Optical waveguides – Optical fiber waveguide with cladding – With graded index core or cladding
Reexamination Certificate
2000-02-15
2003-07-01
Cherry, Euncha (Department: 2872)
Optical waveguides
Optical fiber waveguide with cladding
With graded index core or cladding
C385S092000, C385S137000
Reexamination Certificate
active
06587625
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an optical fiber device for use in a high-radiation environment, and more particularly, to a fiber optic device that is resistant to radiation-induced transmission losses.
BACKGROUND OF THE INVENTION
Optical fibers and optical fiber components are useful for telecommunication transmission and networking. Basically, optical fibers are thin strands of glass capable of transmitting information-containing optical signals over long distances with low loss. In essence, an optical fiber is a small diameter waveguide comprising a core having a first index of refraction surrounded by a cladding having a second (lower) index of refraction. As long as the refractive index of the core exceeds that of the cladding, a light beam propagated along the core exhibits total internal reflection, and it is guided along the length of the core. Typical optical fibers are made of high purity silica, and various concentrations of dopants may be added to control the index of refraction.
Recently interest has grown in the use of optical fibers and communications systems in high-radiation environments such as the outerspace, e.g., in low earth orbit and inter-planetary satellites. For example, a satellite communications system incorporating use of optical fibers is disclosed in U.S. Pat. No. 5,475,520, issued Dec. 12, 1995 to Wissinger, “Satellite Communications System.” However, the outerspace environment is deleterious to fiber optics. Outerspace presents a natural radiation environment, for example, due to the presence of energetic charged particles, x-rays, gamma rays, and heavy ions. This adverse radiation environment degrades the optical fiber's properties over a period of time resulting in a decrease in transmission throughput. This effect is particularly prominent in optical fibers containing rare-earth dopants. Exposure of the fibers to the radiation environment of outerspace can cause the fibers to suffer significant losses over time.
Thus, there is an interest in developing optical fibers and an optical fiber apparatus that would be suitable for use in high-radiation environments such as in outerspace, nuclear reactors, or undersea applications. In particular, it would be useful to have an optical fiber that would be resistant to degradation from radiation present in such environments.
SUMMARY OF THE INVENTION
Summarily described, the invention embraces an optical fiber apparatus adapted for use in a high-radiation environment, including a satellite communications system. The apparatus comprises an optical fiber, a housing surrounding the optical fiber and defining an enclosed space between the exterior surface of the fiber and the housing, and a concentration of deuterium or hydrogen gases disposed within the enclosed space. Applicants have discovered that the adverse effects of a high-radiation environment can be significantly reduced and nearly eliminated by maintaining the optical fiber in an environment of hydrogen or deuterium gases.
REFERENCES:
patent: 4685945 (1987-08-01), Freund
patent: 5153931 (1992-10-01), Buchanan et al.
patent: 5867618 (1999-02-01), Ito et al.
Abate Joseph A.
Ahrens Robert George
DiGiovanni David John
LuValle Michael James
Presby Herman Melvin
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