Panda Type Polarization Maintaining Fiber Bending Loss

The polarization maintaining fiber is a special optical fiber,which can maintain the polarization condition of the transmitting light wave to be invariable in the optical fiber, so this kind of optical fiber is also called the polarization maintaining fiber,it has widespread applications in optical fiber sensors,optical fiber gyroscopes as well as coherent optical communications and so on,therefore,it becomes very important to carry on a thorough research about the polarization maintaining fiber.In this article,we introduced the principle,characteristics of the high double refraction polarization maintaining fiber,and the basic theories of analyzing and solving the problems about the waveguide.A two-step analysis method is given in this paper, first,the thermal-stress of the panda polarization maintaining fiber is analyzed by using the finite element method,then the detailed stress of the panda polarization maintaining fiber is analyzed according to the photoelastic effect theory,and the double refraction in the optical fiber core is calculated to analyzed the mode of the panda polarization maintaining fiber,also we can calculate the propagation constant of the two polarization mode of the base mode,and get the pattern double refraction.The calculation indicated that:When the stress region is near to optical fiber core section,the pattern double refraction will increase obviously,and we draw out the graph about the relationship between the parameter of polarization maintaining fiber and the section geometry structure by using a mathematics software.By introducing the plate waveguide theory,we emphatically analyzed the bending loss theory of polarization maintaining fiber,and established the seven flat-panel model of the panda polarization maintaining fiber,then solved the Helmholtz equation with the photoelastic effect,we obtained the equation of the bending loss coefficient of the polarization maintaining fiber.Also we got the graph of the relations between bending lossαand the bending radius R.Finally,we examined the bending loss of the single mode optical fiber and the panda polarization maintaining fiber by experiments,and drew the graphs of the bending loss of the polarization maintaining fiber,confirmed that the bending loss coefficient of single model optical fiber and the polarization maintaining fiber is consistent along with the change rules of bending radius and the operating wave length,it means that the bending loss coefficient increases in an exponential form along with the reducing of the bending radius,also with the increasing of the operating wavelength.But comparing with the single model optical fiber,the panda polarization maintaining fiber has a much smaller curing loss coefficient.Comparing the fitted empirical graph with the academic bending loss graph,the two graphs coincide very well.