Optical power supply method and optical power supply system

Abstract

This optical power feeding method has: a step in which a light source transmits light for optical power feeding to an optical power feeding line connected to an optical power feeding unit; a step in which an amplifier installed midway in the route of the optical power feeding line amplifies the light transmitted from the light source; and a step in which the optical power feeding unit receives the light amplified by the amplifier, converts the light into optical power, and obtains electrical power.

Description

[Technical Field]

[0001] The present invention relates to an optical power supply method and an optical power supply system. [Background technology]

[0002] There is a technology that uses optical power transmission to increase the amount of power supplied to devices at the receiving end in order to operate them for a long period of time. The devices at the receiving end here refer to electronic devices such as IoT devices installed deep in forests, underground, inside drainage pipes or manholes, for example. The surrounding environment of such devices is likely to be difficult to harvest energy from sunlight or outside the coverage area of ​​mobile phones. Furthermore, the devices are likely to be installed far from the light source of the optical power transmission.

[0003] Fig. 15 is a diagram showing an example of the configuration of an optical power supply system using a conventional optical power supply method. As shown in Fig. 15, in the conventional optical power supply method, light is transmitted from a light source provided in a central office or the like to an optical power supply unit installed in a target area to be supplied with power, which is, for example, a non-electrified area, via an optical power supply line using optical fiber. As a network configuration of the optical power supply line, for example, an SS (Single Star) configuration without branching is used to reduce branching loss. In the target area to be supplied with power, the light transmitted via the optical power supply line is received by a photodiode (PD) of the optical power supply unit. The received light is converted into an electrical signal, and power is supplied to target devices in the target area to be supplied with power. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Ryota Kita, Yoichi Fukada, Hiroaki Katsurai, Tomoaki Yoshida, “Prototype of Optical Power Supply Device for IoT Terminals and Evaluation of Power Balance During Intermittent Operation”, IEICE General Conference, B-8-12, March 2022 [Non-patent document 2] Keiji Takeuchi, “Special Feature: Energy Harvesting (Environmental Power Generation) Latest Trends in Energy Harvesting”, Surface Technology, Vol. 17, No. 7, pp. 334-338, NTT Data Institute of Management Consulting, 2016, [Retrieved August 30, 2022], Internet (URL: https: / / www.jstage.jst.go.jp / article / sfj / 67 / 7 / 67_334 / _pdf / -char / ja) Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional optical power supply methods provide a smaller amount of power compared to general power supply methods that use, for example, commercial power sources or metal wires. FIG. 16 is a schematic diagram showing the amount of power supplied by an optical power supply system using a conventional optical power supply method. As shown in FIG. 16, in conventional optical power supply methods, the greater the distance between the light source and the optical power supply unit, the greater the optical fiber loss in the optical power supply line, resulting in a smaller amount of power supply. Therefore, when the distance between the light source and the optical power supply unit is long, conventional optical power supply methods may not be able to supply enough power to operate devices in the power supply area. To address this issue, one approach would be to increase the amount of power supply by, for example, increasing the light output of the light source. However, this approach poses a problem: the optical fiber may overheat due to, for example, a fiber fuse phenomenon, potentially compromising safety.

[0006] The present invention has been made in view of the above-described technical background, and has an object to provide a technique that can increase the amount of power supply in optical power feeding without compromising safety. [Means for solving the problem]

[0007] One aspect of the present invention is an optical power supply method including the steps of: a light source transmitting light for optical power supply to an optical power supply line connected to an optical power supply unit; an amplifier installed midway along the optical power supply line amplifying the light transmitted from the light source; and the optical power supply unit receiving the light amplified by the amplifier and photoelectrically converting the light to obtain electric power.

[0008] Another aspect of the present invention is an optical power supply system having a light source that transmits light for optical power supply to an optical power supply line connected to an optical power supply unit, an amplifier that is installed along the path of the optical power supply line and amplifies the light transmitted from the light source, and the optical power supply unit that receives the light amplified by the amplifier and performs photoelectric conversion of the light to obtain electric power. [Effects of the Invention]

[0009] According to the present invention, it is possible to increase the amount of power supply in optical power feeding without compromising safety. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing the overall configuration of an optical power supply system 1 according to a first embodiment of the present invention. [Figure 2] 1 is a schematic diagram showing the amount of energy in an optical fiber in an optical power supply system 1 according to a first embodiment of the present invention. [Figure 3] FIG. 10 is a diagram illustrating the overall configuration of an optical power supply system 1a according to a second embodiment of the present invention. [Figure 4] FIG. 10 is an overall configuration diagram of an optical power supply system 1b according to a third embodiment of the present invention. [Figure 5] 10 is a flowchart showing the operation of a switch control unit 42 of an optical power supply system 1b according to the third embodiment of the present invention. [Figure 6] FIG. 10 is a diagram illustrating the overall configuration of an optical power supply system 1c according to a fourth embodiment of the present invention. [Figure 7] FIG. 10 is a diagram showing the overall configuration of an optical power supply system 1d according to a fifth embodiment of the present invention and the amount of energy in an optical fiber. [Figure 8] FIG. 10 is an overall configuration diagram of an optical power supply system 1e according to a sixth embodiment of the present invention. [Figure 9] 13 is a flowchart showing the operation of the optical power supply system 1e according to the sixth embodiment of the present invention. [Figure 10] FIG. 13 is a diagram illustrating the overall configuration of an optical power supply system 1f according to a seventh embodiment of the present invention. [Figure 11] FIG. 13 is a diagram illustrating the overall configuration of an optical power supply system 1g according to an eighth embodiment of the present invention. [Figure 12] 1 is a diagram illustrating an embodiment of the present invention. [Figure 13] 1 is a diagram illustrating an example of an optical power supply system according to an embodiment of the present invention; [Figure 14] 1 is a diagram illustrating an example of an optical power supply system according to an embodiment of the present invention; [Figure 15] FIG. 1 is a diagram illustrating an example of the configuration of an optical power supply system using a conventional optical power supply method. [Figure 16] FIG. 1 is a schematic diagram showing the amount of power supplied by an optical power supply system using a conventional optical power supply method. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an optical power supply method and an optical power supply system according to an embodiment will be described with reference to the drawings.

[0012] First Embodiment A first embodiment of the present invention will be described below.

[0013] [Configuration of optical power supply system] The configuration of the optical power supply system 1 according to the first embodiment will be described below. Fig. 1 is an overall configuration diagram of the optical power supply system 1 according to the first embodiment of the present invention. The optical power supply system 1 is a system for supplying power by optical power to devices present in a target power supply area (hereinafter referred to as "target power supply devices"). The target power supply area in this embodiment is, for example, a non-electrified area.

[0014] The power supply target device is, for example, an electronic device such as an IoT device installed deep in a forest, underground, inside a drainage pipe or manhole, etc. The surrounding environment of such a device is expected to be, for example, where it is difficult to generate energy using sunlight or the like, or outside of a mobile phone communication area. In addition, the device is expected to be installed far from the optical power source. As shown in FIG. 1 , the optical power supply system 1 includes a light source 11, an optical power supply unit 20, an amplifier 31, an energy harvester 32, and an optical power supply line 51.

[0015] The light source 11 is installed in a building such as a station building of a communications base station. This station building is located in an electrified area, for example, far away from the area to be powered. The light source 11 emits light for optical power feeding and transmits it to the optical power feeding line 51. For example, light that is always on may be used as the light for optical power feeding. The light transmitted by the light source 11 is transmitted to the optical power feeding unit 20 via the optical power feeding line 51. The optical power feeding line 51 is configured using optical fiber. For example, a single star (SS) configuration without branching is used as the network configuration of the optical power feeding line 51 in order to reduce branching loss.

[0016] The optical power supply unit 20 is installed, for example, inside or near the power supply target area. The optical power supply unit 20 includes, for example, a PD (Photodiode) (not shown). Light emitted by the light source 11 is received by the PD of the optical power supply unit 20. The optical power supply unit 20 converts the received light into an electrical signal and supplies power to the power supply target device.

[0017] The amplifier 31 is an optical amplifier that replenishes (amplifies) the energy lost due to optical fiber loss during optical transmission in the optical power supply line 51. In this embodiment, the amplifier 31 is located, for example, in a non-electrified area, and is driven by power generated by the energy harvester 32.

[0018] The energy harvesting power generator 32 may be, for example, a device using one of the various energy harvesting technologies described in Non-Patent Document 2. The various energy harvesting technologies are technologies that obtain power using, for example, photovoltaic power generation (solar cells), the piezoelectric effect, or electromagnetic induction. In other words, harvesting technology is a technology that harvests scarce energy that exists in various forms in the surrounding environment, such as light, vibration, heat, and radio waves, and converts it into power. By using the energy harvester 32, it becomes possible to install the amplifier 31 even in non-electrified areas.

[0019] The amount of energy replenished by the amplifier 31 is determined by taking into consideration not only the optical fiber loss but also the amplifier connection loss (amplifier connection loss) that occurs when the amplifier 31 is connected to the optical power supply line 51. The installation location of the amplifier 31 is also determined by taking into consideration the amplifier connection loss. The amount of power generated by the energy harvester 32 is determined according to the amount of energy that needs to be replenished by the amplifier 31.

[0020] [Determining the amount of energy amplification] Hereinafter, a method for determining the amount of energy that needs to be replenished by the amplifier 31 in the optical power supply system 1 according to the first embodiment will be described. Fig. 2 is a schematic diagram showing the amount of energy in the optical fiber in the optical power supply system 1 according to the first embodiment of the present invention.

[0021] In Figure 2, E MAX E represents the upper limit of the power that can be input to the optical fiber (input optical power). Amp represents the power in the optical fiber at the amplifier 31. C represents the amplifier connection loss caused by connecting the amplifier 31 to the optical power supply line 51. R represents the amount of energy amplification to be performed by the amplifier 31. R The value of is set so as to satisfy both of the following conditions (a) and (b).

[0022] (a) From the viewpoint of safety, the amount of amplified energy is limited to the upper limit of the power that can be input to the optical fiber (E MAX ) and the amount must not exceed (b) To obtain the energy amplification effect by using the amplifier 31, W R The value of is the amplifier connection loss (W C ) value or greater.

[0023] W that satisfies the above conditions (a) and (b) R can be expressed as the following equation (1).

[0024] W C ≦W R ≦(E MAX -E Amp +W C ) ···(1)

[0025] As shown in FIG. 2, if the amount of energy amplification by the amplifier 31 is 0, the received optical power at the optical power supply unit 20 (light receiving end) is affected by the optical fiber loss according to the distance from the light source 11, as well as the amplifier connection loss (W C ) is further attenuated by the amount

[0026] Also, in Figure 2, W Env represents the amount of power generated by the energy harvester 32. Here, if the efficiency of the amplifier 31 converts electricity into light is A [%], then [W Env × A / 100] is W R The installation location and size of the energy harvester 32 are determined in accordance with the above.

[0027] The size of the energy harvester 32 here refers to the size and number of panels if the energy harvester 32 is a solar power generator, for example. Env × A / 100] value is W R If this can be achieved, then the amount of energy amplification by the amplifier 31 can be adjusted to W by using, for example, an attenuator (ATT). R The signal may be appropriately attenuated so that

[0028] As described above, in the optical power supply system 1 of the first embodiment, the amplifier 31 is provided midway along the optical power supply line 51, which is an optical transmission line connecting the light source 11 and the optical power supply unit 20 that supplies power to the power supply target device. The amplifier 31 amplifies energy so as to replenish an amount of energy equivalent to optical fiber loss occurring in the optical power supply line 51. With this configuration, the optical power supply system 1 of the first embodiment can supply sufficient power to operate the devices in the power supply target area, even if, for example, the distance between the light source 11 and the optical power supply unit 20 is great and optical fiber loss occurring in the optical power supply line 51 is large.

[0029] Furthermore, as described above, in the optical power supply system 1 according to the first embodiment, the amplifier 31 amplifies energy in consideration of an amplifier connection loss that occurs when the amplifier 31 is connected to the optical power supply line 51. With this configuration, the optical power supply system 1 according to the first embodiment can supply sufficient power to operate devices in the power supply area even if an amplifier connection loss occurs.

[0030] As described above, in the optical power supply system 1 according to the first embodiment, the amplifier 31 is driven by the power generated by the energy harvester 32. With this configuration, the optical power supply system 1 according to the first embodiment can install not only the power supply target device and the optical power supply unit 20 but also the amplifier 31 in a non-electrified area.

[0031] Furthermore, in the optical power supply system 1 of the first embodiment, there is no need to increase the light intensity of the existing light source 11 in order to increase the amount of power supply, and therefore, there is no risk of heating the optical fiber. Therefore, the optical power supply system 1 of the first embodiment can increase the amount of power supply in optical power supply without compromising safety.

[0032] Furthermore, the optical power supply system 1 in the first embodiment can utilize the existing light source 11, the existing optical power supply line 51, and the PD of the existing optical power supply unit 20. In this way, the optical power supply system 1 in the first embodiment can be constructed without significantly modifying the existing system, and therefore installation costs can be kept low.

[0033] <Second embodiment> A second embodiment of the present invention will now be described.

[0034] [Configuration of optical power supply system] The configuration of the optical power supply system 1a according to the second embodiment will be described below. Fig. 3 is a diagram showing the overall configuration of the optical power supply system 1a according to the second embodiment of the present invention. As shown in Fig. 3, the optical power supply system 1a includes a light source 11, an optical power supply unit 20, an amplifier 31, an energy harvester 32, a storage battery 33, and an optical power supply line 51.

[0035] The configuration of the optical power supply system 1a in the second embodiment differs from the configuration of the optical power supply system 1 in the first embodiment in that a storage battery 33 is installed midway along the path between the amplifier 31 and the energy harvester 32. The storage battery 33 stores the electricity generated by the energy harvester 32. The storage battery 33 also supplies the stored power to the amplifier 31.

[0036] Also, in Fig. 3 as in Fig. 2, W Env represents the amount of power generated by the energy harvester 32. Here, if the conversion efficiency from electricity to light of the amplifier 31 is A [%] and the conversion efficiency of the storage battery is B [%], then [W Env ×A / 100×B / 100] is W R The installation location and size of the energy harvester 32 are determined so that the above is achieved. Env ×A / 100×B / 100] is calculated as W R If this can be achieved, then the amount of energy amplified by the amplifier 31 will be W R The output of the storage battery can be adjusted so that

[0037] As described above, in the optical power supply system 1a of the second embodiment, the storage battery 33 is installed midway along the path between the amplifier 31 and the energy harvester 32. With this configuration, the optical power supply system 1a of the second embodiment can supply power to the amplifier 31 more stably than in the optical power supply system 1 of the first embodiment, in which the amplifier 31 and the energy harvester 32 are directly connected.

[0038] This is because, just as the amount of power generated by a solar power generator is easily affected by changes in sunlight conditions, the amount of power generated by the energy harvester 32 is easily affected by changes in the environment. By installing the storage battery 33 midway along the path between the amplifier 31 and the energy harvester 32, it becomes possible to keep the amount of energy supplied from the storage battery 33 to the amplifier 31 approximately constant, even if the amount of power generated by the energy harvester 32 becomes unstable due to changes in the environment.

[0039] <Third embodiment> A third embodiment of the present invention will now be described.

[0040] [Configuration of optical power supply system] The configuration of an optical power supply system 1b according to the third embodiment will be described below. Fig. 4 is a diagram showing the overall configuration of the optical power supply system 1b according to the third embodiment of the present invention. As shown in Fig. 4, the optical power supply system 1b includes a light source 11, an optical power supply unit 20, an amplifier 31, an energy harvester 32, a storage battery 33, a storage battery usage switching unit 40, and an optical power supply line 51.

[0041] The configuration of the optical power supply system 1b in the third embodiment differs from the configuration of the optical power supply system 1a in the second embodiment in that a storage battery use switching unit 40 (first switching unit) is installed between the amplifier 31 and the energy harvester 32. As shown in FIG. 4, the storage battery use switching unit 40 includes a switch 41p, a switch 41q, and a switch control unit 42.

[0042] The switch 41p is a one-input, two-output switch that can appropriately switch between two output terminals to be used. On the other hand, the switch 41q is installed after the switch 41p. The switch 41q is a two-input, one-output switch that can appropriately switch between two input terminals to be used. The switch control unit 42 controls the switching of terminals by the switches 41p and 41q in accordance with the amount of power generated by the energy harvester 32.

[0043] 4, when the output of the switch 41p is switched to side A and the input of the switch 41q is switched to side A, a path is established that directly connects the energy harvester 32 and the amplifier 31. That is, the power generated by the energy harvester 32 is directly input to the amplifier 31. When the output of the switch 41p is switched to side B and the input of the switch 41q is switched to side B, a path is established that connects the energy harvester 32 and the amplifier 31 via the storage battery 33. That is, the power generated by the energy harvester 32 is temporarily stored in the storage battery 33 and then supplied from the storage battery 33 to the amplifier 31.

[0044] When the amount of power generated by the environmental power generator 32 exceeds the amount of power required by the amplifier 31 and there is surplus power, the switch control unit 42 controls the switches 41p and 41q so that power is stored in the storage battery 33 and power is supplied from the storage battery 33 to the amplifier 31. That is, in this case, the switch control unit 42 controls the output of the switch 41p and the input of the switch 41q so that they are both on the B side.

[0045] On the other hand, when the amount of power generated by the environmental power generator 32 does not exceed the amount of power required by the amplifier 31 and there is no surplus power, the switch control unit 42 controls the switches 41p and 41q so that power is directly supplied from the environmental power generator 32 to the amplifier 31. That is, in this case, the switch control unit 42 controls both the output of the switch 41p and the input of the switch 41q to be on the A side.

[0046] [Switch control section operation] The following describes the operation of the switch control unit 42. Fig. 5 is a flowchart showing the operation of the switch control unit 42 of the optical power supply system 1b according to the third embodiment of the present invention.

[0047] The switch control unit 42 compares the amount of power generated by the environmental power generator 32 with the amount of power required by the amplifier 31 (step S301). If the amount of power generated by the environmental power generator 32 exceeds the amount of power required by the amplifier 31 (step S301: YES), the switch control unit 42 sets both the output and input of the switch 41p to side B, and performs control so that the storage battery 33 is charged by the environmental power generator 32 while power is supplied from the storage battery 33 to the amplifier 31 (step S302).

[0048] On the other hand, if the amount of power generated by the environmental power generator 32 does not exceed the amount of power required by the amplifier 31 (step S301: NO), the switch control unit 42 determines whether the amount of power generated by the environmental power generator 32 is equal to or greater than a predetermined threshold (step S303). If the amount of power generated by the environmental power generator 32 is equal to or greater than the predetermined threshold (step S303: YES), the switch control unit 42 sets both the output and input of the switch 41p to side A, thereby performing control so that power is directly supplied from the environmental power generator 32 to the amplifier 31 (step S304). In other words, if there is no surplus power but the amount of power generated by the environmental power generator 32 is sufficient to power the amplifier 31, the switch control unit 42 causes power to be directly supplied from the environmental power generator 32 to the amplifier 31.

[0049] On the other hand, if the amount of power generated by the environmental power generator 32 is less than the predetermined threshold (step S303: NO), the switch control unit 42 determines whether the amount of power stored in the storage battery 33 is equal to or greater than the predetermined threshold (step S305). If the amount of power stored in the storage battery 33 is equal to or greater than the predetermined threshold (step S305: YES), the switch control unit 42 sets both the output and input of the switch 41p to side B, and performs control so that power is supplied from the storage battery 33 to the amplifier 31 (step S306).

[0050] On the other hand, if the amount of stored power in the storage battery 33 is less than the predetermined threshold (step S305: NO), the switch control unit 42 sets both the output and input of the switch 41p to side A, and controls the environmental power generator 32 to supply power directly to the amplifier 31 (step S307).

[0051] The reason why the switch control unit 42 operates as in step S307 above is that if the amount of power generated by the environmental power generator 32 is not sufficient to power the amplifier 31 and the amount of power stored in the storage battery 33 is also not sufficient to power the amplifier 31, a route via the storage battery 33 would result in a further power shortage due to conversion loss. Therefore, the switch control unit 42 controls the supply of even a small amount of generated power directly to the amplifier 31.

[0052] As described above, in the optical power supply system 1b of the third embodiment, the storage battery 33 and the storage battery use switching unit 40 (first switching unit) are installed midway along the path between the amplifier 31 and the energy harvester 32. With this configuration, the optical power supply system 1b can store power in the storage battery 33 and supply power from the storage battery 33 to the amplifier 31 when the amount of power generated by the energy harvester 32 exceeds the amount of power required by the amplifier 31 and there is surplus power, and can supply power directly from the energy harvester 32 to the amplifier 31 when the amount of power generated by the energy harvester 32 does not exceed the amount of power required by the amplifier 31 and there is no surplus power. As a result, the optical power supply system 1b of the third embodiment can supply energy to the amplifier 31 more stably than the optical power supply system 1 of the first embodiment and the optical power supply system 1a of the second embodiment.

[0053] <Fourth embodiment> A fourth embodiment of the present invention will now be described.

[0054] [Configuration of optical power supply system] The configuration of an optical power supply system 1c according to the fourth embodiment will be described below. Fig. 6 is a diagram showing the overall configuration of the optical power supply system 1c according to the fourth embodiment of the present invention. As shown in Fig. 6, the optical power supply system 1c includes a light source 11, an optical power supply unit 20, an amplifier 31, an energy harvester 32, a storage battery 33, and an optical power supply line 51.

[0055] The configuration of the optical power supply system 1c in the fourth embodiment differs from the configuration of the optical power supply system 1 in the first embodiment in that a storage battery 33 is installed after the optical power supply unit 20. The storage battery 33 stores the electricity output from the optical power supply unit 20. The storage battery 33 constantly outputs a fixed amount of power to the target devices in the target power supply area.

[0056] With this configuration, the optical power supply system 1c in the fourth embodiment can stably supply power to the power supply target device even if the amount of power generated by the energy harvester 32 fluctuates over time due to environmental changes, etc.

[0057] <Fifth embodiment> The fifth embodiment of the present invention will now be described.

[0058] [Configuration of optical power supply system] The configuration of an optical power supply system 1d according to the fifth embodiment will be described below. Fig. 7 is a diagram showing the overall configuration of the optical power supply system 1d according to the fifth embodiment of the present invention and the amount of energy in an optical fiber. As shown in Fig. 7, the optical power supply system 1d includes a light source 11 provided in a station building, a light source 12 installed near an energy harvester 32, a light source determination unit 15, an optical power supply unit 20, an amplifier 31, the energy harvester 32, and an optical power supply line 51.

[0059] The configuration of the optical power supply system 1d in the fifth embodiment differs from the configuration of the optical power supply system 1 in the first embodiment in that a light source (light source 12) is also installed near the energy harvester 32, and a light source determination unit 15 is further provided. The light source determination unit 15 determines whether optical power supply is to be performed by the light source 11 or the light source 12.

[0060] If the distance between the light source 11 provided in the station and the optical power supply unit 20 is greater than a certain value, the amount of energy supplied from the light source 11 will attenuate to almost zero (less than a predetermined threshold value α) at ​​the point of the optical power supply unit 20. In this case, there will be almost no benefit to using the light source 11 provided in the station.

[0061] In this way, when the amount of energy supplied from the light source 11 attenuates to almost zero at the point of the optical power supply unit 20, the light source determination unit 15 switches from optical power supply by the light source 11 provided in the station building to optical power supply by the light source 12 installed near the energy harvester 32. The light source 12 is driven by power generated by the energy harvester 32. This makes it possible for the light source 12 to emit light even in a non-electrified area.

[0062] With such a configuration, the optical power supply system 1d in the fifth embodiment can increase the amount of power supply without compromising safety in optical power supply, even if the distance between the light source 11 provided in the station and the optical power supply unit 20 is greater than a certain value.

[0063] Sixth Embodiment A sixth embodiment of the present invention will now be described.

[0064] [Configuration of optical power supply system] The configuration of an optical power supply system 1e according to the sixth embodiment will be described below. Fig. 8 is a diagram showing the overall configuration of the optical power supply system 1e according to the sixth embodiment of the present invention. As shown in Fig. 8, the optical power supply system 1e includes a light source 11, an optical power supply unit 20, an amplifier 31, an energy harvester 32, an optical power supply line 51, and an amplifier use switching unit 60.

[0065] The configuration of the optical power supply system 1e in the sixth embodiment differs from the configuration of the optical power supply system 1 in the first embodiment in that an amplifier use switching unit 60 (second switching unit) is further installed midway along the optical power supply line 51. As shown in Fig. 8, the amplifier use switching unit 60 includes an optical switch 61p, an optical switch 61q, and an optical switch control unit 62.

[0066] The optical switch 61p is a one-input, two-output optical switch that can appropriately switch between two output terminals to be used. On the other hand, the optical switch 61q is installed after the optical switch 61p. The optical switch 61q is a two-input, one-output optical switch that can appropriately switch between two input terminals to be used. The optical switch control unit 62 controls the switching of terminals by the optical switches 61p and 61q according to the amplification capacity of the amplifier 31.

[0067] 8, when the output of the optical switch 61p is switched to side A and the input of the optical switch 61q is switched to side A, the light source 11 and the optical power supply unit 20 are directly connected without passing through the amplifier 31. That is, the light emitted from the light source 11 is received directly by the optical power supply unit 20. When the output of the optical switch 61p is switched to side B and the input of the optical switch 61q is switched to side B, the light source 11 and the optical power supply unit 20 are connected via the amplifier 31. That is, the light emitted from the light source 11 is amplified by the amplifier 31 and then received by the optical power supply unit 20.

[0068] The optical switch control unit 62 checks the amount of amplification that the amplifier 31 can perform at the current time, and if the amount of amplification that can be performed is equal to or greater than a predetermined threshold value β, controls the optical switches 61p and 61q to form a path that passes through the amplifier 31. On the other hand, if the amount of amplification that the amplifier 31 can perform at the current time is less than the predetermined threshold value β, the optical switch control unit 62 controls the optical switches 61p and 61q to form a path that does not pass through the amplifier 31.

[0069] Because the amplifier 31 is powered by the power supplied from the energy harvester 32, a decrease in the power supply due to environmental changes or the like may result in a power supply shortage. When the amplifier 31 is not driven due to a power supply shortage from the energy harvester 32, it functions as a powerful attenuator rather than an amplifier. However, with the above-described configuration, the optical power supply system 1e according to the sixth embodiment can switch to a path that does not pass through the amplifier 31 when the amplifier 31 is not driven due to a power supply shortage. This prevents the influence of amplifier connection loss caused by connecting the amplifier 31 to the optical power supply line 51, enabling the optical power supply system 1e according to the sixth embodiment to supply energy to the optical power supply unit 20 without excessive energy loss.

[0070] The power required to operate the optical switches 61p and 61q may be supplied by the energy harvester 32. When power is not supplied to the optical switches 61p and 61q, the optical switches 61p and 61q are configured to automatically switch to side A (i.e., to a path that does not pass through the amplifier 31).

[0071] The configurations of the amplifier use switching unit 60 and the amplifier 31 of the optical power supply system 1e in the sixth embodiment can also be applied to the optical power supply systems in the above-described first to fifth embodiments. In this case, the configuration of the amplifier 31 of the optical power supply systems in the above-described first to fifth embodiments can be replaced with a configuration that combines the amplifier use switching unit 60 and the amplifier 31 of the optical power supply system 1e in the sixth embodiment.

[0072] [Operation of the optical switch control unit] The following describes the operation of the optical switch control unit 62. Fig. 9 is a flowchart showing the operation of the optical switch control unit 62 of the optical power supply system 1e according to the sixth embodiment of the present invention.

[0073] The optical switch control unit 62 determines whether the amount of energy monitored by the amplifier 31 or the environmental power harvester 32 exceeds a predetermined threshold value β (step S601). If the amount of energy monitored by the amplifier 31 or the environmental power harvester 32 exceeds the predetermined threshold value β (step S601: YES), the optical switch control unit 62 sets both the output and the input of the optical switch 61p to side B, and controls the amplifier 31 to amplify the energy received from the light source 11 before supplying it to the optical power supply unit 20 (step S602).

[0074] On the other hand, if the amount of energy monitored by the amplifier 31 or the environmental power generator 32 does not exceed the predetermined threshold value β (step S601: NO), the optical switch control unit 62 sets both the output and input of the optical switch 61p to side A, and controls the energy received from the light source 11 to be supplied to the optical power supply unit 20 without passing through the amplifier 31 (step S603).

[0075] As described above, the optical power supply system 1e according to the sixth embodiment of the present invention is configured so that when sufficient power is not supplied to the amplifier 31, the light sent from the source is transmitted directly to the optical power supply unit 20 without passing through the amplifier 31. With this configuration, the optical power supply system 1e can prevent the amplifier 31 from functioning as an attenuator, and can stably increase the amount of supplied power without compromising safety in optical power supply.

[0076] Seventh Embodiment The seventh embodiment of the present invention will now be described.

[0077] [Configuration of optical power supply system] The configuration of an optical power supply system 1f according to the seventh embodiment will be described below. Fig. 10 is a diagram showing the overall configuration of the optical power supply system 1f according to the seventh embodiment of the present invention. As shown in Fig. 10, the optical power supply system 1f includes a light source 11, an optical power supply unit 20, an amplifier 31, a commercial power supply 34, and an optical power supply line 51.

[0078] The configuration of the optical power supply system 1f in the seventh embodiment differs from the configuration of the optical power supply system 1 in the first embodiment in that a commercial power source 34 is used instead of the energy harvester 32. That is, unlike the first to sixth embodiments, the seventh embodiment is assumed to install the amplifier 31 in an electrified area rather than a non-electrified area.

[0079] In this embodiment, the amplifier 31 is driven by power supplied from a commercial power source 34. If the installation location of the amplifier 31 is an electrified area, it is also possible to install a light source at the installation location of the amplifier 31. However, since a large laser is generally used as the light source, installation may be difficult due to installation location restrictions and safety restrictions.

[0080] As described above, in the optical power supply system 1f according to the seventh embodiment of the present invention, the amplifier 31 is provided midway along the optical power supply line 51, which is an optical transmission line connecting the light source 11 and the optical power supply unit 20 that supplies power to the power supply target device. The amplifier 31 amplifies energy so as to replenish an amount of energy equivalent to the optical fiber loss occurring in the optical power supply line 51. With this configuration, the optical power supply system 1f according to the seventh embodiment can supply sufficient power to operate the devices in the power supply target area, even if, for example, the distance between the light source 11 and the optical power supply unit 20 is great and the optical fiber loss occurring in the optical power supply line 51 is large.

[0081] Eighth Embodiment An eighth embodiment of the present invention will now be described.

[0082] [Configuration of optical power supply system] The configuration of an optical power supply system 1g according to the eighth embodiment will be described below. Fig. 11 is a diagram showing the overall configuration of the optical power supply system 1g according to the eighth embodiment of the present invention. As shown in Fig. 11, the optical power supply system 1g includes a light source 11, a light source 13, an optical power supply unit 20, an amplifier 31, an optoelectric conversion unit 35, and an optical power supply line 51.

[0083] The configuration of the optical power supply system 1f in the eighth embodiment differs from the configuration of the optical power supply system 1 in the first embodiment described above in that a light source 13 and a photoelectric conversion unit 35 are used instead of an environmental power generator 32.

[0084] The light source 13 is installed in a building such as a station building of a communications base station. This station building is located in an electrified area, and is located, for example, far away from the photoelectric conversion unit 35 and the amplifier 31. The light source 13 emits light for optical power supply toward the photoelectric conversion unit 35. As the light for optical power supply, for example, light that is always on may be used. The light emitted by the light source 13 is transmitted to the photoelectric conversion unit 35 via an optical fiber. As a network configuration for the path between the light source 13 and the photoelectric conversion unit 35, for example, an SS (Single Star) configuration without branching is used in order to reduce branching loss.

[0085] In this way, light source 11 emits light for operating a power supply target device that is driven by optical power supplied by optical power supply unit 20. In response to this, light source 13 emits light for driving amplifier 31 to photoelectric conversion unit 35. Photoelectric conversion unit 35 receives the light sent from light source 13, performs photoelectric conversion, and supplies power to amplifier 31 via optical power supply. This drives amplifier 31.

[0086] As described above, in the optical power supply system 1g according to the eighth embodiment of the present invention, an amplifier 31 is provided midway along the optical power supply line 51, which is an optical transmission line connecting the light source 11 and the optical power supply unit 20 that supplies power to a power supply target device. The amplifier 31 amplifies energy so as to replenish an amount of energy equivalent to optical fiber loss occurring in the optical power supply line 51. With this configuration, the optical power supply system 1g according to the eighth embodiment can supply sufficient power to operate devices in the power supply target area, even if, for example, the light source 11 and the optical power supply unit 20 are far apart and optical fiber loss occurring in the optical power supply line 51 is large.

[0087] [Example] Hereinafter, the configuration of the optical power supply system 1 in the first embodiment described above will be used as an example, and actual values ​​will be substituted to clarify the feasibility of the present invention.

[0088] 12 is a diagram illustrating an embodiment of the present invention. For example, assume that the distance between the light source 11 and the amplifier 31 is 10 km. Also, assume that the optical fiber loss occurring in the optical power feed line 51 is 0.3 dB / km. From the perspective of the fiber fuse phenomenon (the phenomenon in which the fiber melts), when the upper limit of the input optical power is set to 32 dBm (= 1.5 W), the amount of energy in the optical fiber at the point of the amplifier 31 is attenuated to 29 dBm. In other words, to compensate for this energy attenuation, the amplifier 31 needs to amplify the energy by 3 dB (= 0.75 W).

[0089] For example, two commercially available solar cells measuring 1.2 m x 0.5 m generate approximately 200 W of power. If the average daily power generation, taking into account nighttime and rainy weather, is assumed to be 1 / 10 of 200 W, then an average of 20 W of energy can be supplied from these solar cells. If the power conversion efficiency of the amplifier 31 is assumed to be 4%, then 0.8 W can be supplied to the optical fiber. If the amplifier connection loss caused by connecting the amplifier 31 to the optical power supply line 51 is 0.5 dB or less, then theoretically, it is possible to compensate for the aforementioned energy attenuation (0.75 W).

[0090] 13 and 14 are diagrams showing examples of installation of an optical power supply system according to an embodiment of the present invention. Fig. 13 shows an example of installation in which the amplifier 31 is installed in a non-electrified area, and Fig. 14 shows an example of installation in which the amplifier 31 is installed in an electrified area.

[0091] The optical power supply system shown in Fig. 13 includes a light source installed in a station in an electrified area, and an amplifier, a light receiving terminal, a battery, and a power supply target device in a non-electrified area. Because the amplifier is in a non-electrified area, power to operate the amplifier is supplied by an energy harvester that can generate power even in a non-electrified area.

[0092] On the other hand, the optical power supply system shown in Fig. 14 is composed of a light source and an amplifier installed in a station building in an electrified area, and a light receiving terminal, a battery, and a power supply target device in a non-electrified area. Because the amplifier is in an electrified area, the power to operate the amplifier can be supplied from a commercial power source.

[0093] According to the above-described embodiment, the optical power supply system includes a light source, an amplifier, and an optical power supply unit. For example, the optical power supply system is the optical power supply systems 1 and 1a to 1g in the embodiments, the light source is the light source 11 in the embodiments, the amplifier is the amplifier 31 in the embodiments, and the optical power supply unit is the optical power supply unit 20 in the embodiments. The light source transmits light for optical power supply to an optical power supply line connected to the optical power supply unit. For example, the optical power supply line is the optical power supply line 51 in the embodiments. The amplifier is installed midway along the optical power supply line and amplifies the light transmitted from the light source. The optical power supply unit receives the light amplified by the amplifier and obtains power by photoelectrically converting the light.

[0094] The optical power supply line may be a line having a single star configuration.

[0095] The optical power supply system may further include an energy harvester. For example, the energy harvester is the energy harvester 32 in the embodiment. The energy harvester 32 generates electricity by energy harvesting. The amplifier may then be driven by electricity obtained from the energy harvester.

[0096] The amplifier may be configured to supplement the power lost due to optical fiber loss occurring between the light source and the optical power feed section.

[0097] The above amplifier has a power consumption W that satisfies the following equation (2): R The power may be supplemented.

[0098] W C ≦W R ≦(E MAX -E Amp +W C )···(2)

[0099] where W C represents the amount of power lost when the amplifier is connected to the optical power line, and E MAX represents the upper limit of the power that can be input to the optical power supply line, and E Amp represents the power of the optical feed line at the amplifier point.

[0100] The optical power supply system may further include a first switching unit. For example, the first switching unit is the storage battery use switching unit 40 in the embodiment. The first switching unit may switch the path between the energy harvester and the amplifier to either a path that goes through the storage battery or a path that does not go through the storage battery, depending on the amount of power generated by the energy harvester. The storage battery is provided between the energy harvester and the amplifier, stores electricity obtained from the energy harvester, and sends the stored electricity to the amplifier.

[0101] The optical power supply system may further include a second switching unit. For example, the second switching unit switches the path between the light source and the optical power supply unit between a path that goes through the amplifier and a path that does not go through the amplifier, depending on the amount of power that can be amplified by the amplifier.

[0102] A part of the configuration of the optical power supply system 1 and the optical power supply systems 1a to 1g in the above-described embodiments may be implemented by a computer. In this case, a program for implementing the functions may be recorded on a computer-readable recording medium, and the program may be loaded into a computer system and executed. Note that the term "computer system" as used herein includes hardware such as an OS and peripheral devices. Furthermore, the term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into computer systems. Furthermore, the term "computer-readable recording medium" may also include devices that dynamically store programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or telephone lines, or devices that store programs for a fixed period of time, such as volatile memory within a computer system that serves as a server or client. The program may be for implementing a part of the above-described functions, or may be capable of implementing the above-described functions in combination with a program already stored in the computer system, or may be implemented using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0103] Although an embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention. [Explanation of symbols]

[0104] 1, 1a to 1g... optical power supply system, 11 to 13... light source, 15... light source determination unit, 20... optical power supply unit, amplifier 31, energy harvester... 32, storage battery... 33, 51... optical power supply line, 20... optical power supply unit, 31... amplifier, 32... energy harvester, 33... storage battery, 34... commercial power supply, 35... photoelectric conversion unit, 40... storage battery use switching unit, 41p... switch, 41q... switch, 42... switch control unit, 51... optical power supply line, 60... amplifier use switching unit, 61p... optical switch, 61q... optical switch, 62... optical switch control unit

Claims

1. a step in which a light source transmits light for optical power feeding to an optical power feeding line connected to the optical power feeding unit; a step of generating power by energy harvesting using an energy harvester; an amplifier installed along the optical power supply line and driven by electricity obtained from the energy harvester amplifying the light emitted from the light source; a storage battery provided between the energy harvester and the amplifier storing electricity acquired from the energy harvester and transmitting the stored electricity to the amplifier; a switching unit switching a path between the energy harvester and the amplifier to either a path that passes through the storage battery or a path that does not pass through the storage battery, depending on the amount of power generated by the energy harvester; the optical power supply unit receiving the light amplified by the amplifier and performing photoelectric conversion of the light to obtain electric power; An optical power supply method comprising:

2. The optical power supply line is a line with a single star configuration. The optical power supply method according to claim 1 .

3. The amplifier compensates for the power loss caused by optical fiber loss between the light source and the optical power supply unit. The optical power supply method according to claim 1 or 2.

4. The amplifier supplies a power of an amount WR that satisfies the following formula: The optical power supply method according to claim 1 or 2. WC≦WR≦(EMAX-EAmp+WC) Here, WC represents the amount of power lost when the amplifier is connected to the optical power line, EMAX represents the upper limit of the power that can be input to the optical power line, and EAmp represents the power of the optical power line at the amplifier point.

5. A step in which a light source transmits light for optical power supply to an optical power supply line connected to an optical power supply unit; an amplifier installed midway along the optical power supply line amplifying the light transmitted from the light source; a switching unit switching a path between the light source and the optical power supply unit to either a path that passes through the amplifier or a path that does not pass through the amplifier, depending on the amount of power that can be amplified by the amplifier; the optical power supply unit receiving the light amplified by the amplifier and performing photoelectric conversion of the light to obtain electric power; An optical power supply method comprising:

6. a light source that transmits light for optical power feeding to an optical power feeding line connected to the optical power feeding unit; an energy harvester that generates electricity by energy harvesting; an amplifier that is installed along the optical power supply line, is driven by electricity obtained from the energy harvester, and amplifies the light transmitted from the light source; a storage battery provided between the energy harvester and the amplifier, for storing electricity acquired from the energy harvester and transmitting the stored electricity to the amplifier; a switching unit that switches a path between the environmental power generator and the amplifier to either a path that passes through the storage battery or a path that does not pass through the storage battery, depending on the amount of power generated by the environmental power generator; the optical power supply unit that receives the light amplified by the amplifier and obtains electric power by photoelectrically converting the light; An optical power supply system having the same.

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