Variable coupling ratio Y-Branch plastic Optical fiber (POF) coupler with suspended waveguide taper

Abstract

A variable coupling ratio Y-Branch plastic optical fiber (POF) coupler based on acrylic has been developed. This device utilized two optical designs: a Y-branch structure with a novel suspended waveguide taper and a simple attenuation technique based on lateral displacement of two fibers for the non-symmetrical coupling ratios. The high index contrast waveguide taper is constructed on the acrylic block itself where the area surrounding the waveguide taper has been designed in such a way that it is surrounded by an open air. A simple attenuation technique based on lateral displacement of two adjoining fibers for each of the two output ports has been proposed and presented for the non-symmetrical coupling ratios. Lateral displacement of the fiber is set from 4.4mm down to 1.6mm for output fiber 1 and 0.1mm to 1.0mm for output port 2. Numerical analysis has been done on the lateral displacement of the output fibers which shows the device is able to generate non-symmetrical coupling ratios. Device modeling has been performed using non-sequential ray tracing technique on the Y-branch coupler performing as a 3 dB coupler with an excess loss of 1.84 dB and a coupling ratio of 50:50. The designed coupling ratios vary from 1% to 45% for port 1 and 99% down to 55% for port 2 whereas in the simulated device, ratios vary from 7.65% to 39.85% for port 1 and from 92.35% down to 60.15% for port 2. Fabrication of the device is done by producing the device structures on an acrylic block using high speed CNC machining tool. The fabricated device has an excess loss of 5.85 dB while the coupling ratios are 56.86% and 43.14% when operating as a 3 dB coupler. In thevariable coupling ratio mode, the coupling ratios are 10.09% to 32.88% for port 1 and 89.91% down to 67.12% for port 2. The excess loss of the fabricated device varies from 5.85 dB to 8.49 dB.