Multilongitudinal-mode fiber laser temperature sensor and its applications in the measurement of temperature dependence of fiber birefringence

In this paper, an active temperature sensor based on beat frequency interrogation of a multilongitudinal-mode fiber laser has been proposed and demonstrated. Temperature measurement has been achieved through beat frequency interrogation of the proposed multilongitudinal mode laser. Experimental results show that the temperature sensing curve has good linearity with a coefficient of determination of 0.996004 for a temperature range of 30°C to 105.3°C. Furthermore, its application in the measurement of temperature dependence of fiber birefringence has been also investigated. And calculation results according to experimental observation of the beat frequency spectrum indicate that as temperature increases intrinsic fiber birefringence also linearly increases with a temperature coefficient of about 4.4×10^-10/°C. The proposed multilongitudinal-mode fiber laser sensor based on beat frequency interrogation has several advantages including compactness, high signal to noise ratio, etc, which is expected to be employed in future sensing applications.