Patent Description:
Recently, there has been studied an optical power supply system that converts electric power into light (called feed light), transmits the feed light, converts the feed light into electric energy, and uses the electric energy as electric power.

PTL <NUM> discloses an optical communication device including an optical transmitter, an optical fiber, and an optical receiver. The optical transmitter transmits signal light modulated based on an electric signal and feed light for supplying electric power. The optical fiber includes a core, a first cladding surrounding the core, and a second cladding surrounding the first cladding. The core transmits the signal light. The first cladding has a refractive index lower than that of the core and transmits the feed light. The second cladding has a refractive index lower than that of the first cladding. The optical receiver operates with electric power obtained by converting the feed light transmitted through the first cladding of the optical fiber and converts the signal light transmitted through the core of the optical fiber into the electric signal. PTL <NUM> discloses a power-over-fiber system according to the preamble of claim <NUM>. PTL <NUM> discloses an optical power feeding device equipped with an optical power generating means which generates optical power, an electric power supply means which supplies electric power to the optical power generating means, a photoelectric transfer means which transfers the optical power into the electric power and a storage means, which stores the electric power obtained through the transfer by the photoelectric conversion means, and supplies a load device with the electric power obtained through the transfer by the means or the electric power stored in the storage means. The device is equipped with a means for detecting voltage values at the opposite ends of the storage means and an optical power control means, which controls the strength of the optical power on the basis of the detected voltage values. PTL <NUM> discloses optically powered radio-over-fiber remote units for distributed antenna system applications using separate fibers for power and signal transmissions.

PTL <NUM>: <CIT>; PTL <NUM>: <CIT>; PTL <NUM>: <CIT>; PTL <NUM>: <NPL>.

In optical power supply, further improvement in optical power supply efficiency is desired. As one form of the improvement, improvement in photoelectric conversion efficiency on a power-sourcing side and a powered side is desired.

A power-over-fiber system according to one aspect of the present disclosure includes.

<FIG> do not show each and every feature of claim <NUM>.

One embodiment of the present disclosure is described below with reference to the drawings.

As illustrated in <FIG>, a power-over-fiber (PoF) system 1A according to the present embodiment includes a power sourcing equipment (PSE) <NUM>, an optical fiber cable 200A, and a powered device (PD) <NUM>.

In the present disclosure, the power sourcing equipment is a device that converts electric power into optical energy and supplies the optical energy, and the powered device is a device that receives the supplied optical energy and converts the optical energy into electric power.

The power sourcing equipment <NUM> includes a semiconductor laser <NUM> for power supply.

The optical fiber cable 200A includes an optical fiber 250A that forms a channel of feed light.

The powered device <NUM> includes a photoelectric conversion element <NUM>.

The power sourcing equipment <NUM> is connected to a power source, which electrically drives the semiconductor laser <NUM> for power supply and so on.

The semiconductor laser <NUM> for power supply oscillates with electric power supplied from the power source to output feed light <NUM>.

The optical fiber cable 200A has one end 201A connectable to the power sourcing equipment <NUM> and another end 202A connectable to the powered device <NUM>, and transmits the feed light <NUM>.

The feed light <NUM> from the power sourcing equipment <NUM> is input to the one end 201A of the optical fiber cable 200A. The feed light <NUM> propagates through the optical fiber 250A and is output from the other end 202A to the powered device <NUM>.

The photoelectric conversion element <NUM> converts the feed light <NUM> transmitted through the optical fiber cable 200A into electric power. The electric power obtained by the photoelectric conversion element <NUM> through the conversion is used as driving electric power needed in the powered device <NUM>. The powered device <NUM> is capable of outputting, for an external device, the electric power obtained by the photoelectric conversion element <NUM> through the conversion.

Semiconductor materials of semiconductor regions that exhibit a light-electricity conversion effect of the semiconductor laser <NUM> for power supply and the photoelectric conversion element <NUM> are semiconductors having a short laser wavelength of <NUM> or shorter.

Semiconductors having a short laser wavelength have a large band gap and a high photoelectric conversion efficiency. Thus, the photoelectric conversion efficiency on the power-generating side and the powered-side of optical power supply improves, and consequently the optical power supply efficiency improves.

Therefore, as such semiconductor materials, for example, semiconductor materials that are laser media having a laser wavelength (fundamental wave) of <NUM> to <NUM> such as diamond, gallium oxide, aluminum nitride, and gallium nitride may be used.

As the semiconductor materials, semiconductors having a band gap of <NUM> eV or greater are used.

For example, semiconductor materials that are laser media having a band gap of <NUM> to <NUM> eV such as diamond, gallium oxide, aluminum nitride, and gallium nitride may be used.

Laser light having a longer wavelength tends to have a higher transmission efficiency. Laser light having a shorter wavelength tends to have a higher photoelectric conversion efficiency. Thus, in the case of long-distance transmission, a semiconductor material that is a laser medium having a laser wavelength (fundamental wave) longer than <NUM> may be used. When the photoelectric conversion efficiency is prioritized, a semiconductor material that is a laser medium having a laser wavelength (fundamental wave) shorter than <NUM> may be used.

These semiconductor materials may be used in either the semiconductor laser <NUM> for power supply or the photoelectric conversion element <NUM>. The photoelectric conversion efficiency is improved on the power-sourcing side or the powered side, and consequently the optical power supply efficiency improves.

As illustrated in <FIG>, a power-over-fiber (PoF) system <NUM> according to the present embodiment is a system including an optical power supply system and an optical communication system with an optical fiber. In a strict sense, the power-over-fiber system <NUM> includes a first data communication device <NUM> including a power sourcing equipment (PSE) <NUM>, an optical fiber cable <NUM>, and a second data communication device <NUM> including a powered device (PD) <NUM>.

In the description below, as a rule, components, which are donated by the same reference signs as those of already-described components, are the same as the already-described components unless otherwise noted.

The power sourcing equipment <NUM> includes a semiconductor laser <NUM> for power supply. The first data communication device <NUM> includes, in addition to the power sourcing equipment <NUM>, a transmitter <NUM> and a receiver <NUM> that perform data communication. The first data communication device <NUM> corresponds to a data terminal equipment (DTE), a repeater, or the like. The transmitter <NUM> includes a semiconductor laser <NUM> for signals and a modulator <NUM>. The receiver <NUM> includes a photodiode <NUM> for signals.

The optical fiber cable <NUM> includes an optical fiber <NUM> including a core <NUM> and a cladding <NUM>. The core <NUM> forms a channel of signal light. The cladding <NUM> is arranged to surround the core <NUM> and forms a channel of feed light.

The powered device <NUM> includes a photoelectric conversion element <NUM>. The second data communication device <NUM> includes, in addition to the powered device <NUM>, a transmitter <NUM>, a receiver <NUM>, and a data processor <NUM>. The second data communication device <NUM> corresponds to a power end station or the like. The transmitter <NUM> includes a semiconductor laser <NUM> for signals and a modulator <NUM>. The receiver <NUM> includes a photodiode <NUM> for signals. The data processor <NUM> is a unit that processes a received signal. The second data communication device <NUM> is a node in a communication network. Alternatively, the second data communication device <NUM> may be a node that communicates with another node.

The first data communication device <NUM> is connected to a power source, which electrically drives the semiconductor laser <NUM> for power supply, the semiconductor laser <NUM> for signals, the modulator <NUM>, the photodiode <NUM> for signals, and so on. The first data communication device <NUM> is a node in the communication network. Alternatively, the first data communication device <NUM> may be a node that communicates with another node.

The photoelectric conversion element <NUM> converts the feed light <NUM> transmitted through the optical fiber cable <NUM> into electric power. The electric power obtained by the photoelectric conversion element <NUM> through the conversion is used as driving electric power for the transmitter <NUM>, the receiver <NUM>, and the data processor <NUM> and as other driving electric power needed in the second data communication device <NUM>. The second data communication device <NUM> may be capable of outputting, for an external device, the electric power obtained by the photoelectric conversion element <NUM> through the conversion.

On the other hand, the modulator <NUM> of the transmitter <NUM> modulates laser light <NUM> output from the semiconductor laser <NUM> for signals into signal light <NUM> on the basis of transmission data <NUM>, and outputs the signal light <NUM>.

The photodiode <NUM> for signals of the receiver <NUM> demodulates the signal light <NUM> transmitted through the optical fiber cable <NUM> into an electric signal, and outputs the electric signal to the data processor <NUM>. The data processor <NUM> transmits data based on the electric signal to a node. The data processor <NUM> also receives data from the node, and outputs, as transmission data <NUM>, the data to the modulator <NUM>.

The modulator <NUM> of the transmitter <NUM> modulates laser light <NUM> output from the semiconductor laser <NUM> for signals into signal light <NUM> on the basis of the transmission data <NUM>, and outputs the signal light <NUM>.

The photodiode <NUM> for signals of the receiver <NUM> demodulates the signal light <NUM> transmitted through the optical fiber cable <NUM> into an electric signal, and outputs the electric signal. Data based on the electric signal is transmitted to a node. Data from the node is treated as the transmission data <NUM>.

The feed light <NUM> and the signal light <NUM> output from the first data communication device <NUM> are input to one end <NUM> of the optical fiber cable <NUM>. The feed light <NUM> and the signal light <NUM> propagate through the cladding <NUM> and the core <NUM>, respectively, and are output from another end <NUM> of the optical fiber cable <NUM> to the second data communication device <NUM>.

The signal light <NUM> output from the second data communication device <NUM> is input to the other end <NUM> of the optical fiber cable <NUM>, propagates through the core <NUM>, and is output from the one end <NUM> of the optical fiber cable <NUM> to the first data communication device <NUM>.

As illustrated in <FIG>, the first data communication device <NUM> includes a light input/output part <NUM> and an optical connector <NUM> attached to the light input/output part <NUM>. In addition, the second data communication device <NUM> includes a light input/output part <NUM> and an optical connector <NUM> attached to the light input/output part <NUM>. An optical connector <NUM> at the one end <NUM> of the optical fiber cable <NUM> is connected to the optical connector <NUM>. An optical connector <NUM> at the other end <NUM> of the optical fiber cable <NUM> is connected to the optical connector <NUM>. The light input/output part <NUM> guides the feed light <NUM> to the cladding <NUM>, guides the signal light <NUM> to the core <NUM>, and guides the signal light <NUM> to the receiver <NUM>. The light input/output part <NUM> guides the feed light <NUM> to the powered device <NUM>, guides the signal light <NUM> to the receiver <NUM>, and guides the signal light <NUM> to the core <NUM>.

As described above, the optical fiber cable <NUM> has the one end <NUM> connectable to the first data communication device <NUM> and the other end <NUM> connectable to the second data communication device <NUM>, and transmits the feed light <NUM>. Further, in the present embodiment, the optical fiber cable <NUM> transmits the signal light <NUM> and the signal light <NUM> bidirectionally.

As semiconductor materials of semiconductor regions that exhibit a light-electricity conversion effect of the semiconductor laser <NUM> for power supply and the photoelectric conversion element <NUM>, same and/or similar materials as those mentioned in the first embodiment may be used, so that a high optical power supply efficiency is implemented.

As in an optical fiber cable 200B of a power-over-fiber system 1B illustrated in <FIG>, an optical fiber <NUM> that transmits signal light and an optical fiber <NUM> that transmits feed light may be provided separately. The optical fiber cable 200B may be constituted by a plurality of optical fiber cables.

A first configuration example that performs power supply according to a transmission distance is described next with reference to the drawing.

<FIG> illustrates a first configuration example in which the power-over-fiber system 1A described above includes a configuration that performs power supply according to a transmission distance.

This power-over-fiber system 1A additionally includes, as the configuration that performs power supply according to a transmission distance, a measurer 150A and a control device 153A. The measurer 150A measures a distance from the power sourcing equipment <NUM> to the powered device <NUM>. The control device 153A controls the power sourcing equipment <NUM> to output the feed light <NUM> after compensating for an amount of attenuation of the feed light <NUM> based on the distance from the power sourcing equipment <NUM> to the powered device <NUM> measured by the measurer 150A.

The power-over-fiber system 1A of the first configuration example described above includes a separator 151A, a photodiode 152A, and the control device 153A. The separator 151A is disposed between the power sourcing equipment <NUM> and the optical fiber cable 200A and extracts reflected light 112R of the feed light <NUM> reflected at an end (end face) of the optical fiber cable 200A adjacent to the powered device <NUM>. The photodiode 152A receives the reflected light 112R extracted by the separator 151A. The control device 153A controls the power sourcing equipment <NUM> on the basis of the detection performed by the photodiode 152A.

The separator 151A is constituted by a beam splitter, an optical coupler, or the like, and is disposed between the semiconductor laser <NUM> for power supply and the optical fiber cable 200A.

This separator 151A allows the feed light <NUM> that is to travel from the semiconductor laser <NUM> for power supply to the optical fiber cable 200A to pass therethrough. The separator 151A also transmits, to the photodiode 152A, part of the reflected light 112R that is to travel from the optical fiber cable 200A to the semiconductor laser <NUM> for power supply.

The separator 151A may be disposed in the middle of the optical fiber cable 200A, near an end of the optical fiber cable 200A adjacent to the power sourcing equipment <NUM>.

The photodiode 152A is disposed to face a direction in which the separator 151A reflects the reflected light 112R, and detects a light intensity of the reflected light 112R incident thereto. A detection signal of the photodiode 152A is input to the control device 153A.

At the time of measurement of a distance from the power sourcing equipment <NUM> to the powered device <NUM>, the control device 153A outputs the single-pulse feed light <NUM> from the semiconductor laser <NUM> for power supply and measures a time elapsed before the photodiode 152A detects the reflected light 122R of the feed light <NUM>. The control device 153A calculates the distance from the power sourcing equipment <NUM> to the powered device <NUM> on the basis of the measured elapsed time.

Specifically, the control device 153A that has the function of calculating the distance, the separator 151A, and the photodiode 152A constitute the measurer 150A.

The control device 153A includes a memory that stores a table data indicating a relationship between an attenuation rate of the feed light <NUM> and a transmission distance. With reference to the table data, the control device 153A identifies an attenuation rate corresponding to the distance from the power sourcing equipment <NUM> to the powered device <NUM> obtained through the measurement.

After obtaining the attenuation rate of the feed light <NUM>, the control device 153A controls the semiconductor laser <NUM> for power supply to output the feed light such that the feed light has an intensity equal to the sum of the original output and an amount of attenuation based on the attenuation rate. Alternatively, when the intensity of the feed light <NUM> is deficient from the intensity required by the powered device <NUM> because of attenuation related to the transmission distance, the control device 153A may control the semiconductor laser <NUM> for power supply such that the feed light <NUM> has an intensity obtained by adding the deficient amount.

After measuring the distance from the power sourcing equipment <NUM> to the powered device <NUM>, the control device 153A continuously controls the semiconductor laser <NUM> for power supply such that the feed light <NUM> has an intensity obtained by compensating for the attenuation amount.

The control device 153A described above may be constituted by a microcomputer, or by a sequencer using an analog circuit or a digital circuit.

The distance from the power sourcing equipment <NUM> to the powered device <NUM> is measured when power supply is started (including a timing immediately before the start) or when the power-over-fiber system 1A starts up (including a timing immediately before the startup).

As described before, the power-over-fiber system 1A of the first configuration example includes the measurer 150A that measures a distance from the power sourcing equipment <NUM> to the powered device <NUM>, and the control device 153A that controls the power sourcing equipment <NUM> to output the feed light <NUM> after compensating for an amount of attenuation of the feed light <NUM>. Thus, the power-over-fiber system 1A can improve the photoelectric conversion efficiency and also perform appropriate power supply by compensating for the attenuation of the feed light <NUM> caused according to the length of the optical fiber cable 200A.

The measurer 150A uses reflection of the feed light <NUM>, which is laser light, at the end face of the optical fiber cable 200A to measure the distance from the power sourcing equipment <NUM> to the powered device <NUM>.

Thus, a configuration for reflecting the feed light <NUM> need not be prepared separately. This can reduce the number of components and reduce the manufacturing cost of the device accordingly.

In the case where the measurer 150A measures the distance from the power sourcing equipment <NUM> to the powered device <NUM> when the power sourcing equipment <NUM> starts the power supply (including a timing immediately before the start), the power sourcing equipment <NUM> can perform the power supply thereafter with the feed light <NUM> having an appropriate intensity.

In the case where the measurer 150A measures the distance from the power sourcing equipment <NUM> to the powered device <NUM> when the control device 153A starts up (including a timing immediately before the startup), the frequency of measurement reduces and thus the frequency can be made appropriate.

For example, the power-over-fiber system 1A is restarted when the specifications of the system are changed because of part replacement or maintenance. In such a case, the distance can be measured again. Thus, the power supply can be performed with the feed light <NUM> having a new appropriate intensity in response to the change or the like.

A second configuration example that performs power supply according to a transmission distance is described next with reference to the drawing. <FIG> illustrates a second configuration example in which the power-over-fiber system 1A described above includes a configuration that performs power supply according to a transmission distance.

In this second configuration example, as illustrated in <FIG>, the power-over-fiber system 1A of the first configuration example additionally includes a reflecting device 361A, and a control device 363A for the reflecting device 361A. The reflecting device 361A includes a mirror 362A that reflects the feed light <NUM> between the optical fiber cable 200A and the powered device <NUM>.

In the case of this second configuration example, the distance is measured using the reflected light 112R from the mirror 362A instead of the reflected light 112R of the feed light <NUM> reflected at the end face of the optical fiber cable 200A adjacent to the powered device <NUM>. The second configuration example is the same as the first configuration example except for this point.

The reflecting device 361A includes an actuator that switches the position of the mirror 362A between a reflection position where the mirror 362A can reflect the feed light <NUM> between the optical fiber cable 200A and the powered device <NUM> and a standby position where the mirror 362A does not hinder the feed light <NUM> from being incident onto the photoelectric conversion element <NUM>.

The control device 363A is constituted by a microcomputer, a sequencer using an analog circuit or a digital circuit, or the like, and controls the above-described operation of switching the position of the mirror 362A performed by the reflecting device 361A.

As the initial position, the reflecting device 361A holds the mirror 362A at the standby position. In response to the feed light <NUM> entering the photoelectric conversion element <NUM> from the power sourcing equipment <NUM> when power supply is started or when the system starts up, a power source is supplied to the control device 363A.

In response to being supplied with the power source, the control device 363A performs control to temporarily switch the position of the mirror 362A of the reflecting device 361A to the reflection position and then return the mirror 362A to the standby position.

This allows the control device 153A to determine the distance from the power sourcing equipment <NUM> to the powered device <NUM> by measuring a time elapsed from the start of output of the feed light <NUM> to receipt of the reflected light 112R from the mirror 362A. The aforementioned elapsed time includes a delay time from when the photoelectric conversion element <NUM> receives the feed light <NUM> to when the control device 363A switches the position of the mirror from the standby position to the reflection position. Thus, this delay time is obtained in advance through measurement or the like, and is stored in the control device 153A. The control device 153A substrates the delay time from the elapsed time, and then calculates the distance.

Instead of providing the control device 363A, a connection may be made such that the control device 153A can control the reflecting device 361A through a line (such as a signal line, for example) different from that for the feed light <NUM>.

In such a case, the reflecting device 361A preferably holds the mirror 362A at the reflection position as the initial position, and the control device 153A preferably performs control to switch the position of the mirror 362A to the standby position after the reflected light 112R is detected.

This can omit the necessity of taking into account the delay time from when the photoelectric conversion element <NUM> receives the feed light <NUM> to when the control device 363A switches the position of the mirror from the standby position to the reflection position.

In this second configuration example, the same effects as those of the first configuration example are obtained. In addition, when the measurer 150A uses reflection of the feed light <NUM>, which is laser light, at the mirror 362A to measure the distance from the power sourcing equipment <NUM> to the powered device <NUM>, the measurer 150A can use the reflected light 112R having a higher light intensity. Thus, the measurer 150A can measure the distance more stably with a higher accuracy.

The reflecting device 361A described above employs the movable mirror 362A. Instead of this configuration, a reflecting device including an optical element capable switching between a light reflecting state and a light passing state in accordance with a control signal may be used.

In the first and second configuration examples, the examples of using the power-over-fiber system 1A as the base configuration have been presented. However, the power over fiber system <NUM> may be configured, as in the first configuration example, to include the measurer 150A and the control device 153A and perform control for supplementing the feed light <NUM>. Further, the power over fiber system <NUM> may be configured, as in the second configuration example, to additionally include the reflecting device 361A and the control device 363A for the reflecting device 361A and cause the feed light <NUM> to be reflected at the mirror 362A.

A third configuration example that performs power supply according to a transmission distance is described next with reference to the drawing.

<FIG> illustrates a third configuration example in which the power-over-fiber system <NUM> described above includes a configuration that performs power supply according to a transmission distance.

To perform power supply according to a transmission distance, the power-over-fiber system <NUM> of this third configuration example uses reflected light 125R of the signal light <NUM>, which is laser light, reflected at an end face of the optical fiber cable <NUM> adjacent to the second data communication device <NUM> (the powered device <NUM>), instead of the reflected light 112R of the feed light <NUM>.

In the power-over-fiber system <NUM>, the first data communication device <NUM> including the power sourcing equipment <NUM> includes the photodiode <NUM> for signals that receives the signal light <NUM> from the semiconductor laser <NUM> for signals. Thus, the power-over-fiber system <NUM> uses the photodiode <NUM> for signals as a measurer to receive the reflected light 125R of the signal light <NUM> and to measure the distance.

The power-over-fiber system <NUM> additionally includes a control device <NUM> that controls the transmitter <NUM> and the power sourcing equipment <NUM>.

At the time of measurement of a distance from the first data communication device <NUM> (the power sourcing equipment <NUM>) to the second data communication device <NUM> (the powered device <NUM>), this control device <NUM> outputs the single-pulse signal light <NUM> from the semiconductor laser <NUM> for signals of the transmitter <NUM> and measures a time elapsed before the photodiode <NUM> for signals detects the reflected light 125R of the signal light <NUM>. The control device <NUM> calculates the distance from the power sourcing equipment <NUM> to the powered device <NUM> on the basis of the measured elapsed time.

The control device <NUM> that has the function of calculating the distance, the semiconductor laser <NUM> for signals, and the photodiode <NUM> for signals constitute the measurer.

This control device <NUM> also includes a memory that stores a table data indicating a relationship between an attenuation rate of the feed light <NUM> and a transmission distance. With reference to the table data, the control device <NUM> identifies an attenuation rate corresponding to the distance from the first data communication device <NUM> (the power sourcing equipment <NUM>) to the second data communication device <NUM> (the powered device <NUM>) obtained through the measurement.

Similarly to the control device 153A described above, after obtaining the attenuation rate of the feed light <NUM>, the control device <NUM> controls the semiconductor laser <NUM> for power supply to output the feed light such that the feed light has an intensity equal to the sum of the original output and an amount of attenuation. This supplemented feed light <NUM> is continuously output after the distance is measured.

Also in the case of this third configuration example, the control device <NUM> may control the semiconductor laser <NUM> for power supply such that the feed light <NUM> has an intensity obtained by adding an amount by which the intensity is deficient from the intensity of the feed light <NUM> required by the second data communication device <NUM> (the powered device <NUM>) because of attenuation.

This control device <NUM> may also be constituted by a microcomputer, or by a sequencer using an analog circuit or a digital circuit.

The distance is measured when power supply is started (including a timing immediately before the start) or when the power-over-fiber system <NUM> starts up (including a timing immediately before the startup).

In the power-over-fiber system <NUM> of this third configuration example, the feed light <NUM> is output after an amount of attenuation of the feed light <NUM> is compensated for based on the measured distance from the first data communication device <NUM> (the power sourcing equipment <NUM>) to the second data communication device <NUM> (the powered device <NUM>). Thus, the power-over-fiber system <NUM> can improve the photoelectric conversion efficiency and can also perform appropriate power supply by compensating for attenuation of the feed light <NUM>.

Further, since the power-over-fiber system <NUM> uses the photodiode <NUM> for signals that receives the reflected light 125R of the signal light <NUM> to measure the distance, there is no need to provide the separator 151A in the channel of the feed light <NUM>. Thus, the transmission efficiency of the feed light <NUM> can be kept high.

In addition, since the photodiode <NUM> for signals, which is a fundamental component of the power-over-fiber system <NUM>, is utilized, the number of components to be newly added can be reduced. This can reduce the number of components and reduce the production cost accordingly.

A fourth configuration example that performs power supply according to a transmission distance is described next with reference to the drawing.

<FIG> illustrates a fourth configuration example in which the power-over-fiber system <NUM> described above includes a configuration that performs power supply according to a transmission distance.

The power-over-fiber system <NUM> of this fourth configuration example uses a measurer, emission of the signal light (laser light) <NUM> from the semiconductor laser <NUM> for signals, which is a laser light source, in the first data communication device <NUM> (adjacent to the power sourcing equipment <NUM>), and a response, to the emission, of the signal light (laser light) <NUM> from the semiconductor laser <NUM> for signals, which is a laser light source, in the second data communication device <NUM> (adjacent to the powered device <NUM>) to measure the distance from the first data communication device <NUM> (the power sourcing equipment <NUM>) to the second data communication device <NUM> (the powered device <NUM>).

At the time of measurement of the distance from the first data communication device <NUM> (the power sourcing equipment <NUM>) to the second data communication device <NUM> (the powered device <NUM>), this control device <NUM> controls the modulator <NUM> of the transmitter <NUM> to cause the semiconductor laser <NUM> for signals to output the signal light <NUM> for distance measurement.

In the second data communication device <NUM>, in response to the photodiode <NUM> for signals receiving the signal light <NUM> for distance measurement, the data processor <NUM> controls the modulator <NUM> to cause the semiconductor laser <NUM> for signals to output the signal light <NUM> serving as a response.

To enable the signal light <NUM> from the semiconductor laser <NUM> for signals to be identified as the signal light <NUM> for distance measurement, the modulator <NUM> desirably performs unique modulation in the first data communication device <NUM>.

Likewise, to enable the signal light <NUM> from the semiconductor laser <NUM> for signals to be identified as the signal light <NUM> serving as a response, the modulator <NUM> desirably performs unique modulation in the second data communication device <NUM>.

The control device <NUM> measures a time elapsed before the photodiode <NUM> for signals detects the signal light <NUM>. The control device <NUM> then calculates the distance from the power sourcing equipment <NUM> to the powered device <NUM> on the basis of the measured elapsed time. The aforementioned elapsed time includes a delay time from when the signal light <NUM> is received to when the signal light <NUM> is output in the second data communication device <NUM>. Thus, this delay time is obtained in advance through measurement or the like, and is stored in the control device <NUM>.

This allows the control device <NUM> to subtract the delay time from the elapsed time and to calculate the distance from the first data communication device <NUM> (the power sourcing equipment <NUM>) to the second data communication device <NUM> (the powered device <NUM>) on the basis of a transmission speed of light.

The control device <NUM> that has the function of calculating the distance, the semiconductor laser <NUM> for signals, the modulator <NUM>, the photodiode <NUM> for signals, the semiconductor laser <NUM> for signals, the modulator <NUM>, the photodiode <NUM> for signals, and the data processor <NUM> constitute the measurer.

Similarly to the control device <NUM> described above, this control device <NUM> also includes a memory that stores a table data indicating a relationship between an attenuation rate of the feed light <NUM> and a transmission distance. After obtaining the attenuation rate of the feed light <NUM>, the control device <NUM> controls the semiconductor laser <NUM> for power supply to output the feed light such that the feed light has an intensity equal to the sum of the original output and an amount of attenuation. This supplemented feed light <NUM> is continuously output after the distance is measured.

Also in this case, the control device <NUM> may control the semiconductor laser <NUM> for power supply such that the feed light <NUM> has an intensity obtained by adding an amount by which the intensity is deficient from the intensity of the feed light <NUM> required by the second data communication device <NUM> (the powered device <NUM>) because of attenuation.

The distance is measured when power supply is started (including a timing immediately before the start) or when the power-over-fiber system <NUM> starts up (including a timing immediately before the startup). However, the distance is preferably measured in a state in which at least the power source for the second data communication device <NUM> is secured by the feed light <NUM>.

In this fourth configuration example, the same effects as those of the third configuration example are obtained. In addition, since emission of the signal light <NUM> from the semiconductor laser <NUM> for signals in the first data communication device <NUM> and a response, to the emission, of the signal light <NUM> from the semiconductor laser <NUM> for signals in the second data communication device <NUM> are used to measure the distance from the first data communication device <NUM> (the power sourcing equipment <NUM>) to the second data communication device <NUM> (the powered device <NUM>), the signal light <NUM> and the signal light <NUM> that have higher light intensities can be used. This enables the distance to be measured more stably with a higher accuracy.

While the embodiments of the present disclosure have been described above, these embodiments are merely presented as examples and can be carried out in various other forms. Each component may be omitted, replaced, or modified within a range not departing from the scope of the invention as defined by the claims.

<FIG> present power-over-fiber systems <NUM> and 1A to which the configurations that perform power supply according to a transmission distance are applied. In the same manner, the configuration that performs power supply according to a transmission distance is also applicable to the power-over-fiber system 1B.

Claim 1:
A power-over-fiber system (<NUM>, 1A, 1B) comprising:
a power sourcing equipment (<NUM>) including a semiconductor laser (<NUM>) configured to oscillate with electric power to output feed light (<NUM>);
a powered device (<NUM>) including a photoelectric conversion element (<NUM>) configured to convert the feed light (<NUM>) into electric power;
an optical fiber cable (<NUM>, 200A, 200B) configured to transmit the feed light (<NUM>) from the power sourcing equipment (<NUM>) to the powered device (<NUM>);
characterized by a measurer (150A, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) configured to measure a distance from the power sourcing equipment (<NUM>) to the powered device (<NUM>); and
a control device (153A, <NUM>, <NUM>, 363A) configured to control the power sourcing equipment (<NUM>) to output the feed light (<NUM>) after compensating for an amount of attenuation of the feed light (<NUM>) according to a transmission distance on the basis of the distance from the power sourcing equipment (<NUM>) to the powered device (<NUM>) measured by the measurer (150A, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>).