Integrated gain-controlled semiconductor optical amplifier for input-power range extension in 100 Gb/s upstream PON receiver applications

High-speed operation for upstream passive optical network (PON) applications enabled by bias-controlled operation of silicon photonics integrated semiconductor optical amplifiers (SOA) is demonstrated in a continuous-mode back-to-back configuration. The InP-based C-band SOAs are heterogeneously integrated onto a 400 nm thick silicon waveguide using micro-transfer printing technology. Optimized apodized grating couplers are designed and incorporated to minimize fiber-to-chip coupling loss (2.5 dB). The integrated SOAs exhibit small-signal on-chip gains of 15-17 dB at a bias current of 120 mA. When the integrated SOA is employed as a receiver-side preamplifier in a 100 Gb/s four-level pulse-amplitude modulation (PAM-4) upstream PON application, bias optimization across received power levels extends the SOA operating input power range to 22 dB while mitigating pattern-dependent distortion arising from SOA gain saturation. A minimum SOA input power of -23 dBm is achieved at the hard-decision forward error-correction threshold, referenced to the on-chip SOA input and excluding input grating-coupler loss. These results demonstrate the potential of heterogeneously integrated, bias-controlled SOAs as compact preamplifiers for extending the operating input power range of next-generation high-speed upstream PON receivers.