Study On Sensing Characteristics Of Grating Written In Polarization Maintaining Fiber

In this paper, the characteristics of polarization maintaining fiber grating(PMFG) are mainly introduced, such as birefringence,temperature,strain and so on. As the birefringence characteristic of PMFG, the spectrum of reflected wave has two peak values.The analyzes of theory in this paper have three parts. Firstly, analyzing the three different structures of polarization maintaining fiber, such as panda model,tie model,ellipse model. From the results of simulation, the important parameters are found which the birefringence value changed when they have different values. Secondly, taking advantage of Coupled Mode Theory, the reflection spectrum expression of Fiber Bragg Grating (FBG) can be derived. Ignoring the coupling of the two polarization models, then the reflection spectrum of PMFG can see as the sum of two different FBGs. Thirdly , through the reflection spectrum expression of PMFG and others theories , using the Matlab software for simulating, the characteristics of the reflection spectrum are found.The characteristics of the fiber Bragg grating (FBG) fabricated in the PMF are analyzed by experiments. The experiments for the PMFG at temperature range from 20℃to 80℃and strain range from 0μεto 1100μεare measured. From the results of temperature experiment, with the temperature increasing, we can see that the value of the wavelength of the spectrum of reflected wave will increase but the space between the two peaks will decrease. From the results of strain experiment, with the strain increasing, we can see that the value of the wavelength of the spectrum of reflected wave will increase but the space between the two peaks will not change basically.