Fiber Temperature Sensor Based on Vernier Effect and Optical Time Stretching Method

Abstract

A novel method for ultra-sensitive and ultra-fast temperature sensing has been successfully implemented by cascading Saganc rings to generate the Vernier effect and doing the same dispersive fibers to achieve the optical time-stretching effect. This is different from the traditional point fiber sensor demodulated by optical spectrum analyzer (OSA) whose demodulation speed is usually at the second level. The designed system maps the wavelength domain to the time domain through the dispersive fiber, which can realize the ultra-fast temperature monitoring at the nanosecond level. The cascaded Sagnac ring is composed of polarization maintaining fiber (PMF) which is significantly affected by the thermal-optical coefficient. When the temperature changes, the variation is as high as −6.228 nm/°C, which is 8.5 times higher than the sensitivity based on the single Sagnac ring system. Furthermore, through the optical time stretching scheme, the corresponding response sensitivity is increased from 0.997 ns/°C to 7.333 ns/°C, and the magnification is increased 7.4 times with a response speed of 50 MHz.

Dual-Parameter Fiber Sensors for Salinity and Temperature Measurement Based on a Tapered PMF Incorporated With an FBG in Sagnac Loop

“…The sensor with the sensitivity of 0.356 nm/‰ for salinity measurement is achieved. At the same time, the sensor has the response to temperature, and with the help of high birefringence index of PMF [24], the temperature measuring can reach sensitivity of 0.616 nm/°C in the range of 22 °C-36 °C. Thanks to the temperature compensation provided by FBG, dual-parameter measurement of salinity and temperature can be realized.…”