Multiwavelength generation utilizing hybrid loop fibre NL-PM-750 PCF chirped Fabry–Pérot resonator

This paper presents a hybrid interferometric system for multiwavelength fibre-laser generation in the C-band. The configuration integrates a nonlinear polarisation-maintaining photonic crystal fibre (PCF) loop (NL-PM-750) with dual chirped fibre Bragg gratings (CFBGs) forming a Fabry–Pérot resonator. The NL-PM-750 fibre, featuring negligible polarisation-mode dispersion and a honeycomb microstructure, was chemically etched in 40 % hydrofluoric acid for 10 min and 20 min, reducing the outer diameter to (104.74 ± 0.15) µm and (95.02 ± 0.12) µm, respectively. This etching enhanced the nonlinear coefficient from (10.2 ± 0.4)/(W km) to (16.3 ± 0.6)/(W km) through the associated reduction in effective mode area. Optimal operation (20 min etching at 20 dBm EDFA output) yielded five wavelength channels at 1,529.679 nm, 1,530.996 nm, 1,531.862 nm, 1,532.407 nm and 1,533.147 nm. The system achieved a peak optical signal-to-noise ratio of (38.5 ± 0.3) dB, a mean channel spacing of 0.867 nm with a standard deviation of 0.33 nm, and wavelength stability with a standard deviation of 0.023 nm over 60 min. Statistical analysis demonstrated a mean spectral power density of (14.22 ± 0.85) µW/nm with a variance of 808.7 (nW/nm) 2 at the optimal operating point. Compared to representative approaches in the recent literature, the configuration provides improved OSNR while maintaining a compact, passive architecture based on chirped-grating spectral selectivity and etching-enhanced nonlinearity.