Vibration sensor based on highly birefringent Bragg gratings written in standard optical fiber by a femtosecond laser

Abstract

We present a vibration sensor based on highly birefringent fiber Bragg gratings written in standard single mode optical fiber and realized with UV femtosecond pulses. This vibration sensor takes advantage of the stress-induced phase shift between the two orthogonally polarized fiber eigenmodes which induces intensity distribution changes in the two fiber Bragg grating reflection modes. The gratings are inscribed with the femtosecond line by line technique and have a birefringence value of 6 10^-4. We demonstrate that theses gratings are temperature birefringence insensitive and ideal for vibration measurements.