Abstract: A fiber optic communication system provides parallel paths to enable cancellation of even order harmonic distortion components. A pair of parallel optical fibers is provided. Each of the fibers is coupled to a corresponding transmitter at one end of the pair and to a corresponding receiver at the other end of the pair. The transmitters are modulated with an input signal applied to the transmitters at a 180.degree. phase differential. The 180.degree. phase shifted signals are combined at the receivers to recover the input signal while cancelling even order distortion products introduced by the transmitters. A method is provided for balancing the system upon installation.

Abstract: Method and apparatus are provided for transmitting, receiving, and reproducing digital audio signals as discrete carriers similar to standard FM broadcast signals. An audio signal is digitized using, for example, adaptive delta modulation techniques. Several channels of audio information, such as left and right stereo channels and a second audio program ("SAP") channel can all be digitized and incorporated onto the digital broadcast signal carrier. The digitized audio signal may be modulated using multiphase modulation of the carrier of an FM broadcast band signal. A plurality of audio channels may be digitized and transmitted over the airwaves, or over a cable transmission network. Channels of nondigitized audio channels may be interspersed with the digitized audio channels. Source material for the digitized audio channels may be provided to a cable headend over the cable transmission network outside the FM band, and rebroadcast over the cable transmission network in the FM band.