Single-mode fused biconical coupler optimized for polarizationbeamsplitting

A single-mode fused biconical coupler for polarization beamsplitting is described. In the coupling region, standard communication fibers are used. The output fibers are polarization-maintaining. To stop the coupler drawing process accurately, the degree of polarization is measured during the drawing and is used as a criterion. Losses of 0.2 dB are typical, and a minimum extinction ratio of -27 dB is achieved. A usable spectral window as broad as 17 nm with an extinction ratio smaller than -15 dB for both output fibers is obtained. Any specified wavelength for the minimum of the extinction ratio is reached within ±3 nm