Optical data communications receiver

Optical data receiving apparatus comprises a photo detector 1 which generates electrical pulse signals representative of pulses of light received by said photo detector. A pulse stretcher 4 coupled to the photo detector 1 receives the electrical pulses and selectively increases the length of the electrical pulses to a minimum predetermined temporal length. A threshold generator 5 generates a detection threshold equal to the average amplitude of the electrical pulse signals received from the photo detector (1) multiplied by a predetermined scaling factor. Comparator 6 receives on a first input the output of pulse enhancer 4 and on a second input to the output of amplitude scaler 5 and generates an output signal pulse when the stretched pulse signals have an amplitude which is greater than the detection threshold. This facilitates interoperability of systems which use a different pulse length and/or amplitude.