Generation and transmission of phase-stable coherent multi-band linear frequency modulated signals

We present a coherent multi-band linear frequency modulated (LFM) signal generation and transmission system based on dual optical frequency combs (OFCs). In the proposed scheme, the two OFCs are phase-locked to ensure high coherence of the generated multi-band LFM signals. A round-trip phase correction is adopted to stabilize the time delay of the fiber transmission and enable the system to resist temperature variation. In the demonstration experiment, the generated multi-band LFM signals across L, S, and C frequency bands has a bandwidth of 200 MHz in each band. The root-mean-square (RMS) phase deviation of the multi-band signal is below 4 × 10⁻³ rad after 1.2 km fiber transmission. During 1^◦C temperature variation, the RMS phase drift is suppressed from 1 rad to 0.1 rad. The high signal coherence between different bands and the capability of resisting temperature variation are highly desired for a multi-band distributed radar system.