Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1999-03-12
2004-07-06
Negash, Kinfe-Michael (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C385S024000
Reexamination Certificate
active
06760137
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to wave division multiplexing communications systems, devices and methods generally.
BACKGROUND OF THE INVENTION
Wave division multiplexing communication systems employing optical fiber links are known in the art but suffer in some cases from a limitation in range and/or in transmission rate and thus require amplification along the optical fiber links for distances generally exceeding 80 km.
The following patents and publications are believed to represent the state of the art and are hereby incorporated by reference: U.S. Pat. Nos. 5,600,473; 5,455,672; 5,463,487; 5,355,237.
SUMMARY OF THE INVENTION
The present invention seeks to overcome the above-described limitations of prior art wave division multiplexing communications systems.
There is thus provided in accordance with a preferred embodiment of the present invention a wave division multiplexing communications system a wave division multiplexing communications system including a plurality of optical transmitters, each of the optical transmitters including a distributed feed back laser characterized in that it has a dispersion penalty of less than 2 dB when used for transmission into an optical fiber having chromatic dispersion of 1800 ps
rn, driver operative for receiving a communications signal input and providing electrical power to the distributed feed back laser in accordance therewith, and a wave division multiplexer receiving outputs from the plurality of optical transmitters including thin film dielectric layers and having a maximum power insertion loss of 4.5 dB.
There is also provided in accordance with another preferred embodiment of the present invention a wave division demultiplexing communications system including a wave division demultiplexer receiving wave division multiplexed inputs and including thin film dielectric layers and having a maximum power insertion loss of 4.5 dB, the wave division demultiplexer being characterized in that losses exceeding 25 dB for adjacent channels and exceeding 35 dB for non-adjacent channels are experienced, and a plurality of optical receivers receiving demultiplexed inputs, each of the optical receivers including an avalanche photodiode trans-impedance amplifier having a sensitivity of at least −25 dBm, a limiting amplifier which receives an output from the avalanche photodiode trans-impedance amplifier, and a clock and data recovery circuit receiving an output signal from the limiting amplifier.
Further in accordance with a preferred embodiment of the present invention the transmission power of each of the optical transmitters exceeds +2 dBm.
Further in accordance with a preferred embodiment of the present invention the avalanche photodiode trans-impedance amplifier has a sensitivity of at least −29 dBm.
There is thus provided in accordance with another preferred embodiment of the present invention a wave division multiplexing communications system including a plurality of optical transmitters, each of the optical transmitters including a distributed feed back laser characterized in that it has a dispersion penalty of less than 2 dB when used for transmission into an optical fiber having chromatic dispersion of 1800 ps
m, a driver operative for receiving a communications signal input and providing electrical power to the distributed feed back laser in accordance therewith, and a wave division multiplexer receiving outputs from the plurality of optical transmitters and including thin film dielectric layers and having a maximum power insertion loss of 4.5 dB, a plurality of optical receivers, each of the optical receivers including an avalanche photodiode trans-impedance amplifier having a sensitivity of at least −25 dBm, a limiting amplifier which receives an output from the avalanche photodiode trans-impedance amplifier, and a clock and data recovery circuit receiving an output signal from the limiting amplifier and a wave division demultiplexer receiving an input from the wave division multiplexer and providing outputs to the optical receivers and including thin film dielectric layers and having a maximum power insertion loss of 4.5 dB, the wave division demultiplexer being characterized in that losses exceeding 25 dB for adjacent channels and exceeding 35 dB for non-adjacent channels are experienced, wherein the maximum combined power insertion losses of the wave division multiplexer and the wave division demultiplexer do not exceed 7.0 dB, thereby obviating the need for power amplification equipment between the wave division multiplexer and the wave division demultiplexer.
These is also provided in accordance with yet another preferred embodiment of the present invention a wave division multiplexing communications system including a plurality of optical transmitters, a wave division multiplexer receiving outputs from the plurality of optical transmitters and having a maximum power insertion loss of 4.5 dB, an optical fiber link having a distance exceeding 80 km, a plurality of optical receivers, and a wave division demultiplexer receiving an input from the wave division multiplexer over the optical fiber link and providing outputs to the optical receivers and having a maximum power insertion loss of 4.5 dB, wherein the maximum combined power insertion losses of the wave division multiplexer and the wave division demultiplexer do not exceed 7.0 dB, thereby obviating the need for power amplification equipment between the wave division multiplexer and the wave division demultiplexer.
There is also provided in accordance with another preferred embodiment of the present invention a wave division multiplexing communications system including a plurality of optical transmitters, a wave division multiplexer receiving outputs from the plurality of optical transmitters and having a maximum power insertion loss of 4.5 dB, an optical fiber link, a plurality of optical receivers, and a wave division demultiplexer receiving an input from the wave division multiplexer over the optical fiber link and providing outputs to the optical receivers and having a maximum power insertion loss of 4.5 dB, wherein the optical fiber link line loss is less than about 22 dB and the maximum combined power insertion losses of the wave division multiplexer and the wave division demultiplexer do not exceed 7.0 dB, thereby obviating the need for power amplification equipment between the wave division multiplexer and the wave division demultiplexer.
Further in accordance with a preferred embodiment of the present invention each of the plurality of optical transmitters includes a distributed feed back laser characterized in that it has a dispersion penalty of less than 2 dB when used for transmission into an optical fiber having chromatic dispersion of 1800 ps
m, a driver operative for receiving a communications signal input and providing electrical power to the distributed feed back laser in accordance therewith.
Still further in accordance with a preferred embodiment of the present invention the transmission power of each of the optical transmitters exceeds +2 dBm.
Additionally in accordance with a preferred embodiment of the present invention the wave division multiplexing communications system includes eight optical transmitters.
Moreover in accordance with a preferred embodiment of the present invention each of the plurality of optical receivers includes a plurality of optical receivers receiving demultiplexed inputs, each of the optical receivers further including an avalanche photodiode trans-impedance amplifier having a sensitivity of at least −25 dBm, a limiting amplifier which receives an output from the avalanche photodiode trans-impedance amplifier, and a clock and data recovery circuit receiving an output signal from the limiting amplifier.
Preferably the division demultiplexer includes thin film dielectric layers and has a maximum power insertion loss of 4.5 dB, the wave division demultiplexer being characterized in that losses exceeding 25 dB for adjacent channels and exceeding 35 dB for non-adjacent ch
ECI Telecom Ltd.
Nath & Associates
Negash Kinfe-Michael
Novick Harold L.
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