Experimental and theoretical investigation of fiber ring laser dynamics and transient analysis

We report the experimental and theoretical studies on the dynamics of a fiber ring laser system which contains a length of erbium doped fiber pumped at 980nm connected to a fiber loop consisting of a micro-optic gas cell and a tunable bandpass filter. Due to a long loop length ~60m of the system, the number of cavity modes present in the 1nm filter bandwidth is extremely large. As a result, the effect of spontaneous emission into these laser modes plays an important role in determining the dynamics of the laser. A theoretical model which incorporates the effect of spontaneous emission into multiple laser modes is described and it is shown to be in agreement with experimental results obtained. A detailed analysis has been performed on the relaxation oscillations induced during the transient operation of the laser with the aim of using it as a tool for obtaining laser parameter