Exploiting a centrally powered coherent microcomb for lightweight optical transmission

Domain: physics
Published: 2025-12-29
Editorial outcome: major_revision

Abstract
The exponential growth of data capacity in intelligent terminals drives higher data traffic toward network edges. Compact I/O systems are essential to support space-constrained infrastructures at the computing edges or modular data centers. However, scaling high-capacity transmission via increasing physical channels is constrained by limited source coherence and low carrier-to-noise ratios (OCNR), hindering lightweight, efficient applications like distributed edge computing. Here, we exploit an integrated self-injection-locked dark-pulse microcomb to achieve 1 Tbps/λ/core transmission and characterize the constraints among OCNR, linewidth, and transmission rate. Furthermore, a multi-dimensional transmission architecture for multi-nodes aggregation is explored, boosting the transmission rate to 200 Tbps with 16 comb lines at 70 Gbaud. Combining with integrated waveshapers and semiconductor optical amplifiers, a chip-level parallel carrier generator is explored, reducing system size a hundredfold while delivering 5 Tbps. Our results highlight significant potential for compact and resource-conserving transmission systems in data centers and distributed high performance computing applications.

Introduction
With the explosive growth of artificial intelligence (AI) and the internet of things (IoT) 1, the demand for efficient data transmission within the network has reached unprecedented levels. In addition to backbone network communications, the devices at the network edges, required to perform real-time monitoring 2 and high accuracy sensing 3, are also expected to simultaneously transmit massive information across distributed nodes or back to the data center for system coordination 4. Recent advances in optical cloud computing architectures have demonstrated significant potential for enabling AI workload offloading to edge networks 5, with experimental validation confirming seamless integration between distributed edge nodes and centralized cloud computing infrastructure across metropolitan-area optical networks. To meet these challenges, compact data links with lightweight infrastructures capable of supporting high throughput have become more essential 6.

Integrated photonics can provide high-density data link solutions. Despite the achievement of ultra-high capacity integrated parallel transmission systems, conventional schemes still struggle to deliver the required data throughput while maintaining compact structure and energy efficiency in space-limited and power-constrained scenarios. The challenges stem from two main aspects. Firstly, it is difficult for wavelength-division multiplexing (WDM) parallel light sources to obtain both low noise and compact forms simultaneously. While distributed feedback (DFB) laser diode arrays have been commercially successful 7,8, they exhibit limited phase noise and complexity in synergistic frequency control. Quantum dot mode-locked lasers 9–13 can generate multiple channels with a single laser diode, but the inherent high phase noise reduces the maximum transmission rate for coherent communication. Other integrated multiwavelength sources, such as electro-optical combs 14–16 and Kerr microcombs 17–21, relying on high-power, high-purity optical or microwave sources for low-noise wideband comb generation, which results in bulky and costly setups for edge nodes. Self-injection locked (SIL) Kerr microcombs offer high-coherent multiwavelength sources with a laser diode directly coupled to a high-quality optical nonlinear microcavity. However, the relatively low combline powers of microcombs degrade the OCNR with the optical amplification, limiting the data rates per channel. Optical-injection amplified combs 22,23 have been proposed to avoid the OCNR degeneration, while the employment of laser diode arrays hinders their application for lightweight systems.

Another issue lies in the subsequent system. As the channel count often spans multiple optical bands (S/C/L) for high-capacity integrated optical demonstrations, the link setup of each wavelength, comprising modulators, amplifiers, and passive couplers, grows dramatically in real-world deployments. This increase occurs not only due to the need to scale the same devices within each band 24, but also the differing design structures and operating principles required across bands 25. The use of excessive wavelengths in high-capacity transmission will further exacerbate nonlinear signal crosstalk, which may degrade overall signal quality and limit system throughput, particularly in tightly packed wavelength grids 26,27. Therefore, merely increasing the number of physical channels in the system makes it difficult to realize lightweight, cost-effective high-capacity signal transmission. To date, although achieves over 1 Pbps high-throughput transmission 28, wavelength resources are often underutilized, resulting in reduced communication conversion efficiency and increased device overhead.

Ideally, a compact transmission system at edge nodes needs a parallel light source covering a single band with high coherence and adequate OCNR. Such a source is essential to maximize single-channel capacity, enable multi-dimensional multiplexing for even higher aggregate rates, and tolerate the performance degradation inherent in lightweight systems.

In this work, we achieve high-capacity optical transmission and a streamlined system architecture by employing an integrated SIL comb source. The highly integrated source provides both high coherence with ~40 dB frequency noise suppression and high per-channel power with >60% on-chip conversion efficiency. Among 16 channels within the C-band, each channel exhibits an intrinsic linewidth below 600 Hz with power exceeding −10 dBm. To establish an overarching framework for our study, we perform a detailed investigation of the constraints among OCNR, linewidth, and achievable transmission rate. The experimental results indicate that a narrow linewidth <1 kHz is essential for elevated Gbaud single-channel transmission in our system, positioning the SIL microcomb as a key enabler of high-capacity lightweight systems. We experimentally demonstrated short-reach campus/edge networks and metropolitan area network transmission separately. In the campus/edge networks, we achieve a transmission capacity of 1 Tbps/λ across all carriers using a self-homodyne system. Furthermore, we perform multi-dimensional multiplexing by incorporating with WDM methods across various schemes, such as spatial mode, linear polarization (LP) mode, and orbital angular momentum (OAM), with the highest baud rate in comb-based transmission at 70 Gbaud. Specifically, in the WDM-spatial division multiplexing (SDM) scheme, the maximum transmission capacity exceeds 200 Tbps using only 16 high-quality comb carriers in the C-band. This reduces both wavelength resource requirements and channel count by more than ten times compared to previous demonstrations with the same capacity. Finally, for more compact deployment scenarios, a chip-level multicarrier generator is demonstrated, replacing bulky erbium-doped fiber amplifiers (EDFAs) and wavelength-selective switches (WSS) with integrated semiconductor optical amplifiers and silicon photonic waveshapers. Contributing to the original narrow linewidth and high OCNR, optical carriers provided by the SIL microcomb can tolerate the higher noise figures and insertion losses of integrated devices. The proposed scheme shrinks the system size by a hundredfold with an aggregation rate of 5 Tbps. By fully exploiting the integrated parallel high-coherence optical carriers, the proposed transmission scheme paves the way for high-capacity, ultra-lightweight solutions in next-generation edge computing networks (Fig. 1).

Results
Lightsource effects on transmission system
To fulfill the demand for a compact, highly coherent source, the SIL microcomb scheme is implemented for frequency noise compression and carrier-to-noise enhancement in this work, as shown in Fig. 2b. A laser diode chip, which exhibits a wall-plug efficiency of 13.45%, is directly coupled with the designed silicon nitride (SiN) microresonator chip. The output spectrum from the laser chip through the SiN chip to the fiber link is given in Fig. 2a, with the output wavelength around 1555.37 nm and the output power of 14.86 dBm. Considering the laser diode direct output power of 18 dBm, the total optical insertion loss is estimated as 3.14 dB. The SiN microresonator consists of a rectangular waveguide with a height of 300 nm and a width of 3 μm for both high-quality and normal dispersion conditions. Figure 2c shows one of the measured resonances around 1555.37 nm, where the loaded quality factor is measured as 1.7×10⁷. Such high quality factor is significant for microcomb generation with limited optical power without amplification, and for noise suppression with self-injection locking. In this way, both frequency noise and spontaneous emission noise can be minimized. Figure 2d exhibits the generated coherent microcomb. Thanks to the normal dispersion condition, the spectrum is highly concentrated within C-band with high conversion efficiency. For adequate OCNR, we select the central 16 comblines with power exceeding −10 dBm as parallel optical carriers. The on-chip conversion efficiency from the pump laser to the 15 generated comblines (excluding the residual pump laser) is calculated to be 61.5%, with the center 16 high-power comblines accounting for ~99.7% of the converted energy. In addition, the frequency noise of the generated comblines is lower than the free-running laser, where the noise is suppressed by ~40 dB for the pump laser. Due to the repetition rate fluctuation, the combline coherence degenerates as apart from the pump laser. Owing to the self-injection locking, all 16 comblines express the intrinsic linewidth below 600 Hz.

To quantitatively verify the necessity of such high-performance sources for high-capacity transmission, we conduct a systematic investigation of the impact of linewidth and OCNR on optical communication systems under back-to-back (BTB) conditions. The experimental link transmits DP-16QAM signals as described in the Methods, wherein a Keysight N7714A external cavity laser (ECL) with 10-kHz linewidth serves as the local oscillator (LO). Optical carrier linewidths are varied from 1 Hz to 10 MHz, provided by different commercial lasers and comb lines of the SIL microcomb. The OCNR is adjusted by controlling the laser intensity via a variable optical attenuator. Intuitively, high-speed transmission systems require coordinated optimization of both OCNR and laser linewidth characteristics. While the degradation of OCNR critically impacts transmission, light sources with superior coherence properties, could partially alleviate such degradation. With narrow linewidth (200 Hz for example), an OCNR of ~45 dB suffices to achieve transmission rate exceeding 100 GBaud, where a higher OCNR provides negligible improvement. Importantly, maintaining a linewidth <1 kHz is essential to achieve 1 Tbps in our system, as coherent receivers exhibit heightened sensitivity to phase noise under high-speed signal conditions. As coherence progressively deteriorates, the accumulated phase noise not only elevates the bit error rate (BER) at the receiver but also disrupts frequency offset estimation in the offline digital signal processing. This impairment leads to failed carrier phase recovery and ultimately complete system failure.

Parallel node-to-node data transfer
Currently implemented distributed edge computing systems primarily focus on short-reach campus/edge networks and metropolitan area network transmission, and avoid excessive hardware overhead to maintain edge computing capabilities. Thus, a high single-carrier capacity facilitates efficient data aggregation with minimal scaling requirements. To validate this, parallel wavelength multiplexing data transmission is performed, employing the central 16 comblines. The experimental setup is illustrated in Fig. 3a. SIL comb lines are divided into odd and even banks to simulate real-world communication scenarios. First, we build up a 1 km self-homodyne coherent transmission system to explore the maximum capacity of the comb lines. Limited by the channel spacing of 100 GHz, we artificially doubled the spectral interval through WSS, as shown in Fig. 3b, and distinguish the channels by their transparency. Thanks to the high OCNR with power levels above −10 dBm, all channels can support 110 GBaud DP-32QAM signal transmissions in the WDM configuration, indicating a single-channel rate of 1.1 (net 1.008) Tbps below the 9.1% forward error correction (FEC) threshold with a BER of 7×10⁻³.

Despite self-homodyne coherent system can support ultrahigh transmission rate, it is not suitable for metropolitan area network transmission, considering the requirements of precise fiber-length alignments and extra channels for LO transmission. Thus, the transmission results based on the homodyne coherent scheme are also provided in this section. The symbol rate is limited to 70 Gbaud due to constraints from the power level and linewidth characteristics of the edge comb lines, while simultaneously satisfying requirements for fiber transmission loss and component insertion losses. DP-16QAM signals are then modulated onto the parallel carriers, which are subsequently combined and transmitted through a 160-km standard single mode fiber (SMF). At the receiver end, the LO source and transmitted comb lines are detected and mixed by a coherent receiver. Overall, this 16-channel WDM scheme achieves a raw (net) aggregated rate of 8.96 (8.37) Tbps below the 7% hard decision (HD)-FEC BER threshold.

Extending beyond previous work showing minimal degradation from a soliton microcomb verses a 10kHz narrow-linewidth ECL 18, we demonstrate a substantial improvement in transmission quality by introducing the SIL scheme here. Figure 3d shows the error vector magnitude (EVM) results for each carrier in WDM transmission with DP formats. Compared with a high-performance tunable ECL1 with a ~10kHz linewidth (gray dots), the self-injection locking scheme (purple dots) exhibits a 3dB lower OSNR requirement at the same EVM level due to the high coherence. Figure 3e compares the ECL1 and the 1550.72nm combline (−6 channel) for 160-km transmission. The SIL comb with better noise performance delivers superior BER levels. The OSNR values at a BER of 3.8×10−3 are calculated for the −6, +6, −3, +3, and 0 channels and compared with ECL at the same wavelength, as illustrated in Fig. 3f. This comparison also validates the lower OSNR requirements for the narrower linewidth carriers. It also can be seen that the OSNR penalty difference between the referenced ECL carrier and the narrow-linewidth comb lines increases from 1dB at BTB transmission to 3dB after 160-km. This demonstrates during long-haul transmission, the pulse-like transmission format of the microcomb solution can better resist nonlinear distortions, potentially optimizing signal quality compared to traditional WDM schemes 29, hinting at superior performance compared to commercial ECLs.

Multi-dimensional transmission aggregation
SDM transmission over a field-deployed fiber has been practically demonstrated recently 30. Multiplexing dimensions 31, including spatial, LP mode, and OAM mode, hold promising prospects in next-generation edge networks. Such cascaded multiplexing schemes can aggregate information from distributed nodes operating with the same standardized wavelength configuration. Compared to continuously expanding the wavelength channels, this approach results in a more compact and cost-effective system architecture.

To simulate the aforementioned multi-node aggregation scenario, a 2-km 24-core multi-core fiber (MCF) with a mode field diameter of 9 μm was used. The crosstalk of 24-core MCF is ~28 dB for nearest neighbors, ~49 dB for next-nearest neighbors, and ~62 dB for next-next-nearest neighbors and beyond, as shown in Fig. 4b. In this case, we achieve a raw (net) transmission rate of 215.04 (200.97) Tbps below the 7% HD-FEC BER threshold by loading 70 Gbaud DP-16QAM signals, with only 16 wavelength channels, as shown in Fig. 4c. As far as we are aware, this represents the highest rate realized with an on-chip light source over the entire C-band, significantly simplifying the cumulative device requirements while avoiding saturation of the EDFAs.

Besides, we show the first proof-of-concept mode-division multiplexed (MDM) multi-dimensional transmission includes LP modes in a few-mode fiber (FMF) and OAM modes in a ring-core fiber (RCF) driven by the integrated photonic light source. Two modes are considered here for each scheme, where FMF supports the LP01 and LP02 and RCF supports OAM11 and OAM21, as shown in Fig. 4a. Nonlinear losses and crosstalk across all channels are measured in both schemes, as shown in Fig. 4d. Although higher-order modes exist more crosstalk, the fibers maintain inter-coupling below −15 dB, making them suitable for seamless linking with the front WDM for boosted capacity. Figure 4e shows the WMD-MDM transmission results for LP01 and LP02 mode carrying 40-Gbaud DP-16QAM signals transmitted over a 25-km FMF, with raw (net) capacity of 10.24 (9.57) Tbps. Compared to back-to-back transmission, MDM signals incur an additional OSNR penalty of ~6 dB after transmission over 25-km FMF. OAM modes are multiplexed and demultiplexed by a dedicated functional device 32 operating in C-band, with over 95% generating purity and <3 dB insertion loss. Similarly, the WDM-MDM transmission performance of 16 comb lines carrying 70-Gbaud SP-16QAM signals with raw (net) rate reaching 8.96 (8.37) Tbps in a 50-m RCF using OAM11 and OAM21 modes, as shown in Fig. 4f. It is observed that MDM transmission of OAM modes in this scenario brings about 8-dB OSNR penalty around 7% HD-FEC threshold, compared with BTB transmission. The results validate the feasibility of microcomb-based multi-dimensional cascaded multiplexing schemes using passive specialty fiber links, offering a budget-friendly solution without the need for additional wavelength-dependent active devices.

Highly integrated lightweight transmission
Under stringent cost and footprint constraints, bulky equipment impedes system integration, particularly for achieving lightweight transmission in distributed edge nodes. In this section, beyond integrated light sources, we present a chip-level parallel carrier generator where bulky WSSs and EDFAs are replaced by SOAs and silicon photonic integrated waveshaping chips (IWCs). Figure 5a illustrates the architecture of the chip-level transmitter module, with photographs of all modules provided in Fig. 5b. The IWC is fabricated using mature silicon photonics technology, featuring cascaded microring resonators with a free spectral range (FSR) of ~1.3 THz. Microheaters placed above the microrings allow tuning of resonant frequencies to adjust the output spectrum, as detailed in Supplementary Information Note 5. To suppress thermal crosstalk, adjacent microrings are physically separated by etched trenches, as illustrated in Fig. 5c. Since not all comb lines require power equalization, we achieve uniform power distribution across all spectral lines using only 12 microrings. After the IWC, all 16 comb lines are equalized to −18 dBm per carrier, accounting for an 8 dB insertion loss. All carriers are then amplified by an SOA to a total output power of 18 dBm and routed through another IWC for odd-even channel separation. The separated carriers are modulated by 35-GHz-bandwidth DP-IQ modulators (which introduce 20 dB of insertion loss), combined, and then amplified by an SOA to an output power of 2 dBm before transmission. As demonstrated in Fig. 5e, a 10-km transmission at 5.12 Tbps (net 5.015 Tbps, 5 channels under 7% HD-FEC threshold condition) is achieved using 40-GBaud DP-16QAM signals. The BER trend per channel aligns consistently with the linewidth values as shown in Fig. 5d, with comb lines below 300 Hz linewidth achieving error-free operation.

It is noteworthy that the capacity of the present chip-level transmitter is lower than that of systems based on bulky devices. This primarily stems from carrier performance degradation caused by integrated components, which feature higher noise figures and insertion losses than their benchtop counterparts. Specifically, the IWC contributes an additional 3 dB insertion loss compared to benchtop WSS. SOAs, while far more compact than EDFAs, introduce excessive amplified spontaneous emission (ASE) noise. Meanwhile, their high α-factor and nonlinear effects (notably XPM) further induce cumulative phase noise and waveform distortion in high-speed systems 33,34. Figure 5f presents the corresponding noise degradation after an SOA amplification. When amplified to 10 dBm, the linewidth of channel 6 increases by approximately threefold and tenfold via EDFA and SOA respectively. After two SOAs, IWC and modulators, the OCNR decreases by 13 dB at the 2 dBm output operating point, as shown in Fig. 5g. We find that when the input optical carrier has an OCNR < 25 dB, the ASE noise from the dual SOAs completely overwhelms the carrier, rendering it incapable of supporting signal transmission. Despite these impairments, the SIL light source still enables >5 Tbps transmission within the chip-level lightweight system, due to its original superior coherence and OCNR. For comparison, we implement a reference system using a 45-GHz-spacing electro-optic frequency comb pumped by an N7714A ECL (Fig. 5d). Under identical conditions, severely degraded constellation diagrams are obtained due to its poor original coherence (Fig. 5e black pentagrams).

Methods
Detailed characterization of microcomb
The silicon nitride resonator was fabricated with a standard integrated photonic foundry process. A 300 nm silicon nitride layer (refractive index 1.95 @ 1550nm) is encapsulated by highly transparent silica cladding, with the bottom oxide layer thickness of 4.4 μm and the top oxide layer of 3.5 μm. The silicon substrate is 725 μm thick. To achieve low loss and adequate dispersion, the microresonator waveguide width was designed to be 3 μm, with the bus waveguide of 1 μm. The fabricated microresonator exhibits a free spectral range of 100 GHz (aligned with the DWDM ITU grid spacing standard), a Q-factor of ~1.7×10⁷, and a coupling loss of ≤2.5 dB/facet @ 1550nm. The microring resonator adopts a racetrack configuration, with Euler bends on both curved sections. The coupling gap is 1 μm, and the coupling length is 110 μm, forming an overall weakly overcoupled structure.

Our DFB laser outputs ~18 dBm, which is reduced to 14.86 dBm after traversing the microresonator. The DFB laser was mounted on a six-axis translation stage (Thorlabs MAX602D/M) and controlled by a benchtop laser diode driver (Thorlabs ITC4001). The SiN microresonator, maintained at room temperature, was placed on a three-axis translation stage (Thorlabs MAX313D). Alignment between the DFB laser and the SiN microresonator is achieved using a piezoelectric controller to adjust the six-axis stage. The output was collected by lensed fibers, with 1% of the light directed to an optical spectrum analyzer (Yokogawa AQ6370C) and the remaining 99% connected to subsequent communication systems or noise measurement setups. When the DFB laser diode was powered on, the current was set around 300 mA, and the temperature was maintained at ~30 °C. By fine-tuning the position of the six-axis stage, the generation of dark pulse soliton frequency combs can be observed on the optical spectrum analyzer (as shown in Fig. 2d). Stable microcomb generation is sustained for over 1000 min.

We employed delayed self-heterodyne interferometry to measure the spectral phase noise. The desired wavelength was filtered out using an optical filter. The signal was then split into two paths with equal power: one path was frequency-shifted by a 200 MHz acousto-optic modulator (AOM), while the other passed through a 10-km (10 m for MHz Laser) fiber delay line. Both paths were subsequently combined using a 2×2 50/50 optical coupler (OC) and directed to two photodetectors (PD). The output signals were captured by an oscilloscope at a sampling rate of 500 MSa/s, collecting 80 million data points, which were then processed using custom software.

Fabrication and characterization of the SDM (de)multiplexers
The optical fibers used in the experiments (a 160-km SMF, a 2-km 24-core MCF, a 25-km FMF and a 50-m RCF) are all provided by YOFC. We fabricate all the (de)multiplexers needed for SDM experiments. The 24-core MCF (de)multiplexer are self-made fan-in/fan-out 3D photonic devices based on femtosecond laser writing technology. The glass chip (dimension: 40 mm × 20 mm × 1 mm) is inscribed by a high repetition rate Ytterbium-based laser to form 24-channel (de)multiplexer. The measured insertion losses of (de)multiplexer are all lower than 1.5 dB in C band, with the maximum and minimum inter-channel crosstalk of −19.8 dB and −30.6 dB respectively. For LP modes (de)multiplexing, we employed all-fiber mode-selective couplers (MSCs) based on the side-polishing technique 47. The MSC consists of a SMF and a FMF. When the effective refractive index of the fundamental mode in the SMF matches that of the higher-order modes in the FMF, the fundamental mode is coupled into the FMF to generate the corresponding LP02 mode. The fundamental mode in the FMF maintains its mode nature as it passes through the MSC. As a result, the MSC successfully enables the multiplexing of the LP01 and LP02 modes. The LP multiplexer and demultiplexer are connected by an FMF to characterize their desirable performance. Across the entire C-band, they exhibit a loss of less than 1.5 dB and crosstalk of less than −15 dB. For OAM modes (de)multiplexing, we utilized MSCs similar to those used for LP mode (de)multiplexing 32. The difference lies in the use of the fused biconical taper technique for OAM modes (de)multiplexing. Additionally, a multimode fiber (MMF) is used instead of an FMF. Furthermore, we implemented two cascaded MSCs to achieve the multiplexing of OAM11 and OAM21 mode. The cascaded OAM multiplexer demonstrates a loss of less than 2.5 dB and crosstalk of less than −15 dB across the entire C-band.

Detailed coherent experimental setup
The experimental results presented in Fig. 2e were obtained using multiple light sources with varying linewidth characteristics: NKT Photonics (1 Hz), Comb 0 (25 Hz), Comb 1 (81.64 Hz), Comb 5 (220 Hz), SANTEC TSL-510 (1.576 kHz), RIO ORION-1550-30-15-M (5 kHz), KEYSIGHT N7714A ECL (10.4 kHz), ALNAIR TLT-200 (20 kHz), APEX AP3350A (238 kHz), and CONQUER CUSTOMIZED (628 kHz), along with two cases that failed demodulation-an InP DFB laser (3 MHz) and BOXOPTRONICS CUSTOMIZED (8.8 MHz). Throughout the transmission experiments, the KEYSIGHT N7714A ECL served as the LO to maintain phase reference stability. It must be emphasized that all OCNR measurements were performed with the optical spectrum analyzer’s resolution bandwidth set to 6.25 GHz.

In our work, we employed self-homodyne and homodyne coherent detection schemes for optical communication demonstration. The homodyne scheme modifies the self-homodyne setup by replacing LO path with an additional light source, while other configurations remain unchanged. Notably, for a WDM system with a single-wavelength rate of 1 Tbps, self-homodyne detection system demands precise alignment of the signal and LO path lengths, exhibiting a trend where lower linewidths of light source result in higher tolerance levels. At the transmitter, integrated comb chip generates 16 comb lines as the WDM channels while 16 ECLs are used to load channels for comparison experiment. The channel spacing of both solutions is 100 GHz. The WSS (Finisar Waveshaper 4000s) (with 5 dB insertion loss) splits these channels into odd/even paths. Subsequently, the light source carrying 16 wavelengths is amplified by an amplifier to boost the power of each channel, with the aggregate power reaching ~13 dBm prior to entering two 35-GHz 3 dB bandwidth IQ modulators (Sumicem T.SBXH1.5PL-35PD-ADC). Both paths are simultaneously modulated by data generated from a 128-GSa/s Arbitrary Waveform Generator (AWG-M9505A). Depending on the data rate, the output optical signal power varies within the range of −7 dBm to −14 dBm. The odd and even signals decorrelating by a 10-ns optical delay lines are coupled with similar power levels and fed into the transmission link. When transitioning to single-polarization transmission, only one polarization of the dual-polarization modulator is utilized, with the corresponding modulator drive voltage applied to that polarization. The modulator’s bias voltage is dynamically adjusted by an automatic bias controller to ensure stable high-speed signal performance and efficient operation.

The transmission link consists of an EDFA (KEOPSYS) for signal amplification, multiplexers/demultiplexers, and multidimensional multiplexing fiber to validate the optical comb’s transmission performance. The SDM channels are fully decorrelated to each other, with 10-ns optical delay lines between each channel. The power injected into the fiber is kept below 10 dBm to mitigate fiber nonlinear effects. At the receiver, amplification, filtering, attenuation and amplification scheme is employed for WDM demultiplexing and OSNR adjustment. The LO light, amplified to 18 dBm by an EDFA, is coherently detected with the signal light (around 0 dBm) by a dual-polarization coherent receiver consisting of a polarization-diversity 90-degree hybrid and four 70-GHz 3 dB bandwidth balanced photodiodes. A 256-GSa/s real-time oscilloscope (KEYSIGHT UXR0594AP) with 59-GHz bandwidth captures waveforms from four channels and sends them to a computer for DSP. In the context of DSP, at the transmitter side, we initially generate a PRBS sequence for QAM mapping, followed by 0.01 Root Raised Cosine pulse shaping, and then resample the signal before sending it to the AWG. On the receiver side, the captured signal undergoes sequential processing including resampling, frame synchronization, dispersion compensation, carrier frequency offset estimation using the fourth-power algorithm, adaptive MIMO equalization, carrier phase recovery through a two-stage blind phase search algorithm (with filter lengths of 32 and 8 for the first and second stages, respectively), demodulation, and BER calculation. It is noteworthy that during the verification of the relationship between OCNR and linewidth versus maximum net rate, DSP section utilized an 81-tap adaptive MIMO equalizer. In other experimental scenarios, the use of a 41-tap MIMO equalizer with reduced compensation capability and the decreased received OSNR per comb line caused by WDM collectively lead to a degradation in achievable symbol rate compared to the former configuration.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "This paper presents the use of a self injection locked microcomb as a source for coherent optical fiber transmission in the C-band achieving a net rate of 8.4 Tbps in WDM scheme and a net 200 Tbps in a WDM + MCF configuration. Additionally, MDM transmissions are also demonstrated achieving net 9.57 and 8.37 Tbps. The authors claim a 10-fold reduction in resource requirements for similar capacity architectures. The paper is well organized but could improve in the following areas.\n\nPlease specify in more details the exact DSP that was used at both the transmitter and at the receiver. It would be interesting to know filter lengths, equalization and pre-emphasise used, etc.\n\nThe authors claim the first coherent single-lambda comb-based transmission results over 1 Tbps, however their citation [8] (Bernal S, et al.) includes a single-lambda demonstration of 1.6 Tbps in the O-band. Please adapt the claim accordingly.\n\nThe authors compare the performance of the comb lines vs commercial ECLs for different OSNR values. It would be valuable to add a discussion on the amount of gain needed in their proposed architecture since it requires more optical amplification than a single laser WDM scheme.\n\nThe authors claim their design is lightweight as it only uses one optical source, however their WDM transmission still requires 16 DP-IQMs, EDFAs, mux/demux, etc. to be integrated into the same chiplet. I recommend the authors carefully justify the full size of their proposed architecture. It would also be interesting to see a discussion on their proposed architecture being used in a bi-directional link.\n\nThe discussion section provides a good summary of the obtained results as compared to previous works but does not provide an impactful argument explaining why this type of comb source is ideal for their proposed architecture. A more detailed comparison between the limitations of this type of comb source compared to others would be of great interest. Additionally, system sensitivities to temperature would be of value to the study.\n\nOther comments:\nPlease specify for all the throughput values if they are net (after FEC) or not.\n\nIn the Noise compression for ultra-high carrier capacity section, two laser output powers are mentioned. Please clarify which is the output of the laser diode and which is the output of the optical comb.\n\nPlease fix minor spelling errors such as “combine” instead of \"comb line”.\n\nFigure 2(g) shows two curves labeled 1 Tbps results each. It might be better to remove that label as every point on those curves does not equal a net 1 Tbps throughput.\n\nIn Parallel node-to-node data transfer, ECL1 and comb are both described as (gray dots) for Figure 3(b)", "reviewer_2": "In this manuscript, “Exploiting a Centrally Powered Coherent Microcomb for Lightweight Optical Transmission” , the authors use the comb lines of a microcomb to demonstrate:\n- 1 Tbps (115 GBd 32 QAM-DP) with one of the lines;\n- 8.4 Tbit/s with 16 lines (70 GBd 16QAM-DP) over 160 km of SSMF;\n- 200 Tbps with 16 lines (40 GBd 16QAM-DP) over 2 km of a 24-core fiber;\n- 9.5 Tbps with 16 lines (40 GBd 16QAM-DP) over 25 km of a 2-mode (LP) fiber;\n- 8.4 Tbps with 16 lines (70 GBd 16QAM-SP) over 50 m of a 2-mode (OAM) fiber.\nThe authors make use of such high symbol rates thanks to the low noise properties of each comb line, which is achieved by self-injection locking of the DFB pump laser. While the high on-chip conversion efficiency of 60% is associated with the type of comb.\nThe manuscript is clearly written, and the topic and results are relevant for the scientific community. My major concern relates to the novelty impact of this work. First, regarding the comb the authors employ, this seems to be the same as the one reported in Ref. 22, where the noise reduction is already analysed (as well as in other references) and the comb is already used for data transmission: 30 GBd, 32QAM-DP. The authors, thus need to clarify if this is the same comb and what is the main novelty with respect to that work. Otherwise, the work feels that it is an incremental enabled by using better components such as modulators and AWGs.\n\nSecond, when it comes to the 1 Tbps claim, this is shown only for one of the comb lines, i.e., the pump line. The authors should also characterize other lines in the same way (Fig. 2g). Will there be a penalty due to the lower power / higher noise? With only one line, their 1 Tbps is not that novel, see ,e.g., [Buchali, 1-Terabit/s Net Data-Rate Transceiver Based on Single-Carrier Nyquist-Shaped 124 Gbaud PDM-32QAM], or [First Single-Carrier Transmission at Net Data Rates of 1.6 Tb/s over 9075 km and 2.4 Tb/s over 1210 km Using 300 GBd Dual-Polarization Signals and Probabilistic Constellation Shaping].\nIf the selling point is to also demonstrate the high data rate with MCF, FMF, RCF, there has been already works bringing this approach tothe extrem: [22.9 Pb/s data-rate by extreme space-wavelength multiplexing] with a few-modes MCF providing 114 spatial channels (30 Tbps/wavelength).\n\nFinally, the authors claim 200 tbps to be the highes with an integrated source, but already Ref.21 in 2018 showed 600 tbps, and maybe I am missing other examples.\n\nIn summary, the authors would need to position their work a bit more fairly and more clearly with respect to the state of the art in a meaningful way before the manuscript can be accepted.\n\nOther comments:\n- The manuscript, including methods and supplementary material, does not provide detailed description of: microresonator used (although I assume is the one from Ref 22), the soliton state, all equipment used, DSP, etc. The lack of details prevents properly evaluating the veracity of their results and questions its reproducibility.\n- The authors highlight the power conversion efficiency, but what about the wall-plug efficiency? How does it compare to other similar approaches?\n- The authors performed several transmission demonstrators with different symbol rates, modulation formats, with SMF, MCF, FMF, RCF. They could consider having a simple way to indicate them, e.g, table or in the respective figures.\n\nSome typos:\n-line 140: “combines”\n- line 247 : “include”\n- Line 293 “perabit”\n- Line 252\nFig. 5 : this should be just for comb-based transmission experiments.", "reviewer_3": "This manuscript reports technically work demonstrating high-speed multidimensional optical communication utilizing a self-injection-locked (SIL) dark-pulse microcomb. The authors ascribe the achieved high baud rate and 1 Tbps per-channel performance to the noise suppression facilitated by injection locking. However, in comparison with existing literature, this study does not introduce a fundamentally novel device architecture or a system-level innovation of transformative significance. Rather, the primary contribution appears to be the enhancement of single-carrier transmission rates, achieved at the cost of a reduced number of utilized channels, without providing substantial forward-looking perspectives. Consequently, I believe the scope and impact of this work might be more appropriately aligned with the focus of specialized journals in photonics or communications. The reasons I'm not entirely convinced by this work are listed below.\n\n1. The authors attribute the high baud rate and 1 Tbps/channel performance to noise suppression via injection locking, but this claim lacks quantitative support.\n(a) Please provide comparative data (OCNR, linewidth/phase noise, combline power) between the SIL and non-SIL combs. How do these differences translate to single-wavelength capacity?\n(b) The explanation for setting the baud rate based on OCNR (lines 186-187) is unclear. What is the precise relationship between OCNR and maximum baud rate per channel? Why does the SIL comb achieve higher baud rates than other sources? Supporting analysis is required.\n(c) The 1 Tbps record relies on a single high-power comb line. This does not represent the system's parallel performance and weakens the claim of a system-level breakthrough based on the microcomb.\n\n2. The authors frequently emphasize the \"lightweight\" nature of the system, attributed to the compactness and conversion efficiency of the SIL comb.\n(a) However, reliance on external EDFA amplification and WSSs for spectral shaping/equalization (Supplementary Note 4) contradicts the compactness claim. The authors should propose mitigation strategies or quantify the hardware overhead.\n(b) Furthermore, the use of EDFAs and WSSs may negate the noise benefits of SIL combs. How does ASE noise impact OCNR, linewidth, and BER? Is the performance comparable or inferior to simpler pump-plus-filter approaches? This trade-off needs clarification.\n(c) While a 61.5% conversion efficiency for 15 lines is reported, power distribution is uneven. Spectral flattening for power equalization introduces additional insertion loss. The authors should recalculate an \"effective\" conversion efficiency considering usable lines post-equalization.\n\n3.The manuscript mentions injection-locked amplification as a future improvement but this contradicts earlier claims that such techniques are less suitable for lightweight systems. Furthermore, prior work (e.g., Ref. [22]) has already demonstrated injection-locked amplification of SIL microcombs with comparable or better performance. The authors should re-evaluate their novelty claim and clarify the meaningful differences of their implementation compared to these prior studies.\n\n4. Minor issues and editorial errors:\n(a) Line 202: \"gray dots\" should be \"purple dots\".\n(b) Supplementary Note 4, line 65: \"Fig.1(e)\" reference is unclear."}, "author_response": "Manuscript ID: NCOMMS-25-24030\nTitle: Exploiting a Centrally Powered Coherent Microcomb for Lightweight Optical Transmission\nAuthor: Junhao Han, Guofeng Yan, Kang Li, Bitao Shen, Haowen Shu, Yimeng Wang, Yuchen Zhang,\nJiong Xiao, Yichen Wu, Huajin Chang, Chengkun Cai, Xuguang Zhang, Xingjun Wang, and Jian Wang\nDear Editor and Reviewers of Nature Communications,\nWe sincerely appreciate the careful review by the reviewers and have modified the manuscript in\naccordance with their suggestions. Here, we present a point-by-point reply (in blue) to the reviewers'\ncomments (in black). All the changes have been highlighted (in red) with corresponding original text\nprovided for comparison(in orange).\nResponse to the report from the Referee #1\nGeneral comments: \"This paper presents the use of a self injection locked microcomb as a source for coherent optical fiber\ntransmission in the C-band achieving a net rate of 8.4 Tbps in WDM scheme and a net 200 Tbps in a WDM + MCF\nconfiguration. Additionally, MDM transmissions are also demonstrated achieving net 9.57 and 8.37 Tbps. The authors claim\na 10-fold reduction in resource requirements for similar capacity architectures. The paper is well organized but could\nimprove in the following areas.\"\nOur reply: We are sincerely grateful for the reviewer’s favorable comments on our study. In the revised manuscript, we\nhave included design and experimental details and carefully proofread the manuscript. Please find our point-by-point\nresponse attached.\nComment 1: \"Please specify in more details the exact DSP that was used at both the transmitter and at the receiver. It would\nbe interesting to know filter lengths, equalization and pre-emphasise used, etc.\"\nOur reply: Thanks for your valuable comment regarding the insufficient description of our experiments. In response, we\nhave provided a detailed explanation of the DSP aspects:\n(Materials and Methods, page 28) In the context of DSP, at the transmitter side, we initially generate a PRBS sequence for\nQAM mapping, followed by 0.01 Root Raised Cosine pulse shaping, and then resample the signal before sending it to the\nAWG. On the receiver side, the captured signal undergoes sequential processing including resampling, frame\nsynchronization, dispersion compensation, carrier frequency offset estimation using the fourth-power algorithm, adaptive\nMIMO equalization, carrier phase recovery through a two-stage blind phase search algorithm (with filter lengths of 32 and\n8 for the first and second stages, respectively), demodulation, and BER calculation. It is noteworthy that during the\nverification of the relationship between OCNR and linewidth versus maximum net rate, DSP section utilized an 81-tap\nadaptive MIMO equalizer. In other experimental scenarios, the use of a 41-tap MIMO equalizer with reduced compensation\ncapability and the decreased received OSNR per combline caused by WDM collectively lead to a degradation in achievable\nsymbol rate compared to the former configuration.\nComment 2: \"The authors claim the first coherent single-lambda comb-based transmission results over 1 Tbps, however\ntheir citation [8] (Bernal S, et al.) includes a single-lambda demonstration of 1.6 Tbps in the O-band. Please adapt the claim\naccordingly.\"\nOur reply: Thanks for the correction. Indeed, our work does not constitute the first demonstration of an integrated light\nsource achieving single-carrier 1 Tbps transmission, as we had overlooked prior works in O-band communications. Instead\nof claiming single-carrier channel rates, in the revised version, we further demonstrate exceeding 1 Tbps (110 Gbaud DP-\ndue to their inherent limitations in linewidth and OCNR. We have updated the newly added experiment in Fig. 3(b) and (c)\nas follows:\nFig. 3 SMF transmission system. (a) Schematic diagram of the high-speed node-to-node transmission system for short-reach\ncampus/edge networks and metropolitan-scale optical transmission. (b) The self-homodyne-based campus/edge\ninterconnect system achieves per-channel transmission rates exceeding 1 Tbps across all wavelength channels. (c)\nConstellation diagram of DP-32QAM.\n(Introduction, page 6) We simulated short-range campus/edge networks and metropolitan area network transmission\nseparately. In the campus/edge networks, we achieved a transmission capacity of 1 Tbps/λ across all carriers using a self-\nhomodyne system.\nComment 3: \"The authors compare the performance of the comb lines vs commercial ECLs for different OSNR values. It\nwould be valuable to add a discussion on the amount of gain needed in their proposed architecture since it requires more\noptical amplification than a single laser WDM scheme. \"\nOur reply: We appreciate these valuable suggestions. A comparative analysis has been added in the revised Supplementary\nInformation, as shown in the following figure. In summary, the output power of the integrated frequency comb is lower\nthan that of conventional laser-array-based WDM schemes (assuming 0 dBm output), requiring an additional 13 dB of gain.\nWhile the additional noise influence brought by amplification can be effectively alleviated by the narrow linewidth\ncharacteristic.\nFig. S2 Gain Comparison: SIL Comb vs. Commercial External-Cavity Laser.\n(Supplementary Note 3) Here we present a comparative analysis of the gain requirement between the SIL microcomb and\nthe laser-array schemes. To ensure a fair comparison, the input power to the modulator is fixed at 10 dBm (its optimal\noperating point) across all configurations. With higher output power, the system with laser arrays eliminates the need for\nthe first-stage EDFA (shown in Fig. S2 bottom panel). And the WSS before IQ modulators for demultiplex is not needed. For\nthe microcomb-based approach, due to the 5 dB insertion loss introduced by the WSS, this scheme requires an additional\n13 dB of first-stage gain compensation, with additional OCNR degradation. However, due to the narrow-linewidth\ncharacteristics of the self-injection-locked microcomb, the receiver achieves the same level of BER, despite remaining a 3\ndB lower OSNR when compared with the bulky laser approach (main text in Fig 3(d)).\n(Discussion, page 20) Owing to the high conversion efficiency and coherence of each combline, the highest single channel\nnet data rate of 1 Tbps/(λ·core) and 523 Gbps/(λ·core) are achieved in wavelength multiplexing and wavelength-space\nmultiplexing schemes, respectively. It means that the single-carrier rate of comb-based transmission has reached the\nlevel of high-power bulk lasers48. Although the output power of the integrated frequency comb remains lower than that of\ntraditional bulk laser arrays, this limitation is compensated during transmission by the comb's high conversion efficiency\nand narrow linewidth characteristics.\nComment 4: \"The authors claim their design is lightweight as it only uses one optical source, however their WDM\ntransmission still requires 16 DP-IQMs, EDFAs, mux/demux, etc. to be integrated into the same chiplet. I recommend the\nauthors carefully justify the full size of their proposed architecture. It would also be interesting to see a discussion on their\nproposed architecture being used in a bi-directional link.\"\nOur reply: Thanks for the insightful question. In our previous demonstrations, the transmitter primarily consists of a SIL\ncomb, two EDFAs, one WSS, and two DP-IQMs. Based on calculations, the total footprint measures 2300 cm² with a height\nof 12 cm in the system, with sizes of each individual components are listed below:\nComponent Number Volume (cm*cm*cm)\nSIL Comb 1 2.8*1.2*1\nEDFA 2 32*25*10\nWSS 1 31*24*12\nDP-IQM 2 8.8*1.4*1\nFrom the above table, the bulky EDFA and WSS occupy the majority of the volume, making the transmitter appear less\n\"lightweight\". To address this, we have replaced the transmitter module with a more integrated solution, combining SOA\nand silicon photonic waveshaping chips, which maintains >5 Tbps transmission capability while reducing the system\nvolume by 80 times, occupying less than 100 cm² with a height of 3 cm (Fig. 5(b)). Although monolithic integration of all\n16 channels remains challenging, the proposed all-modular system demonstrates that on-chip architectures can sustain\nequally high channel rates. This approach simultaneously achieves system miniaturization while meeting inter-node\ntransmission requirements.\nComponent Number Volume (cm*cm*cm)\nSIL Comb 1 2.8*1.2*1\nSOA 2 3*1.27*1\nIWC 2 5.2*4.8*3\nDP-IQM 2 8.8*1.4*1\nFig. 5 Highly integrated transmitter demonstration. (b) Physical Diagram of the Transmitter Module.\nAlso, we completely agree with the reviewer's interesting suggestion about bidirectional link transmission. The integrated\ncoherent receiver can be implemented, as demonstrated in our previous work [Laser & Photonics Reviews, 18(1): 2300501,\n(2024)], with further plans to realize a fully lightweight transceiver link.\n(Discussion, page 22) Extending this approach to the receiver side is equally feasible, where the proposed chip-level parallel\noptical source can serve as local oscillators in combination with integrated photodetectors and demultiplexers49. The co-\nintegration of transmitters and receivers would enable a lightweight platform for bidirectional transmission.\nComment 5: \"The discussion section provides a good summary of the obtained results as compared to previous works but\ndoes not provide an impactful argument explaining why this type of comb source is ideal for their proposed architecture. A\nmore detailed comparison between the limitations of this type of comb source compared to others would be of great\ninterest.\"\nOur reply: Thanks for the valuable insights. Our SIL source indeed offers distinct advantages in terms of the simultaneously\nachieved high coherence and OCNR, which ensures parallel high-capacity data transmission in a shrunk form factor\ncompared with the traditional bulky laser array and other externally pumped comb approach.\nIn the revised manuscript, we systematically analyze the influence of OCNR and linewidth on the maximum transmission\nrate under back-to-back (BTB) conditions, as shown in Fig. 2(e) of the revised manuscript. As seen from the figure, the\nhigher OCNR and narrower linewidth will result in a higher maximum transmission rate. This is exactly what SIL dark-\npulse microcomb can provide, as we demonstrate in this manuscript. With SIL operation, such parallel sources feature\nremarkable narrow linewidth, along with simple operation and fully integrated. In the normal dispersion microresonator,\nthe mode-locked dark-pulse state is well-known for the high conversion efficiency, experimentally >60% in this manuscript.\nSuch high conversion efficiency ensures a high single channel power, equivalently a high OCNR. Such unique combination\nenables tolerance to higher insertion losses and SNR degradation, especially when employing lossy on-chip WDM devices\nand noisy SOAs in a space-constrained scenario.\nCompared with other comb sources, semiconductor mode-locked laser chips face inherent phase noise limitations, leading\nto wide linewidth of ~1 MHz and blocking high-coherence transmission. Limited by the long cavity length, bulky mode-\nlocked lasers tend to feature combline spacing < 1 GHz, which require precise filtering to select target comblines for suitable\nchannel spacing. Conventional microcombs demand the delicate frequency alignment between the pump laser and the\nmicroresonator. In addition, the coherence is determined by the pump laser, where chip-level lasers are insufficient to\nprovide the pump with both high power and high coherence. Electro-optic combs, while alternative solutions, require\nadditional microwave drivers with high cost and increased complexity, and the coherence also relies on the external sources.\nFig. 2 Integrated coherent comb source generation and the effect of light source on transmission. (e) The influence of\nOCNR and linewidth on the maximum net symbol rate is evaluated under the error-free condition. The red pentagrams in\nthe figure trace the degradation path of the light source in the communication system.\nTo further exhibit the superiority of SIL microcomb for lightweight systems, we constructed a transmission system using\nelectro-optic comb (Fig 5. (d)). Except for the larger footprint and higher cost, the transmission performance (balck star) is\nalso worse than that based on the SIL microcomb source, when processed through the same SOA and integrated\nwaveshaping chip (IWC).\nFig. 5 Highly integrated transmitter demonstration. (d) Intrinsic linewidth characteristics of individual combline. The black\npentagrams in the figure denote the combline generated by the microwave-driven electro-optic frequency comb. (e)\nTransmission with a symbol rate of 40 Gbaud and DP-16QAM modulation format. Partial constellation diagrams and\ncorresponding EVM values are provided. Eleven channels are considered to achieve error-free transmission.\n(Results, page 18) For comparation, we implement a reference system using a 45-GHz-spacing electro-optic frequency comb\npumped by an N7714A ECL (Fig. 5(d)). Under identical conditions, severely degraded constellation diagrams are obtained\ndue to its poor original coherence (Fig. 5(e) black pentagrams).\n(Discussion, page 20) Owing to the high conversion efficiency and coherence of each combline, the highest single channel\nnet data rate of 1 Tbps/(λ·core) , 523 Gbps/(λ·core) and are achieved in wavelength-mode multiplexing and wavelength-\nspace multiplexing schemes, respectively. It means that the single-carrier rate of comb-based transmission has reached the\nlevel of high-power bulk lasers48. Although the output power of the integrated frequency comb remains lower than that of\ntraditional bulk laser arrays, this limitation is compensated during transmission by the comb's high conversion efficiency\nand narrow linewidth characteristics. Compared to other integrated light sources, our approach demonstrates superior\ncoherence and noise performance while achieving the highest level of integration - requiring neither bulk laser drivers nor\nmicrowave excitation.\nComment 6: \"Additionally, system sensitivities to temperature would be of value to the study.\"\nOur reply: Thanks for the valuable suggestion. Aside from the IWC and modulator components, our system incorporates\nTEC controllers for all critical elements, so it can somehow resist the environmental temperature variations. We have\nperformed additional temperature stability tests, and the detailed experimental results have been included in the revised\nSupplementary Information. The microcomb device, in summary, operates stably between 22 and 28 °C. To function in\nwider ambient conditions, thermal-isolating packaging will be required to suppress temperature fluctuations.\n(Supplementary Note 5) In integrated WDM transmission systems, light sources exhibit the most significant susceptibility\nto temperature fluctuations. By adjusting the TEC temperature of the silicon nitride microring, we simulated real-world\nenvironmental temperature variations. The system maintains normal operation within a 22-28°C range (6°C operational\nwindow). The corresponding wavelength drift ranges from 1555.34 nm to 1555.42 nm, which does not affect the final\nfrequency offset estimation. This is because: (1) the local oscillator (LO) can be dynamically adjusted with temperature\nvariations, and (2) such drift does not compromise the intrinsic coherence at each specific temperature. In practical\ntransmission scenarios, each component can be thermally stabilized by individual TEC controllers, enabling reliable\nperformance across wider ambient temperature fluctuations.\nFig. S4 The optical spectrum varies with ambient temperature from 21.5°C to 28.5°C, where cross markers in the figure\nindicate failure conditions.\nComment 7: \"Please specify for all the throughput values if they are net (after FEC) or not.\nIn the Noise compression for ultra-high carrier capacity section, two laser output powers are mentioned. Please clarify which\nis the output of the laser diode and which is the output of the optical comb.\nPlease fix minor spelling errors such as “combine” instead of \"comb line\".\nFigure 2(g) shows two curves labeled 1 Tbps results each. It might be better to remove that label as every point on those\ncurves does not equal a net 1 Tbps throughput.\nIn Parallel node-to-node data transfer, ECL1 and comb are both described as (gray dots) for Figure 3(b).\"\nOur reply: We have meticulously examined all technical details and implemented corresponding revisions. We sincerely\nappreciate the reviewers' rigorous scientific approach.\n(Results, page 13) Thanks to the high OCNR with power levels above -10 dBm, all channels can support 110 GBaud DP-\n32QAM signal transmissions in the WDM configuration, indicating single-channel rate of 1.1 (net 1.008) Tbps.\n(Results, page 14) Overall, this 16-channel WDM scheme achieves a raw (net) aggregated rate of 8.96 (8.37) Tbps.\n(Results, page 17) In this case, we achieve a raw (net) transmission rate of 215.04 (200.97) Tbps by loading 70 Gbaud DP-\n16QAM signals, with only 16 wavelength channels, as shown in Fig. 4(c).\n(Results, page 18) Figure 4(e) shows the WMD-MDM transmission results for LP01 and LP02 mode carrying 40-Gbaud DP-\n16QAM signals transmitted over a 25-km FMF, with raw (net) capacity of 10.24 (9.57) Tbps.\n(Results, page 18) Similarly, the WDM-MDM transmission performance of 16 comblines carrying 70-Gbaud SP-16QAM\nsignals with raw (net) rate reaching 8.96 (8.37) Tbps in a 50-m RCF using OAM11 and OAM21 modes, as shown in Fig. 4(f).\n(Results, page 9) The output spectrum from the laser chip through the SiN chip to the fiber link is given in Fig. 2(a), with\nthe output wavelength around 1555.37 nm and the output power of 14.86 dBm. Considering the laser diode direct output\npower of 18 dBm, the total optical insertion loss is estimated as 3.14 dB.\n(Results, page 10) The on-chip conversion efficiency from the pump laser to the 15 generated comblines (excluding the\nresidual pump laser) is calculated to be 61.5%, with the center 16 high-power comb lines comblines accounting for\napproximately 99.7% of the converted energy.\n(Results, page 14) Figure 3(e) compares the high-performance ECL1 and the 1550.72 nm comb line combline (-6 channel)\nfor 160-km transmission.\n(Results, page 14) Compared with a high-performance tunable ECL1 with a ~10 kHz linewidth (gray dots), the self-injection\nlocking scheme (gray dots purple dots) exhibits a 3 dB lower OSNR requirement at the same EVM level due to the parallel\nhigh coherence.\nResponse to the report from the Referee #2\nGeneral comments: \"In this manuscript, “Exploiting a Centrally Powered Coherent Microcomb for Lightweight Optical\nTransmission” , the authors use the comb lines of a microcomb to demonstrate:\n- 1 Tbps (115 GBd 32 QAM-DP) with one of the lines;\n- 8.4 Tbit/s with 16 lines (70 GBd 16QAM-DP) over 160 km of SSMF;\n- 200 Tbps with 16 lines (40 GBd 16QAM-DP) over 2 km of a 24-core fiber;\n- 9.5 Tbps with 16 lines (40 GBd 16QAM-DP) over 25 km of a 2-mode (LP) fiber;\n- 8.4 Tbps with 16 lines (70 GBd 16QAM-SP) over 50 m of a 2-mode (OAM) fiber.\nThe authors make use of such high symbol rates thanks to the low noise properties of each comb line, which is achieved by\nself-injection locking of the DFB pump laser. While the high on-chip conversion efficiency of 60% is associated with the type\nof comb.\nThe manuscript is clearly written, and the topic and results are relevant for the scientific community.\"\nOur reply: We are deeply grateful for the thoughtful evaluation of our work and sincerely appreciate the considerable time\nand effort you have dedicated to reviewing our manuscript. All responses to the reviewers' comments and corresponding\nmanuscript revisions have been clearly documented. Please find our point-by-point response attached.\nComment 1: \"My major concern relates to the novelty impact of this work. First, regarding the comb the authors employ,\nthis seems to be the same as the one reported in Ref. 22, where the noise reduction is already analysed (as well as in other\nreferences) and the comb is already used for data transmission: 30 GBd, 32QAM-DP. The authors, thus need to clarify if this\nis the same comb and what is the main novelty with respect to that work. Otherwise, the work feels that it is an incremental\nenabled by using better components such as modulators and AWGs.\"\nOur reply: We sincerely appreciate the reviewer's valuable feedback and would like to clarify the key distinctions between\nour work and Ref. 22. First, it should be noted that the two studies are based on fundamentally different chip designs (Ref.\n22 employs a 100-nm-thick ultra-high Q device, whereas ours employs a 300-nm-thick structure). Below, we systematically\noutline the key distinctions of our work:\n1. Energy Efficiency: Reference 22 utilizes an add-drop microresonator, with each comb line exhibiting only -20 dBm\noutput power. In this manuscript, with special over-coupling design, we achieve >60% conversion efficiency, resulting\nin exceeding -10 dBm power for each combline.\n2. Channel spacing: The 100-nm-thick SiN is hard to get high-Q resonator with larger FSR (>40 GHz). This design choice\ninherently limits their capability to support higher-speed signal at each carrier. Based on 300-nm-thick SiN platform, it\nis easy to realize high-Q microresonator with large FSR >100 GHz for high single-channel transmission. In our revision,\nrather than relying on single-channel demonstrations, we successfully achieved ultra-high data rates using 110-Gbaud\nDP-32QAM, corresponding to over 1 Tbps, across all 16 comb lines (Response to Comment 2), which strongly supports\nour claims.\n3. Cost: Reference 22 intended to realize ultra-low-noise sources. To suppress the phase noise as much as possible, the\nprior work adopted the ultra-low-loss photonic circuits based on 100-nm-thick SiN. Such extraordinary platform\nrequires complete and costly fabrication processes and is difficult to obtain commercially at present. By contrast, the\n300-nm-thick SiN is widely available [CUMEC-CSiN300, IMB-CNM & VLC Photonics, LIGENTEC, GLOBALFOUNDRIES],\nand the fabrication process is much simpler. This ensures the universality and low cost of this solution.\n4. Compactness: Regarding system architecture, Ref. 22 employs multiple DFBs for injection locking, each requiring\nindividual laser drivers (LD) and thermoelectric cooler (TEC) control, which inherently limits its suitability for\nlightweight transmission systems. By contrast, our system fully exploits the inherently high conversion efficiency and\nlow noise of the designed light source, aiming for greater simplicity than other microcomb based systems. To further\nstrengthen this claim, in our revised manuscript, we have conducted additional lightweight transmission experiment\nby replacing bulky system components with integrated ones, such as SOAs and integrated waveshaping chip (IWC)\nfor WDM operation (Response to Comment 3). Those compact devices, to the best of our knowledge, have not yet\nbeen simultaneously adopted in other comb-based transmission systems. This integration enables a significantly more\ncompact transmitter architecture, achieving nearly an 80-fold reduction in system size compared with our previous\ndemonstration. Even under the noisy SOA amplification and extra insertion loss from the waveshaping chip, the system\nstill performs a 16 WDM transmission with over 5 Tbps aggregation rate, showing promise in noise tolerance and\ncompact-system suitability of the proposed light source.\n5. Performance analysis with quantified experimental verification: In our newly revised manuscript, to better clarify\nhow the high OCNR and noise-suppression effect in a comb source affect the transmission results, systematic analysis\nhas been conducted (Response to Comment 2). The relationship between baud rate and noise-OCNR is experimentally\nexplored by the substituting light source with different linewidth and varying emission intensity in each of them. The\ncharacterization provides critical insights for future high-coherence transmission experiments.\nComment 2: \"Second, when it comes to the 1 Tbps claim, this is shown only for one of the comb lines, i.e., the pump line. The authors\nshould also characterize other lines in the same way (Fig. 2g). Will there be a penalty due to the lower power / higher noise?\nWith only one line, their 1 Tbps is not that novel, see ,e.g., [Buchali, 1-Terabit/s Net Data-Rate Transceiver Based on Single-\nCarrier Nyquist-Shaped 124 Gbaud PDM-32QAM], or [First Single-Carrier Transmission at Net Data Rates of 1.6 Tb/s over\n9075 km and 2.4 Tb/s over 1210 km Using 300 GBd Dual-Polarization Signals and Probabilistic Constellation Shaping]. \"\nOur reply: Thanks for these valuable comments and questions. In our revised manuscript, to better demonstrate the\ntransmission potential of a low-noise comb source, we carried out over 1 Tbps data transmission utilizing all 16 high-\npower microcomb carriers under a WDM configuration, as shown in the following Fig. 3(a). All channel achieved BER under\n7E-3 (Fig. 3(b)). Accordingly, we have added the following description of the new experiments.\n(Result, page 11) SIL comblines are divided into odd and even banks to simulate real-world communication scenarios. First,\nwe build up a 1 km self-hemodyne coherent transmission system to explore the maximum capacity of the comelines.\nLimited by the channel spacing of 100 GHz, we artificially doubled the spectral interval through WSS, as shown in Fig. 3(b),\nand distinguish by transparency. Thanks to the high OCNR with power levels above -10 dBm, all channels can support 110\nGBaud DP-32QAM signal transmissions in the WDM configuration, indicating single-channel rate of 1.1 (net 1.008) Tbps.\nFig. 3 SMF transmission system. (a) Schematic diagram of the high-speed node-to-node transmission system for short-reach\ncampus/edge networks and metropolitan-scale optical transmission. (b) The self-homodyne-based campus/edge\ninterconnect system achieves per-channel transmission rates exceeding 1 Tbps across all wavelength channels. (c)\nConstellation diagram of DP-32QAM.\nIn addition, to provide more quantitative experimental evidence of how low OCNR and coherence impact transmission\nperformance, we performed extensive experimental characterization, as shown in the following Fig. 2(e). To emulate\ndifferent conditions, benchtop lasers with varying linewidths were employed, with the OCNR of each laser tuned through\nits output power. The results indicate that both high coherence and OCNR are crucial for supporting high transmission\nspeeds, capabilities that our proposed microcomb inherently offers.\nFig. 2 Integrated coherent comb source generation and the effect of light source on transmission. (e) The influence of\nOCNR and linewidth on the maximum net symbol rate is evaluated under the error-free condition. The red pentagrams in\nthe figure trace the degradation path of the light source in the communication system.\nComment 3: \"If the selling point is to also demonstrate the high data rate with MCF, FMF, RCF, there has been already works\nbringing this approach tothe extrem: [22.9 Pb/s data-rate by extreme space-wavelength multiplexing] with a few-modes\nMCF providing 114 spatial channels (30 Tbps/wavelength).\"\nOur reply: We are sorry for any misleading in the original manuscript. Actually, this work aims to provide deeper insights\ninto an ultra-compact microcomb-based transmission system capable of supporting high-capacity links between space-\nconstrained supernodes of computing units. Multiplexing techniques such as MCF, FMF, and RCF represent potential\nsolutions for enabling multi-node aggregation in transmission networks. Here, we demonstrate that a lightweight\ntransmission system based on a self-injection-locked microcomb source can be organized in this manner.\nWe thank the reviewer for stimulating our consideration of the key selling points of this work. To further substantiate the\n“lightweight” claim, we propose a chip-level transmitter by replacing bulky components with integrated ones, such as\nSOAs and integrated waveshaping chips (IWCs) for WDM operation, as shown in Fig. 5(a–c). The results demonstrate per-\nchannel data rates exceeding 320 Gbps, with an aggregate capacity of over 5 Tbps, as shown in Fig. 5(e). Moreover, the\nhigh conversion efficiency and narrow linewidth of the proposed SIL microcomb source play a critical role in mitigating the\ndegradation induced by additional noise of integrated devices. As analyzed in Fig. 5(f–g), compared with commercial EDFAs,\nSOA amplification introduces more severe frequency noise and OSNR degradation, yet the SIL microcomb exhibits strong\nresilience against these impairments.\nFig. 5 Highly integrated transmitter demonstration. (a) Lightweight Transmitter Scheme. (b) Physical Diagram of the\nTransmitter Module. (c) Microphotograph of the SiPh integrated waveshaping chip. (d) Intrinsic linewidth characteristics of\nindividual combline. The black pentagrams in the figure denote the combline generated by the microwave-driven electro-\noptic frequency comb. (e) Transmission with a symbol rate of 40 Gbaud and DP-16QAM modulation format. Partial\nconstellation diagrams and corresponding EVM values are provided. Eleven channels are considered to achieve error-free\ntransmission. (f) Power spectral density of frequency noise, including components from comb lines (0, 2, 6, and -8), as well\nas noise levels when the InP-DFB and comb line 6 are amplified to 10 dBm by an SOA and EDFA respectively. (g) OCNR\ndegradation induced by SOA and EDFA at 10 dBm output power.\n(Result, page 17) A highly integrated system is essential for realizing lightweight transmission in distributed edge nodes,\nespecially under stringent cost and footprint constraints. In this section, beyond integrated light sources, we present a chip-\nlevel parallel carrier generator where bulky WSSs and EDFAs are replaced by SOAs and silicon photonic IWCs. Figure 5(a)\nillustrates the architecture of the chip-level transmitter module, with photographs of all modules provided in Fig. 5(b). The\nIWC is fabricated using mature silicon photonics technology, featuring cascaded microring resonators with a free spectral\nrange (FSR) of approximately 1.3 THz. Microheaters placed above the microrings allow tuning of resonant frequencies to\nadjust the output spectrum, as detailed in Supplementary Information Note 5. To suppress thermal crosstalk, adjacent\nmicrorings are physically separated by etched trenches, as illustrated in Fig. 5(c). Since not all comblines require power\nequalization, we achieve uniform power distribution across all spectral lines using only 12 microrings. After the IWC, all 16\ncomblines are equalized to -18 dBm, accounting for an 8 dB insertion loss. The carriers are then amplified by an SOA and\nrouted through another IWC for odd-even channel separation. Separated carriers are modulated by 35-GHz-bandwidth IQ\nmodulators, combined, and then amplified through an SOA before transmission. As demonstrated in Fig. 5(e), a 10-km\ntransmission at 5.12 Tbps (net 5.015 Tbps) is achieved using 40-GBaud DP-16QAM modulation. The BER trend per channel\naligns consistently with the linewidth values as shown in Fig. 5(d), with comblines below 300 Hz linewidth achieving error-\nfree operation.\nIt is noteworthy that the capacity of the present chip-level transmitter is lower than that of systems based on bulky devices.\nThis primarily stems from carrier performance degradation caused by integrated components, which featuring higher noise\nfigures and insertion losses than their benchtop counterparts. Specifically, the IWC contributes an additional 3 dB insertion\nloss compared to benchtop WSS. SOAs, while far more compact than EDFAs, introduce excessive amplified spontaneous\nemission (ASE) noise. Meanwhile, their high α-factor and nonlinear effects (notably XPM) further induce cumulative phase\nnoise and waveform distortion in high-speed systems46,47. Figure 5(f) and (g) present the corresponding noise and OSNR\ndegradation after amplification. When amplified to 10 dBm, the linewidth of channel 6 increases of approximately threefold\nand tenfold via EDFA and SOA respectively. In addition, the OCNR decreases by 6 dB and 12.5 dB respectively. Despite these\nimpairments, the SIL light source still enables >5 Tbps transmission within the chip-level lightweight system, due to its\noriginal superior coherence and OCNR. For comparation, we implement a reference system using a 45-GHz-spacing electro-\noptic frequency comb pumped by an N7714A ECL (Fig. 5(d)). Under identical conditions, severely degraded constellation\ndiagrams are obtained due to its poor original coherence (Fig. 5(e) black pentagrams).\nComment 4: \"Finally, the authors claim 200 tbps to be the highes with an integrated source, but already Ref.21 in 2018\nshowed 600 tbp, and maybe I am missing other examples.\"\nOur reply: Thanks for raising this important point. Ref. 21 is a great pioneering work that achieved over 100 Tbps data\ntransmission. While it is worth noting that this work was performed based on supercontinuum generation, where a high-\npeak-power femtosecond laser is injected into an integrated waveguide. The high-peak-power femtosecond laser is not\nintegrated in this work. And the femtosecond laser currently still faces significant challenges in on-chip integration, which\nwe believe limits the system's overall integration level. Therefore, we emphasize a highly integrated transmitter light source,\nand we apologize for any confusion caused by our original wording. In the revised manuscript, we have replaced 'integrated'\nwith 'on-chip' for clarity.\n(Result, page 14) As far as we are aware, this represents the highest rate realized with an integrated on-chip light source\nover the entire C-band, significantly simplifying the cumulative device requirements while avoiding saturation of the\nerbium-doped fiber amplifier (EDFA).\nComment 5: \"The manuscript, including methods and supplementary material, does not provide detailed description of:\nmicroresonator used (although I assume is the one from Ref 22), the soliton state, all equipment used, DSP, etc. The lack of\ndetails prevents properly evaluating the veracity of their results and questions its reproducibility. \"\nOur reply: In the revised manuscript, we have provided more comprehensive descriptions of the microcomb and the DSP\n(digital signal processing) procedures, including the specific models of key components such as the EDFA, modulator, and\nAWG used in the experiments.\n(Matericals and Methods, page 23) The fabricated microresonator exhibits a free spectral range of 100 GHz (aligned with\nthe DWDM ITU grid spacing standard), a Q-factor of approximately 1.7 × 10⁷, and a coupling loss of ≤ 2.5 dB/facet @ 1550\nnm. The microring resonator adopts a racetrack configuration, with Euler bends on both curved sections. The coupling gap\nis 1 μm, and the coupling length is 110 μm, forming an overall over-coupled structure for high conversion efficiency.\n(Matericals and Methods, page 24) By fine-tuning the position of the six-axis stage, the generation of dark pulse\nmicrocombs can be observed on the optical spectrum analyzer (as shown in Fig. 2(d)). Stable microcomb generation is\nsustained for over 1000 minutes.\n(Matericals and Methods, page 28) A 256-GSa/s real-time oscilloscope (KEYSIGHT UXR0594AP) with 59-GHz bandwidth\ncaptures waveforms from four channels and sends them to a computer for DSP. In the context of DSP, at the transmitter\nside, we initially generate a PRBS sequence for QAM mapping, followed by 0.01 Root Raised Cosine pulse shaping, and then\nresample the signal before sending it to the AWG. On the receiver side, the captured signal undergoes sequential processing\nincluding resampling, frame synchronization, dispersion compensation, carrier frequency offset estimation using the\nfourth-power algorithm, adaptive MIMO equalization, carrier phase recovery through a two-stage blind phase search\nalgorithm (with filter lengths of 32 and 8 for the first and second stages, respectively), demodulation, and BER calculation.\nIt is noteworthy that during the verification of the relationship between OCNR and linewidth versus maximum net rate,\nDSP section utilized an 81-tap adaptive MIMO equalizer. In other experimental scenarios, the use of a 41-tap MIMO\nequalizer with reduced compensation capability and the decreased received OSNR per combline caused by WDM\ncollectively lead to a degradation in achievable symbol rate compared to the former configuration.\nThe specifications/model numbers of all equipment used are provided.\n(Matericals and Methods, page 27) The experimental results presented in Fig. 2(e) were obtained using multiple light\nsources with varying linewidth characteristics: NKT Photonics (1 Hz), Comb0 (25 Hz), Comb1 (81.64 Hz), Comb5 (220 Hz),\nSANTEC TSL-510 (1.576 kHz), RIO ORION-1550-30-15-M (5 kHz), KEYSIGHT N7714A ECL (10.4 kHz), ALNAIR TLT-200 (20 kHz),\nAPEX AP3350A (238 kHz), and CONQUER CUSTOMIZED (628 kHz), along with two cases that failed demodulation - an InP\nDFB (3 MHz) and BOXOPTRONICS CUSTOMIZED (8.8 MHz). Throughout the transmission experiments, the KEYSIGHT\nN7714A ECL served as the LO to maintain phase reference stability.\n(Matericals and Methods, page 27) The WSS (Finisar Waveshaper 4000s) (with 5 dB insertion loss) splits these channels\ninto odd/even paths while performing power equalization.\n(Matericals and Methods, page 27) Subsequently, the light source carrying 16 wavelengths is amplified by an amplifier to\nboost the power of each channel, with the aggregate power reaching approximately 13 dBm prior to entering two 35-GHz\n3dB bandwidth IQ modulators (Sumicem T.SBXH1.5PL-35PD-ADC). Both paths are simultaneously modulated by data\ngenerated from a 128-GSa/s Arbitrary Waveform Generator (AWG-M9505A).\n(Matericals and Methods, page 27) The transmission link consists of an EDFA (KEOPSYS) for signal amplification,\nmultiplexers/demultiplexers, and multidimensional multiplexing fiber to validate the optical comb's transmission\nperformance.\n(Matericals and Methods, page 28) A 256-GSa/s real-time oscilloscope (KEYSIGHT UXR0594AP) with 59-GHz bandwidth\ncaptures waveforms from four channels and sends them to a computer for DSP.\n(Supplementary Note 4) Fig. S3 Detailed Schematic Diagram of the Communication System; OC: Optical Coupler. PD:\nPhotodetector. WSS: Wavelength Selective Switch. AWG: Arbitrary Waveform Generator. LO: Local Oscillator. EDFA: Erbium-\nDoped Fiber Amplifier. PC: Polarization Controller. VOA: Variable Optical Attenuator (CETC AV6381B). BPD: Balanced\nPhotodetector (Finisar BPDV3120RQ). Mixer (Optolex).\nComment 6: \"The authors highlight the power conversion efficiency, but what about the wall-plug efficiency? How does it\ncompare to other similar approaches?\"\nOur reply: Our InP-DFB laser operates with a laser voltage of 1.564 V and current of 300 mA, delivering an output power\nof 18 dBm (63.1 mW). The wall-plug efficiency (WPE) is calculated as: 63.1/469.2 = 13.45%.\nThis performance falls within a relatively ideal range (9-16%) [Opt. Express 30, 27983-27992 (2022)]. The primary\nlimitations come from the laser's intrinsic quantum efficiency as well as optical losses caused by reflection and absorption.\nCompared to existing literature, our WPE does not show significant advantages. However, when considering the product of\nWPE and power conversion efficiency [Journal of Lightwave Technology 38, 5517-5525 (2020)], our design demonstrates\na clear superiority (inferred ~18 dB). We have now included this information in the main text.\n(Result, page 9) A laser diode chip, which exhibits a wall-plug efficiency of 13.45%, is directly coupled with the designed\nsilicon nitride (SiN) microresonator chip.\nComment 7: \"The authors performed several transmission demonstrators with different symbol rates, modulation formats,\nwith SMF, MCF, FMF, RCF. They could consider having a simple way to indicate them, e.g, table or in the respective figures.\"\nOur reply: Thanks for the valuable suggestions from the reviewers. We have provided all the experimental tables to clarify\nthe overall context of all the experiments, in the SI.\n(Supplementary Note 6) To better present the experimental results and conceptual framework, we have tabulated the\nobtained data. Experiments 1 and 2 primarily demonstrate transmission in short-range campus/edge networks and\nmetropolitan area networks. Experiments 3–5 employ SDM to showcase multi-node aggregated data transmission.\nExperiment 6 achieves more integrated lightweight transmission through the use of highly integrated components such as\nSOA and IWC.\nTable S3. Tabulation of experimental results.\nSymbol Raw Summation Net\nSignal Multiplexing Local\nrate capacity Net rate rate/λ/core\nformat scheme oscillator\n[Gbaud] [Tbps] [Tbps] [Gbps]\n1 110 DP-32QAM 838 8.064 1008 1 km-SMF SIL-Comb\n2 70 DP-16QAM 8.96 8.37 523 160 km-SMF ECL\n3 70 DP-16QAM 215.04 200.97 523 2 km-24MCF ECL\n4 40 DP-16QAM 10.24 9.57 598 25 km-FMF ECL\n5 70 SP-16QAM 8.96 8.37 523. 50 m-RCF ECL\n6 40 DP-16QAM 5.12 5.015 313 10 km-SMF ECL\nComment 8: \"Some typos:\n-line 140: “combines”\n- line 247 : “include”\n- Line 293 “perabit”\n- Line 252\nFig. 5 : this should be just for comb-based transmission experiments. \"\nOur reply: We have meticulously examined all technical details and implemented corresponding revisions. We sincerely\nappreciate the reviewers' rigorous scientific approach.\n(Result, page 5) For adequate OCNR, we select the central 16 comblines with power exceeding -10 dBm as parallel optical\ncarriers.\n(Result, page 15) Besides, we show the first proof-of-concept mode-division multiplexed (MDM) multi-dimensional\ntransmissions includes LP modes in few-mode fiber (FMF) and OAM modes in ring-core fiber (RCF) driven by integrated\nphotonic light source.\n(Result, page 21) Despite the total capacity is below the petabit-per-second scale compared to state-of-the-art\ndemonstrations, a higher channel capacity and streamlined nature of this light source would significantly reduce the\nfootprint and overhead associated with channel scaling, making it well-suited for compact edge infrastructure.\n(Results, page 12) Compared with a high-performance tunable ECL1 with a ~10 kHz linewidth (gray dots), the self-injection\nlocking scheme (gray dots purple dots) exhibits a 3 dB lower OSNR requirement at the same EVM level due to the parallel\nhigh coherence.\n(Discussion, page 22) Fig. 6 Review of comb-based coherent transmission systems.\nComment 9: \"In summary, the authors would need to position their work a bit more fairly and more clearly with respect to\nthe state of the art in a meaningful way before the manuscript can be accepted.\"\nOur reply: We sincerely appreciate the time and effort the reviewers dedicated to providing such valuable feedback. The\ncore innovation of our work lies in lightweight transmission, which encompasses two key aspects: power\nconsumption/energy efficiency and size/cost reduction. Overall, we have supplemented three additional experiments to\nsupport our claims, as shown in above discussion and concluded below.\n(1) We have supplemented experiments investigating the relationship between transmission rate and noise-OCNR (Fig.\n2(e)). These were conducted to further demonstrate the advantages of our light source in coherent systems, and to\nprovide clearer guidance for subsequent experiments.\n(2) We have achieved a transmission capacity of 1 Tbps/λ across all carrier wavelengths (Fig. 3(b)), demonstrating the\nsuperior parallel transmission capability of our light source.\n(3) We demonstrate the system using chip-level components (Fig. 5(e)), with 80 times smaller compared with our\nprevious demonstrations and confirm that our light source exhibits significantly higher tolerance to both OSNR\ndegradation and coherence impairment.\nWe greatly appreciate the reviewer's suggestions, which have significantly contributed to the revision of the manuscript.\nResponse to the report from the Referee #3\nGeneral comments: \"This manuscript reports technically work demonstrating high-speed multidimensional optical\ncommunication utilizing a self-injection-locked (SIL) dark-pulse microcomb. The authors ascribe the achieved high baud rate\nand 1 Tbps per-channel performance to the noise suppression facilitated by injection locking. However, in comparison with\nexisting literature, this study does not introduce a fundamentally novel device architecture or a system-level innovation of\ntransformative significance. Rather, the primary contribution appears to be the enhancement of single-carrier transmission\nrates, achieved at the cost of a reduced number of utilized channels, without providing substantial forward-looking\nperspectives. Consequently, I believe the scope and impact of this work might be more appropriately aligned with the focus\nof specialized journals in photonics or communications. The reasons I'm not entirely convinced by this work are listed below.\"\nOur reply: We sincerely appreciate the reviewers' valuable comments. Here, we would like to further elaborate on the\nsignificance and innovative aspects of our work. We have provided a detailed, point-by-point response to clarify the\ntechnical aspects and address all raised concerns. We also conducted additional experiments to further support our claims.\nFirst of all, we would like to clarify that our work specifically addresses the communication and aggregation challenges\namong distributed edge computing nodes [1]. In such scenarios, an excessive number of wavelength channels imposes\nsignificant pressure on hardware components. Our primary goal is to develop a lightweight parallel transmission system,\nwith reduced volume, power consumption and cost, to meet the growing high-capacity demands of network edges and\nmodular data centers in space-constrained scenarios.\nWe understand the reviewer's concerns mainly focus on three aspects:\n(1) First, the reason why such a comb source could support superior transmission lacked quantitative support, and the\ndifferences from previous work were not specified in detail.\n(2) Second, our emphasized single-carrier rate transmission capability comes at the cost of reduced channel count. The\npresentation of parallelism is insufficient.\n(3) Third, the system is not \"lightweight\" enough, as some components such as WSS and EDFA cannot be modularized,\nwhich contradicts the lightweight architecture.\nFor (1): We conducted additional experiments to quantify the relationship between the maximum transmission rate and\nOCNR and linewidth of the laser carrier. The results demonstrate that the high coherence and high conversion efficiency\nof our light source strongly support such high-speed transmission. (Response to Comment 1). In the revised main text,\nnewly added Fig. 2(e) presents such relationship. Moreover, the superior coherence and OCNR provide strong resilience\nagainst amplification-induced degradation, allowing the system to tolerate the additional noise introduced by SOAs when\nreplacing bulky EDFAs, thereby enabling a more compact configuration. Supplementary experiments are also performed as\nin newly added Fig. 5 for analysis on such impact.\nIn comparison, none of the currently available integrated optical frequency combs (typically featuring around 10 kHz\nlinewidth and 40 dB OCNR) could reach such performance while remaining compact. Also, compared to previous work\n(e.g., Ref. 22), our design achieves significantly improved integration simplicity. In terms of device architecture, we reduced\ncomponents by removing additional LDs and TEC controllers, as we require only a single DFB pump. Regarding power\nefficiency, our design achieves higher conversion efficiency compared to prior solutions. Most importantly, Ref. 22 primarily\naimed to realize an integrated ultra-low-noise parallel source, which required ultra-low-loss integrated photonic circuits\n(thin SiN). Such platforms are costly and difficult to obtain commercially. At the system level, we obtained remarkable\ntransmission results - achieving 200 Tbps using just 16 comblines. This demonstration breaks the conventional paradigm\nby scaling up the capacity of each channel in a micro-parallelism system with low system overhead, rather than scaling up\nchannel numbers with relatively low per-channel data rates.\nFor (2): We firmly believe that enhancing single-carrier rates holds significant value - indeed, this represents a critical\nperformance metric where integrated optical frequency combs currently lag behind bulk laser systems [2,3]. As mentioned\nbefore, an excessive number of comblines does not necessarily translate to practical advantages, especially in resource-\nconstrained scenarios. Through innovative microring resonator design, we achieve more concentrated energy distribution\nwithin targeted spectral regions (as elaborated in the Supplementary Information). While our initial single-carrier 1 Tbps\ntransmission is indeed lack convincement, in the revised manuscript, we have substantiated our approach by\ndemonstrating uniform 1 Tbps transmission (110 Gbaud DP-32QAM) across all 16-comblines (Fig. 3(b)) (Response to\nComment 1-c). Implemented via our self-homodyne architecture, this solution unlocks the potential of ultrahigh per-\nchannel rate parallel transmission, making it well-suited for short-reach campus and edge network environments with\nstringent bandwidth demands.\nFor (3): We performed a proof-of-concept lightweight transmission link, by replacing the bulk WSSs and EDFAs with\nintegrated waveshaping chips and semiconductor optical amplifiers, in the revised manuscript. By leveraging integrated\nphotonic devices, the system volume is reduced by 80-fold. We find that such replacement degrade both the carrier\nlinewidth and the received OSNR. However, thanks to its high carrier power and narrow linewidth, the SIL microcomb\nexhibits significantly high tolerance to both OSNR degradation and coherence impairment. Comparative experiments are\nalso conducted with EO combs, which further confirm that the proposed SIL microcomb source can withstand such\ndegradation (Response to Comment 2).\nIn conclusion, this work introduces both the concept and the first practical demonstration of a chip-level lightweight optical\ntransmission system. It represents a paradigm shift toward greener, higher-density compute-and-transport architectures,\nwith broad potential impact across fields such as high-performance computing and intelligent manufacturing. To address\nthe novelty concerns raised by reviewers, we have substantially revised the manuscript and added three compelling new\nexperiments. We hope that the responses provided below fully address the reviewer’s concerns. We sincerely thank the\nreviewer for their thorough and thoughtful review.\n1. Xing, S., Sun, A., Wang, C. et al. Seamless optical cloud computing across edge-metro network for generative AI. Nat\nCommun 16, 6097 (2025).\n2. R. Rios-Müller et al., \"1-Terabit/s net data-rate transceiver based on single-carrier Nyquist-shaped 124 GBaud PDM-\n32QAM,\" Optical Fiber Communications Conference and Exhibition (OFC), Los Angeles, CA, USA, pp. 1-3, (2015).\n3. H. Mardoyan et al., \"First Single-Carrier Transmission at Net Data Rates of 1.6 Tb/s over 9075 km and 2.4 Tb/s over 1210\nkm Using 300 GBd Dual-Polarization Signals and Probabilistic Constellation Shaping,\" European Conference on Optical\nCommunication (ECOC), Frankfurt, Germany, pp. 1805-1808, (2024).\nComment 1: \"The authors attribute the high baud rate and 1 Tbps/channel performance to noise suppression via injection\nlocking, but this claim lacks quantitative support.\"\nOur reply: We sincerely appreciate the reviewers' questions. In response to the request for quantitative support evidence,\nwe have conducted additional experiments.\nTo systematically investigate the relationship between OCNR, linewidth and baud rate, we conducted extensive\nexperiments utilizing dozens of optical sources with varying linewidths, with the OCNR also varies with the change of laser\noutput power. All transmission systems employed DP-16QAM modulation with homodyne detection, maintaining\nconsistency with our previous experimental configuration. The corresponding results are presented in Fig. 2(e), clearly\nshows that high OCNRs (high powers) and narrow linewidths are the basis for high transmission rates.\nFig. 2 Integrated coherent comb source generation and the effect of light source on transmission. (e) The influence of OCNR\nand linewidth on the maximum net symbol rate is evaluated under the error-free condition. The red pentagrams in the\nfigure trace the degradation path of the light source in the communication system.\n\"(a) Please provide comparative data (OCNR, linewidth/phase noise, combline power) between the SIL and non-SIL combs.\nHow do these differences translate to single-wavelength capacity?\"\nOur reply: (a) Figures 2(a) and (d) show the OCNR of all comblines under non-SIL conditions. The OCNR at the pump position\nremains approximately 72.86 dB before and after SIL. After completing the SIL process, energy is redistributed to other\ncomblines through four-wave mixing, resulting in an OCNR of about 67.45 dB for comb0. Considering the lowest comb line,\nthe OCNR is approximately 50 dB. The linewidth is approximately 3 MHz for InP-DFB without SIL but narrows to 25 Hz after\nSIL implementation, as shown in Fig. 5(d) and (f).\nFig. 2 Integrated coherent comb source generation and the effect of light source on transmission. (a) The pump light source\ninput (including insertion loss), at 1555.37 nm. (b) Physical image of microcomb generation. (c) Normalized coupling\ndiagram. (d) SIL comblines generate with 16 channels (over -10 dBm) ranging from 1549.17 nm to 1560.84 nm.\nFig. 5 Highly integrated transmitter demonstration. (f) Power spectral density of frequency noise, including components\nfrom comblines (0, 2, 6, and -8), as well as noise levels when the InP-DFB and comb2 (1556.94 nm) are amplified to 10 dBm\nby an SOA and EDFA respectively.\nFor clear and concise comparison, we have listed several representative works in the field. Our work demonstrates\nsignificant advantages in both linewidth performance and OCNR characteristics. Because of that, we have achieved multi-\nfold improvement in single-carrier capacity, and it accords with the quantified analysis shown in Fig. 2(e) above.\nOCNR linewidth/phase noise single combline power\nNature 546, 274–279 (2017). ~40 dB <100 kHz -20 dB\nNature Photon 12, 469–473 (2018). ~20 dB 40 kHz -20 dB\nNat Commun 9, 1598 (2018). ~45 dB <10 kHz -15dB\nNat Commun 11, 2568 (2020). ~30 dB —— <-40 dB\n107~1.2k Hz\nPhotonics Research 12, 2573-2580\n~32 dB (ultra-narrow linewidth -28 dB\n(2024).\nfiber laser pump)\nNat Commun 16, 6387 (2025). ~40 dB —— -6 dB\n25~600 Hz\nThis works >50 dB -10 dB\n(DFB pump)\nThe \"——\" indicates that no specific value is explicitly stated in the text. However, the soliton generation method described\nin the aforementioned literature results in combline linewidth characteristics that are correlated with the pump source,\nand are therefore dependent on the performance of the laser used.\n\"(b) The explanation for setting the baud rate based on OCNR (lines 186-187) is unclear. What is the precise relationship\nbetween OCNR and maximum baud rate per channel? Why does the SIL comb achieve higher baud rates than other sources?\nSupporting analysis is required.\"\nOur reply: (b) Thanks for identifying these issues. We acknowledge the lack of clarity in our original presentation and have\naccordingly revised the manuscript to address these concerns. The symbol rate was set to 70 Gbaud after considering the\ncombined impact of all optical components (including modulator, optical amplifier, and WSS), and the degraded coherence\nof the edge comblines.\n(Result, page 12) The symbol rate is limited to 70 Gbaud due to constraints from the power level and linewidth\ncharacteristics of the edge comblines, while simultaneously satisfying requirements for fiber transmission loss and\ncomponent insertion losses. A DP-16QAM signal is then modulated onto the parallel carriers, which are subsequently\ncombined and transmitted through a 160-km standard SMF.\nTo further investigate the impact of source noise on the transmission system performance, we conducted experimental\nverification using laser sources with dozens of different noise levels. The experimental results, as detailed in Fig. 2(e),\ndemonstrate that the narrow linewidth achieved through self-injection locking significantly improves the performance of\nhomodyne communication systems. Detailed analysis has been included in the revised manuscript. Additional comparative\nexperiments with other comb sources in Fig. 5(d, e) further validate the feasibility of our approach.\nFig. 5 Highly integrated transmitter demonstration. (d) Intrinsic linewidth characteristics of individual combline. The black\npentagrams in the figure denote the combline generated by the microwave-driven electro-optic frequency comb. (e)\nTransmission with a symbol rate of 40 Gbaud and DP-16QAM modulation format. Partial constellation diagrams and\ncorresponding EVM values are provided. Eleven channels are considered to achieve error-free transmission.\n(Result, page 9) To quantitatively verify the necessity of such high-performance sources for high-capacity transmission, we\nconduct a systematic investigation of the impact of linewidth and OCNR on optical communication systems under back-to-\nback (BTB) conditions. The experimental link transmits DP-16QAM signals as described in the Methods, wherein a Keysight\nN7714A external cavity laser (ECL) with 10-kHz linewidth serves as the local oscillator (LO). Optical carrier linewidths are\nvaried from 1 Hz to 10 MHz, provided by different commercial lasers and comblines of the SIL microcomb. The OCNR is\nadjusted by controlling the laser intensity via a variable optical attenuator. Intuitively, high-speed transmission systems\nrequire coordinated optimization of both OCNR and laser linewidth characteristics. While the degradation of OCNR critically\nimpacts transmission, light sources with superior coherence properties, could partially alleviate such degradation. With\nnarrow linewidth (200 Hz for example), an OCNR of ~45 dB suffices to achieve transmission rate exceeding 100 GBaud,\nwhere a higher OCNR provides negligible improvement. Importantly, maintaining a linewidth <1 kHz is essential to achieve\nAs coherence progressively deteriorates, the accumulated phase noise not only elevates the BER at the receiver but also\ndisrupts frequency offset estimation in the offline digital signal processing. This impairment leads to failed carrier phase\nrecovery, loss of phase synchronization, and ultimately complete system failure.\n(Results, page 18) For comparation, we implement a reference system using a 45-GHz-spacing electro-optic frequency comb\npumped by an N7714A ECL (Fig. 5(d)). Under identical conditions, severely degraded constellation diagrams are obtained\ndue to its poor original coherence (Fig. 5(e) black pentagrams).\n\"(c) The 1 Tbps record relies on a single high-power comb line. This does not represent the system's parallel performance\nand weakens the claim of a system-level breakthrough based on the microcomb.\"\nOur reply: (c) We acknowledge the reviewer's keen insight. To enhance parallelism, we have demonstrated all comblines\nachieving 1 Tbps transmission rates. The modifications have been incorporated into the manuscript.\nFig. 3 SMF transmission system. (a) Schematic diagram of the high-speed node-to-node transmission system for short-reach\ncampus/edge networks and metropolitan-scale optical transmission. (b) The self-homodyne-based campus/edge\ninterconnect system achieves per-channel transmission rates exceeding 1 Tbps across all wavelength channels. (c)\nConstellation diagram of DP-32QAM.\n(Result, page 11) First, we build up a 1 km self-hemodyne coherent transmission system to explore the maximum capacity\nof the comelines. Limited by the channel spacing of 100 GHz, we artificially doubled the spectral interval through WSS,\nas shown in Fig. 3(b), and distinguish by transparency. Thanks to the high OCNR with power levels above -10 dBm, all channels\ncan support 110 GBaud DP-32QAM signal transmissions in the WDM configuration, indicating single-channel rate of 1.1\n(net 1.008) Tbps.\nComment 2: \"The authors frequently emphasize the \"lightweight\" nature of the system, attributed to the compactness and\nconversion efficiency of the SIL comb.\"\nOur reply: Thanks for these insightful questions regarding the lightweight aspects. We consider both the high efficiency\nand coherence properties of the SIL comb to be the critical enablers for lightweight transmission systems. We have\nconducted extensive supplementary experiments to address these concerns and provide point-by-point clarifications below:\n\"(a)However, reliance on external EDFA amplification and WSSs for spectral shaping/equalization (Supplementary Note 4)\ncontradicts the compactness claim. The authors should propose mitigation strategies or quantify the hardware overhead.\"\nOur reply: (a) The reviewer is correct that EDFAs and WSS would compromise the system's lightweight nature. To better\ndemonstrate system-level lightweight transmission, we replaced EDFAs with more integrated SOA chips and substituted\nbulky WSS with compact silicon photonic waveshaping chips (IWC), achieving over 5 Tbps WDM transmission while\nreducing overall size to 100 cm2*3cm, as shown in Fig. 5. The trade-off for lightweight design is higher insertion loss and\ndegraded coherence performance introduced by integrated devices. Nevertheless, it is the high conversion efficiency and\nhigh output power characteristics that help this comb source tolerate the additional insertion loss from IWC and the\nseverely degraded ASE noise and linewidth broadening induced by SOA.\nFig. 5 Highly integrated transmitter demonstration. (a) Lightweight Transmitter Scheme. (b) Physical Diagram of the\nTransmitter Module. (c) Microphotograph of the SiPh integrated waveshaping chip. (d) Intrinsic linewidth characteristics of\nindividual combline. The black pentagrams in the figure denote the combline generated by the microwave-driven electro-\noptic frequency comb. (e) Transmission with a symbol rate of 40 Gbaud and DP-16QAM modulation format. Partial\nconstellation diagrams and corresponding EVM values are provided. Eleven channels are considered to achieve error-free\ntransmission. (f) Power spectral density of frequency noise, including components from comb lines (0, 2, 6, and -8), as well\nas noise levels when the InP-DFB and comb6 are amplified to 10 dBm by an SOA and EDFA respectively. (g) OCNR\ndegradation induced by SOA and EDFA at 10dBm output power.\n(Result, page 17) A highly integrated system is essential for realizing lightweight transmission in distributed edge nodes,\nespecially under stringent cost and footprint constraints. In this section, beyond integrated light sources, we present a chip-\nlevel parallel carrier generator where bulky WSSs and EDFAs are replaced by SOAs and silicon photonic IWCs. Figure 5(a)\nillustrates the architecture of the chip-level transmitter module, with photographs of all modules provided in Fig. 5(b). The\nIWC is fabricated using mature silicon photonics technology, featuring cascaded microring resonators with a free spectral\nrange (FSR) of approximately 1.3 THz. Microheaters placed above the microrings allow tuning of resonant frequencies to\nadjust the output spectrum, as detailed in Supplementary Information Note 5. To suppress thermal crosstalk, adjacent\nmicrorings are physically separated by etched trenches, as illustrated in Fig. 5(c). Since not all comblines require power\nequalization, we achieve uniform power distribution across all spectral lines using only 12 microrings. After the IWC, all 16\ncomblines are equalized to -18 dBm, accounting for an 8 dB insertion loss. The carriers are then amplified by an SOA and\nrouted through another IWC for odd-even channel separation. Separated carriers are modulated by 35-GHz-bandwidth IQ\nmodulators, combined, and then amplified through an SOA before transmission. As demonstrated in Fig. 5(e), a 10-km\ntransmission at 5.12 Tbps (net 5.015 Tbps) is achieved using 40-GBaud DP-16QAM modulation. The BER trend per channel\naligns consistently with the linewidth values as shown in Fig. 5(d), with comblines below 300 Hz linewidth achieving error-\nfree operation.\nIt is noteworthy that the capacity of the present chip-level transmitter is lower than that of systems based on bulky devices.\nThis primarily stems from carrier performance degradation caused by integrated components, which featuring higher noise\nfigures and insertion losses than their benchtop counterparts. Specifically, the IWC contributes an additional 3 dB insertion\nloss compared to benchtop WSS. SOAs, while far more compact than EDFAs, introduce excessive amplified spontaneous\nemission (ASE) noise. Meanwhile, their high α-factor and nonlinear effects (notably XPM) further induce cumulative phase\nnoise and waveform distortion in high-speed systems46,47. Figure 5(f) and (g) present the corresponding noise and OSNR\ndegradation after amplification. When amplified to 10 dBm, the linewidth of channel 6 increases of approximately threefold\nand tenfold via EDFA and SOA respectively. In addition, the OCNR decreases by 6 dB and 12.5 dB respectively. Despite these\nimpairments, the SIL light source still enables >5 Tbps transmission within the chip-level lightweight system, due to its\noriginal superior coherence and OCNR. For comparation, we implement a reference system using a 45-GHz-spacing electro-\noptic frequency comb pumped by an N7714A ECL (Fig. 5(d)). Under identical conditions, severely degraded constellation\ndiagrams are obtained due to its poor original coherence (Fig. 5(e) black pentagrams).\n\"(b) Furthermore, the use of EDFAs and WSSs may negate the noise benefits of SIL combs. How does ASE noise impact OCNR,\nlinewidth, and BER? Is the performance comparable or inferior to simpler pump-plus-filter approaches? This trade-off needs\nclarification.\"\nOur reply: The reviewer's concerns are justified, and we carefully evaluate this. The ASE noise from optical amplifiers (EDFA\nor SOA) and the insertion loss of spectral shapers (WSS or IWC) will inevitably affect OCNR. The insertion loss of WSS (IWC)\nis approximately 5 dB (8 dB), and the OCNR degradation caused by EDFA (SOA) has been shown in Fig. 5(g). When the\ncombline power is -10 dBm (OCNR=48), the insertion loss of WSS (IWC) will reduce the OCNR to 43 dB (40 dB). After\namplification by EDFA (SOA), the OSNR will decrease by 6 dB (10 dB).\nMoreover, the amplifiers' inherent linewidth enhancement will broaden the linewidth. Figure 5(f) shows the test results:\nSOA exhibits higher noise degradation than EDFA, increasing the 170 Hz linewidth by approximately threefold and tenfold,\nrespectively. The measurements in Fig. 2(e) demonstrate that lower OCNR and broader linewidth will affect the maximum\ntransmission rate, and the same applies to BER.\n(Result, page 18) Figure 5(f) and (g) present the corresponding noise and OSNR degradation after amplification. When\namplified to 10 dBm, the linewidth of channel 6 increases of approximately threefold and tenfold via EDFA and SOA\nrespectively. In addition, the OCNR decreases by 6 dB and 12.5 dB respectively.\nWe infer that the mentioned “pump-plus-filter” approach refers to the conventional microcomb generation approach,\nwhere the pump laser is amplified and ASE noise is suppressed with a narrow bandpass filter. However, this configuration\nrequires a complex tuning process with precise alignment between the pump frequency and the resonator peak, and the\ncoherence of the generated comblines is ultimately limited by the pump laser. Pump lasers that simultaneously offer high\npower and narrow linewidth are costly and challenging to integrate. In contrast, the SIL scheme, achieved via hybrid\nintegration, is inherently more suitable for lightweight transmission. Additionally, benefiting from linewidth narrowing\nenabled by the high-Q microresonator, we can achieve comblines with sub-1 kHz linewidth.\n\"(c) While a 61.5% conversion efficiency for 15 lines is reported, power distribution is uneven. Spectral flattening for power\nequalization introduces additional insertion loss. The authors should recalculate an \"effective\" conversion efficiency\nconsidering usable lines post-equalization.\"\nOur reply: We sincerely appreciate the reviewer's insightful comments. As noted, conversion efficiency can be defined in\nmultiple ways. In the main text, we give the conversion efficiency as the ratio between the total power of the 15 generated\ncomblines to the pump laser power. We understand the reviewer’s concern, since practical transmission systems require\nconsistent power levels across channels. Considering the 18 dBm LD power is converted to 16 >-10 dBm carriers, the\n“effective” conversion efficiency can be calculated as 16*10-1/101.8=2.5%. After including the additional insertion loss of\nthe WSS (IWC), the post-equalization conversion efficiency falls to 0.8% (0.4%).\nFollowing the wall-plug efficiency definition, we also provide the electro-optic conversion efficiency, which accounts for the\ngenerated optical power relative to the electrical power driving the optical sources. Considering the electrical consumption\nof 0.469 W (0.3 A×1.564 V) for the laser diode, 0.587 W (0.38 A×1.545 V) for the SOA and the output optical power of\n0.031 W (15 dBm), the overall electric-optic conversion efficiency is ~3.0%. This is lower than typical wall-plug efficiency\n(9%~16%) of DFB laser diodes. However, we emphasize that the strength of microcomb sources lies in their parallel\ntransmission capability, which fundamentally distinguishes them from laser arrays. In WDM systems, the wavelengths of\nindividual laser diodes must be carefully controlled, requiring multiple controllers and added power consumption. In\ncontrast, the optical frequency comb provides intrinsically stable channel spacing, since the microcomb is mode-locked.\nThis property dramatically reduces system complexity: in our demonstrated system, only two temperature controllers are\nrequired, whereas a 16-channel laser array would require 16 independent controllers.\nThe reviewer may concern that the post-equalization conversion efficiency is comparable to the other types of mode-locked\nmicrocombs, bright soliton microcombs, which feature flatter spectra. However, even in those cases, the central combline\npowers are not perfectly uniform. For example, combline power variations of ~4 dB and ~10 dB among the central 16 lines\nwere observed in [Science 373, 99–103 (2021)] and [Nature Photonics 18, 294–299 (2024)], which also necessitate power\nequalization. Soliton crystal-based optical frequency combs, despite achieving conversion efficiencies >40%, suffer from\nspectral non-uniformity that necessitates equalization exceeding 20 dB for individual comblines [Nat Commun 11, 2568\n(2020)].\n(Supplementary Note 1) In the main text, we give the conversion efficiency as the ratio between the total power of the 15\ngenerated comblines to the pump laser power. Considering the 18 dBm LD power is converted to 16 >-10 dBm carriers, the\n“effective” conversion efficiency can be calculated as 16*10-1/101.8=2.5%. After including the additional insertion loss of\nthe WSS (IWC), the post-equalization conversion efficiency falls to 0.8% (0.4%).\nFollowing the wall-plug efficiency definition, we also provide the electro-optic conversion efficiency, which accounts for the\ngenerated optical power relative to the electrical power driving the optical sources. Considering the electric consumption\nof 0.469 W (0.3 A×1.564 V) for the laser diode, 0.587 W (0.38 A×1.545 V) for the SOA and the output optical power of 0.031\nW (15 dBm), the overall electric-optic conversion efficiency is ~3.0%. This is lower than the typical wall-plug efficiency\n(9%~16%) of DFB laser diodes, but unlike DFB arrays, it requires no individual LD or TEC control for each laser unit.\nComment 3: \"The manuscript mentions injection-locked amplification as a future improvement but this contradicts earlier\nclaims that such techniques are less suitable for lightweight systems. Furthermore, prior work (e.g., Ref. [22]) has already\ndemonstrated injection-locked amplification of SIL microcombs with comparable or better performance. The authors should\nre-evaluate their novelty claim and clarify the meaningful differences of their implementation compared to these prior\nstudies.\"\nOur reply: We sincerely appreciate the reviewer's rigorous scientific attitude. Relatively low combline power is a significant\nconstraint of microcombs in high capacity transmission. Ref. 22 presents a feasible solution. However, the proposed SIL-\nplus-IL (injection locking) scheme relies on multiple laser diodes along with controllers for temperature and other\nparameters, leading to high power consumption and large volume, contrary to the goals of a lightweight system. In contrast,\nthe revised manuscript presents a much more practical solution for lightweight transmission, employing four types of\nintegrated chips: a laser diode, a SiN microresonator, a silicon photonic waveshaper, and a III–V semiconductor amplifier.\nAll components are chip-level and commercially available, enabling a system with high integration, low power consumption,\nand significantly reduced cost.\nWe also note that integrated rare-earth-doped optical amplifiers with high output power (W-level) and low noise figures\n(<5 dB) have already been demonstrated, and their combination with microcombs has been experimentally validated in\ntransmission links. Such high-performance amplifiers are highly promising for compensating the low combline power and\nfurther strengthening the practicality of microcomb-based lightweight systems.\n(Discussion, page 21) Additionally, despite high conversion efficiency, the comb power is still constrained by the limited\npump power, making it challenging to adopt higher-order modulation formats, which can be mitigated by further\noptimization in coupling loss36,37 and integrated optical amplifier with high output power and low noise figure50.\nComment 4: \"Minor issues and editorial errors:\n(a) Line 202: \"gray dots\" should be \"purple dots\".\n(b) Supplementary Note 4, line 65: \"Fig.1(e)\" reference is unclear.\"\nOur reply: We are grateful for the reviewer's meticulous evaluation and have thoroughly addressed all raised concerns\nthrough comprehensive revisions in our updated submission.\n(Results, page 12) Compared with a high-performance tunable ECL1 with a ~10 kHz linewidth (gray dots), the self-injection\nlocking scheme (gray dots purple dots) exhibits a 3 dB lower OSNR requirement at the same EVM level due to the parallel\nhigh coherence.\n(Supplementary Note 4) The local oscillator at the receiver is of the same model as the ECL1 laser shown in Fig. 1(e).\nKEYSIGHT N7714A ECL.\nThanks again for the valuable comments and helpful suggestions."}, {"round": 2, "reviewer_comments": {"reviewer_1": "I would like to acknowledge the authors for addressing my comments in a careful and thorough manner. The additions to the text are reasonable and fairly convincing. I would be happy to see this paper published after these requests and other reviewer comments are fully addressed.\n\n1. In rebuttal comment 2: The authors state a simulated transmission; however, I believe they show an experimental result.\nPlease clarify if these 1 Tbps results are experimental or simulation.\n\n2. Please specify in text what FEC each raw (net) transmission result is using as some plots use the 7% HD-FEC, while other use a 9.1% overhead\n\n3. In rebuttal comment 4: The authors show a on-chip size comparison for multiple components; however, they still emulate a real system by using an even/odd modulation scheme which only requires 2 DP-IQMs. It would be more useful to know the size and performance of the full system using on chip MUX/DEMUX pairs and individual modulators instead of an IWC.", "reviewer_2": "The reviewed manuscript now adds additional experimental data: impact of linewidth and OCNR, the BER achieved with all the comb lines and comparison with ECL, and data transmission replacing EDFA and AWG by SOA and IWC, respectively. These experiments and the associated data clarify some of the concerns raised from the prior manuscript. In addition, the authors have increased the details of their experimental investigations with the added Methods and Supplementary information. I believe the paper contains enough results, however, it does have some issues associated mostly with the new extensive new content.\n\n- The paper includes multiple experiments with different settings, e.g., 70 GBd or 110 GBd, ECL or comb lines or a single line, SOA or EDFAs, and so on. The authors did include two setups in the supplementary document, however it is still not clear if, e.g., the same LO and receiver configuration is used. If so, do the authors observe or expect to observe penalties due to the 10 kHz linewidth of the LO? (I short sentence here would suffice)\n\n- The authors use 2 SOAs. They mention the output power of the first one (10 dBm) but that of the second one is missing.\n\n- The authors continuously refer to OCNR and OSNR values. How are these quantities measured? Are the authors using the optical spectrum analyzer? If so, which resolution bandwidth the consider? Importantly, where are they measured? I believe the authors should clearly indicate everytime where the OCNR and OSNRs are measured. I believe the authors should clearly indicate everytime where the OCNR and OSNRs are measured.\n\n- If the authors consider a resolution bandwidth of 12.5 GHz, I can’t understand how they measured an OSNR of 40 dB (Fig. 5g) if the power of the comb line before the first SOA is already -18 dBm. I would expect a much lower OSNR if that is measured after the second SOA. The authors should clarify this as it questions the validity of this analysis.\n\nAdditional suggestions:\n- The manuscript seems to have lost the well organized structure from the first version. The authors may want to revise the content for smooth reading and clear transitions between experiments.\n\n- In addition, there quite some grammatical error, e.g., lines 213-215 have some of them. The authors may want to also revise this thoroughly.", "reviewer_3": "The authors have made significant improvements to the manuscript, particularly by providing a more compact DFB-laser pumping scheme for the frequency comb. This alternative is a valuable addition. However, it is also clear that this new scheme comes at the cost of substantially worse performance parameters compared to the original EDFA-based approach. While this trade-off between compactness and performance is an important discussion point, the manuscript has been improved enough through the added comparisons to be acceptable for publication. I recommend acceptance."}, "author_response": "Manuscript ID: NCOMMS-25-24030A-Z\nTitle: Exploiting a Centrally Powered Coherent Microcomb for Lightweight Optical Transmission\nAuthor: Junhao Han, Guofeng Yan, Kang Li, Bitao Shen, Haowen Shu, Yimeng Wang, Yuchen Zhang,\nJiong Xiao, Yichen Wu, Huajin Chang, Chengkun Cai, Xuguang Zhang, Xingjun Wang, and Jian Wang\nDear Editor and Reviewers of Nature Communications,\nWe sincerely appreciate the careful review by the reviewers and have modified the manuscript in\naccordance with their suggestions. Here, we present a point-by-point reply (in blue) to the reviewers'\ncomments (in black). All the changes have been highlighted (in red) with corresponding original text\nprovided for comparison (in orange).\nResponse to the report from the Referee #1\nGeneral comments: \"I would like to acknowledge the authors for addressing my comments in a careful and thorough\nmanner. The additions to the text are reasonable and fairly convincing. I would be happy to see this paper published after\nthese requests and other reviewer comments are fully addressed.\"\nOur reply: We sincerely appreciate the reviewer's favorable comments and the considerable time and effort dedicated to\nevaluating our work. In the revised manuscript, we have incorporated a more detailed description and refined the analysis\nof the system footprint. Please find our point-by-point response attached.\nComment 1: \"In rebuttal comment 2: The authors state a simulated transmission; however, I believe they show an\nexperimental result. Please clarify if these 1 Tbps results are experimental or simulation.\"\nOur reply: We sincerely thank you for this comment. We would like to clarify that our results are based on experimental\ndemonstrations, not simulations. Corresponding clarifications have been added to the manuscript.\n(Introduction, page 6 line 111) We simulated experimentally demonstrated short-reach campus/edge networks and\nmetropolitan area network transmission separately. In the campus/edge networks, we achieved a transmission capacity of\nComment 2: \"Please specify in text what FEC each raw (net) transmission result is using as some plots use the 7% HD-FEC,\nwhile other use a 9.1% overhead. \"\nOur reply: We sincerely thank the reviewer for this valuable feedback. We have now provided clarification regarding all FEC\noverheads mentioned in the manuscript.\n(Results, page 12, line 218-219) Thanks to the high OCNR with power levels above -10 dBm, all channels can support 110\nGBaud DP-32QAM signal transmissions in the WDM configuration, indicating a single-channel rate of 1.1 (net 1.008) Tbps\nbelow the 9.1% forward error correction (FEC) threshold with a BER of 7×10⁻³.\n(Results, page 12, line 231-232) Overall, this 16-channel WDM scheme achieves a raw (net) aggregated rate of 8.96 (8.37)\nTbps below the 7% HD (hard decision)-FEC.\n(Results, page 15, line 278) In this case, we achieve a raw (net) transmission rate of 215.04 (200.97) Tbps below the 7% HD-\nFEC BER threshold by loading 70 Gbaud DP-16QAM signals, with only 16 wavelength channels, as shown in Fig. 4(c).\n(Results, page 18, line 334) As demonstrated in Fig. 5(e), a 10-km transmission at 5.12 Tbps (net 5.015 Tbps, 5 channels\nunder 7% HD-FEC threshold condition) is achieved using 40-GBaud DP-16QAM signals.\n(Results, Fig. 4, line 312) (f) LP and OAM MDM transmission under 7% HD-FEC threshold.\nComment 3: \" In rebuttal comment 4: The authors show a on-chip size comparison for multiple components; however, they\nstill emulate a real system by using an even/odd modulation scheme which only requires 2 DP-IQMs. It would be more useful\nto know the size and performance of the full system using on chip MUX/DEMUX pairs and individual modulators instead of\nan IWC.\"\nOur reply: We are grateful to the reviewer for their valuable comments. We acknowledge the necessity of employing\nindependent modulators for each wavelength channel in a practical deployment scenario, which underscores the\nimportance of a more comprehensive statistical evaluation. In response, we have updated the relevant table and provided\na detailed explanation in the manuscript to enhance the robustness of our discussion.\nComponent Number Volume (cm*cm*cm)\nSIL Comb 1 2.8*1.2*1\nEDFA 2 32*25*10\nWSS 1 31*24*12\nDP-IQM 16 8.8*1.4*1\n2x1 Optical Coupler 1 0.7*5*0.4 0.3*6*0.3\nIn a practical deployment scenario using commercially available EDFAs and WSSs, the overall footprint is 2546 cm² with a\nheight of 12 cm. By adopting a more lightweight SOA system and on-chip DEMUX/MUX components, the overall required\nfootprint is further reduced to 208 cm² with a height of 1 cm. This results in a volume reduction by a factor of approximately\n150 (2546*12/208/1 = 147). Furthermore, the use of on-chip IQ modulators holds the promise of achieving a volume\nreduction of more than a thousandfold [Nature Communications 15, 7892 (2024)].\nComponent Number Volume (cm*cm*cm)\nSIL Comb 1 2.8*1.2*1\nSOA 2 3*1.27*1\nAWG (DEMUX/MUX)\n[IEEE Photonics Technology Letters, 2 ~0.11*0.07\n35(7), 369-372, 2023]\nDP-IQM 16 8.8*1.4*1\n(SI, Supplementary Note 7) We present the volume and quantity of all components in the transmitter. For our long-haul,\nhigh-speed demonstration, the transmitter assembly features a footprint of 2374 cm² and a height of 12 cm. In the more\nlightweight transmitter demonstration, our system occupies an area of 89 cm² with a height of 3 cm. This results in a volume\nreduction of more than a hundred-fold (2374*12/89/3 = 106).\nIt is noteworthy that in our experiment, two DP-IQ modulators were used to separate the odd and even channels to simulate\na real world transmission system. In an actual communication node deployment, each carrier channel requires an individual\nmodulator for signal loading. Consequently, we have re-evaluated the size here in table S5. In a practical deployment\nscenario using commercially available EDFAs and WSSs, the overall footprint is 2546 cm² with a height of 12 cm. By adopting\na more lightweight SOA system and on-chip DEMUX/MUX components1, the overall required footprint is further reduced\nto 208 cm² with a height of 1 cm. This results in a volume reduction by a factor of approximately 150 (2546*12/208/1 = 147). Furthermore, the use of on-chip IQ modulators holds the promise of achieving a volume reduction of more than a\nthousand-fold.\nTable S4. Experimental system component sizes.\nEDFA-WSS-based\nComponent Number Volume (cm*cm*cm)\nSIL Comb 1 2.8*1.2*1\nEDFA 2 32*25*10\nWSS 1 31*24*12\nDP-IQM 2 8.8*1.4*1\n2x1 Optical Coupler 1 0.3*6*0.3\nSOA-IWC-based\nComponent Number Volume (cm*cm*cm)\nSIL Comb 1 2.8*1.2*1\nSOA 2 3*1.27*1\nIWC 2 5.2*4.8*3\nDP-IQM 2 8.8*1.4*1\n2x1 Optical Coupler 1 0.3*6*0.3\nTable S5. Real deployment system component sizes.\nEDFA-WSS-based\nComponent Number Volume (cm*cm*cm)\nSIL Comb 1 2.8*1.2*1\nEDFA 2 32*25*10\nWSS 1 31*24*12\nDP-IQM 16 8.8*1.4*1\n16x1 Optical Coupler 1 0.7*5*0.4\nSOA-AWG-based\nComponent Number Volume (cm*cm*cm)\nSIL Comb 1 2.8*1.2*1\nSOA 2 3*1.27*1\nAWG (DEMUX/MUX) 2 ~0.11*0.07\nDP-IQM 16 8.8*1.4*1\nIn summary, we thank the reviewers for the thorough review, which has been invaluable in strengthening our paper. We\nhave carefully revised the manuscript.\nResponse to the report from the Referee #2\nGeneral comments: \"The reviewed manuscript now adds additional experimental data: impact of linewidth and OCNR, the\nBER achieved with all the comb lines and comparison with ECL, and data transmission replacing EDFA and AWG by SOA and\nIWC, respectively. These experiments and the associated data clarify some of the concerns raised from the prior manuscript.\nIn addition, the authors have increased the details of their experimental investigations with the added Methods and\nSupplementary information. I believe the paper contains enough results, however, it does have some issues associated\nmostly with the new extensive new content.\"\nOur reply: We sincerely appreciate the reviewer's meticulous review and rigorous assessment. We have provided further\nelaboration and refinements to the newly added experimental content. Please find our point-by-point response attached.\nComment 1: \"The paper includes multiple experiments with different settings, e.g., 70 GBd or 110 GBd, ECL or comb lines\nor a single line, SOA or EDFAs, and so on. The authors did include two setups in the supplementary document, however it is\nstill not clear if, e.g., the same LO and receiver configuration is used. If so, do the authors observe or expect to observe\npenalties due to the 10 kHz linewidth of the LO? (I short sentence here would suffice)\"\nOur reply: We thank the reviewer for their careful review of our manuscript. We apologize for the lack of clarity. However,\nto clarify, the local oscillator and receiver configuration were identical across both experimental architectures. We did not\nconduct experimental validation regarding the impact of LO laser linewidth. However, based on established understanding,\nwe believe that an increase in LO linewidth would primarily place a greater computational burden on the DSP and\nconsequently degrade the BER [Journal of Lightwave Technology, 38(6), 1138-1147 (2020)]. However, since the LO does\nnot traverse the transmission channel, its impact is relatively \"pure\" and direct compared to the transmitter laser.\nSwitching to an LO with a better linewidth would certainly achieve better transmission performance. In practical\ndeployment, it may lower the economic benefit.\n(SI, Supplementary Note 4) After generating the frequency comb, it is split into odd and even channels and decorrelated.\nEach channel undergoes I/Q modulation, and the signals are then coupled and transmitted through the fiber. The local\noscillator at the receiver in both the EDFA-based and the SOA-based configurations is the KEYSIGHT N7714A ECL.\nComment 2: \"The authors use 2 SOAs. They mention the output power of the first one (10 dBm) but that of the second one\nis missing.\"\nOur reply: We are grateful to the reviewer for this comment. In our setup, the first SOA initially delivers an output power\nof 18 dBm. This signal subsequently experiences an 8 dB attenuation from the IWC, entering the modulators at 10 dBm.\nThe modulators then introduce an inherent 20 dB insertion loss. After the signals are combined, they are finally amplified\nby a subsequent SOA to 2 dBm for transmission. This has been addressed by adding a clearer description in the manuscript.\n(Results, page 18, line 327-333) After the IWC, all 16 comb lines are equalized to -18 dBm per carrier, accounting for an 8\ndB insertion loss. All carriers are then amplified by an SOA to a total output power of 18 dBm and routed through another\nIWC for odd-even channel separation. The separated carriers are modulated by 35-GHz-bandwidth DP-IQ modulators\n(which introduce 20 dB of insertion loss), combined, and then amplified by an SOA to an output power of 2 dBm before\ntransmission.\nComment 3: \"The authors continuously refer to OCNR and OSNR values. How are these quantities measured? Are the\nauthors using the optical spectrum analyzer? If so, which resolution bandwidth the consider? Importantly, where are they\nmeasured? I believe the authors should clearly indicate everytime where the OCNR and OSNRs are measured. I believe the\nauthors should clearly indicate everytime where the OCNR and OSNRs are measured.\nIf the authors consider a resolution bandwidth of 12.5 GHz, I can’t understand how they measured an OSNR of 40 dB (Fig.\n5g) if the power of the comb line before the first SOA is already -18 dBm. I would expect a much lower OSNR if that is\nmeasured after the second SOA. The authors should clarify this as it questions the validity of this analysis.\"\nOur reply: We sincerely thank the reviewer for pointing out the lack of clarity in our experimental description. We have\nrevised the corresponding section to provide a more explicit explanation and have supplemented it with additional\nexperimental data to resolve the ambiguity.\n\"The authors continuously refer to OCNR and OSNR values. How are these quantities measured? Are the authors using the\noptical spectrum analyzer? If so, which resolution bandwidth the consider? \"\n We confirm that both the OCNR and OSNR were indeed measured using an optical spectrum analyzer (OSA), with the\nresolution bandwidth set to 6.25 GHz. The measurement method is primarily determined by the power ratio (in dB)\nbetween the peak of the optical carrier and the ASE noise floor.\n(Materials and Methods, page 27, line 504-506) It must be emphasized that all OCNR measurements were performed with\nthe optical spectrum analyzer's resolution bandwidth set to 6.25 GHz.\n\"Importantly, where are they measured? I believe the authors should clearly indicate everytime where the OCNR and OSNRs\nare measured. \"\n The measurement location has been explicitly specified at all points where OCNR and OSNR data is presented.\n(Results, Fig. 2) (e) The influence of OCNR and linewidth on the maximum net symbol rate is evaluated under the error-free\ncondition in single carrier condition. This OCNR is measured at the output of the first-stage EDFA and is primarily\ndetermined by the intrinsic property of the optical source itself.\n(Results, Fig. 3) (f) OSNR penalty process. The OSNR measurement is performed after the first EDFA at the receiver. The left\nand right panels show BTB and 160-km transmission, respectively.\n(Results, page 19, line 349-353) After two SOAs, IWC and modulators, the OCNR decreases by 13 dB at the 2 dBm output\noperating point, as shown in Fig. 5(g). We find that when the input optical carrier has an OCNR < 25 dB, the ASE noise from\nthe dual SOAs completely overwhelms the carrier, rendering it incapable of supporting signal transmission.\n(Results, Fig. 5) (g) OCNR-OSNR degradation induced by two SOAs or EDFAs at 2dBm output power.\n\"If the authors consider a resolution bandwidth of 12.5 GHz, I can’t understand how they measured an OSNR of 40 dB (Fig.\n5g) if the power of the comb line before the first SOA is already -18 dBm. I would expect a much lower OSNR if that is\nmeasured after the second SOA. The authors should clarify this as it questions the validity of this analysis. \"\n We are grateful to the reviewer for their meticulous attention to detail in identifying this discrepancy. The original\nfigure 5g was measured after the first stage amplification using a single wavelength laser as the input, and was\npresented to qualitatively explain the OCNR degradation during the amplification process. Additionally, the vertical\naxis in the initial version of Fig. 5g, labeled as OSNR, may be misleading. As the measurement was taken after\namplification by a single SOA and without any signal transmission, it actually shows the OCNR variation. The label has\nbeen corrected accordingly. To address the reviewer’s concern, we have supplemented the analysis with an\ninvestigation of the OCNR to the exact OSNR degradation under WDM conditions, following the signal path through\ntwo SOAs, an IWC and a modulator, which is same as the one in data transmission experiment.\n(g)OCNR-OSNR degradation induced by two SOAs (EDFAs) at 2dBm output power.\nWe have re-measured the OCNR variation under the experimental conditions. With an input power of -18 dBm\n(corresponding to an OCNR of 42 dB), the final achieved OSNR was only 29 dB. To better elucidate the system's\noperating point, we have created a schematic diagram to show the power budget at each connection points.\nFig. Operating point optical power\nMeanwhile, we put the original Fig. 5g into the updated version in the SI, with corrected labels.\n(SI, Supplementary Note 6) We present the degradation of the input OCNR by a single SOA at an output power of 10 dBm\nusing a single wavelength laser, which is caused by the introduction of ASE noise. In comparison, EDFAs introduce lower\nASE noise, which results in a 4 dB higher final OCNR output. Additionally, EDFAs offer superior linearity, broader span range,\nhigher saturation power, and lower input power requirements.\nFig. S6 OCNR degradation. The blue curve represents the EDFA, and the red curve represents the SOA, both at an output\npower of 10 dBm. The EDFA shows a degradation of approximately 6 dB, while the SOA exhibits about 10 dB.\nComment 4: \"The manuscript seems to have lost the well organized structure from the first version. The authors may want\nto revise the content for smooth reading and clear transitions between experiments.\"\nOur reply: We sincerely thank the reviewers for their valuable suggestions. We have added more transitional sentences to\nmake the logical connections between experiments smoother and more coherent.\n(Introduction, page 5, line 98-99) Such a source is essential to maximize single-channel capacity, enable multi-dimensional\nmultiplexing for even higher aggregate rates, and tolerate the performance degradation inherent in lightweight systems.\n(Introduction, page 5, line 105-108) To establish an overarching framework for our study, we perform a detailed\ninvestigation of the constraints among OCNR, linewidth, and achievable transmission rate.\n(Introduction, page 6, line 122) Finally, for more compact deployment scenarios, a chip-level multicarrier generator is\ndemonstrated, replacing bulky erbium-doped fiber amplifiers (EDFAs) and wavelength-selective switches (WSS) with\nintegrated semiconductor optical amplifiers and silicon photonic waveshapers.\n(Results, page 18, line 314-316) Under stringent cost and footprint constraints, bulky equipment impedes system\nintegration, particularly for achieving lightweight transmission in distributed edge nodes.\nComment 5: \"In addition, there quite some grammatical error, e.g., lines 213-215 have some of them. The authors may\nwant to also revise this thoroughly.\"\nOur reply: We sincerely thank the reviewer for this reminder. We have thoroughly re-examined the entire manuscript and\nmade corrections to grammatical and spelling errors throughout the text.\n(Introduction, page 3, line 62) Despite the achievement of ultra-high capacity integrated parallel transmission systems,\nconventional schemes still struggle to deliver the required data throughput while maintaining compact structure and\nenergy efficient efficiency in space-limited and power-constrained scenarios.\n(Introduction, page 5, line 101-102) The highly integrated source provides both high coherence with approximately 40 dB\nfrequency noise suppression and high pre-channel per-channel power with >60% on-chip conversion efficiency.\n(Results, page 8, line 142-143) To fulfill the demand for a compact, highly coherent source, the SIL microcomb scheme is\nimplemented for frequency noise compression and carrier-to-noise enhancement in this work, as shown in Fig. 2(b).\n(Results, page 11, line 214) Limited by the channel spacing of 100 GHz, we artificially doubled the spectral interval through\nWSS, as shown in Fig. 3(b), and distinguish the channels by their transparency.\n(Results, page 11, line 216) Thanks to the high OCNR with power levels above -10 dBm, all channels can support 110 GBaud\nDP-32QAM signal transmissions in the WDM configuration, indicating a single-channel rate of 1.1 (net 1.008) Tbps below\nthe 9.1% FEC (forward error correction) threshold with a BER of 7×10⁻³.\n(Results, page 12, line 226-229) DP-16QAM signals are then modulated onto the parallel carriers, which are subsequently\ncombined and transmitted through a 160-km standard single mode fiber (SMF). At the receiver end, the LO source and\ntransmitted comblines are detected and mixed by a coherent receiver.\n(Results, page 15, line 282-285) Besides, we show the first proof-of-concept mode-division multiplexed (MDM) multi-\ndimensional transmissions includes LP modes in a few-mode fiber (FMF) and OAM modes in a ring-core fiber (RCF) driven\nby the integrated photonic light source.\n(Results, page 19, line 340) This primarily stems from carrier performance degradation caused by integrated components,\nwhich feature higher noise figures and insertion losses than their benchtop counterparts.\n(Results, page 19, line 346-348) Figure 5(f) presents the corresponding noise degradation after an SOA amplification. When\namplified to 10 dBm, the linewidth of channel 6 increases of by approximately threefold and tenfold via EDFA and SOA\nrespectively.\n(Results, page 19, line 355) For comparation comparison, we implement a reference system using a 45-GHz-spacing electro-\noptic frequency comb pumped by an N7714A ECL (Fig. 5(d)).\n(Discussion, page 22, line 398) Despite Although the total capacity is below the petabit-per-second scale compared to state-\nof-the-art demonstrations, a higher channel capacity and streamlined nature of this architecture would significantly reduce\nthe footprint and overhead associated with channel scaling, making it well-suited for compact edge infrastructure.\n(Materials and Methods, page 27, line 501) along with two cases that failed demodulation - an InP DFB laser (3 MHz)\nResponse to the report from the Referee #3\nGeneral comments: \" The authors have made significant improvements to the manuscript, particularly by providing a more\ncompact DFB-laser pumping scheme for the frequency comb. This alternative is a valuable addition. However, it is also clear\nthat this new scheme comes at the cost of substantially worse performance parameters compared to the original EDFA-\nbased approach. While this trade-off between compactness and performance is an important discussion point, the\nmanuscript has been improved enough through the added comparisons to be acceptable for publication. I recommend\nacceptance.\"\nOur reply: We thank the reviewer for carefully reviewing our manuscript and for providing valuable comments\nThanks again for the valuable comments and helpful suggestions."}]

Decision letter