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-parallel Mach-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 the OEO is 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 the DPMZM. 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/ at 10 kHz offset with a 100-m and 1-km optical fiber used in the two oscillation loops. When 1-Gbit/s and 2-Gbit/s coding signals are, respectively, applied to the DPMZM, two 10-GHz self-oscillating phase-coded signals are eventually produced, and the phase shift in the signals is successfully confirmed with the phase information extracted from the phase-coded signals.