Study On Fabrication Of Fiber Bragg Grating And Temperature Compensation

Fiber Bragg grating (FBG) is one of the optical fiber passive devices which have great development in recent years. As having advantages of small volume, light weight, low insertion loss, FBG has brilliant prospects in fields of fiber communication and sensing. The variation of Bragg wavelength to temperature and strain can cause the problem of cross sensitivity in one parameter measurement. And there is also a strict demand for wavelength stability of FBG in fiber communication field. Therefore, studying temperature compensation methods for FBG is very necessary and has far-reaching significance.Based on the photosensitivity mechanism, hydrogen is loaded in single mode optical fiber, FBG is fabricated using the method of phase mask, and the temperature and strain characteristics of FBG are analyzed.On the basis of investigating the principle of temperature compensation for FBG and doing many experiments and theoretic calculation, a effective passive temperature compensation method is demonstrated. A reasonable structure using two materials with different thermal expansion coefficient is designed. Two ends of the tensioned fiber Bragg grating are attached to the organic glass with epoxy resin. The strain is progressively released as the temperature rises, which compensates the temperature dependence of the Bragg wavelength. The central wavelength of FBG has a shift of 0.79nm when temperature varies form -19℃ to 60℃ before compensation, the temperature coefficient is 0.0nm/℃. While it reduces to 4.43*10~-4nm/℃ after compensation, and the temperature stability of FBG has an increase of a order magnitude accordingly. The influence of prestrain to compensation effect is given and the effects of single side package and double sides package are compared. The reason of undercompensation and overcompensation are also analyzed. Furthermore, the temperature compensation methods based on NTE (Negative Thermal Expansion) material is discussed and the experiment results are analyzed.The temperature compensation structure has the advantages of small volume, easy to be fabricated, and it can meet the demand of temperature stability in the communication system.