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Fiber-Optic Communications Loop

IP.com Disclosure Number: IPCOM000042838D
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 3 page(s) / 45K

Publishing Venue

IBM

Related People

Balliet, L: AUTHOR

Abstract

The fiber-optic communications loop configuration described herein permits the use of simpler forms of optical fiber switches to provide the station bypass function for the user stations connected to the loop. In particular, a single-pole, double-throw fiber switch can be used to provide the bypass function. A particularly useful form of construction for such a switch is also described. Fig. 1 shows a portion of a communications loop, which portion includes user stations A, B and C which are interconnected by means of optical fiber cables 1 and 2. In practice, the lengths of the cables 1 and 2, located between adjacent stations, may be anywhere from a few feet up to several thousand feet. Each station includes a single-pole, double-throw optical fiber switch 3 for providing the station bypass function.

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Fiber-Optic Communications Loop

The fiber-optic communications loop configuration described herein permits the use of simpler forms of optical fiber switches to provide the station bypass function for the user stations connected to the loop. In particular, a single-pole, double-throw fiber switch can be used to provide the bypass function. A particularly useful form of construction for such a switch is also described. Fig. 1 shows a portion of a communications loop, which portion includes user stations A, B and C which are interconnected by means of optical fiber cables 1 and 2. In practice, the lengths of the cables 1 and 2, located between adjacent stations, may be anywhere from a few feet up to several thousand feet. Each station includes a single-pole, double-throw optical fiber switch 3 for providing the station bypass function. (Suffix letters a, b and c are used to distinguish between the corresponding elements in the different stations.) The bypass function is needed to maintain loop continuity in the event a particular station should break down, be turned off, or the like. Each fiber switch 3 includes an input connector 4 and a pair of output connectors 5 and 6. A movable fiber element 7 is attached to the input connector 4, and a pair of stationary fiber elements 8 and 9 are attached to the output connectors 5 and 6, respectively. These fiber elements are short lengths of optical fiber cable. Each station further includes a normal operating mode optical receiver 10 and a bypass mode optical receiver 11. These receivers convert the received light signals into electrical signals which are supplied to an interface controller 12. This interface controller 12 supplies electrical signals to an optical transmitter 13 which converts them into light signals and applies the light signals to the optical fiber cable 1 which runs to the next station. The interface controller 12 is also connected to the user equipment 14 for that particular station. This user equipment may be, for example, a data processor or digital computer. For the sake of distinction, optical cables are represented by heavy inked lines and electrical cables are represented by lighter-weight inked lines. Fiber switch 3a in station A is shown in the normal operating mode position. In this case, light signals received from the preceding station are supplied by way of fiber elements 7a and 8a to the normal mode receiver 10a. If the coding of these signals indicates that they are intended for the user equipment 14a connected to station A, then the interface controller 12a supplies them to the user equipment 14a. If they are instead intended for some other station on the loop, then the interface controller 12a supplies such signals to the transmitter 13a to send them on around the loop. If the user equipment 14a wishes to place signals on the loop for transmission to another station, then such signals are supplied by way of the interface controller 12a to the transmitte...