Optical twisting alert sensor based on PM-EDF short cavity DBR laser

We report an optical twisting alert sensor using beat frequency from a short cavity polarization-maintaining erbium-doped fiber (PM-EDF) based distributed Bragg reflector (DBR) laser. A DBR fiber laser with an effective cavity length of ∼ 1 cm formed by a pair of fiber Bragg gratings (FBGs) inscribed on a portion of PM-EDF was developed for demonstrated. This fiber laser exhibited stable operation in dual-polarization single-longitudinal-mode. The amplitude of the beat frequency generated by two orthogonal polarizations of the cavity is twist dependence. It is shown that the beat frequency signal can be completely “turned off” at ∼ 180° twist angle. This type of single mode DBR fiber laser can be used as optical twisting alert sensors for remotely interrogated systems and multi-parameter monitoring systems.