Optical waveguides – Accessories – Attenuator
Reexamination Certificate
2000-03-03
2001-03-27
Ullah, Akm E. (Department: 2874)
Optical waveguides
Accessories
Attenuator
Reexamination Certificate
active
06208798
ABSTRACT:
FIELD OF THE INVENTION
This invention is generally related to optical attenuators and more particularly to variable fiber optic attenuators that use a thermo-optical control mechanism.
BACKGROUND
Variable fiber optic attenuators play an important role in the implementation of modern information networks having optical interconnects. For instance, in wave division multiplexed (WDM) optical networks having increased wavelength content and greater functionalities, optical channels of communication may be added, dropped, and/or rerouted at any node of the network. This flexibility makes the network more complex from an optical content point of view, such that it becomes important to carefully monitor the optical power in individual wavelength channels. Without such control, unacceptably high error rates may occur during propagation through communication channels having optical amplifiers, so called add-drop modules, multiplexers/de-multiplexers as well as other optical signal conditioning components. Accordingly, low cost, reliable devices to adjust the power level of the optical signals with high accuracy and high repeatability are needed.
Conventional variable optical attenuators have featured several types of architectures, including the use of a lossy fusion splice (see U.S. Pat. No. 4,557,557) and those that vary the distance from one optical fiber end-face to the end-face of an opposed optical fiber (see U.S. Pat. No. 5,050,956). More recently, an attenuator has been developed by Molecular Optoelectronics Corp. (MOEC) that allows electronic control of the attenuation by controlling the temperature of a control layer with an index of refraction that varies with temperature. The control layer is placed against the polished side (cladding) of a fiber to alter the boundary conditions of the optical signals traveling through the core of the fiber , resulting in the attenuation of the optical signal. The fiber side polishing technique, however, results in a rather expensive product due to the manufacturing process which is time and labor intensive.
SUMMARY
An apparatus that features an optical fiber with a core surrounded by a cladding, wherein the core has a reduced thickness along a control interval of the fiber to enlarge a modal field diameter of the guided mode in the fiber. A control layer is disposed on an external surface of the cladding along the control interval. The control layer exhibits a change in its index of refraction as a function of temperature. The apparatus further includes a controller to change the temperature of the control layer to more than two different levels, responsive to more than two different, corresponding attenuation settings for an optical signal to be guided by the fiber. In another embodiment of the invention, a coreless optical fiber is fused to the cladding of the optical fiber at the control interval. The control layer is formed at least on the external surface of the optical fiber, and may further be formed on an external surface of the coreless optical fiber.
REFERENCES:
patent: 4426215 (1984-01-01), Murphy
patent: 4557557 (1985-12-01), Gleason et al.
patent: 4599098 (1986-07-01), Sarkar
patent: 4842358 (1989-06-01), Hall
patent: 4887900 (1989-12-01), Hall
patent: 4915503 (1990-04-01), Pavlath
patent: 4960319 (1990-10-01), Dankowych
patent: 5050956 (1991-09-01), Carpenter et al.
patent: 5701382 (1997-12-01), Grois et al.
patent: 5966493 (1999-10-01), Wagoner et al.
Webpage of Conference Abstracts, Optical Filter Communications (OFC) 2000, Mar., 5-10, 2000 Baltimore, Maryland, www.osa.oyg/mtg-conf/OFC/2000/head.htm.
Fused Fiber Optic Variable Attenuator, Val Morozov et al. submitted to Optical Society of America as a conference paper, OFC-Optical Filter Comm. Conference 2000 Mar. 5-10, 2000 Baltimore, MD.
Fused Coupler Switch Using a Thermo-Optic Cladding, (Author unknown), Electronic Letters, V. 24, No. 8, 1988.
Low-Power, Optically Switched Fibre Directional Coupler, T.V. Clapp et al., Electronic Letters. V. 25 No. 2, Jan. 19, 1989.
A Primer on Shadow™ Technology for Variable Optical Attenuation, Molecular OptoElectronics Corporation, Version 7/99, Jul. 1999.
Fan Haining
Morozov Val N.
Yang Long
E-Tek Dynamics
Greene Kevin E.
Lacasse Randy W.
Lacasse & Associates
Ullah Akm E.
LandOfFree
Variable optical attenuator with thermo-optic control does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Variable optical attenuator with thermo-optic control, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Variable optical attenuator with thermo-optic control will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2498900