Diameter Measurement System Using the Spectrum Distortion of a Twin-Hole Fiber Bragg Grating

A new component diameter measurement system that uses a twin-hole fiber Bragg grating (THFBG) is proposed. The diameter is obtained by observing the distortion of the THFBG transmission spectrum. Furthermore, the wavelengths and the relative intensities of different troughs are extracted from the transmission spectrum to measure the diameter. It is experimentally found that the wavelengths of the troughs are independent of changes in the diameter, and the relative intensities of different troughs obtained via different calculation methods change monotonically with increasing diameter. The relative intensity ratio between different troughs is used to measure the sample diameter to eliminate the measurement interference caused by the difference in light source output intensity at different measuring points. The relationship between this relative intensity and the diameter is monotonic and nonlinear, and a maximum sensitivity of -0.5894 cm(-1) is achieved when the sample diameter is 4 cm.