Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
1998-09-24
2001-10-09
Font, Frank G. (Department: 2877)
Optical waveguides
With optical coupler
Input/output coupler
C385S043000
Reexamination Certificate
active
06301408
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to optical fiber grating devices and systems using them. In particular, it concerns tapered optical fiber grating devices with variable index coatings that change the spectral shaping properties of the grating by modifying the effective index of the fundamental mode.
BACKGROUND OF THE INVENTION
Optical fiber gratings are used for spectral shaping in modem telecommunications systems and sensing systems. A typical optical fiber grating includes a periodic or quasiperiodic pattern of refractive index fluctuations or perturbations along an optical fiber. Bragg-based fiber gratings reflect light within a narrow wavelength band and transmit wavelengths of light outside of that band to provide spectral shaping. Long period fiber grating designs couple selected wavelengths of light from the fundamental mode into rapidly attenuated cladding modes to provide spectral shaping. These spectral shaping properties permit fiber gratings to be used as gain equalizers, narrowband filters, dispersion compensators, and shift detectors.
Spectral shaping can also be accomplished with tapered optical fibers. For example, U.S. Pat. No. 5,473,714 issued to Vengsarkar on Dec. 5, 1995, titled “Optical Fiber System Using Tapered Fiber Devices”, discloses a tapered fiber device which can be used for optical filtering. The taper of the fiber is dimensioned to permit signals of a first wavelength to pass with little loss while signals of a second wavelength are blocked.
Telecommunications and sensing systems operate under many conditions which cause them to experience spectral changes. Unfortunately, conventional fiber gratings and tapered fibers have static spectral shaping properties which can not be tuned or adjusted to compensate for these changes. Therefore, there is a need for an optical fiber device that can be adjusted or tuned to provide different spectral shaping properties.
SUMMARY
An improved optical fiber grating device comprises a length of optical fiber having a predetermined fundamental mode effective guide index and a longitudinally tapered region for accessing a fundamental mode of light. The tapered region includes a grating having a predetermined light spectral shaping property that shapes the light spectrum of the fundamental mode. A coating surrounds the tapered region of the fiber for modifying the fundamental mode effective guide index of the fiber in order to change the spectral shaping property of the grating.
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A.M. Vengsarkar et al., “Long-Period Fiber Gratings as Band Rejection Filters,” Journal of Lightwave Technology, vol. 14, No. 1, Jan., 1996, pp. 58-65.
Espindola Rolando Patricio
Stentz Andrew John
Wagener Jefferson Lynn
Font Frank G.
Lowenstein & Sandler PC
Lucent Technologies Inc
Mooney Michael P.
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