JP4050661B2 - Optical cross-connect device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a small-scale / medium-scale optical cross-connect device used for optical path switching in the metro area or the like in the optical communication field, and more particularly to an optical cross-connect device capable of improving yield and reducing manufacturing cost.
[0002]
[Prior art]
In recent years, with the spread of TCP / IP networks, Ethernet (registered trademark) technology stipulated in IEEE 802.3 is used not only for short-distance LANs in the floor but also for medium-distance transmission from several kilometers to several tens of kilometers. Has been.
[0003]
For example, in the 10 gigabit Ethernet standard of IEEE Standard 802.3ae, the physical layer for WAN is defined, and in the case of 10 GBASE-EW, a 10-Gbps signal is transmitted using a single mode optical fiber of 1.55 μm band for about 40 km. It is possible. Similarly, the fiber channel technology can transmit a signal of 1 Gbps by about 10 km using a single mode optical fiber.
[0004]
In such a transmission form, an optical cross-connect device provided with an M × N matrix type optical switch capable of switching signal light at high speed is used for optical path switching.
[0005]
FIG. 2 is a configuration diagram showing an outline of a general M × N optical cross-connect device. This optical cross-connect device 101 includes M optical input ports 1, 2,... M, N optical output ports 1, 2,... N, and M × N MEMS mirrors. The optical input ports 1, 2,... M are connected to the input terminal of the M × N matrix type optical switch 103 at least including a × N matrix type optical switch 103 and a control unit 102 that controls driving of the MEMS mirror. The optical output ports 1, 2,... N are connected to the output terminals. A control communication input / output port is connected to the M × N matrix type optical switch 103 via the control unit 102.
[0006]
In such an optical cross-connect device 101, when an optical path switching signal including a MEMS mirror switching instruction is input from the control communication input / output port, the control unit 102 extracts a MEMS mirror number from the optical path switching signal. Then, a drive control signal is sent to the extracted MEMS mirror. Thus, when the drive of the MEMS mirror is turned on, the optical path between the designated input port and the output port is established, so that the signal light input from the designated input port is output from the target output port.
[0007]
Actually, in addition to such a configuration of the optical cross-connect device 101, failure detection / failure analysis during network operation, addition of various monitoring mechanisms for the purpose of redundancy, and contrivance of the optical switch configuration have been made.
[0008]
By the way, in the input port and output port of the optical cross-connect device 101 described above, two single-fiber optical connectors or two-fiber optical connectors are generally mounted as transmission / reception optical connectors. FIG. 3 is a diagram showing a configuration of a two-core SC optical connector 106 which is a typical example of the transmission / reception optical connector. Instead of the two-fiber SC type optical connector, an optical transceiver disclosed in Japanese Patent Laid-Open No. 2002-139659 that can perform bidirectional communication with one optical fiber can also be realized.
[0009]
Returning to FIG. 3, specifically, the SC-type two-fiber optical connector 106 is composed of a receptacle 106a and a plug 106b. The receptacle 106a is mounted on the optical cross-connect device side, and the plug 106b is connected to the station side device or the transmission line. It is mounted at the tip of the installed optical fiber. The receptacle 106a and the plug 106b have a pair of transmission / reception paths inside, and a pair of transmission / reception can be performed by fitting the plug 106b to the receptacle 106a.
[0010]
As described above, since the input / output optical fibers are generally used in a pair of transmission and reception, the input port (M) and the output port (N) are M = N. Then, the M × N matrix type optical switch 103 can be rewritten as an N × N matrix type optical switch. In the M × N matrix type optical switch or the N × N matrix type optical switch, connection from the transmission path 1 to the transmission path 2 or from the station side apparatus 1 to the station side apparatus 2 is possible. The connection to the path 2 or the connection from the station side apparatus 1 to the station side apparatus 2 is not necessarily required, and it is practically possible to connect any station side apparatus to any transmission path. Very many. In such a case, the N × N matrix type optical switch is further expressed by using two small J × J matrix type optical switches such as J × J using the relational expression of J = N / 2. Can do.
[0011]
Therefore, the SC type two-fiber connector shown in FIG. 3 is applied to the optical cross-connect device 101 shown in FIG. 2, and the route is divided into a station side device and a transmission line, and further replaced by a J × J matrix. When replaced with a type optical switch, it is as shown in FIG.
[0012]
In general, a (N / 2) × (N / 2) matrix type optical switch is ¼ the size of an N × N matrix type optical switch, and thus such an optical cross-connect device is configured at a low cost. There is an advantage that you can.
[0013]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-27975 [0014]
[Patent Document 2]
[Patent Document 1] Japanese Patent Laid-Open No. 10-200209
[Patent Document 3]
JP-A-11-27208 [0016]
[Patent Document 4]
Japanese Patent Laid-Open No. 11-41173 [0017]
[Patent Document 5]
JP 2002-139659 A
[Problems to be solved by the invention]
As described above, optical communication has become widespread in Ethernet / Gigabit Ethernet, etc., which is a communication method for LAN in recent years, not only in LANs in buildings and offices, but also in medium distance MANs of several kilometers to several tens of kilometers. However, these technologies are increasingly being applied. Against this background, there is a demand for an inexpensive optical cross-connect device that can be used appropriately in these inexpensive communication systems.
[0019]
However, in the configuration of FIG. 4, the optical cross-connect device is still expensive, so further cost reduction is expected.
[0020]
Therefore, the present invention has been made in view of the above problems, and the object of the present invention is sufficient for bidirectional communication at the same wavelength by eliminating optical noise caused by reflection using a low-reflection optical component. An object of the present invention is to provide an inexpensive optical cross-connect device while ensuring crosstalk characteristics.
[0021]
[Means for Solving the Problems]
The invention described in claim 1 is a J × J matrix type optical switch having J optical input ports and J optical output ports, and 2J pieces connected to input terminals of the J × J matrix type optical switch. It comprises at least an input port, 2J output ports connected to the output terminal of the J × J matrix type optical switch, and control means for switching control of the switching means, and the signal light input from a certain input port is predetermined. An optical cross-connect device that outputs to a plurality of output ports, wherein each pair of input / output ports is composed of one input port of the input ports and one output port of the output ports. the connector or 2-core optical connector is provided, between the optical connector and J × J matrix type optical switch, we have a output of one to the input of two and two single-mode optical fiber The 1 × 2 optical coupler formed by fusing and extending insert disposed inside the optical wiring and the single-mode optical fiber, is summarized in that two-way communication by light of the same wavelength.
[0022]
The invention according to claim 2 is the optical cross-connect device according to claim 1, wherein all of the reflections of the optical connector, the 1 × 2 optical coupler, and the J × J matrix type optical switch are combined. The gist of the present invention is that the return loss of the optical path is 40 dB or more.
[0023]
According to a third aspect of the present invention, in the optical cross-connect device according to the first aspect, each of the optical cross-connect devices including all the reflections of the optical connector, the 1 × 2 optical coupler, and the J × J matrix type optical switch is combined. The gist of the present invention is that the return loss for the optical path is 45 dB or more.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0028]
FIG. 1 is a diagram showing a configuration of an optical cross-connect device 1 according to an embodiment of the present invention.
The optical cross-connect device 1 of the present invention includes J station side input / output ports 1, 2,... J connected to the station side devices 1, 2,. J transmission line input / output ports 1, 2,... J connected to J, a Y-type 1 × 2 optical coupler 4 and a 1 × 2 optical coupler 4 arranged for each input / output port Connected to the J × J matrix type optical switch 3, the J × J matrix type optical switch 3 and the control unit 2 for controlling these functional units, and the control unit 2 to connect to the J × J matrix type optical switch. At least a control communication input / output port.
[0029]
Compared with the conventional optical cross-connect device 101, this optical cross-connect device 1 includes a 1 × 2 optical coupler 4 between the station side device input / output ports 1, 2,... J and the J × J matrix type optical switch 3. Is different from the transmission line input / output ports 1, 2,... J and the J × J matrix type optical switch 3 in that the 1 × 2 optical coupler 4 is disposed.
[0030]
An important point in realizing the optical cross-connect device 1 is how to prevent the deterioration of the crosstalk. For example, when establishing the path between the station side device 1 and the transmission path 3, ideally, after turning on the driving of the MEMS mirror included in the J × J matrix type optical switch 3, it is ideally connected to the reception port of the station side device 1. Between the two paths so that only the signal light input from the transmission port of the transmission path 3 arrives and only the signal light input from the transmission port of the station side apparatus 1 reaches the reception port of the transmission path 3. It is desirable that no crosstalk occurs.
[0031]
However, light from other paths may actually enter each receiving port, and in such devices with high optical noise (ie, devices with poor crosstalk characteristics), communication errors frequently occur and are practical. Can no longer be used.
[0032]
In many cases, the main cause of optical noise is light emitted from a transmission port paired with a reception port. For example, not all of the optical signals incident from the transmission port of the station side device 1 can reach the reception port of the transmission path 3, and those reflected by various parts are returned although they are only a part in intensity. Thus, the reception port of the station side device 1 is reached. The reflection is, for example, a connection portion between the 1 × 2 optical coupler 4 and the wiring or a connection portion between the wiring and the input terminal of the J × J matrix type optical switch.
[0033]
In a conventional system that performs two-way communication with a single core, in many cases, different wavelengths are used in the upstream and downstream directions to improve crosstalk characteristics, and a wavelength filter is inserted to reflect desired optical signals. The idea of discriminating from the optical noise caused by the problem was implemented.
[0034]
However, in order to obtain such a configuration, it is necessary to always use a device including a light source having an upstream wavelength and a device having a light source having a downstream wavelength, and the versatility is poor.
[0035]
In particular, when it is desired to apply an inexpensive Ethernet device, which has been rapidly spread in recent years, to both sides, such an optical cross-connect device is not suitable.
[0036]
In Japanese Patent Laid-Open No. 2002-139659, a multi-core Y-shaped light distribution element is used to prevent reflected light from the light emitting element from reaching the light receiving element.
[0037]
However, in such a configuration, even though it is possible to prevent the reflection at the end face of the connector on the near side, the reflection at the end face of the mating connector cannot be sufficiently prevented. In fact, Japanese Patent Laid-Open No. 2002-139659 In the example of the publication, there is an optical noise intensity of -39.6 dBm with respect to the emitted light intensity of -14.0 dBm, and the return loss is only about 25.6 dB.
[0038]
This is a numerical value that cannot be said to be a sufficient return loss depending on the application. For example, in a medium range device having a dynamic range, that is, an allowable transmission line loss width of 27 dB, the optical noise intensity caused by reflection is considered to exceed the sensitivity of the light receiving element. This method is basically for a communication system using a multimode optical fiber having a large core diameter, and cannot be applied to a single mode optical fiber as it is.
[0039]
Therefore, in the present invention, as the J × J matrix type optical switch 3, a 4 × 4 two-dimensional MEMS matrix type optical switch having a return loss of 50 dB or more is used.
[0040]
The 1 × 2 optical coupler 4 is a 4 × 4 fixed optical coupler formed by melting and stretching two single mode optical fibers, and one of the two output ends that is not used is The non-reflection termination process is performed so that the return loss is 50 dB or more.
[0041]
Furthermore, all the optical wiring inside the optical cross-connect device 1 is a normal single mode optical fiber.
[0042]
Furthermore, the optical adapter uses a double SC type optical adapter, and the optical connector in the optical cross-connect device 1 is a physical contact type (ultra PC polishing) that achieves a return loss of 50 dB or more by setting appropriate polishing conditions. SC type optical connector (hereinafter referred to as UPC polishing) or advanced PC polishing).
[0043]
Next, operations and effects of the optical cross-connect device 1 having the above-described configuration will be described.
[0044]
First, when the control unit 2 built in the optical cross-connect device 1 acquires an optical path switching signal including a MEMS mirror switching instruction via the control communication input / output port, the MEMS mirror number is extracted from the optical path switching signal. Then, a drive control signal is sent to the MEMS mirror. When the MEMS mirror switch is turned on by the drive control signal, an optical path between the designated input port and the designated output port is established.
[0045]
After the optical path is established, the signal light input from the specified optical input port is input to the J × J matrix type optical switch via the 1 × 2 optical coupler 4 and reflected by the specified MEMS mirror, and then the specified optical output. Output from the port.
[0046]
That is, for example, when a MEMS mirror switching signal for connecting the station side device 1 and the transmission path 3 is input via the control communication input port, the control unit 2 extracts a specified MEMS mirror number from this signal, A drive control signal is sent to the MEMS mirror. As a result, when the MEMS mirror switch is turned on, connection between both the transmission / reception paths (upward and downstream directions) between the station apparatus 1 and the transmission path 3 is established.
[0047]
Here, when signal light is input from the input port of the station side device 1, it is input to the J × J matrix type optical switch via the 1 × 2 optical coupler 4 and reflected by the switched MEMS mirror, and then the transmission path. 3 output ports. Similarly, when signal light is input from the input port of the transmission line 3, it passes through the 1 × 2 optical coupler 4 and is output to the output port of the station side device 1 via the J × J matrix type optical switch 3. Is done.
[0048]
Therefore, according to the present embodiment, it is possible to realize a device that essentially eliminates optical noise caused by reflection by adopting low-reflection components for each component constituting the optical cross-connect device 1. Therefore, sufficient crosstalk characteristics can be ensured even when bidirectional communication is performed at the same wavelength.
[0049]
Next, the optical characteristic measurement result of such an optical cross-connect device 1 will be shown.
[0050]
In this measurement, the remaining 15 ports other than the measurement target port are non-reflective terminations in which a coreless optical fiber is fused to the end of a normal single mode optical fiber in which a UPC polished SC optical connector with a return loss of 50 dB or more is connected. Connected, and measured.
[0051]
Under the above measurement conditions, the optical characteristics of the optical cross-connect device 1 were measured. As a result, a total of four input / output port connections of the station side devices 1, 2, 3, 4 and the transmission paths 1, 2, 3, 4 The total return loss of the total of 16 input / output optical ports comprising a total of 4 input / output port connections is 1.31 μm and 1.55 μm band C-Band / L-Band. Was 46 to 50 dB.
[0052]
If the return loss is 46 dB, for example, even if the incident light intensity from the output (transmission) port is −3 dBm, the optical noise due to reflection reaching the input (reception) port is −49 dBm, Because it is small enough, it does not matter. Note that -3 dBm here is IEEE Standard. 1000 BASE-LX Average launch power (max) defined in 802.3.
[0053]
Next, a result obtained by actually connecting a station-side device to the optical cross-connect device 1 having the optical characteristics and using it for bidirectional communication at the same wavelength is shown.
[0054]
A media converter device with a built-in 1000BASE-LX port was used as the station side device. When the transmission port of the 1000BASE-LX port of the station side apparatus was directly connected to the optical power meter with a short patch cord, the transmitted light intensity was -7.0 dBm. This was connected to the optical cross-connect device 1 as the station-side device 1. Next, an instruction was given to the optical cross-connect device 1 via the control communication input / output port so as to establish an optical path between the station-side device 1 and the transmission line 1, and the optical path was established.
[0055]
In this state, when the output port for the transmission line 1 is directly connected to the optical power meter with a short patch cord and the transmitted light intensity is measured, it is −14.3 dBm, and the optical cross-connect device 1 is inserted in this path. The loss was 7.3 dB.
[0056]
Next, when a reflection-free terminator was connected to each of the input / output ports for the transmission line 1 and the reflected light reaching the reception port of the station side device 1 was measured, it was -57.4 dBm. Therefore, when a media converter having an allowable transmission line loss of 27 dB is used, a transmission line loss of about 20 dB can be allowed in view of the insertion loss of the optical cross-connect device 1. It was confirmed that the ratio of light to optical noise due to reflection was sufficiently large at 23 dB. Actually, a 20 dB fixed optical attenuator is used instead of the transmission line, and another media converter device with a built-in 1000BASE-LX port can be connected to the input / output port for transmission line 1 through this to communicate normally. It was confirmed.
[0057]
Subsequently, in order to confirm the influence of the reflected light generated in the transmission / reception circuit of the station side device or the device connected to the end of the transmission line, the fixed optical attenuator is removed and the two units are connected to the input / output port for the transmission line 1. The eye device was connected directly with a short patch cord. The transmission / reception circuit of the 1000BASE-LX port of the device sufficiently satisfies the standard, but the reflection is larger than that of the optical cross-connect device 1. With this configuration, the light emission of the transmission port of the device on the transmission line 1 side was stopped, and the reflected light reaching the reception port of the station side device 1 was measured to be -33.7 dBm. At this time, the ratio between the signal light and the optical noise caused by the reflection was sufficiently large as 19 dB, and it was confirmed that the two devices could actually communicate normally.
[0058]
From the above experiments, if the return loss of the optical cross-connect device 1 is sufficiently large, it is possible to construct an optical communication system that eliminates optical noise caused by reflection, and performs bidirectional communication at the same wavelength. It was also shown that sufficient crosstalk characteristics can be secured.
[0059]
Here, there is a problem of how much return loss is required. However, in the medium-range Ethernet optical media converters and the like, a transmission line having an allowable loss width of about 30 dB is commercially available. It is necessary to.
[0060]
Further, since the light receiving sensitivity of the light receiving element is actually more marginal than the standard value, it is desirable that the return loss is 40 dB or more for practical use in consideration of that amount. In order to secure a margin and obtain a stable characteristic, it is desirable that it is 45 dB or more.
[0061]
Therefore, as described in the present embodiment based on the above considerations, the optical cross-connect device 1 includes a J × J two-dimensional MEMS matrix type optical switch with a return loss of 50 dB or more, and terminals that are not used. An optical cross-connect device 1 is further used by using a 1 × 2 optical coupler 4 that is non-reflectively terminated so that the return loss is 50 dB or more, and a physical contact type SC optical connector that achieves a return loss of 50 dB or more. An optical cross-connect device in which the attenuation amount of the entire device is 45 dB or more can be realized by making all the internal optical wirings into ordinary single mode optical fibers and the optical adapter as a double SC type optical adapter.
[0062]
With such a configuration, the return loss of the optical cross-connect device can be set to 45 dB or more, so that bidirectional communication using the same wavelength can be performed. Thereby, the scale of the matrix type optical switch used for the optical cross-connect device can be reduced to ¼ of the conventional size. In addition, two or more types of light sources for upstream and downstream that have been necessary in conventional bidirectional communication can be realized by one type, and further no wavelength filter for demultiplexing wavelengths is required. In comparison, it can be realized at a low cost.
[0063]
【The invention's effect】
Therefore, according to the present invention, a low-cost optical cross-connect device can be obtained while ensuring sufficient crosstalk even in bidirectional communication at the same wavelength by eliminating optical noise caused by reflection using a low-reflection optical component. Can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an optical cross-connect device 1 according to an embodiment of the present invention.
FIG. 2 is a diagram showing a configuration of a conventional optical cross-connect device 101. FIG.
FIG. 3 is a diagram showing a configuration of an SC type two-fiber optical connector 106;
4 is a diagram showing a configuration in which J × J matrix type optical switches 103a and 103b are arranged in place of the M × N matrix type optical switch of the conventional optical cross-connect device 101. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Optical cross-connect apparatus 2 ... Control part 3 ... JxJ matrix type optical switch 4 ... Optical coupler 101 ... Optical cross-connect apparatus 102 ... Control part 103 ... MxN matrix type optical switch 106 ... SC type 2 core optical connector 106a ... Receptacle 106b ... Plug

Claims (3)

A J × J matrix optical switch having J optical input ports and J optical output ports; 2J input ports connected to input terminals of the J × J matrix optical switch; Light that includes at least 2J output ports connected to the output terminal of the matrix type optical switch and control means for switching and controlling the switching means, and outputs signal light input from a certain input port to a predetermined output port A cross-connect device,
A pair of optical connectors or a two-fiber optical connector is provided for each pair of input / output ports constituted by one input port of the input ports and one output port of the output ports. wherein between the J × J matrix type optical switch, insert arranged 1 × 2 optical coupler Yu and and two single-mode optical fiber of the output of one to the input of the two by melt stretching An optical cross-connect device that uses a single-mode optical fiber as an internal optical wiring and performs bidirectional communication using light of the same wavelength .   The reflection attenuation amount for each optical path of the optical cross-connect device including all the reflections of the optical connector, the 1 × 2 optical coupler, and the J × J matrix type optical switch is 40 dB or more. The optical cross-connect device according to claim 1.   The reflection attenuation amount for each optical path of the optical cross-connect device including all the reflections of the optical connector, the 1 × 2 optical coupler, and the J × J matrix type optical switch is 45 dB or more. The optical cross-connect device according to claim 1.

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