Polymer optical fiber coupler fabrication using chemical etching and lapping technique

Development of a polymer optical coupler using lapping technique integrated with contact mechanics and couple mode theory is proven where the initial procedure of fabrication is explained. Procedure of the fabrication includes etching process where a harmless chemical solvent, acetone, is used in order to remove the cladding layers gradually in accordance to the etching rate. The exposed region of the core is then aligned with another similar strand of fiber. The bending radii or bending angle is determined using particular size of circular blocks. Several experiments using different etched rate fibers attached to circular blocks having the same radii is demonstrated to investigate the output power and insertion losses of the developed coupler. Although in this initial study, the measurement parameters values shows unattractive results, however, the fabrication of couplers using this lapping technique is proven.

I. INTRODUCTION

One of the most recent coupling technologies using POF is Y-branch coupler based on acrylic block with high-index contrast waveguide taper [1]. In this study, a directional coupler is fabricated with integration of several important technique and concepts, i.e. tapering and macro-bending. Some known works such as couplers have been developed decades ago using heating and pulling method or known as fused coupler [2]. An alternative method of fabricating a multimode fiber coupler has been demonstrated by Ogawa [3] and McCormick [3] where two unclad fibers are placed in a acrylic base side by side. Important concept in this fabrication is that the unclad region of the fiber increases the influence of the evanescent field which then assists the coupling process. In this study, acetone is used to etch or taper a certain length of the fiber as an initial procedure to fabricate the coupler which consists of two parallel fibers brought in close proximity at a certain length, which this method is known as lapping technique. Merchant [4], Scully [4] and Schmitt [4] has already demonstrated a quite similar but different technique where the fibers are embedded into a plastic material and the surface is polished until the cladding is removed 80%. This technique resulted in better coupling length than fused-taper method [4].