Stitch-free widely tunable dual-channel fibre laser for use in a passive component analyser

A widely-tunable laser source (WTLS) is discussed that is particularly well-suited for use in a passive component analyser, which is based on a novel design incorporating two distinct resonant cavities sharing a common tuning element and a common optical output. This design comprises a polarisation-maintaining fibre, two semiconductor optical amplifiers, a low-loss tunable filter and wavelength-independent fused couplers. The WTLS can be continuously tuned over the O-, E-, S-, C- and L-bands with an output power greater than -12 dBm from 1250 to 1637 nm and a peak power of 4.5 dBm. The laser exhibits a signal-to-noise ratio of greater than 80 dB over almost all the spectral range when measured with an optical spectrum analyser having a resolution bandwidth of 1 nm. Its effective 3-dB linewidth is less than 7 GHz