Sapphire Fiber Fabry-Perot Sensors With High Fringe Visibility

Abstract

It is difficult for sapphire fiber Fabry-Perot (FP) sensors to generate high quality interference fringes because their highly multimode property. In this paper, we report a sapphire fiber FP strain sensing system with high fringe visibility, realized by the use of a self-made fiber collimator. The collimator is made by a quarter-period graded index optical fiber (GIOF) fused to a single mode fiber (SMF). In the contrast experiment, no effective signal was collected from a sensing system without the fiber collimator. While adding a fiber collimator into the sensing system, high visibility interference fringes were collected. The fringe visibility is 49.37% when the FP cavity length is 341.1 μm, and 20.09% when the cavity length is 1343.3 μm. The effective range of the cavity is over 1000 μm. Strain experiment at room temperature shows the measuring range is 10037 με with relative error of 0.37% while the gauge length is 100 mm. High temperature experiment was also carried out and the result shows that the sensor can work at 1300 °C. This method is expected to be helpful for decreasing the difficulty of fabricating high fringe visibility sapphire fiber FP sensors, and increasing the measuring range.

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

“…In the past decade, optical fiber temperature sensor has been developed rapidly, because of its unique advantages such as high sensitivity, small size, light weight and immunity to electromagnetic interference [1][2][3][4][5]. Interferometers with different structures have built micro-nano laboratories on optical fibers to achieve the ultimate pursuit of sensitivity, including the Mach Zehnder interferometer (MZI) [6][7][8][9], Fabry Perot interferometer (FPI) [10][11][12], Michelson interferometer (MI) [13][14][15][16] and the Sagnac ring structure [17][18][19][20]. However, due to the limitation of demodulation mode, the OSA has a slow demodulation speed, which makes it very difficult to realize real-time online temperature monitoring [21][22][23].…”