Finisar Corporation

Finsar Corporation

Gerald Francis Sage

Frank H Levinson

Arthur Michael Lawson

Willem A Mostert

Randy Ichiro Oyadomari

A device for and a method of decreasing the data rate of a digital return path link in a Cable Television Hybrid Fiber-Coax system (CATV system) is disclosed. At the node of the CATV system, the bandwidth of the a digital data stream representative of an analog return signal is limited to a desired frequency band. The bandwidth-limited data stream is then digitally re-sampled at a predetermined multiple of a center frequency of the frequency band. The re-sampled data stream is then separated into two data streams. Then, these separate data streams are digitally decimated to a lower data rate, interleaved and serialized for transmission to a head end of the CATV system. A reverse process reconstructs the original analog return signal's signal components within the desired frequency band at the head end.

Bandpass component decimation and transmission of data in cable television digital return path

An apparatus for and a method of transmitting analog return signals in a digital return path of a cable television system (CATV) is disclosed. In one embodiment, at a node of the CATV system, an analog CATV return signal is converted to a stream of digital samples at approximately 100 MHz. Signals outside of a desired frequency band are removed with a digital filter having predetermined filter coefficients. The resulting stream of digital samples is up-sampled to generate another stream of digital samples at a rate that is four times the center frequency of a predetermined frequency band. The resulting stream is then punctured to generate yet another stream with a data rate that is lower than 100 MHz. Zero samples are removed, and the remaining digital samples are serialized and converted to optical signals for transmission via an optical medium of the CATV return path. A reverse process at a hub or head end of the CATV return system restores the signals of the desired frequency band.

Data rate compression device for cable television return path using bandpass puncturing

An optical signal return path system includes a transmitter and a receiver. The receiver receives an optical data signal from the transmitter and recovers therefrom a digital data stream and an associated first clock having an associated first clock rate. The data stream is stored in a memory device at the first clock rate. A clock generator generates a second clock having an associated second clock rate that is adjusted in accordance with a clock control signal. A control circuit reads data from the memory device at a rate corresponding to the second clock rate and generates a fullness signal that indicates whether the memory device is fuller more full than a predefined threshold fullness level. A clock speed adjusting circuit generates the clock control signal in accordance with the fullness signal.

System and method for transmitting data on return path of a cable television system

An efficient means for transmitting digitized return path signals over a cable television return path is disclosed. In one embodiment of the invention, the cable television return path includes a node that receives an analog return signal from a subtree of the cable television system and generates a digital transport signal representative of the analog return path signal. The digital transport signal, however, is not a digitized form of the analog return signal. Rather, the digital transport signal is encoded such that fewer bits are used to represent the analog return signal without substantially impacting the accuracy and dynamic range of the signal. At the hub, the digital transport signal is decoded and converted to produce an analog signal that is a close approximation of the analog return signal.

Efficient transmission of digital return path data in cable television return path

A return path transmitter includes an optical signal receiver configured to receive a digital optical signal and generate therefrom a first digitized RF data stream and a sample clock. The return path transmitter further includes an RF signal receiver, coupled to the optical signal receiver, configured to receive and convert the analog RF data signal into a second digitized RF data stream of digitized RF data samples at a rate determined by the sample clock. The return path transmitter further includes a summing circuit configured to mathematically sum the first and second digitized RF data streams so as to generate a third digitized RF data stream. The return path transmitter further includes an optical transmitter configured to convert an output data stream into a serialized optical data signal for transmission over an optical fiber, the output data stream including the third digitized RF data stream.

A device for and method of combining asynchronous digital return signals from multiple nodes of a CATV return path is disclosed. The signals are digitally filtered, re-sampled at a common output rate and digitally combined (e.g., summed) without being converted to analog form. The combined signal can be provided to an optical data transmitter for transmission over an optical fiber to the head end. Because the device of the present embodiment does not require analog hardware (e.g., converters, D/A converters and analog summers), it is smaller, costs less and consumes less power than conventional CATV return signal combiners.

Asynchronous digital signal combiner and method of combining asynchronous digital signals in cable television return path

An optical signal return path system includes a transmitter having a sample clock generator for generating a sample clock and an RF signal receiver for receiving and converting an analog RF data signal into a first data stream of digitized RF data samples at a rate determined by the sample clock. Supplemental channel circuitry provides a second data stream. A multiplexor receives and combines the first data stream and second data stream, and an optical transmitter converting the combined data stream into a serialized optical data signal for transmission over an optical fiber. The second data stream may contain maintenance data reflecting an operational state of the transmitter. A receiver receives the optical data signal and recovers therefrom a digital data stream and an associated first clock having an associated first clock rate. The data stream is stored in a memory device at the first clock rate. A clock generator generates a second clock having an associated second clock rate that is adjusted in accordance with a clock control signal. A control circuit reads data from the memory device at a rate corresponding to the second clock rate and generates a fullness signal that indicates whether the memory device is more full than a predefined threshold fullness level. A clock speed adjusting circuit generates the clock control signal in accordance with the fullness signal.

A Cable Television (CATV) digital return link system that provides dedicated, high-speed, full-duplex and point-to-point connections between users and the head end system is disclosed. The CATV digital return link system includes return path transmitters, intermediate hubs and a head end hub coupled to each other via a network of fiber optics cables. The return path transmitters are each coupled to a relatively large number of users via a local CATV-subtree. Signals from cable modems are transmitted via the local CATV-subtree to the return path transmitters for transmission to the head end. A number of users are individually and directly connected to the return path transmitters. Data from these directly connected users is transmitted to the head end via the network of fiber optics cables in conjunction with the RF data from the subtree. Likewise, data from the head end to these directly connected users is transmitted in the forward path direction using the digital return link system.

Growing community of inventors

Chico, CA, United States of America

Gerald Francis Sage