Experimental validation of FWM efficiency improvement in multichannel fiber laser by using DF-HNLF

•Comparison of FWM efficiency was made with various structures and different fibers.•Roles of nonlinearity and dispersion in FWM efficiency were analyzed.•Efficient multiwavelength output with double-pass scheme was generated.•Flat multiwavelength output with narrow channel spacing was achieved.

We proposed and experimentally reported on an efficient multiwavelength generation with narrow wavelength spacing based on four-wave mixing. The employment of dispersion flattened high nonlinear fiber (DF-HNLF) and double-pass configuration enable an efficient multiwavelength generation with a 3 dB bandwith of ~11 nm and a wavelength spacing of 0.1 nm. Comparisons were made by inserting a 500 m long standard single mode fiber (SSMF), a 500 m long conventional high nonlinear fiber (HNLF) and a 500 m long DF-HNLF into the cavity, respectively, to analyse the role of nonlinearity and dispersion. Compared with HNLF, an improvement of almost 200% was made in 3 dB uniformity of output spectrum in our DF-HNLF based multiwavelength system.