Fig. 1. Bidirectional subsystem using heterodyne detection sharing one laser at the ONU for UDWDM-PON using RSOA chip.

Fig. 2. Optical spectrum for 1.25 Gb/s/user DPSK–DPSK bidirectional UDWDM.

Fig. 3. Polarization-independent long-cavity RSOA chip at ONU.

Fig. 4. ASE spectrum at different bias condition.

Fig. 5. Frequency response as a function of the input powers of 0, −5, −10, −15, −20, and −25  dBm at the injected current of 140 mA for the RSOA chip.

Fig. 6. Polarization diversity heterodyne Rx.

Fig. 7. BER penalty against cut-off frequencies of the LPF (Rx input power at −50.6  dBm) and HPF (Rx input power at −47.5  dBm) at 1.25 Gb/s.

Fig. 8. BER penalty versus frequency offset between Tx and LO (Rx input power at −46.6 and −41.7  dBm for 1.25 and 2.5 Gb/s, respectively).

Fig. 9. BER against Rx power back-to-back and after 50 km at 1.25 and 2.5 Gb/s (DFB as transmitter at the ONU, and ECL as the LO at the OLT) together with 2 DFBs at 1.25 Gb/s.

Fig. 10. BER versus Rx power using RSOA chip compared with To-can RSOA (back-to-back, 25°C), and RSOA chip at 22°C.