Monolithic 1*19 single-mode fused fibre couplers

The theory and performance of monolithic 1*19 single-mode fibre couplers are presented. The devices are fabricated using fused-fibre technology with the 19 fibres held in a cylindrically symmetric array by a close fitting glass capillary tube. The coupling response of the devices differs depending on the degree of fusion of the structure selected during fabrication. Results from two devices having different degrees of fusion are presented, demonstrating single wavelength operation with good coupling uniformity over all 19 output ports, and dual wavelength operation with equal splitting over 18 output ports and a higher power remaining on the central, input fibre.