JP7387112B2 - Optical power supply system and optical power supply method - Google Patents

Description

The present invention relates to an optical power supply system and an optical power supply method.

Various mechanical devices used in modern society can operate by converting electrical energy into mechanical energy such as a motor by receiving electricity from the outside.

Electricity can generally be supplied by connecting a conductor (wire) with electrical conductivity to the power device of a mechanical device. However, the electric wire must always be connected to a power source and the driving machine body, and if the machine body is free to move, this may pose a significant restriction on its movement.

Incidentally, in recent years, techniques for converting optical energy into electrical energy have been studied, and for example, Patent Document 1 listed below discloses a technique for performing high-power optical transmission using a photonic crystal.

Patent No. 6578017 Publication

However, the technology described in Patent Document 1 uses a quartz core, and has the problem that it is not suitable for laser light with a short wavelength of less than 1000 nm, which is expected to have higher output, due to the Rayleigh scattering loss of quartz. There is.

Therefore, in view of the above problems, an object of the present invention is to provide an optical power supply system and an optical power supply method that can be applied to higher output laser light.

The inventors of the present invention have conducted extensive studies regarding the above-mentioned problems, and have discovered that the above-mentioned problems can be solved by using a hollow core fiber and applying innovations thereto, leading to the completion of the present invention. .

That is, an optical power feeding system according to one aspect of the present invention that solves the above problems includes a laser device that emits a laser beam in a wavelength range of 420 nm or more and 980 nm or less, a hollow core fiber that propagates the laser beam, and a light energy source of the laser beam. and a photovoltaic element that converts energy into electrical energy.

Further, from this point of view, although not limited to this, it is preferable that the beam parameter product (BPP) of the laser light is 8 mm·mrad or less.

Further, from this point of view, although not limited to this, it is preferable that the output of the laser beam is 100 W or more.

Further, from this point of view, although not limited to this, it is preferable that the effective core cross-sectional area of the hollow core fiber is 300 μm ² or more.

Further, from this point of view, although not limited to this, it is preferable that the laser device performs multi-mode oscillation.

In addition, in this aspect, although not limited to, the laser device and the hollow core fiber are provided in the energy supply side device,
The photovoltaic element is preferably provided in an energy receiving device that is provided separately from the energy supplying device.

Further, from this point of view, it is preferable to include, although not limited to, a beam steering device that controls the optical axis of the laser beam.

Further, from this point of view, the wavelength of the laser light is preferably in the range of 420 nm or more and 540 nm or less, although it is not limited thereto.

In addition, from this point of view, although not limited to, the photovoltaic element is In _x Ga _y N _(1-xy) (x is 0 or more, and x/y is 0.2 or less). It is preferable to have a semiconductor element including.

Furthermore, from this point of view, it is preferable, although not limited thereto, to provide an optical rotary joint between the laser device and the hollow core fiber.

Further, in this aspect, although not limited to this, it is preferable that the optical rotary joint includes a quartz prism.

In addition, from this point of view, although not limited to this, the effective core cross-sectional area of the optical fiber emitted from the optical rotary joint is 1.5 times larger than the effective core cross-sectional area of the laser light beam incident on the optical rotary joint. It is preferable that it is 5 times or more.

Further, an optical power feeding method according to another aspect of the present invention includes a step of emitting laser light in a wavelength range of 420 nm or more and 980 nm or less, a step of propagating the laser light through a hollow core fiber, and a step of transmitting the laser light using a photovoltaic element. The method includes a step of converting energy into electrical energy.

As described above, according to the present invention, it is possible to provide an optical power supply system and an optical power supply method that are applicable to higher output laser light.

1 is a diagram schematically showing an optical power feeding system according to an embodiment. FIG. 2 is an image diagram of a cross section of a hollow optical fiber used in the optical power feeding system according to the embodiment. FIG. 3 is a diagram schematically showing another example of the optical power supply system according to the embodiment. FIG. 3 is a diagram schematically showing another example of the optical power supply system according to the embodiment.

Hereinafter, embodiments of the present invention will be described in detail using the drawings. However, the present invention can be implemented in many different forms and is not limited to the specific examples described in the embodiments and examples below.

(Embodiment 1)
FIG. 1 is a diagram schematically showing an optical power feeding system (hereinafter referred to as "this system") S according to the present embodiment. As shown in this figure, this system S includes a laser device 1 that emits a laser beam L, a hollow core fiber 2 that propagates the laser beam, and a photovoltaic element 3 that converts the optical energy of the laser beam L into electrical energy. It is equipped with the following. The effects of this system S will become clear from the description below, but by converting the optical energy of the laser beam L emitted by the laser device 1 into electrical energy by the photovoltaic element 3, the electrical energy can be converted into electric energy by the photovoltaic element 3. 3 can be supplied to the power unit M of the mechanical device to which it is connected.

Moreover, although this system S may be used in the atmosphere on land, it is more preferable to use it underwater. Power is normally supplied underwater using copper wires, but since copper wires are thick and heavy, the stress of tidal currents on the supply cables has a large effect, and therefore mechanical equipment requires a large power device M. However, this system When S is used, power is supplied via an optical fiber, which has the advantage that the diameter of the cable can be reduced and power consumption can be significantly reduced.

In this system S, the laser device 1 is capable of emitting laser light L, as described above, and the wavelength range thereof is 420 nm or more and 980 nm or less. When the range of the laser beam L is 420 nm or more, light propagation in water becomes possible, and when the range is 980 nm or less, the energy to be supplied can be increased.

Further, the laser device 1 of the present system S is not limited as long as it can emit the laser beam L, and a commercially available laser device can be used. The laser device may be a solid-state laser device in which the oscillation medium is solid, or a liquid laser device in which the oscillation medium is liquid, and is not limited thereto.

Further, in the present system S, the output of the laser beam L is preferably 100 W or more, although it is not limited thereto. As an example of an underwater power unit M, an ROV (Remotely Operated Unmanned Submersible Vehicle) has a constant power consumption of several tens of W even if it is small, and a constant power consumption of several hundred W if it is a medium to large size. , 100W or more, it becomes possible to apply it to the above-mentioned ROV, etc.

In addition, in the present system S, it is preferable that the laser device 1 performs multi-mode oscillation, although it is not limited thereto. Multi-mode oscillation has the advantage of increasing the efficiency of the entire system because the conversion efficiency from electric power to light is higher than that of single-mode oscillation laser devices.

In addition, in this system S, although not limited to, when the photovoltaic element 3 is separated from the power supply device and power is supplied through water, the wavelength of the laser beam L is The wavelength range is preferably from 420 nm to 540 nm, which is a wavelength range with little attenuation in water. By setting it in this range, as mentioned above, it becomes possible to supply power more efficiently underwater.

Furthermore, in the present system S, although not limited to this, the beam parameter product (BPP) of the laser beam L is preferably 8 mm·mrad or less, more preferably 5 mm·mrad or less. Setting it to 8 mm/mrad has the effect of making the laser beam L efficiently enter the hollow core fiber 2 and propagate within the fiber, increasing the coupling efficiency to the hollow core fiber 2. By setting it to 5 mm/mrad or less, This effect becomes more pronounced.

Further, as described above, the system S includes the hollow core fiber 2 through which the laser beam L propagates. Here, an "optical fiber" is an optical waveguide for propagating light, consisting of a core that propagates light and a cladding around it.By utilizing the difference in refractive index between this core and cladding, light It is possible to confine the light within the core and guide the light to the tip of the optical fiber.

Further, in this system S, a hollow core fiber 2 is used as the optical fiber. Here, the term "hollow core fiber" refers to an optical fiber in which the core of the optical fiber is a hole, and light is confined in the core and propagated by Bragg reflection. An image of this cross section is shown in FIG. In this system S, a hollow core fiber 2 is used. Since the hollow core fiber 2 propagates in a hollow gas, it can transmit the laser beam L with a lower loss than a quartz core or other materials, even at a wavelength of 980 nm or less. Suitable for light propagation and power transmission. Furthermore, when considering the transmission of the laser beam L in water, the wavelength is preferably in the range of 420 nm or more and 540 nm or less in consideration of its absorption. In particular, in the case of an optical fiber using a normal quartz core, it is thought that there is a large loss of 50 dB/km or more, but if the hollow core fiber 2 is used in this wavelength range, it is possible to reduce the loss to 1 dB/km or less.

Further, in the present system S, although not limited to this, the effective core cross-sectional area of the hollow core fiber 2 is preferably 300 μm ² or more, more preferably 600 μm ² or more. Setting it to 300 μm ² or more has the advantage of increasing the coupling efficiency between the laser and the hollow core fiber 2, while setting it to 600 μm ² or less has the advantage of increasing the coupling efficiency between the laser and the optical fiber and increasing the coupling efficiency between the laser and the hollow core fiber 2. This has the advantage of suppressing the generation of heat caused by bond loss at certain points.

In addition, the length of the hollow core fiber 2 in this system S can be adjusted as appropriate, but the longer the length, the more effective it is compared to other fibers. be. On the other hand, it is not preferable that the length is too long, so the length is preferably 5000 m or less, more preferably 2000 m or less.

Moreover, in this system S, it is preferable that the output from the hollow core fiber 2 is irradiated onto the photovoltaic element 3 through an optical system 4 such as a lens. In this case, it is also preferable to provide an optical system 4 between the laser device 1 and the hollow core fiber 2. By providing the optical system 4, light can be appropriately converged and diffused to enable efficient light transmission.

The system S also includes a photovoltaic element 3 that converts the optical energy of the laser beam L into electrical energy. Here, the term "photovoltaic element" refers to an element that converts received laser light L into electricity, and specific examples include an element made of indium gallium nitride, an element with a perovskite structure, etc. but not limited to.

Further, in the present system S, although not limited to this, it is preferable that the band gap energy of the photovoltaic element 3 is 1.65 eV or more, more preferably 2.29 eV or more. The band gap energy is inversely proportional to the wavelength, and the smaller the energy, the higher the energy.Using a photovoltaic element 3 of 1.65 eV or more has the advantage of increasing photoelectric conversion efficiency at 980 nm or less, and furthermore, 2.29 eV or more. There is an advantage, for example, that the photoelectric conversion efficiency is high at 540 nm or less.

Further, although the specific structure of the photovoltaic element 3 is not limited, for example, in order to obtain the above bandgap energy, a semiconductor whose composition contains gallium and nitrogen, preferably indium, gallium and A semiconductor containing nitrogen, specifically a semiconductor of In _x Ga _y N _(1-x-y) (x is 0 or more) is preferable, and in this case, the molar ratio of indium/gallium is is preferably 0% or more and 20% or less (x/y is 0 or more and 0.1 or less). With such a composition, it is possible to realize a photovoltaic element 3 with high photoelectric conversion efficiency at 540 nm or less.

Further, as for the area of the photovoltaic element 3, the light receiving efficiency can be increased by adopting a wide effective area, and it is preferable that the photovoltaic element 3 has a planar shape with an effective area of 100 mm x 100 mm, for example.

Further, it is preferable that this photovoltaic element 3 is connected to a battery and stores necessary power.

Moreover, in the present system S, it is preferable to include a beam steering device 5 that controls the optical axis of the laser beam L, although it can be omitted. By using the beam steering device 5, it is possible to perform optical axis control of the laser beam L, to reliably apply the laser beam L to the photovoltaic element 3, and to perform highly efficient power feeding. FIG. 3 shows an image of the system S when the beam steering device 5 is provided.

Here, the "beam steering device" is not limited as long as it has the above functions, but it is equipped with a light source 51 for adjusting the optical axis on the power transmission side and a photoelectric conversion element array 52 for position detection on the light receiving side, Preferably, positioning is performed by transmitting an optical signal of position detection information from the side to the power transmission side. Here, the optical axis adjustment light source 51 can be coupled to the same optical fiber for power feeding, but it is also possible to use an optical fiber different from the optical fiber for power feeding. The optical signal of the position detection information on the light receiving side may be transmitted through the same optical fiber as the power feeding optical fiber, or through a different optical fiber.

In addition, in this system S, the laser device 1 and the hollow core fiber 2 are provided in the energy supplying device A, and the photovoltaic element 3 is not limited to the energy supplying device A. It is preferable that the energy receiving side device B is provided separately. By doing this, it becomes possible to physically separate the energy supply side device A and the energy reception side device B, and the energy reception side device B can move freely without being restricted by electric wires etc. Become. In addition, especially when using this system S underwater, by transmitting data underwater, the energy receiving device B can move without being subjected to resistance and restrictions from the energy supplying device A, which reduces power consumption. Reduction is effective. In particular, optical fiber cables can be formed to have a smaller diameter than general power supply cables, and by separating energy supply side device A and energy reception side device B, power consumption can be further reduced. can be reduced.

Here, although the operation of this system S is clear from the above description, by using this system S, a new optical power feeding method can be provided. Specifically, the optical power feeding method according to the present embodiment (hereinafter referred to as "this method") includes (1) emitting laser light in a wavelength range of 420 nm or more and 980 nm or less; (2) emitting laser light through a hollow core fiber. (3) converting the optical energy of the laser beam into electrical energy using a photovoltaic element.

In other words, this method provides efficient energy supply by supplying laser light with a wavelength range of 420 nm or more and 980 nm or less. Specifically, as mentioned above, it can be used underwater. By using light, highly efficient optical power supply with little attenuation becomes possible even underwater. Further, in this method, by using a hollow core fiber, it is possible to reduce optical loss in the above range. Then, by converting this light energy into electrical energy using a photovoltaic element, it becomes possible to return it as electric power.

By the way, in the present system S, it is preferable that an optical rotary joint is provided between the laser device 1 and the hollow core fiber 2, although it is not limited thereto. An image diagram of this case is shown in FIG. Here, the "optical rotary joint" refers to a device that connects one or more fixed input-side optical waveguides to the same number of rotatable output-side optical waveguides via a prism. Providing the rotary joint has the effect that it is possible to continue connecting the optical fiber from the fixed laser device 1 to the optical fiber wound around the drum while feeding out the optical fiber.

Furthermore, in the present system S, although not limited to this, it is preferable that the prism constituting the optical rotary joint is made of quartz. Making the prism made of quartz has the effect of being able to withstand high-power laser light L of 100 W or more.

In addition, in this system S, the effective core cross-sectional area of the optical fiber emitted from the optical rotary joint is 1.5 times or more the effective core cross-sectional area of the beam of laser light L inputting into the optical rotary joint. is preferred. The efficiency is higher if the beam on the input side is smaller than the beam on the output side (core cross-sectional area of the fiber that receives the beam). This has the effect of suppressing fluctuations in coupling loss with the output fiber that occur when the optical rotary joint rotates and maintaining high coupling efficiency.

As described above, with the present system S, it is possible to provide an optical power feeding system and an optical power feeding method that can be applied to a higher output laser beam L. Once again, the specific effects of this system S are as follows.

Conventionally, quartz has been mainly used as the core of optical fibers to propagate high-power laser beams L of 100 W or more over long distances. Although they have been used for communications, they mainly had an oscillation wavelength of 1000 nm or more. As a known technology, attempts are being made to achieve higher power transmission by using a photonic crystal fiber to propagate through a fiber designed with an enlarged core diameter, but since the core is made of quartz, It is difficult to transmit wavelengths over long distances with low loss.

In recent years, high-output lasers with wavelengths of 980 nm or less have been developed, and there is a demand for high-power, long-distance transmission of light at these wavelengths. In the case of a quartz core, transmission loss due to Rayleigh scattering is large at wavelengths of 980 nm or less, making it unsuitable for long-distance power transmission.

On the other hand, according to this system S, it is equipped with a laser device 1, a hollow core fiber 2, and a photovoltaic element 3, and the laser device 1 has an output of 100 W or more at an oscillation wavelength of 980 nm or less. It is possible to provide an optical power supply system and an optical power supply method that solve the above problems and are applicable to higher output laser light L.

The present invention has industrial applicability as an optical power supply system and optical power supply method.

Claims (6)

an energy supply side device that integrates a hollow core fiber having a hole core and a laser device that emits laser light and propagates the laser light into the hole core of the hollow core fiber;
An optical power supply comprising: a photovoltaic element that converts the optical energy of the laser beam into electrical energy; and an energy receiving device that is provided separately from the energy supplying device and can move freely. system. The optical power feeding system according to claim 1 , further comprising a beam steering device that controls the optical axis of the laser beam. 2. The optical power feeding system according to claim 1, wherein the wavelength of the laser beam is in a range of 420 nm or more and 540 nm or less. The optical power feeding system according to claim 1 , wherein the photovoltaic element has a semiconductor element including In _x Ga _y N _(1-x-y) (x is 0 or more and x/y is 0.2 or less). . a hollow core fiber having a hole core;
An optical power supply system comprising a laser device that emits a laser beam and propagates the laser beam into the hollow core, and an optical rotary joint between the laser device and the hollow core fiber,
An optical power supply system, wherein an effective core cross-sectional area of the optical fiber on the side emitted from the optical rotary joint is 1.5 times or more as large as an effective cross-sectional area of a laser beam beam incident on the optical rotary joint. The optical power feeding system according to claim 5 , wherein the optical rotary joint includes a quartz prism.