Dual-Parameter Optical Fiber Sensor for Temperature and Pressure Discrimination Featuring Cascaded Tapered-FBG and Ball-EFPI

A dual parameter optical fiber sensor for temperature and pressure discrimination has been proposed and experimentally realized. A tapered fiber Bragg grating (tapered-FBG) and an extrinsic Fabry-Perot interferometer with a ball shape (ball-EFPI) are the two main sensing structures. The taper is fabricated by elongating it during an arc-discharge provided by the fusion splicer. Then, the femtosecond laser is used to inscribe a first-order Bragg grating in the taper region, adopting the point-by-point direct-writing technique. The ball-EFPI is fabricated using the chemical etching and arc-discharge enlargement method. The test temperature range is 40 °-400°, and the test pressure range is 0-2 MPa on the basis of ambient pressure. Experimental results show that the tapered-FBG has good temperature response while the ball-EFPI is sensitive to pressure. By analyzing the sensitivity matrix, the temperature and pressure discrimination can be achieved using the proposed hybrid sensor.