JP6306449B2 - Active optical star coupler device - Google Patents

Description

  The present invention relates to an active optical star coupler device that connects an OLT (telephone station side termination device) and an ONU (subscriber premises side termination device) in a PON (Passive Optical Network).

  By connecting the OLT and a large number of ONUs in a star shape with optical star couplers and optical fibers, and multiplexing and using optical signals with different wavelengths in the upstream and downstream directions on a single optical fiber In an optical communication system that realizes general communication, an active optical star coupler device is used for concentrating instead of an optical star coupler.

  As one of concentrated optical communication systems, a PON system using an optical star coupler has been put into practical use. For example, there are systems called GE-PON (the following non-patent document 1) and 10GE-PON (the following non-patent document 2) as PON systems whose details of the signal system are standardized by IEEE. An outline of the operation of the PON system is shown in, for example, Non-Patent Document 3 below.

  The PON system is characterized in that an economical optical communication system can be realized by collecting information transmitted from a large number of ONUs using an optical star coupler and processing the information with a single OLT. Hereinafter, a conventional PON system will be briefly described with reference to FIGS.

  FIG. 9 is a schematic diagram showing a configuration example of a conventional PON system in which one OLT 100 and N ONUs 310 to 3N0 are connected using an optical star coupler 21. In general, it is assumed that the OLT 100 is installed in a communication building and the ONUs 310 to 3N0 are installed in each home.

  The OLT 100 includes a multiplexer / demultiplexer 101, an optical transmitter 102, an optical receiver 103, and a control unit 104. The ONU 3i0 (i is any value from 1 to N) includes an optical receiver 3i2, an optical transmitter 3i3, a multiplexer / demultiplexer 3i1, and a control unit 3i4.

  The OLT 100 and the ONUs 310 to 3N0 are connected via the optical fiber 210, the optical star coupler 21, and the optical fibers 211 to 21N.

  In the optical fibers 210 to 21N, the downstream optical signal (downstream signal) from the OLT 100 to the ONUs 310 to 3N0 and the upstream optical signal (upstream signal) from the ONUs 310 to 3N0 to the OLT 100 are reversed at different wavelengths. Is transmitted.

  Hereinafter, a downlink communication method of the conventional PON system will be described.

  FIG. 10 is a schematic diagram illustrating a state in which the optical signal 40 output via the multiplexer / demultiplexer 101 is divided into optical signals 41 to 4N on the N optical fibers 211 to 21N in the optical star coupler 21. It is.

  In the downstream direction, all the information to be transmitted from the OLT 100 to all or each of the ONUs 310 to 3N0 is transmitted from the optical transmitter 102 as a continuous optical signal. The downstream signal and the continuous optical signal are referred to as an optical signal 40.

  The optical signal 40 transmitted from the optical transmitter 102 is input to the optical star coupler 21 through the optical fiber 210 via the multiplexer / demultiplexer 101. The optical star coupler 21 branches the input optical signal 40 to N optical fibers 211 to 21N and transmits the branched optical signal 40.

  The optical signals 41 to 4N divided by the star coupler 21 are input to the ONUs 310 to 3N0, respectively. The optical signal 4i input to the ONU 3i0 is demultiplexed by the multiplexer / demultiplexer 3i1 and input to the optical receiver 3i2. After receiving the optical signal 4i, the optical receiver 3i2 selects and processes information addressed to its own ONU 3i0 and information addressed to all the ONUs 310 to 3N0.

Note that the optical signals 41 to 4N are completely copied with respect to temporal changes as compared with the input optical signal 40, but have an intensity of 1 / N.
The above is the downstream communication method of the conventional PON system.

  Hereinafter, the uplink communication method of the conventional PON system will be described.

  FIG. 11 is a schematic diagram illustrating how the optical signals 51 to 5N output from the respective ONUs 310 to 3N0 are multiplexed by the optical star coupler 21 and output as the optical signal 50.

  In the upstream direction, information desired to be transmitted from the ONU 3i0 to the OLT 100 is transmitted as an optical burst signal independent of the optical transmitter 3i3. The upstream signal and the optical burst signal are referred to as an optical signal 50.

  The optical signal 5i transmitted from the optical transmitter 3i3 is input to the optical star coupler 21 through the optical fiber 21i via the multiplexer / demultiplexer 3i1. The optical star coupler 21 multiplexes the optical signals 51 to 5N input from the N optical fibers 211 to 21N and outputs the multiplexed optical signals to the optical fiber 210.

  Note that due to the optical properties of the optical star coupler 21, the optical signal 50 is multiplexed so that the optical signals 51 to 5N each have an intensity of 1 / N.

  The optical signal 50 input to the OLT 100 is demultiplexed by the multiplexer / demultiplexer 101 and input to the optical receiver 103. The optical receiver 103 receives the optical signal 50 and processes the information sent from each of the ONUs 310 to 3N0.

  However, as described above, when the optical signals 51 to 5N are output from the optical star coupler 21 as the optical signal 50, if the optical signals 51 to 5N overlap in time, the optical receiver 103 causes the ONUs 310 to 310 to overlap each other. Information from 3N0 cannot be input correctly.

  Therefore, in the PON system, the optical signals 51 to 5N transmitted by the respective ONUs 310 to 3N0 are multiplexed by the optical star coupler 21 as a sequence of optical burst signals spaced apart by a certain guard time or more. Means for adjusting the transmission timing of the optical signals 51 to 5N from the respective ONUs 310 to 3N0 are provided.

  The detailed procedure is defined in the following Non-Patent Documents 1 and 2, but the control unit 104 of the OLT 100 and the control units 314 to 3N4 of the ONUs 310 to 3N0 use the downlink and uplink communication methods. By exchanging information, the control unit 104 and the control units 314 to 3N4 can operate in synchronization.

Further, the transmission timing of the optical signals 51 to 5N can be notified from the OLT 100 so that the upstream optical signals 51 to 5N from the ONUs 310 to 3N0 do not arrive at the optical star coupler 21 at the same time.
The above is the upstream communication method of the conventional PON system.

IEEE 802.3ah-2004 IEEE 802.3av-2009 NTT Technical Journal, August 2005, p. 71-74, Technology Basic Course [GE-PON Technology]

  Here, FIG. 12 is a schematic diagram showing a state in which optical star couplers are connected in multiple stages in a conventional PON system.

  In the conventional PON system described above, if one OLT can handle a larger number of ONUs, the economics of the system can be improved. For this reason, as shown in FIG. 12, more ONUs 310 to 3N0 are accommodated by connecting the optical star coupler 2M in multiple stages.

  While the communication speed of optical transmitters and optical receivers used in the PON system is improved by the advancement of technology, while the increase in the amount of information transmitted from each home is small, A sufficient communication band can be secured for each ONU.

  However, as described above, when N optical signals are branched or multiplexed using the optical star couplers 20 to 2M, the intensity of each optical signal is reduced to 1 / N.

  Therefore, when the number of branches is increased using the optical star couplers 20-2M, the intensity of the optical signal becomes weaker as the number of branches increases, and the light input to the optical receiver 103 and the optical receivers 312-3N2 The signal falls below the minimum light receiving sensitivity (the minimum intensity of the optical signal necessary for the optical receiver 103 and the optical receivers 312 to 3N2 to correctly receive information).

  Therefore, the intensity of the branched downstream signal (optical signals 41 to 4N) and the multiplexed upstream signal (optical signal 50) maintain the light reception sensitivity (maintain the minimum light reception sensitivity or more). A certain limit is determined for the maximum number of optical branches within the range, that is, the maximum number of ONUs accommodated.

  In the PON system as described above, it is conceivable to increase the intensity of the optical signal as a method for further expanding the ONU accommodation number beyond the limit of the number of branches of the light receiving sensitivity.

  Specifically, there are a method of increasing the output intensity of the light source in the optical transmitter 102 and the optical transmitters 313 to 3N3, and a method of increasing the intensity of the optical signal using an optical amplifier.

  Here, in the downstream direction, since there is only one optical transmitter 102 of the OLT 110, the output intensity of the optical transmitter 102 is increased, or between the optical transmitter 102 and the multiplexer / demultiplexer 101. One optical amplifier may be arranged. That is, the cost and energy required for arranging one optical amplifier is small, and this method is a realistic option. FIG. 12 shows a state in which a high-power optical transmitter 105 is used instead of the optical transmitter 102 (FIGS. 9 to 11).

  However, since the number of ONUs 310 to 3N0 is large in the upstream direction, if the method of increasing the output intensity as described above is used for the light sources of the optical transmitters 313 to 3N3 of all the ONUs 310 to 3N0, the cost and energy There is a problem that the increase in the number of cases becomes very large.

  Also, if the method using an optical amplifier as described above is used in the upstream direction, it is necessary to place an optical amplifier in each of the upstream inputs of the optical star coupler, unlike the downstream direction. There is a problem that the increase in energy becomes very large.

  Therefore, the present invention provides an active optical star coupler device that suppresses a decrease in the intensity of an optical burst signal in the upstream direction without using an optical amplifier or the like and realizes the number of branches exceeding the limit of the conventional optical star coupler. For the purpose.

An active optical star coupler device according to a first invention for solving the above-mentioned problems is as follows.
An optical star coupler having one first optical input signal line and M first optical output signal lines (M is an arbitrary integer greater than or equal to 2);
An optical switch having M second optical input signal lines and one second optical output signal line;
M first multiplexers / demultiplexers respectively connected to the first optical output signal lines and the second optical input signal lines;
The optical signal arriving at each of the second optical input signal lines is determined based on the time calculated by the OLT control unit that determines the transmission timing of the optical burst signal and calculates the time when the optical burst signal reaches the optical switch. And an optical switch controller that controls the optical switch in accordance with the timing of the burst signal.

An active optical star coupler device according to a second invention for solving the above-mentioned problems is as follows.
In the active optical star coupler device according to the first invention,
A second multiplexer / demultiplexer connected to the first optical input signal line and the second optical output signal line is provided.

An active optical star coupler device according to a third invention for solving the above-mentioned problems is as follows.
An optical star coupler having one first optical input signal line and M first optical output signal lines (M is an arbitrary integer greater than or equal to 2);
An optical switch having M second optical input signal lines and one second optical output signal line;
M first multiplexers / demultiplexers respectively connected to the first optical output signal lines and the second optical input signal lines;
An optical switch controller that controls the optical switch in accordance with the timing of an optical burst signal that arrives at each of the second optical input signal lines;
For each of the second optical input signal lines,
An optical branching device for bifurcating the optical burst signal;
A photoreceiver that receives one of the optical burst signals branched by the optical splitter and converts it into an electrical signal;
A determinator for determining from the electrical signal whether the optical burst signal has arrived at each of the second optical input signal lines;
After adding a certain delay to the other optical burst signal branched by the optical splitter, connected to an optical delay line to be input to the optical switch,
Each of the determiners detects the beginning and end of each of the optical burst signals,
The optical switch control unit controls switching of the optical switch based on detection of all the determination units , and when a plurality of the optical burst signals are duplicated, determination of a head of a new optical burst signal is performed. The switching of the optical switch is controlled so that the optical burst signal is transferred to the second output signal line with priority given to .

An active optical star coupler device according to a fourth invention for solving the above-mentioned problems is as follows.
In the active optical star coupler device according to the third invention,
Each of the determiners is
Means for obtaining an integral value of the electrical signal output by the light receiver in a certain period;
And a means for comparing the integrated value with a certain threshold value.

  According to the active optical star coupler device according to the present invention, it is possible to suppress the decrease in the intensity of the optical burst signal in the upstream direction without using an optical amplifier or the like and realize the number of branches exceeding the limit of the conventional optical star coupler. Can do.

It is the schematic which showed the principle of operation at the time of multiplexing the upstream signal in a PON system using an optical concentrator switch. 1 is a schematic diagram of a PON system including an active optical star coupler device according to a first embodiment of the present invention inside an OLT. FIG. It is the schematic of a PON system provided with the active optical star coupler apparatus based on Example 2 of this invention outside OLT. It is the schematic of a PON system provided with the active optical star coupler apparatus which concerns on Example 3 of this invention outside OLT. It is the schematic which shows the structure of an autonomous control type optical concentrator switch. It is a graph which shows the specific determination method of a determination device. It is the graph showing the example of the output of a light receiver and a determination device when the optical burst signal which spaced a short time interval arrives at three optical input signal lines. It is the schematic which shows the example of a 16x16 active light star coupler apparatus. It is the schematic which shows the structural example of the conventional PON system which connected OLT and ONU using the optical star coupler. It is the schematic which shows a mode that the optical signal output via the multiplexer / demultiplexer was divided | segmented into the optical signal on N optical fibers in an optical star coupler. It is the schematic which shows a mode that the optical signal which each ONU output is multiplexed and output by an optical star coupler. It is the schematic which shows a mode that the optical star coupler was connected in multistage in the conventional PON system.

  The active optical star coupler according to the present invention splits and transfers an optical signal for a downstream signal in the same manner as a conventional optical star coupler, but for an upstream signal, an optical burst signal is multiplexed using an internal optical switch. Therefore, in principle, transfer can be performed without reducing the intensity of the optical burst signal.

  For this reason, when an active optical star coupler is used instead of the conventional optical star coupler in combination with an increase in the intensity of the downstream signal of the OLT, the conventional optical star coupler is used without changing the upstream signal intensity of the ONU or the minimum light receiving sensitivity of the OLT. The above number of branches can be realized, and an economical optical communication system capable of accommodating more ONUs can be realized with one OLT.

  That is, the active optical star coupler device according to the present invention maintains the optical intensity of the optical burst signal using an optical concentrator switch that controls switching timing in a communication system that multiplexes optical burst signals such as a PON system. It can be multiplexed as it is. Thereby, the active optical star coupler device according to the present invention can economically exceed the limit of the number of ONU convergence of the conventional PON system and can accommodate many ONUs without using an optical amplifier or the like.

  FIG. 1 is a schematic diagram showing an operation principle when uplink signals in a PON system are multiplexed using an optical concentrator switch. Hereinafter, the principle of operation when the upstream signal in the PON system is multiplexed using the optical concentration switch will be described.

  First, by controlling the transmission timing of each ONU 310-3N0, all the optical signals (upstream signals) 61-6N arrive at the optical switch 80 at shifted timings.

  Here, the optical concentrator switch 90 includes an optical switch 80 and an optical switch control unit 81.

  The optical switch control unit 81 controls switching of the optical switch 80 in accordance with the timing at which the optical signals 61 to 6N arrive. Further, the optical switch 80 multiplexes the arrived optical signals 61 to 6N under the control of the optical switch control unit 81 and outputs the multiplexed optical signal (upstream signal and optical burst signal) 60.

  In the multiplexing of the optical signal using the conventional optical star coupler, even if an optical star coupler having a very good performance is used, the intensity is theoretically 1 / N. When multiplexed using, the theoretical loss between connected input and output fibers is zero.

  That is, when multiplexed using the optical concentrator switch 90, the optical signals 61 to 6N are multiplexed as the optical signal 60 and transferred to the OLT 100 while maintaining the strength when input.

  The actual optical switch 80 has a loss inherent in the device itself, but the theoretical loss is 0. Therefore, if the number of branches is large, an optical switch with a sufficiently small loss can be realized as compared with the conventional optical star coupler. can do.

  In the PON system, it is necessary to consider both the downlink signal and the uplink signal. However, as described above, the intensity of the optical signal is increased in the downlink direction (transmission of the light source (optical transmitter) on the transmission side of the OLT 100). It is easy to increase power).

  Therefore, in the active optical star coupler device according to the present invention, the strength of the upstream optical burst signal is obtained by combining the optical star coupler that branches the downstream signal and the optical switch that multiplexes the upstream optical burst signal. The number of branches exceeding the limit of the conventional optical star coupler can be realized.

  Hereinafter, an active optical star coupler device according to the present invention will be described in each embodiment with reference to the drawings.

[Example 1]
The device configuration of the active optical star coupler device according to the first embodiment of the present invention will be described with reference to FIG. FIG. 2 is a schematic diagram of a PON system in which the number of ONUs is increased by providing the active optical star coupler device (active optical star coupler device 900) according to the first embodiment of the present invention inside the OLT.

  In the PON system using the active optical star coupler device 900 of FIG. 2, the output of the light source of the optical transmitter of the OLT 120 is increased in the downstream direction, and the optical burst signal is multiplexed by the optical concentrator switch 90 in the upstream direction. Is used.

  That is, the PON system of FIG. 2 includes an optical receiver 103, a control unit 104, and an active optical star coupler device 900 inside the OLT 120, and further includes a high-power optical transmitter 105 as an optical transmitter of the OLT 120. ing.

  Here, the high-power optical transmitter 105 is assumed that the output intensity of the light source (the intensity of the optical signal) is M times that of the conventional optical transmitter.

  The active optical star coupler device 900 includes an optical star coupler 85, an optical concentrator switch 90, and multiplexers / demultiplexers 91 to 9M.

  The optical star coupler 85 has one optical input signal line (optical fiber) 850 and M optical output signal lines (optical fibers) 911 to 9M1 (M is an arbitrary integer equal to or greater than 2). The one that branches. Note that a high-power optical transmitter 105 is connected to the other side of the optical input signal line 850.

  The multiplexers / demultiplexers 91 to 9M are connected to the optical output signal lines 911 to 9M1 of the optical star coupler 85 and the optical input signal lines (optical fibers) 912 to 9M2 of the optical switch 80.

  The optical concentrator switch 90 includes an optical switch 80 and an optical switch control unit 81.

  The optical switch 80 has M optical input signal lines 912 to 9M2 and one optical output signal line (optical fiber) 800, and multiplexes upstream signals (optical burst signals) that arrive from the optical fibers 912 to 9M2. And output to the optical receiver 103 through the optical output signal line 800.

  The optical switch control unit 81 controls the switching of the optical switch 80 through the signal line 82 in accordance with the timing of the upstream signal arriving at each of the optical input signal lines 912 to 9M2.

  The optical switch control unit 81 is connected to the control unit 104 via the signal line 84 and obtains information regarding the timing at which the upstream signal arrives at the optical switch 80 from the control unit 104 of the OLT 120.

  That is, as described above, the control unit 104 of the OLT 120 determines the transmission timing of the upstream signal (optical burst signal) of each ONU 310 to 3N0.

  Therefore, the control unit 104 of the OLT 120 can calculate the time when the upstream signal (optical burst signal) transmitted from each ONU 310 to 3N0 reaches the optical switch 80 by improving the internal arithmetic processing. The result can be transmitted to the optical switch control unit 81 through the signal line 84 as timing information for controlling the optical switch 80.

  Hereinafter, the operation of the PON system using the active optical star coupler device according to the first embodiment of the present invention will be described in detail.

First, the downlink signal will be described.
When the optical signal (downlink signal) output from the high-power optical transmitter 105 is input to the active optical star coupler device 900 through the optical fiber 850, the optical star coupler (splitter) 85 branches the optical signal into M optical fibers. The signals are input to the multiplexers / demultiplexers 91-9M through 911-9M1.

  At this time, the intensity of each optical signal after being branched into M lines is comparable to that of a normal optical transmitter (the optical transmitter 102 in FIGS. 9 to 11 and 1).

The downlink signals branched into M are input to the optical star couplers (splitters) 21 to 2M via the multiplexers / demultiplexers 91 to 9M. Thereafter, the same operation as that of the optical signals 41 to 4N in FIG. 10 is performed for each of the optical star couplers 21 to 2M.
This completes the description of the downlink signal.

Next, the uplink signal will be described.
When the optical signals (upstream signals) output from the respective ONUs 310 to 3N0 are input to the active optical star coupler device 900 through the optical star couplers 21 to 2M through the optical fibers 211 to 2MN and 210 to 2M0, Uplink signals are demultiplexed by the multiplexers / demultiplexers 91 to 9M and input to the optical switch 80 in the optical concentrator switch 90 through the optical fibers 912 to 9M2.

  Switching of the optical switch 80 is controlled by the optical switch control unit 81, and the optical switch control unit 81 obtains timing information at which the upstream signal arrives at each of the optical fibers 912 to 9 M 2 from the control unit 104 of the OLT 120.

  As described above, the control unit 104 of the OLT 120 determines the transmission timing of the upstream signal of each ONU 310 to 3N0.

  Therefore, the control unit 104 of the OLT 120 can calculate the time when the upstream signal transmitted from each of the ONUs 310 to 3N0 reaches the optical switch 80 by improving the internal arithmetic processing. Timing information for controlling the switch 80 can be transmitted to the optical switch control unit 81 through the signal line 84.

  The optical switch 80 can switch according to the arrival timing of the upstream signal, multiplexes the upstream signal input from the optical star couplers 21 to 2M, and outputs the multiplexed signal to the optical receiver 103 through the optical fiber 800. At this time, the optical intensity of the upstream signal is transferred while maintaining the intensity input to the optical switch 80 in principle.

The uplink signal input to the optical receiver 103 is thereafter subjected to reception processing in the same manner as in FIG.
This completes the description of the uplink signal.

  The optical star coupler 85 and the multiplexers / demultiplexers 91 to 9M in the active optical star coupler device 900 described above can be manufactured on an integrated optical circuit using a quartz material, and the optical switch. By combining the (high-speed optical switch) 80, an active optical star coupler device can be realized economically.

  The active optical star coupler device according to the first embodiment of the present invention has been described above. In other words, the active optical star coupler device according to the first embodiment of the present invention includes one first optical input signal line (optical Optical star coupler 85 having an input signal line 850) and M first optical output signal lines (optical output signal lines 911 to 9M1) (M is an arbitrary integer greater than or equal to 2), and M second optical input signals Optical switch 80 having a line (optical input signal lines 912 to 9M2) and one second optical output signal line (optical output signal line 800), and each first optical output signal line and each second optical input signal line. Optical switches that control the optical switch 80 in accordance with the timing of optical burst signals arriving at the respective second optical input signal lines and M first multiplexers / demultiplexers (multiplexers 91 to 9M) connected thereto. And a control unit.

[Example 2]
A device configuration of an active optical star coupler device according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 3 is a schematic diagram of a PON system including an active optical star coupler device (active optical star coupler device 910) according to the second embodiment of the present invention outside the OLT.

  In the PON system using the active optical star coupler device 910 of FIG. 3, the OLT 130 includes an optical receiver 103, a control unit 104, and a high output optical transmitter 105, and further from the high output optical transmitter 105. A multiplexer / demultiplexer 101 that demultiplexes an output signal to the active optical star coupler device 910 and an input signal from the active optical star coupler device 910 to the optical receiver 103 is provided.

  Similarly to the first embodiment, the active optical star coupler device 910 includes an optical star coupler 85, an optical concentrator switch 90, a multiplexer / demultiplexer 83, and multiplexers / demultiplexers 91 to 9M. Further, the active optical star coupler device 910 demultiplexes the downstream signal passing through the optical input signal line 850 of the optical star coupler 85 and the upstream signal passing through the optical output signal line 800 of the optical switch 80. It has.

  In the PON system of FIG. 3, the optical switch control unit 81 is connected to the control unit 104 of the OLT 130 via the signal line 84, and an upstream signal (for controlling switching of the optical switch 81 of the active optical star coupler device 910). Information regarding the arrival timing of the optical burst signal is obtained from the control unit 104 of the OLT 130.

  With the above configuration, the active optical star coupler device 910 can be arranged outside the OLT 130, and the optical signal is connected to the OLT 130 by a single optical fiber 830 as in the conventional optical star coupler. Therefore, the degree of freedom regarding the arrangement of the active optical star coupler device 900 in the OLT 130 is increased.

  In addition, since the modification of the OLT 130 is only a change in the arithmetic processing of the control unit 104, the change from the conventional PON system is small, and the introduction of the active optical star coupler device 910 is facilitated.

  However, since the active optical star coupler device 910 of FIG. 3 is connected to the OLT 130 by the signal line 84, in order to control the optical switch 80 in accordance with the timing at which the upstream signal arrives accurately, It is necessary to pay sufficient attention to the length.

  The active optical star coupler device according to the second embodiment of the present invention has been described above. In other words, the active optical star coupler device according to the second embodiment of the present invention includes the first optical input signal line (optical input signal line). 850) and the second optical output signal line (optical output signal line 800), the second multiplexer / demultiplexer (multiplexer / demultiplexer 83) connected to the second optical output signal line (optical output signal line 800) can be installed outside the OLT 130. .

[Example 3]
A device configuration of an active optical star coupler device according to Embodiment 3 of the present invention will be described with reference to FIG. FIG. 4 is a schematic diagram of a PON system including an active optical star coupler device (active optical star coupler device 920) according to the third embodiment of the present invention outside the OLT.

  In the PON system using the active optical star coupler device 920 in FIG. 4, the flow of the downstream signal and the upstream signal is the same as that of the second embodiment, and the arrival information of the upstream signal (optical burst signal) input to the optical switch control unit. The means for generating is different.

  The active optical star coupler device 920 shown in FIG. 4 includes the optical star coupler 85, the multiplexer / demultiplexer 83, and the multiplexers / demultiplexers 91 to 9M, as in the second embodiment. Further, the active light star coupler device 920 includes an autonomous control type light concentration switch 86 instead of the light concentration switch 90 in the second embodiment.

  As in the second embodiment, the autonomous control type optical concentrator switch 86 does not obtain information on the arrival timing of the upstream signal for controlling the switching of the optical switch 80 from the control unit of the OLT 130, but the autonomous control type optical concentrator switch 86. By providing means for monitoring whether or not the optical burst signal has reached the optical input signal lines 912 to 9M2 connected to the concentrator switch 86, the optical switch 80 described later is autonomously controlled.

  In the above configuration, since the control signal from the control unit 104 of the OLT 130 (the above-described information related to the arrival timing of the upstream signal for controlling the switching of the optical switch 80) is unnecessary, the signal line 84 is not provided. Therefore, it can be placed at any position from the OLT 130. That is, the degree of freedom regarding arrangement further increases.

  In addition, since the loss of the upstream signal can be made smaller than that of the optical star coupler having the same number of branches, the economical PON system can be used to realize a large-scale optical branching and accommodates more ONUs. Can be realized.

  Here, FIG. 5 shows a configuration of an autonomous control type optical concentrator switch 86 having means for autonomously controlling the optical switch 80.

  The autonomous control type optical concentrator switch 86 has M optical input signal lines 912 to 9M2 and one optical output signal line (optical fiber) 800. In addition, an optical switch 80 and an optical switch control unit 81 are provided inside, and further, optical branching devices 8021 to 802M, light receiving devices 8041 to 804M, determination devices 8061 to 806M, and optical delay lines (optical fibers) 8081 to 8081. 808M, optical signal lines (optical fibers) 8031 to 803M, a signal line 82, signal lines 8051 to 805M, and signal lines 8071 to 807M.

  In the autonomous control type optical concentrator switch 86, the optical input signal lines 912 to 9M2 include optical branching devices 8021 to 802M, optical receivers 8041 to 804M, determiners 8061 to 806M, optical delay lines 8081 to 808M, optical signals, respectively. Lines 8031 to 803M, signal lines 8051 to 805M, signal lines 8071 to 807M, and signal line 82 are connected to each other. The optical output signal line 800 is connected to the optical switch 80.

  The optical splitters 8021 to 802M split the upstream signal (optical burst signal) from the optical input signal lines 912 to 9M2 into two, and one output is input to the optical switch 80 via the optical delay lines 8081 to 808M. . The other outputs of the optical splitters 8021 to 802M are input to the optical receivers 8041 to 804M via the optical signal lines 8031 to 803M.

  The light receivers 8041 to 804M receive one upstream signal branched from the optical branching devices 8021 to 802M via the optical signal lines 8031 to 803M, convert the upstream signal into an electrical signal, and determine the electrical signal as a determination device. Output to 8061-806M.

  Based on the electric signals input from the light receivers 8041 to 804M via the signal lines 8051 to 805M, the determiners 8061 to 806M have arrived at the optical input signal lines (optical input signal lines 912 to 9M2). The determination result is output to the optical switch control unit 81 via the signal lines 8071 to 807M.

  The optical delay lines 8081 to 808M are extended in length, so that a certain delay is added to the upstream signal of one output of the optical branching devices 8021 to 802M and the optical delay lines 8081 to 808M are output to the optical switch 80.

  The optical switch control unit 81 controls switching of the optical switch 80 based on the output signals from all the determiners 8061 to 806M.

  Hereinafter, the operation of the autonomous control type light collecting switch 86 will be described.

  First, the optical branching device 802i (i = 1 to M) branches the upstream signal input from the optical input signal line 9i2 from the outside, and outputs it to the optical delay line 808i and the optical signal line 803i. At this time, it is assumed that most of the upstream signals are output at a branching ratio so that they are output to the optical delay line 808i side.

  The upstream signal output to the optical signal line 803i is input to the light receiver 804i and converted into an electrical signal. Since the electrical signal is used not only for receiving information in the upstream signal but for detecting the presence of the upstream signal, the optical receiver 804i has a signal band slower than the bit rate of the upstream signal. An inexpensive light receiver having the above may be used.

  The electrical signal output from the light receiver 804i is input to the determiner 806i via the signal line 805i.

  The determiner 806i determines 1 from the input electrical signal when it is determined that the upstream signal has arrived at the optical input signal line 9i2, and 0 when it is determined that the upstream signal has not been input. Is output. Here, when the determiner 806i receives the first bit of the upstream signal (optical burst signal), it is desirable to detect it as soon as possible.

  In addition, the determiner 806i considers that a bit string of various patterns appears in the upstream signal (optical burst signal) and some 0 bits are continuous, and that the upstream signal is continuing, and It is determined that the uplink signal has ended.

  Here, the determiners 8061 to 806M include integration means for obtaining an integral value of the electrical signals output from the light receivers 8041 to 804M for a certain period, and comparison means for comparing the integral value with a certain threshold value. May be provided. Hereinafter, the determination procedure by the determiner 806i will be described.

  FIG. 6 is a graph showing a specific determination method of the determiner 806i. When the output (electric signal) from the light receiver 804i receiving the upstream signal to the determiner 806i has a value as shown in FIG. 6A, the value obtained by integrating this in the determiner 806i is shown in FIG. It is shown in 6 (b).

  If the output of the light receiver 804i is positive, the integrated value increases greatly. If the output from the light receiver 804i is 0, the integrated value decreases gradually.

  Here, as shown in FIG. 6B, a fixed determination threshold value is provided in the determiner 806i, and the integration value that changes with time is compared with the determination threshold value. As shown in (c), the output is 1 if the integral value exceeds this threshold value, and 0 is output otherwise.

  In this way, the determiner 806i outputs 1 only while the upstream signal arrives at the optical input signal line 9i2.

  However, when the above operation is analyzed in detail, the delay time until the start of the upstream signal is determined is t1, and the delay time until the end of the upstream signal is determined is t2 (FIG. 6 (c)). It should be noted that the determination of the end of the signal generally takes t2> t1 because it takes time because it is necessary to wait for a constant 0 input to continue.

  Next, the outputs of the determiners 8061 to 806M are input to the optical switch control unit 81, and the optical switch control unit 81 selects the optical input signal line connected to the determiners 8061 to 806M that determined the arrival of the upstream signal. Then, the optical switch is controlled so as to be connected to the optical output signal line 800.

  Here, after the upstream signal arrives at the autonomous control type optical switch 86, this information is transmitted to the optical switch control unit 81 via the light receivers 8041 to 804M and the determiners 8061 to 806M, and the optical signal is actually transmitted. It takes a certain time to complete the switching control of the switch 80.

  Therefore, the optical delay lines 8081 to 808M are adjusted to a length that takes into account such a control delay in advance, and the upstream signals input from the optical input signal lines 912 to 9M2 are delayed by a certain time. The timing adjustment is realized such that the upstream signal is input to the optical switch 80 when the switching control of the optical switch 80 is just completed.

  As shown in FIG. 6C, since a certain delay occurs in the detection of the end of the upstream signal by the determiners 8061 to 806M, the time from the plurality of optical input signal lines 912 to 9M2 is short. When an upstream signal arrives at an interval, the outputs of the determiners connected to the optical input signal lines 912 to 9M2 may overlap in time.

  For example, FIG. 7 shows light receivers 8041 to 8043 (in FIG. 7, the first to first light receivers 8041 to 8043) when upstream signals (optical burst signals) arrive at three optical input signal lines 912 to 932 at short intervals. It is a graph showing an example of the output of the determination devices 8061 to 8063 (described as the first to third determination devices in FIG. 7).

  When the first to third light receivers output an output signal as shown in FIG. 7A in response to the arrival of the upstream signal, the corresponding outputs of the first to third determiners are shown in FIG. 7B. The time changes as shown in

  That is, although the actual uplink signal arrives without overlapping in time, the determination delay t2 at the end of the optical burst signal is longer than the determination delay t1 at the start of the uplink signal. The outputs of the third determiner will overlap.

  Therefore, when the outputs of the first to third determiners overlap, the optical switch control unit 81 gives priority to the determination of arrival of a new uplink signal, and each of the first to third determiners determines a new uplink signal. Corresponding to the optical input signal lines (in FIG. 5, the optical input signal lines 912 to 9M2 having the optical delay lines 8081 to 808N) at the time of detecting the head of (A1, A2, A3 in FIG. 7B). In addition, control for switching the optical switch 80 is performed.

  In other words, in the optical switch control unit 81, each of the determiners 8061 to 806M newly arrives at the second optical input signal line (optical input signal line 912 to 9M2) at the head of the upstream signal (optical burst signal). The switching of the optical switch 80 is controlled so that the upstream signal (optical burst signal) is transferred to the second output signal line (optical output signal line 800).

  By performing the above control, in order to prevent an erroneous determination that a new upstream signal has arrived after the upstream signal has been terminated once for upstream signals that may have many 0 bits, It is possible to make a setting so that the determination at the end of the burst signal takes a sufficient amount of time, always accurately determining that a new upstream signal has arrived, and controlling the switching of the optical switch 80 with high accuracy. It becomes possible.

  As described above, the active optical star coupler apparatus according to the present invention has been described by using each embodiment. In the above description, the optical device is ideally described, and the principle of loss reduction is described.

  Here, a trial calculation example relating to loss in the case where the active optical star coupler device according to the present invention is configured using a realistic optical device having a certain amount of excess loss will be described.

  For example, assuming that the maximum number of ONUs in a standard PON system is accommodated by a combination of a 4 × 4 optical star coupler and another optical star coupler, the 4 × 4 optical star coupler is 16 × Consider changing to 16 active optical star coupler devices according to the present invention, and increasing the maximum capacity of ONUs four times.

  First, the conventional 4 × 4 optical star coupler has a theoretical loss of 6 dB. However, assuming that the excess loss is about 1 dB, the system configuration is expected to have a loss of about 7 dB.

  Next, a 16 × 16 optical star coupler 85, 15 2 × 2 optical switches 80, 16 optical splitters 8021, 16 optical delay lines 70, and 17 multiplexers / demultiplexers A 16 × 16 active optical star coupler device according to the present invention using the demultiplexer 83 and the 16 multiplexers / demultiplexers 91) is shown in FIG. However, in FIG. 8, only a part of the optical branching device 8021, the optical delay line 70, and the multiplexer / demultiplexer 91 are described.

  Among the optical devices shown in FIG. 8 (16 × 16 active optical star coupler device), the multiplexer / demultiplexer 83, the multiplexer / demultiplexer 91, the optical splitter 8021, and the optical star coupler 85 are: It is known that an optical integrated circuit having a very high performance can be realized by a planar optical waveguide circuit technology using a quartz-based material.

  For example, in FIG. 8, the multiplexer / demultiplexer 83 and the optical star coupler 85 on the OLT 130 side are used as the first optical integrated circuit, and the optical branching device 8021 and the ONU side multiplexer / demultiplexer 91 are used as the second optical integrated circuit. Each can be realized.

  Further, the 15 optical switches 80 can be integrated by using, for example, InP-based optical semiconductor device technology, and can be realized as a third optical integrated circuit.

  In such a configuration, in the first optical integrated circuit, a multiplexer / demultiplexer having a loss of about 13 dB obtained by adding an excess loss of 1 dB to the theoretical loss of 12 dB of the optical star coupler 85 in the downstream direction, and in principle having no loss in the upstream direction. 1 only, and excess loss is considered to be about 1 dB.

  In the second optical integrated circuit, the optical signal in the upstream direction passes through the four optical switches 80 as shown in FIG. 8, but if one optical switch can be realized with an excess loss of about 1 dB, it is about 4 dB. Can be realized with loss.

  In the third optical integrated circuit, it passes only through the multiplexer / demultiplexer 91 having no theoretical loss in the downstream direction, and is considered to have an excess loss of about 1 dB. As for the upstream direction, for example, when the optical branching device 91a branches an optical signal at a ratio of optical switch direction: photoreceiver direction = 4: 1, the theoretical loss is about 1 dB, and this is an excess loss of about 1 dB. Is estimated to result in a loss of about 2 dB in total.

  Note that the optical delay line 70 is a very short optical fiber, and therefore no loss is expected.

  In summary, in the active optical star coupler device according to the present invention shown in FIG. 8, the loss in the downstream direction is about 14 dB in total, and the loss in the upstream direction is about 7 dB in total.

  From the above, the active optical star coupler device according to the present invention of 16 × 16 has a large increase in the number of branches compared with the conventional 4 × 4 optical star coupler. It can be seen that the loss can be suppressed to the same level as that of the conventional 4 × 4 optical star coupler, and the loss increase in the downstream direction is about 7 dB compared to the conventional 4 × 4 optical star coupler.

  Therefore, when replacing the conventional 4 × 4 optical star coupler with the 16 × 16 active optical star coupler device according to the present invention, the necessary system change is that the transmission output of the light source of the optical transmitter of the OLT 130 is about 7 dB. It is only to increase.

  Therefore, even if the active optical star coupler device according to the present invention performs a number of branches, the multiplexed signal of the optical burst signal with a very small decrease in optical intensity is obtained for the upstream signal with respect to the normal optical star coupler. Therefore, in a concentrated optical communication system such as a PON system, there is a great effect in realizing an economical optical communication system that accommodates more ONUs in one OLT.

  The present invention is suitable as an active optical star coupler device.

20-2M, 85 Optical star couplers 40-4N, 50-5N, 60-6N Optical signal 80 Optical switch 81 Optical switch controller 82, 84 Signal line 83, 91-9M MUX / DEMUX 86 Autonomous control type optical concentrator switch 90 Light Concentration Switch 100 ~ 120 OLT
101 multiplexer / demultiplexer (in OLT)
102 Optical transmitter (within OLT)
103 Optical receiver (in OLT)
104 Control unit (within OLT)
105 High Power Optical Transmitter 200, 210-21N, 221-2N, 2M1-2MN Optical Fiber 310-3N0 ONU
311-3N1 multiplexer / demultiplexer (within OLT)
312-3N2 optical receiver (in OLT)
313-3N3 optical transmitter (within OLT)
314-3N4 control unit (in OLT)
800 Second optical output signal line (optical fiber)
850 First optical input signal line (optical fiber)
900 to 920 active optical star coupler device 911 to 9M1 first optical output signal line (optical fiber)
912 to 9M2 Second optical input signal line (optical fiber)
8021 to 802M Optical splitter 8031 to 803M Optical signal line (optical fiber)
8041 to 804M Light receivers 8051 to 805M, 8071 to 807M Signal lines 8061 to 806M Determinators 8081 to 808M Optical delay line (optical fiber)

Claims (4)

An optical star coupler having one first optical input signal line and M first optical output signal lines (M is an arbitrary integer greater than or equal to 2);
An optical switch having M second optical input signal lines and one second optical output signal line;
M first multiplexers / demultiplexers respectively connected to the first optical output signal lines and the second optical input signal lines;
The optical signal arriving at each of the second optical input signal lines is determined based on the time calculated by the OLT control unit that determines the transmission timing of the optical burst signal and calculates the time when the optical burst signal reaches the optical switch. An active optical star coupler device comprising: an optical switch control unit that controls the optical switch in accordance with a timing of a burst signal. The active optical star coupler device according to claim 1, further comprising a second multiplexer / demultiplexer connected to the first optical input signal line and the second optical output signal line. An optical star coupler having one first optical input signal line and M first optical output signal lines (M is an arbitrary integer greater than or equal to 2);
An optical switch having M second optical input signal lines and one second optical output signal line;
M first multiplexers / demultiplexers respectively connected to the first optical output signal lines and the second optical input signal lines;
An optical switch controller that controls the optical switch in accordance with the timing of an optical burst signal that arrives at each of the second optical input signal lines;
For each of the second optical input signal lines,
An optical branching device for bifurcating the optical burst signal;
A photoreceiver that receives one of the optical burst signals branched by the optical splitter and converts it into an electrical signal;
A determinator for determining from the electrical signal whether the optical burst signal has arrived at each of the second optical input signal lines;
After adding a certain delay to the other optical burst signal branched by the optical splitter, connected to an optical delay line to be input to the optical switch,
Each of the determiners detects the beginning and end of each of the optical burst signals,
The optical switch control unit controls switching of the optical switch based on detection of all the determination units , and when a plurality of the optical burst signals are duplicated, determination of a head of a new optical burst signal is performed. the preferentially, to transfer the optical burst signal to the second output signal line, you and controlling the switching of the optical switch, the active optical star coupler device. Each of the determiners is
Means for obtaining an integral value of the electrical signal output by the light receiver in a certain period;
The active optical star coupler device according to claim 3 , further comprising means for comparing the integrated value with a certain threshold value.

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