Passive Alignment of Optical Fibers in V-grooves with Low Viscosity Epoxy Flow

Abstract

Optical fibers are one of the most commonly used light transmitting media in optoelectronic systems for telecommunication applications. Because the core diameter of optical fibers is very small, active alignment methods are usually employed for the coupling between optical fibers and other optoelectronic devices. In general, the equipment cost of active alignment is very high and the processing time is relatively long, especially for fiber array alignment. Therefore, the conventional fiber alignment process becomes rather expensive and the throughput is quite low. In recent years, passive alignment using low cost epoxy adhesives and precisely etched V-grooves on silicon optical benches is attracting more attention due to its reduced production cost and short processing time. During the passive alignment process, the optical fiber may be lifted up by the buoyancy of epoxy flow and, hence, an extra cover plate is required to press the fiber against the walls of the V-groove. An effort is made to develop a modified passive alignment method without using the cover plate. Several parameters may affect the yield and need to be optimized. It is found that the amount of epoxy dispensed to the V-groove is critical in the process. Also the viscosity of the epoxy determines the characteristics of the flow in the V-groove and, hence, affects the results of passive alignment. In this chapter, the design and configuration of the modified passive alignment method will be introduced. The effect of the volume and viscosity of epoxy will be presented. The application to multiple fiber alignment will be demonstrated. The newly developed passive alignment method is capable of aligning an array of 8 fibers up to 1 micron accuracy.