Fused taper single-mode fiber couplers are readily fabricated with specific spectral properties, including 3 dB splitting in the 1310 and 1550 nm windows, and 1310/1550 nm wavelength division multiplexing (WDM) and demultiplexing. The specific functionality of the coupler is achieved through precise control over the heating and drawing processes. A possible alternative approach to obtaining the required functionality is to use UV- trimming or post-tuning. The spectral response of single-mode fused taper fiber couplers can be shifted by exposing the entire coupler to intense UV light. Furthermore this occurs without any prior hydrogenation, and there is also no discernible increase in excess loss in the exposed couplers. Results will be presented showing the effect of varying both the fluence and the wavelength of the UV-source on the spectral shift of these and other types of couplers. Wavelength shifts of over 100 nm are possible with the 1310/1550 nm WDM couplers, using sufficient fluence. A simple slab model of the complete tapered coupler confirms that the major contribution to the wavelength shift due to the change in the core index originates mainly in the down- and up-taper regions and, to a lesser extent, in the central waist region. This model explains the greater sensitivity of the spectral shift of the more-tapered WDM couplers to UV-irradiation compared to the shift in the 3 dB couplers.

Date Published: 9 June 1998
PDF: 8 pages
Proc. SPIE 3282, Photosensitive Optical Materials and Devices II, (9 June 1998); doi: 10.1117/12.311537

Published in SPIE Proceedings Vol. 3282:
Photosensitive Optical Materials and Devices II
Mark P. Andrews, Editor(s)