Optical waveguides – With optical coupler – Plural
Reexamination Certificate
2000-03-22
2002-04-02
Ngo, Hung N. (Department: 2874)
Optical waveguides
With optical coupler
Plural
Reexamination Certificate
active
06366717
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for carrying on simultaneous signal transmissions over a single optical fiber by using two different operating frequencies, and more specifically to an apparatus for combining bidirectional telephone signals and cable TV signals carried by optical fibers on a single optical fiber extending from a distribution cabinet to a multiplicity of user stations or first locations. The apparatus includes optical couplers for combining the telephone signals and the TV signals onto a single fiber and support and guide structure for organizing a multiplicity of such coupler and input and output fibers for easy access.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
The telecommunications industry is using more and more optical or light fibers in lieu of copper wire. Optical fibers have an extremely high bandwidth thereby allowing significantly more information than can be carried by a copper wire.
Of course, modem telephone systems require bidirectional communications where each station on a communication channel can both transmit and receive. This is true, of course, whether using electrical wiring or optical fibers as the transmission medium. Early telephone communication systems solved this need by simply providing separate copper wires for carrying the communications in each direction. Some early attempts at using optical fibers as a transmission medium followed this example and also used two different optical fibers such as optical fibers
10
and
10
A in the prior art
FIG. 1
for carrying the communications in each direction. As shown, in the prior art
FIG. 1
, fiber
10
is connected by an optical coupler
12
to an LED (light-emitting diode)
14
at one end and by optical coupler
16
to a PD (photodetection diode)
18
at the other end. Similarly, but in reverse, fiber
10
A is connected by an optical coupler
16
A to PD
18
A at one end and by optical coupler
12
A to LED
14
A at the other end.
However, because of extremely high bandwidths available for use by an optical fiber, a single fiber is quite capable of carrying communications in both directions. One technique is WDM (wavelength divisional multiplexing) which is shown in the prior art FIG.
2
and uses different wavelenghts for each direction of travel. Components in FIG.
2
and subsequent figures which operate the same as shown in
FIG. 1
carry the same reference numbers. In the embodiment shown in
FIG. 2
, a central office
20
is connected to an RT (remote terminal)
22
by a single optical fiber
10
B. As shown, the central office includes a light-emitting diode
14
optically connected to fiber optics
10
by optical coupler
12
for converting electrical signals to optical signals and a photodetection diode
18
optically connected to optical fiber
10
A by a coupler
16
for converting optical signals to electrical signals. The fiber optics
10
and fiber optics
10
A are each connected to a wavelength division multiplexer
24
which is connected to optical fiber
10
B. This arrangement is duplicated at the RT
22
by light-emitting diode
14
A, coupler
12
A, photodetection diode
18
A, coupler
16
A and wavelength division multiplexer
24
A. It will, of course, be appreciated that although the figure is shown as providing communications between a central office
20
(station
1
) and a remote terminal
22
(station
2
), the communications system could be used for providing communications between any two types of stations such as, for example, two central offices, two remote terminal offices, or between a remote office and an individual user's location, etc. A typical communications system using an LED and a PD with a single optical fiber is disclosed in U.S. Pat. No. 5,075,791 entitled “Method and Apparatus for Achieving Two-Way Long-Range Communication Over an Optical Fiber”, issued to Mark W. Hastings, and incorporated in its entirety hereby by reference.
Yet another and simpler technique for using a single optical fiber
10
C for telephone systems is illustrated in the prior art FIG.
3
. The illustrated figure is referred to as TCM (time compression multiplexing) and is sometimes referred to as a “ping-pong” system. The system operates at a single frequency and uses a single optical fiber
10
and a single diode
30
and
30
A at each end connected by optical couplers
32
and
32
A, respectively, for both converting electrical signals to optical signals and for receiving optical signals and converting those optical signals to electrical signals. TCM systems have the obvious advantage of requiring fewer components.
However, as mentioned above, optical fibers have extremely high bandwidths and use of an optical fiber for a single ping-pong telephone channel is a very ineffective use of the fiber and, in fact, the available bandwidth of an optical fiber makes it possible to use a transmission technique such as TCM or ping-pong at one frequency and then by the use of WDM technology to use another technique at a second frequency. Of course, where optical transmission systems such as a ping-pong or TCM system has been installed, it would not be desirable to disrupt the operation of such systems. Further, once a ping-pong fiber-optic telephone system is installed, removal and replacement with a new system would normally be prohibitive from a cost point of view. Therefore, it would be advantageous to be able to upgrade the existing TCM or ping-pong fiber-optic telephone system to also carry a second communication channel at another frequency.
SUMMARY OF THE INVENTION
It is an object of this invention to provide apparatus for upgrading a communication transmission system initially providing a communication channel operating at one frequency so that it can provide two communication channels operating at different frequencies.
It is another object of the invention to provide a method and apparatus to upgrade a communication transmission system while using as much of the existing telephone equipment and distribution frames as possible.
It is still another object of the invention to provide methods and apparatus to upgrade a fiber optic telephone transmission system to carry CATV signals with minimal addition of new components.
It is yet another object of the invention to allow upgrading of a optical fiber communication transmission system to occur on an on-demand-basis.
The present invention accomplishes these and other objects in apparatus for distributing optical transmission which comprises a plurality of first optical fibers which bidirectionally transmit light of a first wavelength. Each one of the plurality of first optical fibers has a first portion spliced to a second portion. There is also included a like or equal number or plurality of second optical fibers for transmitting light at a second wavelength and which, in a preferred embodiment, this second wavelength is used to carry cable TV signals. The plurality of first optical fibers and second optical fibers are provided to a similar plurality or like number of wave division optical couplers (WD) each of which has a first port connected to one of the plurality of first optical fibers and a second port connected to one of the plurality of second optical fibers. Each of the couplers combines light having a first wavelength and which is received from the first plurality of optical fibers at the first port with light having a second wavelength (the TV signals) and which is received from the second plurality of optical fibers at the second port to provide an output at a third port comprised of light carrying both first and second frequencies. The light output at the third port is provided to a similar plurality of third optical fibers which transmit the light at both first and second wavelengths to the user. Each one of the plurality of third optical fibers also has a first portion spliced to a second portion. The invention further includes a support structure or panel which supports the first, second and third
BuAbbud George H.
Radloff Georgeanne M.
Jones Day Reavis & Pogue
Marconi Communications Inc.
Ngo Hung N.
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