The paper assesses the feasibility of using reflected downstream light for upstream signalling in a primarily broadcast passive optical network, to eliminate the need for a light source at each terminal. It shows (for a typical CATV network) that using this technique, and by extracting only 1 dB from light power received at the customer's terminal, a mean upstream signalling rate of around 64 kbits/s from 32 terminals is possible. However, this requires full network synchronisation and modulation at the terminals at 2 Mbaud. In practice, the modulation of the reflected light may be limited to perhaps 1 kbaud if a cheap technology is to be employed. Under these circumstances, the maximum data rate is approximately 550 bits/s and is achieved using subcarrier FDMA. The use of subcarrier FDMA has the added advantage of providing completely asynchronous access from all terminals.