Taper Device for Tolerant Coupling of Free-Space Optical Beams Into Single-Mode Fiber

A new device for improving the free-space optical monitoring and coupling into a single mode fiber is proposed. It consists of a fiber taper, which can easily be drawn from a suitable fiber with large core radius. The taper acts as a mode filter discarding higher order modes. A first device is fabricated. Measurements show that lateral tolerances increase linearly with the taper input core radius and longitudinal tolerances increase with the square of the input core radius.