Optical waveguides – Optical transmission cable – Ribbon cable
Reexamination Certificate
1999-12-17
2001-03-20
Healy, Brian (Department: 2874)
Optical waveguides
Optical transmission cable
Ribbon cable
C385S115000, C385S100000, C385S024000
Reexamination Certificate
active
06205278
ABSTRACT:
The present invention relates to a cabling system for fiber optical networks which have a plurality of optical fibers used in each link, in particular networks which have one or more ribbon fibers in each link. The present invention also relates to a fiber optical network and in particular to an optical connector to be used in fiber optical networks, the network being the kind having a plurality of optical fibers used in each link, in particular a network which has one or more ribbon fibers in each link.
BACKGROUND
Fiber optical networks are nowadays built and widely expanded and there is a great interest in providing, in addition to branches to companies, institutions, etc. also branches to private subscribers, i.e. to apartments, private homes and estates, etc., in order to allow communication having high velocity and high capability. Then there is also an interest in reducing the costs for such installations. However, in fiber optical networks the most costly components generally are the cabling system and the laser devices used for injecting and modulating light signals transmitted in optical fibers. One way of reducing the cost is to use optical ribbon cables or ribbon fibers allowing cabling systems to be more easily handled. Then also array devices can be used provided with appropriate multifiber connectors. However, when building an optical fiber network, the final number of subscribers and the geographical distribution thereof are never fully known and thus the network must be dimensioned taking this into account. This will in almost all cases mean that in actual use of the network a number of fibers in links in the system will not be used. Then a corresponding number of the element devices of array devices will not be used. Also, the ribbon fibers are made in definite capacities including e.g. 4, 8 and 12 optical fibers. Then, if a connection line is to be built to a geographical location where one or two subscribers reside, perhaps a fiber ribbon holding four fibers is used, this resulting in that at least two fibers of the ribbon are not used. In this way the advantage of introducing fiber ribbons and device arrays can be lost.
Optical fiber networks/cabling systems having branching points are disclosed in e.g. the published European patent application No. 0 549 862 and the British published Patent application No. 2 167 609. Optical connectors for such networks/systems are disclosed in e.g. the published International patent application No. WO 93/22695 and the published British patent applications No. 2 191 598 and 2 255 652.
SUMMARY
It is an object of the present invention to provide a cabling system for a fiber optical network that uses the fibers of the cables in an efficient way.
The problem solved by the invention is thus how to provide a system for efficiently using a single optical cable holding a multitude of fiber ribbons, i.e. how to arrange that as small portions of the individual optical fibers as possible are not used in actual installation and also how to arrange in a simple way that a small number of line boards can be used.
Thus, generally, for transmitting to and receiving information on optical fibers from subscribers which reside at different geographical locations a single optocable is used holding a plurality of parallel ribbon fibers. The cable is connected to some central station, e.g. line boards in a telecommunication station. Array devices connected to the ribbon fibers can there be used for transmitting and receiving signals on the optical fibers of the cable. At a geographical location, where there are subscribers, a sufficient number of ribbon fibers are cut off and a fan-out is made for both cut-off ends, splitting the ends into individual fibers. In such a branching point, where there are more individual cut-off fibers than there are subscribers, the remaining cut-off fibers are connected through by means of interconnecting fiber pieces, so that these fibers continue uninterruptedly through the branching point. In another branching point there are more subscribers than individual fibers in the cut-off ribbon fibers and then the subscribers are connected to individual fibers both in the portions of ribbon fibers close to the line boards and to the cut-off portions distant therefrom. At the non-connected end of the cable suitable ends of the optical fibers therein are connected to each other, so that a subscriber for instance can be connected through a piece of fiber extending to the end of the cable, there through a short fiber piece to an end of another fiber, this other fiber extending to a branching point where it is connected through to a fiber extending directly to the central station. In this way the capacity of the ribbon fibers can be used efficiently, also in the case where at a place there are a number of subscribers which is not an even multiple of the number of individual fibers in a ribbon fiber.
Thus, this system reduces the above-mentioned disadvantage by combining partly filled ribbon fibers at a far end of a cable so that fully or almost fully used ribbon fibers are obtained. Thus, the cabling system is almost fully used and nearly all pieces of fibers are used for transferring information.
Thus, as described above, at each geographical location, where there are subscribers to be connected to the network, a sufficient number of ribbon fibers are cut off. This will in many cases result in that there are individual fibers which are not used in the cut-off ribbon fibers. Two or more such ribbon fibers holding a sufficient total number of unused fibers can then be connected to the same line board by a suitably designed connector. In this way a small number of line boards can be used and this number can then easily be increased to connect the ribbon fibers directly by removing the connector.
For connection to a line board a connector can be used having a first side and second side intended for connecting optical ribbon fibers, these sides being substantially flat and parallel to each other. A ribbon fiber interface is provided at the first side and at least two ribbon fiber interfaces are provided at the second side. All of the interfaces are preferably adapted for fibers ribbons comprising the same number of individual optical fibers. Each such fiber interface has connection points inside the connector. All connection points of the interface at the first side are connected by optical waveguides such as loose optical fiber pieces to connection points of interfaces at the second side, so that at least one of the connection points of each interface at the second side is connected to an optical waveguide. The remaining connection points of each interface at the second side are not connected to any other connection point.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the methods, processes, instrumentalities and combinations particularly pointed out in the appended claims.
REFERENCES:
patent: 5222179 (1993-06-01), Auteri
patent: 5367598 (1994-11-01), Devenish, III et al.
patent: 5561731 (1996-10-01), Cooke et al.
patent: 5604834 (1997-02-01), Beasley, Jr. et al.
patent: 6035088 (2000-03-01), Chandraiah et al.
patent: 0 549 862 A1 (1993-07-01), None
patent: 2 167 609 (1984-10-01), None
patent: WO 93/22695 (1993-11-01), None
Healy Brian
Telefonaktiebolaget LM Ericsson
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