Characterization of an EDF fiber laser strain-tuned by two high- strength fiber bragg gratings

This paper describes the characterization of a tunable erbium-doped fiber laser with a linear cavity used for fiber Bragg grating sensors interrogation. The laser is mechanically tuned by a highly-stretchable fiber grating that works as a cavity end reflector. A 2 times 1 optical switch allows two gratings to be connected to the laser cavity at a time. The gratings are bonded onto a piezoelectric device that stretches them periodically, inducing Bragg wavelength shifts and tuning the laser output signal. A synchronized TTL signal is applied to the optical switch, changing the end reflector gratings and allowing the system to scan two distinct spectral ranges. The scanning laser signal features significant relaxation oscillations during a short period of time after the grating switching. These oscillations are investigated with reference to the drive current of the laser diode used to pump the EDFL and the pump ratio r.