Mach-Zehnder fiber interferometers for sensing applications incorporatingphotoinduced mode coupling filters in elliptical-core high-birefringence fibers,

摘要

Abstract: Photogenerated mode coupling filters for temperature and strain sensing are described. Mach-Zehnder fiber interferometers have been fabricated in elliptical-core, high-birefringence fibers where the directional couplers of a conventional fiber interferometer are replaced by two polarization rocking filters written on the same fiber. One interferometer having an operational bandwidth of 18 nm was used as a temperature sensor with a measured sensitivity of 9.1 mrad/($DEG@C cm). Photoinduced polarization couplers written with 266 nm light can survive temperatures of 200$DEG@C. This allows development of a temperature sensor based on the shift of the resonant wavelength of the coupler with temperature. A scheme for the simultaneous measurement of strain and temperature based on the use of a Bragg grating and a mode coupling filter is proposed.!19