# Beyond 100G: All-Optical Processor for High-Capacity Access\(\sim\)Networks
## 4 Simulation Setup  
In this section, we detail the simulation setup and performance evaluation for the 100G and 200G PON systems. Our objective is to utilize existing equipment compatible with the 50G standard or proposed 100G specifications and employ higher-order modulation schemes to significantly increase data rates. By using PAM4 instead of the conventional NRZ, we aim to achieve 100 Gbps and 200 Gbps, respectively. This approach leverages equipment intended for 50G or 100G PON to effectively double the transmission capacity, achieving 100G and 200G PON using 50G and 100G equipment, respectively. Higher-order modulation schemes like PAM4 offer increased spectral efficiency but introduce a sensitivity penalty due to their multiple levels and higher linearity requirements at the transmitter. For instance, transitioning from 25G NRZ to 50G PAM4 using the same receiver incurs a sensitivity penalty of 8-9 dB, typically preventing PAM4 from meeting the 29 dB power budget without digital signal processing (DSP) and/or receiver pre-amplification. These limitations necessitate advanced signal processing techniques, underscoring the necessity of the AOP. Figure 3: Operation of the AOP at state 1 and CDCF. Table 1 outlines the key simulation parameters used for both 100G PON and 200G PON systems. These parameters were selected to accurately model the performance of the PON systems under realistic operating conditions. In Figure 4, the system configuration illustrates a downstream link for a 100/200G PON operating in the O-band (1344 nm), designed to support 64 users within a radius of up to 20 km. The simulation setup and performance evaluation were conducted using VPItransmissionMaker(tm) 11.4 software. At the optical line terminal (OLT), the signal is modulated onto an optical carrier using an Electro-Absorption Modulator (EAM). The Tx 3 dB electro-optical bandwidths for the different scenarios are detailed in Table 1, achieved through a fourth-order Bessel electrical filter. This modulated signal is transmitted over a Standard Single-Mode Fiber (SSMF) span of up to 20 km, with a chromatic dispersion parameter of D = 2.44 ps/(km\(\cdot\)nm), to the optical network unit (ONU). At the ONU side, an avalanche photodiode (APD) with 0.8 responsivity, paired with a Transimpedance Amplifier (TIA) and a post-amplifier, effectively detects and amplifies the incoming optical signal. The receiver (Rx) 3 dB effective electro-optical bandwidths for the different scenarios are also detailed in Table 1, shaped by a fourth-order Bessel filter as well. To evaluate the performance of the AOP, an equalizer employing 21 symbol-spaced taps of Feed-Forward Equalization (21 FFE) and three taps of Decision Feedback Equalization (3 DFE) is used. The primary performance metric in this simulated environment is the bit error rate (BER) analysis, which assesses the effectiveness of the AOP in optimizing signal integrity. The tuning of the AOP's parameters is achieved using a machine-learning-driven Bayesian optimization decider. A probabilistic model is employed by Bayesian optimiza \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameters** & **50G PON** & **Proposed 100G** & **Simulated 100G** & **Simulated 200G** \\  & **Standard [(29)]** & **PON [(31)]** & **PON** & **PON** \\ \hline Tx Bandwidth & 22 GHz & 75 GHz & 22 GHz & 75 GHz \\ Tx Launch & 10 dBm & 10 dBm & 10 dBm & 10 dBm \\ Power, C+ & & & & \\ Wavelength & 1340–1344 nm & 1318-1322 nm & 1344 nm & 1344 nm \\ Rx Bandwidth & 30 GHz & 50 GHz & 30 GHz & 50 GHz \\ Rx ROP & \(-20.75\) dBm & \(-20.75\) dBm & \(-19\) dBm & \(-17\) dBm \\ Rx Responsivity & 0.8 A/W (APD) & 0.6 A/W (PIN) & 0.8 A/W (APD) & 0.8 A/W (APD) \\ Bit Rate & 50 Gbit/s & 100 Gbit/s & 100 Gbit/s & 200 Gbit/s \\ Modulation & & & & \\ Format & NRZ & NRZ & PAM4 & PAM4 \\ Reach & 20 km & 10 km & 20 km & 10 km \\ Equalization & 13 FFE & 21 FFE + 3 DFE & AOP (+ 5 FFE) & AOP (+ 5 FFE) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Parameters for 50, 100, and 200G PON.