WO2013141760A2

WO2013141760A2 - Method for switching nxn optical channels and multi-channel switch

Info

Publication number: WO2013141760A2
Application number: PCT/RU2013/000221
Authority: WO
Inventors: Игорь Николаевич КОМПАНЕЦ; Сергей Игоревич КОМПАНЕЦ; Татьяна Александровна НЕЕВИНА
Original assignee: Kompanets Igor Nikolaevich; Kompanets Sergey Igorevich; Neevina Tatyana Aleksandrovna
Priority date: 2012-03-20
Filing date: 2013-03-19
Publication date: 2013-09-26
Also published as: WO2013141760A3; RU2012110328A; RU2504812C2

Abstract

The invention relates to the information-processing and communications field and can be used for transmitting, receiving and redistributing information signals in switching and coding/decoding devices of telecommunications systems and of fibre-optic and integrated optical communications, information-processing and data computation systems, including on supercomputers. The essence of the invention consists in that, in a multi-channel switch which optically connects any specified optical input channel to any specified optical output channel, a method for switching NN channels is proposed, which method is characterized in that, in each bit, the connections are implemented in parallel, wherein the integration of the channels is controlled optically owing to the photorefractive properties of the material of the optical channels. In order to implement the method, a multi-channel switch is proposed in which signals are transferred from channel to channel by supplying photorefractive waveguides with optical signals of a specified configuration, which can be generated with the aid of a matrix of light emitters and a holographic optical element or an optical mask, which are optically connected with the aid of projection optics.

Description

The method of switching NxN optical channels

and multi-channel switch

Technical field

The invention relates to the field of information processing and communication and can be used to transmit, receive and redistribute information signals in switching devices of multi-subscriber telecommunication and fiber-optic communication systems and integrated optics systems, information processing and data calculation, including in supercomputers. State of the art

Known acousto-optic (AO) fiber switch ΙχΝ light channels, based on the effect of the Bragg AO diffraction [1]. The light from the input fiber is fed to the collimating system of the switch and then to the AO crystal. A control radio signal at a frequency is supplied to a piezoelectric transducer, which excites an ultrasonic wave in a crystal with the same frequency. Diffracting on this wave, the light is deflected by an angle α = ί / υ, proportional to the frequency of the radio signal (here λ is the wavelength of light and υ is the speed of sound in the crystal). The deflected beam is focused by the lens into the fibers of the output optical fibers. To organize the NxN switch, it would be necessary to either place N piezoelectric transducers on a single crystal, which would lead to unacceptably large cross-noise and reduce the contrast of the switched signals, or have N crystals (with its piezoelectric transducers), which would lead to a significant complication and cost of the switch.

Known optical switch 1x2, including an optical waveguide formed of two light-transmitting materials, located one after another and having a common border, moreover, the refractive index of one of the materials can be changed by external action, for example, by application of electric voltage in the case of electro-optical material [2]. Light falls on the interface between two materials at such an angle that by changing the refractive index of the first material, it is possible to ensure that the light either passes through the boundary or is reflected from it due to the known effect of total internal reflection (TIR) [3]. To create a ΙχΝ switch, it is necessary to use a certain sequence of such materials - electro-optical crystals, so that, electrically controlling the value of the refractive index, direct the light flux along certain directions on the way to a given address (output).

A device is known for filtering light and controlling the direction of the flow with ΙχΝ channels [4], based on the application of the effect of total internal reflection (TIR) and the transverse electro-optical effect in an optical crystal. The device includes a number of independent electrodes located above the electro-optical crystals in order to divide the layer of electro-optical material into a set of so-called pixels. A control electric circuit is connected to the device in order to change the voltage at the electrodes and thereby control the direction of propagation of the light flux. Such a device can be used as an optical scanner to shift the position of the incident beam from one pixel to another. The device can also be used as a multi-channel color filter, if a filter is inserted in each output pixel that transmits a certain light, associated with that particular pixel, and reflects light of other wavelengths.

Creating an NxN switch based only on approaches [2, 4] would require a huge number of separate switches and multiple optical channel crossings, which would make the switch too complicated and expensive.

Closest to the proposed method and device is a switching method implemented in a KxM fiber optic switch of optical channels with a relatively low attenuation in the channels and a low level of crosstalk [5]. The device contains a plate of an electro-optical lithium niobate crystal (LiNbO ₃ ) in which waveguide channels with control electrodes are made. Each plate is divided into M cells, in each cell, K waveguide channels are made, i.e. all performed KXM channels. From each of the K inputs, there are M optical cables, one for each cell. To each of the M outputs, on the contrary, from the corresponding cell all K optical cables are connected: from the first cell to the first output, from the second cell to the second, etc. By applying a control voltage to the electrodes that control the inclusion of the electro-optical effect in the corresponding waveguide channel from lithium niobate, due to the air defense effect, a predetermined connection of any optical input to any optical output is provided. For example, if a signal with the address m is supplied to the input in order, then the next waveguide channel (in accordance with the serial number of the input) in the needle cell is turned on (voltage is applied to it and it becomes transparent) (in accordance with the serial number of the output). Thus, by simultaneously switching on one specific waveguide channel in each cell, all incoming signals can be switched in parallel.

The disadvantage of this method of connecting channels in the switch is the large number of intersections of fiber optic cables (as well as electrical wires for connecting control electrodes) resulting from the serial connection of the first of K inputs with all M outputs, then the second input with all M outputs, then the third, fourth, etc., up to the connection of the K-th input with all M outputs.

Thus, the multichannel fiber optic switch according to the patent [5] provides switching K input channels on the M output with a relatively low attenuation in the channels and a low level of crosstalk. However, the device contains a large number of intersecting fiber-optic and electric cables, making it difficult for its design and technological implementation.

The problem to be solved in the proposed method for switching NxN optical channels and a device for its implementation is to make the connections of the input and output optical channels in automatic mode without intersections of fiber-optic and electrical cables and with maximum parallelism, which simplifies the design embodiment of the switch, with the possibility of its block design with the same blocks for this address category.

Brief Description of the Drawings

The drawings show:

Figure 1 - Diagram of switching NxN optical channels according to the proposed method.

FIG. 2 - A diagram explaining the operation of the proposed multi-channel switch.

FIG. 3 - An example of the implementation of the operation of doubling information channels using optical cubes.

FIG. 4 - Scheme of the implementation of the operation of the "assembly" of channels using photorefractive waveguides (PV) in the initial (left), intermediate (middle) and final (right) state.

FIG. 5 - General diagram of the proposed switch (for example, 8 channel device) located:

a) in the initial state, when the input and output channels are not connected,

b) in an intermediate state, when addressing and assembling channels, and

c) in the final state, when the information optical flow is directed to the given addresses.

6 - Switching in an electric circuit.

SUMMARY OF THE INVENTION

The solution to this problem is provided by the fact that the method of switching NxN optical channels is based on the use of the photorefraction effect, and for the implementation of a given connection of any optical input with a given optical output without intersecting fiber-optic and electric cables and with maximum parallelism: - organize a bitwise serial-parallel connection of N input optical channels with N output optical channels, and all channel connections are performed sequentially for each bit of n = log2N bits, starting from the senior, in n steps, and at the same time in parallel within each bit Addresses

- at each stage, the operation of doubling the channels is performed, namely, at the first stage, the channels with 0 and 1 in the high order of addresses are separated, at the second stage the channels with 0 and 1 are separated in the next category of addresses, etc., so at the last stage share channels with 0 and 1 in the lower order of addresses;

- at each stage after the operation of doubling the channels, the operation of assembling the channels is performed by arranging in the neighborhood only those channels that are required for the passage of the switched optical streams;

- at each stage, when performing the operation of assembling the channels, the optical signals of a given configuration from the optical radiation source to which the switched connections of the waveguide channels are sensitive, which leads to a change in the refractive index of the photorefractive material and these , respectively, to transfer the optical flux to an adjacent waveguide with an unchanged refractive index.

Switchable connections of waveguide channels are determined using a computer at the input and specified addresses, and from the results of calculations using a matrix of light emitters (MIS), light beams are formed that are coordinated in their spatial position with the places of switched connections of waveguide channels. Thanks to the photorefractive effect, the light beams from the MIS change the refractive index of the material of the connections of the waveguides, which ensures the deviation of information signals into the desired waveguide.

In FIG. 1 is a diagram illustrating an example of a three-digit (8-channel) device switching method in the proposed multi-channel switch at different stages of the connection of channels. Here 1 is a line of input optical channels with given switching addresses; 2 '- line of direct and inverse modulators (filters), setting on the first stage (belonging to it is indicated by one stroke), after doubling the channels, the transmission of optical signals in accordance with 0 and 1 in the highest category of addresses; 3 'is the result of the removal of gaps in the first stage of the connection of the channels; 2 "- the line of direct and inverse modulators (filters), specifying in the second stage (belonging to it is indicated by two strokes), after doubling the channels, the transmission of optical signals in accordance with 0 and 1 in the second category of addresses; 3" - the result of removing gaps on the second stage of connecting the channels; 2 "'- the line of direct and inverse modulators (filters), specifying in the third stage (belonging to it is indicated by three strokes), after doubling the channels, the transmission of optical signals in accordance with 0 and 1 in the lower order of addresses; Y" - the result of removing the gaps at the third stage of connecting the channels, bringing each of the 8 input optical signals to the selected address.

From the circuit of FIG. 1 shows that all channel connections according to the claimed method are performed in parallel within each bit of the address and at the same time sequentially (alternately) for each bit, starting with the oldest. Thus, the essence of the proposed method consists in such a connection of channels, which provides conditions for making connections of input and output channels with maximum parallelism, providing for the absence of intersections of fiber optic and electric cables. You can also notice that the proposed method is quite universal and can be used in multichannel switches not only optical but also electrical signals.

To implement the method, an optoelectronic multichannel switch is proposed, containing waveguide channels based on a photorefractive crystal (for example, lithium niobate, lithium tantalate, barium titanate, etc.) and due to the photorefraction effect, they provide an optically controlled predetermined connection of any optical input with any optical output; switching scheme for making connections of input and output channels without intersections of fiber optic and electric cables and with maximum parallelism is cascade and branched, with serial-parallel connection of N input optical channels with N output optical channels in n stages, where n = log ₂ N is the number of bits in the address, and a matrix of light emitters is introduced into the device to form control optical signals (MIS ) and a holographic optical element (GOE) and / or optical mask, optically coupled to each other and to the connections of photorefractive waveguides.

Wherein:

- the addresses for connecting the N input optical channels to the N output optical channels are set using the lines of optical modulators, and the number of lines at each step is 2, and the number of modulators in the line is N;

- for the implementation of doubling, special translucent mirrors or cubes made up of two prisms are used;

- to transfer signals from the waveguide to the waveguide during the assembly (compaction) of the channels, optical signals are used from the optical radiation source, to which the switched connections of the waveguide channels are sensitive;

- to simplify the configuration of the optical signals from the MIS, necessary for the excitation of photorefractive waveguides by laser radiation, a holographic optical element (GOE) is introduced;

- the introduced projection optics is made in such a way that the light flux from the MIS emitting coherent (laser) light in the spectral sensitivity range of the connections of the photorefractive waveguides passes through the GEE, due to which these signals acquire a given configuration, and arrives at those connections of the photorefractive waveguides that are necessary optically switch to a predetermined state to transfer signals from channel to channel;

- to simplify the configuration of the optical signals from the MIS, necessary for the excitation of photorefractive waveguides by the radiation of light-emitting diodes, an optical mask is introduced;

- the introduced projection optics is designed in such a way that the light flux from the MIS emitting incoherent light in the spectral sensitivity range of the connections of the photorefractive waveguides passes through an optical mask, due to which these signals acquire a given configuration, and is supplied to those connections of photorefractive waveguides that need to be optically switched to a predetermined state in order to transfer signals from channel to channel.

- switching of optical channels in photorefractive waveguides is performed simultaneously and simultaneously for all categories of addresses by means of simultaneous illumination with the help of MIS of those compounds where the transfer of information flows from channel to channel is required at the assembly stage.

The technical result achieved in the claimed invention lies in the fact that the design of the optoelectronic switching device xN of optical channels, based on a cascade, branched and maximally parallel connection scheme and using optical signals from the MIS with the configuration specified by their passage through the GEE, provides a given connection of any input and output channels without intersections of fiber optic and electric cables, which makes the device technological.

The main advantages of the proposed method and device for switching NxN optical channels in comparison with the prototype in the end are:

- a specified parallel connection of any input and output channels without intersections of fiber optic and electric cables;

- making connections at all stages in automatic mode with a one-time installation immediately on all lines of optical modulators of bit addresses that specify their transmission;

- making connections at all stages in automatic mode with a one-time formation in the MIS array of control optical signals and setting their configuration using the GOE and / or optical mask;

- the ability to block the design of the switch with the same at this stage (for this category of addresses) blocks.

Thus, the proposed method and device using photorefractive waveguides make it possible to obtain a predetermined connection of any input and output channels in a multi-channel switch without intersections of fiber optic and electric cables and with the other above advantages.

To improve the characteristics of the inventive optoelectronic switch (without changing its architecture), one can individually or collectively use various options for implementing optical channels — using waveguide or integrated optical structures, prismatic air defense cells, etc. Translucent mirrors can be used as optical splitters , two prismatic optical cubes, topographic optical elements, etc. elements of the same purpose. In the lines of high-speed and compact optical modulators, it is possible to use modulators not only from lithium niobate, but also based on other electro-optical materials, including integrated-optical, micromirror, semiconductor (for example, based on the Franz-Keldysh effect) and other modulators of the same destination. As sources of control optical radiation, to which the photorefractive material is sensitive, in addition to LEDs and laser diodes, for example, plasma, luminescent, and other radiation sources can be used. The holographic optical element can be made of photorefractive crystals, chalcogenide glasses and silver halide and other materials with high diffraction efficiency, not sensitive to the same radiation. The optical mask can be made of a material that does not transmit optical radiation outside the area of the holes of a given configuration. The location of the GOE and / or optical mask relative to the compounds in the waveguides should not introduce diffraction and other noises that create optical interference outside the range of each given optical signal generated by the MIS. It is possible to abandon the use of GOE and / or optical mask if the shape of the optical signal from the light emitters (in the transverse direction) corresponds to the shape of the connections in the waveguides. In multi-bit switches, it is possible to provide amplification of optical flows (with preservation of their information characteristics) using compact semiconductor lasers and matching elements. Industrial applicability

The proposed optoelectronic switch based on the effect of photorefraction is a technological and efficient device for switching NxN optical channels. This makes it possible to use it in many modern and promising systems for the transmission, reception and redistribution of information signals, in telecommunication systems, in multi-device devices and information processing and data calculation systems, including in supercomputers, in fiber-optic and integrated-optical communication systems .

An example embodiment of the invention

According to the proposed method, the operation of an optoelectronic multi-channel switch with a connection of 8x8 optical channels was modeled.

FIG. 2 explains the operation of such a switch. At the first stage, the operations of doubling the channels {G} were performed, dividing by 0 and 1 in the highest order of addresses and the operation of channel compression {2 '} in both arms, i.e. assembling open (signal) channels and removing closed channels (there is no signal in them). As a result, 4 signal channels remained in both arms. At the next stages, the same operations were carried out for subsequent bits of addresses, as a result of which at the second stage {1 ", 2"} 4 arms of 2 signal channels were formed, and at the third stage {", 2" '} - 8 arms of 1 signal channel leading the light signal to the selected address.

It is clear that if there are N = 2 ⁿ channels in n steps, all N channels can be switched to the given N addresses. Accordingly, for the common 64-bit and 128-bit switch, the number of stages is 6 and 7.

In the model used, the number of channels was doubled using an optical splitter, and their separation by 0 and 1 was performed using an inverse optical filter. As optical splitters were used optical cubes made up of two prisms {G, 1 "} (Fig. 3). Pairs of rulers of modulators {2 ', 2"}, one of which has always been an inverter, i.e. set not single, but zero bits of addresses, were performed on the basis of electro-optical crystals. Including those or other modulators, it was possible to selectively transmit light, thereby addressing the signals.

In FIG. Figure 4 shows the scheme of optical control of the connection of channels used in the model using the photorefraction effect for pumping the flow of optical information from one channel to another. For an example, 4 channels are considered, the input of which is fed 2 information flows (in 1 and 3 channels). Optical signals from MIS 1 (laser diodes) pass through a holographic optical element 2, where they acquire the desired configuration, and then enter the photorefractive waveguides 3 in the place where you want to change the direction of the optical information flow. Due to the photorefractive effect, the refractive index changes in these places, which causes the optical stream to pass into the neighboring empty channel.

In this way, all “empty” channels were removed, and at the output of the first cascade only 4 of 8 adjacent signal channels remained in two arms, and at the output of the second cascade in four arms only 2 of 4 adjacent signal channels remained.

Such a scheme for applying the photorefractive effect solves the assembly problem not only for 8-channel switches, but also for more complex ones - 16, 64, 128 channel. It is easy to verify that the scheme can be generalized further. It is important that the application locations and the configuration of the optical control signals are easily calculated upon receipt of the address data and are immediately set on the MIS, so that the implementation of the optical control does not require feedback elements and is performed immediately for all bits. Thus, thanks to the use of MIS, the optical control of the switch channels of the switch is significantly simplified and accelerated.

In FIG. Figure 5 shows the general diagram of a multi-channel switch with 8x8 channels in the initial (channels are not switched), intermediate (addressing and assembling channels) and in the final states (channel switching is completed, and information light flow). The optoelectronic switch according to the claimed method and device contained optical shutters 1, made on the basis of light modulators, which are the input ports of the switch; translucent cubes 2 ', 2 ", 2"', composed of two prisms; line modulators 3 ', 3 ", 3"', used for addressing signals; photorefractive waveguides 4 ', 4 ". The figure also shows the connections of photorefractive waveguides 5', 5", where the refractive index of the material changed under the influence of optical signals 8 ', 8 "from MIS 6', 6", which forced the optical information flow to turn into adjacent open waveguide and propagate along it. For each combination of light beams, different, pre-programmed combinations of control signals were applied at the MIS input. GOE 7 ', 7 "are needed here to specify the configuration of the optical signals generated in the MIS. The incoming and outgoing switched flows are indicated in the figure as 9' and 9".

It should be noted that the number of laser or LED emitters 6 ', 6 "does not have to equal the number of connections of photorefractive waveguides 5', 5", because not all connections require MIS signal management. In those places where the connections in FIG. 5 are shown in a lighter color, the refractive index of the photorefractive material was varied to reflect the optical signal or pass it into an adjacent waveguide. And in those places where the compounds are shown in a darker color, the refractive index did not change and was always in the “on” state, i.e. reflected the optical signal, because Optical signals traveling through these channels should always be converted to neighboring ones during assembly. In these compounds, for example, a reflecting mirror or a prism can also be provided.

The proposed method and the parallel architecture of the multichannel switch, as well as the method of optical control of channel switching, are also applicable to various switches of electrical signals (Fig. 6). In this case, the electric signal I, propagating along the electric circuit, passes further along the upper branch of the circuit, in which the contact integrated in the circuit is closed using an element (shown in a circle), which is sensitive to the control optical signal h v. Sources of information Antonov S.N. Acousto-optical devices for controlling unpolarized light and polarization modulators based on a paratellurite crystal // Zh.T.F., vol. 74, JY ° 10, 84-89 (2004).

Skinner J. D., McCormack J. S. Optical switch // US Patent JYS 4828362 (1989). G.S. Landsberg. Optics, Nauka, M., 928 s. (1976).

Wang Yu. Efficient color filtering and beam steering based on controlled total internal reflection // US Patent JYe 6 278 540 (2001).

Geokchaev F.G. Multichannel fiber optic switch // RF Patent JV ^O 2107318 (1998).

Claims

Claim

1. The method of switching NxN optical channels, based on the optical connection of any given input optical channel with any given output optical channel in a multi-channel switch, characterized in that they organize a bitwise serial-parallel connection of N input optical channels with N output optical channels, all connections channels are performed sequentially for each bit of = lg2N bits, starting from the highest, in n steps, and at the same time in parallel within each bit of the address;

- at each stage, except the last, after the operation of doubling the channels, the operation of assembling the channels is performed by arranging in the neighborhood only those channels that are required for the passage of the switched optical flows in the next stage;

- for the implementation of the assembly of channels using the effect of photorefraction, for which optical waveguides are made of photorefractive material;

- at each stage, when performing the operation of channel assembly, control optical signals of a given configuration are simultaneously and parallel to all the discharges for the given connections of the waveguides to change the refractive index of the photorefractive material in these places and, accordingly, to transfer the optical flux to the adjacent waveguide with an unchanged refractive index, moreover, the switched connection of the waveguide channels is determined using a computer at the input and specified output addresses and the result of calculating Nij via radiator array (IIA) is formed optical beams agreed in its spatial position with places switchable compounds waveguide channels.

2. A multi-channel switch, including a device for addressing signals, a device for doubling optical fluxes, an active element with waveguide channels, and also a device for controlling the change in the refractive index of the material of the waveguide channel, providing the connection of any input channels with any output channels, characterized in that the circuit switching is cascade and branched, with parallel connection of input and output optical channels in each of n stages, where n = log ₂ N is the number of bits in the address; the device for addressing signals is made in the form of lines of optical modulators, and the number of lines at each stage is 2, and the number of modulators in the line is N; a device for doubling optical flows is made in the form of an optical splitter; the waveguide channels are made of photorefractive material, and the device for controlling the change in the refractive index of the material of the waveguide channel is a matrix of light emitters (MIS), a holographic optical element (GOE) and / or an optical mask optically coupled to each other and with the connections of the photorefractive waveguide channels using a projection optics.

3. The multi-channel switch according to claim 2, characterized in that the optical splitter can be made in the form of a translucent mirror or a cube made up of two prisms.