A fattening Michelson and Fabry-Perot interferometers as comb filter and its application as switchable linear fiber laser

This work presents a switchable multiwavelength erbium-doped fiber laser based on a fattening Michelson interferometer (FMI) cascaded with a silicon wafer (SW) of 525 μm thickness, acting as a Fabry-Perot interferometer (FPI), together producing a comb filter (CF). Fattening fusion splicing a single-mode fiber (SMF-28) segment with a non-zero dispersion-shifted fiber (NZ-DSF) generates an FMI. The proposed linear cavity design uses the CF as a wavelength-selective filter (WSF). Experimental results show that the Free Spectral Range (FSR) for FPI and FMI was 0.6 and 8 nm, respectively, with a fringe contrast of approximately 10 nm for both. Furthermore, the laser lines can be switched from 1560 to 1565 nm by changing the curvature over the FMI. In this way, we obtain single, double, and quintuple emission lines by applying micro-bending from 0 to 0.622 m⁻¹. The laser has a side mode suppression ratio (SMSR) of about 47 dB and a 3 dB linewidth of 0.06 nm. Finally, the laser arrangement is compact and robust, requiring a relatively simple fabrication procedure.