JP2018006915A - Variable light branching apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable light branching apparatus configured to remotely vary a branching ratio and the number of branches of light branching devices in an optical transmission line while eliminating the need of a power supply facility.SOLUTION: A variable light branching apparatus comprises: one or more input/output ports to/from which a signal light is inputted/outputted; multiple splitters each for causing the signal light to be branched or confluent; an optical switch part for connecting the signal light to the splitter in accordance with its switch state; a wavelength demultiplexing part for demultiplexing a control light which controls the switch state of the optical switch part, in accordance with its wavelength; one or more light-receiving parts for receiving the control light which is demultiplexed by the wavelength demultiplexing part, in accordance with its wavelength; and an optical power supply part for supplying energy of the control light that is received by the light-receiving part, to the optical switch part and a control part as electric power. The control part is configured to changeover and control the switch state of the optical switch part in accordance with the light-receiving part that has received the control light.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a variable optical branching device used for optical transmission.

  Currently, a system called a PON (Passive Optical Network) (see Non-Patent Document 1 below) is widely used for optical transmission from a base station to an end user, 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. The optical branching device provided on the route with the user branches or merges with a plurality of users.

  In this conventional PON system shown in Fig. 1 (extracted from Fig. 1 of Non-Patent Document 1 below), a single optical fiber from the base station (OLT, SNI side) allows more users (ONU, UNI side). It is required from the viewpoint of economy to accommodate in a wider range (up to a place farther than 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, the current PON system uses an optical branching device that branches light in order to accommodate a plurality of users with a single optical fiber. In FTTH, the user changes in a fluid manner, and therefore the ideal branching ratio and the number of branches in the installation location of the optical branch device and each of the optical branch devices change in a fluid manner. For this reason, even when accommodating the first user, it is usual to place an optical branching device on the communication path from the beginning.

  Therefore, when the number of branches is changed by adding or changing a user after the optical branching device is installed, it is necessary to perform another work at the installation location of the optical branching device. When this installation location is away from the base station, it is necessary to dispatch personnel, which is not only costly, but also causes a non-interruption time during which the signal cannot be transmitted to the already accommodated users during construction.

  As a method of remotely changing the branching ratio and the number of branches of this optical branching device, there is a method of installing an optical switch that can be remotely operated 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 the branching locations, and changing the connection destination by switching with a remotely operated optical switch. As a result, the intensity of the output light to the unconnected terminal can be reduced, and an optical signal can be efficiently transmitted far away.

  However, in order to operate the optical switch by remote control, power for driving the optical switch is required, so it is necessary to supply power to each branch point outside the base station, and power supply such as a power supply or a power supply line is required. Equipment installation 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 it is essential to install a power supply facility with a large installation cost and operation cost.

  The present invention has been made in view of such a problem, and the object of the present invention is that the branching ratio and the number of branches of the optical branching device in the optical transmission line can be changed remotely while eliminating the need for power supply equipment. It is to realize a variable optical branching device.

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

(Configuration 2)
In the variable optical branching device of Configuration 1 of the invention,
The optical switch unit is composed of two stages of a first optical switch unit and a second optical switch unit,
A part of the signal light that has passed through the first optical switch unit is split between stages by simultaneously controlling the switch states of the first and second optical switch units in cooperation with the control unit. Having a path connected to another splitter via the second optical switch unit after being branched or merged by
A variable optical branching device characterized by that.

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

(Configuration 4)
In the variable optical branching device of Configuration 3 of the invention,
The wavelength demultiplexing unit is
A splitter that splits the input light from the input / output port into two branches;
A wavelength dispersive element configured to demultiplex 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.
A variable optical branching device characterized by that.

(Structure 5 of the invention)
In the variable optical 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,
The input / output port through which the signal light is input / output is directly connected to the optical switch unit,
The port to which the control light is input is connected to the wavelength demultiplexing unit.
A variable optical branching device characterized by that.

(Structure 6 of the invention)
In the variable optical branching device according to any one of configurations 1 to 5, the optical switch unit is configured by a self-holding optical switch that maintains a switch state with no power supply.
A variable optical branching device characterized by that.

  As described above, according to the present invention, it is possible to remotely change the branching ratio and the number of branches of the optical branching device in the optical transmission line while eliminating the need for power supply equipment.

It is a schematic diagram explaining the conventional PON system. It is a block diagram which shows the variable optical branching apparatus of Example 1 of this invention. It is a block diagram which shows the variable optical branching apparatus of Example 2 of this invention. It is a block diagram which shows another example of the variable optical branching apparatus 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 apparatus according to the first embodiment of the present invention includes control light (wavelength λc, indicated by a white arrow) and signal light (wavelength λs, An input port 101 to which input light including a shaded arrow is input, and an optical splitter (splitter) 102 that splits the input light into two.

  In addition, the variable optical branching apparatus according to the first embodiment includes a wavelength demultiplexer (wavelength dispersion element) 103 that divides (divides) the control light of one of the two branched lights into wavelengths. The wavelength demultiplexer 103 and the above-described optical branching device 102 are collectively referred to as a wavelength demultiplexing unit.

  In addition, the variable optical branching apparatus according to the first embodiment uses the light receiving units 104-1 to 104-N that receive the demultiplexed control light according to the wavelength and the energy of the control light received by the light receiving unit as power. An optical power feeding unit 105 that converts and feeds power is provided.

  Furthermore, the variable optical branching apparatus according to the first embodiment receives the 1 × N optical switch unit 106 that changes the connection destination of the signal light of the other input light that has been branched into two by the optical branching unit 102 in N switch states, and receives light. An optical switch control unit 107 that changes the connection destination of the optical switch unit 106 according to the wavelength of the control light, and N lights that branch the signal light at an arbitrary number of branches on the output side of the optical switch unit 106 and connect it to the user It has branching devices (splitters) 108-1 to 108-N.

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

  The power feeding method from the optical power feeding unit 105 can be changed depending on 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 supply power at different ports of the optical switch control unit 107 through the route.

  Which port of the optical switch control unit 107 supplies power and what switch state the optical switch unit 106 takes is associated with each other. 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 by a control signal from the optical switch control unit 107.

  The change of the switch state changes the optical branching devices 108-1 to 108-N to which the signal light is connected. As a result, it is possible to change the number of optical branches and the ratio of the optical branching device remotely from the control light, thereby realizing a variable optical branching device. The state switching setting 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 control light is decoded by the optical power feeding unit 105 or 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. Further, the wavelength of the control light may use a part of the wavelength band of the signal light.

  Further, by using a self-holding optical switch that requires power only when switching the switch state, such as MEMS disclosed in Non-Patent Document 2, and can maintain the switch state without a power source, 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 shown in FIG. 2, when the number of branches is increased in order 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, it is possible to make the branching ratio and the number of branches variable while maintaining the state of being connected to the already accommodated user by connecting the optical switch units 106 in multiple stages. In the following second embodiment, a case where the number of multistages is 2 and the switch state is 2 will be described.

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

  In particular, the variable optical branching apparatus according to the second embodiment has two (two-stage) optical switch units 106-1 and 106-2 that change the connection destination of the other signal light of the two-branched input light between 1x2 and 2x1. An optical branching unit 109 for branching the signal light between the two optical switch units, an optical switch control unit 107 for changing and controlling the connection destination of the two optical switch units according to the wavelength of the received control light, and a user Are provided with optical branching units 108-1 and 108-2 for branching the signal light with an arbitrary number of branches on the output side connected to.

  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. The optical branching device 102 splits the light into two, and at least one of the two branched light beams is input to a wavelength demultiplexer (wavelength dispersion element) 103.

  Next, the control light is further demultiplexed according to the wavelength by the wavelength demultiplexer (wavelength dispersion element) 103, and is received by the light receiving units 104-1 and 104-2 corresponding to the wavelength of the control light. Thus, the optical power feeding unit 105 feeds and operates the optical switch units 106-1 and 2 and the optical switch control unit 107.

  The power feeding method from the optical power feeding unit 105 varies depending on which light receiving unit 104-1, 104-2 receives the control light. For example, control lights having different wavelengths are output from different output ports of a wavelength demultiplexer (wavelength dispersion element) 103 and received by different light receiving units 104-1 and 104-2. It is possible to supply power to 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 supply and what switch state is taken by the two optical switch units 106-1 and 106-2. It is. In response to this association, the switch states of the two optical switch units 106-1 and 106-2 are simultaneously linked by the control signal from the optical switch control unit 107 as shown in the switch state 1 and the switch state 2 in FIG. And change control.

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

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

  As a result, a part of the signal light that has passed through the first optical switch unit 106-1 is branched or joined by the splitter 109 between the stages, and then separated through the second optical switch unit 106-2. A path connected to the splitter 108-1 is provided.

  Therefore, an already accommodated user accommodated under the optical branching unit 108-1 in the switch state 1 is not interrupted by the change of the switch state for connection to the newly accommodated user. The housed state can be maintained.

(Another embodiment of Example 2)
In the second embodiment of FIG. 3, an optical switch having one input and two outputs or two inputs and one output is 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. With the above natural numbers, two (two stages) optical switch sections 106-1 and 106-2 with one input and N outputs or N inputs and one output, and N−1 two-branch optical branching devices 109 between the stages. -1 to 109- (N-1) and N-1 optical splitters 108-2 to 108-N for user output corresponding to this, so that there are three types of branching ratios and branching ratios that can be changed It is also possible to easily create the above switch state.

  In the embodiment of FIG. 4 as well, the user who is accommodated under the optical branching unit 108-1 in the switch state 1 by the simultaneous cooperation control of the two-stage optical switch is not interrupted even in the switch states 2 to N. It is possible to maintain the accommodated state, and at the same time, a new user can be accommodated in N-1 optical branching units 108-2 to 108-N for output between stages.

  In any form of the second embodiment, as in the first embodiment, by using a self-holding optical switch that requires power only when switching the switch state, such as MEMS, and can maintain the switch state without a power source. The control light need not be transmitted except when the number of branches is changed.

The point that a combination of a plurality of wavelengths can be used for the control light and the conditions of the wavelength band of the control light are the same as in the first embodiment.
(Other embodiments)
(Configuration of wavelength demultiplexer)
In each of the above-described embodiments, the optical branching unit 102 of the wavelength demultiplexing unit has been described as an element that splits input light with one input and two outputs, such as a splitter. It can also be configured by a duplexer (wavelength dispersion element).

  In this case, the optical branching unit 102 may be configured by a wavelength dispersion element integrated with the branching wavelength demultiplexer 103 to form one wavelength demultiplexing unit.

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

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

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

  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 by, for example, using a plurality of optical fibers on the base station side or a so-called multi-core optical fiber.

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

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

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

(Bidirectional signal light)
Further, in all the embodiments described above, the signal light is transmitted by using an optical element capable of propagating light bidirectionally (reversibly) on the signal light path, except for the control light including the light receiving unit in the path. Propagating in the reverse direction, the variable optical branching device of the present invention can be shared by the upstream and downstream links of the network, or used as both. Regarding the figure, the shaded arrow of the signal light λs can be a bidirectional arrow.

  In this case, with respect to the signal light, the input port 101 and the connection ports of the optical splitters 108-1 to 108-N connected to the user can be referred to as signal light input / output ports, respectively. It can be said that the branching device has one or a plurality of input / output ports through which signal light is input / output. Further, the optical branching units 108 and 109 can be referred to as splitters that branch or merge signal lights.

  As described above, the present invention can realize a variable optical branching device, and in particular, an optical branching ratio and the number of branches of an optical branching device in an optical transmission line can be remotely changed while eliminating the need for a power supply facility. It can be applied to a network.

101 Input port (I / O port)
102 Optical splitter (splitter)
103 Wavelength demultiplexer (wavelength dispersion element)
104-1 to 104-N Receiver
105 Optical feeder
106, 106-1, 106-2 Optical switch
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 for branching or joining the signal light;
An optical switch unit for connecting the signal light to the splitter according to the switch state;
A wavelength demultiplexing unit for demultiplexing the control light for controlling the switch state of the optical switch unit according to the wavelength;
One or a plurality of light receiving units that receive the control light demultiplexed by the wavelength demultiplexing unit according to the wavelength;
An optical power feeding unit that feeds power to the optical switch unit and the control unit as energy of the control light received by the light receiving unit;
The control unit switches and controls a switch state of the optical switch unit according to the light receiving unit that has received the control light.
A variable optical branching device characterized by that. The variable optical branching device according to claim 1, wherein
The optical switch unit is composed of two stages of a first optical switch unit and a second optical switch unit,
A part of the signal light that has passed through the first optical switch unit is split between stages by simultaneously controlling the switch states of the first and second optical switch units in cooperation with the control unit. Having a path connected to another splitter via the second optical switch unit after being branched or merged by
A variable optical branching device characterized by 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 the subsequent stage of the input / output port to which the control light is input.
A variable optical branching device characterized by that. The variable optical branching device according to claim 3,
The wavelength demultiplexing unit is
A splitter that splits the input light from the input / output port into two branches;
A wavelength dispersive element configured to demultiplex 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.
A variable optical branching device characterized by 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,
The input / output port through which the signal light is input / output is directly connected to the optical switch unit,
The port to which the control light is input is connected to the wavelength demultiplexing unit.
A variable optical branching device characterized by that. The variable optical branching device according to any one of claims 1 to 5, wherein the optical switch unit includes a self-holding optical switch that maintains a switch state with no power supply.
A variable optical branching device characterized by that.

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