Methods for fine-tuning the wavelength response of single-mode optical-fibre taper filters

The effect of twisting and longitudinal strain on the wavelength response of taper coaxial coupler filters is examined. Both effects permit the fine-tuning of the wavelength response of the single fibre filters, but we demonstrate that a combination of twist and strain is preferred, as it is possible to eliminate residual birefringence present during the fabrication of such filters.