Multi-Band LFM Signal With Unidentical Bandwidths Subjected to Optical Injection in a DFB Laser

This letter demonstrates a tunable multi-band linear frequency modulation (LFM) signal with improved and unidentical bandwidths subjected to optical injection in a distributed-feedback (DFB) laser. In the proposed scheme, an optical beam is divided into two paths, one modulating with a baseband LFM signal and another with a power-varying signal. The basic principle of the proposed scheme is the optical beating of the carrier-suppressed ±1
^st
sidebands in one path and the red-shifted emission mode of the DFB laser after optical injection in another path. In the experiment, the generated three LFM signals have the bandwidths of 11.5 GHz (from 23.0 to 34.5 GHz), 7.5 GHz (from 15.0 to 22.5 GHz), and 4 GHz (from 8.0 to 12.0 GHz) in one period of 1 μ s. Moreover, we analyze the effect of the injected beam's frequency and power on the bandwidth tunability of the generated LFM signals.