WO2001043457A1

WO2001043457A1 - Signal exchanging device

Info

Publication number: WO2001043457A1
Application number: PCT/JP1999/006917
Authority: WO
Inventors: Nobuhiro Fujimoto
Original assignee: Fujitsu Limited
Priority date: 1999-12-09
Filing date: 1999-12-09
Publication date: 2001-06-14

Abstract

Inputted wavelength division multiplexed light is separated into components by wavelength by a wavelength demultiplexer (11) and the components are fed to a wavelength converter (21), which converts the wavelength of each component. A switch (31) comprises 8 8 cross-bar add switch elements. Each cross-bar add switch element takes up one of the three states, a cross state, a bar state, and the add state. A predetermined cross-bar add switch element of the switch (31) multiplexes a signal light (μ3) and a signal light (μ5) and transmits a signal light (μ3+μ5) to an output transmission line (#8).

Description

Specification

Signal switching equipment Technical field

The present invention relates to a device for processing a signal, and mainly relates to a device for exchanging an optical signal. Background art

With the spread of the Internet and mobile phones, the amount of information transmitted over networks has exploded in recent years. For this reason, for example, it is expected that the backbone transmission line in Japan will require a transmission capacity of several Tbps (terabit Z seconds) in the near future.

In order to meet the demand for such a rapid increase in transmission capacity, the development of wavelength division multiplexing (WDM) transmission systems has been actively pursued. Currently, it has a wavelength multiplexing transmission system of 10 Gbps Z 32 wavelengths (each transmitting 10 Gbps optical signals using 32 different wavelengths), that is, a total transmission capacity of 320 Gbps. A transmission system has been realized. In the near future, it is expected that a transmission system with a transmission capacity exceeding 1 Tbps using 100 or more wavelengths will be constructed.

In order to efficiently use large-capacity transmission lines, transmission paths between nodes can be flexibly set according to fluctuations in demand, and large-capacity WDM cross-connects (compatible with WDM transmission systems) XC: Cross Connect) node is required. A cross-connect is a device that accommodates multiple transmission lines and connects channels provided on any transmission line to any other transmission line, and is usually managed by a telecommunications carrier. Have been. Figure 1 shows an example of a network constructed using WDM cross-connects. Here, the transmission path between the optical cross connect (OXC) is a wavelength-division multiplex transmission path for transmitting wavelength-division multiplexed light in which optical signals having different wavelengths are multiplexed. Then, each optical cross-connect switches paths for each wavelength, and adjusts the number of paths to be multiplexed as necessary.

Conventionally, the optical cross connect converts a received optical signal into an electric signal and controls the path of the electric signal. However, electric signals are severely degraded in ultra-high-speed transmission conditions of several to several tens of gigabits Z seconds, and there are difficulties in downsizing. Therefore, in order to process such an ultra-high-speed signal, it is necessary to realize a cross-connect operation without converting an optical signal into an electric signal. Up to now, as an optical cross-connect that realizes a cross-connect operation without converting an optical signal into an electric signal, for example, a wavelength path (Wavelength Path) method and a virtual wavelength path (Virtual Wavelength Path) method have been proposed. ing. FIG. 2 is a diagram illustrating the concept of the wavelength path method. In the wavelength path method, one wavelength is assigned to end-to-end communication. In the example shown in FIG. 2, a wavelength λ 3 is assigned to a path from node 1 to node 9 via nodes 4, 5, and 6. In FIG. 2, “nodes” are optical cross-connect nodes.

In the wavelength path method, as described above, since one wavelength is allocated to one end-to-end communication, there is no need to convert the wavelength of the signal light within each optical cross-connect node. Therefore, the configuration of the optical switch provided in each optical cross-connect node is simplified. For example, in a cross-connect in which eight input transmission lines and eight output transmission lines are connected, switching (path selection) is performed by selecting eight routes (a process of selecting one from eight output transmission lines). Switching) can be realized, so the cross-connect may be provided with a single-stage 8x8 switch. FIG. 3 is a configuration diagram of an example of an existing optical cross-connect node used in the wavelength path method. In the example shown in Fig. 3, eight input transmission lines # 1 to # 8 and eight output transmission lines # 1 to # 8 are connected to the optical cross-connect node. 8 and output transmission lines # 1 to # 8 each transmit wavelength-multiplexed light. In this wavelength multiplexed light, optical signals of wavelengths λΐ to 8 are multiplexed here.

The wavelength division multiplexed light transmitted through each input transmission line is demultiplexed into signal lights having wavelengths of 1 to 8 by a wavelength demultiplexer (wavelength DMUX) 11, and the spatial switches 12 are respectively: ! To 1 2—8. Spatial switch 1 2—:! Reference numerals 12 to 8 denote general 8 × 8 type switches, each of which exchanges signal light of wavelength λλ to 8. The wavelength combiners 13 are provided for each of the output transmission lines # 1 to # 8, and the space switches 1 2— :! Combine the signal lights output from ~ 12-8 and send out the wavelength multiplexed light to the corresponding output transmission line. The wavelength combiner 13 is, for example, an optical power bra. An optical amplifier 14 is provided in each of the input transmission lines # 1 to # 8, and an optical amplifier 15 is provided in each of the output transmission lines # 1 to # 8. Thus, in the wavelength path method, the configuration of each optical cross-connect node is simplified. However, in terms of the entire transmission system, wavelengths cannot be flexibly assigned to each path, so the efficiency of resource (wavelength) utilization is low. For example, suppose that in the example shown in FIG. 2, a path from node 7 to node 2 via nodes 4 and 5 is to be established. In this case, wavelength λ 3 has already been used between nodes 4 and 5 for another path. Therefore, when establishing a path from node 7 to node 2, not only wavelength λ 3 cannot be used between nodes 4 and 5, but also wavelength λ 3 between nodes 7 and 4, and between nodes 5 and 2. 3 cannot be used.

FIG. 4 is a diagram illustrating the concept of the virtual wavelength path method. With virtual wavelength path method When establishing one path, an arbitrary wavelength is assigned to each link set between nodes. In the example shown in Fig. 4, the link between nodes 1 and 4 has wavelength λ3, the link between nodes 4 and 5 has wavelength λ2, the link between nodes 5 and 6 has wavelength λ5, and the link between nodes 6 and 1. Each link is assigned a wavelength λ 1.

As described above, in the virtual wavelength path method, an arbitrary wavelength can be assigned to each link set between nodes adjacent to each other, so that the efficiency of resource (wavelength) utilization is improved. For example, in the example shown in FIG. 4, suppose that a path from node 7 to node 2 via nodes 4 and 5 is to be established. In this case, the wavelength λ 2 has already been used between the nodes 4 and 5 for another path. Therefore, when establishing a path from node 7 to node 2, it is necessary to use a wavelength other than wavelength λ 2 between nodes 4 and 5, but between node 7 and 4, and between nodes 5 and 2, Any unused wavelength can be used.

However, in the virtual wavelength path method, as is clear from FIG. 4, it is necessary to convert the wavelength of the signal light at each optical cross-connect node. For this reason, for example, if eight wavelengths are multiplexed for each transmission line in a cross-connect where eight input transmission lines and eight output transmission lines are connected, appropriate switching (route switching) In order to realize), it is necessary to select 64 routes (combination of the process of selecting one out of eight wavelengths and the process of selecting one out of eight output transmission lines). In this case, the cross-connect must be provided with three 8 x 8 switches, as is well known.

FIG. 5 is a configuration diagram of an example of an existing optical cross-connect node used in the virtual wavelength path method. In FIG. 5, the input transmission lines # 1 to # 8 connected to the optical cross-connect node, the output transmission lines # 1 to # 8, and the wavelengths λ1 to λ8 multiplexed on those transmission lines Is the same as that shown in FIG.

Wavelength-division multiplexed light transmitted via each input transmission line is output to each wavelength demultiplexer. The signal light is demultiplexed into signal lights having wavelengths λΐ to 8 by 11 and input to the wavelength converter 21. The wavelength converter 21 converts the wavelength of each signal light according to the given control signal. For example, in the spatial light switch provided at the node 4 shown in FIG. 4, the wavelength λ 3 is converted into the wavelength λ 2.

As described above, the switch device has a three-stage configuration. That is, the switch device is composed of a spatial switch 12 _ 11 1 to 12-18 (first stage), a spatial switch 12 2-21 to 12-28 (second stage), and a spatial switch 12 — 3 1 to: 1 2— 3 8 (third stage). Each spatial switch is a general 8 × 8 type switch. The wavelength combiner (optical power blur) 13 combines the signal lights output from the third-stage spatial switches 12-31 to 12-38.

Thus, in the virtual wavelength path method, the configuration of each optical cross-connect node becomes complicated.

FIG. 6 is a configuration diagram of a general 8 × 8 type spatial light switch. An 8 × 8 spatial light switch is usually configured by arranging 64 cross-bar switch elements in a matrix. Each cross-bar switch element is of the 2 x 2 type (2 input Ζ 2 output type). Then, each cross-bar switch element is controlled to one of the cross state shown in FIG. 7B and the bar state shown in FIG. 7B by the applied control signal. In the cross state, the cross-bar switch element outputs the light input from # 1 to # 2 and outputs the light input from # 2 to # 1. On the other hand, in the bar state, the light input from # 1 is output to # 1 and the light input from # 2 is output to # 2.

As described above, the optical cross-connect node of the virtual wavelength path method has a larger number of spatial optical switches (the number of stages) than that of the wavelength path method, and its configuration is complicated. For example, the optical cross-connect node shown in Fig. 3 requires eight spatial light switches of 8x8 type shown in Fig. 6, while the optical cross-connect node shown in Fig. 5 A node needs 24 of them. As the number of spatial optical switches increases, the number of links between spatial optical switches and the spatial optical switches and other devices (wavelength demultiplexers, wavelength combiners, wavelength converters, etc.) The number of links to For example, the optical cross-connect node shown in Fig. 3 requires 128 links, while the optical cross-connect node shown in Fig. 5 requires 256 links. Become. The “link” is, for example, an optical fiber cable or the like.

In other words, up to now, in a wavelength division multiplexing transmission system, if resources (wavelengths) are to be used effectively, the configuration of the optical cross-connect node will be complicated. Disclosure of the invention

A main object of the present invention is to realize effective use of resources and simplification of the configuration of an optical switching device in a wavelength division multiplexing transmission system.

The switch device of the present invention has a plurality of optical switch elements and is configured to exchange wavelength multiplexed light. And at least one of the plurality of optical switch elements has a first input, a second input, a first output, and a second output, and has a first input and a second input. A first state in which the output is connected and the second input is connected to the first output, and the first input is connected to the first output and the second input is connected to the second output A second state connected to the first and second inputs and the first output, and a fourth state connected to the first and second inputs and the second output. The cross bar is controlled by any one of the 'ad switch elements.

In the above configuration, the cross 'bar' switch element multiplexes signal lights having different wavelengths when controlled to the third or fourth state. did W

Therefore, this optical switch device does not cause congestion or collision even when signal lights having different wavelengths are guided to the same output path. The cross bar ad switch element is, for example, a first gate switch provided between the first input and the first output, and a second gate switch provided between the first input and the second output. A second gate switch, a third gate switch provided between the second input and the first output, and a fourth gate switch provided between the second input and the second output. Including. In this case, the first state is obtained by setting the second and third gate switches to the 〇N state, and the second state is obtained by setting the first and fourth gate switches to the 〇N state. By turning on the first and third gate switches, a third state is obtained, and by turning on the second and fourth gate switches, a fourth state is obtained.

Note that the present invention is applicable not only to optical signals but also to electric signals. BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows an example of a network constructed using WDM cross-connects.

FIG. 2 is a diagram illustrating the concept of the wavelength path method.

FIG. 3 is a configuration diagram of an example of an existing optical cross-connect node used in the wavelength path method.

FIG. 4 is a diagram illustrating the concept of the virtual wavelength path method.

FIG. 5 is a configuration diagram of an example of an existing optical cross-connect node used in the virtual wavelength path method.

FIG. 6 is a configuration diagram of a general 8 × 8 type spatial light switch. FIG. 7A and FIG. 7B are diagrams showing the state of the existing cross-bar switch element constituting the spatial light switch.

FIG. 8 is a diagram for explaining a problem of the conventional virtual wavelength path method.

FIGS. 9A to 9D are diagrams showing the state of the crossbar switch element constituting the spatial light switch of the present invention.

FIG. 10 is a diagram for explaining the configuration and operation of an optical cross-connect node using the crossbar-advertising switch element of the present invention.

FIG. 11 is a diagram showing a specific example (part 1) of the operation of the spatial switch of the present embodiment.

FIG. 12 is a diagram showing a specific example (part 2) of the operation of the spatial switch of the present embodiment.

FIG. 13 is a diagram showing a basic configuration of a cross-bar-advertising switch element. FIG. 14 is a table showing the relationship between the state of each gate switch and the state of the crossbar / ad switch element.

FIG. 15 is a diagram showing one embodiment of a cross-bar 'ad switch element. FIGS. 16A and 16B are diagrams showing another embodiment of the gate switch of the cross-bar / ad switch element.

FIG. 16C is a diagram showing still another embodiment of the gate switch of the cross-bar-ad switch element.

FIG. 17 is a diagram showing a switch for processing a frequency division multiplexed signal.

FIG. 18 is a basic configuration diagram of a cross-bar / ad-switch element for processing an electric signal.

FIG. 19 is a diagram for explaining an application example using a cross-bar-and-switch element for processing an electric signal.

Figure 20 is a block diagram of a cross-connect node that takes into account the increase in the number of wavelength multiplexes. You.

Fig. 21 is a configuration diagram of a cross-connect node that handles eight wavelengths using a 4X4 spatial switch.

FIG. 22 is a configuration diagram of a 4 × 4 spatial switch used in the cross-connect node shown in FIG. 21.

FIG. 23 is a configuration diagram of a spatial switch from which redundancy has been removed.

FIG. 24 is a configuration diagram of another example of the spatial switch from which redundancy has been removed. BEST MODE FOR CARRYING OUT THE INVENTION

In the embodiment of the present invention, the virtual wavelength path method shown in FIG. 4 is introduced in order to effectively use resources (wavelengths) in the wavelength division multiplexing transmission system. Then, we attempt to simplify the configuration of each optical cross-connect node while realizing the virtual wavelength path method.

Hereinafter, embodiments of the present invention will be described. Before that, the reason why the configuration of the optical cross-connect node cannot be simplified in the above-described virtual wavelength path method with reference to FIG. 8 will be described. Here, as a specific example, a problem in the case where the number of switches of the optical cross-connect node shown in FIG. 5 is one in the virtual wavelength path method will be described.

In the optical cross-connect node shown in FIG. 8, for example, the signal light (λ 2) and the signal light (Λ 6) are transmitted from the signal light (λ ΐ to 8) transmitted through the input transmission line # 1. It shall be sent to output transmission line # 8. Here, it is assumed that the wavelength λ 2 and the wavelength λ 6 are converted into the wavelength 3 and the wavelength λ 5 by the wavelength converter 21, respectively. In this case, the spatial switch 12-1 sets a path in the switch so that the signal light (λ 3) and the signal light (λ 5) are guided to the output transmission line # 8. However, in the conventional method, each cross-bar switch element constituting the spatial switch is Is controlled to either the cross state or the bar state as shown in Fig. 7A and Fig. 7B, so that it is not possible to simultaneously guide multiple signal lights to one path with a spatial switch. Absent. That is, in the case of the example shown in FIG. 8, the signal light (λ 3) and the signal light (λ 5) congest or collide in the spatial switch 12-1.

In the optical cross-connect of the present embodiment, in order to solve this problem, each cross-bar switch element constituting the space switch is provided with an “add function”. Here, the “add function” refers to a function of multiplexing and outputting a plurality of input lights (particularly, a plurality of signal lights having different wavelengths from each other), or a function of combining a plurality of optical signals with one path. This is the function to output the input signal to the same path. This feature

It utilizes the property that "lights with different wavelengths do not affect each other even on the same path". Hereinafter, a cross-noise switch element having an “add function” will be referred to as a “cross-bar ad switch element”.

The cross 'bar' ad-switch element is controlled to one of four states as shown in FIGS. 9A to 9D in the case of 2 × 2 type (two-input two-output type). Here, the cross state shown in FIG. 9A and the bar state shown in FIG. 9B are the same as the conventional cross state and bar state shown in FIG. 7A and FIG. 7B, respectively. In addition, in the add state shown in FIG. 9C, the cross-bar ad-switch element multiplexes light input from # 1 and # 2, respectively, and outputs the multiplexed light to # 1. On the other hand, in the add state shown in FIG. 9D, the lights input from # 1 and # 2 are multiplexed and output to # 2.

FIG. 10 is a diagram for explaining the configuration and operation of an optical cross connect using the cross-bar-adswitch element of the present invention. The optical cross connect node is connected to input transmission lines # 1 to # 8 and output transmission lines # 1 to # 8. Shall be The wavelength demultiplexer 11, the wavelength combiner (optical power blur) 13, the optical amplifiers 14 and 15, and the wavelength converter 21 are the same as the conventional one (for example, each of the components shown in FIG. 5). Parts) can be used. The wavelength conversion unit 21 converts the wavelength of the input light into an arbitrary wavelength among the wavelengths λ1 to λ8. The wavelength converter 21 can be realized by, for example, a combination of an optical receiver (〇R: Ortical Receiver) and an optical transmitter (OS: Optical Sender). Here, as the component used as the optical transmitter, for example, a light emitting element that can arbitrarily change the wavelength of the output light, such as a wavelength tunable laser diode, is used.

Spatial switch 3 1— :! 3 to 8 are 8 × 8 type switches, each having 64 switch elements. Each switch element is the cross-bar-ad switch element described with reference to FIGS. 9A to 9D.

In this spatial switch, when a plurality of signal lights having different wavelengths are guided to the same route, those signal lights are multiplexed by an arbitrary cross-bar 'ad switch element. In the example shown in Fig. 10, the signal light (λ3) and the signal light (λ5) output from the wavelength conversion unit 21 are combined by the cross-bar-adswitch element and the signal light (Hi 3+ ぇ 5) Is output as

FIG. 11 shows a specific example of the operation of the spatial switch of the present embodiment. In this example, when signal light (λΐ) to signal light (λ8) are input via input routes # 1 to # 8, output routes # 1, # 2, # 3, # 5, # Output signal light (λ2), signal light (λ3), signal light (λ4), signal light (λ6), signal light (λ5), and signal light (λ8) to # 6 and # 8, respectively, and output route # Signal light (Λ10Λ7) shall be output to 4. In this case, the states of the other switch elements are controlled so that the signal light (λΐ) and the signal light (λ7) are guided to the cross-bar ad switch element 32. Then, the cross-bar ad switch element 32 is controlled to the add state. As a result, the signal light (λΐ) and the signal light (λ7) are multiplexed by the crossbar ad switch element 32. To output route # 4. The other signal light is guided to a predetermined output path according to the same method as the existing technology.

Note that, in the above operation example, a case where two signal lights are multiplexed in the spatial switch has been described. However, three or more signal lights can be multiplexed. For example, in the example shown in FIG. 12, three signal lights are multiplexed and guided to the output route # 4. In this case, first, the states of the other elements are controlled so that the signal light (E5) and the signal light (λ7) are guided to the cross-bar ad-switch element 33, and the cross-bar 'ad-switch element 33 is added. Control the state. Thus, the signal light (λ5) and the signal light (λ7) are multiplexed by the crossbar switch element 33, and the signal light (λ5 + λ7) is guided to the crossbar switch element 32. . In addition, the state of the other elements is controlled so that the signal light (λΐ) is guided to the cross-bar-ad switch element 32, and the cross-bar-ad switch element 32 is controlled to the add state. As a result, the signal light (λΐ) and the signal light (λ 5 + λ 7) are multiplexed by the crossbar switch element 33, and the signal light (λ1 + λ5 + λ7) is guided to the output route # 4. I will

As described above, the spatial switch of the present embodiment has the multiplexing function in addition to the switching function due to the addition of the “add function”. As a result, a situation in which a plurality of signal lights (signal lights having different wavelengths) congest or collide in the spatial switch is avoided. That is, the problem shown in FIG. 8 is solved. Therefore, as shown in FIG. 10, a virtual wavelength path method can be realized by using a one-stage spatial switch. That is, the configuration of the optical cross-connect node can be simplified.

Conventional spatial switches have the function of guiding one input signal to one output path, or the function of directing one input signal to multiple output paths (for example, an ATM switch). However, there was no function that combines multiple input signals and guides them to one output path. In the past, rather than Efforts have been made to separate the force signals so that they are not directed to the same output path, ie, to avoid crosstalk. FIG. 13 is a diagram showing a basic configuration of a cross-bar 'ad switch element. The cross bar switch element includes four gate switches 41 to 44, and realizes a cross state, a bar state, and an add state by controlling the states of the switches. Each of the gate switches 41 to 44 is supplied with a control signal via a control line (not shown), and controls one of a 〇N state (a state in which a signal is passed) and a 〇FF state (a state in which a signal is not passed) Is done. Figure 14 shows the relationship between the state of these gate switches and the function (state) of the cross 'bar' ad switch element.

This will be specifically described. To realize the cross state (see Fig. 9A), the gate switches 42 and 43 are controlled to the 〇N state, and the switches 41 and 44 are controlled to the OFF state. As a result, the signal input from input # 1 is guided to output # 2, and the signal input from input # 2 is guided to output # 1. In addition, in order to realize the no-state (see FIG. 9B), the gate switches 41 and 42 are controlled to the 〇N state, and the switches 42 and 43 are controlled to the OFF state. As a result, the signal input from input # 1 is guided to output # 1, and the signal input from input # 2 is guided to output # 1.

Furthermore, in order to realize the add 1 state (see FIG. 9C), the gate switches 41 and 43 are controlled to be in the ON state, and the switches 42 and 44 are controlled to be in the OFF state. Thus, the signals input from input # 1 and input # 2 are both guided to output # 1. Similarly, in order to realize the add 2 state (see FIG. 9D), the gate switches 42 and 44 are controlled to the ON state, and the switches 41 and 43 are controlled to the OFF state. As a result, the signals input from input # 1 and input # 2 are both guided to output # 2. FIG. 15 is a diagram showing one embodiment of the crossbar's switch element. In this example, the cross bar switch device is realized using a semiconductor optical amplifier. That is, an optical waveguide (S i〇2) 52 having a predetermined pattern is formed on the upper surface of the semiconductor substrate (Si substrate) 51, and light transmitted through the optical waveguide 52 is further transmitted as necessary. A gate switch 53 is formed for shutting off. Note that a buffer layer (Si〇2) 54 is formed on the surface of the semiconductor substrate 51. Each gate switch 53 is a semiconductor optical amplifier, to which a current source 55 is connected. Then, by controlling the current source 55 to the ON state or the OFF state, the state of the gate switch 53 is controlled. Specifically, if the current source 55 is controlled to the ON state, current is supplied to the corresponding gate switch (semiconductor optical amplifier) 53, and the light propagating through the optical waveguide 52 is amplified. . That is, the gate switch 53 is controlled to the ON state. On the other hand, if the current source 55 is controlled to the OFF state, no current is supplied to the corresponding gate switch 53, and the gate switch 53 is controlled to the OFF state. Then, as described with reference to FIG. 14, a cross state, a bar state, and an add state are realized according to a combination of ON / OFF states of these four gate switches.

FIG. 16A and FIG. 16B are diagrams showing another embodiment of the gate switch of the cross bar switch element. These gate switches are implemented using mechanical optical switches. The mechanical optical switch shown in Fig. 16A controls the position of one of the input optical fiber 61 and the output optical fiber 62 so that the light input from the input optical fiber 61 is sent to the output optical fiber 62. It is decided whether to lead. The mechanical optical switch shown in FIG. 16B depends on whether or not the shirt 63 is inserted between the end face of the input optical fiber 61 and the end face of the output optical fiber 62. It is determined whether the light input from 1 is guided to the output optical fiber 62. These mechanical switches are compatible with existing technologies. Therefore, detailed description of the configuration and operation is omitted. Further, the mechanical optical switch that can be used as the gate switch of the cross-bar-ad switch element is not limited to the one shown in the above-described example, and for example, a reflective switch may be used.

FIG. 16C is a diagram showing still another embodiment of the cross bar switch element. In this cross bar switch element, each gate switch is realized by using an optical modulator whose refractive index of light changes according to an applied voltage. In this case, each gate switch determines whether or not to allow input light to pass according to the applied voltage. As an example of this type of optical modulator, for example, a Mach-Zehnder type optical modulator (in particular, LN B_〇 ₃ optical modulator) is known.

By the way, in the above embodiments, the present invention is applied to the spatial light switch of the wavelength division multiplexing transmission system, but the present invention is also applicable to the spatial switch for processing an electric signal. However, in systems handling electrical signals, there is generally no concept of “wavelength multiplexing”. However, the concept of “Frequency Division Multiplex (FDM) is substantially the same as that of“ wavelength multiplexing ”. Therefore, in a system using frequency division multiplexing, as shown in FIG. 17, a plurality of electric signals having different frequencies can be guided to one route that is synthesized in a spatial switch. In the example shown in Fig. 17, the electric signal (fl) input from the input route # 1 and the electric signal (f7) input from the input route # 7 are given by a predetermined crossbar in the spatial switch. The output signal is synthesized by a single switch element and guided to an output route # 4.

FIG. 18 is a basic configuration diagram of a cross-bar / ad-switch element for processing an electric signal. This cross-bar'adswich element includes gate circuits 71-74. Here, each of the gate circuits 7 1 to 7 4 is an AND gate, and when “1” is given as a control signal, the signal is passed and “0” is given. Cut off the signal when received. The gate circuits 71 to 74 correspond to the gate switches 41 to 44 shown in FIG. 13 respectively, and the correspondence shown in FIG. 14 corresponds to the cross bar for this electric signal. · The same applies to the ad-switch element.

FIG. 19 is a diagram for explaining an application example using a cross-bar / ads switch element for processing an electric signal. Here, the cross-bar ad-switching element has the configuration shown in FIG. 18, in which the gate circuits 71 and 73 are controlled to be in the ON state, and the gate circuits 72 and 74 are controlled to be in the OFF state. It is assumed that That is, the cross-bar ad-switch element is in the add state shown in FIG. 9C.

It is assumed that, when the cross-bar-ad switch element is in the above state, in the time slot T1, the signal A1 is input from the input route # 1 and nothing is input from the input route # 2. In this case, a composite signal of the signal from the input route # 1 and the signal A1 from the input route # 2 is led to the output route # 1. However, since nothing is input from the input route # 2, the signal A1 is led to the output route # 1 as a result. Subsequently, in time slot T2, if signal B 1 is input from input route # 2 and nothing is input from input route # 1, similarly, signal B 1 is output to output route # 1. 1 will be derived. Thereafter, the same processing is repeated.

As described above, when the timings of a plurality of signals input to the crossbar switch element are appropriately controlled, a time division multiplexing function is realized using the crossbar switch element. Will be. Therefore, if a spatial switch is constituted by using this crossbar switch element, the switching function and the multiplexing function are integrated. This configuration contributes to downsizing of the device. By the way, as mentioned above, with the spread of the Internet and mobile phones, the amount of information transmitted via networks has exploded. For this reason, in the trunk system, it is often necessary to increase the capacity of the cross-connect switch. In a wavelength division multiplexing transmission system, the capacity of a transmission line is increased by increasing the number of multiplexed wavelengths. In the following, taking into account such a background, a cross-connect having a configuration with excellent scalability will be described. FIG. 20 is a configuration diagram of a cross-connect node in consideration of an increase in the number of multiplexed wavelengths. Here, a transition from a state in which eight wavelengths (λ 1 to λ 8) are handled to a state in which 16 wavelengths (λ 1 to λ 16) can be considered is considered. In this embodiment, a method of grouping a plurality of wavelengths and increasing the number of multiplexed wavelengths in a group unit is employed. In the example shown in FIG. 20, they are grouped every eight wavelengths. The basic configuration of this cross-connect node is the same as that of the cross-connect node shown in FIG. However, the wavelength demultiplexer 81 has a function of demultiplexing 16 wavelengths (λΐ- え 16), and the wavelength combiner (optical power bra) 82 has 16 wavelengths (λΐ- え 16). It has a function to merge

In the initial stage of the cross-connect node, one wavelength conversion unit 83Α and one spatial switch 84 4 are provided for each transmission path. The wavelength converter 83 A is the same as the wavelength converter 21 shown in FIG. 10, and performs wavelength conversion in the range of wavelength 1 to wavelength λ8. The spatial switch 84 is an 8 × 8 type switch, and is composed of 64 crossbar switch elements. In this state, transmission lines # 1 to # 8 can each transmit up to eight waves.

When this cross-connect node is added, a wavelength converter 83 B and a spatial switch 84 B may be added for each transmission line. The wavelength conversion unit 83B performs wavelength conversion in the range of the wavelength λ9 to the wavelength λ16. Also, spatial switch 8 4 Β Is the same as the spatial switch 84A. In the state where the expansion has been completed in this way, the transmission lines # 1 to # 8 can transmit up to 16 wavelength-multiplexed signals, respectively. Here, assuming that the transmission speed of the transmission signal is 10 Gbps, the throughput of this cross-connect node is 1.28 (10 0 Gbps) from 64 (10 Gbps X 8 wavelength X 8 transmission line) Gbps. Gbps x 16 wavelength x 8 transmission line) Tbps.

If the wavelength demultiplexer and the wavelength combiner were designed in consideration of the future increase in capacity, simply adding a wavelength conversion unit and a spatial switch would make 8 wavelengths—16 wavelengths → 24 wavelengths—3 wavelengths. Like 2 wavelengths, the number of multiplexed wavelengths can be easily increased in units of 8 wavelengths.

If the above-described extension method is adopted, the extension of the wavelength converter and the spatial switch for the wavelengths λ 9 to λ 16 does not affect the system in use. Therefore, this method is particularly useful in networks that cannot be shut down (eg, public networks).

Next, miniaturization of the spatial switch will be described. In the above-described embodiment, it has been described that the number of the spatial switches (the number of stages) can be reduced by configuring the spatial switches using the cross-bar / ad switch elements. Specifically, a configuration for reducing the size of the spatial switch (the number of switch elements) is shown.

Paying attention to the cross-connect node shown in FIG. 20, 16 wavelengths can be processed by providing two 8 × 8 spatial switches in parallel for each transmission path. Therefore, by analogy with this, it should be possible to process eight wavelengths by providing two 4X4 type spatial switches in parallel. FIG. 21 is a configuration diagram of a cross-connect node that handles eight wavelengths using a 4 × 4 spatial switch. In this cross-connect node, the signal light (λ1 to λ4) And the signal light (λ 5 to λ 8) are subjected to wavelength conversion by the wavelength conversion units 91 1 and 91 1, respectively, and then input to the spatial switches 92 A and 92 B. The space switches 92A and 92B have the same configuration as each other, and are 4x4 type switches. However, each of the spatial switches 9 2 A and 9 2 B needs to be able to guide the input signal to any of the eight output transmission lines # 1 to # 8-that is, each of the spatial switches 9 Each of 2A and 92B must have eight output routes.

FIG. 22 is a configuration diagram of a 4 × 4 type spatial switch used in the cross-connect node shown in FIG. This spatial switch is composed of 16 cross 'bar-' ad-switch elements. Each switch element has two inputs and two outputs. Conventionally, as shown in FIG. 6, only one of the outputs of the last-stage switch element was used. However, in this embodiment, as shown in FIG. 22, both outputs connected to the last-stage switch elements 101 to 104 are used. As a result, eight output routes are secured. That is, in the cross-connect node, a spatial switch having 4 × 4 elements is used as a 4 × 8 spatial switch.

As described above, since the spatial switches 92A and 92B each have eight output routes, each wavelength combiner (optical power bra) 82 has the function of "16: 1". You need what you have.

The cross-connect node shown in FIG. 21 basically has the same function as the cross-connect node shown in FIG. Here, when these are compared, as shown in FIG. 21, the wavelength combiner 13 used in the cross-connect node shown in FIG. 10 only needs to have a function of cascading eight signals. Since the wavelength combiner 82 used in the cross-connect node needs to have a function of combining 16 signals, it is slightly disadvantageous in terms of device size and manufacturing cost. However, the spatial switch 31 used in the cross-connect node shown in FIG. 10 has a configuration with 64 (8 × 8) elements for each transmission path, whereas the spatial switch 31 shown in FIG. The spatial switch 92 used in the cross-connect node has 32 (4 × 4 × 2) elements for each transmission path. Here, as the scale of the switch (here, the number of switch elements) becomes smaller, the manufacturing yield increases, as is well known. Therefore, a configuration using a small spatial switch as in the configuration shown in FIG. 21 is expected to greatly reduce the manufacturing cost. When the number of switch elements is reduced, the size of the device can be reduced as a matter of course. This effect becomes even more remarkable when considering that a control line is connected to each switch element.

Furthermore, focusing on the configuration of the cross-connect node shown in Fig. 21, two spatial switches 92A and 92B are provided for each transmission line, and eight output routes are provided for each spatial switch. I have. The output path of each spatial switch is connected to the corresponding wavelength combiner 82. For this reason, if one set of spatial switches 92A and 92B provided for each transmission line is considered as one spatial switch, two spatial switches are provided between the one spatial switch and each wavelength combiner 82. There will be a transmission path. That is, the configuration of the cross-connect node shown in Fig. 21 is somewhat redundant, and there is room for improvement.

FIG. 23 is a configuration diagram of a spatial switch from which redundancy has been removed. This spatial switch can be obtained, for example, by forming the spatial switches 92A and 92B shown in FIG. 21 on one semiconductor substrate. However, the output routes that should be connected to the same wavelength combiner are connected to each other. For example, in the example shown in FIG. 23, the first output of the switch element 111 of the spatial switch 92A and the first output of the switch element 112 of the spatial switch 92B are connected to each other. . As a specific implementation method, for example, each output path of the spatial switches 92A and 92B is formed using a waveguide. Then, the corresponding waveguides may be connected to each other. Thus, a spatial switch having eight inputs and eight outputs is obtained by using two 4 × 4 spatial switches. This spatial switch contributes to the miniaturization of the cross-connect node. For example, in the cross-connect node shown in Fig. 21, if one set of spatial switches 92A and 92B is replaced with the spatial switch shown in Fig. 23, eight signals are combined as each wavelength combiner. A force bra can be used. Also, the number of lines connecting the spatial switch and the wavelength combiner is halved, which greatly contributes to the miniaturization of the device size.

In the example shown in Fig. 23, an 8-input / 8-output spatial switch is realized by arranging two 4-by-4 element spatial switches, but in general terms, the NXN element spatial switch is By arranging two, a spatial switch of 2N input Z2N output can be realized. Fig. 24 shows a 4-input Z 4-output spatial switch obtained by arranging two 2 X 2 element spatial switches.

In this case, if a general matrix configuration is used to realize a spatial switch of 2 N inputs Z 2 N outputs, 2 NX 2 N = 4 N ² switch elements are required. If the configuration described with reference to 23 is introduced, when realizing a spatial switch of 2 N input Z 2 N output, the number of required switch elements is 2 XNXN = 2 N ² . That is, if the configuration described with reference to FIG. 23 is introduced, when realizing a spatial switch having the same function, the number of switch elements can be halved as compared with the related art.

Note that the spatial switch shown in the above embodiment is composed of a plurality of cross 'bar' ad switch elements, but the switch of the present invention does not necessarily require that all switch elements be cross bar ad switch elements. . That is, the switch of the present invention may be a mixture of the existing cross-persistent switch and the cross-bar-ads switch element of the present invention. Further, in the above-described embodiment, the case where the present invention is mainly applied to the optical cross-connect node has been described, but the present invention is not limited to this. That is, the present invention can be applied to, for example, an optical switch. The configuration of the optical switch to which the present invention is applied is basically the same as the configuration of the optical cross-connect node.

Although the optical switching equipment and the optical cross-connect node are the same equipment in a broad sense, there are differences when considering specific operations. The exchange usually analyzes the transmitted signal and performs a process of setting a route based on the analysis result. For this reason, switches are generally installed with signal analysis software. Also, since the signal needs to be analyzed, the route switching time in the spatial switch must be shorter than the time slot of the signal. Therefore, when the present invention is applied to an optical switch, the operation speeds of the wavelength conversion unit and the spatial switch need to be sufficiently high. On the other hand, a cross-connect node is a device that switches a path according to given route information, and does not require much high-speed operation.

As described above, according to the present invention, by configuring a spatial switch using the cross 'bar' ad-switch element, the number (the number of stages) of spatial switches provided in the cross-connect node (including the switch) in the wavelength division multiplexing transmission system Can be reduced.

Also, it is easy to add cross-connect nodes. Further, the size of the spatial switch provided in the cross-connect node can be reduced.

Claims

The scope of the claims

1. A switch device having a plurality of switch elements and exchanging a multiplexed signal in which a plurality of signals are multiplexed,

At least one switch element among the plurality of switch elements has a first input, a second input, a first output, and a second output, and has a first input and a second output. A first state of connecting and connecting the second input and the first output; a second state of connecting the first input and the first output and connecting the second input and the second output One of the following states: a third state connected to the first and second inputs and the first output; and a fourth state connected to the first and second inputs and the second output. Switch device controlled to state.

2. An optical switch device having a plurality of optical switch elements and exchanging wavelength multiplexed light,

At least one of the plurality of optical switch elements has a first input, a second input, a first output, and a second output, and has a first input and a second output. And a second state of connecting the second input and the first output, connecting the first input and the first output, and connecting the second input and the second output One of a second state, a third state connected to the first and second inputs and the first output, and a fourth state connected to the first and second inputs and the second output. Optical switch device controlled to one state.

3. The optical switch device according to claim 2, wherein

The switch element controlled to any one of the first to fourth states is: A first gate switch provided between the first input and the first output; a second gate switch provided between the first input and the second output; A third gate switch provided between the input and the first output, and a fourth gate switch provided between the second input and the second output). The above first to fourth states are realized by controlling the state of the fourth gate switch.

4. The optical switch device according to claim 3, wherein

Each of the first to fourth gate switches is a semiconductor optical amplifier.

5. The optical switch device according to claim 3, wherein

Each of the first to fourth gate switches is a mechanical optical switch.

6. The optical switch device according to claim 3, wherein

Each of the first to fourth gate switches is an optical modulator.

7. A switch device having a plurality of switch elements for exchanging electric signals transmitted in a frequency division multiplexing system,

At least one of the plurality of switch elements is:

A first input, a second input, a first output, and a second output, wherein the first input is connected to the second output and the second input is connected to the first output A first state, connecting a first input and a first output, and connecting a second input and a second output, a first state, a first and a second input, and a first output An optical switch device controlled to one of a third state connected to the first state and a fourth state connected to the first and second inputs and the second output.

8. An optical switching device that is connected to a plurality of input transmission lines and a plurality of output transmission lines and exchanges wavelength-multiplexed light,

A plurality of wavelength demultiplexers provided for each of the plurality of input transmission lines and for demultiplexing the wavelength division multiplexed light transmitted via the corresponding input transmission line for each wavelength;

A plurality of wavelength converters provided for each of the plurality of wavelength demultiplexers, for converting the wavelength of the signal light output from the corresponding wavelength demultiplexer;

A plurality of switches provided for each of the plurality of wavelength converters and guiding signal light output from the corresponding wavelength converter to the plurality of output transmission paths;

A plurality of optical combiners provided for each of the plurality of output transmission paths, for combining the signal lights guided to the corresponding output transmission paths by the plurality of switches,

An optical switching device, wherein the plurality of switches are each configured of a cross-bar-ad switch element controlled to any one of a cross state, a bar state, and an add state.

9. An optical switching device that is connected to an input transmission line and a plurality of output transmission lines and exchanges wavelength-multiplexed light,

A wavelength demultiplexer for demultiplexing the wavelength-division multiplexed light transmitted through the input transmission line for each wavelength;

A first wavelength converter for converting the wavelength of the signal light output from the wavelength demultiplexer; and a first switch for guiding the signal light output from the first wavelength converter to the plurality of output transmission lines. When,

An optical combiner that is provided for each of the plurality of output transmission paths and combines the signal lights guided to the corresponding output transmission paths,

When increasing the wavelength multiplexing number of the wavelength multiplexed light, the wavelength An optical switching device to which a second wavelength converter for converting the wavelength of signal light to be input and a second switch for guiding signal light output from the second wavelength converter to the plurality of transmission paths are added.

10. An optical switching device which is connected to an input transmission line and a plurality of output transmission lines and exchanges wavelength-division multiplexed light.

First and second wavelength converters for converting the wavelength of the signal light output from the wavelength demultiplexer;

First and second switches for guiding the signal lights output from the first and second wavelength converters to the plurality of output transmission paths, respectively;

An optical combiner provided for each of the plurality of output transmission lines, for combining the signal lights guided to the corresponding output transmission lines by the first and second switches, wherein the wavelength of the wavelength-multiplexed light is The maximum number of multiplexes is 2 N,

The first and second switches are configured by arranging NXN cross-bar / ad-switch elements controlled to any one of a cross state, a bar state, and an ad state, respectively. Optical switching equipment.

11. The optical switching device according to claim 10, wherein

Routes from the first and second switches to the same output transmission line are connected to each other.

1 2. NXN cross-bar / ad-switch elements controlled to any one of the cross state, the bar state, and the ad state. The first switch

A plurality of first waveguides respectively connected to a plurality of outputs of the first switch;

A second switch constituted by arranging N X N cross bar-ad switch elements controlled to any one of a cross state, a bar state, and an add state;

A plurality of second waveguides respectively connected to the plurality of outputs of the second switch;

A switch device, comprising: a first waveguide and a second waveguide connected to the same destination and connected to each other.