Imporvment On The Pulling Processs And The Polarization Dependent Loss Of 1X2 Fiber FBT Couplers

1X2 single-mode optical fiber coupler is a very important passive component,widely used in fiber communication systems,coherent light measurements,sensing systems and other fields.With the rapid developing of the optical fiber technology in various fields,the demands for the 1X2 single-mode optical fiber coupler increase.The polarization characteristic is a significant parameter.High performance of system needs the device with low PDL..Firstly,this paper compares the advantages and disadvantages of several broadband networks.And points out that Fiber to the Home(FTTH) is an inevitable trend.Secondly,this paper analyses the coupled-mode theory and derives the coupling coefficient;Analyses the phase characteristics of the 1x2 single-mode optical fiber coupler. This paper also derives the polarization evolution using the coupled-mode equation.Does research in the polarization characteristics of 1X2 single-mode optical fiber coupler from the concept of degree of polarization,gives the expression of the degree of polarization;and analyses the impact on the degree of polarization which parameters brought.In the third part,this paper compares the FBT process and PLC process.Then points out the application of these two processes.It also introduces the production process of FBT briefly.The forth part of this paper is the focus.One focus is the improvement of the production process,including the way of the cutting fiber ends,the method of inserting adapter to the detector,the way of cleaning fiber,and methord of how to twist fibers;And the improvement of how to modulate the pulling parameters,glue preparation and storage,inner-package,the improvement of fiber yellowing issues.As following,a large number of experiments confirm the higher productivity which the new process brought,also confirm cost saving.The last part is the other focus which analyses the impact which speed brought to the polarization dependent loss(PDL) of single-mode fiber-optic 1x2 coupler.In order to find a suitable speed for the production of dual-window broadband,low PDL coupler,this paper uses online test method to find out the different impact on PDL which brought by diffirent speed.And the results tell us that speed differents,then PDL differents.Finally,this paper points out the best speed,that is,0.18 mm/s for small ratios;0.27mrn/s for big ratios.