An apparatus for converting an input optical signal to an electrical signal. The input optical signal is characterized by a modulation frequency and a modulation wavelength. The apparatus includes a photoconductive switch that is coupled to a photodetector by a common electrode. The photoconductive switch samples the output of the photodetector and is actuated by a switch light signal. The photoconductive switch and the photodetector are arranged such that the switch light signal does not interfere with the optical signal at locations proximate to the electrode and the electrode has a length that is less 0.5 mm.