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1. (WO1992010770) A METHOD AND ARRANGEMENT FOR OPTICAL SWITCHING
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CLAIMS

1. An optical switch for wavelength multiplexed optical signals, comprising
- a first number (N) of inputs (33A-33N9);
a second number (M) of outputs (38A-38M);
a first number (N) of optical switching elements (45A-45N) arranged between the inputs and the outputs, wherein the optical switch is intended to coact with: - a first number (N) of input links (23A-23N), each connected to a respective input (33A-33N) and each transmitting first wavelength multiplexed signals


a second number (M) of output links (24A-24M), each connected to a respective output and each transmitting second wavelength multiplex signals
( Aj... λn) ,
c h a r a c t e r i z e d by
a first number (N) of first optical splitters
(35A-35N), each of which is arranged between a respective input (33A-33N) and a respective optical switching element for splitting the signals on each of the inputs into a third number (n) of branches (36Al-36An, ... 37Nl-37Nn), wherein there is formed a first number (N) of groups, each comprising a third number (n) of branches;
a first number (N) of groups, each comprising a third number (n) of tunable first optical wavelength filters (39Al-39An, ..., 39Nl-39Nn), wherein each group of tunable wavelength filters is connected between a respective first optical splitter and a respective optical switching element, and each optical wavelength filter in each group forms a wavelength channel
(4lA1.4lAn, ..., 41Nl-41Nn);

a second number (M) of first optical couplers (34A-34M), each of which is arranged between a respective output (38A-38M) and a respective optical switching element (45) for coupling optical signals from predetermined switching elements to said outputs;
- control means (40) for controlling the tunable first optical wavelength filters and for controlling the optical switching elements.

2. An optical switch in accordance with claim 1, ch a r a c t e r i z e d in that said control means (40) is adapted to select the wavelengths for the optical signals on the inputs and the outputs and in the wavelength channels from among 2n-l different wavelengths, where n is the third number, and wherein the first (N), the second (M) and the third number (n) are each any desired integer so as to prevent two identical wavelengths from occurring simultaneously on both the input links and the output links.

3. An optical switch according to one or more of the preceding Claims, c h a r a c t e r i z e d by a first number (N) of groups, each comprising a third number (n) of transmitters (21A-21N) for transmitting optical signals on different wavelengths within each transmitter group;
a second number (M) of groups, each comprising a third number (n) of receivers (22A-22M) for receiving optical signals on different wavelengths within each receiver group;
- a first number (N) of second optical couplers
(27A-27N), each being arranged between a respective group of transmitters and each of the input links (23A-23N), more specifically the transmitting sides of the links; and
- a second number (M) of second optical splitters (28A-28M), each being arranged between a respective output link (24A-24M), more specifically the
receiving sides of the links, and a respective group of receivers;
- wherein the guide means (40) are arranged also to control the transmitters and the receivers so that their wavelengths are chosen from among said 2n-l wavelengths.

4. An optical switch according to Claim 3, c h a r -a c t e r i z e d in that each transmitter includes a respective second tunable optical wavelength filter

(31Al-31An, 31Nl-31Nn); and in that each receiver includes a respective third tunable optical wavelength filter (32Al-32An, ... 32Ml-32Mn).

5. An optical switch according to Claim 4, c h a r a c t e r i z e d in that each of the first, second and third tunable optical wavelength filters
(39, 31, 32) can be tuned to each of said 2n-l dif-ferent wavelengths.

6. An optical switch according to Claim 5, c h a r a c t e r i z e d in that each tunable optical wavelength filter (39, 31, 32) includes an optical ampli-fier.

7. An optical switch according to Claim 6, c h a r a c t e r i z e d in that the optical amplifier is a laser of the type DBR (Distributed Bragg Flector) or DFB (Distributed FeedBack) which is pumped optically to a moderate extent.

8. An optical switch according to Claim 7, c h a r a c t e r i z e d in that each optical switching element (45A-45N) includes, in a known manner, optical amplifying elements, each of which is intended to amplify solely one wavelength channel.

9. An optical switch according to Claim 8 in which each optical switching element includes a third number (n) of inputs (43Al-43An, ... 43Nl-43Nn) and a second number (M) of outputs (38Al-38Am, ... 38N1-38NM) and means for establishing a connection between a selected input and a selected output of respective switching elements, c h a r a c t e r i z e d in that each input of an optical switching element is connected to a respective one of said third number (n) of wavelength channels (41Al-41An, ... 41Nl-41Nn).

10. An optical switch according to Claim 9 in which each first optical coupler (34A-34M) has a first number

(N) of inputs (36Al-36An, ... 36Nl-36Nn) and one single output, ch a r a c t er i z e d in that each of the inputs to said second number (M) of first optical couplers (34A-34M) is connected to a respective one of said second number (M) of outputs of a respective one of said first number (N) of optical switching elements.

11. An optical cross connector comprising an optical switch (30) according to Claim 1, in which the input and output links (23A-23N, 24A-24N) are included in a network of trunk lines which conduct wavelength multiplexed optical signals, c h a r a c t e r i z e d by a digital cross connector (50) having an input side (51) and an output side (52);
- a fourth number (L) of optical third splitters
(55A-55L), each connected between a respective predetermined output optical link and inputs on the input side of the optical coupler;
a fourth number (L) of first groups, each comprising a third number (n) of tunable optical wavelength filters (59Al-59An, ... 59Ll-59Ln), wherein each wave- length filter group is connected between a respective splitter on the input side of the cross connector and each wavelength element in each group forms a wavelength channel;
- a fourth number (L) of third optical couplers
(56A-56L), each having an output and a third number (n) of inputs, wherein each output is connected to a respective input (33M-33N) of first optical splitters (33M-33N), predetermined from among said first number (N);
a fourth number (L) of second groups, each comprising a third number (n) of tunable optical wavelength filters (58Al-58An, ... 58Ll-58Ln), wherein each second wavelength filter group is connected between a respec-tive third optical coupler (56A-56L) and the output side (52) of the digital cross conenctor;
said control means (40) being also arranged to control the first and the second groups of optical wavelength elements (59, 58) such as to redistribute optical signals on the output predetermined links to inputs selected from the predetermined optical splitters at the optical switch.

12. A method for switching groups of optical signals from the inputs of an optical switch to the outputs of said switch in a blocking free and optically uninterrupted fashion, in which method each group is transmitted on a respective optical link and the signals in each group are wavelength multiplexed, c h a r a c -t e r i z e d by expanding the wavelength domain to 2n-l different wavelengths, transmitting a predetermined number (n) of wavelengths on each link, and selecting the predetermined number of wavelengths from among said 2n-l wavelengths.