Multi-carrier broadband signal generation based on a mutually dual-domain mode-locked optoelectronic oscillator

Abstract

A novel dual-domain mode-locked optoelectronic oscillator (DDML-OEO) is proposed and demonstrated to generate multi-carrier broadband signal. The DDML-OEO is built up by mode-locking a conventional OEO at the time domain and Fourier domain mutually. The Fourier domain mode locking (FDML) is achieved by driving the laser with a period triangular waveform voltage, of which the frequency is synchronized with the round-trip time of the OEO loop. Meanwhile, an electrical signal synchronizing with the free spectrum range (FSR) of the OEO loop is injected to realize the time domain mode locking (TDML) process. Through combined mechanisms of the FDML and TDML, the multi-carrier broadband signal can be directly generated via the DDML-OEO. Thanks to the TDML, different multi-carrier bands of the signal are coherent and the phase noise of the generated broadband waveform is strongly suppressed compared with free-running FDML-OEO. With the proposed scheme, an ultra-low phase noise of −111.1 dBc/Hz at 10 kHz offset for the generated multi-broadband signal waveform is achieved when the cavity length is about 3000 m. The bands interval, the bandwidth and the central frequency tunability are all discussed, which have great potential usage in multi-channel radar transmitter.