Optical switching matrix

Optical: systems and elements – Deflection using a moving element – Using a periodically moving element

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Details

359117, 359121, 359128, H04J 1402, H04B 10207

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active

054852978

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to an optical switching matrix that can be used in particular in an exchange or node of an optical fiber data-transmission network. The matrix can also be used in any other routing member of such a network.
Such a matrix includes inputs and outputs, each input receiving data to transmitted, and each output transmitting, from the matrix, that data which is received via the input to which the output is temporarily connected. Switching signals are received by the matrix so as to control the beginning and the end of the period during which the output is connected to the input. Inside the matrix, data to be transmitted is carried by light waves.
An important characteristic of such a matrix is its ability to perform data collection operations easily when necessary, so as to collect a plurality of different items of data which are received via a plurality of respective inputs, and which are all to be transmitted to the same output.
A first known optical switching matrix includes the following elements (see FIG. 1): emitters being designated by the reference 100; each of the emitters has a wavelength at which it emits a carrier light wave; the wave is modulated by data to be transmitted that is received by the emitter, e.g. in electrical form; the emitters constitute tuned members that are tuned to wavelengths; respectively connected to Z emitters 100 and also with Z outputs, and it is referred to below as a "star distributor"; it permanently transmits a fraction of a mixture constituted by all the waves that it receives at its inputs to each of its outputs; such a distributor is often referred to in the literature as a "star coupler"; and
Z filters such as 104j, given the overall reference 104 and respectively connected to the Z outputs of the distributor 102; such a filter has a wavelength and constitutes a tuned member that is tuned to that wavelength; it selectively transmits those waves whose carrier wavelengths are equal to its own wavelength; the filters such as 104 are referred to below as "fixed" filters to indicate that their wavelengths are fixed.
The emitters are referred to below as "controlled" emitters to indicate that their wavelengths are controlled as a function of the switching signals that are received by the matrix, so that when data to be transmitted is received by an emitter 100i and when that data is to be transmitted in optical form to an output of a filter 104j whose wavelength is Lj, the emitter is tuned to that wavelength Lj, i.e. the wavelength of the emitter is made equal to Lj.
That first known matrix uses a technique referred to internationally as "wavelength routing". This technique is described in a document by Brackett entitled "Dense Wavelength Divisions Multiplexing Networks: Principles and Applications", Charles A Brackett, IEEE Journal on Selected Areas in Communications, Vol. 8, No. 6, August 1990 p 948-964.
That first known matrix may be referred to as a "wavelength-division" matrix because it uses different wavelengths of the optical spectrum.
A second known matrix is shown in FIG. 2, and may be referred to as a "space-division" matrix because it creates guided light paths that can be varied in three-dimensional space. For example, that matrix includes: optical form; to make the connections, the distributor receives switching signals which control the guided paths formed in the distributor between the inputs and the outputs; the paths are guided in the same way for waves that may have different wavelengths; such a distributor is well known and itself constitutes an optical switching matrix such as the matrix described in a document by Hermes entitled "Optical Routing--State of the art and future aspects", Thomas Hermes, Proceedings ECOC'86, pp 33-38; some such distributors enable data to be broadcast from one input to a plurality of outputs, while others enable data received via a plurality of inputs to be collected at one output.
Those known optical switching matrices suffer, in particular, from the drawback that

REFERENCES:
patent: 4873681 (1989-10-01), Arthurs et al.
patent: 5241409 (1993-08-01), Hill et al.
M. Akiyama et al "Photonic Switching System", Transactions Of The Institute Of Electronics, Information And Communication Engineers of Japan, vol. 74, No. 1, Jan. 1991, pp. 84-91.
C. A. Brackett, "Dense Wavelength Division Multiplexing Networks: Principles and Applications", IEEE Journal On Selected Areas In Communication, vol. 8, No. 6, Aug. 1990 pp. 948-964.
A. M. Hill, "A Distributed Wavelength Switching Architecture for the TPON Local Network", Proceedings, International Switching Symposium, May 27-Jun. 1, 1990, vol. III, pp. 21-26.
H. Obara et al, "Star Coupler Based WDM Switch Employing Tunable Device with Reduced Tunability Range", Electronics Letters, vol. 28, No. 13, Jun. 18, 1992, pp. 1268-1270.
M. Fujiwara et al, "Line Capacity Expansion Schemes in Photonic Switching", IEEE Transactions On Parallel And Distributed Systems, vol. 1, No. 2, May 1990 pp. 47-53.

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