Research On The Polarization Of Linearly Chirped Fiber Bragg Gratings

Linearly chirped Fiber grating is a key optical component in the optical fibercommunication and optical fiber sensing systems, and it be widely used in the opticalfiber systems. As most of the optical Linearly chirped fiber grating are lateral written,and the optical source which used in write system there are also have correspondingpolarization properties, most of the Linearly chirped fiber gratings have a certainamount of birefringence, and the presence of birefringence caused the performance ofpolarization properties of fiber gratings out. With high-speed optical fibercommunication and fiber sensing technology, rapid development, the polarizationproperties of fiber grating more and more important.In this paper, Linearly chirped fiber Bragg grating as the research object, the use ofcoupled mode theory and Transfer matrix method, the polarization and optical devicetest system of LCFBG polarization related properties of theoretical and experimentalresearch carried out.Firstly, in this paper, the necessary optics polarization content and thecoupled-mode theory, and uniform FBG polarization characteristics systematicallyanalyzed, including transmission and reflection of Stokes parameter, polarizationdependent loss and difference group delay and so on.Secondly, this paper deeply studies the wavelength dependency of polarizationdependent loss in reflection in uniform FBGs written in single mode fibers. Theinfluence of the grating parameters on the polarization dependent loss are analyzed, andthe influence of fiber grating analysis shows that the polarization dependent loss inreflection in uniform FBGs are directly depend on the grating birefringence quantity,grating length and grating depth of the modulation.Finally, this paper studies the reflected polarization dependent properties ofLCFBG with change the temperature. As the temperature has a very small influenceupon the grating’s birefringence, especially the low birefringence LCFBG. and weakbirefringence LCFBG’s polarization properties of the response to temperature than thecorresponding wavelength shift with the outside of the invariance. LCFBG’s PDL,DGD,and Stokes were measured in room temperature and with temperature changes. And further measures the PDL, DGD, Stokes of LCFBG with the change in temperaturecharacteristics. The results obtained from the test of the polarization of the LCFBGrelated properties with temperature change is spectrum form the whole mobile, And justthe overall with the rise of temperature wave direction to translation，And of the spectrallines drift and the change of the temperature also exist between good linear relationshipbetween. Obtained from the test results can be used in the LCFBG reflection PDL toimprove the accuracy of temperature of LCFBG.