Quasi-Axial GRIN Lens Implemented in Wedge-Shaped Fiber Coupling With InP-Based PLC

A 3-D equivalent rectangle approximation staircase concatenation method to analyze the optical mode evolution in a wedge-shaped fiber (WSF) is proposed in this paper. A scheme with an axial gradient-index (AGRIN) lens between the WSF and InP-based planar lightwave circuit (PLC) chip, yielding higher transmission efficiency than those with two cascaded lenses and one radial GRIN lenses, by 2.282 and 7.816 dB, respectively, is devised and experimentally demonstrated. The WSF-AGRIN-PLC-single-mode fiber coupling linkage supplies a preferable solution for solving the problem of index mismatching in fiber-to-InP-based PLC assembly to achieve a high-efficiency connection.