An optical data symbol detection circuit (90) comprises: - at least one single-photon detection circuit (100) configured to generate trigger events (d1) in response to an incident light signal comprising photons, the incident light signal encoding data symbols; - a reference signal generator (105) configured to provide a reference demodulation signal (Vdemod); - a discrimination mechanism (125) configured to identify trigger events based on their temporal alignment with the reference demodulation signal (Vdemod); and - at least one correlation system (126) configured to adjust the contribution of each identified trigger event to an output signal (Vsymbol) based on its synchronization with the reference demodulation signal (Vdemod).