Abstract: A relatively simple, low cost apparatus detects the presence and location of faults in an optical transmission system. It is particularly applicable to underwater optical transmission systems. The optical transmission system contains at least one optical fiber pair extending between two terminals. Optical amplifier based repeaters are located at predetermined positions along fibers. Each repeater has a simple high-loss optical loopback circuit which is used to provide fault identification and location. The loopback circuit couples a portion of the optical signal travelling from a transmitting station through one of the fibers, attenuates that portion of the optical signal, and adds the attenuated signal to the optical signal in the other fiber for return to the transmitting station. Fault location is accomplished by launching a supervisory signal into the fiber from one of the terminals.

Abstract: Improved compression of digital signals relating to high resolution video images is accomplished by an adaptive and selective coding of digital signals relating to frames and fields of the video images. Digital video input signals are analyzed and a coding type signal is produced in response to this analysis. This coding type signal may be used to adaptively control the operation of one or more types of circuitry which are used to compress digital video signals so that less bits, and slower bit rates, may be used to transmit high resolution video images without undue loss of quality. For example, the coding type signal may be used to improve motion compensated estimation techniques, quantization of transform coefficients, scanning of video data, and variable word length encoding of the data. The improved compression of digital video signals is useful for video conferencing applications and high definition television, among other things.

Abstract: The present invention relates to an economical yet effective technique for locating and defeating intentional or unintentional interfering signals transmitted to a commercial communications satellite on a channel-by-channel basis. The satellite arrangement includes a first and a second configuration of hybrids and Variable Power Combiners (VPCs), respectively, that concurrently combine the channels received from a plurality of ground regions for delivery to at least one input multiplexer. In one arrangement, the corresponding channel outputs from the at least one input multiplexer, are each connected to a different input of a separate Single Pole Double Throw (SPDT) switch. Channel switching is accomplished by transmitting commands to the VPCs and SPDT switches from a command earth station. Noting the presence or absence of the interfering signal for a given channel switch and VPC setting will provide the location of the interferer and the elimination of the interfering signal.