A large-tolerant single-mode optical fiber coupler with a tapered structure

An efficient and large-tolerant single-mode optical fiber coupler with a tapered structure is fabricated and studied experimentally. The maximum coupling efficiency of 95 percent and the tolerance in the coupling length of 2.5 mm permitting the coupling efficiency of more than 90 percent are obtained experimentally. The approximate analysis based upon a coupled mode equation is developed using a step transition model in order to describe the basic principle of this coupler.