Fiber Assembly of MEMS Optical Switches With U-Groove Channels

A key process in assembly of microelectromechanical systems optical switches is of inserting fibers into U-grooves in silicon substrate. Due to positioning errors and dimensional tolerances in components, heavy collision occurs between fibers and the edges of U-grooves during insertion, throwing out fibers from the fiber holder or worse, damaging the components. Typical solutions to the problem involve determining errors using machine vision or force sensors, and then positioning fibers accurately by virtue of high precision multi-axis systems (with submicron repeatability). However, these approaches are costly and difficult to implement. In this paper, we present a low-cost passive assembly method to solve the problem. It utilizes a special flexure-based fixture to regulate high contact forces and accommodate assembly errors. Specifically, we model the problems happening in the process of fiber insertion and characterize the conditions of successful insertion. We then suggest how to design flexural fixtures so that the required insertion conditions can be met. Experimental results show that using such a fixture the fiber assembly can be successfully implemented even if the assembly system's accuracy is lower than 12 in and axes, and 0.07 in theta axis. These requirements are within the reach of most low-cost precision systems.