Multiple frequency-swept source based on recirculating frequency shifter loop

A multiple frequency-swept source based on a recirculating frequency shifter loop (RFSL) is established. Three distributed feedback (DFB) lasers are used as a seed source and sweep in the RFSL synchronously. The swept spectra of the separate DFB lasers are precisely controlled and stitch together without overlap. The key significance of this technique is that the swept range increases as the number of the multiple seed wavelengths increase. Experimentally, the swept range of our system can broaden to 4.5 nm/3.9 nm with an 8.6 GHz/7.5 GHz swept step. The swept rate is 200 kHz. The output of the source is sent into a Mach-Zehnder interferometer and the interference signal is detected to measure the length difference of interferometer arms.