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US 7,613,366 B2Granted
Polarization mode dispersion compensator and polarization mode dispersion compensating method
AssigneeFujitsu Limited
InventorsJens C. Rasmussen, Akihiko Isomura, George Ishikawa
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Abstract
An amount of change of a control signal applied to a polarization controller in a polarization mode dispersion compensator is determined for each feedback loop by evaluating degree of polarization response in past feedback loops.
Claims13
A polarization mode dispersion compensator comprising:
- a polarization controller rotating a polarization angle of an input optical signal and outputting polarization controlled light;
- a polarization mode dispersion (PMD) compensating device compensating a polarization mode dispersion of the polarization controlled light and outputting a PMD compensated light;
- a signal quality monitor measuring a degree of polarization (DOP) of the PMD compensated light and generating a feedback signal indicating the measured DOP of the PMD compensated light;
- and
- a control unit controlling the polarization controller and PMD compensating device based on the measured DOP,
- wherein the control unit determines an amount of change of a control signal applied to the polarization controller for a feedback loop, by evaluating a DOP in response to the control signal using a plurality of feedback signals generated in the past feedback loops, changes the control signal by the determined amount, applies a changed control signal to the polarization controller,
- the compensating device is an optical element with a variable and adjustable amount of differential group delay, and
- the control unit determines an amount of change of the differential group delay for each feedback loop by evaluating a past trend of changes of the differential group delay of the compensating device.
5 more elements
A polarization mode dispersion compensating method comprising:
- rotating a polarization angle of an input optical signal and outputting polarization controlled light through a polarization controller;
- compensating a polarization mode dispersion of the polarization controlled light and outputting a polarization mode dispersion (PMD) compensated light through a PMD compensating device;
- measuring a degree of polarization (DOP) of the PMD compensated light and generating a feedback signal indicating the measured DOP of the PMD compensated light;
- and
- controlling the polarization controller and PMD compensating device based on the measured DOP,
- wherein the controlling determines an amount of change of a control signal applied to the polarization controller for a feedback loop, by evaluating a DOP in response to the control signal using a plurality of feedback signals generated in past feedback loops, changes the control signal by the determined amount, and applies a changed control signal to the polarization controller,
- wherein the controlling compares a difference between a maximum and a minimum of the degree of polarization obtained from the respective feedback signals, with a threshold value, and increases the amount of change when the difference is greater than the threshold value.
4 more elements
Dependencies are inferred from the claim text.