Power supply system

Abstract

An optical node (20) comprises: a photoelectric conversion circuit (22); a capacitor (C); and a derivation unit (31) that executes, in accordance with received light power, a process for deriving, as a function of a predetermined charging start voltage (VL), a charging time (ΔT) required for a capacitor voltage (Vc) to reach a charging end voltage (VH) from the charging start voltage (VL). The optical node (20) comprises a calculation unit (32) that calculates a minimum value (ΔTmin) of the charging time on the basis of the function, and a comparison unit (33) that determines whether or not the minimum value (ΔTmin) is within a specified range. The optical node (20) comprises a setting unit (34) that, if the comparison unit (33) determines that the minimum value (ΔTmin) is not within the specified range with received light power (P), determines whether or not the minimum value (ΔTmin) calculated by the calculation unit (32) is within the specified range with received light power (P + ΔP) or (P - ΔP), and that, if the comparison unit (33) determines that the minimum value (ΔTmin) is within the specified range, sets the received light power at that time as the received light power received by the photoelectric conversion circuit (22).

Description

Power supply system

[0001] The present disclosure relates to a power supply system that supplies power from a light source to an optical node.

[0002] In Non-Patent Document 1, a power supply optical signal (hereinafter referred to as "power supply light") for supplying power from a light source for optical power supply mounted on an in-house optical node installed in a communication building or the like to an optical node installed at a remote location via an optical fiber network is transmitted, and an optical fiber power supply system (also referred to as a POF (Power Over Fiber) system) that charges a capacitor mounted on the optical node is disclosed. In the optical node, the power charged in the capacitor can be used to drive the devices mounted on the optical node. Further, data on the charging voltage of the capacitor can be fed back to the in-house optical node.

[0003] In the POF system, the power supply light output from the light source is received and photoelectrically converted by a photoelectric conversion circuit mounted on the optical node. In the optical node, the power generated by photoelectric conversion in the photoelectric conversion circuit is used to charge a capacitor. The optical node starts driving the device when charging of the capacitor is started and the capacitor voltage reaches a predetermined charging end voltage VH. When the driving of the device ends, the optical node starts charging the capacitor again from this point. The voltage of the capacitor at this time is taken as the charging start voltage VL.

[0004] That is, in the optical node, the driving of the device is started when the capacitor voltage reaches the charging end voltage VH, and when the driving of the device ends, the charging of the capacitor is started. The optical node repeats the operation of driving the device again when the capacitor voltage rises from the charging start voltage VL to the charging end voltage VH. Therefore, the required time (this is referred to as the charging time ΔT) until the capacitor voltage becomes from the charging start voltage VL to the charging end voltage VH becomes the interval time of device use.

[0005] IEICE Society Conference b-8-3, 2022, “Study on Remote Operation and Management / Maintenance Functions in Remote Optical Path Switching Nodes” OFC 2024 Th2A.35 “Estimation of Energy Storage Status in Power Supply System Using Power over Fiber for Outdoor Environment”

[0006] In optical nodes, the power consumption of the device to be driven is predetermined, and often the interval between device usage, i.e., the charging time ΔT, is also predetermined. Therefore, it is desirable to set the received light power (dBm) output from the light source mounted on the in-house optical node and received by the photoelectric conversion circuit to an appropriate value according to the predetermined power consumption and charging time ΔT.

[0007] In other words, from a safety standpoint, there are limitations to the power of the light that can be transmitted using optical fiber cables, and the power of the light cannot be set above a certain level. Furthermore, setting the power of the light to be higher than necessary leads to increased energy loss. On the other hand, setting the power of the light to be lower increases the charging time ΔT, making it impossible to satisfy the preset charging time ΔT.

[0008] Therefore, under the condition that the device's power consumption and charging time ΔT are constant, it is desirable to set the power of the supplied light output from the light source so that the received light power received by the photoelectric conversion circuit is optimal. Non-patent document 2 proposes a theoretical formula that shows the time change (dVc / dt) of the capacitor voltage Vc when charging a capacitor mounted on an optical node in a POF system.

[0009] However, Non-Patent Document 2 does not mention the relationship between the power consumption of the device mounted on the optical node, the charging time ΔT, and the light-receiving power in the photoelectric conversion circuit. Therefore, when the power consumption of the device mounted on the optical node and the charging time ΔT are determined, it is difficult to set the light-receiving power in the photoelectric conversion circuit to an optimal value.

[0010] This disclosure has been made in view of the above circumstances, and its purpose is to provide a power supply system that can set the light-receiving power in a photoelectric conversion circuit to an optimal value when the power consumption of the device and the charging time ΔT of the capacitor are determined.

[0011] A power supply system according to one aspect of the present disclosure includes a light source that outputs power supply light and an optical node that receives the power supply light, wherein the optical node includes a photoelectric conversion circuit that receives the power supply light and converts it into electricity, a capacitor that charges the electricity, a derivation unit that derives the charging time required for the charging voltage of the capacitor to reach a predetermined charging end voltage from a predetermined charging start voltage as a function of the charging start voltage, in accordance with the light received power received by the photoelectric conversion circuit, a calculation unit that calculates the minimum value of the charging time based on the function derived by the derivation unit, and a comparison unit that determines whether the minimum value is within a predetermined range based on a target charging time, wherein the comparison unit determines that the minimum value calculated by the calculation unit is not within the predetermined range for one light received power, and further includes a setting unit that determines whether the minimum value calculated by the calculation unit is within the predetermined range for another light received power, and if it determines that the minimum value is within the predetermined range, sets the light received power at that time as the light received power received by the photoelectric conversion circuit.

[0012] According to this disclosure, when the power consumption of the device and the charging time of the capacitor are determined, it becomes possible to set the power of the supplied light to an optimal value.

[0013] Figure 1 is a schematic diagram of the power supply system according to the embodiment. Figure 2 is a block diagram showing the detailed configuration of the optical node. Figure 3 is a circuit model of the photoelectric conversion circuit, control circuit, and charging circuit mounted on the optical node. Figure 4 is a graph showing the change in capacitor voltage Vc over time. Figure 5 is an explanatory diagram showing each parameter of the circuit model shown in Figure 3. Figure 6 is an explanatory diagram showing the setting values ​​of each parameter used in the theoretical formula shown in equation (2). Figure 7 is a graph showing the relationship between charging time and capacitor voltage Vc. Figure 8 is a graph showing the relationship between the charging start voltage VL and charging time ΔT, and the relationship between the charging start voltage VL and charging end voltage VH. Figure 9 is a graph showing the relationship between the charging start voltage VL and charging time ΔT when the light receiving power P is changed. Figure 10 is a flowchart showing the processing operation of the power supply system according to the embodiment. Figure 11 is a block diagram showing the hardware configuration of this embodiment.

[0014] Embodiments will be described below with reference to the drawings. Figure 1 is a schematic diagram of the power supply system 100 according to the embodiment. As shown in Figure 1, the power supply system 100 according to this embodiment includes an in-house optical node 10 and an optical node 20. The in-house optical node 10 and the optical node 20 are connected by an optical fiber 5. The distance of the optical fiber 5 laid between the in-house optical node 10 and the optical node 20 is L [km].

[0015] The in-house optical node 10 comprises a light source 1, an optical circulator 2, an optical receiver 3, and a controller 4.

[0016] Light source 1 outputs power supply light. The power supply light output from light source 1 is introduced into optical fiber 5 via optical circulator 2 and transmitted to optical node 20.

[0017] The optical receiver 3 receives the optical signals transmitted from the optical node 20 and separated by the optical circulator 2.

[0018] The controller 4 controls the power of the supplied light output from the light source 1 based on the control data contained in the optical signal received by the optical receiver 3. For example, when the controller 4 receives a control signal from the optical node 20 to set the power (dBm) of the supplied light output by the light source 1, the controller 4 controls the supplied light to achieve the set power.

[0019] The optical node 20 comprises a remote control board 6 and a plurality of devices 7 (7-1 to 7-n). Device 7 has a function, for example, to perform core switching of the optical fiber 5.

[0020] Figure 2 is a block diagram showing the specific configuration of the remote control board 6. As shown in Figure 2, the remote control board 6 includes a communication device 21, a photoelectric conversion circuit 22, a charging circuit 23, and a control circuit 24. Figure 3 is a circuit model of the photoelectric conversion circuit 22, the charging circuit 23, and the control circuit 24 shown in Figure 2.

[0021] The communication device 21 performs optical communication with the in-house optical node 10 shown in Figure 1 via the optical fiber 5. Specifically, the communication device 21 transmits and receives control signals with the in-house optical node 10. The communication device 21 receives control signals that control the operation of device 7 transmitted from the in-house optical node 10 and outputs the received control signals to the control circuit 24. The communication device 21 transmits data (capacitor voltage Vc, described later) of the charging voltage of capacitor C (see Figure 3) mounted on the charging circuit 23 to the in-house optical node 10.

[0022] The photoelectric conversion circuit 22 receives the power supply light transmitted from the light source 1 of the in-house optical node 10 and converts this power supply light into electricity. The photoelectric conversion circuit 22 supplies the power generated by the photoelectric conversion to the charging circuit 23. As shown in Figure 3, the photoelectric conversion circuit 22 is equipped with a photodiode PD1. The two terminals of the photodiode PD1 are connected to the control circuit 24 and the charging circuit 23.

[0023] The charging circuit 23 includes resistors RESR and Rleak, and a capacitor C (see Figure 3), and charges the capacitor C with the power generated by the photodiode PD1. Hereinafter, the voltage charged to the capacitor C will be referred to as the "capacitor voltage Vc".

[0024] The control circuit 24 includes a derivation unit 31, a calculation unit 32, a comparison unit 33, a setting unit 34, and a drive unit 35. The control circuit 24 can be configured, for example, with an MPU (Micro Processing Unit).

[0025] The control circuit 24 supplies power to each device 7 shown in Figure 1 to drive each device 7 when the capacitor voltage Vc being charged to the capacitor C in the charging circuit 23 reaches a predetermined charging termination voltage VH. The charging termination voltage VH is a voltage slightly lower than the saturation voltage of the capacitor C and is a voltage that can supply enough power to drive the devices 7. Furthermore, once the driving of each device 7 is complete, the control circuit 24 controls the charging circuit 23 to start charging the capacitor C at that point.

[0026] As shown in Figure 4, when the capacitor voltage Vc charges and reaches the charging completion voltage VH, the device 7 is started to operate. Therefore, the capacitor voltage Vc decreases to the charging start voltage VL. After that, the capacitor voltage Vc gradually increases due to the start of charging, and when it reaches the charging completion voltage VH again, the device 7 is started to operate, and this operation is repeated. Thus, the capacitor voltage Vc changes periodically as shown in Figure 4. The control circuit 24 sets the power of the power supplied by the light source 1 so that the received power of the power supplied by

[0027] The derivation unit 31 shown in Figure 2 generates a curve showing the relationship between the charging time of capacitor C and the capacitor voltage Vc when the received light power received by the photoelectric conversion circuit 22 is set to a constant value (let's call this the received light power P [dBm]). Specifically, as shown in Figure 7 which will be described later, it generates a curve s1 (details will be described later) with the charging time [sec] on the horizontal axis and the capacitor voltage Vc on the vertical axis.

[0028] The derivation unit 31 calculates the voltage at which the capacitor voltage Vc is supplied to drive each device 7 (this is called the charging completion voltage VH), and the voltage at which the device 7 is finished to drive (this is called the charging start voltage VL). The derivation unit 31 starts charging capacitor C when the capacitor voltage Vc is at the charging start voltage VL, calculates the elapsed time (charging time ΔT) until the capacitor voltage Vc reaches the charging completion voltage VH, and derives a function showing the relationship between the charging start voltage VL and the charging time ΔT. This will be explained in detail below.

[0029] Non-patent document 2, mentioned above, shows the following equation (1) for calculating the current I output from the photoelectric conversion circuit 22.

[0030]

[0031] In equation (1), e is the elementary charge (electron charge), V is the voltage of the photodiode PD1, n is the ideal coefficient of the diode D1, k is the Boltzmann constant, T is the temperature of the photodiode PD1 (calculated at 25°C, 298K absolute temperature in this embodiment), η is the ideal efficiency of the photodiode PD1, P is the light power received by the photodiode PD1 (dBm), λ is the wavelength of light, h is Planck's constant, and c is the speed of light in a vacuum.

[0032] Non-patent document 2 further presents the following equation (2) as a theoretical formula showing the time change (dVc / dt) of the capacitor voltage Vc in the circuit model shown in Figure 3.

[0033]

[0034] The parameters in equation (2) are as shown in Figure 5. Furthermore, by substituting the values ​​shown in Figure 6 into the parameters in equation (2), the curve s1 shown in Figure 7 is obtained.

[0035] That is, under the condition that the power consumption E of each device 7 is constant, a curve s1 is obtained that shows the relationship between the charging time of capacitor C and the capacitor voltage Vc when the light received power (dBm) received by the photodiode PD1 of the photoelectric conversion circuit 22 and the capacitance of capacitor C are set to arbitrary values.

[0036] The curve s1 shown in Figure 7 illustrates the relationship between the charging time and the capacitor voltage Vc, when the light-receiving power of the photodiode PD1 is +5 [dBm], the capacitance of capacitor C is 0.49 [F], and the power consumption of device 7 is 0.3 [J].

[0037] The derivation unit 31 calculates the change in capacitor voltage Vc when each device 7 is driven once, based on the power consumption E of the device 7. As described above, the capacitor voltage Vc at the start of driving the device 7 is defined as the charging end voltage VH, and the capacitor voltage Vc at the end of driving is defined as the charging start voltage VL, and the capacitance of the capacitor C is represented by the same symbol "C". In this case, the power consumption E can be expressed by the following equation (3).

[0038] E=(1 / 2)・C(VH ２ -VL ２ ) ... (3) Also, if we let Vbottom be the voltage at which the control circuit 24 starts up and Vsatu be the voltage when the capacitor voltage Vc is saturated, then the following equation (4) holds true.

[0039] Vbottom < VL < VH < Vsatu ... (4) The derivation unit 31 calculates a combination of voltages VL and VH that satisfies the relationship shown in equation (4). For example, if a voltage VL greater than voltage Vbottom is arbitrarily set, and voltage VH is calculated from this voltage VL using equation (3) above, and if this voltage VH is less than voltage Vsatu, then the combination of voltages VL and VH satisfies equation (4).

[0040] The derivation unit 31 calculates the charging time ΔT from the difference between the charging time elapsed when voltage VL is substituted into the curve s1 shown in Figure 7 (tVL to tVH) and the charging time elapsed when voltage VH, which is a combination of voltage VL and tVH, is substituted (tVL to tVH in Figure 7). That is, the charging time ΔT is calculated as the time elapsed from the charging start voltage VL to the charging end voltage VH when the capacitor voltage Vc reaches the charging end voltage VL.

[0041] The derivation unit 31 calculates the charging time ΔT for each combination of a plurality of voltages VL and VH. As a result, the charging time ΔT becomes a function of the voltage VL. That is, when the charging time ΔT with respect to the voltage VL is represented as "ΔT(VL)", it can be expressed by the following equation (5).

[0042] ΔT(VL) = tVH - tVL ・・・(5) In equation (5), "tVL" represents the time when the capacitor voltage Vc becomes the voltage VL, and "tVH" represents the time when the capacitor voltage Vc reaches the voltage VH. That is, when the voltage VL is determined, the charging time ΔT is uniquely determined. Also, based on the aforementioned equation (4), when the voltage VL is determined, the voltage VH is uniquely determined.

[0043] As a result, as shown in FIG. 8, a curve s2 showing the relationship between the voltage VL and the charging time ΔT, and a curve s3 showing the relationship between the voltage VL and the voltage VH are obtained. In FIG. 8, the curve s2 corresponds to the left scale, and the curve s3 corresponds to the right scale.

[0044] The derivation unit 31 derives the charging time ΔT required for the charging voltage (capacitor voltage Vc) of the capacitor C to reach the charging end voltage VH from the predetermined charging start voltage VL as a function of the charging start voltage VL. The derivation unit 31 derives the above-mentioned function under the condition that the received light power received by the photodiode PD1 of the photoelectric conversion circuit 22 and the power consumption of the device 7 are constant. The derivation unit 31 executes a process of deriving each of the above functions according to the received light power (a plurality of received light powers) received by the photoelectric conversion circuit 22.

[0045] The calculation unit 32 shown in FIG. 2 calculates the voltage VL that minimizes the charging time ΔT. Specifically, the calculation unit 32 calculates the voltage VL at which the charging time ΔT becomes the minimum value ΔTmin in the curve s2 shown in FIG. 8, and the charging time ΔT at this time. By the calculation unit 32, for example, as shown in the curve s2, the voltage VL = 2.54 [V] that minimizes the charging time ΔT and the charging time ΔT = 344 [sec] at this time are obtained.

[0046] The calculation unit 32 calculates the charging end voltage VH corresponding to the charging start voltage VL by associating the voltage VL calculated based on the curve s2 with the curve s3 shown in FIG. 8. That is, the calculation unit 32 calculates a combination of voltages VL and VH (let these be voltages VL1 and VH1, respectively) for which the charging time ΔT is minimized in order to shorten the interval time of device utilization. In the example shown in FIG. 8, as shown by the curve s3, VL1 = 2.54 [V] and VH1 = 2.77 [V]. The calculation unit 32 calculates the charging end voltage VH1 that minimizes the charging time ΔT based on a function showing the relationship between the voltage VL and the charging time ΔT and an expression showing the relationship between the charging start voltage VL and the charging end voltage VH.

[0047] When the calculation unit 32 changes the received power P when receiving the power supply light in the photoelectric conversion circuit 22, it generates a curve showing the relationship between the voltage VL and the charging time ΔT. Specifically, a plurality of curves s2 as shown in FIG. 8 are generated by changing the received power P. For example, curves showing the relationship between the voltage VL and the charging time ΔT are generated for each case where the received power P is set to 3 [dBm], 4 [dBm], 5 [dBm], 6 [dBm], and 7 [dBm], respectively. As a result, as shown in FIG. 9, a plurality of curves s21 to s25 are generated. Note that the curve s23 shown in FIG. 9 is the same as the curve s2 shown in FIG. 8.

[0048] The calculation unit 32 calculates the minimum value ΔTmin of the charging time ΔT for each of the curves s21 to s25. For example, for curve s21, ΔTmin = 570 [sec], for curve s23, ΔTmin = 344 [sec], and for curve s25, ΔTmin = 207.5 [sec]. The calculation unit 32 calculates the minimum value ΔTmin of the charging time ΔT based on the function derived by the derivation unit 31.

[0049] That is, the optical node 20 includes a device 7 driven by the charging voltage of the capacitor (capacitor voltage Vc), and the calculation unit 32 calculates the minimum value ΔTmin assuming that the power consumption of the device 7 is constant.

[0050] The comparison unit 33 determines whether the minimum value ΔTmin of the charging time ΔT calculated by the calculation unit 32 is within the range of an allowable time (Treq - δT to Treq + δT) based on a preset target charging time Treq. "δT" is a time that indicates a margin. That is, it determines whether the minimum value ΔTmin(P) of the charging time ΔT at the light receiving power P satisfies the following equation (6).

[0051] Treq + δT ≥ ΔTmin(P) ≥ Treq - δT ... (6) The comparison unit 33 compares the minimum value of the charging time ΔT at the light receiving power P, ΔTmin(P), with the target charging time Treq (corresponding to the interval time between device uses) required in the system design.

[0052] If equation (6) above does not hold and "Treq - δT > ΔTmin(P)", the comparison unit 33 reduces the received light power P by ΔP and sets a new received light power (P - ΔP). That is, if the minimum value ΔTmin(P) is smaller than the allowable time set based on the target charging time Treq, it means that sufficient received light power is obtained in the photoelectric conversion circuit 22, so the received light power P is reduced to (P - ΔP). This is based on the fact that as the received light power P decreases, the minimum value of the charging time ΔTmin increases.

[0053] In other words, if the minimum value of one light-receiving power (light-receiving power P) is smaller than a predetermined range, the comparison unit 33 sets the other light-receiving powers to be lower than the first light-receiving power (P - ΔP).

[0054] If the above result is obtained by the comparison unit 33, the derivation unit 31 and the calculation unit 32 described above recalculate the relationship between the capacitor voltage Vc and the charging time ΔT with respect to the changed light-receiving power (P - ΔP).

[0055] Furthermore, if "ΔTmin(P) > Treq + δT", the light-receiving power P is increased by ΔP to set a new light-receiving power (P + ΔP). That is, if the minimum value ΔTmin(P) is greater than the allowable time set based on the target charging time Treq, it is presumed that sufficient light-receiving power cannot be obtained in the photoelectric conversion circuit 22, and that it takes a long time to reach the charging completion voltage VH, so the light-receiving power P is increased to (P + ΔP). This is based on the fact that as the light-receiving power P increases, the minimum value of the charging time ΔTmin decreases.

[0056] In other words, if the minimum value of one light-receiving power (light-receiving power P) is greater than a predetermined range, the comparison unit 33 sets the other light-receiving powers to be higher than the first light-receiving power (P + ΔP).

[0057] If the above result is obtained by the comparison unit 33, the derivation unit 31 and the calculation unit 32 described above recalculate the relationship between the capacitor voltage Vc and the charging time ΔT with respect to the changed light-receiving power (P + ΔP).

[0058] In other words, the comparison unit 33 determines whether the minimum value ΔTmin is within a predetermined range (Treq - δT to Treq + δT) based on the target charging time Treq. If the comparison unit 33 determines that the minimum value ΔTmin calculated by the calculation unit 32 for one light receiving power (for example, 5 [dBm]) is not within the predetermined range, it determines whether the minimum value ΔTmin calculated by the calculation unit 32 for another light receiving power (for example, 4 [dBm]) is within the predetermined range.

[0059] When increasing or decreasing the light-receiving power P, it may be changed repeatedly by a constant value (for example, 1.0 [dBm]) each time, or the value of ΔP may be decreased with each repetition. For example, it may be 1.0 [dBm] the first time, 0.9 [dBm] the second time, and so on, decreasing by 0.1 [dBm] each time.

[0060] When the setting unit 34 determines that the minimum value ΔTmin calculated by the calculation unit 32 satisfies equation (6) above, the comparison unit 33 acquires the light-receiving power P that results in this minimum value ΔTmin, and sets this light-receiving power P as the appropriate light-receiving power (referred to as "light-receiving power Px"). In other words, if the charging time ΔT is within the range of "Treq±δT", the setting unit 34 sets the light-receiving power P at this time to the appropriate light-receiving power Px. The setting unit 34 can calculate the recommended value VLmin for the charging start voltage VL and the recommended value VHmin for the charging end voltage VH when the charging time ΔT becomes the minimum value ΔTmin (P) that satisfies equation (6) above.

[0061] Based on various conditions related to optical communication, such as the line loss of the optical fiber 5 shown in Figure 1, the setting unit 34 sets the power of the power supply light output by the light source 1 provided at the in-house optical node 10 so that the received power P of the power supply light received by the photoelectric conversion circuit 22 becomes the received power Px described above.

[0062] If the setting unit 34 determines that the minimum value ΔTmin is within a predetermined range, it sets the received light power (Px as described above) at that time as the received light power that the photoelectric conversion circuit 22 receives.

[0063] The drive unit 35 outputs a control signal to the in-house optical node 10 so that the power of the supplied light is set in the setting unit 34, thereby driving the light source 1. Specifically, the drive unit 35 outputs a control signal to the in-house optical node 10 so that the power of the supplied light is set in the setting unit 34. The controller 4 of the in-house optical node 10 drives the light source 1 based on this control signal.

[0064] Next, the operation of the power supply system 100 configured as described above will be explained with reference to the flowchart shown in Figure 10. First, in step S11 of Figure 10, the derivation unit 31 obtains the target charging time Treq and the power consumption E of the device 7. The target charging time Treq corresponds to the interval time during device use.

[0065] In step S12, the derivation unit 31 calculates the relationship between the capacitor voltage Vc and the charging time when the received light power P received by the photoelectric conversion circuit 22 is the reference received light power P. As a result, the curve s1 shown in Figure 7 is obtained.

[0066] In step S13, the derivation unit 31 calculates multiple combinations of the capacitor voltage Vc (charging end voltage VH) at the start of operation of the device 7 and the capacitor voltage Vc (charging start voltage VL) at the end of operation, in the range of Vbottom to Vsatu, as shown in equation (4) above.

[0067] In step S14, the calculation unit 32 calculates the charging time ΔT with respect to the charging start voltage VL based on equation (5) described above. As a result, for example, the relationship shown in curve s23 in Figure 9 is obtained. Curve s23 is a graph showing the relationship between the voltage VL and the charging time ΔT when the light receiving power P = 5 [dBm].

[0068] In step S15, the calculation unit 32 calculates the minimum charging time ΔT based on the curve s23, and sets this as the minimum value ΔTmin(P).

[0069] In step S16, the comparison unit 33 compares the minimum value ΔTmin(P) with the target charging time Treq.

[0070] In step S17, the comparison unit 33 determines whether "ΔTmin(P) > Treq + δT". If "ΔTmin(P) > Treq + δT" (S16; YES), then equation (6) above is not satisfied, so in step S18, the light-receiving power P is changed to (P + ΔP) and the process returns to step S12.

[0071] In step S19, the comparison unit 33 determines whether "ΔTmin(P) < Treq - δT". If "ΔTmin(P) < Treq - δT" (S19; YES), then equation (6) above is not satisfied, so in step S20, the received light power P is changed to (P - ΔP) and the process returns to step S12.

[0072] Furthermore, if both steps S17 and S19 result in a NO determination, the above equation (6) is satisfied, and the process proceeds to step S21.

[0073] In step S21, the setting unit 34 sets the charging start voltage VL at the minimum value ΔTmin(P) to the recommended value VLmin, and the charging end voltage VH to the recommended value VHmin. In this way, when the power consumption of the device 7 and the target charging time Treq are determined, the appropriate light receiving power Px received by the photoelectric conversion circuit 22 can be set so that the charging time ΔT is equal to the target charging time Treq or within the range of "Treq±δT".

[0074] Subsequently, the setting unit 34 controls the power of the power supply light output from the light source 1 so that the received power of the power supply light received by the photoelectric conversion circuit 22 is Px. Specifically, by calculating the line loss that occurs in the optical fiber 5 connecting the nodes, the setting unit 34 sets the power of the power supply light output by the light source 1 to satisfy the received power Px.

[0075] The drive unit 35 outputs a control signal to the in-house optical node 10 so that the power of the supplied light is set in the setting unit 34. The controller 4 of the in-house optical node 10 drives the light source 1 according to this control signal. That is, the controller 4 sets the output value of the light source 1 so that the photoelectric conversion circuit 22 is supplied with supplied light that has an appropriate received light power, based on the received light power set in the setting unit 34 and the characteristics of the optical fiber 5 connecting the light source 1 and the optical node 20. As a result, the received light power P received by the photoelectric conversion circuit 22 can be set to an appropriate value.

[0076] As described above, the power supply system 100 according to this embodiment includes a light source 1 that outputs power supply light and an optical node 20 that receives the power supply light. The optical node 20 includes a photoelectric conversion circuit 22 that receives the power supply light and converts it into power, a capacitor C that charges the power, a derivation unit 31 that derives the charging time ΔT required for the charging voltage of the capacitor C to reach a predetermined charging end voltage VH from a predetermined charging start voltage VL as a function of the charging start voltage VL, in accordance with the received power P received by the photoelectric conversion circuit 22, a calculation unit 32 that calculates the minimum value ΔTmin of the charging time ΔT based on the function derived by the derivation unit 31, and the minimum value ΔTmin is the target charging The system further includes a comparison unit 33 that determines whether the time Treq is within a predetermined range, and if the comparison unit 33 determines that the minimum value ΔTmin calculated by the calculation unit 32 for one light-receiving power is not within the predetermined range, it determines whether the minimum value ΔTmin calculated by the calculation unit 32 for other light-receiving powers is within the predetermined range, and if it determines that the minimum value ΔTmin is within the predetermined range, it sets the light-receiving power at that time as the light-receiving power to be received by the photoelectric conversion circuit 22.

[0077] In the power supply system 100 according to this embodiment, when the power consumption of each device 7 and the interval time between device uses (charging time ΔT) are determined, the received power P of the power supply light received by the photoelectric conversion circuit 22 can be set to an appropriate power. Consequently, the power of the power supply light output by the light source 1 mounted on the in-house optical node 10 can be set to an appropriate power. Therefore, problems such as increased energy loss due to transmitting power supply light that is unnecessarily high can be avoided. In addition, it becomes possible to drive each device provided on the optical node 20 at a desired interval time.

[0078] In this embodiment, in the power supply system 100 shown in Figure 1, under conditions where the power consumption of device 7 and the required operating interval of device 7 are determined and operated accordingly, when the operating interval of device 7 is changed, the optimal light-receiving power P is recalculated. Based on the result of this recalculation, the optimal light-receiving power P for the changed operating interval can be obtained. In other words, even if the operating conditions of the system are changed, it is possible to readjust the light-receiving power from the power supply light to an appropriate value in response.

[0079] In this embodiment, it becomes possible to design the power supply system 100 based on the optimal light receiving power. For example, by calculating the line loss that occurs in the optical fiber 5 connecting the nodes, the power of the power supply light output by the light source 1 placed in the in-house optical node 10 can be set to an optimal value.

[0080] In this embodiment, the power of the power supply light output by the light source 1 can be set to the minimum, thus avoiding the output of excessive power and reducing power consumption. Furthermore, when the in-house optical node 10 is installed at an arbitrary distance from the optical node 20, the power of the power supply light output by the light source 1 can be set considering the line loss that occurs in the optical fiber between the in-house optical node 10 and the optical node 20, thereby enabling the operation of the optical node 20 in a location that meets system requirements.

[0081] In the embodiment described above, an example was given in which the control circuit 24 is mounted on the remote control board 6 shown in Figure 1. However, the control circuit 24 may also be mounted in the controller 4 of the in-house optical node 10. In this case, the in-house optical node 10 may query the optical node 20 for the capacitor voltage Vc. The controller 4 may also be configured to have a function for estimating the capacitor voltage Vc.

[0082] Furthermore, when the capacitor voltage Vc reaches the charging termination voltage VHmin (the charging termination voltage VH at which the charging time ΔT becomes the minimum value ΔTmin), a control signal for operating the device 7 may be transmitted from the in-house optical node 10 to the optical node 20. These control functions may also be implemented as software in the controller 4.

[0083] Alternatively, the controller 4 may be configured to calculate the loss value in the optical line, such as the optical fiber 5 between the optical node (in-house) and the optical node, based on the appropriate light receiving power Px described above, and to control the power of the supplied light output from the light source 1.

[0084] The loss values ​​in the optical path described above may be measured using an OTDR (Optical Time Domain Reflectometer). Furthermore, the OTDR measurement and the acquisition of the loss values ​​may be controlled by controller 4.

[0085] The control circuit 24 mounted on the optical node 20 of the above-described embodiment can use a general-purpose computer system, as shown in Figure 11, which includes, for example, a CPU (Central Processing Unit, processor) 901, memory 902, storage 903 (HDD: Hard Disk Drive, SSD: Solid State Drive), communication device 904, input device 905, and output device 906. The memory 902 and storage 903 are storage devices. In this computer system, each function of the control circuit 24 is realized when the CPU 901 executes a predetermined program loaded onto the memory 902.

[0086] The control circuit 24 may be implemented on one computer or on multiple computers. Furthermore, the control circuit 24 may be a virtual machine implemented on a computer.

[0087] The program for the control circuit 24 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 it can be distributed via a network. A computer-readable recording medium is, for example, a non-transitory recording medium.

[0088] This disclosure is not limited to the embodiments described above, and numerous modifications are possible within the scope of its essence.

[0089] 1 Light source 2 Optical circulator 3 Optical receiver 4 Controller 5 Optical fiber 6 Remote control board 7 (7-1 to 7-n) Devices 10 In-house optical node 20 Optical node 21 Communication device 22 Photoelectric conversion circuit 23 Charging circuit 24 Control circuit 31 Derivation unit 32 Calculation unit 33 Comparison unit 34 Setting unit 35 Drive unit 100 Power supply system C Capacitor E Power consumption VH Charging end voltage VL Charging start voltage

Claims

1. A power supply system comprising: a light source that outputs power supply light; and an optical node that receives the power supply light, wherein the optical node includes: a photoelectric conversion circuit that receives the power supply light and converts it into power; a capacitor that charges the power; a derivation unit that derives the charging time required for the charging voltage of the capacitor to reach a predetermined charging end voltage from a predetermined charging start voltage as a function of the charging start voltage, in accordance with the light received power received by the photoelectric conversion circuit; a calculation unit that calculates the minimum value of the charging time based on the function derived by the derivation unit; and a comparison unit that determines whether the minimum value is within a predetermined range based on a target charging time, wherein the comparison unit determines that the minimum value calculated by the calculation unit is not within the predetermined range for one light received power, and a setting unit that determines that the minimum value is within the predetermined range, sets the light received power at that time as the light received power received by the photoelectric conversion circuit.

2. The power supply system according to claim 1, wherein the comparison unit sets the other light-receiving power lower than the first light-receiving power if the minimum value of the first light-receiving power is smaller than the predetermined range, and sets the other light-receiving power higher than the first light-receiving power if the minimum value is larger than the predetermined range.

3. The power supply system according to claim 1 or 2, wherein the optical node comprises a device driven by the charging voltage of the capacitor, and the calculation unit calculates the minimum value assuming that the power consumption of the device is constant.

4. The power supply system according to claim 1 or 2, further comprising a controller that sets the output value of the light source so that power supply light, which becomes the light receiving power, is supplied to the photoelectric conversion circuit based on the light receiving power set in the setting unit and the characteristics of the optical fiber connecting the light source and the optical node.

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