Novel structure for monolithic fused-fibre 1*4 couplers

A new structure is presented for the fabrication of monolithic 1*4 couplers. The structure consists of five fibres positioned symmetrically in a ring, and therefore lends itself readily to fabrication using capillary clad techniques. A theoretical model describing the coupling in a circular array of five cores is given together with the experimental results from two prototype devices. These devices demonstrate good coupling uniformity at a single wavelength with a maximum insertion loss of 6.74 dB, and a wavelength response optimised at 1400 nm demonstrating insertion losses \n\n\t\t