Optical Homodyne Receiver
AssigneeAT&T Bell Laboratories
InventorsJoseph M. Kahn, Bryon L. Kasper
Life of this patent
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Abstract
An optical homodyne receiver is realized by employing two separate signal amplification paths in a balanced receiver configuration. Specifically, the relative phase difference between a received optical signal and a local oscillator signal is extracted from nodes which, from the point of view of an amplifier extracting a data component signal, are at ac ground. This approach permits a phase detector amplifier, which extracts the relative phase component, to be dc coupled in addition to having a higher transimpedance for lower thermal noise, and thus higher sensitivity. Additionally, by extracting the data and phase component signals at different points in a balanced receiver configuration, the data and phase amplifiers can be separately engineered for optimum performance.
Claims16
An optical homodyne receiver comprising:
- first and second photodetectors responsive to first and second optical signals, respectively, said first photodetector connected between first and second terminals, said second photodetector connected between a third terminal and said second terminal, said first optical signal comprising the electrical-field sum of a local oscillator signal and a received optical signal, and said second optical signal comprising the electrical-field difference between said local oscillator signal and said received optical signal;
- means, for detecting a data component of said received optical signal, electrically connected to said second terminal;
- and
- means, for detecting the relative phase difference between said received optical signal and said local oscillator signal, electrically connected across said first and third terminals.
An optical communication system comprising an optical transmitter, an optical homodyne receiver and a transmission medium optically coupled jointly to said optical transmitter and said optical homodyne receiver for supporting a received optical signal therebetween, said optical homodyne receiver comprising:
- an optical means for linearly combining said received optical signal and a local oscillator signal to produce first and second optical signals, said first optical signal comprising the electrical-field sum of a local oscillator signal and said received optical signal, said second optical signal comprising the electrical-field difference between said local oscillator signal and said received optical signal;
- first and second photodetectors responsive to first and second optical signals, respectively, said first photodetector electrically connected between first and second terminals, said second photodetector connected between a third terminal and said second terminal;
- means, for detecting a data component of said received optical signal, electrically connected to said second terminal;
- means, for detecting the relative phase difference between said received optical signal and said local oscillator signal, electrically connected across said first and third terminal.
Dependencies are inferred from the claim text.