Optical fiber interference sensor based on fiber ending micro-groove fabricated by femtosecond laser

An optical fiber interference sensor with a fiber end groove structure that was fabricated by a femtosecond laser is presented for temperature and refractive index measurement. In the designed fiber sensor, a groove that was 40 mu m deep and 50 mu m wide was etched on the fiber end along the core at the SMF-28 fiber. The microstructure was manufactured by the femtosecond laser through a line-by-line scanning method. In an experiment, the sensor head was inserted into NaCl solution. The interferometer wavelength interval was 46 nm, and the stripe contrast was 17 dB. Under different vertical refractive indexes (RIs), the corresponding comb spectrum was obtained. Results showed that the proposed fiber filter exhibited an RI sensitivity of 3282.176 nm per refractive index unit (RIU) and 1317.351 dB/RIU, respectively. In addition, the temperature characteristic was measured. The wavelength variation was not obvious and the power fluctuation curve was linear within 50 degrees C-100 degrees C. The sensor spectrum had good repetition at high and low temperatures. The results demonstrated the satisfactory performance of the refraction and temperature sensor. (C) 2018 Elsevier GmbH. All rights reserved.