Optical network system and remote device

Abstract

To provide a technique for reducing light loss of a light source to improve energy efficiency.SOLUTION: In an optical network system, a center device 1 comprises a light source 101 which outputs light to a remote device 2 through an optical fiber. The remote device 2 comprises: a light path changeover switch 201 which changes a path of light output from the center device 1 to an optical coupler 204 or a photoelectric converter 202; an optical coupler 204 which branches the light input through the light path changeover switch 201 to the photoelectric converter 202 and an uplink communication mechanism 205; the photoelectric converter 202 which converts the light input through the light path changeover switch 201 or one of light beams branched by the optical coupler 204 into electricity; and an uplink communication mechanism 205 which uses the other light beam branched by the optical coupler 204 to generate an uplink signal to be transmitted to the center device 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an optical network system and a remote device. [Background Art]

[0002] In optical networks, optical power feeding via optical fibers has been proposed. An example of a network system using optical fiber power feeding is a sensor network. In a sensor network, a power feeding light source for supplying power is installed on the center side, an optical signal from the power feeding light source is transmitted to a plurality of node devices installed at remote locations to supply power, and wireless sensors or wired sensors are driven to acquire sensor information.

[0003] Non-Patent Documents 1 and 2 describe an optical power feeding type sensor network via optical fibers. [Prior Art Documents] [Non-Patent Documents]

[0004] [Non-Patent Document 1] Y. Tanaka, M. Kinoshita, A. Takahashi, and T. Kurokawa, “A wide-area sensor network based on fiber optic power supply,” Japanese Journal of Applied Physics, vol.50, no.11, ID112501, 2011 [Non-Patent Document 2] Y. Tanaka, S. Kobayashi, A. Shiomichi and T. Kurokawa, "Low power fiber sensor network deploying both wired and wireless sensors using optical power supply with WDM technique," 2016 IEEE Photonics Conference (IPC), 2016, pp. 819-820, doi: 10.1109 / IPCon.2016.7831080 [Overview of the project] [Problems that the invention aims to solve]

[0005] In the node device described in Non-Patent Document 1, a two-way optical coupler is used to separate the uplink and downlink communication paths. One branch is used to secure power to drive the node device and for downlink communication. The other branch is used for uplink communication. In this method, the optical signal output from the power supply light source is always split into two, but when uplink communication is not performed, unnecessary losses occur in the power supply light source, resulting in a decrease in energy efficiency.

[0006] Non-Patent Document 2 describes using a wavelength division multiplexer coupler to separate the uplink and downlink communication paths. Specifically, it avoids unnecessary optical loss in the power supply light source by separating the wavelength of the power supply light source from the wavelength used for uplink communication. However, Non-Patent Document 2 requires a separate uplink communication light source with a different wavelength in addition to the power supply light source.

[0007] This disclosure is made in view of the above circumstances, and the purpose of this disclosure is to provide a technology that reduces light loss from a light source and improves energy efficiency. [Means for solving the problem]

[0008] To achieve the above objective, one aspect of the present disclosure is an optical network system comprising a central device and a remote device, wherein the central device includes a light source that outputs light to the remote device via an optical fiber, and the remote device includes an optical path switching switch that switches the path of light output from the central device to an optical coupler or a photoelectric converter, an optical coupler that branches the light input via the optical path switching switch to the photoelectric converter and an uplink communication mechanism, a photoelectric converter that converts the light input via the optical path switching switch or one of the light branches from the optical coupler into electricity, and an uplink communication mechanism that generates an uplink signal to be transmitted to the central device using the other light branched from the optical coupler.

[0009] One aspect of the present disclosure is a remote device comprising: an optical path switching switch that switches the path of light output from a central device via an optical fiber to an optical coupler or a photoelectric converter; an optical coupler that branches the light input via the optical path switching switch to the photoelectric converter and an uplink communication mechanism; a photoelectric converter that converts the light input via the optical path switching switch, or one of the light branches from the optical coupler, into electricity; and an uplink communication mechanism that generates an uplink signal to be transmitted to the central device using the other light branched from the optical coupler. [Effects of the Invention]

[0010] According to this disclosure, it is possible to provide a technology that reduces light loss from a light source and improves energy efficiency. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 shows an example configuration of an optical network system according to an embodiment. [Figure 2] Figure 2 shows an example configuration of an optical network system in the first modified example. [Figure 3] Figure 3 shows an example configuration of an optical network system in the second modified example. [Modes for carrying out the invention]

[0012] Embodiments of this disclosure will be described with reference to the attached drawings. The embodiments described below are examples of the disclosure, and the disclosure is not limited to these embodiments. In this specification and in the drawings, components with the same reference numerals refer to the same components.

[0013] <Embodiment> Figure 1 shows an example configuration of an optical network system according to an embodiment of the present invention. The illustrated optical network system comprises a central device 1 (internal node) and a plurality of remote devices 2 (external nodes). The upstream central device 1 and the plurality of remote devices 2 downstream are connected via an optical fiber 4. In this embodiment, the direction from the remote devices 2 to the central device 1 is described as the "upstream direction," and the direction from the central device 1 to the remote devices 2 is described as the "downstream direction."

[0014] The central device 1 is installed in an environment where power can be secured (for example, inside a communications building) and is powered by optical fiber. Specifically, the central device 1 outputs light for power supply to the remote device 2 via optical fiber 4.

[0015] The illustrated center device 1 comprises a light source 101 that outputs light, a modulator 102, a light circulator 103, a light receiver 104, and a control unit 105. In the following description, light will also be referred to as an optical signal.

[0016] The optical circulator 103 splits the optical signal in the downstream direction (hereinafter referred to as the "downstream signal") and the optical signal in the upstream direction (hereinafter referred to as the "upstream signal"). The downstream and upstream signals are split via the optical circulator 103, and a single optical fiber 4 can connect the central device 1 and the remote device 2.

[0017] The light source 101 outputs light to the remote device 2 via the optical fiber 4. The light source 101 is, for example, a laser diode or the like, and emits laser light. The light emitted from the light source 101 is input to the optical fiber 4 via the modulator 102 and the optical circulator 103. The wavelength of the laser light is, for example, from 1480 nm to 1490 nm. Further, the power of the laser light output from the light source 101 is, for example, approximately +10 to 17 dBm. In the present embodiment, the light source 101 for power feeding is used to transmit and receive a downlink signal and an uplink signal.

[0018] The modulator 102 (intensity modulator) modulates the light output from the light source 101 under the control of the control unit 105 to generate a downlink signal, superimposes the downlink signal on the power feeding light, and outputs the resultant signal to the remote device 2. Note that although the illustrated example uses an external modulation scheme in which the light source 101 and the modulator 102 are separated, a direct modulation scheme may also be used. For example, the light source 101 may be configured as an internally modulated laser having a modulation function.

[0019] The light receiver (photoelectric converter) 104 receives the uplink signal output from the remote device 2 via the optical fiber 4, converts the uplink signal into an electrical signal, and outputs the electrical signal to the control unit 105. The uplink signal includes, for example, detection information detected by the sensor device 5, the stored power amount of the power storage unit 203 of the remote device 2, and the like. A light receiving element such as a photodiode is used for the light receiver 104.

[0020] The control unit 105 (first control unit) executes various types of control. For example, the control unit 105 transmits a modulation signal to the modulator 102 via the signal line 106, and superimposes the control signal (downlink signal) to the remote device 2 on the power feeding light output from the light source 101. Examples of the control signal include a drive instruction for the sensor device 5, an instruction related to power feeding such as start / stop of power feeding, and an inquiry about the stored power amount of the power storage unit 203. The control unit 105 of the present embodiment may instruct the remote device 2 to switch the optical path switching switch 201 as the control signal.

[0021] Further, the upstream signal output from the optical receiver 12 via the control unit 105 and the signal line 107 may be received, and detection information detected by the sensor device 5 included in the upstream signal may be transmitted to the control system 6. The control system 6 is a system that controls and manages the optical network system.

[0022] In the present embodiment, a plurality of remote devices 2 are connected to the center device 1 via optical fibers 4. Therefore, the optical network system of the present embodiment includes at least one optical coupler 3 disposed on the optical fiber 4. In the example shown in FIG. 1, a plurality of remote devices 2 are connected in series to the center device 1 via the optical fiber 4 and the optical coupler 3. Accordingly, power can be supplied to the plurality of remote devices 2 by one light source 101 of the center device 1, and the plurality of remote devices 2 can be driven.

[0023] The optical coupler 3 splits the light output from the center device 1 to the optical fiber 4 into a corresponding remote device 2 (first remote device) and another remote device 2 in the downstream direction (second remote device). Here, the optical coupler 3 is disposed on the optical fiber 4 for each remote device 2, and splits the light in the optical fiber 4 into an optical path switch 201 of the corresponding remote device 2 and the downstream optical fiber 4.

[0024] The remote device 2 is a device connected to the center device 1 via the optical fiber 4 and capable of storing electricity through optical power feeding. Therefore, the remote device 2 can be installed in a place without a power supply.

[0025] The illustrated remote device 2 includes an optical path changeover switch 201, a photoelectric converter 202, a power storage unit 203, an optical coupler 204, an upstream communication mechanism 205, and a control unit 208.

[0026] The optical path changeover switch 201 switches the path of light output from the center device 1 via the optical coupler 3 to the optical coupler 204 or the photoelectric converter 202. That is, in the remote device 2 of the present embodiment, the optical path changeover switch 201 is provided at a preceding stage of the optical coupler 204.

[0027] For example, the optical path switching switch 201 switches the optical path to the photoelectric converter 202 when it does not transmit an uplink signal to the central device 1. Specifically, when the remote device 2 does not perform uplink communication, the optical path switching switch 201 sets the path so that all the light from the light source 101, which is branched by the optical coupler 3, is directed to the photoelectric converter 202.

[0028] In this case, the light output from the light source 101 is entirely converted into power to drive the remote device 2 by the photoelectric converter 202 of the remote device 2. The converted power is stored in the power storage unit 203, and the stored power is used to drive the sensor device 5 and various parts within the remote device 2. The path setting (path switching) of the light path switching switch 201 is performed by the control unit 208 via the signal line 211.

[0029] On the other hand, when the optical path switching switch 201 transmits an uplink signal to the central device 1, it switches the optical path to the optical coupler 204. Specifically, when the remote device 2 performs uplink communication, the optical path switching switch 201 sets the path so that the light from the light source 101, which is branched by the optical coupler 3, is guided to the optical coupler 204.

[0030] In this embodiment, a 2-input 2-output optical path switching switch 201 is used. When the remote device 2 is not performing uplink communication, the 2-input 2-output optical path switching switch 201 is set to a bar configuration as shown by the solid line, and the optical path output from the optical coupler 3 is connected to the photoelectric converter 202. On the other hand, when the remote device 2 is performing uplink communication, the 2-input 2-output optical path switching switch 201 is set to a cross configuration as shown by the dotted line, and the optical path output from the optical coupler 3 is connected to the optical coupler 204. In this case, one of the optical paths branched at the optical coupler 204 is guided to the photoelectric converter 202 via the optical path switching switch 201, and the other optical path is guided to the uplink communication mechanism 205.

[0031] By using a 2-input, 2-output optical path selector switch, the optical path can be switched with a single switch, thereby reducing power consumption.

[0032] The optical coupler 204 splits the light input via the optical path switching switch 201 to the photoelectric converter 202 and the uplink communication mechanism 205. The optical coupler 204 is, for example, a branch ratio coupler, and splits more of the optical power of the downlink light output from the center device 1 to the photoelectric converter 202 with a branch ratio such as 90:10 or 99:1.

[0033] The photoelectric converter 202 converts light input via the optical path switching switch 201, or one of the light branches off from the optical coupler 204, into electricity. The photoelectric converter 202 uses a photoelectric conversion element capable of receiving the wavelength of the laser light emitted by the light source 101. The photoelectric conversion element is made of readily available elements suitable for the long wavelength band of 1300nm to 1600nm used for communications, such as indium gallium arsenide, with an open-circuit voltage of 5V or less and a conversion efficiency of about 30%. The wavelength of the light emitted by the light source 101 of the center device 1 is set to the wavelength corresponding to the photoelectric conversion element used in the photoelectric converter 202.

[0034] The photoelectric conversion element is, for example, an optical power converter. Furthermore, if the power of the laser light transmitted through the optical fiber 4 is, for example, around 2mW, it can be used for optical power supply. Note that this power will vary depending on the device used for optical power supply.

[0035] The energy storage unit 203 stores the electrical energy converted by the photoelectric converter 202. For example, an electric double-layer capacitor can be used in the energy storage unit 203. Furthermore, the supply voltage to each active element can be adjusted as appropriate using a boost circuit (such as a DC / DC converter).

[0036] The light with the lower optical power, which is branched off from the optical coupler 204, is guided to the uplink communication mechanism 205. The uplink communication mechanism 205 uses the other light branched off from the optical coupler 204 to generate an uplink signal to be transmitted to the central device 1. The uplink communication mechanism 205 may also generate an uplink signal that includes detection information detected by the sensor device 5.

[0037] The uplink communication mechanism 205 includes a reflective optical switch 206 (1-input, 1-output optical switch) that performs modulation synchronized with the signal from the control unit 208, and a reflector 207. The uplink communication mechanism 205 generates modulated light by modulating the light branched by the optical coupler 204 using the optical switch 206. Specifically, the control unit 208 controls the optical switch 206 via the signal line 213, and generates modulated light by reflecting or dereflecting the light from the light source 101 with the reflector 207 according to the transmitted data.

[0038] The generated modulated light is output to the center device 1 via the optical fiber 4 as an uplink signal to the center device 1. The modulated light input to the center device 1 is converted into an electrical signal by the photodetector 104 via the optical circulator 103 and output to the control unit 105.

[0039] The uplink communication mechanism 205 is preferably one that operates at a low voltage and with very low power consumption of a few μW or less. For example, an electrostatically driven MEMS optical switch, which has low drive power and is generally available, can be used.

[0040] The control unit 208 (second control unit) controls each active element, such as the optical path switching switch 201 and the optical switch 206 of the uplink communication mechanism 205, and the sensor device 5. The control unit 208, each active element, and the sensor device 5 are connected via signal lines 211 to 214. For example, a microprocessor can be used in the control unit 208. For example, the control unit 208 may control the switching of the optical path switching switch 201 according to instructions from the control unit 105 of the center device 1.

[0041] The control unit 208 analyzes the downstream signal contained in the light received by the photoelectric converter 202. Based on the control of the control unit 105, the light source 101 of the center device 1 has its output laser light subjected to intensity modulation, resulting in an informational downstream signal such as a TTL (Time to Live) or CMOS signal. The downstream signal includes various control signals such as instructions to the sensor device 5, power supply control, and switching instructions for the optical path switching switch 201.

[0042] The control unit 208 generates an uplink signal by controlling the optical switch 206 of the uplink communication mechanism 205. For example, the control unit 208 may operate the sensor device 5 according to a control signal from the central device 1, generate an uplink signal using the uplink communication mechanism 205 from the detection information detected by the sensor device 5, and output it to the central device 1. The control unit 208 may also control the power supply from the energy storage unit 203 to the sensor device 5. In this way, the control unit 208 can communicate with the central device 1 to operate the sensor device 5 with the power from the energy storage unit 203 and acquire detection information.

[0043] The remote device 2 of this embodiment can transmit detection information from a sensor device 5 installed in an underground manhole, an overhead closure, or other location where it is difficult to secure a power source, to the central device 1 using power supplied by optical power.

[0044] The control unit 208 may also monitor the amount of stored energy in the energy storage unit 203 using an AD converter (not shown) or the like provided by the control unit 208. For example, the control unit 208 may acquire the voltage of the energy storage unit 203 according to a control signal from the central device 1, generate an uplink signal of the acquired voltage value using the uplink communication mechanism 205, and output it to the central device 1 via the optical fiber 4.

[0045] The sensor device 5 is driven using the power stored in the energy storage unit 203. The sensor device 5 is electrically connected to the control unit 208 of the remote device 2 via signal lines and power lines 214. The sensor device 5 operates using the power from the energy storage unit 203 according to the control of the control unit 208, detects predetermined information, and transmits the detected information to the control unit 208. A wide variety of sensor devices can be used in the sensor device 5, such as a temperature sensor, humidity sensor, motion sensor, tilt sensor, water level sensor, etc. Note that the sensor device 5 may also be a device that has a built-in energy storage unit and is driven by its own power supply.

[0046] In this way, during downlink communication, where data is transmitted from the central device 1 to the remote devices 2, the control unit 105 controls the modulator 102 via the signal line 106 to perform intensity modulation on the output light of the power supply light source 101. The intensity-modulated downlink signal propagates through the optical circulator 103 and optical fiber 4, and is then delivered to each remote device 2 by the optical coupler 3. The downlink signal delivered to the remote devices 2 passes through the optical path switching switch 201 and is then converted into an electrical signal by the photoelectric converter 202. The downlink signal (data) transmitted in downlink communication is received by the control unit 208 by monitoring the voltage of the photoelectric converter 202 via the signal line 212.

[0047] In uplink communication, where data is transmitted from the remote device 2 to the central device 1, the path of the optical path switching switch 201 is set so that the light from the power supply light source 101 passes through the optical coupler 204. As a result, the light from the light source 101, which is branched at the optical coupler 3, is further split at the optical coupler 204 into the photoelectric converter 202 and the uplink communication mechanism 205. In this state, the control unit 208 controls the optical switch 206 via the signal line 213 to reflect or dereflect the light from the light source 101 according to the data to be transmitted. The reflected light sequentially passes through the optical coupler 204, the optical path switching switch 201, the optical coupler 3, the optical fiber 4, and the optical circulator 103, is converted into an electrical signal by the light receiver 104, and then received by the control unit 105.

[0048] The optical network system of this embodiment described above comprises a central device 1 and a remote device 2. The central device 1 includes a light source 101 that outputs light to the remote device 2 via an optical fiber 4. The remote device 2 includes an optical path switching switch 201 that switches the path of light output from the central device 1 to an optical coupler 204 or a photoelectric converter 202, an optical coupler 204 that branches the light input via the optical path switching switch 201 to the photoelectric converter 202 and an uplink communication mechanism 205, a photoelectric converter 202 that converts the light input via the optical path switching switch 201, or one of the light branches from the optical coupler 204, into electricity, and an uplink communication mechanism 205 that generates an uplink signal to be transmitted to the central device 1 using the other light branched from the optical coupler 204.

[0049] As described above, the remote device 2 of this embodiment is equipped with an optical path switching switch 201 before the two-branch optical coupler 204. This allows the optical coupler 204 to branch the optical signal output from the power supply light source 101 only when uplink communication is required, thereby configuring an optical path for uplink communication. On the other hand, when uplink communication is not required, the weak optical energy transmitted through the optical fiber 4 can be supplied 100% as power to drive the remote device 2.

[0050] Therefore, in this embodiment, the optical loss of the power supply light source can be reduced, and energy efficiency can be improved. In other words, it is possible to prevent a decrease in energy efficiency due to unnecessary losses in the power supply light source without having to provide a separate light source for uplink communication of a different wavelength.

[0051] <First variation> Figure 2 shows the configuration of a first modified example of the optical network system shown in Figure 1. In this modified optical network system, one remote device 2 is connected to the central device 1.

[0052] The optical network system shown in Figure 2 differs from the optical network system shown in Figure 1 in that it does not have an optical coupler 3 arranged on the optical fiber 4. In this embodiment, the light output from the central device 1 is input to the remote device 2 via the optical fiber 4. Otherwise, it is the same as in Figure 1. That is, the central device 1 and remote device 2 in this embodiment are the same as the central device 1 and remote device 2 in the first embodiment.

[0053] <Second variation> Figure 3 shows the configuration of a second modified example of the optical network system shown in Figure 1. In the above embodiment, a 2-input 2-output optical path switching switch was used for the optical path switching switch 201, but it is not limited to this. For example, a 1-input 2-output optical path switching switch 201A may be used as shown in Figure 3. In this case, a 2-input 1-output optical path switching switch 201B is provided between the 1-input 2-output optical path switching switch 201A and the photoelectric converter 202. The optical coupler 204 branches the light output from the 1-input 2-output optical path switching switch 201A to the 2-input 1-output optical path switching switch 201B and the uplink communication mechanism 205.

[0054] The 1-input 2-output optical path switching switch 201A switches the optical path output from optical coupler 3 to photoelectric converter 202 when the remote device 2 is not performing uplink communication, and switches the optical path output from optical coupler 3 to optical coupler 204 when the remote device 2 is performing uplink communication.

[0055] The 2-input 1-output optical path switching switch 201B switches the path so that the light from the 1-input 2-output optical path switching switch 201A is input to the photoelectric converter 202 when the remote device 2 is not performing uplink communication, and switches the path so that the light from the optical coupler 204 is input to the photoelectric converter 202 when the remote device 2 is performing uplink communication.

[0056] The control unit 208 sends control signals via the signal line 211 to switch the 1-input 2-output optical path switching switch 201A and the 2-input 1-output optical path switching switch 201B in an interlocking manner.

[0057] In the control unit 105 of the central device 1 and the control unit 208 of the remote device 2 in the above-described embodiment and modified examples, a general-purpose computer system can be used, for example. The computer system comprises a CPU (Central Processing Unit, processor), memory, storage (HDD: Hard Disk Drive, SSD: Solid State Drive), communication device, input device, and output device. Memory and storage are storage devices. In this computer system, the functions of the control unit 105 or control unit 208 are realized by the CPU executing a predetermined program loaded into memory. The program of the control unit 105 or control unit 208 can be stored on a computer-readable recording medium such as an HDD, SSD, USB (Universal Serial Bus) memory, CD (Compact Disc), or DVD (Digital Versatile Disc), or distributed via a network. A computer-readable recording medium is, for example, a non-transitory recording medium.

[0058] This disclosure is not limited to the embodiments described above, and numerous modifications are possible within the scope of its essence. [Explanation of Symbols]

[0059] 1: Center device 101: Light source 102: Modulator 103: Light Circulator 104:Receiver 105: Control Unit (First Control Unit) 2: Remote device 201: Optical path switching switch 202: Photoelectric Converter 203: Energy Storage Unit 204: Optical coupler 205: Uplink Communication Mechanism 206: Optical switch 207:Reflector 208: Control Unit (Second Control Unit) 3: Optical coupler (other optical coupler) 4: Fiber optic 5: Sensor device 6: Control System

Claims

1. An optical network system comprising a central device and a remote device, The aforementioned center device is The device includes a light source that outputs light to the remote device via an optical fiber, The remote device is An optical path switching switch that switches the path of light output from the aforementioned center device to an optical coupler or photoelectric converter, The optical coupler, which branches the light input via the optical path switching switch to the photoelectric converter and the uplink communication mechanism, A photoelectric converter that converts the light input via the optical path switching switch, or one of the light branches off from the optical coupler, into electricity, The system includes an uplink communication mechanism that generates an uplink signal to be transmitted to the central device using the other optical fiber branched from the optical coupler. Optical network system.

2. The optical path switching switch switches the optical path to the optical coupler when transmitting the upstream signal to the center device, and switches the optical path to the photoelectric converter when not transmitting the upstream signal to the center device. The optical network system according to claim 1.

3. The aforementioned optical path switching switch is a two-input, two-output path switching switch. The optical network system according to claim 1.

4. Equipped with multiple remote devices, The optical coupler also provides a way to split the light output from the central device to the optical fiber to a first remote device and a second remote device. The optical network system according to claim 1.

5. The aforementioned uplink communication mechanism generates an uplink signal that includes detection information detected by the sensor device. The optical network system according to claim 1.

6. The aforementioned center device is The system includes a first control unit that instructs the remote device to switch the optical path switching switch, The remote device is The system includes a second control unit that controls the switching of the optical path switching switch according to instructions from the first control unit. The optical network system according to claim 1.

7. It is a remote device, An optical path switching switch that switches the path of light output from the central device via optical fiber to an optical coupler or photoelectric converter, The optical coupler, which branches the light input via the optical path switching switch to the photoelectric converter and the uplink communication mechanism, A photoelectric converter that converts the light input via the optical path switching switch, or one of the light branches off from the optical coupler, into electricity, The system includes an uplink communication mechanism that generates an uplink signal to be transmitted to the central device using the other optical fiber branched from the optical coupler. Remote control device.

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