Study on the Spatial Division Multiplexing Technique of Fiber Bragg Grating Sensors

The optical switch spatial division multiplexing sensing system is proposed by using wavelength division multiplexer and unbalanced Mach-Zehnder interferometer. Controlled by an optical switch, fiber Bragg grating sensing system based on spatial division multiplexing was achieved when a broadband source illumines FBG sensor array. With an isosceles triangle cantilever beam to realize linear tuning of Bragg wavelength of fiber grating without chirping by adjusting the deflection of the free end, the system employs an unbalanced Mach-Zehnder interferometer to translate the FBG wavelength signal related the strain into phase signal. The wavelength division multiplexer is adopt to realize the demand of the change of different fiber Bragg grating wavelength. The strain can be recovered by measuring the phase change of the signal with signal processing circuit. With the characteristic of high resolution, wide measuring range, this sensing system has the capability of measuring static strain as well as dynamic strain. Experiment demonstrated that the sensing sensitivity of this system, which was with a resolution of 20 nepsiv, was 0.29deg/muepsiv.