JP2018064231A - Optical communication system and power supply method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical communication system and a power supply method that reduce the number of light sources, improve space efficiency, and reduce power consumption.SOLUTION: A master station transmits output light from a light source, and a slave station splits the light transmitted by the master station with an optical splitter, uses one of the split light as modulated light and uses the other for power supply. The present invention eliminates the necessity of separately providing a light source for power supply and a light source for modulated light in the master station, and thereby can save space and reduce power consumption.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to an optical communication system that supplies power from a master station to a slave station via an optical fiber, eliminates the need for a power supply source on the slave station side, and transmits information collected on the slave station side to the master station, and The present invention relates to a power supply method.

  In recent years, not only IP data communication but also IoT (Internet of Things) / M2M (Machine to Machine), 4K / 8K high-definition video distribution service, online video distribution service, video uploading by SNS, etc. Has become popular. In particular, not only information / communication equipment such as computers but also various “things” that exist in the world have communication functions, are connected to the Internet, and communicate with each other, so that automatic recognition, automatic control, remote measurement, etc. IoT is expected to expand dramatically due to a match between the needs of society due to social demands and the seeds of cheap devices.

  As an example of IoT, a predetermined physical quantity (current, voltage, atmospheric pressure, air temperature, water volume, humidity, etc.) is acquired at a remote location, and big data analysis is performed on these data on the center side, so that the analysis result can be renewed. There are scenes that can be used for business. Sensors are mainly used to collect various data at remote locations, but a power source is required to drive the sensors, and power is supplied to remote locations where power lines are not installed or where power lines cannot be used. As a power supply system for this purpose, an optical power supply system via an optical transmission line composed of an optical fiber is effective. The optical power feeding system has a configuration in which light energy is generated using a high-power laser light source on the power feeding side (master station), and photoelectric conversion is performed on the power feeding side (slave station) into electric energy by a PD (Photodiode) or a solar cell. A high conversion efficiency of about 30% has been reported. In recent years, 1W class communication lasers have been commercialized, and by combining them, it is possible to realize an optical power feeding system capable of supplying power of several hundred mW. In this way, the optical power feeding system supplies power to the sensor, etc. via the optical fiber, thereby eliminating the need for electrical wiring construction for power supply, laying of electrical supply facilities on site, lightning damage countermeasures, and electric noise countermeasures. There are many merits and various reports for realization have been made.

  For example, Patent Document 1 discloses a method using a multi-core fiber because there is a concern that the fiber connection portion may be damaged by high-power optical energy transmission. Patent Document 2 discloses a method of transmitting power and signal on the same fiber by wavelength division multiplexing: WDM (Wavelength Division Multiplexing).

JP 2014-042166 A Japanese Patent No. 4641787

  The concept of IoT is that various “things” are connected to the Internet, and information is exchanged and collected, so that data of “things” and automation based on it progress, creating new added value. . Therefore, in order to apply the optical power feeding system to IoT, a mechanism for feeding power to a sensor or the like arranged on the slave station side and transmitting information collected from the sensor or the like as an optical signal to the parent station is required.

  In Patent Document 1, a power feeding method is specified, but a method for transmitting data on a slave station side from a sensor device or the like to the master station side is not described. Japanese Patent Laid-Open No. 2004-228561 specifies a method in which a light source on the slave station side is not required by providing a light source on the master station side in advance in order to transmit data collected on the slave station side to the center side. However, in Patent Document 2, it is necessary to provide a power supply laser light source on the master station side and a laser light source for transmitting data collected on the slave station side to the center side. There was a problem of inefficiency from the viewpoint.

  SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to provide an optical communication system and a power feeding method that reduce the number of light sources, improve space efficiency, and reduce power consumption.

  In order to achieve the above object, an optical communication system and a power supply method according to the present invention transmit supply light from a master station to a slave station, a part of the supply light is modulated light of an upstream signal, and the other is supply light. I decided to receive it.

Specifically, the optical communication system according to the present invention is an optical communication system in which a master station and a slave station are connected by an optical transmission line,
The master station comprises a transmission means for transmitting supply light including modulated light for an uplink signal from the slave station to the master station to the slave station,
The slave station modulates the modulated light branched by the optical splitter and splits the supplied light from the master station into the modulated light and power supply light, and transmits the modulated light to the master station. And a photoelectric converter that receives the feed light branched by the optical splitter and converts it into electric power.

Specifically, the power supply method according to the present invention is a power supply method for supplying power to the slave station using light in an optical communication system in which a master station and a slave station are connected by an optical transmission line,
A transmission procedure for transmitting supply light including modulated light for an uplink signal from the slave station to the master station from the master station to the slave station;
An optical branching procedure for splitting the supply light from the master station into the modulated light and the feed light;
An optical modulation procedure for modulating the modulated light branched in the optical branching procedure and transmitting the modulated light to the master station;
A photoelectric conversion procedure for receiving the power supply light branched in the optical branching procedure and converting it into electric power;
It is characterized by performing.

  In the present invention, the master station transmits the output light from the light source, the slave station splits the light transmitted from the master station by the optical splitter, uses one of the branched lights as the modulated light, Light is used for power supply. According to the present invention, it is not necessary to separately provide a power source for power supply and a light source for modulated light in the master station, and space saving and low power consumption can be achieved.

  Therefore, the present invention can provide an optical communication system and a power feeding method that reduce the number of light sources, improve the space efficiency and reduce power consumption.

  The slave station of the optical communication system according to the present invention further includes a power storage circuit that stores electric power photoelectrically converted by the photoelectric converter. The drive power range of the sensor connected to the slave station can be changed from the photoelectric converter rate limit to the capacity limit rate of the power storage circuit, and it becomes possible to operate a sensor or a plurality of sensor groups with large power consumption.

  The slave station of the optical communication system according to the present invention further includes a bias circuit that converts electric power photoelectrically converted by the photoelectric converter into a bias voltage and applies the bias voltage to the optical modulator. By applying a constant bias voltage to the modulator, individual differences in the optimum bias voltage of the optical modulator can be absorbed.

  The optical transmission line of the optical communication system according to the present invention transmits a path for transmitting the supplied light from the transmission means to the slave station and light modulated from the modulated light from the optical modulator to the master station. The route is different. When the master station and the slave station are connected by a single path (for example, single-core bidirectional transmission), an optical circulator and a directional coupler are required for both the master station and the slave station. When the downstream path from the master station to the slave station and the upstream path from the slave station to the master station are separated (for example, a two-core configuration), an optical circulator or a directional coupler is not required, and modulation from the slave station Crosstalk with respect to signals can be reduced, and the cost for optical circulators and directional couplers can be reduced.

  The present invention can provide an optical communication system and a power supply method that can reduce the number of light sources, improve space efficiency, and reduce power consumption.

It is a figure explaining the optical communication system which concerns on this invention. It is a figure explaining operation | movement of the optical communication system which concerns on this invention. It is a figure explaining the optical communication system which concerns on this invention. It is a figure explaining the optical communication system which concerns on this invention.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

(Embodiment 1)
FIG. 1 is a configuration diagram illustrating an optical communication system 301 of the present embodiment. An optical communication system 301 is an optical communication system in which a master station 10 and a slave station 20 are connected by an optical transmission line 30,
The master station 10 includes transmission means (light source 11) for transmitting supply light including modulated light for an uplink signal from the slave station 20 to the master station 10 to the slave station 20,
The slave station 20 modulates the modulated light branched by the optical splitter 21 to the master station 10 by optically splitting the supplied light from the master station 10 into the modulated light and the feeding light. An optical modulator 23 for transmission, and a photoelectric converter 22 that receives the feed light branched by the optical splitter 21 and converts it into electric power are provided.

  The master station 10 includes transmission means (light source 11) that transmits to the slave station 20 light including power supply light for supplying power to the photoelectric converter 22 and modulated light from the slave station 20 to the master station 10. The slave station 20 modulates the light transmitted from the master station 10 by the loopback and the optical splitter 21 that distributes the light intensity to the feed light and the modulated light, and the modulated light that is distributed by the optical splitter 21. And an optical modulator 23 for transmitting to the master station 10 and a photoelectric converter 22 for receiving the power supply light distributed by the optical splitter 21 and converting it into electric power. The slave station 20 is connected to a sensor 40 that collects information. A broken line in the figure indicates an electric signal, and a solid line indicates an optical signal path.

  In the case of this embodiment, the transmission means of the master station 10 is the light source 11 that outputs the feeding light and the modulated light. The light source 11 is not limited as long as it is a light source that can be coupled to an optical fiber. For example, an LD (Laser Diode) is used for a coherent light source, and an ASE (Amplified Spontaneous Emission) light source is used for an incoherent light. It is done. Light from the light source 11 is output to the optical transmission line 30 via the optical circulator 12. The upstream signal modulated with the sensing data from the sensor 40 is received by the optical receiver 13 via the optical circulator 12. Here, the optical circulator 12 is used as an example for the coupling between the light from the light source 11 and the transmission path 30, and the coupling between the upstream signal from the optical transmission path 30 and the optical receiver 13, but the present invention is not limited thereto. A similar effect can be obtained by using a directional coupler (optical coupler).

  On the other hand, the optical splitter 21 of the slave station 20 includes a port that outputs light transmitted from the master station 10 to the power feeding side with a predetermined branching ratio, and a port that outputs light to the modulated side. For example, when the branching ratio of the optical splitter 21 is 90:10 (feeding side: modulated side), 90% of the transmitted light intensity is distributed to the feeding side, and the remaining 10% is distributed to the modulated side. . The photoelectric converter 22 receives light from the power supply side port of the optical splitter 21, converts it into electric power, and supplies it to each device and sensor 40 of the slave station 20. The optical modulator 23 modulates light from the modulated side port of the optical splitter 21 into an optical signal with data from each sensor 40. The optical circulator 24 couples light from the optical transmission line 30 to the optical splitter 21 and couples an upstream signal from the optical modulator 23 to the optical transmission line 30. Here, the optical circulator 24 is given as an example for the coupling between the light from the transmission path 30 and the optical splitter 21, and the coupling between the upstream signal from the optical modulator 23 and the optical transmission path 30, but the present invention is not limited to this. A similar effect can be obtained with a directional coupler (optical coupler).

  In the above configuration, the light transmitted from the light source 11 installed in the master station 10 is sent to the optical fiber transmission line 30 via the master station side optical circulator 12. The optical signal reaching the slave station 20 is distributed in light intensity at a predetermined branching ratio to the feed light and the modulated light by the optical splitter 21 via the slave station side optical circulator 24.

  The modulated light to which the light intensity is distributed by the optical splitter 21 is modulated into an optical signal by an electrical signal from various sensors 40 by the optical modulator 23, and the slave station side optical circulator 24, the optical fiber transmission line 30, The signal is received by the optical receiver 13 via the station side optical circulator 12. Here, the photoelectric converter 22 functions as a current source that converts an optical signal into a current, and examples thereof include a solar cell and a PD. The optical modulator 23 is not limited as long as it can modulate the intensity of the light input by the electrical signal from the sensor 40 and convert it into an optical signal. LN (Lithium−) utilizing the electro-optic effect is not limited. Examples thereof include an optical gate using Niobate) or MEMS (Micro Electro Mechanical Systems).

  FIG. 2 shows a spectrum and a waveform in the frequency / time domain up to the points A to F in FIG. Here, the light source is an LD light source (wavelength λ1), and the branching ratio of the optical splitter 21 is 90:10. The symbol α in the figure indicates the sum of the transmission loss in the optical circulators 12 and 24 and the transmission path loss in the optical transmission path 30.

  The optical communication system 301 is effective in reducing the number of laser light sources installed in the master station 10, improving the space efficiency of the master station 10, reducing power consumption, and providing all power supply sources to the slave stations 20. It can be unnecessary.

(Embodiment 2)
FIG. 3 is a configuration diagram illustrating the optical communication system 302 of the present embodiment. The difference between the optical communication system 302 and the optical communication system 301 in FIG. 1 is that a path 30a for transmitting the supplied light from the master station 10 to the slave station 20 and a modulation from the slave station 20 to the master station 10 by the optical modulator 23. That is, the path 30b for transmitting the signal light is different. The optical communication system 302 does not have an optical circulator or a directional coupler, and includes a dedicated path 30b for transmitting an upstream signal modulated with sensing data from the sensor 40.

  The optical circulator is generally composed of three ports. Light incident on the port 1 is emitted from the port 2, and light incident on the port 2 is emitted from the port 3. In the first embodiment, the optical circulator 12 installed on the master station 10 side has the port 1 connected to the light source 11, the port 2 connected to the optical transmission line 30, and the port 3 connected to the receiver 13. . Ideally, the optical circulator does not output light from port 1 to port 3 (referred to as directivity), but the directivity has a finite value, and a part of the signal transmitted from the master station 10 is optical circulator. 12 is input to the receiver 13 as leaked light. This is a crosstalk for the upstream signal modulated by the sensing data from the sensor 40, and causes a deterioration in reception sensitivity. Since the directional coupler also has a finite directivity value in the same manner as the optical circulator, a part of the signal transmitted from the master station 10 is input to the receiver 13 as leakage light and modulated upstream. For signals, this is crosstalk.

  The present embodiment solves the above-mentioned problem, and by eliminating the optical circulators 12 and 24, it provides a more economical optical communication system and crosstalk that causes the reception sensitivity to deteriorate. It is possible to eliminate. The operation principle is the same as that of the optical communication system 301, and thus the description thereof is omitted.

  The optical communication system 302 is effective in reducing the number of light sources installed in the master station 10, increasing the space efficiency of the master station 10 and reducing power consumption, and does not require any power supply source to the slave station 20. By eliminating the optical circulator and the directional coupler, it is possible to provide a more economical optical communication system and to eliminate crosstalk caused by leakage of the optical circulator and the directional coupler.

(Embodiment 3)
FIG. 4 is a configuration diagram illustrating the optical communication system 303 of the present embodiment. A difference between the optical communication system 303 and the optical communication system 301 in FIG. 1 is that a bias circuit 25 and a power storage circuit 26 (for example, a capacitor) are added to the slave station 20. The slave station 20 further includes a power storage circuit 26 that stores the power photoelectrically converted by the photoelectric converter 22, and a bias circuit 25 that converts the power photoelectrically converted by the photoelectric converter 22 into a bias voltage and applies the bias voltage to the optical modulator 23. Prepare.

  As described in the first embodiment, the optical modulator 23 is mainly an LN modulator. It is known that the transmission characteristic of the LN modulator is proportional to the square of the cosine of the applied voltage (DC bias voltage). For this reason, when using an LN modulator, the DC bias point is generally set to a transmittance of 50%. Usually, the optimum voltage of the DC bias voltage of the LN modulator has individual differences, and depending on the LN modulator, there is a possibility that modulated light is not output when the applied voltage is 0 V (transmittance 0%). Therefore, the optical communication system 303 uses part of the power generated by the photoelectric converter 22 to generate a DC bias voltage by the bias circuit 25 and applies it to the optical modulator 23.

In addition, the drive power range of the various sensors 40 is rate-determined by the photoelectric converter 22, but depends on the capacity of the power storage circuit 26 by including the power storage circuit 26. For example, assuming that the photoelectric converter 22 is a constant current source of 20 mA, the capacity value of the power storage circuit 26 is 10 ⁴ μF, and the charging time is 10 s, a voltage of 20 V is obtained. By providing the power storage circuit 26 as described above, it is possible to operate a sensor with a large power consumption or a plurality of sensor groups.

  The optical communication system 303 is effective in reducing the number of laser light sources installed in the master station 10, improving the space efficiency of the master station 10, reducing power consumption, and providing all power supply sources to the slave stations 20. It can be made unnecessary and independent of the electric power of the photoelectric converter 22 by providing the power storage circuit 26. The power storage circuit 26 and the bias circuit 25 described in the present embodiment can also be applied to the configuration of the optical communication system 302 described in the second embodiment.

(effect)
The present invention eliminates the need for a power supply laser light source on the master station side in a loopback type optical power supply system that does not require a power supply source and a data collection light source for sensors installed on the slave station side. With a simple configuration on the station side, space efficiency and power consumption can be reduced.

10: Master station 11: Light source 12: Optical circulator 13: Optical receiver 20: Slave station 21: Optical splitter 22: Photoelectric converter 23: Optical modulator 24: Optical circulator 25: Bias circuit 26: Power storage circuits 30, 30a 30b: Optical transmission line 40: Sensors 301 to 303: Optical communication system

Claims (5)

An optical communication system in which a master station and a slave station are connected by an optical transmission line,
The master station is
Transmitting means for transmitting supply light including modulated light for an uplink signal from the slave station to the master station to the slave station,
The slave station is
An optical splitter that splits the supply light from the master station into the modulated light and the feed light;
An optical modulator that modulates the modulated light branched by the optical splitter and transmits the modulated light to the master station;
A photoelectric converter that receives the feed light branched by the optical splitter and converts it into electric power;
An optical communication system comprising: The slave station is
The optical communication system according to claim 1, further comprising a power storage circuit that stores electric power photoelectrically converted by the photoelectric converter. The slave station is
The optical communication system according to claim 1, further comprising a bias circuit that converts electric power photoelectrically converted by the photoelectric converter into a bias voltage and applies the bias voltage to the optical modulator. The optical transmission line is
4. A path for transmitting the supplied light from the transmitting means to the slave station is different from a path for transmitting light modulated from the modulated light from the optical modulator to the master station. An optical communication system according to any one of the above. In a power supply method for supplying power to the slave station using light in an optical communication system in which a master station and a slave station are connected by an optical transmission line,
A transmission procedure for transmitting supply light including modulated light for an uplink signal from the slave station to the master station from the master station to the slave station;
An optical branching procedure for splitting the supply light from the master station into the modulated light and the feed light;
An optical modulation procedure for modulating the modulated light branched in the optical branching procedure and transmitting the modulated light to the master station;
A photoelectric conversion procedure for receiving the power supply light branched in the optical branching procedure and converting it into electric power;
A power feeding method characterized in that

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