Long Sensing Gauge Fiber Bragg Grating Sensor with Pretension

A novel long gauge strain Fiber Bragg Grating sensor (LG FBG sensor) has been proposed. Pretension technique and packaging method were proposed and demonstrated. Two kinds of long gauge strain FBG sensors were made, which can measure the average strain in 10cm gauge and 20cm gauge, respectively. Calibration test is conducted to obtain the strain coefficient and temperature coefficient of the sensor. Comparison tests have been carried out, and the results verify the feasibility of the proposed sensor. Introduction As one of the most important fiber optic sensor, significant amount of interest in fiber Bragg grating sensing techniques have been generated in a variety of fields. Since the photosensitivity of Germania doped fiber was discovered by Hill (1978), and transverse holographic method using UV illumination was invented by Meltz(1989), Fiber Bragg Grating received extensive attentions from research organizations around the world. FBG’ s application in communication field resulted in maturation of the technique. FBG, as a novel type of sensor, was initially applied to military fields such as aviation. Lots of measurands such as stress、vibration、pressure、magnetic field can be measured by FBG through the two basic measurands strain and temperature. Fiber Bragg grating(FBG) are sensor elements which are photo-written into optical fiber using intense ultra-violet laser beams and have the ability for the measurement of strain and temperature. The speciality of using FBG sensor for strain sensing application is that it is able to measure strains locally with high resolution and accuracy. As the physical size of an optical fiber is extremely small compared with other strain measuring components, it enables it to be embedded into the structures for determining the strain distributions without influencing the mechanical properties of the host materials. Because of distinct advantages (EMI immunity、high sensitivity、 multiplexing capabilities etc) over traditional sensors, FBG sensor is regarded as one of the most promising candidates for application in smart health monitoring. Prohaska