Multilevel asymmetric coupler MAC field rotator for LP11 mode in few mode fiber

Abstract

In this work, we present a new design for an integrated optical field rotator for the mode LP11a to the mode LP11b and vice versa using planar Silica over silicon technology. The structure is designed using a Multilayer Asymmetric Coupler. The coupling efficiency of the coupler could be as high as 99% when its length is about 1 mm. For a shorter coupler of length 550 microns and a coupling efficiency of 91%, a complete structure is designed to couple 2 few mode fibers of diameters 15.4 microns through an inverted taper from one side and a Y junction with two inverted tapers from the other side. The fiber to fiber insertion loss of the proposed structure is less than 3 dB over about 190 nm spectral range around 1550 nm. The 3 dB bandwidth of the structure is greater than 360 nm as demonstrated by the Beam Propagation Method BPM simulation.