Wideband Microwave Phase Noise Analyzer Based on All-Optical Microwave Signal Processing

An approach for wideband phase noise measurement of microwave signal sources is proposed based on all-optical microwave signal processing. In the proposed scheme, an optical carrier is sequentially modulated by the signal under test (SUT) in a phase modulator and a dual-polarization modulator to generate two +1st-order sidebands with orthogonal polarizations. A time delay is introduced between two sidebands by a span of low-loss optical fiber. Combined with a polarization controller and a polarizer, photonic microwave downconversion with a desired phase shift and time delay can be realized after photodetection, and the phase noise of the SUT can be calculated thereafter. Since all the microwave signal processing functions in the conventional photonic-delay-line-based phase noise measurement system are implemented in the optical domain, the proposed scheme has a large operational bandwidth and a high measurement sensitivity. In the experimental demonstration, accurate phase noise measurement of SUTs is achieved in a frequency range of 10-35 GHz, and a phase noise floor as low as −132.16 dBc/Hz at 10 kHz is obtained.