Optical waveguides – With disengagable mechanical connector – Optical fiber/optical fiber cable termination structure
Reexamination Certificate
2000-06-02
2002-04-23
Patel, Tulsidas (Department: 2839)
Optical waveguides
With disengagable mechanical connector
Optical fiber/optical fiber cable termination structure
Reexamination Certificate
active
06375363
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to fiber optic telecommunications equipment and, in particular, to a shielding system and method for providing protection from laser energy emitted from a fiber optic cable.
2. Description of the Related Art
In the telecommunications and data transmission industries, optical fibers are used to transmit signals. The technology uses glass or plastic threads (fibers) to transmit data. A fiber optic cable consists of a bundle of glass threads, each of which is capable of transmitting messages modulated into light waves. Lasers provide the source for the light waves in a fiber optic communications system. The lasers in optical fiber communications systems operate at wavelengths ranging from about 600 nm to about 1550 nm. Today's fiber optic communications systems are growing larger and stronger, with higher intensity laser signals being driven over a larger number of optical fibers.
A hazard associated with fiber optic communications systems, because they employ laser technology, is the risk of harm to humans from exposure to laser light waves. Typical optical fiber communications systems are fully enclosed when operating normally. However, human exposure is possible when the closed system is broken, either intentionally or by accident. In such cases, there is a risk of harm to the human eye if certain portions of the eye are exposed to intense laser radiation. For instance, when laser radiation at wavelengths shorter than 1400 nm are focused on a very small point on the retina, local heating can result in damage to the photosensitive receptors in the retina. In most cases where excessive exposure occurs, the damage is permanent. If the radiation is focused on the portion of the eye called the macula, serious loss of central vision may occur. At 1550 nm, the anterior portions of the eye absorb the radiation. This may result in excessive heating, which may lead to corneal burning or cataract. Because the radiation at these longer wavelengths is not focused, the threshold for biological damage is greater than at shorter wavelengths.
What is needed is a system and method for shielding the operator of a fiber optic communications system from laser energy, while at the same time being practical for the operator to employ as well as requiring as little space as possible within a densely packaged fiber optic cabling system. It would also be desirable for the method and system to provide shielding without regard to the style of commercial connector used in the fiber optic communications system.
SUMMARY OF THE INVENTION
A multi-part shielding system includes a shielding device that automatically obstructs the energy source opening of a connector housing when no connector is present within the housing. In at least one embodiment, the shielding system includes a flexible shielding device that includes a relatively planar bias portion coupled between a fastening plate and a shield portion. The bias portion is coupled to a bias support member that provides support for the bias portion. The shield is at least as wide as the energy source opening and is configured to rest in a position, when no connector is present in the housing, that automatically obstructs the energy source opening. When a connector is inserted into the connector housing, a pressure force is applied to a pressure ledge. The pressure ledge and the shield are formed as a single, hollow, integral unit, and are coupled to the bias portion. The pressure force causes the bias portion to flex into a position that clears the energy source opening. In this manner, a connector may be inserted into the connector housing. While the connector remains in the connector housing, the connector supplies an obstruction force to the shielding device, causing the shielding device to remain in a yielded position. When the connector is removed from the connector housing, and the obstruction force is therefore removed from the shielding device, the bias portion of the shielding device causes the device to return to a rest position that again obstructs the energy source opening. The installation and removal of the shielding device may be accomplished without removing the connector from the connector housing.
In at least one embodiment, the shielding system includes multiple shielding devices coupled to the fastening plate.
In at least one embodiment, the shielding device is configured such that the pressure force and the obstruction force cause the shielding device to yield along a plane perpendicular to the fastening plate. In one embodiment, the shielding device yields downwardly. In another, the shielding device yields to the side.
In one embodiment, the fastening plate contains a mounting notch along an inside edge of a side portion of the fastening plate. In another embodiment, the fastening plate contains two mounting notches, one each on a first edge and a second edge of the fastening plate.
In at least one embodiment, the shielding system is coupled to a housing chassis. The housing chassis contains at least one connector housing into which an optical connector may be inserted. In at least one embodiment, the chassis contains multiple connector housings. The shielding system also contains, in at least one embodiment, multiple shielding devices.
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Bryan A. Tozer; “Telecommunications Systems: Minimize Laser Risks”; Feb. 1999;Phontonics Spectra; pp. 124-126.
Harrison Carl G.
Hoyl Bradley S.
Smart Denise L.
Bacon Shireen
Cisco Technology Inc.
Patel Tulsidas
Skjerven Morrill & MacPherson LLP
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