Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
2001-05-09
2003-09-09
Kim, Robert H. (Department: 2882)
Optical waveguides
With optical coupler
Particular coupling structure
C385S008000, C385S040000
Reexamination Certificate
active
06618524
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an optical filter of the optical devices used in an optical communication, more particularly, to a tunable Fabry-Perot filter and a method for fabricating the same.
DESCRIPTION OF THE PRIOR ARTS
Technology of making an optical filter, particularly, technology on a tunable optical filter, is related to tunable Fabry-Perot filters, a micro machined device, a Mach-Zehnder interferometer, a fiber bragg grating, acousto-optic tunable filters, electro-optic tunable filters, an arrayed waveguide grating (AWG), an active filter, and ring resonator tunable filters. Description on such tunable filter is well given in pages 50-55 of the IEEE Communication Magazine issued on December, 1998, by D. Sadot and E. Boimovich, and entitled “Tunable Optical Filters for Dense WDM Networks”.
The technologies of the tunable Fabry-Perot filters are largely classified into two kinds. First thing is a method for adjusting optical thickness of a cavity medium between optical fibers each having a high-reflective cross-section by using a piezo-electric technology (see pages 781-783 of Electronics Letters, Vol. 23, issued in 1987 by J. Stone and L. W. Stulz and entitled “Pigtailed high finess tunable fiber Fabry-Perot interferometer with large, medium, and small free spectral range”). The other is a technology of tunably filtering by deriving a variation of refractive index due to a change of polarized light characteristics when an electric field is applied, using Ferroelectric Liquid Crystal as a medium between optical fibers each having a high-reflective cross-section (see pages 379-381 of IEEE Photonics Technology Letters, Vol. 7, No. 4, issued in 1995 by A. Sneh and K. M. Johnson and entitled “High-speed wavelength tunable liquid crystal filter”).
However, the method using piezo-electric technology for adjusting the thickness of the medium makes it difficult to align the optical fibers with each other and has many difficulties in a manufacturing process, since it is configured to use ferrule and a sleeve in aligning the optical fibers.
The technology using Ferroelectric Liquid Crystal as a medium also has many difficulties in aligning and manufacturing processes, because an improvement of the filtering speed is obtained through changing the alignment of the liquid crystal by applying the electric field thereto.
SUMMARY OF THE INVENTION
It is, therefore, a primary object of the invention to provide a tunable Fabry-Perot filter having a broad free spectral range (FSR), good finess, narrow 3-dB peak bandwidth or narrow full width at half-maximum, and a widened tuning range by using a thermo-optic effect of silicon and polymeric material, being easy to manufacture and to align optical fibers, and capable of being used for dense wavelength division multiplexing (WDM).
In order to achieve the object, the present invention provides a tunable Fabry-Perot filter including V-shaped grooves for aligning optical fibers each having a high-reflective cross-section, a thin-film medium having a resonant cavity of a high thermo-optic coefficient, and a thermal electrode formed on or between the thin-film medium.
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Pigtailed High-Finesse Tunable Fibre Fabry-Perot Interferometers with Large, Medium and Small Free Spectral Ranges;1987 Electronics Letters, vol. 23, pp. 781-783.
Sneh, et al.;High-Speed Wavelength Tunable Liquid Crystal Filter;IEEE Photonics Technology Letters, vol. 7, No. 4, Apr. 1995; pp. 379-381.
Bao, et al.;High-Speed Liquid Crystal Fiber Fabry-Perot Tunable Filter;IEEE Photonics Technology Letters, vol. 8, No. 9, Sep. 1996; pp. 1190-1192.
Liu, et al.;Analog Smectic C* Ferroelectric Liquid Crystal Fabry-Perot Optical Tunable Filter;IEEE Photonics Technology Letters, vol. 7, No. 11, Nov. 1995.
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Do Jung Yun
Ju Jung Jin
Lee Myung-Hyun
Min Yoo Hong
Park Seung Koo
Barber Therese
Electronics and Telecommunications Research Institute
Jacobson & Holman PLLC
Kim Robert H.
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