Article comprising a dispersion compensating grating with low polarization mode dispersion
First Claim
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1. An article comprising a dispersion compensator for compensating a chromatic dispersion in an optical fiber communication system wherein the dispersion compensator comprisesa) a directional transfer device having a first, second and third port, said first port being an input port, and said third port being an output port;
- b) a polarization maintaining optical fiber having a predetermined first and second axis of polarization, with an intrinsic fiber birefringence of 10-6 or more, the polarization maintaining optical fiber being signal-transmissively connected to the second port of the directional transfer device; and
c) a chirped Bragg grating disposed in said polarization maintaining optical fiber;
CHARACTERIZED IN THATd) the chirped Bragg grating is spaced from said second port of the directional transfer device, the length L of polarization maintaining optical fiber between said second port and said chirped Bragg grating being selected such that, for radiation of wavelength λ
, the chromatic dispersion at the third port is substantially less than the corresponding chromatic dispersion at the first port, with L being furthermore selected such that 2(z±
L)Vg is at least approximately equal to Dλ
, where z is a penetration depth of the signal radiation λ
into the chirped Bragg grating, and Vg is a group velocity of the signal radiation in the polarization maintaining fiber, where L is added to z if a grating dispersion is negative, and L is subtracted from z if the grating dispersion is positive, and where D is a dispersion in the chirped Bragg grating.
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Abstract
A dispersion compensating chirped optical fiber Bragg grating according to our invention is formed in polarization maintaining (PM) fiber having birefringence of at least 10-6, preferably 10-5 or more. Use of the PM fiber makes possible substantial cancellation of the polarization mode dispersion that typically is unavoidably present in chirped Bragg gratings for dispersion compensation.
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Citations
13 Claims
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1. An article comprising a dispersion compensator for compensating a chromatic dispersion in an optical fiber communication system wherein the dispersion compensator comprises
a) a directional transfer device having a first, second and third port, said first port being an input port, and said third port being an output port; -
b) a polarization maintaining optical fiber having a predetermined first and second axis of polarization, with an intrinsic fiber birefringence of 10-6 or more, the polarization maintaining optical fiber being signal-transmissively connected to the second port of the directional transfer device; and c) a chirped Bragg grating disposed in said polarization maintaining optical fiber;
CHARACTERIZED IN THATd) the chirped Bragg grating is spaced from said second port of the directional transfer device, the length L of polarization maintaining optical fiber between said second port and said chirped Bragg grating being selected such that, for radiation of wavelength λ
, the chromatic dispersion at the third port is substantially less than the corresponding chromatic dispersion at the first port, with L being furthermore selected such that 2(z±
L)Vg is at least approximately equal to Dλ
, where z is a penetration depth of the signal radiation λ
into the chirped Bragg grating, and Vg is a group velocity of the signal radiation in the polarization maintaining fiber, where L is added to z if a grating dispersion is negative, and L is subtracted from z if the grating dispersion is positive, and where D is a dispersion in the chirped Bragg grating. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification