JP6523218B2 - Variable optical branching device - Google Patents

Description

  The present invention relates to a variable light branching apparatus used for light transmission.

  At present, for optical transmission from a base station to an end user, a system called PON (Passive Optical Network) (see Non-Patent Document 1 below) is widely used, and information is sent from the base station to each user through an optical fiber (FTTH: Fiber To The Home). In this PON system, a plurality of users are accommodated on one fiber on the base station side, and optical signals (including uplink / downlink) of a plurality of users on one optical fiber connected to the base station are received. A plurality of users are branched or joined by an optical branching device provided on the path to the user.

  In this conventional PON system shown in FIG. 1 (excerpted from FIG. 1 of Non-Patent Document 1 below), more users (ONU, UNI side) can be realized by one optical fiber from the base station (OLT, SNI side) It is required from the economical point of view to accommodate in a wider range (more distant from the base station).

Ryogo Kubo, et al, “Study and Demonstration of Sleep and Adaptive Link Rate Control Mechanisms for Energy Efficient 10G-EPON”, J. OPT. COMMUN. NETW. VOL. 2, NO. 9 / SEPTEMBER 2010, pp. 716-729 C.-H. Ji, et al., "Electromagnetic 2x2 MEMS optical switch," IEEE J Sel. Top. Quant., Vol. 10, no. 3, pp. 545-550, 2004.

  As described above, in the current PON system, in order to accommodate a plurality of users with a single optical fiber, an optical branching device for branching light is used. In FTTH, since the user changes in a fluid manner, the installation position of the light branching device, the ideal branching ratio in each light branching device, and the number of branches change in a fluid manner. Therefore, even when the first user is accommodated, it is usual to put the optical branching device on the communication path from the beginning.

  Therefore, if the number of branches and the like are changed after the installation of the optical branching device due to the addition or change of the user, it is necessary to perform the construction again at the installation position of the optical branching device. When the installation site is apart from the base station, for example, it is necessary to dispatch personnel, which increases costs, and also causes interruption time during which no signal is transmitted to the already accommodated user during construction.

  As a method of remotely changing the branching ratio and the number of branches of the optical branching device, there is a method of installing an optical switch which can be remotely controlled from the base station side in the optical branching device. The number of branches in the optical branching device can be changed by preparing in advance a plurality of optical branching devices having different branching ratios at branching points and changing the connection destination by switching with the optical switch for remote control. As a result, the output light intensity to the unconnected terminal can be reduced, and the optical signal can be efficiently sent to a distant place.

  However, in order to operate the optical switch by remote control, power for driving the optical switch is required, so power needs to be supplied to each branch point outside the base station, and power supply such as a power supply or a feeder line is supplied. Equipment installation costs and operation costs increase.

  That is, in the conventional PON system, in order to change the branching ratio in the optical branching device in the middle of the optical transmission path, there is a problem that the installation of a feeding facility having a large installation cost and operation cost is essential.

  The present invention has been made in view of such problems, and the object of the present invention is to make it possible to remotely change the branching ratio and the number of branching of the optical branching device in the optical transmission path while eliminating the need for power feeding equipment. To realize a variable optical branching device.

The present invention is characterized by having the following configuration in order to achieve such an object.
(Structure 1 of the Invention)
One or more input / output ports through which signal light is input / output,
A plurality of splitters that split or merge the signal light;
An optical switch unit that connects the signal light to the splitter according to the switch state;
A wavelength demultiplexing unit that demultiplexes control light for controlling the switch state of the optical switch unit according to its wavelength;
One or more light receiving units that receive the control light demultiplexed by the wavelength demultiplexing unit according to the wavelength thereof;
It has an optical power feeding unit that feeds the energy of the control light received by the light receiving unit to the optical switch unit and the control unit as electric power,
The control unit switches and controls the switch state of the optical switch unit according to the light receiving unit that has received the control light.
Variable light branching device characterized in that.

(Structure 2 of the Invention)
In the variable light branching device of configuration 1 of the invention,
The optical switch unit is constituted by two stages of a first optical switch unit and a second optical switch unit,
At the same time, the control unit controls the switch states of the first and second optical switch units in cooperation with one another, and a part of the signal light passing through the first optical switch unit is a splitter between stages And a path connected to another splitter via the second optical switch unit after being branched or merged by the
Variable light branching device characterized in that.

(Composition 3 of the Invention)
In the variable light branching device according to the first or second aspect of the invention,
The control light is input from the same input / output port as the input light together with the signal light.
The wavelength demultiplexing unit is connected to a subsequent stage of an input / output port to which the control light is input,
Variable light branching device characterized in that.

(Structure 4 of the Invention)
In the variable optical branching device of configuration 3 of the invention,
The wavelength demultiplexing unit
A splitter that splits input light from the input / output port into two;
And a wavelength dispersive element for wavelength-dividing at least one control light of the input light branched by the splitter,
The other of the input light branched by the splitter is input to the optical switch unit,
Variable light branching device characterized in that.

(Structure 5 of the Invention)
In the variable light branching device according to the first or second aspect of the invention,
The control light is input from a port different from the input / output port of the signal light,
An input / output port through which the signal light is input / output is directly connected to the optical switch unit,
A port to which the control light is input is connected to the wavelength demultiplexer.
Variable light branching device characterized in that.

(Structure 6 of the Invention)
In the variable optical branching device according to any one of the first to fifth aspects of the invention, the optical switch unit is configured of a self-holding type optical switch which holds a switch state with no power supply.
Variable light branching device characterized in that.

  As described above, according to the present invention, it is possible to make the branching ratio and the number of branches of the optical branching device in the optical transmission path variable from the distance while eliminating the need for a power supply facility.

It is a schematic diagram explaining the conventional PON system. It is a block diagram showing a variable light branching device of Example 1 of the present invention. FIG. 7 is a block diagram showing a variable light branching device according to a second embodiment of the present invention. It is a block diagram which shows another example of the variable optical branching device of Example 2 of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Example 1
As shown in FIG. 2, the variable optical branching device according to the first embodiment of the present invention includes control light (indicated by a white arrow with wavelength λc) and signal light (wavelength λs, from the base station side (left side in FIG. 2)). And an optical splitter (splitter) 102 that splits the input light into two.

  Further, the variable optical branching device of the first embodiment has a wavelength demultiplexer (wavelength dispersive element) 103 for dividing (splitting) the control light of one of the two branched input lights for each wavelength. The wavelength demultiplexer 103 and the above-described optical splitter 102 can be collectively referred to as a wavelength demultiplexer.

  Further, the variable light branching device according to the first embodiment uses the energy of the control light received by the light receiving unit as the power of the light receiving units 104-1 to 104-N that receive the branched control light according to the wavelength thereof. It has an optical feeding unit 105 for converting and feeding.

  Furthermore, the variable optical branching device according to the first embodiment receives the 1xN optical switch unit 106 that changes the connection destination of the signal light of the other input light branched into two by the optical branching device 102 in N switch states; The optical switch control unit 107 changes the connection destination of the optical switch unit 106 according to the wavelength of the control light, and N pieces of signal light are branched by an arbitrary number of branches on the output side of the optical switch unit 106 and connected to the user It is configured to include splitters 108-1 to 108-N.

  In the operation of the variable optical branching device according to the first embodiment of FIG. 2, the input light including the signal light λs and the control light λc input from the input port 101 is first input to the optical splitter 102 and branched into two. The at least control light of one input light branched into two is input to the wavelength demultiplexer (wavelength dispersive element) 103. The control light is further demultiplexed corresponding to the wavelength by the wavelength demultiplexing device (wavelength dispersion element) 103, received by the light receiving units 104-1 to 104-N according to the wavelength of the control light, and photoelectrically converted. Ru. The optical feed unit 105 supplies power to the optical switch unit 106 and the optical switch control unit 107 as an electrical control / drive signal, and the optical switch control unit 107 controls the optical switch unit 106 to operate in N switch states. can do.

  The feeding method from the light feeding unit 105 can be changed according to which light receiving unit 104-1 to 104-N receives the control light. For example, control lights of different wavelengths are output from different output ports of the wavelength demultiplexer (wavelength dispersion element) 103 and are received by different light receiving units 104-1 to 104-N. It is possible to feed at different ports of the optical switch control unit 107 through the path.

  It is associated with which port of the optical switch control unit 107 the power is supplied and what switch state the optical switch unit 106 takes. In response to this, the switch state of the optical switch unit 106 is changed from the switch state 1 to the switch state N according to a control signal from the optical switch control unit 107.

  By the change of the switch state, the optical splitters 108-1 to 108-N to which the signal light is connected are changed. As a result, it becomes possible to change the number and ratio of light branches of the light branching device remotely by the control light, and a variable light branching device can be realized. The setting of the state switching of the optical switch unit 106 is performed by changing the wavelength of the control light.

  The control light is not limited to a single wavelength, but may be encoded using a combination of a plurality of wavelengths and associated with N switch states. In this case, the light feeding unit 105 to the control unit 107 Although it is necessary to provide a function, the number of light receiving units 104 can be smaller than the number N of possible switch states. The wavelength of the control light may use a part of the wavelength band of the signal light.

  Furthermore, a branching ratio is required by using a self-holding type optical switch that requires power only at the time of switch state switching, such as the MEMS described in Non-Patent Document 2, and can hold the switch state without power supply. It is also possible to eliminate the need to transmit control light except when changing.

(Example 2)
In the variable optical branching apparatus according to the first embodiment of FIG. 2, when the number of branches is increased to accommodate a new user while the user is already accommodated, the connection to the already accommodated user is interrupted. there is a possibility. In such a case, by connecting the optical switch units 106 in multiple stages, it is possible to make the branching ratio and the number of branches variable while maintaining the state of connection to the user already accommodated. In the following second embodiment, the case where the number of multistages is 2 and the number of switch states is 2 will be described.

  The variable light branching device according to the second embodiment of the present invention shown in FIG. 3 includes an input port 101 to which input light including control light and signal light similar to the variable light branching device according to the first embodiment is input; An optical splitter 102 for branching, a wavelength demultiplexer 103 for demultiplexing control light of one of the bifurcated input light into each wavelength, and two light receiving sections 104-1 for receiving the demultiplexed control light And 104-2 and a light feeding unit 105 that feeds the energy of control light received by the light receiving unit as electric power.

  In particular, the variable optical branching device according to the second embodiment includes two (two-stage) optical switch units 106-1 and 106-2 that switch and change the connection destination of the other signal light of the two branched input light with 1x2 and 2x1. An optical branching unit 109 for branching the signal light into two between the stages of the two optical switch units, an optical switch control unit 107 for changing and controlling connection destinations of the two optical switch units according to the wavelength of the received control light, and a user The optical splitters 108-1 and 108-2 are configured to split the signal light by an arbitrary number of branches at the output side connected to the

  In the operation of the second embodiment, as in the first embodiment, first, the input light in which the signal light (wavelength λs) and the control light (wavelength λc) are wavelength-multiplexed is input to the optical splitter 102 via the input port 101. At least one control light of the input light branched into two by the light branching device 102 and branched into 2 is input to the wavelength demultiplexer (wavelength dispersion element) 103.

  Next, the control light is further branched corresponding to the wavelength by the wavelength demultiplexer (wavelength dispersion element) 103, and is received by the light receiving sections 104-1 and 104-2 according to the wavelength of the control light. Thus, the optical switch unit 106-1, 2 and the optical switch control unit 107 are supplied with power by the light feeding unit 105 and operated.

  The feeding method from the light feeding unit 105 changes depending on which light receiving unit 104-1 or 104-2 receives the control light. For example, control lights of different wavelengths are output from different output ports of the wavelength demultiplexer (wavelength dispersive element) 103 and are received by different light receiving units 104-1 and 104-2, so It is possible to feed different ports of the optical switch control unit 107 through the path.

  In the second embodiment, in particular, it is possible to associate which port of the optical switch control unit 107 receives power with which switch state the two optical switch units 106-1 and 106-2 take. It is. In response to this correspondence, the switch states of the two optical switch units 106-1 and 106-2 are simultaneously linked as shown by switch state 1 and switch state 2 in FIG. 3 by the control signal from the optical switch control unit 107. And change control.

  At this time, as shown in FIG. 3, in the switch state 1, the signal light λs is connected to only the output side optical splitter 108-1 in the upper path of the two-stage optical switch units 106-1 and 106-2. Connected to the user of the accommodation.

  On the other hand, in the switch state 2 of FIG. 3, the signal light λs is led to the inter-stage optical branching device 109 in the lower path of the first-stage optical switch unit 106-1 and branched there. . Then, the signal light λs branched upward by the interstage optical splitter 109 is guided to the output side optical splitter 108-1 along the path of the switch state 2 of the second stage optical switch unit 106-2, Connected to existing users. At the same time, the signal light λs branched downward by the inter-stage optical branching device 109 is directly led to the output side optical branching device 108-2 located between the stages, and connected to the newly accommodated user.

  Thus, a part of the signal light having passed through the first optical switch unit 106-1 is split or merged by the inter-stage splitter 109, and then separated via the second optical switch unit 106-2. A path connected to the splitter 108-1 is provided.

  Therefore, even in the switch state 2, the existing users accommodated under the optical splitter 108-1 in the switch state 1 are not interrupted by the change of the switch state for connection to the newly accommodated user. It is possible to maintain the housed state.

(Another form of Example 2)
In the second embodiment of FIG. 3, one-input two-output or two-input one-output optical switches are used as the optical switches 106-1 and 106-2. However, as another form of the second embodiment, N is 3 as shown in FIG. 4. In the case of natural numbers above, two (two stages) optical switch units 106-1 and 106-2 having one input N output or N input one output, and N-1 two-branch optical splitters 109 between the stages. By providing -1 to 109- (N-1) and the corresponding N-1 optical splitters 108-2 to 108-N for user output, it is possible to change the number of branches that can be changed and the branching ratio to three types. It is also easily possible to make the above switch states.

  Also in the embodiment of FIG. 4, the user accommodated under the optical branching device 108-1 in the switch state 1 is not interrupted even in the switch states 2 to N by the simultaneous cooperative control of the two stages of optical switches. It is possible to maintain the accommodated state, and at the same time, the user can be newly accommodated in the N-1 optical splitters 108-2 to 108-N for output between stages.

  In any of the above-described second embodiment, as in the first embodiment, by using a self-holding type optical switch that requires power only at the time of switch state switching such as MEMS and can maintain the switch state with no power supply. The need to transmit control light can be eliminated except when changing the number of branches.

Further, the point that the combination of a plurality of wavelengths can be used for the control light and the condition of the wavelength band of the control light are also the same as in the first embodiment.
(Other embodiments)
(Configuration of wavelength demultiplexing unit)
In each of the above-described embodiments, the optical branching unit 102 of the wavelength demultiplexing unit has been described as an element for branching input light such as a splitter with one input and two outputs, but this is a wavelength represented by AWG, for example It can also be configured by a splitter (wavelength dispersive element).

  In this case, it is also possible to configure the optical branching unit 102 as a single wavelength demultiplexing unit by constituting the wavelength demultiplexing element integrated with the wavelength demultiplexing unit 103 of the branching destination.

  When a splitter is used as the optical splitter 102, there is no restriction on the wavelength λc of the control light, and the wavelength band may be the same as or different from the wavelength λs of the signal light. Since the light is also branched, a loss of optical power of the signal light occurs.

  On the other hand, when a wavelength splitter is used for the optical splitter 102, it is desirable that the signal light and the control light be in different wavelength bands. In this case, the signal light and the control light depend on the wavelengths λs and λc. After demultiplexing, they can be connected to the optical switch unit 106 and the light receiving units 104-1 to 104-N, respectively. At this time, it becomes possible to separate the signal light carrying the signal and the control light responsible for power supply and switching trigger without loss of optical power.

(Control light input port)
In each of the embodiments described above, the control light is described as being input together with the signal light from the same input / output port 101 as the input light, but the control light input port is an input / output port to which the signal light is input / output Can be another different input port.

  In this case, the input / output port to which the signal light is input may be directly connected to the optical switch unit, and the input port to which the control light is input may be directly connected to the wavelength demultiplexing unit.

  Such a configuration can be realized, for example, by using a plurality of optical fibers on the base station side or using so-called multi-core optical fibers.

(Multi-stage connection of variable optical branching device)
By connecting the variable optical branching device itself in multiple stages, changes in the number of branches and the branching ratio can be adjusted in more stages.

  At this time, in the case of using a splitter as the optical branching device 102 of the wavelength demultiplexing unit of each stage of the variable optical branching device, use the same wavelength as control light of the variable optical branching device of the second and subsequent stages. Is possible. This is because the control light is also input to the optical switch unit by the splitter, and is output together with the signal light toward the variable light branching device of the next stage. However, in this case, it should be noted that the control light becomes weaker along with the signal light in the later stages.

  When a wavelength demultiplexer such as AWG is used as the optical splitter 102 of the wavelength demultiplexing unit of the variable optical splitter of each stage, it is necessary to make the wavelength of the control light used in each stage different. There is. This is because, if the wavelength of the control light is shared in each stage, the light of the wavelength used as the control light is demultiplexed in the AWG of the light branching section of the first stage variable optical branching device, and all variable optical branching devices in the first stage This is because the control light is not input to the subsequent variable light branching device because the light is input to the light receiving units 104-1 to 104-N.

(Bidirectionality of signal light)
Further, in all the embodiments described above, except for the control light including the light receiving unit in the path, the signal light can be transmitted by using the optical element capable of propagating the light bidirectionally (reversibly) on the path of the signal light. It is also possible to propagate in the reverse direction, and use the variable optical branching apparatus of the present invention in the upstream and downstream links of the network, or both. Referring to the figure, the shaded arrows of the signal light λs can be bi-directional arrows.

  In this case, with regard to signal light, the input port 101 and the connection ports of the optical splitters 108-1 to 108 connected to the user can be referred to as signal light input / output ports, respectively. The branching unit can be said to have one or more input / output ports through which signal light is input / output. The optical splitters 108 and 109 can also be referred to as splitters that split or merge signal light.

  As described above, the present invention can realize a variable optical branching device, and in particular, it is possible to make the branching ratio and the number of branching of the optical branching device in the optical transmission path variable from the remote, while eliminating the need for power feeding equipment. It becomes possible to apply to a network.

101 Input port (I / O port)
102 Optical splitter (splitter)
103 Wavelength demultiplexer (wavelength dispersive element)
104-1 to 104-N Photodetector
105 Optical power supply unit
106, 106-1, 106-2 Optical switch unit
107 Optical switch controller
108-1 to 108-N Optical splitter (splitter)
109, 109-1 to 109- (N-1) Optical splitter (splitter)

Claims (6)

One or more input / output ports through which signal light is input / output,
A plurality of splitters that split or merge the signal light;
An optical switch unit that connects the signal light to the splitter according to the switch state;
A wavelength demultiplexing unit that demultiplexes control light for controlling the switch state of the optical switch unit according to its wavelength;
One or more light receiving units that receive the control light demultiplexed by the wavelength demultiplexing unit according to the wavelength thereof;
It has an optical power feeding unit that feeds the energy of the control light received by the light receiving unit to the optical switch unit and the control unit as electric power,
The control unit switches and controls the switch state of the optical switch unit according to the light receiving unit that has received the control light.
Variable light branching device characterized in that. In the variable light branching device of claim 1,
The optical switch unit is constituted by two stages of a first optical switch unit and a second optical switch unit,
At the same time, the control unit controls the switch states of the first and second optical switch units in cooperation with one another, and a part of the signal light passing through the first optical switch unit is a splitter between stages And a path connected to another splitter via the second optical switch unit after being branched or merged by the
Variable light branching device characterized in that. The variable optical branching device according to claim 1 or 2
The control light is input from the same input / output port as the input light together with the signal light,
The wavelength demultiplexing unit is connected to a subsequent stage of an input / output port to which the control light is input,
Variable light branching device characterized in that. In the variable light branching device of claim 3,
The wavelength demultiplexing unit
A splitter that splits input light from the input / output port into two;
And a wavelength dispersive element for wavelength-dividing at least one control light of the input light branched by the splitter,
The other of the input light branched by the splitter is input to the optical switch unit,
Variable light branching device characterized in that. The variable optical branching device according to claim 1 or 2
The control light is input from a port different from the input / output port of the signal light,
An input / output port through which the signal light is input / output is directly connected to the optical switch unit,
A port to which the control light is input is connected to the wavelength demultiplexer.
Variable light branching device characterized in that. The variable optical branching device according to any one of claims 1 to 5, wherein the optical switch unit is constituted by a self-holding type optical switch which holds a switch state with no power supply.
Variable light branching device characterized in that.

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