JPH0946737A - Optical exchange - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the optical exchange of a simple structure provided with non-closability in which loss is less than before. SOLUTION: This optical exchange is provided with the M pieces of wavelength demultiplexing elements 11 for demultiplexing the optical signals of a wavelength multiplicity N to the light of respective wavelengths, the N pieces of optical switches 13 of M input and L output capable of simultaneously and independently switching the plural pieces of the light of the different wavelengths and the L pieces of multiplex elements 15 of N input and 1 output. Then, the (M×N) pieces of output ports in the M pieces of the wavelength demultiplexing elements 11 are connected to the (M×N) pieces of input ports in the N pieces of the optical switches 13 without overlapping so as to input the light of at least two kinds of wavelengths to the same optical switch. Further, the (N×L) pieces of the output ports in the N pieces of the optical switches 13 are connected to the (N×L) pieces of the input ports in the L pieces of the multiplexing elements 15 without overlapping so as to connect the output ports of the same optical switch to the different multiplexing elements. In this case, the M and the L are integers equal to or more than two and the case of being M=L is included as well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical switch which performs circuit switching of optical signals in wavelength-multiplexed optical fibers.

[0002]

2. Description of the Related Art Conventionally, an apparatus of this type is disclosed in, for example, Document I.
("Introduction to Optical Switching Technology", edited by Kenichi Yukumatsu, Ohmsha, (1993.9), especially pp.42-43). Specifically, (a).
² (M is the number of I / O ports) Gate type,
(b). A combination of a frequency (wavelength) demultiplexing / multiplexing element and a space division type optical matrix switch operating at one wavelength, (c). 2 × 2 type multi-wavelength optical switch (for example, see FIG. 3 later). 2 × 2 type optical switch, which will be explained using M)
This is an M-type element.

[0003]

SUMMARY OF THE INVENTION
The device of the configuration (a) has a drawback that the output light is attenuated to 1 / M ² . Further, in the device having the configuration of (b), the optical matrix switch used must be completely unblocked in order to be completely unblocked, so the structure and control become complicated, and as a result, the number of lines is limited. Further, in the device having the configuration of (c), it is necessary to use a large number of 2 × 2 type multi-wavelength optical switches (on the order of M ² ) and perform complicated wiring in order to achieve complete non-blocking. In addition, both the configuration of (a) and the configuration of (c) are maximum in one 2 × 2 multi-wavelength optical switch or gate,
Since we have to handle only the optical wavelength of wavelength multiplicity N,
For example, there is a drawback that the driving power and driving circuit of the 2 × 2 multi-wavelength optical switch are increased accordingly.

[0004]

Therefore, in the first invention of this application, M wavelength demultiplexing elements for demultiplexing an optical signal of wavelength multiplicity N into light of individual wavelengths and M input L output. An optical switch comprising N optical switches capable of simultaneously and independently switching a plurality of lights having different wavelengths and L optical multiplexers having N inputs, wherein the M wavelength demultiplexers are provided. The M × N output ports of the device are connected to the M × N input ports of the N optical switches so that at least two kinds of wavelengths of light are input to the same optical switch without duplication. The output ports of the same optical switch are different from each other without overlapping the N × L output ports of the N optical switches with the N × L input ports of the L multiplexing elements. Optical exchange connected so that it is connected to the element Claims. However, M and L are 2
The above integers are included, including the case where M = L.

In the optical switch according to the first aspect of the present invention, light of wavelengths from 2 types up to M types is input to one optical switch, but the number of wavelengths handled by the optical switch is independent of the wavelength multiplicity N. it can. Further, when light of the same wavelength is input to all the input ports of one optical switch, the non-blocking property of the optical switch may not be secured, but in the present invention, one optical switch has at least two types of wavelengths. Since light is input, the non-blocking property is easily ensured (for details, refer to the section of the invention). Regarding the value in the range of 2 to M, the larger this value is, the higher the non-blocking property of the optical switch is, but the wavelength handled by one optical switch is increased. It is good to decide in consideration.

Further, in the second invention of this application, there are M wavelength demultiplexing elements for demultiplexing an optical signal of wavelength multiplicity N into P sets by combining wavelengths, and an optical switch with M input and L output. An optical switch having P optical switches capable of simultaneously and independently switching a plurality of lights having different wavelengths and L multiplexing elements having P inputs and 1 output, wherein the M wavelength demultiplexing elements are provided. At least two sets of different wavelength combinations are input to the same optical switch without overlapping the M × P output ports in M with the M × P input ports in the P optical switches. Further, the L × P output ports of the P optical switches are not overlapped with the L × P input ports of the L multiplexing elements of the same optical switch. Multiplexing element with different output ports Claiming optical switch which is connected to be connected. However, M and L are integers of 2 or more and include the case of M = L. Further, P is an integer that satisfies 2 ≦ P <N. Further, each of the groups divided into P groups may have the same number of wavelengths, or some groups or all groups may have different number of wavelengths.

In the case of the second invention, it is possible to reduce the number of N optical switches required in the first invention to P.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. However, the drawings used for the description are only schematically shown so that the present invention can be understood. In each figure, the same components are denoted by the same reference numerals.

1. Description of Embodiments of First Invention 1-1. Description of Configuration FIG. 1 is a diagram showing an optical switchboard 10 according to a first aspect of the first invention. The optical switch 10 includes M wavelength demultiplexing elements 11 for demultiplexing an optical signal having a wavelength multiplicity N into lights having individual wavelengths, and is an optical switch having M inputs and L outputs, and is capable of generating a plurality of lights having different wavelengths. It has N optical switches 13 that can be simultaneously and independently switched and L optical multiplexing elements 15 with N inputs and 1 output. In FIG. 1, 10a is an input port of the optical switch 10 and 10b is an optical switch 10 respectively.
Is the output port of.

Here, each wavelength demultiplexing element 11 is 1
It can be constituted by a wavelength demultiplexing element having an input N output, for example, a known interferometer or a grating. Further, each optical switch 13 is, for example, a 2 × 2 type optical switch (hereinafter, also referred to as a “predetermined 2 × 2 type optical switch”) that can simultaneously and independently switch a plurality of lights having different wavelengths. It can be configured by a multi-wavelength router 13 that is connected in multiple stages (for example, connected to form a Banyan network) so as to have an input L output scale. As a specific design method for connecting a predetermined 2 × 2 type optical switch in multiple stages, for example,
When the larger value of M and L is given by 2 ⁿ (n is a positive integer of 2 or more), a predetermined 2 × 2 type optical switch may be connected in log ₂ M (L) stages. . Where M
(L) means to take a larger value of M and L. A specific example of the multi-wavelength router 13 will be described below with reference to FIGS. 2 and 3. Here, FIG. 2 shows a predetermined 2 × 2
Type optical switch 13x has M inputs and L outputs (here, N = L
= 8), an example of wavelength routers connected in multiple stages so that the scale becomes 8) is shown. Further, FIG. 3 shows a specific configuration example of the predetermined 2 × 2 type optical switch 13x. Each of the 2 × 2 type optical switches 13x includes a first polarization separation element (PBS) 13xa, a polarization converter 13xb using AO (acousto-optic effect), and a second polarization separation element (PBS). )
13xc is arranged in series. However, the polarization converter 13xb is configured to generate SAW (surface acoustic wave), and therefore the electrode 13 for generating SAW is used.
It has y. In this 2 × 2 type optical switch 13x, a plurality of input light beams having different wavelengths are independently controlled by using surface acoustic waves having a plurality of different frequencies, and a cross state and a bar state are obtained with respect to each wavelength light. And can be realized. This 2 × 2 type optical switch 13x is disclosed in
II (Science Technical Report OSC94-38 (1994-07)), TE-TM mode conversion type acousto-optic filter (AO
It can be composed of elements described in detail as TF).
Each of the multiplexing elements 15 can be composed of a known one having N inputs and 1 output.

The M wavelength demultiplexing elements 11, the N optical switches 13 and the L multiplexing elements 15 are connected as follows. First, the M wavelength demultiplexing elements 1
1. The M × N output ports 11o (see FIG. 1) in 1 are connected to the M × N input ports 13i (see FIG. 1) in the N optical switches 13 without duplication. However, the same optical switch is connected so that lights of at least two types of wavelengths are input. Further, the N × L output ports 13o of the N optical switches 13 do not overlap with the N × L input ports 15i of the L multiplexing elements 15, but the output ports of the same optical switch are different. It is connected so as to be connected to the multiplexing element.

Regarding the connection relationship, particularly the connection relationship between the wavelength demultiplexing element 11 and the optical switch 13,
The wavelength multiplicity N is 6, and the scale of the optical switch 13 is 4 × 4.
(Thus, M = L = 4) will be described in more detail. This will be described with reference to FIG. In FIG. 4, a circle indicates an optical switch 13 of 4 × 4 scale.
Is an input port in. In this case, wavelength multiplicity N = 6
Therefore, four input ports of each of the six optical switches, that is, a total of 24 input ports are shown.
However, the input ports belonging to the same optical switch are denoted by the reference numeral assigned and the same number lines of the same pattern (such as 13 _1). That is, the first to sixth corresponding to the wavelength multiplicity of 6
Regarding the input ports of each of the 6 optical switches of, the input port of the first optical switch is shown by adding 13 _1.
..., the input port of the sixth optical switch is shown denoted by the 13 _6. Further, in FIG. 4, the vertical axis represents wavelength. In this case, an example using six types of wavelengths λ _{1 to} λ ₆ is shown. Then, in the case of the example of FIG. 4, for example, the first
The four input ports 13 ₁ of the optical switch of
₄ , four types of light of wavelength λ ₃ , wavelength λ ₂ and wavelength λ ₁ are input, ..., Four input ports 13 ₆ of the sixth optical switch have λ ₃ , λ ₂ and λ ₁ , Λ _{6 so} that four types of light are input, the wavelength demultiplexer 11 and the optical switch 13
And are connected. However, it is preferable that the lights of four kinds of wavelengths input to the same optical switch are not output from the same wavelength demultiplexing element but are output from different wavelength demultiplexing elements. . This is because it is possible to reduce the number of wavelengths controlled by one optical switch.

In the case of the optical switch 10, M × N = L × Q must be established in order for the input and output lines to have the same capacity. However, Q is the wavelength multiplicity at the output port 10b of the optical switch 10. However, when a wavelength router having a Banyan network is used as the optical switch 13,
Normally, the Banyan network is M × M type, that is, M = L in this example.
Therefore, in order to make the input and output lines have the same capacity, N = Q.

1-2. Description of Operation In the optical switch 10 according to the first embodiment of the first invention, the optical signal having the wavelength multiplicity N input to the input port 10a is wavelength-demultiplexed by the wavelength demultiplexing element 11 and is used as an optical switch (multi-wavelength router). ) 13 input ports to the optical switch 13. The input light is controlled by the multi-wavelength router 13 and output to a predetermined output port 10b. FIG. 2 shows an example in which the optical switch 13 has an 8 × 8 scale, and light of wavelengths λ ₁ to λ ₈ is separately input to the _eight input ports 13i and is exchanged. ing. Here, the 2 × 2 type optical switch 13x in the optical switch 13 can independently control light of each wavelength. It can be said that this can perform a completely non-blocking type operation unless different signals of the same wavelength compete with one 2 × 2 type optical switch. In such a case, if the connection relationship described with reference to FIG. 4, that is, the configuration in which optical signals of different wavelengths are input to each input port of the optical switch (multi-wavelength router) 13, one 2 × 2 type optical switch Since different signals of the same wavelength do not compete with each other, even if the optical switch 13 is a Banyan network as shown in FIG. 2, it operates as a completely non-blocking type.
Further, in the case of the optical switch of the first mode, the output power is 1 / the input power due to the property of the single mode multiplexing element.
Although it is N, the loss can be reduced, for example, as compared with the device having the configuration (a) described in the prior art (same in the following modified examples).

1-3. Second and Third Modes In the example shown in FIG. 4, the wavelength demultiplexing element 11 and the optical switch 13 are connected so that light of different wavelengths is input to each input port of one optical switch 13. However, instead of doing so, the two may be connected as follows.

When the optical switch (multi-wavelength router) 13 is composed of a Banyan network, the input port of this optical switch 13 is divided into two groups, and the wavelengths of the same combination are input to each group so that wavelengths of the same combination are input. The wave element 11 and the optical switch 13 may be connected (second mode). Even in this case, the optical switch 13 operates as a completely non-blocking type. Specifically, for example, in the case of an example of an optical switch 13 having eight input ports as shown in FIG. 5, two sets of first to fourth input ports and fifth to eighth input ports are provided. It is like inputting light with a combination of wavelengths λ _{1 to} λ ₄ . Of course, this input example is an example. A connection example when the connection relation in the second mode is applied to an optical switch having a wavelength multiplicity N of 6 and a scale of the optical switch 13 of 4 × 4 (thus M = L = 4) is , For example, as shown in FIG. In the example of FIG. 4 described above, light of four types of wavelengths was input to one optical switch, but in the example of FIG. 6, light of two types of wavelengths is input to one optical switch. Become.

Further, the wavelength demultiplexing element 11 and the optical switch 13 may be connected so that a set of wavelengths is input to one optical switch 13 (third mode). FIG. 7 shows an example in which the wavelength multiplicity N is 6 and the scale of the optical switch 13 is 4 × 4 (hence M = L = 4). Each light of λ ₄ , λ ₂ , λ ₆ , λ ₄ is input to the input port 13 ₁ of the first optical switch, ..., λ ₃ , λ is input to the input port 13 ₆ of the sixth optical switch. _This is an example in which light of ₁ , λ ₅ and λ ₃ is input.
Light of λ ₄ is input as a set to the first optical switch,
..., in the example in which light of λ ₆ is input as a set to the third optical switch, and ..., light of wavelength λ ₃ is input as a set to the sixth optical switch. That is, in this case, light of three different wavelengths is input to each optical switch 13. Even with such a connection, the optical switch operates as a non-blocking type.

2. Description of Embodiment of Second Invention Next, an embodiment of the second invention of this application will be described. The optical switch of the second invention is basically the same as the first invention except that the degree of demultiplexing and the number of optical switches are different from those of the first invention. Therefore, illustration is omitted. The optical switch according to the second aspect of the present invention includes M wavelength demultiplexing elements for demultiplexing an optical signal having a wavelength multiplicity N into P sets by combining wavelengths,
The optical switch has M inputs and L outputs, and includes P optical switches capable of simultaneously and independently switching a plurality of lights having different wavelengths, and L P-input 1-output multiplexing elements. Then, the M × P output ports of the M wavelength demultiplexing elements do not overlap with the M × P input ports of the P optical switches, but the same optical switch has different wavelength combinations. At least two types of groups are connected so as to be input, and L × P in the P optical switches are connected.
The output ports are connected to the L × P input ports of the L multiplexing elements so that the output ports of the same optical switch are connected to different multiplexing elements without overlapping. Here, the wavelength demultiplexing element can be composed of, for example, an interferometer or a demultiplexing element using a grating. Each of the optical switch and the multiplexing element can be configured by the one described in the first embodiment, for example.

In order to deepen the understanding of the second invention, this is an example in which the wavelength multiplicity N of the optical signal is 8 and the optical signal is demultiplexed into four sets (P = 4) by the combination of wavelengths. And the scale of the optical switch is 4 × 4 (hence M =
FIG. 8 shows an example of connection between the wavelength demultiplexing element and the optical switch when L = 4). Note that, in FIG. 8, rectangular marks indicate individual input ports of the optical switch. Further, a rectangular mark denoted by the same pattern and and the same number (13 _1, etc.) indicates that the input ports that belong to the same optical switch.

In the example shown in FIG. 8, the first optical switch 4
One of the two input ports 13 ₁ receives light of a pair of wavelengths λ ₈ and λ ₇ , and another input port inputs light of a pair of wavelengths λ ₆ and λ ₅ . It is shown that the light of the set of the wavelength λ ₄ and the wavelength λ ₃ is input to another input port, and the light of the set of the wavelength λ ₂ and the wavelength λ ₁ is input to another input port.
That is, an example is shown in which light of two different wavelengths is input to each input port. In the case of the example of FIG. 8 as well, since light of the same wavelength does not compete with one 2 × 2 type optical switch in the optical switch 13, it operates as a completely non-blocking type. In the second mode, the number of optical switches (wavelength routers) used can be P, which is smaller than that in the first mode. If n types of light are input to each input port, the relationship is N = P × n. Also, the optical switch 13
The number of wavelengths handled by one 2 × 2 type optical switch in
It becomes Mn. Further, in the case of this example in which n kinds of wavelength light are input to the input port, the output power is n / N of the input power due to the property of the single mode multiplexing element, but it is described in the prior art (a). ) The loss can be reduced compared to the device with the configuration of () (same in the following modifications).

In the description of the second invention, an example in which light of n kinds of wavelengths is input to each input port of the optical switch (two kinds in the example of FIG. 8) has been described. When the optical signals are demultiplexed into P sets, some or all of the sets may have different numbers of wavelengths (for example, a set may have λ ₁ , λ ₂ and λ ₃ wavelengths). Three wavelengths, another set may be two wavelengths of λ ₄ and λ ₅ , etc. Of course, one set may be a single wavelength).

3. Modification 3-1. In the above description of the first embodiment of the present invention, an example in which M wavelength demultiplexing elements 11 are individually prepared has been described. However, instead of these, M input M × N output wavelength routers having M It is also possible to use a wavelength router that demultiplexes an optical signal having a wavelength multiplicity N input to the input port of 1 into light of each wavelength.
This is because it can be expected to reduce the number of wavelength separation elements, simplify the connection with the optical switch, and downsize the optical switch. Such an M input M × N output wavelength router 2
An example of No. 1 is shown in FIGS. 9 (A) and 9 (B). However, in the case of FIG. 9, an example of three inputs and nine outputs is shown.

The wavelength router 21 includes M input ports 21a, a first planar waveguide 21b, and a waveguide array 21c composed of a plurality of waveguides (typically 2 × N × M) having different lengths. , The second planar waveguide 21d and the M × N output ports 21e, and is designed to satisfy the following equation.

Δθ = M (λ ₀ / 2ndN _W ), where Δθ is the angle between adjacent input ports 21a and adjacent output ports 21e, M is the number of input ports 21a, and λ
₀ is the average value of the wavelengths used (average value of the wavelength-multiplexed wavelengths), n is the refractive index of the planar waveguides 21b and 21d,
d is the pitch at the root of each of the waveguides forming the waveguide array 21c on the side of the planar waveguides 21b and 21d. Also,
The distance Δλ _W between adjacent wavelengths when demultiplexing is Δλ _W = 2
It is given by ndΔθ / m. Here, m is m = 2n _C Δ
It is given by L / λ ₀ . Note that n _C is the waveguide array 23
It is the equivalent refractive index in the waveguide forming c. Also,
ΔL is a difference in optical path length between adjacent waveguides in the waveguide array 23c.

When an optical signal in which light of each wavelength λ _2, λ ₅ , λ ₈ is multiplexed is input to each input port 21a of the wavelength router described with reference to FIG. Are output to three adjacent output ports (see FIG. 9).

3-2. Further, the idea of this modification can be applied to the second invention. That is, instead of providing M wavelength demultiplexing elements 11, each of the M input M × P output wavelength routers and the optical signals of the wavelength multiplicity N input to the M input ports is converted by a combination of wavelengths. A configuration using wavelength routers for demultiplexing into P sets can be adopted. However, in that case, for example, the following allowance is taken. First, FIG.
When a wavelength router based on the design concept described using (B) is used, in which the number of output ports 21e is changed to M × P, the wavelength-multiplexed optical signal input to the input port 21a is used. The wavelength density of 3-1. N / P times as compared with the case of the above configuration. Alternatively, FIG. 9B
In designing the wavelength router described by using, the above Δθ is designed so that the pitch of the input port 21a is N / P times the pitch described in the above section 3-1 and M included in this wavelength router is provided. × N output ports 21e
It is also possible to combine P output ports to form M × P output ports.

[0027]

As is apparent from the above description, according to the optical switch of the first invention of this application, M predetermined wavelength demultiplexing elements, N predetermined optical switches and predetermined multiplexing elements are provided. Since L are provided in a predetermined connection relation, the number of wavelengths handled by the optical switch can be made independent of the wavelength multiplicity (up to M types can be used). Furthermore, non-blocking operation is also secured. In addition, an optical signal of wavelength multiplicity N is converted into P
In the second invention including the wavelength demultiplexing element for demultiplexing into individual sets, in addition to the effect of the first invention, another effect that the number of optical switches can be reduced can be obtained. Further, in both the first invention and the second invention, the loss is lower and the structure is simpler than the conventional one.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the first invention.

FIG. 2 is a diagram showing a configuration example of an optical switch 13.

FIG. 3 is an explanatory diagram of a predetermined 2 × 2 type optical switch.

FIG. 4 is a wavelength demultiplexing device according to the first aspect of the first invention.
It is a connection explanatory view between optical switches.

FIG. 5 is an explanatory diagram (1) of the second aspect of the first invention.

FIG. 6 is an explanatory view (No. 2) of the second embodiment of the first invention.

FIG. 7 is an explanatory diagram of a third mode of the first invention.

FIG. 8 is an explanatory diagram of the second invention.

FIG. 9 is an explanatory diagram of a third mode.

[Explanation of symbols]

10: Optical switch of 1st form 10a: Input port of optical switch 10b: Output port of optical switch 11: Wavelength demultiplexing element 11o: Output port of wavelength demultiplexing element 13: Optical switch (multi-wavelength router) 13i: Optical Switch input port 13o: Optical switch output port 13x: Predetermined 2 × 2 type optical switch 13xa, 13xc: Polarization separation element (PBS) 13xb: Polarization converter 13y: For generating SAW (surface acoustic wave) Electrode 13 ₁ : Input port of first optical switch 13 ₂ : Input port of _second optical switch 13 ₃ : Input port of third optical switch 13 ₄ : Input port of fourth optical switch 13 ₅ : 5th Optical switch input port 13 ₆ : Input port of _sixth optical switch 15: Multiplexer element 15i: Multiplexer input port 21: M input M × N output wavelength router

Claims (6)

[Claims] 1. An M-input L-output optical switch, which is provided with M wavelength demultiplexing elements for demultiplexing an optical signal of wavelength multiplicity N into light of individual wavelengths, simultaneously It comprises N independently switchable optical switches, L N input and 1 output multiplexing elements, and M × N output ports of said M wavelength demultiplexing elements, said N optical switches. At least 2 for the same optical switch without duplication for M × N input ports in
Lights of different wavelengths are connected so that N × L output ports of the N optical switches are overlapped with N × L input ports of the L multiplexing elements. Are connected so that the output ports of the same optical switch are connected to different multiplexing elements (where M and L are integers of 2 or more and M = Including the case of L). 2. An optical switch having M input and L output, comprising a plurality of wavelength demultiplexing elements for demultiplexing an optical signal having a wavelength multiplicity N into P sets of combinations of wavelengths, and a plurality of lights having different wavelengths. P optical switches capable of switching simultaneously and independently, L comprising P input and 1 output multiplexing elements, and M × P output ports of the M wavelength demultiplexing elements being the P The M × P input ports of the optical switch are connected so that at least two sets having different wavelength combinations are input to the same optical switch without duplication, and the P The L × P output ports of the optical switch are connected to the L × P input ports of the L multiplexing devices so that the output ports of the same optical switch are connected to different multiplexing devices without overlapping. Characterized by Optical switch of M × L scale (where M and L are integers of 2 or more and M = L is included. P is an integer that satisfies 2 ≦ P <N. Each set may have the same number of wavelengths, or some sets or all sets may have different numbers of wavelengths.) 3. The optical switch according to claim 1, wherein the optical switch is a 2 × 2 type optical switch capable of simultaneously and independently switching a plurality of lights having different wavelengths and having a scale of M input and L output. An optical switch characterized by comprising wavelength routers connected in multiple stages. 4. The optical switch according to claim 1, wherein, in connecting the wavelength demultiplexing element and the optical switch, different wavelength demultiplexing elements output to M input ports of the same optical switch. An optical switch characterized by being arranged so that ports are connected. 5. The optical switch according to claim 1, wherein instead of the M wavelength demultiplexing elements, there are M input M × N output wavelength routers, and the number of wavelengths input to the M input ports is increased. An optical switch comprising a wavelength router for demultiplexing an optical signal of severity N into light of individual wavelengths. 6. The optical switch according to claim 2, wherein instead of the M wavelength demultiplexing elements, there is a wavelength router having M inputs and M × P outputs, and the number of wavelengths input to the M input ports is increased. An optical switch equipped with a wavelength router for demultiplexing each of the severe N optical signals into P sets by combining wavelengths.