Design and fabrication of a fiber Bragg grating temperature sensor

Abstract

A Bragg Grating Fiber temperature sensor with a grating period of 1550 nm was designed and fabricated. Excellent linearity was observed in the range -60 degrees Celsius to + 150 degrees Celsius between the shift in center wavelength and temperature. The grating was fabricated using a phase mask with its grating profile normal to the fiber axis. The phase mask was placed directly on top of a Corning SMF CPC6 single mode optical fiber and a tunable (365 - 405 nm) Helium Neon UV laser with an output intensity of 3 mW/cm 2 was scanned along the mask for one hour. The wavelength of the Fiber Bragg Grating was measured to be 1550.36 nm. Its performance was characterized by monitoring the shift in the Bragg Wavelength as a function of temperature. This is described with a linear equation of the form T equals KL + b, where T represents temperature in Celsius, L is the position of the Bragg Wavelength as measured on an Optical Spectrum Analyzer, K is the experimentally determined thermal expansion coefficient, and b is the wavelength position corresponding to 0 degrees Celsius. For this fiber sensor, T equals 100L(nm) - 155016. It exhibited a shift in center wavelength of 0.01 nm/degrees Celsius change in temperature.