Polarization-Independent Coherent Real-Time Analog Receiver for PON Access Systems

A 1.25-Gb/s ASK passive optical network (PON) system with a -51 dBm pre-FEC sensitivity (at BER = 2 × 10
^-3
) is enabled by a real-time polarization-independent coherent receiver (PI-RX) that needs no DSP (nor ADC). The receiver, which only makes use of common DFBs and commercially available electronic ICs, is targeted for use on a 6.25-GHz UD-WDM grid and has a 52-dB dynamic range. Measurements of the robustness of the PI-RX against backreflections and crosstalk from coexistent adjacent channels show that this preliminary implementation is suitable for UD-WDM-PON systems with frequency spacing down to 5 GHz.