JPH1189120A - Optical power transmitting method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical power transmitting method and its device which make it possible to use energy efficiently by stably supplying only the power required by a load. SOLUTION: A laser 1 converts electric power into optical power which is transmitted through an optical fiber 3. When the optical power is converted again into electric power with a solar cell 4, a drive device 2 in which the laser 1 controls an output is provided. A capacitor 5 is placed between the solar cell 4 and a load 6, and a voltage across the capacitor 5 is detected. Control signals are fed back to the drive device 2 based on the detected value to control the optical power oscillated by the laser 1. The control signals which are optical signals of a different frequency from that of the optical power are fed back through the same optical fiber for transmitting the optical power. Also, the control signals are optical on-off signals so that the optical power oscillated by the laser 1 is controlled by the change of the ratio of 'on' time to 'off' time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for transferring power through an optical fiber, and more particularly, to converting power into optical power, transmitting the power through an optical fiber, and transmitting the optical power after transmission. The present invention relates to an optical power transmission method and a device for re-converting the power to power and supplying the re-converted power to a load.

FIG. 1 is a diagram schematically showing a conventional optical power transmission device. In the figure, 1 is a laser for converting electric power to optical power, 3 is an optical fiber for transmitting optical power, 4 is a solar cell for converting optical power to electric power, 6 is a load, solid arrows indicate power transmission, The dotted arrows indicate the transmission of optical power, respectively. In this case, the optical power converted from electricity into light by the laser 1 is transmitted to the solar cell 4 via the optical fiber 3.
Is transmitted to The transmitted optical power is converted into electric power by the solar cell 4 and supplied to the load 6.

In such a conventional method, a constant power is always supplied irrespective of the power required by the load, so that more power than necessary or insufficient power may occur. There was a problem.

[0004]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an optical power transmission method and apparatus which stably supplies only the power required by a load and enables effective use of energy. To provide.

[0005]

In order to achieve the above object, an optical power transmission method according to the present invention converts power into optical power using a laser, transmits the optical power through an optical fiber, and transmits the optical power. An optical power transmission method for converting optical power into electric power using a photoelectric conversion device and supplying the reconverted electric power to a load, comprising a drive device for controlling an output by a laser, wherein a drive device between the photoelectric conversion device and the load is provided. A capacitor is added to the power supply, a value of power, voltage and / or current charged and discharged by the capacitor is detected, and a control signal is fed back to the drive device based on the detected value, and the optical signal generated by the laser is oscillated by the control signal. The control is performed.

An optical power transmission device according to the present invention includes a laser for converting electric power to optical power, an optical fiber for transmitting optical power, and a photoelectric conversion device for converting the transmitted optical power back to electric power. An optical power transmission device configured to supply re-converted power to a load, a drive device that controls laser output, a capacitor disposed between the photoelectric conversion device and the load, And a feedback control circuit that detects a value of power, voltage and / or current when the capacitor is charged and discharged, and feeds back a control signal to a drive device based on the detected value.

In this case, when the power required by the load becomes large and the power from the photoelectric conversion device becomes insufficient, the power is discharged from the capacitor and the terminal voltage of the capacitor decreases. Control to increase the optical power oscillated from the
On the other hand, if the power required by the load becomes small and the power from the photoelectric conversion device has a margin, the capacitor is charged and the terminal voltage of the capacitor rises, so the light oscillated from the laser to cancel this voltage rise What is necessary is just to perform control for reducing power.

[0008] In the present invention, the photoelectric conversion device is preferably a solar cell. Further, it is desirable to use an optical signal as a control signal to be fed back to the laser drive device and feed it back through an optical fiber. By doing so, the laser side and the solar cell side can be electrically insulated and stable control can be performed. When feeding back through optical fiber,
If the optical power and the control signal to be fed back to the drive device are used at different frequencies, they can be transmitted through the same optical fiber.

Further, in the present invention, it is preferable that the control signal fed back to the drive device is an optical on / off signal, and that the optical power generated by the laser is controlled by changing the on / off time ratio.
In this way, the control optical signal can be transmitted stably without being affected by the length and loss of the optical fiber.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a view for explaining a first embodiment of the present invention. In the figure, reference numeral 1 denotes a laser for converting electric power to optical power;
2 is a drive device for controlling the output of the laser, 3 is an optical fiber for transmitting optical power, 4 is a solar cell for converting optical power into electric power, 5 is a capacitor, 6 is a load, and 7 is a feedback control circuit.

In the system shown in FIG. 2, electric power is converted into optical power by a laser 1, and this optical power is input from the left end of the optical fiber 3 in the drawing. The optical power incident on the optical fiber 3 is transmitted to the right end of the optical fiber. Then, the optical power enters the solar cell 4 from the right end of the optical fiber 3 and is converted into electric power by the solar cell 4. This power is charged to the capacitor 5 and supplied to the load 6.

When the power required by the load 6 changes, the balance between the supply and demand of the power between the solar cell 4 and the load 6 changes, thereby changing the power stored in the capacitor 5. The feedback control circuit 7 detects this change, performs signal processing on the detection result, and sends a signal for controlling the optical power in accordance with the power required by the load to the drive device 2 that controls the output of the laser. The optical power of the laser 1 is controlled. In particular,
When the terminal voltage of the capacitor 5 decreases, the optical power of the laser 1 is increased, and when the terminal voltage of the capacitor 5 increases, the optical power of the laser 1 is controlled to decrease.

FIG. 3 is a view for explaining a second embodiment of the present invention. In FIG. 3, reference numeral 3 'denotes an optical fiber, 8 denotes an electro-optical conversion circuit for converting an electric signal to an optical signal, and 9 denotes an electric signal. The photoelectric conversion circuit converts the signal into a signal, and the other reference numerals represent the same parts as those in FIG.

In the system shown in FIG. 3, the power is converted into optical power by the laser 1, this optical power enters from the left end of the optical fiber 3 in the drawing, is transmitted to the right end, and is transmitted from the right end of the optical fiber 3. Incident on the solar cell 4,
Here, it is converted into electric power, and the electric power is charged to the capacitor 5 and supplied to the load 6 in the same manner as in the first embodiment. Further, when the power required by the load 6 changes, the power stored in the capacitor 5 changes,
The detection of this change by the feedback control circuit 7 is the same as in the first embodiment.

In this embodiment, signal processing is performed on the detection result, and the electric signal is input to an electro-optical conversion circuit 8 to be converted into an optical signal, and the converted optical signal is transmitted through an optical fiber 3 '. The signal is input to the electric conversion circuit 9 and converted into an electric signal again here. The electric signal is sent to a drive device 2 for controlling the output of the laser, and the optical power of the laser 1 is controlled. By doing so, the laser side and the solar cell side can be electrically insulated.

FIG. 4 is a view for explaining a third embodiment of the present invention. In the figure, reference numerals 10 and 11 denote optical input / output devices for inputting, outputting, and demultiplexing two lights having different frequencies to an optical fiber. And the other reference numbers represent the same parts as in FIGS.

In the system shown in FIG. 4, the power is converted into optical power by the laser 1, this optical power enters from the left end of the optical fiber 3 in the drawing, is transmitted to the right end, and is transmitted from the right end of the optical fiber 3. Incident on the solar cell 4,
Here, the power is converted to electric power, and the electric power is charged to the capacitor 5 and supplied to the load 6 according to the first and second embodiments.
In addition, when the power required by the load 6 changes, the power stored in the capacitor 5 changes, and the feedback control circuit 7 detects this change in the first and second embodiments. Is the same as

In this embodiment, signal processing is performed on the detection result, and the electric signal is further input to an electro-optical conversion circuit 8 to be converted into an optical signal.
The light enters the optical fiber 3 via the optical input / output device 11. The control optical signal transmitted through the optical fiber 3 is input to the photoelectric conversion circuit 9 via the optical input / output unit 12, where it is converted into an electric signal again. The electric signal is sent to a drive device 2 for controlling the output of the laser, and the optical power of the laser 1 is controlled.

FIG. 5 is a diagram showing an example of the frequency of light transmitted by an optical fiber. It is necessary to use a laser of a level corresponding to the required power as the laser 1 for transmitting optical power, but when using a semiconductor laser,
A semiconductor laser (LD1) that oscillates around a wavelength of 800 nm as capable of transmitting several watts of class
Is used. On the other hand, it is necessary to prevent the control optical signal from being interfered with by other optical signals, so that it is necessary to avoid a wavelength around 800 nm. Furthermore, since the control optical signal does not require a high output, a low-power semiconductor laser (LD2) that oscillates at around 1300 nm is used as a laser in the electro-optical conversion circuit 8 that converts an electric signal into an optical signal. I do. Since the light oscillating from the LD1 and the light oscillating from the LD2 have different frequencies, there is no possibility that they interfere with each other, and the control signal can be transmitted accurately even if one optical fiber is used for both.

FIG. 6 is a diagram showing a waveform of a control optical signal in the optical fiber 3 of FIG. Here, as a control signal from the feedback control circuit 7, a signal having a rectangular wave and a predetermined on / off time ratio within a certain period is used, and such an electric signal is converted into an optical signal and transmitted through an optical fiber. FIG. 6 shows the waveforms of the optical signals at the points a1 and a2. However, in the optical fiber, the light intensity is attenuated as the light travels through the optical fiber due to internal loss. But,
Since the time ratio of ON (TON) and OFF (TOFF) within a certain period does not change, a control signal can be transmitted accurately even if the transmission distance of the optical fiber changes.

FIG. 7A is a diagram showing an embodiment of the feedback control circuit 7, and FIG. 7B is a diagram showing an embodiment of the drive device 2 for controlling the output of the laser. FIG.
(a) The feedback control circuit 7 inputs the voltage V1 of the capacitor 5 to one input terminal of the difference amplifier 7a. In the differential amplifier 7a, the voltage V1 of the capacitor 5 and the reference voltage source 7b
Is amplified to an appropriate value to obtain an output voltage V2. Next, the output voltage V2 from the differential amplifier 7a is compared with a comparator 7d.
, And the output voltage V3 of the triangular wave generator 7c is input to, for example, a negative input terminal of the comparator 7d.
In the comparator 7d, for example, when the value of the voltage signal of the negative input terminal is larger than that of the voltage signal of the positive input terminal, the comparator 7d outputs the ON-level voltage signal V4, When the value of the voltage signal is small, an off-level voltage signal V4 is output.

The output voltage signal V4 of the comparator 7d passes through the electro-optical conversion circuit 8, the optical fiber 3 and the opto-electric conversion circuit 9 as shown in FIG.
Of the switch 2b. The switch 2b is closed by an on-level signal and is opened by an off-level signal. 2a is a current source.

FIGS. 8, 9 and 10 are waveform diagrams for explaining the operation of controlling the power of the laser 1 by detecting the voltage fluctuation of the capacitor 5 due to the fluctuation of the load 6, as in the case of FIG. V1 is the voltage of the capacitor 5, V2 is the differential amplifier
The output voltage of 7a, V3 is the output voltage of triangular wave generator 7c, V4
Is the output voltage of the comparator 7d. FIG. 11 is a diagram showing the current-voltage characteristics of the output of the solar cell 4. In this figure, the point that operates stably first is point a.

FIG. 8 shows a case where the load 6 does not fluctuate, and the voltages V1 and V2 have constant values. Therefore, V4, which is the result of comparing the voltage values V2 and V3 with the comparator 7d, is shown.
Is a rectangular wave voltage maintaining a constant on / off time ratio.
Here, the on / off time ratio is a value obtained by dividing the on time (TON) by one cycle of the rectangular wave voltage (TON + TOFF). If this is D, this signal becomes a drive signal for the switch 2b. A constant optical power P such as P = D · Po is output. Here, Po represents a constant power during continuous oscillation. From this equation, if D is constant, laser 1
Output a constant optical power. Therefore,
Since the light power P incident on the solar cell 4 in FIG. 11 is constant, the operating point of the solar cell 4 is point a (voltage Eo, current Ia
) And outputs the power (Eo × Ia) determined at point a.

FIG. 9 shows a case where the power required by the load 6 has increased, and V1 has decreased, and accordingly, V1 has decreased.
V2, which is a voltage obtained by amplifying the difference between 1 and E, also decreases. For this reason, the on-level time is longer in the rectangular wave of V4, which is the result of comparing the voltage values V2 and V3 with the comparator 7d. That is, the on / off time ratio D increases. At this time, since the optical power oscillated by the laser 1 increases from the above equation P = D · Po, the operating point of the solar cell 4 in FIG. 11 is changed from point a (voltage Eo, current Ia) to point b (voltage Eo). ,
To the current Ib) and the power determined at the point b (Eo × Ib)
To change the output.

FIG. 10 shows a case where the power required by the load 6 is reduced. V1 increases, and accordingly, V2, which is a voltage obtained by amplifying the difference between V1 and E, also increases. For this reason, in the rectangular wave of V4, which is the result of comparing the voltage values V2 and V3 with the comparator 7d, the on-level time becomes shorter. That is, the on / off time ratio D decreases. At this time, since the optical power oscillated by the laser 1 becomes smaller from the above equation P = D · Po, the operating point of the solar cell 4 in FIG. 11 is changed from the point a (voltage Eo, current Ia) to the point c (voltage Eo). ,
Current Ic) and the power determined at point c (Eo × Ic)
To change the output.

[0027]

As described in detail above, the present invention provides
Since a feedback system for performing power control is added to the optical power transmission device, only the power required by the load can be transmitted, so that the power can be effectively used and the overall energy efficiency can be improved.

According to the present invention, the system can be completely insulated by transmitting the optical power through the optical fiber and the control optical signal through the optical fiber at the same time. Further, by setting the optical power and the frequency of the control signal to different values, interference between the two can be prevented, and the power light and the control signal light can be transmitted by one optical fiber. Furthermore, feedback is performed so that the voltage reflecting the charge amount of the capacitor on the solar cell side is kept constant,
Since the method of changing the optical power of the output on the laser side according to the fluctuation of the load is adopted, it is possible to easily and stably control the optical power.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a conventional optical power transmission device.

FIG. 2 is a diagram illustrating a first embodiment of the present invention.

FIG. 3 is a diagram illustrating a second embodiment of the present invention.

FIG. 4 is a diagram illustrating a third embodiment of the present invention.

FIG. 5 is a diagram illustrating an example of a frequency of light transmitted by an optical fiber.

6 is a diagram showing a waveform of a control optical signal in the optical fiber of FIG.

FIG. 7 is a diagram showing an embodiment of a feedback control circuit and a drive device for controlling the output of the laser.

FIG. 8 is a waveform diagram illustrating an operation of controlling laser power when there is no change in load.

FIG. 9 is a waveform diagram illustrating an operation of detecting voltage fluctuation of a capacitor and controlling laser power when the power required by a load increases.

FIG. 10 is a waveform diagram illustrating an operation of detecting a voltage change of a capacitor and controlling laser power when the power required by a load is reduced.

FIG. 11 is a diagram showing current-voltage characteristics of the output of a solar cell.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 laser 2 laser drive device 3 optical fiber 4 solar cell 5 capacitor 6 load 7 feedback control circuit 8 electro-optical conversion circuit 9 opto-electric conversion circuit 10, 11 optical input / output device 7a difference amplifier 7b reference voltage source 7c triangular wave generator 7d Comparator 2a Current source 2b Switch

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Seiichi Muroyama 3-19-2 Nishi Shinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (11)

[Claims] An optical power is converted into an optical power by using a laser, the optical power is transmitted through an optical fiber, the transmitted optical power is re-converted into an electric power by using a photoelectric conversion device, and the re-converted power is converted. An optical power transmission method for supplying to a load, comprising a drive device for controlling an output by a laser, adding a capacitor between the photoelectric conversion device and the load, and values of power, voltage and / or current charged and discharged by the capacitor. And transmitting a control signal to a drive device based on the detected value, and controlling the optical power generated by the laser based on the control signal. 2. The optical power transmission method according to claim 1, wherein an optical signal is used as a control signal to be fed back to the drive device, and the control signal is fed back through an optical fiber. 3. The optical power transmission method according to claim 2, wherein the optical power and the control signal fed back to the drive device are transmitted through the same optical fiber using lights of different frequencies. Optical power transmission method. 4. The optical power transmission method according to claim 1, wherein the voltage of the capacitor is monitored by a feedback control circuit, and when the voltage decreases, the output power of the laser is increased. Control signal,
An optical power transmission method, wherein when the voltage rises, a control signal for decreasing the output power of the laser is fed back to the drive device. 5. The optical power transmission method according to claim 1, wherein the control signal fed back to the drive device is a light on / off signal, and the laser is oscillated by a change in the on / off time ratio. An optical power transmission method characterized by controlling optical power to be transmitted. 6. A laser for converting electric power to optical power,
An optical power transmission device comprising: an optical fiber for transmitting optical power; and a photoelectric conversion device for converting the transmitted optical power into electric power, wherein the reconverted electric power is supplied to a load. A drive device that controls the output of the capacitor, a capacitor disposed between the photoelectric conversion device and the load, and a value of power, voltage, and / or current when the capacitor is charged and discharged. An optical power transmission device comprising: a feedback control circuit that feeds back a control signal to a drive device based on the feedback control circuit. 7. The optical power transmission device according to claim 6, wherein the photoelectric conversion device is a solar cell. 8. The optical power transmission device according to claim 6, wherein an electro-optical conversion circuit that converts a control signal output from the feedback control circuit into an optical signal, and a control signal that is converted into an optical signal. An optical power transmission device comprising: an optical fiber for transmission; and an opto-electrical conversion circuit for re-converting a control signal converted into an optical signal into an electric signal and outputting the electric signal to a drive device. 9. The optical power transmission device according to claim 8, wherein the electro-optical conversion circuit can convert the control signal into an optical signal having a frequency different from that of the output light of the laser. And an optical input / output device capable of transmitting output light of the laser and a control signal converted into an optical signal by the electro-optical conversion circuit through the same optical fiber. 10. The optical power transmission device according to claim 6, wherein the feedback control circuit monitors the voltage of the capacitor, and when the voltage decreases, reduces the output power of the laser. An optical power transmission device configured to output a control signal to increase the output signal and to output a control signal to decrease the output power of the laser when the voltage increases. 11. The optical power transmission device according to claim 6, wherein the output light of the electro-optical conversion circuit is an on / off signal of light, and the drive device includes an electro-optical conversion circuit. An optical power transmission device configured to control the optical power generated by a laser according to a change in an on / off time ratio of output light.