Temperature Sensor Based on Fiber Ring Laser With Cascaded Fiber Optic Sagnac Interferometers

A new temperature fiber ring laser (FRL) sensor based on a cascaded Sagnac loops structure is proposed and experimentally demonstrated. The optical FRL consists of by inserting two polarization-maintaining fibers (PMF) with slightly different lengths. PMF length 56 cm 75 are used in as filter sensing unit cavity. working principle the phase shift (?) caused birefringence between principal polarization modes enhance sensitivity constructing Vernier-scale. In an appropriate range (25 °C - 31 °C), detection significantly higher than other sensors. Thanks to system, can be modulated changing free spectral (FSR). experimental results show that cascade 4.031 nm / °C, which five times base single structure.