Transmission Performance of an Electroabsorption–Modulator Based Self-Started Optical Pulsator and Synthesizer-Free RZ Clock and Data Generator

A synthesizer-free self-starting optoelectronic oscillating-pulsator based return-to-zero (RZ) carrier, clock, and data generator is demonstrated by using an integrated distributed feedback laser diode and electroabsorption modulator (DFBLD-EAM) link. The theoretical model of the self-pulsating EAM is numerically analyzed to optimize optical RZ carrier, providing the relatively short pulsewidth, highest ON/OFF extinction ratio, timing jitter, and frequency variation of 16.5 ps, 10.1 dB, 0.6 ps, and <;220 kHz, respectively. Such a self-pulsating EAM pulsed carrier exhibits a chirp of -13.5 GHz with corresponding chirp parameter of -0.48, which reveals lower frequency chirp accompanied with higher chirp parameter at lower EAM bias. To trigger the pseudorandom binary-sequence (PRBS) data generator, the DFBLD-EAM based self-starting pulsator also delivers an OC-192 microwave clock with a carrier-to-noise ratio of 51.1 dB, a second-harmonics suppression ratio of 55 dB, and a single-side-band phase noise of -110 dBc/Hz at 10 kHz offset. The proposed system provides a synthesizer-free OC-192 RZ data generation with bit-error rate of 10^-9 under receiving power of -19.8 and -17.2 dBm at back-to-back and 25-km propagation. The receiving sensitivity is improved by 2 and 1.6 dB when comparing with that of a commercial synthesizer triggered RZ data generator. The reduced power penalty is attributed to the signal broadening induced by higher frequency chirp of the self-pulsating EAM. The signal-to-noise ratio of the generated RZ data plays more important role than the extinction ratio on obtaining a better Q-factor up to 6.6.