MXPA99006253A - Switchable wavelength router - Google Patents

Abstract

A switchable wavelength router (999) having an input port (11) for the incoming WDM signal (500) and two output ports (13, 14) for de-multiplexing the WDM signals (500). The router (999) divides the received optical signals into divided optical signals (101, 102) comprising a subset of the channels and spatially positions the divided optical signals in response to a control signal applied to the router (999). For example, the router (999) can divide a received WDM signal (500) into two subsets that are either single channel or WDM signals. Multiple routers (999) can be cascaded to form a 2n switchable wavelength router, where n is the number of stages of wavelength routers.

Description

WAVE LENGTH, SWITCHING DEVICE BACKGROUND OF THE INVENTION 1. Field of Invention The present invention relates, in general, to communication systems, and more particularly, to a wavelength routing device, switchable for optical communications by wavelength division multiplexing (WDM). . 2. Establishment of the Problem. Multiplexing by wavelength division, optics has gradually become the main network, normal for fiber optic communication systems. WDM systems employ signals consisting of a number of optical signals of different wavelengths, known as signals or carrier channels, to transmit information about optical fibers. Each carrier signal is modulated by one or more. information signs. As a result, a significant number of signals can be transmitted REF: 030677 information on an optical fiber, individual using WDM technology. Despite the use of a substantially higher fiber bandwidth provided by WDM technology, a number of serious problems must be overcome, for example, multiplexing, demultiplexing, and optical signal routing, if these systems have that become commercially viable. The addition of the wavelength domain increases the complexity for managing a network because the processing now involves both filtering and routing. Multiplexing involves the process of combining multiple channels (each defined by its own frequency spectrum) into an individual WDM signal. Demultiplexing is the opposite process in which an individual WDM signal is broken down into individual channels. The individual channels are spatially separated and coupled to the specific exit doors. The routing differs from demultiplexing in that a routing device especially separates the optical input channels in the output ports and switches those channels according to the control signals for a desired coupling between an input channel and an output port. . The North American patent applications, co-pending from the applicants Nos. of Series 08 / 685,150 and 08 / 739,424 (Kuang-Yi Wu et al.) teach two independent methods for the routing of high-performance signals (No. Se Series 08 / 685,150) and wavelength demultiplexing (No. Se Series) 08 / 739,424). In the Serial No. 08 / 685,150, new structures are described for making optical switches (routing devices) that perform a very high extinction ratio operation. However, these switches are independent of the wavelength. In Serial No. 08 / 739,424, a system for providing the demultiplexing and wavelength routing functions is described. However, this individual stage design depends primarily on the design of the filter. The transmission function of the filter must be limited to a flat, square part, ideal for performing the desired low crosstalk operation. In this patent application, the two architectures and concepts presented in the patent applications cited above are combined to create a switchable wavelength routing device. This new structure employs double stage filters that can obtain a better bandpass (purified) transmission, and incorporates a fault tolerant structure (similar to that described in Serial No. 08 / 685,150) that results a low crosstalk between the channels.

BRIEF DESCRIPTION OF THE INVENTION The present invention involves a switchable wavelength routing device having an input port for the incoming WDM signal and two output ports for demultiplexing the WDM signals. The routing device divides the optical signals, received in the optical, divided signals comprising a subset of the channels and spatially positions the optical signals, divided in response to a control signal applied to the routing device. For example, the routing device can divide a received WDM signal into two subsets that are either single channel or WDM signals. The multiple routing devices can be cascaded to form a switchable wavelength routing device 2n, where n is the number of stages of the wavelength routing devices. More specifically, a first birefringent element decomposes the WDM optical signal into two spatially separated beams having orthogonal polarizations. A first polarization rotator selectively rotates the polarization of one of the beams to equalize the polarization of the other has, based on an external control signal. A wavelength filter (e.g., stacked wave plates) provides an optical transmission function dependent on polarization such that the first beam is decomposed in the third and fourth orthogonal beams, and the "second beam is decomposed in the fifth and sixth orthogonal beams The third and fourth beams carry a first spectral band in a first polarization and the fourth and sixth beams carry a second spectral band in an orthogonal polarization A second birefringent element spatially separates those four beams into four horizontally polarized components and vertically polarized A second polarization rotator rotates the polarizations of the beams so that the third and fifth beams are orthogonally polarized and the fourth and sixth beams are orthogonally polarized A third birefringent element recombines the third and fifth beams containing the first band spectral that is coupled to the first exit door, and also r ecombine the fourth and sixth beams containing the second spectral band that is coupled to the second exit door.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURES la and lb are block diagrams illustrating the functionality of the optical routing device according to the present invention. FIGURES 2a and 2b are schematic, simplified diagrams illustrating a switchable, dual-stage wavelength routing device according to the present invention. FIGURES 3a and 3b are simplified schematic diagrams illustrating a switchable, single-stage wavelength routing device according to the present invention. FIGURES 4a and 4b are graphs showing experimental results using three lithium niobate wave plates in the filter design. In Figure 4a, the spectra of exit door # 1 are recorded before and after switching. Figure 4b shows the corresponding spectra of exit door # 2 before and after switching. The spectra are approximately equally spaced and are easy for spectral, additional cutting. FIGURE 5 is a graph showing a design of the asymmetric spectra where the narrowest can be used as an add / drop gate, while the wider spectrum can pass the rest of the WDM signals back to the network. FIGURE 6 is a graph showing a pattern of a wavelength routing device, switchable to cover the wavelengths of 1310 and 1550 nm. With this design, crosstalk is obtained better than -50 dB between both channels.

DETAILED DESCRIPTION OF THE INVENTION 1. General view The present invention both demultiplexes (i.e., spectrally separates) and routes (i.e., spatially permutes) an optical signal multiplexed by wavelength division (WDM). FIGURES la and lb are block diagrams illustrating the general functionality of the present invention. A WDM 500 signal consists of multiple channels, with each channel having its own range of wavelengths or frequencies. As used herein, the terms "channel" or "spectral band" refer to a particular range of frequencies or wavelengths that define a unique information signal. Each channel is usually spaced with equal adjacent channels, although this is not necessary. The unequal spacing may result in some complexity in the design, but, as will be noted, the present invention can be adapted to such a channel system. This flexibility is important in that the placement of the channel is greatly moved by the technical capabilities of the transmitters (ie, laser diodes) and detectors and thus the flexibility is of significant importance. The WDM 500 signal is input using optical signal coupling techniques, conventional to the input port of the wavelength routing device, switchable 999. When switching the control signal between two control states (e.g., on and off ), the routing device 999 generates two unique output signals at its output ports, where the input WDM spectrum is divided into two bands 501 and 502. One is designated as the first band 501 (i.e., the wavelength shorter in FIGURE la) and the other is designated as the second band 502 (that is, the largest wavelength in FIGURE la). The two spectral bands are routed to the exit doors according to the control state, as shown in FIGURES la and lb. The two output spectra can be symmetric or asymmetric depending on the functionality required by the WDM system. For the demultiplexing of the optical channel, the symmetrical spectra at the two output ports are usually preferred. In addition, a second-stage wavelength routing device with a narrower spectral response can be cascaded after the outputs of the first stage to further divide the spectra and to produce even narrower spectral bandwidths. In an asymmetric spectral design, the wavelength routing device can be used as an add / drop filter for a WDM network node. In the present, a specific optical channel can be added or lowered through the narrowest band of the asymmetric spectra of the wavelength routing device, while the rest of the channels continue past the length routing device. wave across the complementary spectrum, wider. This allows WDM signals to enter or leave the network as they travel within the WDM network. 2. Dual Stage Routing Device FIGURE 2a and FIGURE 2b are schematic diagrams illustrating the two states of 'control of a dual stage 999 wavelength routing device. The 999 wavelength routing device is under control binary of a control bit and therefore has two control states. The routing device 999 serves to separate the channels of the wavelength spectrum applied to an input port 11 and determines which of the two output ports 13, 14 is coupled to each of the channels. In FIGURE 2a and FIGURE 2b, the solid, highlighted or bold lines indicate optical paths that contain the full spectrum of channels in the incoming WDM signal 500. Thin, solid lines indicate optical paths of signals containing a first subset of channels marked as the first spectral band. The thin, dotted lines indicate the optical channels carrying a second subset of channels referred to as the second spectral band. It is important to understand that each of the subsets can comprise more than one channel and can itself be a WDM signal although having a smaller bandwidth than the original WDM signal 500. Each of the optical paths is additionally marked with be a horizontal double-headed line that indicates horizontal polarization, or a double-headed vertical line that indicates vertical polarization, or double-headed horizontal and vertical lines that indicate horizontal and vertical polarizations, mixed in the optical signal in that point. The WDM 500 signal enters the first birefringent element 30 which spatially separates the horizontally and vertically polarized components of the WDM 500 signal. The first birefringent element 30 consists of a material that allows the vertically polarized portion of the optical signal to pass through without changing the course because these are ordinary waves in the birefringent element 30. In contrast, the horizontally polymerized waves are redirected at an angle due to the effect of birefringent abandonment. The redirection angle is a well-known function of the particular materials selected. Examples of materials suitable for the construction of the birefringent element include calcite, rutile, lithium niobate, YV04 based on crystals, and the like. The horizontally polarized component travels along a path 101 as an extraordinary signal in the first birefringent element 30 while the vertically polarized component 102 travels as an ordinary signal and passes through without spatial reorientation. The resulting signals 101 and 102 both carry the full frequency spectrum of the WDM 500 signal. The both horizontally and vertically polarized components 101 and 102 are coupled to a switchable bias rotator 40 under the control of a control bit. The polarization rotator 40 consists of two subelement rotators forming a complementary state, that is, when one is activated the other is deactivated. The rotator 40 selectively rotates the polarization state of any signal 101 and 102 by a predefined amount. In the preferred embodiment, the rotator 40 rotates the signals by either 0o (ie, without rotation) or 90 °. For example, the polarization rotator 40 can be a liquid, pneumatic, twisted crystal rotator, a liquid crystal rotator, ferroelectric, a liquid crystal rotator, based on pi cells, a Faraday rotator based on a magneto-rotator. optical, a polarization rotator based on an acousto-optic or electro-optic. Commercially available rotators based on liquid crystal technology are preferred, although other rotator technologies can be applied to meet the needs of a particular application. The switching speed of these elements varies from a few milliseconds to nanoseconds, and therefore can be applied to a wide variety of systems to meet the needs of a particular application. These and other similar, basic elements are considered equivalent and may be substituted and exchanged without departing from the spirit of the present invention. FIGURE 2a illustrates the control state in which the signal 102 is rotated 90 ° so that both signals 103, 104 exiting the rotator 40 have a horizontal polarization. FIGURE 2b illustrates the second control state in which the polarization of the signal 101 is rotated by 90 ° so that both optical signals 103, 104 exiting the rotator 40 have a vertical polarization. Again, in this step, the both horizontal and vertical components contain the full frequency spectrum of the channels in the WDM 500 signal. The element of the stacked wave plates 61 is a stacked plurality of birefringent wave plates in selected orientations that generate two characteristic states. The first characteristic state carries a first sub-spectrum with the same polarization as the input, and the second characteristic state carries a complementary sub-spectrum in the orthogonal polarization. The polarization of the input beam and the two output polarizations form a pair of spectral responses, where (H, H) and (V, V) carry the first part of the spectrum of enrrada and (H, V) and (V, H) ) carry the complementary (second) part of the input spectrum, where V and H are the vertical and horizontal polarization, respectively. This can be better understood by comparing FIGURES 2a and 2b. With the horizontal polarizations 103, 104 entering the stacked wave plate element 61 as shown in FIGURE 2a, orthogonal vertical and horizontal polarizations are generated with the first spectral band that resides in the horizontal polarization and the second spectral band that resides in vertical polarization. With the vertical polarizations 103, 104 entering the stacked wave plate element 61 as shown in FIGURE 2b, orthogonal vertical and horizontal polarizations are generated with the first spectral band residing in the vertical polarization and the second spectral band that resides in horizontal polarization. For wavelength demultiplexing applications, the stacked wave plate element 61 has a comb characteristic filter response curve with a wave spectral response with the substantially flat or square top. For WDM optical channel addition / descent applications, the stacked wave plate element 61 has an asymmetric filter response. Returning to FIGURE 2a, the pairs of optical responses 105, 106 exiting the stacked wave plate element 61 are coupled to a second birefringent element 50. This birefringent element 50 has a construction similar to the first birefringent element 30 and spatially separates the horizontally and vertically polarized components of the input optical signals 105 and 106. As shown in FIGURE 2a, the optical signals 105, 106 are broken into the vertically polarized components 107, 108 that contain the second, spectral band and components horizontally polarized 109, 110 containing the first spectral band. Due to the birefringent abandonment effect, the two orthogonal polarizations carrying the first spectral band 109, 110 in horizontal polarization and the second spectral-adjusted band 107, 108 in vertical polarization are separated by the second birefringent element 50. After the second birefringent element 50, the optical elements on the input side of the second birefringent element 50 can be repeated in the opposite order, as illustrated in FIGS. 2a and 2b. The second element of stacked wave plates 62 has substantially the same composition as the first element of stacked wave plates 61. The horizontally polarized beams 109110, which enter the second element of stacked wave plates 62, are further purified and maintain their polarization when they exit from the second element of stacked wave plates 62. On the other hand, the vertically polarized beams 107, 108 undergo a rotation of 90 ° polarization and also purify when they leave the second element of stacked wave plates 62. The polarization rotation of 90 ° is due to the fact that the vertically polarized beams 107, 108 carry the second spectral band and therefore are in the complementary state of the element 62. At the output of the stacked wave plate element 62, all four beams 111, 112, and 113, 114 have horizontal polarization. However, the spectral bands defined by the filter characteristics of the stacked wave plate elements 61, 62 are separated with the second spectral band 501 at the top and the first spectral band 502 down. To recombine the spectra of the two sets of beams 111, 112 and 113, 114, a second polarization rotator 41 and a second birefringent element 70 are used. Again, the second rotator 41 has two sub-elements that intercept the four parallel beams 111-114. The two sub-elements of the second rotator 41 are adjusted in a state complementary to the first rotator 40, that is, when the first rotator 40 is activated / deactivated, the second rotator 41 is activated / deactivated. In the case of Figure 2a, beam polarization 111 and 113 is rotated through 90 °, and beams 112 and 114 are passed without polarization change. This results in an orthogonal polarization pair 115, 116 and 117, 118 for each spectral band at the output of the second rotator 41. Finally, a second birefringent element 70 recombines the two orthogonal polarizations 115, 116 and 117, 118 using the effect of abandonment to produce two spectra that exits at gates 14 and 13, respectively. This completes the first operational state of the wavelength routing device, switchable 999. FIGURE 2b shows the other control state in which the two polarization rotators 40 and 41 have been switched to their complementary states, ie activated to deactivated, or deactivated to activated, in contrast to its states shown in FIGURE 2a. The entire spectrum 500 is first divided by polarization into two orthogonal states, i.e. the vertical and horizontal polarization as indicated at 101 and 102, by the first birefringent element 30. The first polarization rotator 40 is now adjusted to have the polarizations of exit 103 and 104 both vertical. After passing through the first stacked wave plate element 61, two orthogonal (i.e., horizontal and vertical) polarizations are generated which carry the second and the first spectral bands, respectively. In this operating state, horizontal polarization is used to carry the second spectral band, and vertical polarization is used to carry the first spectral band of the WDM sector 500. The two spectral bands are then spatially separated by the second birefringent element. with vertical polarization 107, 108 going upwards and horizontal polarization 109, 110 passing through without deviation. Therefore, this separates the two spectral bands according to their polarizations. The resulting four beams 107-11-0 enter the second stacked wave plate element 62 for additional spectral purification. Another important role of the element 62 is its polarization rotation for the second spectral band. Remember that the elements of stacked wave plates 61, 62 have two characteristic states. With respect to the first band, the vertically polarized beams 107, 108 remain unchanged by the element 62. However, with respect to the second spectral band, the horizontally polarized beams 109 and 110 are rotated by 90 ° as they pass. through the element 62 because they are in the complementary state of the stacked wave plate 62. At the output of the element 62, all polarizations become vertical, as indicated by beams 111, 112 for the first spectral band and beams 113, 114 for the second spectral band in FIGURE 2b. To recombine the two sub-spectra, a second polarization rotator 41 and third birefringent element 70 are used, as previously discussed. In the case of FIGURE 2b, the second rotator 41 is adjusted to rotate the polarizations of the beams 112 and 114 by 90 ° and to pass the beams 111 and 112 without rotation. The resulting beams 115-118 are recombined by the third birefringent element 70 and exit at ports 14 and 13 for the first and second spectral bands, respectively. 3. Single stage routing device A simplified version of the dual-stage wavelength routing device using a single-stage switchable, wavelength routing device is shown in FIGURES 3a and 3b, for the two operating states. Two changes have been made with this structure in contrast to the double stage design shown in FIGURES 2a and 2b. The second element of stacked wave plates 61 in FIGURES 2a and 2b have been removed and the second polarization rotator 41 has been replaced with a passive bias rotator with two sub-elements to intercept beams 108 and 109, as shown in FIGURES 3a and 3b. The single-stage wavelength routing device operates in substantially the same manner as the dual-stage routing device until the bundles 107-110 leave the second birefringent element 50. At the outlet of the second birefringent element 50, the first and second divided spectral bands are carried by two sets of orthogonally polarized beams 107, 108 and 109, 110, respectively. The positions of the first and second spectral bands depend on the polarization state of the beams 103 and 104. If the first spectral band is horizontally biased by the first rotator 40, it will exit in the lower exit door 13 and the second spectral band will exit in the upper exit door 14. If the first, spectral band is vertically polarized by the first rotator 40, it will exit in the upper exit door 14 and the second spectral band will exit in the lower exit door 13. Because the birefringent abandon effect in the second birefringent element 50, the vertically polarized light beams 107, 108 deviate from their original trajectories and travel upwards, while the horizontally polarized beams 109, 110 pass through the element 50 without changing their addresses. The two pairs of beams 107, 108 and 109, 110 emerging from the second birefringent element 50 have the same polarization but different frequencies. The passive polarization rotator 41 is designed to rotate the polarization only in the areas that intercept the beams 108 and 109. Therefore, at the output of the rotator 41, the orthogonally polarized beam pairs 115, 116 and 117, 118 are produced for both the first and the second spectral bands. Those beams 115-118 are then recombined by the third birefringent element 70 and exit to gates 13 and 14. The individual stage switchable, wavelength routing device has the advantages of requiring a few components as compared to the device. of 'double stage routing. However, its spectral purity is not as good as the dual-stage routing device. It will depend on the applications and requirements of a specific WDM network, whether the single-stage wavelength routing device or the dual-stage wavelength routing device is preferred. An advantage of the present invention is that the routing is performed while substantially conserving all the available optical energy in the WDM 500 signal. That is, with respect to the polarization of the signals in the WDM 500 signal both horizontal and horizontal components are used. vertically polarized and combined at the exit doors 13, 14 which results in very lossy through the device < Routing 999. Each set of birefringent wave plates 61, 62 is oriented at an optical axis angle, unique with respect to the optical axis of the polarization rotator 40. As mentioned above, the spectral design for the wave plate elements stacked 61 and 62 is dependent on the applications required by the WDM network. Next, three different designs are listed that can be used with current WDM systems. The first example uses wave plates stacked with equally separated sub-spectra, centered on wavelengths of 1533 and 1557 nm. In the second case, the asymmetric sub-spectra are produced by the stacked wave plates. This design can be used for an application of the add / download optical filter. The third is a design to cover the two transmission windows of optical networks with fibers at wavelengths of 1310 and 1550 nm. In this case, the central wavelengths of 1310 and 1550 nm can be rotated interchangeably to any output port.

EXAMPLE 1 Three lithium niobate wave plates (LiNb03) having a thickness of 1 mm have been stacked together to form an equally divided, flat top spectrum as shown in Figure 4, with a crosstalk down channel of 30 dB. The experimental results are based on the switchable, dual-stage wavelength routing device. This improves existing filter technologies, such as using multi-layer dielectric coatings, where a 20 dB crosstalk is generally obtained. Due to the design of equal spectra in the two output ports, this type of switchable wavelength routing device can be cascaded further. With "n" stages of the routing devices arranged in cascade, a total of 2n output ports results. These 2n doors can have their output spectrum permuted according to the n control signals to create a programmable wavelength routing device.

Example 2 Figure 5 shows an asymmetric spectrum design, where an exit door has a much narrower spectral width compared to the other door. This design can be applied to a WDM network when there is a need to add or lower part of the optical channels in an optical exchange node. The addition / descent filter can be either passive or active, depending on the design and system requirements. The switching element, ie the switchable polarization rotator arrangements, can be replaced by two half-wave passive plates at each corresponding position of the polarization rotator, such that one of the doors is always designated as the gate. of addition / download. The rest of the optical channels pass through the wavelength routing device and continue to propagate along the WDM network.

Example 3 As shown in Figure 6, the present invention can be further extended to the furthest spectra to cover two operational wavelength windows, centered at 1310 and 1550 nm for fiber optic switching. Various techniques (e.g., fiber fusion and multi-layer coating techniques) have been widely used in industry to accomplish this task. However, the current design provides lower crosstalk and a switchable feature, which are valuable from a system point of view. The foregoing description sets forth a number of embodiments of the present invention. Other arrangements or modalities could be practiced, not exposed in a precise manner, under the teachings of the present invention and as set forth in the following claims.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, the content of the following claims is claimed as property.

Claims (19)

1. A method for switching optical signals multiplexed by wavelength division (WDM), characterized in that it comprises the steps of: providing a first input / output gate (1/0) for receiving the optical signal WDM; provide a second 1/0 door; provide a third door of 1/0; spatially decomposing the optical signal WDM received from the first I / O gate in a first and a second beam having orthogonal polarizations with respect to each other; rotating the polarization of the first beam to substantially equalize the polarization of the second beam; demultiplexing the first and second beams of the same polarization through a first wavelength filter having an optical transmission function, dependent on polarization such that the first beam is decomposed in the third and fourth beams with their polarizations orthogonal to each other, and- the second beam is decomposed into the fifth and sixth beams with their orthogonal polarizations to each other, where the third and fifth beams carry a first spectral band, predetermined in a first polarization and the fourth and sixth beams carry a second spectral band, predetermined in a second polarization, wherein the first and second spectral bands are substantially complementary and the first and second polarizations are orthogonal; rotate spatially the third, fourth, fifth and sixth beams based on their polarizations; passing the third, fourth, fifth and sixth beams routed through a second wavelength filter that has substantially the same transmission function as the first wavelength filter, wherein the second wavelength filter rotates to the third, fourth, fifth and sixth beams back to the same polarization state as the second beam before it enters the first wavelength filter; turn the polarizations of the fifth and the sixth beams such that they are orthogonal to the third and fourth beams; spatially recombining the third and fifth beams containing the first spectral band, and spatially recombining the fourth and sixth beams containing the second spectral band; and coupling the first spectral band to the second I / O gate and the second spectral band to the third I / O gate.

2. The method according to claim 1, characterized in that the step of spatially decomposing the optical signal WDM uses a first birefringent element.

3. The method according to claim 1, characterized in that the step of rotating the third, fourth, fifth and sixth beams uses a second birefringent element.

4. The method according to claim 1, characterized in that the step of recombining the third, fourth, fifth and sixth beams uses a third birefringent element.

5. The method according to claim 1, characterized in that the step of rotating the first beam also comprises passing the first and the. second you do through a configurable rotator arrangement that has: (a) a first area to rotate the polarization of the first beam; and (b) a second area to pass the second beam ..

6. The method according to claim 1, characterized in that the step of rotating the polarization of the fifth and sixth beams comprises passing the third, fourth, fifth and sixth beams through a rotator array, configurable having: ( a) a first area to rotate the polarization of the fifth and the sixth beams; and (b) a second area to pass the bercer and the fourth beam.

7. The method according to claim 1, characterized in that the first wavelength filter comprises a stacked plurality of birefringent wave plates with each wave plate oriented in a predetermined direction.

8. The method according to claim 1, characterized in that the second wavelength filter comprises a stacked plurality of birefringent wave plates with each wave plate oriented in a predetermined direction.

9. A method for switching optical multiplexed signals by wavelength division (WDM), characterized in that it comprises the steps of: providing a first input / output (I / O) gate for receiving the optical signal WDM; provide a second I / O gate; provide a third door of 1/0; spatially decomposing the optical signal WDM received from the first I / O gate in the first and second beams having orthogonal polarizations with respect to each other; rotate the polarization of the first beam to substantially equalize the polarization of the second beam; demultiplexing the first and the second beams of the same polarization through a wavelength filter having a polarization dependent on the optical transmission function such that the first beam is decomposed into the third and fourth beams with their orthogonal polarizations between yes, and the second beam breaks down into the fifth and sixth beams with their orthogonal polarizations to each other, where the third and fifth beams carry a first predetermined spectral band in a first polarization and the fourth and sixth beams carry a second spectral band, predetermined in a second polarization, wherein the first and second spectral bands are substantially complementary and the first and second polarizations are orthogonal; rotate spatially the third, fourth, fifth and sixth beams based on their polarizations; rotate the polarizations of the third, fourth, fifth and sixth beams such that the third and fifth beams are orthogonally polarized and the fourth and sixth beams are orthogonally polarized; recombine spatially the third and fifth beams containing the first spectral band and spatially recombine the fourth and sixth beams containing the second spectral band; and coupling the first spectral band to the second 1/0 gate and the second spectral band to the third I / O gate.

10. The method according to claim 9, characterized in that the step of spatially decomposing the optical signal WDM uses a first birefringent element.

11. The method according to claim 9, characterized in that the routing step of the third, fourth, fifth and sixth beams uses a second birefringent element.

12. The method according to claim 9, characterized in that the step of recombining the third, fourth, fifth and sixth beams uses a third birefringent element.

13. The method according to claim 9, characterized in that the wavelength filter comprises a stacked plurality of birefringent wave plates with each wave plate oriented in a predetermined direction.

14. The method according to claim 9, characterized in that the step of rotating the first beam further comprises passing the first and second beams through a configurable rotator arrangement having: (a) a first area to rotate the polarization of the first beam; and (b) a second area to pass the second beam.

15. The method according to claim 9, characterized in that the step of rotating the polarization of the fifth and sixth beams comprises passing the third, fourth, fifth and sixth beams through a rotator array, configurable having: ( a) a first area to rotate the polarization of the fifth beam; (b) a second area for rotating the polarization of the sixth beam; (c) a third area to pass the third beam without rotation; and (b) a fourth area to pass the fourth beam without rotation.

16. A switchable wavelength routing device, characterized in that it comprises: a first birefringent element for receiving an optical signal WDM and decomposing the optical signal WDM in a first beam and a second beam having orthogonal polarizations and being spatially separated; a first polarization rotator having a first control state in which the polarization of the first beam is rotated to substantially equalize the polarization of the second beam, and a second control state in which the polarization of the second beam is rotated to substantially equalize the polarization of the first beam; the control state of the first polarization rotator which is switchable by an external control signal; a wavelength filter coupled to receive the first and second beams of the first polarization rotator, the wavelength filter having an optical transmission function dependent on polarization such that the first beam is decomposed in the third and the fourth beams with their orthogonal polarizations among themselves, and the second beam is decomposed into the fifth and sixth beams with their orthogonal polarizations to each other, where the third and fifth beams carry a first spectral band, predetermined in a first polarization and the fourth and sixth beams carry a second spectral band, predetermined in a second polarization, wherein the first and second spectral bands are substantially complementary and the first and second polarizations are orthogonal; a second boiling element to spatially separate the third, fourth, fifth and sixth beams into four horizontally polarized and vertically polarized components; a second polarization rotator to rotate the polarizations of the third, fourth, fifth and sixth beams such that the third and fifth beams are orthogonally polarized and the fourth and sixth beams are orthogonally polarized; and a third birefringent element to receive the third, fourth, fifth and sixth beams of the second polarization rotator, to spatially recombine the third and fifth beams containing the first spectral band, and to spatially recombine the fourth and sixth beams that they contain the second spectral band.

17. The routing device according to claim 16, characterized in that the first polarization rotator further comprises: a first area for rotating the polarization of the first beam in the first control state, and passing the first beam without rotation in the second state of control; and a second area for passing the second beam without rotation in the first control state, and rotating the polarization of the second beam in the second control state.

18. The routing device according to claim 16, characterized in that the second polarization rotator further comprises: (a) a first area for rotating the polarization of the fifth beam; (b) a second area for rotating the polarization of the sixth beam; (c) a third area to pass the third beam without rotation; and (b) a fourth area to pass the fourth beam without rotation.

19. The routing device according to claim 16, characterized in that the wavelength filter comprises a stacked plurality of birefringent wave plates with each wave plate oriented in a predetermined direction.