Supports: cabinet structure – With movable components – Horizontally movable
Reexamination Certificate
1999-12-06
2001-11-27
Cuomo, Peter M. (Department: 3636)
Supports: cabinet structure
With movable components
Horizontally movable
C312S244000, C312S334400, C108S108000, C108S147170, C248S244000
Reexamination Certificate
active
06322178
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a portable workstation for rack mounting, and more particularly, to a workstation for field use when servicing fiber optic telecommunications equipment. The workstation includes a special mounting fixture which provides a means for mounting the workstation on a fiber optic telecommunications rack, ladder, pedestal, or other stationary field stand. The workstation includes a storage area for tools and supplies, and a clean work surface for working on the fiber optic and related communications equipment.
SUMMARY OF RELATED ART
Fiber optic technology is the transmission of energy by light through glass fibers, and is used to transmit and receive analog and digital signals. Fiber optic cable is the premier medium to meet the demand for higher speeds and greater information carrying capacity. Telephone, cable television, communication companies, and other businesses around the world are investing billions of dollars in fiber optic lines which have an enormous capacity for carrying data. Because of the advantages of fiber optic systems over conventional electrical and electronic components and systems, significant growth and expansion is anticipated in the use of fiber optic systems.
One of the main advantages of the fiber optic system is the ultra clear and clean signals in such system. Fiber optic systems are non-conductive, and are not effected by interference from radio frequency or electromagnetic fields. The losses associated with the transmission of fiber optic signals are significantly less than the losses in an electrical system. Another major benefit of a fiber optic system is the greater information carrying capacity. The fiber optic cable is significantly smaller and lighter in weight than the comparable copper conductors required for equivalent transmission capabilities. Optical data is transmitted through fiber optic cable at speeds up to 100 times faster than data transmitted using copper wire.
A typical fiber optic system consists of a transmitter, a transmission medium, and a receiver. The transmission medium is a fiber optic cable which includes a core made from extremely pure glass drawn out into a fine strand that is strong and flexible. The fiber optic cable also requires an outer sheath or cladding formed around the highly transparent core of glass that carries the light. The cladding reflects light back into the core such that the light is propagated by internal refraction. Fiber optic cable is classified by transmission type (single mode, graded index multimode, etc.) and by core/cladding diameter (i.e. 62.5/125 microns).
The single mode fiber only propagates one mode of light which makes it highly efficient. This type of cable is used with laser sources and requires an exact coupling alignment to a well-defined beam of light. The graded index multimode fiber exhibits a variable core density cross-section, which reduces intermodal dispersion and acts to focus broader bandwidths of reflected light into the fiber's core. Precision alignment of splices and connections are also essential in the graded index multimode fiber.
The single mode and/or multiple mode fibers can be assembled into multi-fiber bundles with a single outer cover. The bundles may include a central strength member for additional strength during installation. The bundle is designed to facilitate the splitting out of individual fibers for connection purposes.
The core size may be as small as 10 microns in diameter for a single mode fiber and as large as 85 microns for a multiple mode fiber. When the cladding is included, the total diameter for a single mode fiber can range up to 125 microns. The single mode fiber is very efficient at transmitting light, but such fiber has a small numerical aperture and is not effective in gathering light. Consequently, the single mode fiber is generally used for long distance applications with laser light transmitters, which can provide a concentrated beam of light. The multiple mode fiber has a much larger numerical aperture, but is less efficient at transmitting the light. The multiple mode fibers are used with light emitting diodes with a broader light wave for more local applications (50 miles or less). The diameter for multi mode fibers ranges from 125 microns to 400 microns.
In fiber optic systems, engineers and technicians perform power budget calculations to determine original and periodic operational system integrity in regard to attenuation. The transmitter spectral output power and receiver maximum sensing range are compared to the system losses in the fiber, connectors, splices, and couplers. The transmitter and receiver must be sized to ensure power to propagate the signal from the source to the receiver.
The total attenuation is significantly affected by the quality of the connections and/or splices in the fiber optic system. The losses at a dirty or poor quality connection can easily increase losses in the fiber optic system by as much as ten times the projected amount for a high quality connection. Poor quality connections are the most frequent cause of power loss, which results in operating defects and breakdowns in the fiber optic system.
Each fiber optic system will have optical connections at each junction between a fiber optic cable and a light source or detector. Connections are also needed to join or splice together the ends of two cables. Since each fiber optic system will include a number of junctions of fiber optic cable, it is essential that the technicians working on fiber optic cables in the field have a clean and convenient surface for properly connecting the fiber optic cables.
In the installation of a fiber optic system, transmitters and receivers may be positioned throughout the system at the desired locations for transmitting and receiving signals. The transmitters and receivers are mounted in a light interface unit which includes both electrical receptacles for input/output of electrical signals and lighting receptacles for the input/output of light signals. After the light interface units with transmitters and receivers have been installed and the cable between the light interface units pulled, one of the final field steps to complete the installation is connectorization, which is the connection of fiber optic connectors to the ends of the fiber optic cables to facilitate the proper alignment of the core of the fiber optic cable at the fiber optic connections.
The fiber optic cables used in a system will have a connector secured to each end of the fiber optic cable, the connector being designed for insertion and locking in the receptacle. The cable is stored on spools and is pulled from the spools in the field during installation. Several different types of receptacles and connectors are available for use in fiber optic systems.
The connectorization will typically occur at a telecommunications rack. The racks come in various sizes, but the two standard widths for such racks are 19 inches and 23 inches. The light interface units and the other components in the system are mounted on the rack. The racks are frequently mounted in a storage area or other enclosed facility where space is at a premium.
The connectors are usually installed on the fiber optic cable in the field at the time of installation. The fiber optic cable is stripped of its protective covering and the glass core and cladding are inserted into the connector such that the glass core extends from the ferrule at the end of the connector. The cable is epoxied into the connector and the glass core at the end of the ferrule is cleaved and polished using a lapping process.
The polished end of the core of the cable must be inspected to ensure that the end surface is clean and scratch free. Any scratches or cracks in the end of the glass fiber will adversely effect the integrity of the connection. Even body oils, lint or dust can cause unacceptable losses at the connection.
Because a good connection is essential to the overall efficiency of the system, a technician working on fiber op
Cuomo Peter M.
Fisher Michael J.
Wolfe John
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