Scientific-atlanta, Inc.

Frank R Little

Rezin E Pidgeon, Jr

Leo J Thompson

Herman A Kruse

John G Megna

James O Farmer

Leo Montreuil

Lamar E West, Jr

Joseph Graham Mobley

Dogan A Atlas

William P Lafay

Heather H Rand

Frederick T Zendt

Anatoly Kozushin

Don E Frymyer

Christopher P Lewis

Lamar E West

A distortion circuit for linearizing third-, fifth- and seventh-order distortion components in a non-linear optical communications system includes at least one group of series connected diodes coupled to a common input terminal for receiving a signal source at one end and to an inductor and a capacitor at the other end, a resistance coupled to the common input terminal and a bias source for providing a bias current to the group of series connected diodes. The distortion circuit may be implemented as a predistortion circuit in the headend of the optical communications system or as a postdistortion circuit at the receiving end.

Linearization enhanced operation of single-stage and dual-stage

An optical communications system including a plurality of modulated radio frequency carriers which span more than an octave in bandwidth. In one implementation, the carriers are grouped into ranges which span less than an octave in bandwidth and the individual groups are transmitted over unique optical links. In another implementation, the groups are multiplexed on one optical link by using different wavelengths. In still another implementation, several of the bands are up-converted to the highest band of interest and then transmitted, either over single or multiple links. The resulting optical signals are demodulated and then down-converted before they are recombined into the broadband signal in excess of an octave in bandwidth.

Method and apparatus for transmitting broadband amplitude modulated

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.

Push-pull optical receiver having gain control

An optical communications system provides optical signals of different wavelengths over an optical fiber having a zero dispersion wavelength. Electrical dispersion compensating elements independently compensate optical signals having wavelengths different than the zero dispersion wavelength for dispersion in the optical fiber. Limiting radio frequency signals for modulating a light emitting device or laser outputting signals at a wavelength different than the zero dispersion wavelength to less than one octave of frequency permits second order harmonic distortion resulting from dispersion in the fiber to be filtered at a receiving location. The optical communications system may include a reverse transmission path.

Optical communications system for transmitting information signals

A system for signal level control in AM fiber systems is provided. The system provides level controls at both transmitter and receiver ends of the fiber transmission system, utilizing compensation and control techniques at each end to maintain and optimize the performance of the system. The transmitter includes two stage level control based on a composite power level of a detected RF signal. The receiver includes two stage level control based on a pilot channel filtered from the channels transmitted to the receiver.

Signal level control circuitry for a fiber communications system

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. In a preferred embodiment, a tuning network is connected between the two amplifiers for optimizing the amplification of a selected band of radio frequencies.

Push-pull optical receiver

An optical communications system including a plurality of modulated radio frequency carriers which span more than an octave in bandwidth. In one implementation, the carriers are grouped into ranges which span less than octave in bandwidth and separately transmitted over uique optical links. In another implementation, the groups are multiplexed on one optical link by using different wavelengths. In still another implementation, several of the bands are up-converted to the highest band of interest and then transmitted, either over single or multiple links. The resulting signals are demodulated and then down-converted before they are recombined into the broadband signal in excess of an octave in bandwidth.

Scrambling and descrambling systems utilizing jamming signals provide improved pictures with minimal distortion due to ghosts and artifacts. The television signal is combined with a jamming signal or signals located preferably in the vestigial sideband (VSB) of the modulated picture carrier and at about a null in the spectrum of the modulation of the picture carrier by the horizontal sync. The jamming signal or signals also preferably are placed between the harmonic components of the horizontal sync which define the horizontal sync spectrum and at frequencies which comply with governmental regulations respecting frequency locations of strong signals of CATV purposes. The jamming signals are generated by phase locking to the horizontal sync signals of the television signals or to a submultiple of the horizontal sync frequency. Artifacts are further reduced by preemphasis of the transmitted television signal in the sideband opposite to that in which the jamming signal or signals are located and spaced by an equal frequency increment from the location of the jamming signal energy. In order to extract the jamming signal, so as to descramble the television signal for reproduction in the subscriber's television receiver, a network including at least one surface acoustic wave (SAW) resonator device is embedded in an all-pass network which allows essentially lossless transmission of the television signal spectrum, except for the jamming signal energy and enables that energy to be located close to (e.g., approximately 228 KHz) from the picture carrier in the VSB for enhanced security.

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Alpharetta, GA, United States of America

Frank R Little