Characteristics analysis of wavelength-division-multiplexing fiber couplers fabricated with a microheater

Optical properties and taper profiles of 1.3l/l.55-µm wavelength-division-multiplexing (WDM) fiber couplers have been experimentally analyzed. A newly developed microheater was used for the fabrication in air. The elongation lengths were controlled so that the fourth coupling peak would reach the 1.55-µm wavelength. The wavelength difference Δλ between the peak coupling wavelength of 1.55 µm and that around 1.31 µm decreased linearly at each fusion temperature with the fusion time. At each fusion temperature, the Δλ value decreased linearly with the elongation length and decreased exponentially with the neck width. The Δλ value and the taper shape at the minimum limit of the degree of fusion were estimated. The fabrication condition and the taper shape for 1.31-µm and 1.55-µm WDM coupling were also analyzed.