Insitu loss determination in Erbium-doped fiber lasers having different resonator configurations by studying relaxation oscillations

Erbium doped fiber lasers represent an important class of efficient coherent light sources useful in optical communication systems. Fiber lasers have been built with various resonator configurations, (a) with mirrors not in contact with fibre ends and (b) with mirrors butted to the fibre ends. It is difficult to estimate the resonator losses accurately, but they can be measured in Erbium doped fiber lasers under actual operating conditions by studying the relaxation oscillations of the laser. This paper reports on a study made of relaxation oscillations in an Erbium-doped fiber laser and the determination of the threshold pump powers, cavity lifetimes and single pass losses of the laser for a linear resonator configuration with (a) butted mirrors (b) mirrors not in contact with the fiber ends and (c) also for a ring resonator configuration. The laser thresholds obtained by this method has been compared with those determined by us from other methods. This technique of determining the resonator characteristics from the study of relaxation oscillations permits in situ loss measurements in Erbium doped fiber lasers.