Mengling Xiong

Simultaneous Measurement of Curvature and Temperature Based on Mach–Zehnder Interferometer Comprising Core-Offset and Spherical-Shape Structures

A novel sensor for simultaneous measurement of curvature and temperature based on the Mach-Zehnder interferometer (MZI) is presented. The sensor consists of slight core-offset and spherical-shape structures. The core offset excites cladding modes, and the spherical shape couples the cladding modes back into the core and interferes with the core mode. Two dips of the interference fringe shift with the variation of curvature or temperature, and simultaneous measurement of curvature and temperature can be realized by means of a sensitivity coefficient matrix. Two MZIs with different lengths are fabricated. For sensor 1 with the length of 20 mm, the curvature sensitivity is as high as -22.227 nm/m -1 in the range of 4.66-5.50 m -1, and the temperature sensitivity is 0.0847 nm/°C in the range of 60 °C-100 °C. For sensor 2 with the length of 16 mm, the curvature sensitivity is -20.128 nm/m -1 in the range from 5.66 to 6.53 m -1, and the temperature sensitivity is 0.0737 nm/°C in the range from 40 °C to 100 °C.

Simultaneous Refractive Index and Temperature Measurement Based on Mach–Zehnder Interferometer Concatenating Two Bi-Tapers and a Long-Period Grating

An all-fiber sensor for simultaneous refractive index (RI) and temperature measurement based on Mach-Zehnder interferometer (MZI) is proposed and demonstrated experimentally. The MZI consists of two bi-tapers and a long-period grating. Two dips in the interference spectrum exhibit different responses to the variations of RI and temperature, and simultaneous measurement of RI and temperature can be realized by means of sensitivity coefficient matrix. Experimental results show that the RI and temperature sensitivity for the proposed sensor are -108.16 nm/RI and 0.12 nm/°C, respectively.

Optical fiber hollow ellipsoid for directional bend sensing with a large bending range

A micro-fabricated Mach–Zehnder interferometer in optical fiber is demonstrated for bend sensing in four orthogonal directions. The intensity of the resonant dip exhibits a linear response to curvature in a logarithmic unit within a large range from 0 to 9 m−1, and the sensitivities obtained are 0.42 dB/m−1, 0.186 dB/m−1, −0.41dB/m−1, −0.265 dB/m−1, in the directions of 0°, 90°, 180°, and 270°, respectively. The temperature-induced curvature error is only ~0.012 m−1/°C in the bending directions of 0° and 180°. The device is compact, robust and efficient in operation.

Wavelet transform filtering method of optical fiber Raman temperature sensor

The traditional wavelet filtering threshold de-noising method is widely used in the optical fiber Raman sensor temperature measurement, but the weakly spontaneous Raman scattering signal is easily submerged by optical noise and random noise. So the method has a low efficiency. In order to increase the efficiency of signal denoising in the process of temperature measurement, we proposed a new method combine default threshold and the given threshold based on the traditional method. The experimental data of 25Km fiber Raman sensor is filtered by the new method and the results show that the new threshold method can eliminate the noise in the signal, and also preserve the information of temperature variations.

M-Z optical fiber liquid level sensor based on two cascaded spherical-shape structures

An MZI for measurement of liquid level is proposed and demonstrated, which consists of two cascaded spherical-shape structures. Two interferometers with different lengths of 34mm and 40mm are manufactured with their sensing characteristics studied. By measuring wavelength shifts of the dip in the interference spectrum, we can measurement liquid level. Experimental results show that the sensor (34mm) has a higher sensitivity of liquid level compared to the sensor (40mm). A higher liquid level sensitivity of −1.172nm/cm is obtained.