Large wavelength shifts in UV-exposed 3 dB and WDMfused taper fibre couplers

The spectral response of 3 dB and 1300/1550 nm wavelength division multiplexing fused taper fibre couplers can be shifted by over 100 nm by exposing the entire coupler with intense UV light at a wavelength of 193 nm and without prior hydrogenation. There is no discernable increase in excess loss. The major contribution to these shifts for these couplers originates in the down- and up-taper regions.