An ultrafast switching technique utilizing the optical Kerr effect in optical fibers is described and its switching characteristics are considered, taking into account chromatic and polarization dispersion. Experimental results on picosecond optical Kerr modulation and 2 Gb/s all-optical complete demultiplexing of a 30 ps probe pulse train, as well as all-optical chirping manipulation of ultrashort optical pulses, are presented. Applications of the optical Kerr switching technique to the determination of the nondiagonal component n281 ofthe nonlinear refractive index in nonlinear optical media and to the generation of ultrafast pulse trains are also discussed.