A fiber optic communication system for transmitting signals from a plurality of spatially distributed subscriber transmitters to a central office. Each of the transmitters have a digital data source, a phase modulator, a coherent optical transmitter operating in continuous-wave mode and a biasing circuit to bias the coherent optical transmitter into its linear operating region, such that the coherent optical transmitter transmits light at a first wavelength, intensity modulated by the phase modulated data output within the linear operating region. Each transmitter may also be used to time division multiplex the actual data onto the fiber optic cable. Furthermore, the transmitters may also be grouped into a frequency division multiplexing scheme without the need for expansive, specifically-designed filters. The central office includes at least an optical receiver and phase demodulator. In a frequency division multiplexed scheme, the central office may also include the basic filter.