Enhancement of the sensitivity of a recirculation fibre ring interferometer with pulsed pumping of an intracavity optical erbium-doped fibre amplifier

The signal sensitivity and detection capability of a recirculation fibre ring interferometer (RFRI) are studied experimentally upon pulsed pumping of an intracavity ytterbium-sensitised erbium-doped fibre amplifier (YEDFA). It is shown that the number of effective circulations of light in the ring resonator can be substantially increased in the transient regime above the self-excitation threshold when, however, lasing has yet no time to develop. It is found that the required transient regime is achieved due to the self-restriction (drop) of amplification in YEDFA caused by the saturation of the active medium with increasing radiation power in the resonator. The increase in the signal sensitivity of the RFRI and its detection capability by factors of 25 and 4, respectively, is demonstrated in the pulsed regime of the YEDFA.