JP3998510B2 - Optical switch device and control method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical switch device used in a wavelength division multiplexing optical transmission system and a control method thereof.
[0002]
[Prior art]
With the recent increase in information communication needs, there is an urgent need to expand the transmission capability of communication systems and to improve the management system. In a conventional communication system mainly composed of voice, it is sufficient if an end-to-end connection can be set by a switching network. On the other hand, in data-oriented communications such as the Internet and LAN (Local Area Network), services such as flexible change of line capacity and switching of transmission paths are indispensable.
[0003]
As a transmission system that can meet such a demand, a wavelength division multiplexing optical transmission system has attracted attention. Recently, a system has been proposed in which an optical transmission path is increased in capacity by DWDM (Dense Wavelength Division Multiplexing) and the path of each wavelength light is switched by an optical switch. In this type of system, an optical switch device that can switch the path of wavelength light as an optical signal is a key device. At present, there are known devices using light reflecting elements by bubbles, and two-dimensional (2D) or three-dimensional (3D) optical switch devices using MEMS (micro electro mechanical system) technology. ing.
[0004]
FIG. 12 is a diagram showing a schematic configuration of a conventional optical switch device. This optical switch device includes input ports I1 to I3, output ports O1 to O3, and a plurality of mirror elements formed on a substrate. Each mirror element is arranged in an array on the intersection of the extension line of the input ports I1 to I3 and the extension line of the output ports O1 to O3. Each mirror element takes two states, active or inactive. Each mirror element rises on the substrate in the active state and falls on the substrate in the inactive state.
[0005]
In the above configuration, the light path can be freely changed by individually controlling the active or inactive state of the mirror element.
[0006]
By the way, the above-described configuration has the following problems. That is, since each mirror element operates mechanically, it is inevitable that elastic vibration occurs. Particularly problematic is when the state changes from inactive to active. In such a case, since light is reflected by the vibrating mirror element, a sharp peak may occur in the output level. This type of waveform peak is called a glitch.
[0007]
FIG. 13 is a diagram for explaining the occurrence of glitches. In the figure, the vertical axis represents output light intensity (Po), and the horizontal axis represents time (t). As shown in FIG. 13A, when the mirror element is activated to connect the input light to the output port, a glitch occurs as a transient phenomenon. If the diameter of the output optical fiber connected to the output port is small, the fluctuation of the light output becomes very large even if the vibration is slight. As shown in FIG. 13B, when the mirror element is inactive and the output light is turned off, no glitch occurs.
[0008]
In many cases, an optical amplifier is connected to the output side of the optical switch device in order to compensate for a loss generated in the optical switch device. If light with a glitch is input, a surge (that is, a high-power optical pulse) may occur in the optical output of the optical amplifier. If an optical surge occurs, there is a risk of damaging the optical receiver circuit.
[0009]
In addition, due to the occurrence of glitches, there is a possibility that a false alarm is generated in the device that detects this. If a false alarm occurs, it may cause a malfunction of the monitoring control system that operates based on the false alarm, which is extremely undesirable in terms of network operation.
[0010]
[Problems to be solved by the invention]
As described above, the conventional optical switch device has a problem that an optical device connected in the subsequent stage may be damaged or a false alarm may occur due to the occurrence of a glitch.
[0011]
The present invention has been made under the circumstances described above, and an object thereof is to provide an optical switch device capable of preventing glitches and a control method therefor.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the present invention takes n (n is a natural number) input ports, m (m is a natural number) output ports, a light reflection state, or a light passage state. Xm light reflecting elements are arranged in a matrix, and the light reflecting elements are selectively reflected so that light from the input port is guided to an arbitrary output port. Light reflected by the optical switch unit that forms an arbitrary light propagation path between them and the light reflecting element that has changed from the light passing state to the light reflecting state, the light reflecting element passes the light from the light propagation path. And an optical gate means for blocking only for a specified period including a time point when the state changes from the state to the light reflection state.
[0013]
In such a configuration, a certain light reflecting element transitions from a light passing state (for example, inactive state) to a light reflecting state (for example, active state), reflects light from a certain input port, and outputs a certain amount. Suppose that it is in a state leading to a port. At this time, a glitch is generated immediately after the state is changed from the light passing state to the light reflecting state, but light reflection is performed by the optical gate means in a specified period including the time when the state is changed, preferably in the generation period of the glitch. Reflected light from the element is blocked.
[0014]
Therefore, light including glitches is not output, and from this, it is possible to prevent adverse effects on devices such as optical amplifiers connected in the subsequent stage.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0016]
FIG. 1 is a diagram showing a configuration of a wavelength division multiplexing optical transmission system according to an embodiment of the present invention. This system includes a plurality of optical transmission apparatuses (hereinafter referred to as nodes) Nodes A to D and optical transmission lines FL that connect the nodes A to D in a ring shape. The optical transmission line FL transmits wavelength multiplexed light in which optical signals of different wavelengths are wavelength multiplexed. Each of the nodes A to D is connected to a low-order group device X such as an exchange, separates an optical signal having a predetermined wavelength from the wavelength multiplexed light, and transmits the optical signal to the low-order group device X, and wavelength light from the low-order group device X. To the optical transmission line FL.
[0017]
The optical transmission line FL includes a circuit in the clockwise direction and a circuit in the counterclockwise direction. For convenience, the clockwise direction as viewed from each node is referred to as EAST, and the counterclockwise direction is referred to as WEST. For example, focusing on node A, the direction to node B is EAST and the direction to node D is WEST.
[0018]
FIG. 2 is a diagram illustrating the configuration of the node A in FIG. Nodes B to D have the same configuration. In FIG. 2, the node A includes wavelength multiplexing units 1011 and 1012, wavelength demultiplexing units 1010 and 1013, an optical switch unit 1030, and a control unit 1040. The wavelength multiplexing units 1011 and 1012 wavelength multiplex optical signals λ1 to λn having different wavelengths input from the optical switch unit 1030 and send them to the transmission line fibers 1002 and 1003, respectively. The wavelength demultiplexing units 1010 and 1013 demultiplex the wavelength multiplexed light introduced from the transmission line fibers 1001 and 1004 into optical signals λ1 to λn of individual wavelengths, respectively, and input them to the optical switch unit 1030.
[0019]
Optical signals λi, λj, and λk having predetermined wavelengths are introduced into the optical switch unit 1030 from a low-order group device X (not shown). The optical switch unit 1030 performs signal exchange connection in units of wavelengths. In other words, the optical switch unit 1030 exchanges the path of the optical signal input from the wavelength demultiplexing units 1010 and 1013 or the low-order group device X under the control of the control unit 1040, so that the wavelength multiplexing units 1011 and 1012 Send to group device X and the like.
[0020]
In the following description, the transmission line fiber 1001 is expressed as WEST IN, the transmission line fiber 1002 as WEST OUT, the transmission line fiber 1003 as EAST OUT, and the transmission line fiber 1004 as EAST IN. Further, the wavelength channels related to the low-order group device X are distinguished from each other by expressing them as LS1, LS2,..., LSm, and the signal interface related to these channels is called an LS (Low Speed) interface.
[0021]
FIG. 3 is a diagram illustrating a general configuration of the optical matrix switch. This optical matrix switch includes input ports 1a, 1b, 1c, and 1d, output ports 2a, 2b, 2c, and 2d, and mirror elements 3 arranged in a matrix in an optical propagation path between these ports. . The configuration shown in FIG. 3 is called a 4 × 4 scale, and 16 mirror elements 3 are provided.
[0022]
Each of the mirror elements 3 takes an active state or an inactive state. In the active state, the mirror element 3 reflects light arriving from the input port direction toward the output port direction. In the inactive state, the mirror element 3 does not reflect light but allows it to pass. Techniques such as MEMS and bubble are applied to realize the reflection function.
[0023]
The state of each mirror element 3 is individually controlled by the control unit 1040, and an arbitrary input port and an arbitrary output port are optically connected in response to a wavelength path setting request.
[0024]
FIG. 4 is a diagram illustrating a state of the mirror element 3 when the optical matrix switch of FIG. 3 is in the Add / Drop connection. The Add / Drop connection is a connection configuration in which an optical signal having an arbitrary wavelength input from a transmission line fiber is connected to the LS interface, and an optical signal having an arbitrary wavelength input from the LS interface is connected to the transmission line fiber. . In FIG. 4, it is assumed that WEST IN is connected to LS1 OUT, EAST IN is connected to LS2 OUT, LS1 IN is connected to WEST OUT, and LS2 IN is connected to EAST OUT.
[0025]
To realize this state, a mirror element on a lattice point connecting the input port 1a and the output port 2c, a mirror element on a lattice point connecting the input port 1b and the output port 2d, and the input port 1c and the output port 2a Only the mirror element on the lattice point connecting the two and the mirror element on the lattice point connecting the input port 1d and the output port 2b are made active. As a result, the ports are optically connected, and an Add / Drop connection is realized.
[0026]
FIG. 5 is a diagram showing a state of the mirror element 3 when the optical matrix switch of FIG. 3 is set to pass-through connection. The pass-through connection is a connection form in which an optical signal input from the WEST is output to the EAST side, and an optical signal input from the EAST side is output to the WEST side. That is, WEST IN is connected to EAST OUT, and EAST IN is connected to WEST OUT.
[0027]
In order to realize this state, only the mirror element on the lattice point connecting the input port 1a and the output port 2b and the mirror element on the lattice point connecting the input port 1b and the output port 2a are activated. . As a result, the ports are optically connected, and pass-through connection is realized.
[0028]
FIG. 6 is a diagram showing a configuration in the embodiment of the optical switch device according to the present invention. The optical switch device of FIG. 6 includes input ports 1-1 to 1-n, output ports 2-1 to 2-m, n × m mirror elements 3, and m sub-mirror elements 4.
[0029]
The sub mirror element 4 is formed on each of the output ports 2-1 to 2-m on a common substrate (not shown) with the mirror element 3. The sub mirror element 4 is preferably formed as an optical device having the same form as the mirror element 3. That is, the sub-mirror element 4 is preferably formed as a part of an (n + 1) × m scale optical matrix switch. In this way, the manufacturing process can be simplified.
[0030]
The sub mirror element 4 blocks the optical signal reflected by the mirror element 3 and going to one of the output ports 2-1 to 2-m for a certain period, and its operation timing is controlled by the control unit 1040. Is done.
[0031]
FIG. 7 is a schematic diagram showing how the optical switch device of FIG. 6 operates. As shown in FIG. 7A, in order to connect an optical signal (here, an optical signal input from the input port 1-n) to the output port 2-m, first, the output port 2-m is connected. The corresponding secondary mirror element 4 is activated. As a result, an optical signal directed to the output port 2-m is reflected in a direction other than the output port 2-m. In other words, even if light is directed toward the output port 2-m, this light is blocked in the state of FIG.
[0032]
Next, as shown in FIG. 7B, the mirror element 3 located at the intersection of the input port 1-n and the output port 2-m is activated, and the optical signal from the input port 1-n is output to the output port 2. Lead to -m. At this moment, a glitch occurs. However, since the optical signal is blocked by the sub mirror element 4, the optical signal accompanied by the glitch is not output.
[0033]
Then, as shown in FIG. 7C, when the elastic vibration of the mirror element 3 ends and a stable light output can be obtained, the sub mirror element 4 is made inactive. As a result, the input port 1-n and the output port 2-m are optically connected, and an optical signal input from the input port 1-n is output from the output port 2-m.
[0034]
As a property of the sub mirror element 4, no glitch occurs when the sub mirror element 4 changes from active to inactive. Accordingly, the optical signal input from the input port 1-n can be output from the output port 2-m without any glitch.
[0035]
FIG. 8 is a flowchart showing an operation procedure of the optical switch device of FIG. In order to connect an optical signal from an arbitrary input port to an arbitrary output port, first, in step S1 of FIG. 8, at least the secondary mirror element 4 corresponding to the output port to which the optical signal is to be connected is activated. . From this state, in the next step S2, the mirror element 3 located at the intersection of the desired input / output ports is activated. Thus, in step S3, the sub-mirror element 4 is made inactive after a predetermined time has elapsed until the vibration of the mirror element 3 is settled.
[0036]
As described above, in the present embodiment, the mirror elements 3 arranged in a matrix are individually controlled to be active or inactive to connect the optical signal from the input port to an arbitrary output port. A sub-mirror element 4 is provided for each output port. When the mirror element 3 is changed from inactive to active, at least the secondary mirror element 4 belonging to at least the same column is made active to block the reflected light of the mirror element 3. Then, after a period in which glitches are generated in the reflected light of the mirror element 3, the sub mirror element 4 is made inactive to pass an optical signal so that the input port and the output port are optically connected. Yes.
[0037]
Thus, while the glitch is generated in the optical signal reflected from the mirror element 3, the optical signal is blocked by the sub mirror element 4. Further, by changing the sub mirror element 4 from active to inactive, the optical signal is connected to the output port. For these reasons, glitches can be prevented.
[0038]
For these reasons, the following advantages can be obtained when the optical switch device according to the present embodiment is applied to an optical transmission device, an optical cross-connect device, or the like. That is, in an optical transmission apparatus or the like, optical amplifiers for compensating for a loss generated in an optical switch apparatus or the like are installed everywhere. Since the glitch can be suppressed according to the optical switch device of this embodiment, it is possible to prevent a surge from occurring in the optical output of the optical amplifier. Further, it is possible to prevent a false alarm from being detected in a device such as an optical transmission device or an optical cross-connect device, or in a low-order group device X connected to the outside.
[0039]
(Modification)
Next, modifications of the present invention will be described.
[0040]
In recent years, the number of input / output ports provided in an optical switch device is increasing. In order to incorporate and use such an optical switch device in an optical transmission device, the normality of the connection between the input / output port of the optical switch device and each port of the optical transmission device, the mirror element of the optical switch device itself, and each input In short, it is important to confirm the normality of the internal wiring in the optical transmission device before operation, such as the normality of the positional relationship with the output port.
[0041]
Incidentally, as shown in FIG. 12, in the conventional optical switch device, when all mirror elements are inactive, light is output from the output port no matter how light is input from the input port. Absent. Therefore, if all the mirror elements are inactive when the optical transmission apparatus is started up, it is impossible to confirm the normality of the internal wiring.
[0042]
On the other hand, if the optical transmission device is started with some mirror elements active, light will be output from the unexpected output port until the original switching setting is completed. This is extremely undesirable from the aspect. Furthermore, even if the normal operation state is reached, if any output port is unused, that is, if there is an output port that does not output light, the normality of the port cannot be confirmed.
[0043]
For this reason, when using a conventional optical switch device, the internal wiring is removed, the light source is connected to each line, and the optical power at the receiving end is checked in advance. There must be. Such an operation is desirably performed for all the wirings, and therefore the operation for that purpose is extremely complicated. Moreover, in recent years, the scale of the optical switch device has been remarkably increased, and therefore the wiring confirmation work has to become more complicated.
[0044]
Therefore, in this modification, an optical switch device capable of easily confirming the normality of the wiring inside the device is disclosed.
[0045]
FIG. 9 is a block diagram showing a configuration of an optical switch device according to a modification of the present invention. In FIG. 9, parts common to FIG. 6 are given the same reference numerals, and only different parts will be described here.
[0046]
The optical switch device shown in FIG. 9 includes a reference light source 10 in addition to the n × m mirror element 3. The mirror elements 3 are arranged in a matrix of n rows and m columns at the intersections of the input ports 1-1 to 1-n and the output ports 2-1 to 2-m. The active state or inactive state of each mirror element 3 is individually controlled, and an arbitrary input port and output port are connected. The reference light source 10 generates m systems of reference lights L1 to Lm.
[0047]
The reference lights L1 to Lm may be obtained by branching light emitted from the same light source into m systems. Or a wavelength, a modulation signal, etc. may differ for every reference light L1-Lm.
[0048]
Each of the reference lights L1 to Lm is irradiated to the output ports 2-1 to 2-m through n mirror elements 3, respectively. That is, if any of the mirror elements 3 that pass through is inactive, the reference light is transmitted transparently from the output port. On the other hand, if there is at least one active mirror element 3 in the path, the reference light is blocked and does not reach the output port.
[0049]
FIG. 10 is a schematic diagram showing an initial state of the optical switch device of FIG. Here, a 4 × 4 scale optical matrix switch having four input ports and four output ports is taken as an example.
[0050]
In the so-called initial state, such as when the apparatus is started up, the mirror elements 3 are often all inactive. In such a case, the reference light is output from all the output ports 2-1 to 2-m, that is, WEST OUT, EAST OUT, LS1 OUT, and LS2 OUT.
[0051]
FIG. 11 is a schematic diagram showing a state where the optical switch device of FIG. 9 is in pass-through connection. In this case, an optical signal input from WEST IN is output from EAST OUT, and an optical signal input from EAST IN is output from WEST OUT. Reference light is output from LS1 OUT and LS2 OUT.
[0052]
In summary, in this modification, the reference light generated by the reference light source 10 is transparently output from the output port of the column in which all the mirror elements 3 are inactive. Therefore, when the optical transmission device is started up or when the switching state of the optical switch device is not set, the reference light is output from the optical switch device. Accordingly, it is possible to check the normality of the connection from the optical switch device itself and the output port of the optical switch device to another function. Therefore, the normality of the wiring inside the apparatus can be easily confirmed.
[0053]
More specifically, in the optical switch device according to the present modification, reference light is output from the optical switch device even when all the mirror elements 3 are activated in an inactive state. Therefore, the normality of the function of the optical switch device and the normality of the signal connection state from the output ports 2-1 to 2-m of the optical switch device to, for example, the low-order group device X or the LS interface can be confirmed. .
[0054]
Further, according to the optical switch device of this modification, there is no problem even if all the mirror elements 3 are inactive and the device is started up. Thereby, it is possible to prevent a so-called erroneous connection state (misconnection) in which the transmission optical signal input to the apparatus is output in an unexpected direction.
[0055]
Further, according to the optical switch device of the present modification, an optical signal is output from the output port even when there is an output port to which the transmission optical signal is not connected. Therefore, it is possible to confirm the normality of the optical switch device and the normality of the signal connection state from the output ports 2-1 to 2-m of the optical switch device to, for example, the low-order group device X or the LS interface. For these reasons, it is possible to provide an optical switch device capable of easily confirming the normality of the wiring inside the device.
[0056]
Further, according to the optical switch device of this modification, the input optical signal is branched in order to check the normality of the wiring inside the device, and the branched light is input to the output port to which the transmission optical signal is not connected. There is no need to take measures. Thereby, attenuation of the optical signal can be minimized.
[0057]
Furthermore, according to the optical switch device of this modification, the optical signal from the optical switch device can be constantly output stably. For this reason, it is possible to prevent an optical surge from occurring in the optical output of the optical amplifier connected to the subsequent stage of the optical switch device.
[0058]
The present invention is not limited to the above embodiment. For example, in the embodiment, the sub mirror element 4 is formed on the same substrate as the mirror element 3. Not limited to this, the secondary mirror element 4 may be connected in a retrofit manner. That is, a new row of the sub mirror elements 4 may be added to the existing optical matrix switch. In this way, existing resources can be used effectively. Further, an optical gate element or the like that collectively blocks the output light of each column may be used without providing the sub mirror element 4 individually for each of the output ports 2-1 to 2-m.
[0059]
In addition, various modifications can be made without departing from the scope of the present invention.
[0060]
【The invention's effect】
As described above in detail, according to the present invention, an optical switch device capable of preventing glitches and a control method thereof can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a wavelength division multiplexing optical transmission system according to an embodiment of the present invention.
FIG. 2 is a diagram showing a configuration of nodes A to D shown in FIG. 1;
FIG. 3 is a diagram showing a general configuration of an optical matrix switch.
4 is a diagram showing a state of the mirror element 3 when the optical matrix switch of FIG. 3 is in Add / Drop connection. FIG.
FIG. 5 is a diagram showing a state of the mirror element 3 when the optical matrix switch of FIG. 3 is in a pass-through connection.
FIG. 6 is a diagram showing a configuration in an embodiment of an optical switch device according to the present invention.
7 is a schematic diagram showing how the optical switch device of FIG. 6 operates.
FIG. 8 is a flowchart showing an operation procedure of the optical switch device of FIG. 6;
FIG. 9 is a diagram showing a configuration of an optical switch device according to a modification of the present invention.
10 is a schematic diagram showing an initial state of the optical switch device of FIG. 9. FIG.
FIG. 11 is a schematic diagram showing a state where the optical switch device of FIG. 9 is in pass-through connection.
FIG. 12 is a diagram showing a schematic configuration of a conventional optical switch device.
FIG. 13 is a diagram for explaining a glitch.
[Explanation of symbols]
1-1 to 1-n ... input ports 2-1 to 2-m ... output ports A to D ... optical transmission device FL ... optical transmission path X ... low-order group devices L1 to Lm ... reference light 3 ... mirror element 4 ... Sub-mirror element 10... Reference light source 1001 to 1004... Transmission line fiber 1010, 1013... Wavelength separator 1011, 1012.

Claims (3)

n (n is a natural number) input ports;
m (m is a natural number) output ports;
N × m light reflecting elements that take either the light reflecting state or the light passing state are arranged in a matrix, and the light reflecting element is selected so that light from the input port is guided to an arbitrary output port. An optical switch unit that forms an arbitrary optical propagation path between the input port and the output port,
The light reflected by the light reflecting element that has changed from the light passing state to the light reflecting state, only for a specified period including the time when the light reflecting element changes from the light passing state to the light reflecting state from the light propagation path. A light gate means for blocking,
The optical gate means includes m sub-light reflecting elements provided for each of the output ports, which blocks the light by reflecting the light in a direction other than the propagation path direction. An optical switch device. Wherein n × A m-number of light-reflecting elements and the m sub-light reflecting device, optical switching device according to claim 2, characterized in that formed on a common substrate. A matrix of n (m is a natural number) input ports, m (m is a natural number) output ports, and n × m light reflecting elements that take either a light reflecting state or a light passing state Light that is disposed and selectively forms a light reflecting element so that light from the input port is guided to an arbitrary output port, thereby forming an arbitrary light propagation path between the input port and the output port. A control method of an optical switch device comprising a switch unit,
A first light path for blocking a light propagation path of light output through an output port connected to a light reflecting element to be changed from the light passing state to the light reflecting state before the state of the light reflecting element changes . Steps,
The state of the light reflecting element and a second step of changing the light reflecting state of the light passing state in a state where the light propagation path is blocked by the first step,
Characterized by comprising the this with the state of the light reflecting element is changed to after the elapse of the prescribed period from the second step, a third step of re-connecting the optical propagation path is blocked in advance the first step A control method of the optical switch device.

Images