Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
1998-12-31
2001-06-12
Derrington, James (Department: 1731)
Optical waveguides
With optical coupler
Input/output coupler
C385S010000, C385S039000, C065S385000, C065S392000, C359S290000
Reexamination Certificate
active
06246814
ABSTRACT:
CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C §119 from an application entitled Tunable Chirped Fiber Grating Device And Method For Forming Chirped Fiber Grating earlier filed in the Korean Industrial Property Office on Dec. 31, 1997, and there duly assigned Serial No. 97-82102 by that Office.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tunable chirped fiber grating device in which the spacings of perturbations in the index of refraction vary with a strain which is produced by applying a voltage across a predetermined piezoelectric element and a method for forming a chirped fiber grating.
2. Description of the Related Art
Typically, a chirped grating is designed to have different perturbation spacings or different effective refractive indices depending on positions of the perturbations, and is characterized in that the wavelength of reflected light differs depending on the positions of the perturbations.
FIGS. 1A and 1B
show side views illustrating an optical fiber in which a chirped grating is formed. Here, a core is represented by reference numeral
100
or
120
, a cladding by
110
or
130
, and a grating by
101
or
102
. The chirped grating
101
in the core
100
according to
FIG. 1A
has a structure in which the spacings of successive perturbations are different from each other, while the effective refractive indices of the perturbations are the same, and a chirped grating
102
in the core
120
according to
FIG. 1B
has a structure in which the spacings of successive perturbations are the same, while the effective refractive indices of the perturbations are different from each other.
However, chirped gratings in which the spacings of successive perturbations are different are doomed to experience more complicated procedures than those having equal perturbation spacings. Since the chirping rates of the reflected wavelengths according to the positions of the perturbations are fixed to values in fabrication conditions and the gratings are used for a specific wavelength band, the gratings cannot be flexibly applied (manufactured).
Forming chirped gratings is known in the art as exemplified by U.S. Pat. No. 5,781,670 to is David A. G. Deacon, et al. entitled Optical Frequency Channel Selection Filter With Electronically-controlled Grating Structures; U.S. Pat. No. 5,718,738 to Glenn Eric Kohnke et al. entitled Method For Making Continuously Chirped Fiber Bragg Gratings; U.S. Patent No. 5,636,304 to Victor Mizrahi et al. entitled Article Comprising A Spa tially Varying Bragg Grating In An Optical Fiber; and U.S. Pat. No. 5,007,705 to William W. Morey et al. entitled Variable Optical Fiber Bragg Filter Arrangement.
SUMMARY OF THE INVENTION
To solve the above problem, it is an objective of the present invention to provide, in an optical fiber, a tunable chirped grating device whose perturbation spacings are equal but will differ from each other by applying a controlled voltage to an element attached to the optical fiber since the length of the attached element can vary with the applied voltage, and a method for forming a chirped fiber grating.
Accordingly, to achieve the above objective, there is provided a tunable chirped grating device, included in an optical fiber, having the same spacings between index perturbations, a piezoelectric element, bonded to the optical fiber, for changing the perturbation spacings according to an applied voltage, and a voltage source for applying the voltage to the piezoelectric element.
To achieve the above objective, there is provided a method for forming a chirped fiber grating including the steps of (a) forming a grating having regularly spaced perturbations in the optical fiber, and (b) causing the perturbation spacings of the optical fiber grating to differ from each other by applying different tensions to the optical fiber grating according to the positions of the perturbations.
REFERENCES:
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patent: 5007705 (1991-04-01), Morey et al.
patent: 5636304 (1997-06-01), Mizrahi et al.
patent: 5671307 (1997-09-01), Lauzon et al.
patent: 5694501 (1997-12-01), Alavie et al.
patent: 5699468 (1997-12-01), Farries et al.
patent: 5718738 (1998-02-01), Kohnke et al.
patent: 5781670 (1998-07-01), Deacon et al.
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Ohn M M, et al.: “Dispersion Variable Fibre Bragg Grating Using a Piezoelectric Stack” Electronics Letters, Oct. 10, 1996, IEE, UK, vol. 32, No. 21, pp. 2000-20001, XP 000683539 ISSN 0013-5194.
Cruz J. L , et al.: “Fibre Bragg Gratings Tuned Nad Chirped Using Magnetic Fields” Electronics Letters, Jan. 30, 1997, IEE, UK, vol. 33, No. 3, pp. 235-236, XP00725938 ISSN 0013-5194.
Pacheco M, et al. “Chirping Optical Fibre Bragg Gratings Using Taperd-thicknes Piezoelectric Ceramic” Electronics Letters, Nov. 26, 1998, IEE, UK, vol. 34, No. 24, pp. 2348-2350, XP 002099851 ISSN 0013-5194.
Bushnell , Esq. Robert E.
Derrington James
Samsung Electronics Co,. Ltd.
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