Photonic-Assisted Wideband Phase Noise Analyzer Based on Optoelectronic Hybrid Units

Abstract

We demonstrate a photonic-assisted wideband phase noise analyzer based on optoelectronic hybrid units comprising a microwave photonic phase shifter (MPS) and a microwave true time delayer. The MPS and the microwave true time delayer are achieved by a dual-drive Mach-Zehnder modulator (DMZM) incorporating with a broadband microwave frequency up-convertor (MFC) and an optical fiber delay line (ODL), respectively. Our scheme, which is analogous to the conventional microwave delayed homodyne self-reference method, can effectively improve its accuracy using longer time delay with minimum power consumption. In the scheme, the microwave signal is up-converted using the MFC and then down-converted using optical mixing in a photo-detector (PD). Meanwhile, the microwave signal is phase shifted using the MPS and time delayed using the ODL and are finally homodyne mixed with reference signals for converting phase fluctuations to voltage fluctuations. The motivation of this work lies in the fact that the previously reported phase noise measurement configurations based on photonic techniques are hard to accurately measure phase noise of microwave oscillators working at low frequencies. The microwave signals are phase tuned over 360° at frequency range of 0.5–9 GHz to achieve a photonic-assisted phase detector. Microwave signals at the frequency of 3-, 9-GHz are measured with a phase noise of –70.9 and –66 dBc/Hz at 1 kHz offset frequency, respectively.