# Integrated Components and Solutions for High-Speed Short-Reach Data Transmission
## 2 Transmitter for Short-Reach Transmission Systems
### Monolithic Integrated Transmitter  
Compared with other discrete transmitter components, a monolithic integrated transmitter with the characteristics of lower power consumption, smaller size, lower cost, and higher reliability has shown great potential in short-reach even in metro transmission systems. Currently, mainstream monolithic integration technologies can be divided into two categories, including InP-based monolithic integration and silicon photonics (SiP). In addition, the use of InP-based monolithic integration transmitter has been widely explored to achieve high-speed and power-efficient signal transmission. For example, [PERSON] et al. firstly reported a record 3-dB bandwidth up to 54-GHz InP-based DFB-MZM transmitter [15], and this was demonstrated in the 100-Gbit/s NRZ, 200-Gbit/s PAM-4 and 300-Gbit/s PAM-8 transmission systems with 1-kilometer distance. In addition, [PERSON] et al. presented 333-Gbit/s DMT transmission enabled by an 80-GHz C-band InP-based MZM over 20-km dispersion-compensated link [16]. Another attractive candidate, SiP, has the advantages of compatibility with complementary metal-oxide-semiconductor (CMOS) technology with small size and low loss, although many have questioned the intrinsic bottlenecks of the platform regarding modulator bandwidth at present. Several high-speed SiP transmitters have been reported for beyond 100-Gbit/s optical interconnects [15; 16; 79; 80; 81; 82; 83; 84; 85; 86; 87; 88; 89; 90; 91]. [PERSON] et al. experimentally achieved single lane 112-Gbit/s PAM-4 transmission over 1-km, 2-km, and 10-km SMF links based on 3-dB electro-optical bandwidth of beyond 50-GHz silicon MZM [79]. Furthermore, based on SiP-based DD \begin{table}
\begin{tabular}{c c c c c c c c c} \hline
**Tx** & **\(\boldsymbol{\lambda}\)** & **MF** & **BW** & **Rate** & **Reach** & **Fiber** & **FEC** & **Limit** & **Ref.** \\
**Device** & **(nm)** & **MF** & **(GHz)** & **(Gbit/s)** & **(km)** & **Type** & **Limit** & **Ref.** \\ \hline EML & 1298.5 & PAM-4 & 18 & 100 & 80 & SMF & \(3.8\times 10^{-3}\) & [68] \\ AXEL & \textasci{}1307 & PAM-4 & 35 & 106 & 60 & SMF & \(2\times 10^{-4}\) & [69] \\ EML & 1294.72 & PAM-4 & 20 & 112 & 40 & SMF & \(3.8\times 10^{-3}\) & [70] \\ EML & 1293 & PAM-4 & 25 & 112 & 40 & SMF & \(3.5\times 10^{-6}\) & [71] \\ EML & 1304 & PAM-4 & 17 & 112 & 40 & SMF & \(3.8\times 10^{-3}\) & [72] \\ DS-EML & 1538.74 & PAM-8 & 40 & 129 & 5 & SMF & \(3.8\times 10^{-3}\) & [73] \\ EML & 1310 & PAM-4 & 35 & 214 & 10 & SMF & \(2\times 10^{-4}\) & [74] \\ EML & 1550 & PS-PAM-8 & 40 & 260 & 1 & NZDSF & \(2\times 10^{-2}\) & [75] \\ DFB-TWEAM & 1550 & OOK & \textasci{}100 & 204 & 10 & SMF + DCF & \(1.1\times 10^{-2}\) & [76] \\ DFB-TWEAM & 1550 & PAM-4 & \textasci{}100 & 200 & 0.4 & SMF & \(2\times 10^{-2}\) & [77] \\ DFB-TWEAM & 1550 & DMT & \textasci{}100 & 200 & 1.6 & SMF & \(2.7\times 10^{-2}\) & [78] \\ \hline \end{tabular}
\end{table} 
Table 4: Incomplete summary of EML applied in beyond 100-Gbit/s per lane data transmission. Figure 3: **(a)** Schema of DFB-TWEAM; **(b)** S\({}_{21}\) and S\({}_{11}\) characteristics of TWEAM; DFB: distributed feedback laser; TWEAM: traveling-wave electro-absorption modulators; QW: quantum wells; BCB: BenzoCycloButene layer; AC: alternating current; DC: direct current; (From [13], © 2009 IEEE). traveling-wave (TW) MZM, [PERSON] et al. demonstrated ultra-high-speed optical interconnects with single-lane bit rates of 176-Gbit/s PAM-4 [81] and 200-Gbit/s PAM-6 [82] for 1-km SMF transmission. Furthermore, this group further reported high baud-rate and long-haul transmission with SSB-PAM-N signal [83; 84]. To further generate high baud-rate PAM-4 signal in optical domain, multi-electrode MZM (ME-MZM) [85] has been studied and shown better transmission performance compared to a traditional single electrode TW-MZM [86] at O-band. In addition, [PERSON] et al.