In a high-speed, long-haul, fiber-optic communication system, fiber dispersion can cause serious performance degradations. Here, we describe an optical equalizer consisting of a reflective cavity structure, which gives an all-pass amplitude response and a frequency-selective delay response. In [2], we used computer simulations to assess the performance of the equalizer in the presence of laser chirp (direct modulation). Here, we evaluate equalizer performance for links using external modulation, in which case chirp is absent. We show that, by using equalizers of the type described, the receiver data eye can remain open for distances more than twice those where the unequalized system becomes inoperable. © 1990 IEEE