Stable dual wavelength erbium doped fibre laser

Abstract

This project investigates the stability of a dual wavelength erbium doped fibre laser. The lasing wavelengths of the dual wavelength fibre laser are 1555.12nm and 1560.32nm respectively. The laser is based on a ring cavity resonator which employs fibre Bragg gratings to select the lasing wavelengths. The active medium in the cavity is a 3.2m long Erbium doped fibre with an absorption of 11.38 dB/m at 980 nm. The stability of the dual lasing wavelengths was investigated using an optical loop mirror with a 1m length of singlemode fibre, and an unpumped erbium doped fibre of length 0.5m, 1m and 1.5m respectively. Also, the effect of changing the cavity length on the uniformity of the wavelength power increase with an increase in pump power was investigated together with the stability of the lasing wavelength over a 1 hour period. An increase in cavity length by 5 cm led to a good prospect for a stable dual wavelength laser with an output power difference of 0.4dBm between the dual wavelengths and a stability of 0.4dBm.