An optical fiber emulator. The emulator receives a digitally-encoded optical signal; demodulates the optical signal to produce serial electrical pulses representative of the digital signal; converts the serial pulses to parallel pulses; propagates the parallel pulses through a shift register whose propagation time is less than or equal to the time of a length of fiber to be emulated. The emulator then converts the parallel pulses at the output of the shift register to serial pulses; modulates an optical carrier with the serial pulses from the shift register; and attenuates the modulated optical signal an amount corresponding to the length of the fiber being emulated to produce an output optical signal whose propagation time is substantially equal to that of a section of optical fiber to be emulated. The shift register may be tapped at any point to obtain an output delayed by a desired amount corresponding to a selected section of optical fiber.