Digital optical transmitter
First Claim
Patent Images
1. A method comprising:
- receiving a first analog signal and a second analog signal;
converting the first analog signal to a first digital signal and the second analog signal to a second digital signal;
generating a digital pilot tone;
adding the digital pilot tone to the first digital signal to produce a first summed signal and to the second digital signal to produce a second summed signal;
converting the first summed signal to a first serial signal and the second summed signal to a second serial signal;
interleaving bits of the first serial signal with bits of the second serial signal to generate an interleaved signal; and
producing an optical signal in accordance with the interleaved signal.
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Abstract
A cable television system (100) having forward and reverse paths includes, in the reverse path, a digital optical transmitter (200) for receiving an RF signal, converting it to a digital signal, and adding a digital pilot tone thereto. A laser is driven in accordance with the summed digital signal to generate a digital optical signal representative of the pilot tone and the RF signal. The cable television system (100) also includes an optical receiver (305) for receiving the digital optical signal and recovering therefrom the RF signal and the pilot tone. The optical transmitter (200) and receiver (305) are coupled by fiber optic communication media (110).
22 Citations
16 Claims
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1. A method comprising:
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receiving a first analog signal and a second analog signal; converting the first analog signal to a first digital signal and the second analog signal to a second digital signal; generating a digital pilot tone; adding the digital pilot tone to the first digital signal to produce a first summed signal and to the second digital signal to produce a second summed signal; converting the first summed signal to a first serial signal and the second summed signal to a second serial signal; interleaving bits of the first serial signal with bits of the second serial signal to generate an interleaved signal; and producing an optical signal in accordance with the interleaved signal. - View Dependent Claims (2, 3, 4)
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5. A cable television system for providing signals, the cable television system comprising:
an optical transmitter included in a reverse communication path for receiving an analog signal that has been received from at least one subscriber in the cable television system, the optical transmitter being configured to transmit in accordance therewith a digital optical signal to a headend for processing, the digital optical signal comprising a digital representation of the analog signal and a digital pilot tone, the digital pilot tone being digitally added to the digital representation of the analog signal, the optical transmitter configured to interface with an optical communication medium for coupling the optical transmitter and an optical receiver, the optical receiver being configured to receive the digital optical signal and to recover therefrom an analog signal representative of the analog signal and a pilot tone level from the digital optical signal. - View Dependent Claims (6, 7, 8, 9, 10, 11)
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12. A cable television system for providing signals, the cable television system comprising:
an optical receiver located at a headend of the cable television system configured to receive satellite signals, to demodulate the satellite signals into one of baseband and intermediate frequency signals, and to transmit the one of the baseband and intermediate frequency signals to a plurality of subscribers as an optical signal in a forward communication path, the optical receiver being also configured to receive a digital optical signal from at least one of the plurality of subscribers via a reverse communication path and for recovering therefrom an analog signal, the optical receiver being further configured to interface with an optical communication medium for coupling the optical receiver with an optical transmitter, wherein the optical receiver comprises; a detector for converting the digital optical signal to a digital electrical signal; a digital-to-analog (D/A) converter for converting the digital electrical signal to an analog electrical signal; and a filter for processing the analog electrical signal to recover therefrom a pilot tone and a representative analog signal. - View Dependent Claims (13, 14)
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15. A method comprising:
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receiving an analog signal; converting the analog signal to a digital signal, wherein the digital signal comprises a digital word comprising a number of bits; generating a digital pilot tone, wherein the digital pilot tone comprises a number of bits representative of a level and a frequency; adding the digital pilot tone to the digital signal to produce a summed signal, wherein the adding of the digital pilot tone to the digital signal further comprises performing binary addition of the digital pilot tone and the digital signal; and producing an optical signal in accordance with the summed signal.
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16. A cable television system comprising:
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a headend configured to receive broadcast signals from a satellite, to demodulate the broadcast signals, and to optically transmit the broadcast signals via a fiber optic cable in a forward communication path; an optical node configured to receive the broadcast signals via the fiber optic cable, to convert the broadcast signals to digital electrical signals, and to transmit the digital electric signals to a plurality of subscribers via a coaxial cable in the forward communication path; wherein the optical node comprises an optical transmitter for receiving at least one reverse analog information signal via the coaxial cable from at least one of the plurality of subscribers in the cable television system, the optical transmitter being configured to convert the analog information signal into a reverse digital optical signal and to transmit the reverse digital optical signal to the headend via the fiber optical cable, the reverse digital optical signal comprising a digital representation of the reverse analog information signal and a digitally generated pilot tone that has been digitally added to the digital representation of the reverse analog information signal.
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Specification