Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
2000-08-31
2001-08-28
Pascal, Leslie (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200, C359S199200, C359S199200, C359S199200, C359S199200
Reexamination Certificate
active
06281996
ABSTRACT:
TECHNICAL FIELD
This invention relates to an optical termination unit of a hybrid fiber/coax access network with a forward channel and a return channel. It is also directed and to a method of transmitting electric signals from two or more terminals of a hybrid fiber/coax access network over an electric line and an optical line.
BACKGROUND OF THE INVENTION
A hybrid fiber/coax access network is, for example, a cable television distribution network with a forward channel and a return channel, over which different bidirectional services, such as telephony, Internet communication, or video telephony, can be provided. DE 44 36 818 C1 discloses a subscriber access network for transmitting digital signals of bidirectional interactive telecommunications services. Behind the coaxial cable repeater of a CATV coaxial cable tree network which is closest to a respective subscriber, the optical fibers of a fiber-optic network are bidirectionally connected to the branches of the tree network. Transmission on the optical fibers is digital, for example in the ATM format. This requires a demodulation and/or a frequency conversion of the electric subscriber signals.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to transmit electric signals of a plurality of terminals of a hybrid fiber/coax access network over significant distances, e.g., 50 km, with a smaller amount of technical complexity.
This object is attained by an optical network termination unit of a hybrid fiber/coax access network with a forward channel and a return channel which serves to receive and electrically transmit optical signals in the forward channel and to receive quasi-analog electric signals and optically retransmit said quasi-alalog electric signals in digital form in the return channel, which for this purpose comprises an optical-to-electrical transducer, a digital electrical-to-optical transducer, and an analog-to-digital converter, wherein the received electric signals are digitized in the analog-to-digital converter, and wherein the digitized signals are converted to digital optical signals in the digital electrical-to-optical transducer.
The object is also attained by a method of transmitting electric signals from two or more terminals of a hybrid fiber/coax access network over an electric line and an optical line, comprising the steps of transmitting the electric signals of the two or more terminals together over the electric line to an optical network termination unit; and digitizing the signals received in the optical termination unit and then converting the digitized signals to optical signals by means of a digital electrical-to-optical transducer.
A particular advantage of the invention is that a smaller amount of circuitry is required in the optical network termination units to convert the electric signals to optical signals.
Another advantage of the invention is the flexibility of the application of the optical network termination units as a result of the conversion of the electric signals without previous demodulation and the resulting applicability to arbitrarily modulated signals.
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Gottlicher, Gerhard, Selb, Michael, Bender, Rolf. Digitale Übertragung von Analogsignalen über LWL-Strecken. In: Electronik 1, 8.1, 1988, pp 64-68.
Alcatel
Pascal Leslie
Phan Hanh
Ware Fressola Van der Sluys & Adolphson LLP
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