LFM-Costas waveform generation based on a Fourier domain mode locking optoelectronic oscillator

Abstract

A linear frequency modulation (LFM)-Costas waveform generation scheme is proposed and experimentally demonstrated based on a Fourier domain mode locking (FDML) optoelectronic oscillator (OEO). The FDML OEO is established based on stimulated Brillouin scattering (SBS) effect, where the Costas-coded probe light is realized by employing an open-loop voltage controlled oscillator (VCO) via electro-optic frequency shift. In the experiment, an LFM-Costas waveform with a 12-bit Costas sequence, a chirp rate of 39.234 MHz/μs and a period of 20.390 μs is generated in the frequency range of 8.020 GHz to 8.820 GHz. The generated LFM-Costas waveform has good pulse-to-pulse coherence according to the correlation results, and has been used to detect two targets with a distance difference of 0.30 m and 0.20 m.