Optical waveguides – With disengagable mechanical connector
Reexamination Certificate
1998-03-03
2001-09-18
Healy, Brian (Department: 2874)
Optical waveguides
With disengagable mechanical connector
C385S100000, C385S138000, C174S07000A, C174S07100B
Reexamination Certificate
active
06290399
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical submarine branching unit.
2. Description of the Related Art
An optical submarine cable transmission system is widely used as international and domestic communications means, which is due to its higher transmission quality such as excellence in noise and delay time, and security over satellite communications or other conventional radio communications by means of short waves. In the optical submarine cable transmission system, a plurality of optical submarine repeaters are provided at given intervals to prevent degradation in transmission characteristics of an optical submarine cable and amplify signals. Each submarine repeater is driven by a constant current supplied from a feeding device installed on the land.
Thus, the optical submarine cable transmission system is composed mainly of an optical submarine cable and a plurality of optical submarine repeaters inserted in the optical submarine cable at given intervals. The system further includes an optical submarine branching unit for branching the optical submarine cable into a plurality of transmission lines in the sea, because many optical fibers are accommodated in the optical submarine cable and wavelength division multiplexed optical signals are transmitted in each optical fiber. The optical submarine branching unit is used generally to branch a trunk cable into first and second branch cables. Such an optical submarine branching unit is installed between optical submarine repeaters or between an optical submarine repeater and a land terminal device.
A conventional optical submarine branching unit has only a function of extracting a specific wavelength. Accordingly, in the case that optical signals having different wavelengths are to be separately received by individual terminal stations, it is necessary to design an optical submarine branching unit according to wavelength. That is, many kinds of optical submarine branching unit according to the number of wavelengths to be branched must be installed. Such an increase in kind of optical submarine branching unit causes an increase in number of preliminary optical submarine branching units that must be respectively added to the existing optical submarine branching units. Further, the increase in kind of optical submarine branching unit causes another problem that different components must be manufactured for the different branching units and different tests must also be made, resulting in a reduction in manufacturability.
To solve the above problems, a branching circuit unit accommodated in the branching unit must include a plurality of optical filter circuits each having a function of reflecting light having only a specific wavelength of plural wavelengths and an optical circulator having a function of transmitting light cyclically in a given direction. Further, it is essential to develop a system in which input/output portions of all the optical filter circuits and input/output portions of the optical circulator are introduced into a pressure housing of the branching unit through feed through elements provided in cover assemblies of the pressure housing, and a required wavelength is selected outside of the pressure housing by cable jointing installation.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an optical submarine branching unit which can branch a plurality of different desired wavelengths as required.
In accordance with an aspect of the present invention, there is provided an optical submarine branching unit for branching a trunk cable having a plurality of optical fibers into first and second branch cables each having a plurality of optical fibers, comprising a pressure housing comprising a cylinder and first and second covers fixed to the opposite ends of said cylinder; a branching circuit unit accommodated in said pressure housing; a first feed through assembly mounted to said first cover so as to extend therethrough, for introducing said optical fibers of said trunk cable into said pressure housing; and second and third feed through assemblies mounted to said second cover so as to extend therethrough, for introducing said optical fibers of said first and second branch cables into said pressure housing, respectively.
The branching circuit unit includes a feeding unit and a plurality of optical circuit units completely separated from the feeding unit. Preferably, each optical circuit unit is accommodated in a case, and the number of the optical circuit units is changed as required.
Each of the first, second, and third feed through assemblies includes a sleeve fixed to the first or second cover, and a pin inserted in the sleeve and having a plurality of bosses. Each of the bosses has a plurality of axial grooves each for receiving multiple layers of optical fibers extending along the pin. Further, a spacing between the sleeve and the pin is hermetically sealed by a solder.
The case comprises a base plate and a pair of transparent covers mounted on the opposite sides of the base plate. An optical circulator is mounted on one surface of the base plate, and an optical filter is mounted on the other surface of the base plate. The number of the optical circuit units can be changed according to the number of wavelengths of signal light to be branched.
The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing some preferred embodiments of the invention.
REFERENCES:
patent: 4441786 (1984-04-01), Hulin et al.
patent: 4773728 (1988-09-01), Kershaw
patent: 4784461 (1988-11-01), Abe et al.
patent: 5673644 (1997-10-01), Vanasse et al.
patent: 5726388 (1998-03-01), Ferland
patent: 5838871 (1998-11-01), Lebert et al.
Fujitsu Limited
Healy Brian
Song Sarah N.
Staas & Halsey , LLP
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