Microwave Photonic Source for Coherent Doppler Lidar System Operating at 1550 nm

摘要

We present theoretical and experimental results for a microwave photonic oscillator (MPO) that provides a mi- crowave signal and a modulated optical wave simultaneously. Among the different techniques currently in use for optically generating a microwave signal, we have chosen a ring configuration based on an electro-optical Mach-Zehnder modulator (EOM) driven by a 1.55μm DFB laser diode. An accurate modelling of EOM and the contributions from all noise sources in the oscillation loop allows us to predict performances of our designated MPO in a very good agreement with the measured oscillation power (up to 22 dBm, depending on the DC bias voltage) and phase noise spectral density (- 130 dBc/Hz @ 10 kHz away from the carrier). We propose this hybrid microwave photonic source to be used as a local oscillator for a coherent laser radar operating at 1550 nm. A good compromise between a very high tunabil-ity range (1-8 GHz) and a high spectral purity (> - 120 dBc/Hz @ 10 kHz) is obtained through a dual-loop configuration for the MPO.