CN1717113A - A Optical-Burst/Packet-Switching Hybrid Switch Structure - Google Patents

Abstract

This invention provides a photoelectric mixed exchange structure supporting light burst/packet exchange, which takes optical exchange as the main thing and applies a buffer storage channel composed of a photoelectric converter, RAM buffer storage and an electro optical converter connected by electric field, takes electric-field buffer storage to replace light buffer storage (FDL) and adds with suitable electric-field exchange. This invention utilizes electric-field buffer storage to solve conflict effectively, which is the main reason for loosing data in optical network.

Description

A Optical-Burst/Packet-Switching Hybrid Switch Structure

technical field

The invention belongs to the technical field of switching control in communication systems, and particularly relates to the switching structure of core nodes in optical burst/packet switching networks.

Background technique

With the scale of the Internet and the exponential growth of Internet services, people's demand for network bandwidth is also increasing sharply, so the requirements for the transmission capacity of the network and the processing capacity of routers and switches are also increasing. Dense Wavelength Division Multiplexing (WDM for short) can multiplex multiple wavelength channels on one optical fiber, greatly improving the transmission capacity of a single optical fiber. Utilizing it can establish a broadband basic network to meet the growth of Internet services, and better solve the problem of network transmission. The current technology can multiplex 80-120 wavelengths on one optical fiber, with a total transmission capacity of about 400Gb/s.

On this basis, four technologies for transmitting data on WDM networks have been developed: broadcast-selective reception, wavelength routing, optical burst switching (optical burst switching, OBS), and optical packet switching (optical packet switching, OPS). The switching granularity (basic switching unit) provided by wavelength routing is wavelength, which is not suitable for the transmission of bursty packet services. It needs to cover the hierarchical structure of combined Internet packet services on it, which increases the complexity of the system and reduces the transmission rate. efficiency. In order to reduce complexity and increase efficiency, it is required to transmit IP layer data directly on the WDM optical network, which is the main reason for the emergence of optical burst switching and optical packet switching technologies. Among them, the all-optical packet switching technology is considered to be the most fundamental method to overcome the bottleneck of traditional electrical switching processing, but there are still some difficulties in this technology, such as all-optical storage, optical timing/synchronization, etc. For this reason, it is an effective way to realize a large-capacity switching system by fully combining and giving full play to the advantages of existing optical and electrical technologies to construct an optical-electrical hybrid switching system, such as Optical Burst Switching (OBS) technology, which effectively combines wavelength routing and the advantages of optical packet switching.

In the optical burst switching network, the burst data (Burst) carrying user services can be regarded as an ultra-long packet composed of a large number of data packets, and the packet header of this ultra-long packet is the control packet (Burst Header) of the burst data. Packet, BHP). The BHP contains information about the burst data, such as offset time (Offset Time, that is, the interval between the source sending the BHP and the corresponding burst data), burst length, data channel (wavelength), etc. Different from traditional packet switching, BHP and burst data are separated on the physical channel, that is, out-of-band signaling is used: in a dense wavelength division multiplexing transmission system, one (or more) dedicated wavelength channels can be used As a control channel, it is used to transmit BHP, and other wavelength channels are used as data channels, and there is a one-to-one correspondence between BHP and burst data.

In optical burst switching, in order to reduce the delay of connection establishment and improve channel utilization, a one-way reservation mechanism is generally adopted, that is, before the source end actually sends burst data, it first sends a BHP, and after a certain offset time Then, the burst data is sent, so that the BHP arrives at the intermediate switching node of the optical burst switching network before the burst data for resource reservation. BHP converts electrical signals into electrical signals for processing at intermediate switching nodes, including reservation of outgoing port wavelengths and configuration of switching matrix, etc., to ensure that when burst data arrives, the corresponding all-optical data channel has been configured, so as to realize the transparency of data in the optical domain transmission. From the perspective of completed functions, BHP is very similar to signaling in traditional circuit switching networks. It is in this sense that BHP is also called signaling messages. But different from traditional signaling, optical burst switching signaling is a one-way reservation mechanism without waiting for the feedback confirmation from the destination end.

As we all know, unlike point-to-point transmission lines, each node in a network must have the ability to output input data from a specific output channel at a specific time. This ability is called the ability to exchange data, which is achieved through a specific switching structure Achieved. And different switching structures have relatively large differences in the ability to realize switching, so the quality of the switching structure directly affects the performance of the network.

An optical burst switching network is mainly composed of edge nodes, core nodes and DWDM links (see Figure 1). Among them, the DWDM link includes a control channel (Control Channel) and a data channel (Data Channel). The schematic diagram of the core node structure is shown in Figure 2. All the modules above the optical switching module are collectively referred to as Switch Control Unit (SCU), which controls the operation of the optical switching module so that burst data can pass through correctly. The optical switch matrix will switch the burst data on the specified wavelength channel of the specified input port to the corresponding output wavelength channel at a specified time according to the instruction of the switch control unit. The structure of separating BHP and burst data can avoid converting all data to the electric domain at the core node, and also avoids the use of a large amount of memory. For the core nodes of optical burst switching and optical packet switching networks, the optical switching modules are universal, and the optical switching modules in optical burst switching are used as examples below. Meanwhile, the present invention focuses on the optical switch module, so the switch control unit is omitted in the following introduction.

Existing optical switching modules mainly include the following types: (see literature Lisong Xu, Harry G. Perros, and George Rouskas, North Carolina State University, "Techniques for Optical Packet Switching and Optical Burst Switching", IEEE Communications Magazine January 2001, Volume: 39, Issue: 1, Jan. 2001, Pages: 136-142.)

1. Classic switching structure with Fiber Delay Line (FDL) at the input

As shown in Figure 3, this structure is a classic switching structure, which consists of two parts: scheduling and switching. Among them, the scheduling part mainly solves the scheduling and conflict resolution of BHP, while the switching part switches the input burst data to the designated output port. Because two bursts of data cannot be output from the same FDL output at the same time, there is a head-of-line blocking problem in this switching structure, that is, on each input wavelength channel, the front burst data will interfere with the following burst. Sending data causes blockage. For example, assuming that each burst of data lasts time T, if two sequential bursts of input wavelength channel i are to be sent from output wavelength channel j and output wavelength channel k respectively. If the first burst of data needs to be delayed by T, the second burst of data must also be delayed for more than T, otherwise at time T, two bursts of data are output from the same buffered wavelength channel, causing conflicts. However, if the first burst of data needs to be delayed by nT (n>1), then the second burst of data can be sent without delay as long as there is no conflict at port k. Due to the existence of head-of-line blocking, the ability of FDL to resolve conflicts will be greatly affected, and the improvement of loss performance will be very limited. At the same time, in this structure, FDL resources cannot be shared, resulting in high cost.

2.Broadcast—select switching structure

As shown in Figure 4, this structure consists of three parts: wavelength encoding, buffering, and wavelength selection. Under certain conditions, it can perform the exchange of N wavelength input and N wavelength output K time slots. This structure requires only one wavelength of signal output at each output port at the same time. In the encoding part, N fixed wavelength converters (fixed wavelength converter, FWC) are used to convert each input wavelength into a signal without the same wavelength, and then combined and sent to the buffer part. In the buffer part, the splitter and FDL are used to copy the signal sent by the wavelength coding part to each time slot, and then the splitter, optical switch, and multiplexer are used to construct a space division switching structure to switch the signal to the output end. Finally, in the wavelength selection part, the demultiplexer, optical switch, and multiplexer are used to select the signal of a certain wavelength on a certain output end at a certain time, so that the purpose of optical switching is achieved. Because the wavelength is selected at the output, the wavelength at the output is variable.

The advantage of this structure is that the principle is simple and the control algorithm is easy to realize. However, due to broadcasting, each channel is full of unnecessary information on the channel, so the resource utilization rate is low; and the multiplexing, optical switch, and demultiplexing equipment at each output end cannot be shared, and many devices are required. The price is high. Moreover, after passing through the decomposer, the optical signal is divided into N parts, the energy of the optical signal is greatly reduced, and the probability of signal error is increased.

3. Shared transformation pool structure

As shown in Figure 5, this structure consists of a 2N×2N switch matrix, N TWCs and N ODLs, and the N TWCs are used to adjust the data to the output wavelength. The N internal cycle wavelength channels can make the low-priority data sent to the ODL to be delayed again when the high-priority data and low-priority data conflict, so as to realize the support for the priority. This switching structure requires more resources; half of the wavelengths cannot be output, the wavelength utilization efficiency is not high, and too many wavelengths make the AWG cost too high; although it can use the delay again to provide priority, but due to weak There is a limit to the number of times the optical signal can be delayed, so the priority effects provided are limited.

From the above description, it can be known that the current optical burst switching research mainly has the following problems:

1) Optical burst switching provides Best Effort Services, and the theoretical lower limit of the loss rate is the full-busy probability calculated by the Irish formula. Compared with packet switching in the electrical domain, its loss rate is too high.

2) FDL cannot provide random access, but can only provide fixed delay, the equipment is bulky and has optical power loss. Moreover, its series design and depth design are more complicated, and there are many factors to be considered. Data caching and limited ability to resolve conflicts.

Contents of the invention

The purpose of the present invention is to provide a kind of optical burst/packet switching optical hybrid switching structure for the core node in the optical burst/packet switching network, adopt the switching structure proposed by the present invention, can effectively reduce the loss rate, and can flexibly Provides support for prioritization.

For the convenience of description, the following definitions are first given:

Edge node: A node located at the edge of the OBS network, which mainly realizes the generation of burst data and photoelectric conversion in terms of function.

Core node: a non-edge node in the optical burst switching network, which realizes optical switching of optical burst data.

Switching: The process of sending burst data input from a specific wavelength channel of a specific input port at a specific time from a specific wavelength channel of a specific output port at a specific time.

Loss rate: The loss rate of data packets in the network.

Collision: When multiple burst data packets go to a specific wavelength channel of the same output port at the same time, "collision" occurs, which is also called "external blocking" in packet switches.

Latency: The time difference between burst data being sent into and out of a device.

Transmission error: The burst data is transmitted from the source end to the destination end through the OBS network, but due to errors introduced during the transmission process, the data sent by the source end is inconsistent with the data received by the destination end, which is called a transmission error.

A kind of photoelectric hybrid switching structure (as shown in Figure 6) that supports optical burst/packet switching provided by the present invention, it comprises: an optical switching matrix, and described optical switching matrix has (M+N*n) input port and (M+N×n) output ports, M represents the number of buffered channels, N represents the number of incoming or outgoing ports, N×n represents the number of input (output) wavelength channels, and n represents each The number of wavelength channels included in the input port or output port; N input ports, N output ports, N wave splitters, N wave combiners, N×n tunable wavelength converters (TWC); the input port 1 passes The demultiplexer decomposes n wavelength channels, and the n wavelength channels are respectively connected to any n input ports of the optical switch matrix using optical fibers; the input port 2 is decomposed into n wavelength channels through the demultiplexer, and the n wavelength channels are respectively connected to any n wavelength channels using optical fibers. Connect to any n input ports of the optical switch matrix; the rest of the input ports and so on constitute N input ports; all the input ports use the N×n input ports of the optical switch matrix; corresponding to the input port 1, from the optical The n wavelength channels output by the n output ports of the switch matrix are connected to n tunable wavelength converters through optical fibers, and each tunable wavelength converter is connected to the multiplexer through optical fibers to form output port 1; corresponding to input port 2, from The n wavelength channels output by the n output ports of the optical switch matrix are connected to n tunable wavelength converters through optical fibers, and each tunable wavelength converter is connected to the multiplexer through optical fibers to form output port 2; the remaining output ports follow this By analogy, N output ports are formed; all output ports use N×n output ports of the optical switch matrix;

It is characterized in that it also includes:

A buffer channel is composed of photoelectric converters, RAM caches, and electro-optical converters connected in turn through the electrical domain, and there are M buffer channels in total; the input end of each buffer channel is connected to the output port of the optical switch matrix through optical fibers, and the output port of each buffer channel The output end is connected to the input port of the optical switch matrix through an optical fiber.

It should be noted,

The input port and output port of the optical switch matrix mentioned above can only be connected to one channel.

The role of the demultiplexer is to decompose the input multi-wavelength composite optical signal into multiple single-wavelength optical signals for output, and each single-wavelength optical signal corresponds to a different wavelength.

The function of the optical switch matrix is to switch the optical signal input from a certain input port of the optical switch matrix to the specified output port of the optical switch matrix for output during a specified time period.

The function of the photoelectric converter is to convert the input optical signal of any wavelength into an electrical signal output through photoelectric conversion;

The function of the RAM buffer is to store the input electrical signal for a certain period of time and then output the electrical signal; the function of the electro-optic converter is to reconvert the electrical signal input by the RAM buffer into an optical signal of a certain wavelength.

The function of the tunable wavelength converter is to convert the input optical signal of any wavelength into the output optical signal of the specified output wavelength.

The function of the multiplexer is to combine multiple input single-wavelength optical signals into one multi-wavelength optical signal for output, and each input single-wavelength optical signal corresponds to a different wavelength.

Working process of the present invention:

The multi-wavelength composite optical signal comprising a plurality of burst data enters the ingress port of the switching structure of the present invention through the optical fiber, and is decomposed into single-wavelength optical signals of different wavelengths after passing through the wave splitter (there is only one burst at the same time on each wavelength). The data is being transmitted) and connected to the input port of the optical switch matrix through optical fiber. After the burst data arrives at the optical switch matrix, the burst data is switched to a specific output port of the optical switch matrix for output according to the processing result of the previously received corresponding burst control packet. If there is no conflict, switch to an output port corresponding to the output port of the optical switch matrix and the switch structure; if there is a conflict, switch to a certain output port corresponding to the optical switch matrix and the buffer channel. For the conflicting burst data, after being output from the output port of the optical switch matrix, it is sent to the buffer channel through the optical fiber for delay so as to resolve the conflict. First, the burst data enters the photoelectric converter and converts it into an electrical signal, then sends it to the RAM cache through an electrical connection for delay, and then takes it out from the RAM cache and sends it to the electro-optical converter through an electrical connection to convert it into an optical signal, and finally from the electro-optic converter It is sent back to the input port of the optical switch matrix through the optical fiber. The optical burst data after the buffer channel delay is switched to the output port again without conflict according to the processing result of the corresponding burst control packet for output. For the burst data without conflict and the burst data whose conflict is resolved through the buffer channel, after being output from the optical switching matrix, it is converted to a designated wavelength through an adjustable wavelength converter. Multiple burst data that have been converted to specified wavelengths (the converted burst data use different wavelengths) are connected to the multiplexer through an optical fiber, and are processed by the multiplexer to form a multi-wavelength multiplexer that contains multiple burst data. The optical signal is sent to the output port for output.

Innovation of the present invention:

The main idea of the switching structure proposed by the present invention is based on optical switching, adopts a buffer channel composed of photoelectric converters, RAM caches, and electro-optical converters connected through electrical domains in turn, replaces optical buffer FDL with electrical domain buffers, and appropriately Supplemented by electric field exchange. Compared with the optical buffer FDL, it has the characteristics of effectively reducing the loss rate of the network, reducing the delay of error/loss retransmission, and effectively supporting multiple priorities.

The advantages of a photoelectric hybrid switching structure supporting optical burst/packet switching provided by the present invention are:

1) Reduce the loss rate of the network and improve network performance. The most important cause of data loss in optical networks is collision. This switching structure can effectively resolve conflicts by utilizing the electric domain cache, and its ability to resolve conflicts is much better than that of optical domain conflict resolution schemes. As shown in Figure 7, ti1 represents the original arrival time of the i-th burst data, ti2 represents the original departure time of the i-th burst data, ti1' represents the arrival time of the i-th burst data after passing through the cache, and ti2' represents The departure time after the i-th burst data passes through the cache. As shown in the figure, the BHPs of the three bursts arrive sequentially, and they give the expected arrival times t11, t21, t31, and departure times t12, t22, t32 of the corresponding bursts. It can be seen from the figure that when the burst data 3 arrives, the burst data 1 is being sent, and the burst data 3 must be cached and delayed before sending to resolve the conflict. If FDL is used to resolve conflicts, the delay time must be an integer multiple of a fixed time (set as T). In this way, even if there is a gap in which data can be transmitted, the data cannot be sent in that gap because of the fixed time delay. It can be found in the accompanying drawings that the sending process of burst data 3 conflicts with burst data 2 after being delayed T by the optical delay line, even though the time gap between burst data 1 and burst data 2 can send burst Send data 3. It can be seen from the schematic diagram that burst data 3 must be delayed by 4T to be transmitted without conflict, which increases the transmission time of burst data from the source to the destination, and the weakening of the optical signal after the 4T delay increases, making it easier to introduce errors. These problems can be avoided if we adopt the photoelectric cache structure proposed in this patent. As shown in the figure, when burst data 3 arrives at t31 and conflicts with burst data 1, the photoelectric conversion is performed on it and buffered in the electric domain RAM, and then proceeds after a delay of Δt (Δt=t31'-t31) Electro-optic conversion, sent back to the optical domain transmission. Since the delay of the electric domain RAM is arbitrary, the gap between the burst data 1 and the burst data 2 can be used to transmit the burst data 3 after a delay Δt less than T. Because Δt<<4T, the transmission time from the source to the destination is greatly shortened; and the optical signal converted from electro-optic is a regenerated optical signal without the problem of attenuation due to delay, which also reduces the probability of transmission errors.

2) Reduce the time delay of error/loss retransmission and reduce the network load caused by retransmission, thereby increasing the effective bandwidth to a certain extent. OBS only provides best-effort service, that is to say, it does not guarantee the quality of service, so the handling of conflict packet loss and transmission error is completed by the upper layer protocol. When there is a conflict and packet loss, the upper layer protocol can only solve it by retransmission; for transmission errors, the upper layer protocol can correct it through an efficient coding scheme, or require the source to retransmit. Efficient coding schemes can indeed correct certain errors, but when there are many errors, the redundancy cost for error correction is too high, and it is not as effective as retransmission. It can be seen that retransmission is an important means to provide reliable transmission, but retransmission will increase the network load and reduce the effective transmission performance of the network. From the analysis of 1), it can be seen that the switching structure proposed in this patent can reduce the loss rate and the probability of transmission errors. So this also reduces the probability of retransmission, that is, indirectly reduces the load on the network and increases the effective bandwidth.

3) Different priorities can be provided for different services more flexibly and conveniently. At present, there are not many methods that can provide QoS in optical burst switching, most of which are based on offset time or burst aggregation. The method based on offset time will introduce a large delay, and the priority that can be distinguished is very limited. The method based on burst aggregation is implemented at the edge nodes, which is not very helpful for providing core network QoS. Other methods, such as using FDL to provide limited cache, also provide limited QoS and are inflexible due to the defects of FDL itself. In the switching structure proposed in this patent, the mature technology of the electric field can be used to easily obtain almost unlimited storage time and storage capacity, and at the same time, random access is also possible. Therefore, we can allocate transmission time slots that meet their priority requirements for services with different priorities, that is to say, we can obtain almost the same priority support as the pure electric domain transmission network.

4) It can support the exchange of wavelength granularity to a certain extent. In the current switching structure, the loss rate of burst data is much higher than that of packet switching in the electrical domain. When circuit switching (that is, wavelength switching) is required for a long time, a higher loss rate will be introduced. However, in this structure, under the condition that the burst loss rate is guaranteed to be stable, some wavelength channels in the port can be used to provide certain wavelength switching.

To sum up, the switching structure proposed in this patent can effectively reduce the loss rate of the network, reduce the error/loss retransmission delay, effectively support multiple priorities, and provide wavelength granular switching. It is a switching structure with good performance.

Description of drawings

Figure 1 is a schematic diagram of the existing OBS network structure

Figure 2 is a schematic diagram of the core node structure

Among them, IDC represents the input data channel, ODC represents the output data channel, ICC represents the input control channel, OCC represents the output control channel, FDL represents the fiber delay line, and BCP represents the burst control packet.

Figure 3 Schematic diagram of input buffer switching structure

表示可调波长变换器，

表示光延迟线。in,

Indicates a tunable wavelength converter,

represents an optical delay line.

Figure 4 Schematic Diagram of Broadcast Selective Switching Structure

Among them, K represents the maximum number of delay segments of the optical delay line; N represents the number of input wavelength channels of the switch structure; the function of the resolver is to copy a signal into multiple identical signals; the function of the combiner is to combine multiple The channels are combined into one channel; the role of the optical switch is to allow or prohibit the passage of optical signals. denotes a fixed wavelength converter, represents an optical delay line, Indicates the resolver, Indicates the optical switch, Represents a combiner.

Figure 5 Schematic diagram of shared transformation pool structure

Wherein, N represents the number of the input wavelength channels of the switch structure; P represents the number of optical buffer channels; wherein, Indicates a tunable wavelength converter, represents an optical delay line.

Figure 6. Schematic diagram of the burst switching structure capable of reducing the loss rate of the present invention. Among them, ￣￣￣￣￣￣￣￣indicates optical domain connection, ---------------indicates electrical domain connection

Figure 7 Schematic diagram of conflict resolution in the electrical domain

Among them, T represents the unit fixed delay of the optical delay line (FDL); ti1 represents the original arrival time of the i-th burst data; ti2 represents the original departure time of the i-th burst data; ti1' represents the i-th burst The arrival time of data after passing through the buffer; ti2' represents the departure time of the i-th burst data after passing through the buffer; Δt(Δt=t31'-t31) represents the minimum electrical domain delay for burst data to be sent without conflict.

表示突发控制分组到达时间，_________________表示光延迟线固定时延，■表示发生冲突的部分， 表示突发数据占用时间，

表示光延时后能无冲突发送

Indicates the arrival time of the burst control packet, _________________ indicates the fixed delay of the optical delay line, ■ indicates the part where the conflict occurs, Indicates the burst data occupation time,

Indicates that it can be sent without conflict after optical delay

Figure 8 is a schematic diagram of an embodiment of 100% no packet loss after the conflict

Figure 9 is a schematic diagram of an embodiment of partial non-packet loss after a conflict

Detailed ways

Embodiment 1, 100% no packet loss embodiment after conflict

As shown in Figure 8, we use a 32×32 non-internal blocking optical switch matrix; the input port has two input ports each with 8 wavelength channels, and a total of 16 input wavelength channels are used as signal input; the output port also has two output ports 8 wavelength channels each, a total of 16 output wavelength channels are used as the output of the signal. The difference from the input end is that the 16 wavelength converters can adjust the output signal to the required wavelength; the remaining 16 at the input end and the output end The wavelength channel, 16 photoelectric converters, 16 RAM buffers, and 16 electro-optic converters together form the electrical buffer part to provide 16 electrical buffer channels to resolve conflicts.

When the node starts to work, there is no data stored in the electrical cache, and all data is input from 16 input wavelength channels. The worst case of conflict at this time is that each of the 16 wavelength channels needs to send a burst of data at the same time, and all 16 data need to be sent to the same output wavelength channel. In this case, the way to resolve the conflict is to send one of the 16 data from the wavelength channel that needs to be output, and send the remaining 15 burst data to 15 different electrical buffer channels, and then select the appropriate one. The time is sent without conflict. Therefore, 16 input and output wavelength channels and 16 electrical buffer channels can guarantee no packet loss after 100% conflicts in the initial operation. But this is not the worst case of conflicts. The worst case is that there are 32 bursts of data to be sent at the same time in the 16 input wavelength channels and 16 electrical buffer channels at the input end of the switch matrix. According to the introduction of the optical burst switching system, we know that we have processed their corresponding BHP before the burst data arrives, that is to say, we know the conflict situation in advance. Therefore, the burst data sent by the 16 electrical buffer channels do not conflict with each other, that is to say, the burst data sent by the 16 electrical buffer channels are respectively sent to the 16 output wavelength channels, that is, there are bursts on all 16 output wavelength channels. Data needs to be sent. Then conflicts can only occur between the burst data sent by the 16 input wavelength channels and between the burst data sent by the input wavelength channel and the burst data sent by the electrical buffer. From the perspective of each output wavelength channel, when n bursts of data collide, we will select one of them to send, and send the remaining n-1 bursts to the buffer to delay the resolution of the conflict. Therefore, in the case that all 16 output wavelength channels have data, 16 burst data are sent out by the output wavelength channels, and 32-16=16 burst data are respectively sent to 16 electrical buffer channels for delay. In this way we can also provide 100% no packet loss after collision in the worst case. Of course, the question that still needs to be considered is whether the capacity of the cache can be infinitely large enough to hold all the burst data sent after the conflict; If the limit is too long, the upper layer protocol will think that the packet is lost and retransmit it if the cache time is too long. To sum up, under ideal conditions, if the number of electrical buffer channels M is equal to the total number of input and output wavelength channels N×n, the switching structure proposed in this patent can provide 100% protection against packet loss after collision.

Embodiment 2. An embodiment in which there is a certain loss rate after the conflict

In practical applications, if a certain degree of data loss rate is allowed, then the configuration in FIG. 9 can also achieve better cost performance. As shown in the figure, a 32×32 non-blocking optical switch matrix is still used; the input end has three input ports with 8 wavelength channels each, and a total of 24 input wavelength channels are used as signal input; the output end has three output ports with 8 wavelength channels each channels, a total of 24 output wavelength channels are used as signal output, and 24 wavelength converters can adjust the output signal to the required wavelength; the remaining 8 wavelength channels and 8 photoelectric converters at the input and output ends, 8 A RAM cache and 8 electrical-optical converters are combined to form the electrical cache part to provide 8 electrical cache channels to resolve conflicts. The additional 8 input and output wavelength channels can increase the input and output capabilities and support more business passing. The probability of the worst case of collision is very small, and 8 electrical buffer channels can provide better support for collision. That is to say, without changing the size of the switching matrix, a greater service transmission capacity can be obtained by sacrificing a little data loss rate. Because the cost of the high-speed optical switch matrix increases greatly with the increase of ports, this structure not only controls the cost, but also ensures the loss of performance.

Claims (3)

1. An opto-electronic hybrid switching fabric supporting optical burst/packet switching, comprising: an optical switching matrix, said optical switching matrix has (M + N × N) input ports and (M + N × N) output ports, M represents the number of buffer channels, N represents the number of input ports or output ports, N × N represents the number of input (output) wavelength channels, and N represents the number of wavelength channels included in each input port or output port; n input ports, N output ports, N wave splitters, N wave combiners and Nxn adjustable wavelength converters (TWC); the input port (1) decomposes n wavelength channels through a wave splitter, and the n wavelength channels are respectively connected to any n input ports of the optical switching matrix by using optical fibers; the input port (2) decomposes n wavelength channels through a wave splitter, and the n wavelength channels are respectively connected to any n input ports of the optical switching matrix by using optical fibers; the rest input ports are analogized in this way to form N input ports; all the input ports share N multiplied by N input ports of the optical switching matrix; corresponding to the input port (1), n wavelength channels output from n output ports of the optical switching matrix are connected to n adjustable wavelength converters through optical fibers, and each adjustable wavelength converter is connected to the combiner through the optical fibers to form the output port (1); corresponding to the input port (2), n wavelength channels output from n output ports of the optical switching matrix are connected to n adjustable wavelength converters through optical fibers, and each adjustable wavelength converter is connected to the combiner through the optical fibers to form the output port (2); the rest output ports are analogized in this way to form N output ports; all output ports share N multiplied by N output ports of the optical switching matrix;

it is characterized in that it also comprises:

the photoelectric converter, the RAM buffer and the photoelectric converter are connected in sequence through an electric domain to form a buffer channel, and M buffer channels are shared; the input end of each buffer channel is connected with the output port of the optical switching matrix through an optical fiber, and the output end of each buffer channel is connected with the input port of the optical switching matrix through an optical fiber.

2. An optical-electrical hybrid switching fabric supporting optical burst/packet switching as claimed in claim 1, wherein each input port of said optical switching matrix is connectable to only one channel.

3. An optical-electrical hybrid switching fabric supporting optical burst/packet switching as claimed in claim 1 wherein each output port of said optical switching matrix is connectable to only one channel.

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