Optical waveguides – With disengagable mechanical connector – Structure surrounding optical fiber-to-fiber connection
Reexamination Certificate
1999-09-30
2001-07-24
Sikder, Mohammad (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Structure surrounding optical fiber-to-fiber connection
C385S053000, C385S055000, C385S075000, C385S076000, C385S077000
Reexamination Certificate
active
06264373
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a transition between different types of optical-type fibers, and, more particularly, to a transition device that optically connects two different types of optical-type fibers together.
An optical fiber is formed of an optical glass core and a glass casing. Light travels through the core and is confined to the core by internal reflection from the glass casing. Light signals may be propagated over long distances with little loss of signal strength. For some optical fibers, a polymeric (e.g., acrylate) buffer layer overlies the core and casing to protect them.
As optical fiber technology has progressed, a number of different types of fiber structures have been developed for use in optical fiber systems. For example, laser diode light sources are available in fiber form. Light energy is input through the lateral surfaces of the laser diode fiber, and a monochromatic beam is produced from the end of the laser diode fiber. Each laser diode fiber is typically quite small in size, about 0.005 inch in diameter. To make a satisfactory light source for many applications requiring increased output energy, a number of the laser diode fibers may be bundled together.
In some applications, the light output of the laser diode fiber or fiber bundle must be introduced axially into a second optical-type fiber such as an optical fiber or an amplifier fiber. To accomplish the transition of the light from the laser diode light sources into the second fiber, the output must be focused onto the end of the second fiber. The devices currently available for performing the transition are generally not robust and can easily become misaligned or misadjusted. Further, they are not qualifiable for space applications.
There is a need for an improved optical transition device that accomplishes the transition function between optical devices of a fiber configuration, is robust, and may be qualified for space applications. The present invention fulfills this need, and further provides related advantages.
SUMMARY OF THE INVENTION
The present invention provides an optical transition device that connects two fibers in an end-to-end fashion, so that light emanating from one is transmitted into the other. The optical transition device is made with a high degree of precision, and that precision is retained in service in a variety of circumstances due to the nature of the construction and the closely matched coefficients of thermal expansion of the elements of the optical transition device. No active or manual alignment is required. The magnification of the light transition may be set according to mechanical elements used in the optical transition device. The optical transition device accommodates a wide variety of types and sizes of fibers on either side of the transition. The optical transition device is suitable for high power applications, such as up to 5 watts on the input side. The optical transition device is space qualifiable.
In accordance with the invention, an optical transition device comprises a first transition body having a first transition body bore therethrough, a first fiber connector connected to the first transition body and having a first connector bore therethrough, a second transition body affixed to the first transition body and having a second transition body bore therethrough, and a second fiber connector connected to the second transition body and having a second connector bore therethrough. The first connector bore, the first transition body bore, the second transition body bore, and the second connector bore are coaxial and aligned along a transition axis. A lens, preferably a graded-index lens for applications of interest to the inventors, is disposed within at least one of the first transition body bore and the second transition body bore with an optical axis of the lens coincident with the transition axis. An axial positioning structure is optionally disposed adjacent to the lens, to position the lens axially along the transition axis. Optionally, a heat sink overlies the first and second transition bodies.
This device structure rigidly aligns the fibers on either side of the transition and the lens. No manual or active alignment is required, and there is nothing to become misaligned with time, service, mechanical forces, shocks, or as a result of temperature changes. The materials of construction are all suitable for use in a space environment, and therefore the optical transition device is space qualifiable.
The nature of the fiber structures on either side of the transition determines the selection of the connectors. In one application, one connector (serving as an input connector) is adapted for connecting to a bundle of laser diode light sources, and the other connector (serving as an output connector) is adapted for connecting to an optical fiber, a laser fiber, or an amplifier fiber.
The axial positioning structure includes at least one of a first spacer disposed in the first transition body bore, a middle spacer disposed between the first transition body and the second transition body, and a second spacer disposed in the second transition body bore. The first and second spacers are positioned on each side of the lens, and more preferably a sleeve that holds the lens, so that the axial position of the lens along the transition axis is determined by the length of each spacer, which is established at the time of manufacture. The magnification and focusing of the optical transition device is thereby determined by the axial positioning of the lens.
The first transition body and the second transition body are desirably made of a material, preferably type
410
stainless steel, having a coefficient of thermal expansion close to that of the glass lens, to minimize differential thermal strains and the possibility of damage to the glass lens during temperature changes. The elements of the optical transition device are positively connected together by bolting, screwing, or the like. These features, in combination with the basic structure, give the optical transition device great resistance to loss of alignment.
The present invention therefore provides a readily manufactured, highly stable, versatile optical transition that may be used with many types of fiber structures. Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The scope of the invention is not, however, limited to this preferred embodiment.
REFERENCES:
patent: 4451114 (1984-05-01), Nicia et al.
patent: 4690487 (1987-09-01), Hale et al.
patent: 4784135 (1988-11-01), Boero
patent: 4930858 (1990-06-01), Veenendaal
patent: 5199093 (1993-03-01), Longhurst
Bristol Andrew J.
Fujimori Brian J.
Mader Thomas B.
Gudmestad T.
Hughes Electronics Corporation
Sikder Mohammad
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