Optical switching using a nonlinear optical loop mirror, which exploits unequal nonlinear phase shifts acquired by linearly and circularly polarized solitons that counterpropagate the loop, is investigated. The device totally reflects small amplitude light waves and transmits maximally switched soliton-like pulses nearly completely. The device works for a fiber loop of birefringence of less than 10(-8) and pulses of width of the order of a few hundred femtoseconds. (C) 1998 Elsevier Science B.V.