Abstract: Circuitry for the generation and synchronous detection of optical pulsed signals contaminated by additive background noise characterized by a high signal-to-noise ratio. The circuitry comprises a source for generating optical pulsed signals, a detector for generating detector signals in response to the optical pulsed signals, and a signal processor for processing the detector signals in synchronism with the optical pulsed signals. The signal processor for processing the detector signals includes a high pass filter, an integrator and at least one switch synchronized with the optical pulsed signals for driving the integrator. The circuitry is preferably under computer control.