JP2008153887A - Optical switch device and optical signal transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical switch device for which the load of a communication system for the switching control of the optical switch device constructing an optical network is small. <P>SOLUTION: Optical signals from an ONT 10 are switched and transferred to a plurality of OLTs 30 by the optical switch device 20. As a result, the communicating OLT 30 is connected in a time division manner and the OLT 30 without data to be communicated is completely disconnected. For switching, since a switching pattern is stored in a control memory inside the optical switch device 20 and the switching pattern is read to switch an optical switch, the need of controlling the optical switch device from the outside in synchronism with the changeover is eliminated and burdens on the system for executing control are small. Thus, it is possible to achieve an optical network using many optical switch devices. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical switch device and an optical signal transmission device suitable for use in an optical network, which can be applied to an access network such as FTTH (Fiber To The Home) which is now widely used.

  At present, the FTTH network has a network form called PON (Passive Optical Network). The PON draws one optical fiber into a plurality of subscriber homes by inserting a branching device called a star coupler (optical splitter) in the middle of the optical fiber network. This method is characterized in that it does not require an electrical device and is easy to install, and since it is not necessary to lay an optical fiber from the accommodation station for each user, an FTTH can be constructed economically.

  FIG. 16 is a diagram showing a schematic configuration of a conventional optical network. The optical network includes an optical network terminal (ONT) 10, a star coupler 200, and an optical line terminal (OLT). The star coupler 200 branches the optical signal from the optical network terminal 10 and transfers it to the n optical line terminals 30.

  However, since the optical signal power attenuates in proportion to the number of branches at each branch, the PON has a problem that the signal error rate increases as the number of branches increases. In addition, since all information is branched and delivered to the subscriber, and only the user's own information is selected on the subscriber side, the information of other users is physically delivered. There's a problem.

Therefore, the present inventors have proposed to switch an optical signal from a PC at a time interval set in advance by a control signal from the outside in one optical switch, and transfer it to a plurality of output port destination PCs. (See Non-Patent Document 1).
Teruo Kasahara, 5 others, “Optical Slot Switching (OSS) that performs dynamic path switching using PLZT ultra-high-speed optical switch”, IEICE Technical Report, March 9, 2006, 105, 667, p. 27-32 Keiichi Nashimoto, 8 others, "[Encouragement Talk] PLZT thin film waveguide type 1xN ultrafast optical switching subsystem", IEICE Technical Report, March 9, 2006, Vol. 105, No. 667, p. 21-26

  However, if all of the switching of high-speed optical switch devices that are frequently used in the construction of an optical network is controlled from the outside, the load on the communication system for the control will increase.

  In view of the above problems, an object of the present invention is to provide an optical switch device and an optical signal transmission device having a small communication system load for switching control of an optical switch device that constructs an optical network.

  The optical switch device of the present invention stores an optical switch that outputs a signal from one input optical communication path by switching to a plurality of output optical communication paths in units of a slot that is a predetermined time, and an input control signal. A control memory; and a control unit that reads the control signal from the control memory and switches the optical switch to a predetermined output optical communication path in units of slots.

  In addition, the control memory has a storage area corresponding to a plurality of frames with respect to a frame composed of slots of the number of time division multiplexed channels, so that it can be seamlessly switched to a new switching pattern of the optical switch.

  In addition, the control memory stores the number of slots for continuously selecting a predetermined output optical communication path, and the control unit continuously outputs a predetermined number of slots corresponding to the number of slots read from the control memory. By switching after selecting the output optical communication path, it is not necessary to end and start communication for each slot, and large-scale content such as a DVD can be distributed with high efficiency.

  The control memory does not need to provide a special control line for the optical switch device by inputting the control signal from the input optical communication path of the optical switch.

  The optical switch device according to the present invention includes an optical switch that switches a signal from one input optical communication path to a plurality of output optical communication paths in units of a slot that is a predetermined time, and outputs the signal from the input optical communication path. And a control unit that switches the optical switch using a signal having one or a plurality of predetermined wavelengths of the input frequency multiplexed signals as a control signal. This eliminates the need for a serial-parallel converter or the like in the optical switch device, thereby simplifying the configuration of the optical switch device.

  The optical signal transmitting apparatus of the present invention includes a queue that stores input packets for each destination and from which the packets of the destination are intensively read in a slot of a predetermined destination selected in the optical switch device. The packet read from the queue is transmitted to the optical switch device.

  According to the present invention, since the switching pattern is stored in advance in the memory in the optical switch device as a control signal and the optical switch is switched in accordance with the control signal, it is necessary to control the optical switch device from the outside in synchronization with the switching. And there is little burden on the system for control. Therefore, it is possible to realize an optical network using many optical switch devices.

  Further, by inputting a control signal from the input optical communication path of the optical switch, a special control line is not necessary, and the burden on the system for control is also reduced.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a diagram showing a schematic configuration of an optical network using an optical switch device according to a first embodiment of the present invention. The optical network according to the present invention comprises an optical network terminal (ONT) 10, an optical switch device 20, and an optical line terminal (OLT) 30, and the optical network terminal 10 and the optical switch device 20 are connected by some control line 40. Is done. The control line 40 will be described later. An optical signal from the optical network terminal 10 is selectively transferred to a predetermined optical line terminal 30 in the optical switch device 20.

  FIG. 2 is a time chart for explaining the operation of the optical switch device 20 according to the first embodiment. Here, an example is shown in which one frame is set to four slots for eight output ports # 0 to # 7, and the optical switch device 20 is switched repeatedly in units of frames. The frame consists of slots # 0 to # 3. In slot # 0, user A of output port # 0 is selected, in slot # 1, user C of output port # 3 is selected, and in slot # 2, the output port is selected. The user E of # 5 is selected, and the user F of the output port # 6 is selected in the slot # 3, and an optical signal is transferred to these output ports. For example, while the user A of the output port # 0 is selected in the slot # 0, the optical signal from the optical network terminal 10 is exclusively transferred to the user A of the output port # 0, and the other output port # 1 No optical signal is transferred to ~ # 7.

  FIG. 3 is a diagram illustrating the configuration of the optical switch device according to the first embodiment. The optical switch device according to the first embodiment includes an optical switch 21, a control memory 22, and a control unit 23. As the optical switch 21, for example, a 1 × N PLZT (an oxide compound of lead (Pb), lanthanum (La), zirconium (Zr), titanium (Ti)) optical switch can be used (for example, see Non-Patent Document 2). .) The control memory 22 stores an output port selected in each slot as a control signal input from the outside. The control unit 23 repeatedly reads out the control signal from the control memory 22 and switches the optical switch 21 for each slot. The control signal periodically polls all the optical line terminals 30 such as every 100 slots and accepts new communication requests, and takes into account the amount of data and the like based on the new communication requests and the current communication status. It can be created by determining the switching pattern.

  FIG. 4 is a diagram comparing the loss of Example 1 and the prior art. FIG. 4 shows the loss in the prior art using an optical splitter and the first embodiment using the 1 × 8 PLZT optical switch (denoted as the present invention), where the vertical axis represents loss (dB) and the horizontal axis represents the number of users N. In the prior art, the loss increases remarkably as the number of users N increases. In the first embodiment, the loss of one optical switch device is 6 dB or less (see Non-Patent Document 2), and the number of users exceeds 8. When the optical switch devices are connected and arranged in a tree shape with respect to the number, it can be seen that the expandability to the increase in the number of users is great.

  FIG. 5 is a time chart illustrating the operation of the optical switch device according to the second embodiment, and FIG. 6 is a diagram illustrating the configuration of the optical switch device according to the second embodiment. In the optical switch device 20 according to the second embodiment, the control memory 22 has a storage area for each frame. Then, while the control unit 23 reads the control signal and switches the optical switch 21, the control unit 23 writes a control signal of a new switching pattern in another storage area. In FIG. 5, in the storage areas of frame numbers 0 and 1, optical signals are transferred to users E, A, F, and D in slots # 0 to # 3. Assuming that the user C makes a communication request for 3 slots during this period and the communication amount of the user F is the frame number 1 and the communication is terminated, the frame number 2 is terminated before the frame number 1 is terminated. A control signal is written in the storage area so as to transfer the optical signal to the users E, A, C, and D. By doing so, it is possible to seamlessly switch to a new switching pattern of the optical switch 21. That is, there is no need to pause communication when switching to a new switching pattern. Further, if user B makes a communication request for two slots during this period and communication is terminated when user A's communication volume is frame number 2, storage of frame number 3 is completed before frame number 2 ends. A control signal is written in the area so as to transfer the optical signal to the users E, B, C, and D. Here, for simplicity of explanation, the control memory has a storage area corresponding to each frame. However, in that case, an infinite storage area is required, so in practice a storage corresponding to a plurality of frames is required. Needless to say, if there is a region, it can be used repeatedly. Therefore, if there is a storage area corresponding to at least two frames, the same operation can be realized by alternately using these for writing and reading.

  FIG. 7 is a time chart for explaining the operation of the optical switch device according to the third embodiment, and FIG. 8 is a diagram illustrating the configuration of the optical switch device according to the third embodiment. In the optical switch device 20 according to the third embodiment, the control memory 22 has a storage area for each output port, and has an area for storing the number of slots to be successively selected for each output port. Then, the control unit 23 switches the optical switch 21 so as to select the output port continuously for the number of slots. Here, output port # 0 (user A) is selected twice in succession, output port # 1 (user B) is selected five times in succession, and output port # 2 (user C) is selected in succession 2 An example of selecting the number of times is shown. As a result, when a predetermined output port is selected in succession for a plurality of slots, it is not necessary to end and start communication for each slot, and a large-scale content such as a DVD can be distributed with high efficiency. In addition, Example 2 and Example 3 can be implemented in combination. Specifically, the control memory 22 stores the number of continuously selected slots for each output port in units of frames. In this case, the number of continuously selected slots for each output port accumulated for the frame is the number of slots in the frame.

  FIG. 9 is a diagram illustrating the configuration of the optical signal transmission device according to the fourth embodiment. The optical signal transmission device according to the fourth embodiment includes a distribution device 11 and a queue 12. The distribution device 11 stores, for example, asynchronously transmitted Ethernet packets in the queue 12 for each destination. The queue 12 is provided for each destination, and reads and transmits the stored Ethernet packet for each destination in synchronization with the slot of the optical switch device. At that time, a guard time is provided at the slot cut as necessary. The Ethernet packet of the fourth embodiment may be a general packet. Thereby, the packets transmitted asynchronously can be concentrated and transmitted in the slots, and efficient communication can be realized.

  FIG. 10 is a time chart for explaining the operation of the optical switch device according to the fifth embodiment, and FIG. 11 is a diagram illustrating the configuration of the optical signal transmitting device according to the fifth embodiment. The optical signal transmission apparatus according to the fifth embodiment includes a queue 12, a RAM 13, a speed converter 14, and a multiplexer 15. In the fifth embodiment, the protocol is different for each slot. The queue 12 is the same as the queue 12 according to the fourth embodiment, stores an Ethernet packet of a predetermined destination, reads out and transmits the packet in synchronization with the slot. In this case, Ethernet packets having different speeds for each slot can be transmitted. The RAM 13 stores TDM (Time Division Multiplexing) data, and reads and transmits it at a faster speed than the storage. The speed converter 14 is for increasing the speed of the analog signal and transmitting it. The multiplexer 15 multiplexes and transmits signals from the queue 12, the RAM 13, and the speed converter 14. Since the present invention switches the optical communication path for each slot, a free protocol can be adopted in the selected optical communication path without being restricted by other slots. That is, a different protocol can be adopted for each destination.

  FIG. 12 is a diagram illustrating the configuration of the optical switch device according to the sixth embodiment. The optical switch device according to the sixth embodiment further includes a duplexer 25 in addition to the configuration of the optical switch device according to the first embodiment, and the control unit 23 includes a photoelectric converter 24. The demultiplexer 25 demultiplexes the light having the wavelength λo and the light having the wavelengths λ1 to λn. The photoelectric converter 24 converts the light with the wavelength λo into an electric signal to obtain a control signal. In the sixth embodiment, a control signal is sent from the optical network terminal (ONT) 10 to the optical switch device using one wavelength (λo in this example) of wavelength multiplexing via an optical fiber for communication. Thereby, it is not necessary to provide a special control line for the optical switch device.

  FIG. 13 is a diagram illustrating the configuration of the optical switch device according to the seventh embodiment, and FIG. 14 is a time chart illustrating the operation of the optical switch device according to the seventh embodiment. The configuration of the optical switch device of the seventh embodiment is basically the same as that of the sixth embodiment, but transmits one bit at one wavelength as a control signal. In the example shown in the figure, three bits for selecting eight routes (that is, output ports) are transmitted using λo to λ2. For example, when slot # 1, route 5 is selected as λo = 1, λ1 = 0, λ2 = 1, and when slot # 2, route 4 is selected as λo = 1, λ1 = 0, λ2 = 0. And so on. Thereby, since one wavelength is used for one bit, a serial-parallel converter or the like is not required for the optical switch device, and the configuration of the optical switch device can be simplified. When the optical switch device is configured in a multi-stage such as a tree shape, different wavelengths are assigned to the respective stages, the first stage λo to λ2, the second stage λ3 to λ5, the third stage λ6 to λ8, etc. It can be realized by using the wavelength.

  FIG. 15 is a diagram illustrating the configuration of the optical switch device according to the eighth embodiment. The optical switch device 20 according to the eighth embodiment further includes a duplexer 25, a photoelectric converter 26, and a battery 27 in addition to the configuration of the optical switch device according to the first embodiment. An optical network terminal (ONT) 10 is an optical switch that combines powerful light of a specific wavelength from an electro-optical converter 16 such as a laser or LED (Light Emitting Diode) with a communication wavelength by a multiplexer 17. Send to device 20. The optical switch device 20 demultiplexes the received light into a power wavelength and a communication wavelength by the demultiplexer 25, and the photoelectric converter 26 converts the light having the power wavelength into an electric signal. The battery 27 is charged, and the battery 27 supplies the charged power to the control unit 23. Thereby, it is not necessary to provide a special power line for the optical switch device.

  In addition, this invention is not limited to the said Example.

  Since the present invention switches the optical communication path by switching, communication is possible not only in one direction but in both directions in a communicable slot.

It is a figure which shows the structure outline | summary of the optical network which uses the optical switch apparatus by Example 1. FIG. 3 is a time chart illustrating the operation of the optical switch device 20 according to the first embodiment. It is a figure which shows the structure of the optical switch apparatus by Example 1. FIG. It is a figure which compares Example 1 and the loss of a prior art. 6 is a time chart for explaining the operation of the optical switch device according to the second embodiment. It is a figure which shows the structure of the optical switch apparatus by Example 2. FIG. 12 is a time chart for explaining the operation of the optical switch device according to the third embodiment. FIG. 6 is a diagram illustrating a configuration of an optical switch device according to a third embodiment. FIG. 10 is a diagram illustrating a configuration of an optical signal transmission device according to a fourth embodiment. 10 is a time chart for explaining the operation of the optical switch device according to the fifth embodiment. FIG. 10 is a diagram illustrating a configuration of an optical signal transmission device according to a fifth embodiment. FIG. 10 is a diagram illustrating a configuration of an optical switch device according to a sixth embodiment. FIG. 10 is a diagram illustrating a configuration of an optical switch device according to a seventh embodiment. 12 is a time chart for explaining the operation of the optical switch device according to the seventh embodiment. FIG. 10 is a diagram illustrating a configuration of an optical switch device according to an eighth embodiment. It is a figure which shows the structure outline | summary of the conventional optical network.

Explanation of symbols

10 Optical network terminal 11 Sorting device 12 Queue 13 RAM
DESCRIPTION OF SYMBOLS 14 Speed converter 15 Multiplexer 16 Electro-optical converter 17 Multiplexer 20 Optical switch apparatus 21 Optical switch 22 Control memory 23 Control part 24 Photoelectric converter 25 Demultiplexer 26 Photoelectric converter 27 Battery 30 Optical line terminal 40 Control Line 200 star coupler

Claims (7)

An optical switch that switches a signal from one input optical communication path to a plurality of output optical communication paths and outputs the signal from a slot that is a predetermined time as a unit;
A control memory for storing input control signals;
An optical switch device comprising: a control unit that reads the control signal from the control memory and switches the optical switch to a predetermined output optical communication path in slot units.   2. The optical switch device according to claim 1, wherein the control memory has a storage area corresponding to a plurality of frames for a frame composed of slots of the number of time division multiplexing channels. The control memory stores the number of slots for continuously selecting a predetermined output optical communication path,
3. The optical switch according to claim 1, wherein the control unit selects a predetermined output optical communication path continuously by the number of slots read from the control memory and then switches the optical output path. apparatus.   4. The optical switch device according to claim 1, wherein the control memory inputs the control signal from an input optical communication path of the optical switch. An optical switch that switches a signal from one input optical communication path to a plurality of output optical communication paths and outputs the signal from a slot that is a predetermined time as a unit;
An optical switch device comprising: a control unit that switches the optical switch using a signal having one or a plurality of predetermined wavelengths of frequency multiplexed signals input from the input optical communication path as a control signal.   6. The light according to claim 1, further comprising a power supply that supplies power by a signal having one or a plurality of predetermined wavelengths of frequency multiplexed signals input from the input optical communication path. Switch device. An input packet is stored for each destination, and the optical switch device according to claim 1, 2 or 3, comprising a queue from which the packets of the destination are read in a concentrated manner in a slot of a predetermined destination selected. An optical signal transmission device that transmits a packet read from the queue to the optical switch device.

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