Self Optical Pulsation Based RZ-BPSK and Reused RZ-OOK Bi-Directional OC-768 Transmission

The generation and reusing of a self-pulsated optical RZ carrier is demonstrated to achieve bi-directional OC-768 transmission with downstream return-to-zero binary phase-shift keying (RZ-BPSK) and reused upstream return-to-zero ON-OFF keying (RZ-OOK) data formats at 40-Gbit/s. The self-started optical RZ carrier is generated by linking a single-mode laser with a nonlinearly biased Mach-Zehnder modulator based self-feedback loop, which is externally modulated to transmit the downstream RZ-BPSK and reused to transmit the upstream RZ-OOK. By lengthening the true-time delay in the self-feedback loop with a 900-m long SMF, the self-started 40-GHz photonic-microwave clock with an ultralow SSB phase noise of -160 dBc/Hz at an offset frequency of 100 kHz could suppress its relative timing jitter to 2 fs for obtaining a Q-factor as high as 5 × 10
¹⁶
. Both the photon-microwave clock and optical RZ carrier can be triggered to achieve bi-directional downstream RZ-BPSK and upstream reused RZ-OOK transmissions with receiving power sensitivities of -15.7 and -12.3 dBm, respectively, at a requested BER of 10
^-9
. The bi-directional downstream RZ-BPSK data reveals a comparable BER performance with the uni-directional case by a power penalty of only 0.5 dB, whereas the power penalty between uni- and bi-directional upstream RZ-OOK data is up to 3 dB.