Alternative to Super-PON downstream transmitter using a directly-modulated SOA

Super-PON is a 16-wavelength passive optical network with 50 km reach and 64 ONUs per λ , providing up to 10 Gb/s to sparsely populated areas. To bridge its challenging loss-budget, Super-PON includes an EDFA located next to the OLT, thus compromising transceiver integration and future spectral expansion. An alternative for downstream transmission consists in using a powerful directly-modulated semiconductor optical amplifier (SOA) and an avalanche photodiode. Here, we numerically demonstrate the technical feasibility of this proposal. By combining a sensitivity of − 24.9 dBm and an optimized SOA transmitter output of +19.4 dBm, error-free (BER ≤ 3.8x10 - 3 ) transmission is demonstrated. This achievement relies on the use of PAM-4 modulation to combat the limited opto-electronic bandwidth of the SOA, and Tomlinson-Harashima precoding (THP) to mitigate fiber transmission and receiver impairments. It is also shown that THP enhances the direct modulation capability of SOAs, leveraging their use in integrated transceivers aimed for high-loss photonic systems.