Phase-coded microwave signal generation with a built-in optoelectronic oscillator based on a dual-parallel Mach-Zehnder modulator

A scheme for binary phase-coded microwave signal generation is proposed and experimentally demonstrated with a dual-parallelMach-Zehnder modulator (DPMZM). The carrier of the generated phase-coded signal is provided by the built-in dual-loop optoelectronic oscillator (OEO) based on the DPMZM. The principle of this signal generator and the oscillating condition of theOEOis theoretically described in detail. It is found that phase-coded signals can be produced by setting the three working points and the modulation depth of theDPMZM.In the proving experiment, a 10-GHz oscillating signal with a side mode suppression ratio of 49 dB is generated. The phase noise of this carrier wave is measured to be-80 dBc=Hz at 10 kHz offset with a 100-m and 1-km optical fiber used in the two oscillation loops.When1-Gbit/s and 2-Gbit/s coding signals are, respectively, applied to theDPMZM,two 10- GHzself-oscillating phase-coded signals are eventually produced, and the π phase shift in the signals is successfully confirmed with the phase information extracted fromthe phase-coded signals.