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The optimum conditions for arc-fusion splicing of single-mode fibers with core eccentricity of a few microns are investigated in detail. A narrow, quick fusion method, where the fiber-fused region is restricted by the narrowing of the electrode gap and the arc-discharge time is short compared with the conventional multi-mode fiber splice, is presented that will reduce the surface tension effect. The optimum values of electrode gap, prefusion time, and discharge duration are found to be 0.7 mm, 0.2 sec, and 1 sec, respectively, when the discharge current is 18 mA. The optimum pressing stroke of a fiber after the fiber end faces contact each other is determined to be 20 microm. Splice loss <0.1 dB is achieved in the present conditions for fibers with 2-microm core eccentricity and +/-3-microm o.d. discrepancy.

Operation of a fiber-optic logic gate is demonstrated for the first time. The principle of operation is based upon the intensity-dependent polarization rotation in birefringent fibers. Using a birefringent fiber combined with polarizers in the crossed state, the ON/OFF state of an AND operation is clearly observed with an extinction ratio of approximately 10 dB. The fiber-optic logic gate would be a promising device for optical information processing in the future because of the feasibility of compact configuration and very fast-speed operation.

An all-fiber optical Kerr shutter consisting of a short single-mode fiber and a highly birefringent fiber which serves not only as a polarizer but also as a wavelength filter to reject pump light is successfully realized. By utilizing the Kerr shutter, optical sampling is demonstrated. Time-varying signal light from a laser diode at λ=0.84 μm is sampled into a train of pulses through the Kerr shutter which is driven by an intense light pulse at λ=1.064 μm. The applications to high-speed signal processing and the generation of picosecond optical pulse are promising because of the fiber’s fast response of optical Kerr effect.