Plastic-optical-fiber joined Optical Coupler and Distribution Ratio Prediction by Ray Tracing.

Abstract

It is necessary to connect cores of two optical fibers mutually and to compose an optical window between fibers for distributing the optical signal. The ultrasonic fusion technique enables physical joining through instantaneous fusion of junction boundary surfaces, so one of its distinctive features is that it does not cause deformation or other physical changes at areas outside the junction. Therefore, it is predicted that optical signals come and go between the joined fibers with no change in the propagation mode. In this report, the optical window and area were varied and optical characteristics were evaluated, while controlling ultrasonic fusion conditions. The distribution ratio was predicted from the joined structure using the geometrical ray tracing method, and the predictions were compared with experimental results. The optical ray propagation was calculated for 104 to 105 incident rays, and the results matched well with experimental results, thus showing that ray tracing using simple geometrical calculation is useful in predicting the distribution ratio. In parallel joined type optical couplers formed via ultrasonic vibration, the splitting ratio precision can be adjusted from 6 dB to 1 dB by varying the joined area, while maintaining low insertion loss. Equal distribution, however, cannot be achieved.