Design of Long-Period Grating Couplers Based on Asymmetric Dual-Core Fibres

Abstract

We demonstrate a grating coupler using an asymmetric dual-core fibre with a pair of long-period gratings (LPGs). Simple formulas for the achievement of high coupling efficiency are derived and the results are compared with reported LPG couplers based on two discrete fibres. Our results show that with a proper choice of grating parameters, the coupling efficiency reaches 100%. A passing band with steep band transitions and side lobes less than ~25 dB can be achieved.