Scientific-Atlanta, Inc.

Antec, Incorporated

Other

Dogan A Atlas

Rezin E Pidgeon, Jr

Frank R Little

A method for transmitting broadcast and narrowcast services in a system having a headend, a hub connected the headend, and a plurality of nodes connected to the hub. Instead of transmitting the signals directly from the headend to each node, the signals are transmitted from the headend to the hub. The signals transmitted from the headend to the hub include both broadcast services to be transmitted to each node and narrowcast services to be transmitted only to predetermined targeted nodes. The broadcast and narrowcast services are transmitted by optical signal beams operating at different wavelengths. Subscribers can transmit signals to the headend, via each node, on the reverse channel. The reverse channel information from subscribers is combined at each respective node into a single wavelength for each node. The narrowcast services are added at the headend instead of at the hub. By adding the narrowcast services at the headend, the processing of the narrowcast signals is performed by the electronic processing equipment at the headend. Therefore, the narrowcast signals leave the headend as optical signals, and the hub is only required to perform optical signal processing, and is not required to have any electrical processing equipment. In this manner, the hub performs only optical signal processing, which reduces the complexity and cost of the system.

Optical network for transmitting two-way multicast signals

A system and method for reducing Raman cross-talk between optical signals having different wavelengths in an optical communications system. Optical signals having wavelengths &lgr;,, &lgr;,, &lgr;,, and &lgr;,, respectively, are launched into an optical fiber at the headend of the system by an optical transmitter. Each wavelength &lgr; is preferably separated from each adjacent wavelength by the same amount, &Dgr;&lgr;. &lgr;,and &lgr;,have vertical polarizations and &lgr;,and &lgr;,have horizontal polarizations. Because there is no Raman cross-talk between orthogonally polarized optical signals, there will be no Raman cross-talk between &lgr;,and &lgr;,, between &lgr;,and &lgr;,, between &lgr;,and &lgr;,, or between &lgr;,and &lgr;,. However, there is Raman cross-talk between &lgr;,and &lgr;,because each is vertically polarized and also between &lgr;,and &lgr;,because each is horizontally polarized. The amount of Raman cross talk is minimized because the wavelength difference between vertically polarized signals &lgr;,and &lgr;,, and also between horizontally polarized signals &lgr;,and &lgr;,, is only &Dgr;&lgr;, which is the smallest wavelength difference between adjacent optical signals.

System and method for reducing Raman cross-talk in a DWDM transport system

A system for amplifying separate optical signals traveling in a forward path and a reverse path over an optical communications system used for CATV program distribution. A first and second optical circulator, each having a first, second, and third port, are connected to respective opposite sides of a bi-directional amplifier. The first port of the first circulator inputs a first optical signal traveling in the forward path. The second port of the first circulator is coupled to an input/output port of the amplifier. The third port of the first circulator outputs an amplified second signal traveling in the reverse path. The second circulator is similarly connected to the side of the amplifier. A first and second signal/signal WDM coupler, each having a pass port P, an add port A/D, and a common port C, are coupled to the first and second optical circulators, respectively. The first port of the first optical circulator is connected to the pass port of the first signal/signal WDM coupler, and the third port of the first optical circulator is connected to the add port of the first signal/signal WDM coupler. The common port of the first signal/signal WDM coupler outputs an amplified second path signal and inputs a first path signal. The second signal/signal WDM coupler is similarly connected to the second optical circulator and outputs an amplified first path signal and inputs a second path signal. In this manner, the present invention provides bi-directional amplification of signals traveling in opposite paths on a single fiber communications link.

Optical amplifier for CATV system with forward and reverse paths

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 modulator for a high power laser transmitter includes a laser source coupled through a phase modulator to a signal modulator. A noise source provides a band limited noise signal to either the laser source or the phase modulator or both. Alternatively, an optical modulator for a high power laser transmitter includes a laser source providing a laser output optical signal and a phase modulator. First and second continuous wave signals at respective first and second frequencies are combined to modulate either the laser source or the phase modulator. The first frequency is different than the second frequency. The laser and phase modulation produces a broadened optical output signal such that the broadened optical output signal is characterized by beat frequencies harmonically related to the first and second frequencies. The modulation bandwidth includes no significant beat frequencies. Each of the multiple beat frequencies produced has a correspondingly reduced amplitude but has the same laser line width, thus increasing the power that can be injected into the fiber before the onset of stimulated Brillouin scattering.

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Duluth, GA, United States of America

Dogan A Atlas