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US 5,295,013 AGranted
Optical receiver of direct detection type
AssigneeNEC Corporation
InventorTakashi Ono
Life of this patent
Estimating the term…
Abstract
An optical receiver according to the present invention is used for detecting FSK or PSK signal light directly. The receiver has a PM fiber and a peak detector. The peak detector detects an amplitude of a demodulated output signal. In accordance with an output signal of the peak detector, a polarization condition of a signal light to be supplied to the PM fiber is controlled so as to keep the output of the peak detector maximum.
Claims9
An optical receiver of direct detection type, comprising:
- a polarization controller for controlling polarizations of an input signal light modulated by an optical FSK (frequency shift keying) method;
- a PM (polarization-maintaining) fiber for discriminating a frequency of an output light of said polarization controller;
- a polarization divider for dividing an output light of said PM fiber into two orthogonal lights in polarization, said polarization divider being structured to have an optical axis having forty five degrees to the two intrinsic optical axes of said output light of said PM fiber;
- means for demodulating at least one of two output lights of said polarization divider to provide said signal light;
- means for detecting amplitude of said demodulated signal light;
- and
- a controller for controlling said polarization controller in accordance with an output of said amplitude detecting means so that said output of said amplitude detecting means is controlled to have maximum value.
4 more elements
An optical receiver of direct detection type, comprising:
- a polarization controller for controlling polarizations of an input signal light modulated by an optical PSK (phase shift keying) method;
- a PM (polarization-maintaining) fiber for discriminating a frequency of an output light of said polarization controller;
- a polarization divider for dividing an output light of said PM fiber into two orthogonal lights in polarization, said polarization divider being structured to have an optical axis having forty five degrees to the two intrinsic optical axes of said output light of said PM fiber;
- means for demodulating at least one of two output lights of said polarization divider to provide said signal light;
- means for detecting an amplitude of said demodulated signal light;
- and
- a controller for controlling said polarization controller in accordance with an output of said amplitude detecting means so that said output of said amplitude detecting means is controlled to have maximum value.
4 more elements
An optical receiver of direct detection type, comprising:
- a polarization controller for controlling polarizations of an input signal light modulated by an optical PSK (phase shift keying) method;
- means for coupling an output light of said polarization controller with an excitation light;
- a PM (polarization-maintaining) fiber for discriminating a phase of an output light of said coupling means, said PM fiber being of rare-earth element doped type for amplifying an input light in accordance with said excitation light;
- a polarization divider for dividing an output light of said PM fiber into two orthogonal lights in polarization, said polarization divider being structured to have an optical axis having forty five degrees to the two intrinsic optical axes of said output signal of said PM fiber;
- means for demodulating said signal light at least one of two output lights of said polarization divider to provide said signal light;
- means for detecting an amplitude of said demodulated signal light;
- and
- a controller for controlling said polarization controller in accordance with an output of said amplitude detecting means so that said output of said amplitude detecting means is controlled to have maximum value.
5 more elements
An optical receiver of direct detection type, comprising:
- a polarization controller for controlling polarizations of an input signal light modulated by an optical FSK (frequency shift keying) method;
- means for coupling an output light of said polarization controller with an excitation light;
- a PM (polarization-maintaining) fiber for discriminating a phase of an output light of said coupling means, said PM fiber being of rare-earth element doped type for amplifying an input light in accordance with said excitation light;
- a polarization divider for dividing an output light of said PM fiber into two orthogonal lights in polarization, said polarization divider being structured to have an optical axis having forty five degrees to the two intrinsic optical axes of said output signal of said PM fiber;
- means for demodulating said signal light at least one of two output lights of said polarization divider to provide said signal light;
- means for detecting an amplitude of said demodulated signal light;
- and
- a controller for controlling said polarization controller in accordance with an output of said amplitude detecting means so that said output of said amplitude detecting means is controlled to have maximum value.
5 more elements
Dependencies are inferred from the claim text.