Abstract: A communications system includes forward and reverse paths. Reverse path circuitry within an optical node of the system receives reverse analog electrical signals from subscriber equipment and generates therefrom a multiplexed reverse digital optical signal. A coupling node combines digital optical signals and/or RF signals from an optical node or from coaxial cable, respectively. The combined digital optical signal is transmitted over a fiber optic cable to a cable television hub, the reverse path portion of which includes no active circuitry. The hub multiplexes the digital optical signal with other digital optical signals from other nodes to generate one or more forwarded digital optical signals at a hub output, wherein generation of the one or more forwarded digital optical signals requires only passive devices in the reverse path of the hub.

Abstract: A communication system, such as a cable television system, includes an optical transmitter (FIG. 2) that includes adaptive predistortion control circuitry (104). The adaptive predistortion control circuitry (104) measures the distortion produced by television band signals processed in the communication system. In the optical transmitter (FIG. 2), the distortion signal produced by the television signals is a relatively high-level signal from which necessary predistortion control signals may be more easily processed. Additionally, the adaptive predistortion control circuitry (104) detects both the amplitude and the polarity of distortion within the optical output (FIG. 2) of the optical transmitter, which enables the control circuit (104) to determine the correct polarity and level adjustments that should be made to the predistorter (102) included in the optical transmitter.

Abstract: A postdistortion network for a receiver at a receiver location in an optical transmission system is disclosed. The receiver converts an optical signal carried over an optical transmission link to an RF signal. The postdistortion network includes an input terminal for receiving the RF signal and a distortion generator for generating a distortion signal from the RF signal. An adjusting circuit for adjusts the phase and amplitude of the distortion signal based on distortion at said receiver location. The adjusted distortion signal is combined with the RF signal in order to cancel or substantially suppress distortion in the RF input signal. The present invention permits individual receivers in an optical transmission system to be compensated for distortion which may be unique to that receiver location. A communications system including a predistortion network and a postdistortion network is also disclosed.

Abstract: A receiver is described for optical signals which are amplitude modulated with broadband radio frequency signals. The receiver includes an optical detector which receives the incoming optical signal and generates a radio frequency electrical signal which varies with the power level of the incoming optical signal. This electrical signal is applied to a pair of amplifiers which are connected in a push-pull relationship. A gain control circuit controls the gain of the amplifier pair.

Abstract: A predistortion circuit for an optical communications system includes a main path and a predistortion path for an RF modulating signal which are independently level adjusted and impedance matched to a laser diode. The distortion path includes a distortion generator which generates a distortion signal which is substantially the same as the distortion generated by the modulation of the transmission system. The distortion path further includes an in phase adjustment leg for overall amplitude adjustment and amplitude adjustment as a function of frequency and a quadrature adjustment leg for phase adjustment as a function of frequency. Temperature compensation is provided to the adjustment networks to stabilize the gain elements of each for ambient temperature changes.

Abstract: A receiver is described for optical signals which are amplitude modulated with broadband radio frequency signals. The receiver includes an optical detector which receives the incoming optical signal and generates a radio frequency electrical signal which varies with the power level of the incoming optical signal. This electrical signal is applied to a pair of amplifiers which are connected in a push-pull relationship. A gain control circuit controls the gain of the amplifier pair.