Optical waveguides – With optical coupler – Plural
Patent
1998-11-16
2000-02-08
Palmer, Phan T. H.
Optical waveguides
With optical coupler
Plural
385 20, 385 21, 385 27, 385 31, 359109, 359154, 359333, G02B 628
Patent
active
060235438
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to optical telecommunications. More specifically, it relates to interconnecting two stations of a telecommunications system when the connection is to be a both-way connection. Each station then has a receiver terminal and a transmitter terminal which need to be connected respectively to the transmitter terminal and to the receiver terminal of the other station by a line interconnecting the two stations.
BACKGROUND OF THE INVENTION
In a known link providing such interconnection, the line interconnecting the two stations is a pair of lines, i.e. it has two individual lines set up in parallel between the two stations. Each individual line is constituted by optical fiber sections connected together in series. In order to compensate for line losses, each terminal includes amplifier apparatus which, for each line, has an optical amplifier which is typically constituted by an optically-pumped erbium-doped silica fiber. In general, the word "amplifier" is used below to designate a light guide that is suitable for amplifying a light wave when said light wave to be amplified travels therealong simultaneously with a pumping wave.
For the same purpose of compensating losses, in-line amplification apparatuses can also be distributed along the length of the link. Each of them then also includes one such amplifier for each line.
It is known to use in such amplifier apparatus a common pump or a plurality of common pumps for supplying the two pumping waves necessary for the two amplifiers. Passive optical couplers of the type having two groups of two branches can then direct a fraction of the power of said pump or said pumps to each of the amplifiers without interfering with their respective connections to the two individual lines of the link.
Furthermore, such a link must be robust, i.e. it must in particular be made in such a manner that the operation of the transmitters and of the receivers is disturbed as little as possible and as rarely as possible by light waves not intended for them.
Such robustness would appear to be obtained to a reasonable degree in the above-mentioned known link.
Another essential characteristic of such a link is the quantity of information it is capable of conveying per second. A link may have a plurality of information channels implemented by spectrum, time, or other multiplexing on one or more lines, and this quantity needs to be distinguished from the data rate of each channel. On this topic, it has been found that in some known links of the kind described above and that are already in operation, that the maximum quantity of information that was specified at the time they were established and which they are capable of conveying now appears to be insufficient.
This quantity could be increased either by increasing the data rate of the terminals of each line, or by increasing the number of terminals included in the stations and similarly increasing the number of lines interconnecting the stations, and in both cases that would be expensive. If increasing the number of terminals, a major portion of the cost of obtaining such an increase in the quantity of information would lie in setting up new lines.
SUMMARY OF THE INVENTION
A particular object of the present invention is to enable the quantity of information that can be conveyed by an optical link having two lines that are already installed to be increased at moderate cost without providing a corresponding increase in the number of optical lines and without decreasing the robustness of the link.
Another object of the invention is to enable a both-way optical link to be implemented at low cost that is robust and capable of conveying information at a high data rate.
Specifically, the invention provides amplification apparatus for a both-way optical link, said link conveying first and second carrier waves carrying information and propagating in light guides respectively in first and second mutually opposite directions. In known manner the apparatus comprises: light guides respectively conveying
REFERENCES:
patent: 5898801 (1999-04-01), Braun et al.
Cheng et al, "622 Mb/S, 144 km transmission using a bidirectional fiber amplifier repeater", IEEE Photonics Technology Letters, vol. 5, No. 3, Mar. 1993, New York, US, pp. 356-358.
Kannan et al, "Unrepeatered bidirectional transmission system over a single fiber using optical fiber amplifiers", IEEE Photonics Technology Letters, vol. 5, No. 1, Jan. 1993, New York US, pp. 76-79.
Delavaux Jean-Marc
Perrier Philippe
Alcatel Cit
Palmer Phan T. H.
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