Scissors Fiber Bragg Grating Packaging And Low Temperature Sensing Device

Fiber Bragg gratings(FBGs) have been applied greatly in the fiber communication and sensor fields. However, the wavelength of the FBGs will shift when the temperature changes, which can not be accepted in practical applications. One aim of the paper is to study a novel forficiform packaging of fiber grating to compensate for the thermal effects.Cryogenic sensors in the low temperature environment of -196℃- -40℃ have been used in a wide range of fields such as energy, military project, space technology, life science , and so on. How to get high-sensitivity cryogenic temperature sensor is a difficult problem, FBGs can be well used as temperature sensors, but the characteristics of fiber and fiber grating in cryogenic temperature are different with those of normal temperature. The other aim of the paper is to study the characteristics of fiber and fiber grating and apply the forficiform device in cryogenic temperature sensors. Thus, the novel forficiform device can be for both temperature-compensating package for FBGs and cryogenic temperature sensors.Low temperature optics is proposed firstly, and the characteristics of fiber and fibergrating are studied systematically; Our data show that the increase in the thermal stress at the cladding/coating interface adequately reflects the experimentally observed in -crease in the added transmission losses at low temperature; the shift of wavelength of FBGs in the cryogenic temperature is also studied.A novel forficiform packaging of fiber gratings is proposed. The new packaging method keeps the compact form of a fiber grating and does not require any pre-loading stress. In the range of -30℃ to 80℃, the sensitivity of the Bragg wavelength to the temperature is reduced more than 10 times and reaches 0.001nrn/℃. The range of tuning for the Bragg wavelength can be expanded by adding a piece of piezoelectric ceramic.The novel forficiform device is applied in cryogenic temperature sensors, thetemperature precision can be improved by the change of ratio of arm length of theforficiform device.Liquid nitrogen thermodetector is developed for studying the characteristics of fiber and fiber grating in cryogenic temperature, which offers a low temperature environment. Infrared sensor is applied in the liquid nitrogen thermodetector, physical shape change of the fiber can be observed in the real time.This study puts emphasis on the application in packaging of fiber grating and cryogenic temperature sensor of the forficiform device. In the range of -30℃ to 80℃, the sensitivity of the Bragg wavelength to the temperature is reduced more than 10 times and reaches 0.001nm/℃. The temperature sensitivity of the forficiform device is 0.03nm/ ℃ at -196℃ when an aluminum substrate is used, 0.051nm/℃ at -196℃ when a poly(methyl methacrylate) substrate is used and 0.08nm/℃ at -196℃ when the fiber Bragg grating was bonded between two Teflon substrates.