초록 ▼

An optical heterodyne detection system in accordance with an embodiment of the invention includes two optical receivers for separately measuring the power of an input signal and a local oscillator signal before the signals are combined. The measurements of the input signal and the local oscillator s

An optical heterodyne detection system in accordance with an embodiment of the invention includes two optical receivers for separately measuring the power of an input signal and a local oscillator signal before the signals are combined. The measurements of the input signal and the local oscillator signal are then utilized to enhance the heterodyne signal to noise ratio by removing the intensity noise contributed by the input signal and the local oscillator signal. By measuring portions of the input signal power and the local oscillator signal power and then subtracting out the scaled quantities from the photocurrent measurement during signal processing, the signal to noise of the heterodyne signal is improved beyond that which is accomplished by known balanced receivers.

대표청구항 ▼

An optical heterodyne detection system in accordance with an embodiment of the invention includes two optical receivers for separately measuring the power of an input signal and a local oscillator signal before the signals are combined. The measurements of the input signal and the local oscillator s

An optical heterodyne detection system in accordance with an embodiment of the invention includes two optical receivers for separately measuring the power of an input signal and a local oscillator signal before the signals are combined. The measurements of the input signal and the local oscillator signal are then utilized to enhance the heterodyne signal to noise ratio by removing the intensity noise contributed by the input signal and the local oscillator signal. By measuring portions of the input signal power and the local oscillator signal power and then subtracting out the scaled quantities from the photocurrent measurement during signal processing, the signal to noise of the heterodyne signal is improved beyond that which is accomplished by known balanced receivers. prises a photon counting detector. 11. The quantum optical measurement system of claim 1 further comprising a polarization-specific variable delay module in optical communication with said separation element. 12. The quantum optical measurement system of claim 11 wherein the said polarization-specific variable delay module comprises one or more polarization-specific delay elements, said elements jointly or individually in optical communication with said separation element. 13. The quantum optical measurement system of claim 11 wherein the said polarization-specific variable delay module imparts a time delay to the one of said twin photons, said twin photon polarized in a first polarization axis, said delay relative to the time delay imparted to the one of said twin photons polarized in a second polarization axis, said first and second polarization axes being orthogonal. 14. The quantum optical measurement system of claim 13 wherein the time delay imparted by said polarization-specific variable delay module is relatively positive or relatively negative. 15. The quantum optical measurement system of claim 1 wherein, for each of said twinons, said first twin photon has a first energy and said second twin photon has a second energy, the sum of said first energy and said second energy being substantially equal to a constant value. 16. The quantum optical measurement system of claim 15 wherein, for each of said twinons, said first energy of said first twin photon is distributed within a predetermined range of energy. 17. The quantum optical measurement system of claim 16 wherein said predetermined range of energy corresponds to photon wavelengths substantially between 1300 nanometers and 1700 nanometers. 18. A quantum optical measurement system for determining polarization mode dispersion comprising: an entangled photon source, said entangled photon source generating a plurality of photon pairs (twinons), each of said twinons comprising a first twin photon and a second twin photon, said first twin photon being correlated to said second twin photon in at least one of time, wavelength and polarization; an optical element to be measured in optical communication with said entangled photon source, said optical element receiving said plurality of twinons; a separation element in optical communication with said optical element to be measured, said separation element providing a first optical path and a second optical path for said twinons; an optical demultiplexer in optical communication with said separation element along said first optical path, said demultiplexer adapted to provide a plurality of spectral beams, one of said spectral beams comprising one of said first twin photon and said second twin photon, from each of said twinons, at a predetermined wavelength; a plurality of first detectors, each of said first detectors adapted to receive a respective one of said spectral beams; and a second detector in optical communication with said separation element along said second optical path. 19. The quantum optical measurement system of claim 18 wherein said optical element is a communications optical channel. 20. A method for determining polarization mode dispersion of an optical element comprising: forming a plurality of first twin photons and second twin photons (twinons); transmitting said plurality of twinons through said optical element; providing a first optical path and a second optical path for said plurality of twinons, said paths being indistinguishable in the quantum-optical sense; determining a wavelength for each of said plurality of twinons, said wavelength being the wavelength of one of said first twin photon and said second twin photon; detecting one or both of said twin photons from each twinon in said plurality of twinons after transmission through said optical element at a first detector; detecting one or both of said twin photons from each twinon in said plurality of twinons after transmission through said optical element at a second detector; and determining said polarization mode dispersion of said optical element in response to said steps of detecting. 21. The method for determining polarization mode dispersion of an optical element of claim 20 further comprising the step of isolating said first detector and said second detector with polarizing elements, said polarizing elements oriented at 45 degrees to the polarization axes of said first twin photons. 22. The method for determining polarization mode dispersion of an optical element of claim 20 further comprising the step of delaying each of said plurality of twinons before detecting said twinon at said first detector, said delay being polarization-specific. 23. A quantum optical measurement system for determining an optical characteristic of an active optical channel comprising: an entangled photon source, said entangled photon source generating a plurality of photon pairs (twinons), each of said twinons comprising a first twin photon and a second twin photon, said first twin photon being correlated to said second twin photon in at least one of time, wavelength and polarization; an injector module having a first injector input port in optical communication with said entangled photon source, a second injector input port adapted to receive an optical data stream and an injector output port in optical communication with said optical channel, said injector module providing a combined optical stream at said injector output port; an extractor module having an extractor input port in optical communication with said optical channel, a first extractor output port adapted to transmit said optical data stream and a second extractor output port in optical communication with a quantum interference device, said extractor module accepting a combined optical stream at said extractor input port; a separation element, forming the input to said quantum interference device, in optical communication with said second extractor output port, said separation element providing a first optical path and a second optical path for said twinons; an optical demultiplexer in optical communication with said separation element along said first optical path, said demultiplexer adapted to provide a plurality of spectral beams, one of said spectral beams comprising one of said first twin photon and said second twin photon, from each of said twinons, at a predetermined wavelength; a plurality of first detectors, each of said first detectors adapted to receive a respective one of said spectral beams; and a second detector in optical communication with said separation element along said second optical path. 24. The quantum optical measurement system of claim 23 further comprising a electronic processing unit in communication with said plurality of first detectors and said second detector. 25. The quantum optical measurement system of claim 24 wherein said processing unit is adapted to identify coincident photon detections in said second detector, said coincident detections being photon detections in said second detector that occur within a pre-determined time window before or after a photon detection in one of said plurality of first detectors. 26. The quantum optical measurement system of claim 25 wherein said processor said processor adapted to generate a rate coincidence detections. 27. The quantum optical measurement system of claim 23 further comprising: a first polarization analyzer in optical communication with said separation element and said demultiplexer; and a second polarization analyzer in optical communication with said separation element and said second detector. 28. The quantum optical measurement system of claim 23 further comprising a polarization-specific variable delay module in optical communication with said separation element and located in one of said first optical path and said second optical path. 29. The quantum optical measurement system of claim 23 wherein sai