Method and system for equalizing PMD using incremental delay switching
First Claim
1. An apparatus for equalizing polarization mode dispersion in an optical data signal traveling through an optical fiber, comprising:
- (a) a polarization mode separator which separates the optical data signal into a first polarized signal and a second differently polarized signal traveling along respective first and second paths;
(b) a first variable time delay element located along said first path for selectively providing a first incremental propagation delay to said first polarized signal;
(c) a second variable time delay element located along said second path for selectively providing a second incremental propagation delay to said second polarized signal;
(d) a time variant controller coupled to said first and second variable time delay elements, said controller controlling the selection of said first and second time delay elements such that said first and second polarized signals have a relative propagation delay that compensates for polarization mode dispersion, said relative propagation delay corresponding to the difference between said first and second incremental propagation delays; and
(e) a beam combiner, coupled to said first and second optical paths after said first and second time delay elements, the beam combiner combining said first and second signals to form an optical output data signal compensated for polarization mode dispersion.
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Abstract
A polarization beam splitter separates the optical data signal into first and second orthogonally polarized optical signals. A first variable time delay element provides a first incremental propagation delay for the first polarized optical signal. A second variable time delay element provides a second incremental propagation delay for the second polarized optical signal. The first and second variable time delay elements consist of a series of optical switches optically interconnected by different incremental lengths of optical fiber. For example, 2×2 optical switches are provided for switching between a reference fiber segment and a respective delay fiber segment to provide a relative incremental propagation delay. A controller controls optical switches in the first and second variable switching delay elements to set first and second incremental propagation delays. In particular, the first and second polarized optical signals are incrementally delayed relative to one another so as to compensate for polarization mode dispersion. A beam combiner then combines the first and second signals to form an optical output data signal which can be detected accurately by a receiver without the effects of polarization mode dispersion. In this way, optical data signals can be reliably transmitted over greater distances along a long-haul fiber optic dispersive medium at even greater bit-rates and bandwidth.
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Citations
21 Claims
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1. An apparatus for equalizing polarization mode dispersion in an optical data signal traveling through an optical fiber, comprising:
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(a) a polarization mode separator which separates the optical data signal into a first polarized signal and a second differently polarized signal traveling along respective first and second paths; (b) a first variable time delay element located along said first path for selectively providing a first incremental propagation delay to said first polarized signal; (c) a second variable time delay element located along said second path for selectively providing a second incremental propagation delay to said second polarized signal; (d) a time variant controller coupled to said first and second variable time delay elements, said controller controlling the selection of said first and second time delay elements such that said first and second polarized signals have a relative propagation delay that compensates for polarization mode dispersion, said relative propagation delay corresponding to the difference between said first and second incremental propagation delays; and (e) a beam combiner, coupled to said first and second optical paths after said first and second time delay elements, the beam combiner combining said first and second signals to form an optical output data signal compensated for polarization mode dispersion. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for equalizing polarization mode dispersion in an optical data signal traveling through an optical fiber, comprising the steps of:
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(a) separating the optical data signal into a first polarized signal and a second differently polarized signal traveling along respective first and second paths; (b) delaying the first polarized signal utilizing a first variable time delay element located along said first path; (c) delaying the second signal utilizing a second variable time delay element located along said second path; (d) controlling the first and second time delay elements utilizing a time variant controller coupled to said first and second variable time delay elements, said controller controlling said first and second time delay elements such that said first and second signal have a relative propagation delay that compensates for polarization mode dispersion, said relative propagation delay corresponding to the difference between said first and second incremental propagation delays; and (e) combining said first and second signals to form an optical output data signal compensated for polarization mode dispersion utilizing a beam combiner coupled to said first and second optical paths after said first and second time delay elements. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. An system for equalizing polarization mode dispersion in an optical data signal traveling through an optical fiber, the system comprising:
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(a) a means for separating the optical data signal into a first polarized signal and a second differently polarized signal traveling along respective first and second paths; (b) a means for delaying the first polarized signal utilizing a first variable time delay element located along said first path; (c) a means for delaying the second signal utilizing a second variable time delay element located along said second path; (d) a means for controlling the first and second time delay elements utilizing a time variant controller coupled to said first and second variable time delay elements, said controller controlling said first and second time delay elements such that said first and second signal have a relative propagation delay that compensates for polarization mode dispersion, said relative propagation delay correspond to the difference between said first and second incremental propagation delays; and (e) a means for combining said first and second signals to form an optical output data signal compensated for polarization mode dispersion, wherein said means for combining is coupled to said first and second optical paths after said first and second time delay elements.
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Specification