A system and method that utilizes digital coding techniques to combine a high-rate data stream with a lower rate side data stream to produce a combined data stream in such a way that the side data can be extracted by an inexpensive, low-bandwidth receiver. The method generally comprises the steps of: combining at least one payload data stream with at least one side data stream into a composite electrical data stream; applying the composite data stream to an optical transmitter to produce an optical signal; detecting the optical signal with an optical receiver having a maximum frequency of operation less than one-half of the rate of the composite data stream; and recovering the side data stream from the electrical output of the optical receiver.