A novel fiber optic microbend pressure sensor

A novel fiber optic sensor employing microbend modulator and small-displacement diaphragm with hard center is presented in this paper. The sensor is made up of isolation diaphragm, silicon oil, sensing diaphragm, microbend modulator, sensing optical fiber, reference optical fiber, supporting platform, adjusting bolt, front cover and back cover etc. It can be used to measure the pressure of gas or liquid. When the pressure is applied to the isolation diaphragm, it passes an it to the sensing diaphragm through silicon oil. Then the hard center of the sensing diaphragm produces small displacement. Thus the light in the sensing optical fiber between the microbend modulator is attenuated. By detecting the output light power the relationship of the input pressure and relative output light power is obtained. The basic structure is given and the sensing mechanism is discussed. Experiments have shown a satisfactory result. The sensitivity and measuring range of the sensor can be modified by altering the mechanical wavelength of the microbend modulator, ratio of the teeth number of the two deformer plates or by changing the parameters of the sensing diaphragm. The sensor has the function of zero adjustment and overload protection.