Optical fiber and optical communication system

Abstract

To provide a higher-performance or multi-functional multicore fiber and an optical communication system.SOLUTION: An optical fiber comprises: a cladding portion; and a core portion provided inside the cladding portion, the cladding portion has a plurality of structure portions concentrically disposed around the core portion, each structure portion forms a photonic bandgap therein. In the optical fiber, wavelengths of wavelength bands of the photonic band gaps formed by the plurality of structure portions are different from each other. The core portion may be a void.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to optical fibers and optical communication systems. [Background technology]

[0002] One type of optical fiber known in the art has a periodic refractive index structure formed in the cladding, and propagates light by Bragg-reflecting it in the core using this periodic structure, thereby confining the light in the core (see Patent Document 1). This type of optical fiber is also called a photonic bandgap fiber, and the periodic structure forms a photonic bandgap in a predetermined wavelength band in the core. This wavelength band includes wavelengths that are approximately the same as the period of the periodic structure. This type of optical fiber is characterized by a core diameter that is larger than that of a typical single-mode optical fiber, for example, approximately three times larger.

[0003] In particular, this type of optical fiber, in which the core portion is an air hole, is also called a hollow-core fiber. Hollow-core fibers have the advantage of a fast propagation speed of light because the core portion is made of air. Specifically, the propagation speed of light, v, is expressed as v=c / n, where c is the speed of light in a vacuum and n is the refractive index of the propagation medium. Therefore, if the core portion is air, n is approximately 1, and if the core portion is glass, n is, for example, approximately 1.5, so hollow-core fibers can achieve a propagation speed that is approximately 1.5 times faster than optical fibers with a glass core portion.

[0004] Another advantage of hollow-core fiber is that it is less susceptible to optical fiber burnout, deterioration, fiber fuses, etc., even when transmitting high-power light. For this reason, hollow-core fiber is being considered for use in PWoF (Power over Fiber), which transmits optical energy.

[0005] Furthermore, because air has significantly better linearity than glass, there is almost no degradation (waveform distortion) of the transmitted waveform in a hollow-core fiber, even if the propagating light has high energy. Therefore, hollow-core fiber has great potential for analog signal propagation (RoF: Radio over Fiber). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-158619 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, studies have been conducted on the practical application of this type of optical fiber, and there is a demand for optical fibers with higher or more functions.

[0008] The present invention has been made in view of the above, and an object of the present invention is to provide an optical fiber and an optical communication system with higher or more functions. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems and achieve the object, one aspect of the present invention is an optical fiber comprising a cladding portion and a core portion disposed inside the cladding portion, wherein the cladding portion has a plurality of structural portions that are concentrically disposed to surround the core portion and each of which forms a photonic bandgap inside, and wherein the wavelengths of the wavelength bands of the photonic bandgaps formed by the plurality of structural portions are different from each other.

[0010] The core portion may be a hole.

[0011] The plurality of structural portions may include a first structural portion that forms a first photonic bandgap and a second structural portion that surrounds the first structural portion and forms a second photonic bandgap, and the wavelength band of the second photonic bandgap may have a shorter wavelength than the wavelength band of the first photonic bandgap.

[0012] Each of the plurality of structures may have a plurality of periodically arranged holes.

[0013] The plurality of structural portions may include a first structural portion that forms a first photonic band gap and a second structural portion that surrounds the first structural portion and forms a second photonic band gap, and the spacing between the plurality of air holes arranged in the second structural portion may be smaller than the spacing between the plurality of air holes arranged in the first structural portion.

[0014] One aspect of the present invention is an optical communication system comprising: an optical fiber; an optical transmitter having a plurality of optical transmitting units, each of which outputs light having a wavelength included in a respective wavelength band of the photonic band gap of the optical fiber to the optical fiber; and an optical receiver having a plurality of optical receiving units that receive each of the plurality of light beams transmitted through the optical fiber.

[0015] Any one of the plurality of optical receiving sections may convert the optical energy of the received light into electric power and supply it to any other one of the plurality of optical receiving sections.

[0016] The wavelength of the light received by the optical receiving unit that supplies the power may be shorter than the wavelength of the light received by the optical receiving unit to which the power is supplied. [Effects of the Invention]

[0017] According to the present invention, an optical fiber with higher functionality or multiple functions can be realized. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic cross-sectional view of an optical fiber according to a first embodiment, taken along a plane perpendicular to the longitudinal direction thereof. [Figure 2] FIG. 2 is a diagram showing the detailed structures of the first structural portion and the second structural portion. [Figure 3] FIG. 3 is a diagram illustrating an example of the power distribution of light transmitted through the optical fiber illustrated in FIG. [Figure 4] FIG. 4 is a diagram showing an example of a wavelength band of light transmitted through the optical fiber shown in FIG. [Figure 5] FIG. 5 is a schematic configuration diagram of an optical communication system according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments described below. Furthermore, in each drawing, the same or corresponding components are appropriately designated by the same reference numerals, and redundant explanations are appropriately omitted.

[0020] (Embodiment 1) Fig. 1 is a schematic cross-sectional view of an optical fiber according to embodiment 1, taken along a plane perpendicular to the longitudinal direction thereof. In Fig. 1, hatching of the cross section is omitted to make the drawing easier to see.

[0021] The optical fiber 10 includes a cladding portion 11 and a core portion 12 disposed inside the cladding portion 11. In the first embodiment, the cladding portion 11 is made of glass, and the core portion 12 is a hole formed in the glass.

[0022] The cladding portion 11 has a first structural portion 11a and a second structural portion 11b. The first structural portion 11a and the second structural portion 11b are concentrically arranged to surround the core portion 12 and are ring-shaped in cross section. More specifically, the second structural portion 11b surrounds the first structural portion 11a. The first structural portion 11a and the second structural portion 11b are an example of a plurality of structural portions.

[0023] 2A and 2B are diagrams showing the detailed structures of the first and second structural portions, with Fig. 2A showing the detailed structure of the first structural portion 11a and Fig. 2B showing the detailed structure of the second structural portion 11b.

[0024] As shown in FIG. 2(a), the first structure portion 11a is a portion in which a periodic refractive index structure is formed, and in the first embodiment, air holes 11aa are periodically arranged in a lattice pattern. The air holes 11aa are arranged to form a triangular lattice. The lattice constant of the triangular lattice, i.e., the spacing between the air holes 11aa, is Λ1. As a result, the first structure portion 11a forms a first photonic band gap in the core portion 12, having a wavelength band including substantially the same wavelength as Λ1.

[0025] As shown in FIG. 2(b), the second structure portion 11b is a portion in which a periodic refractive index structure is formed, and in the first embodiment, air holes 11ba are periodically arranged in a lattice pattern. The air holes 11ba are arranged to form a triangular lattice. The lattice constant of the triangular lattice, i.e., the spacing between the air holes 11ba, is Λ2. As a result, the second structure portion 11b forms a second photonic band gap in the core portion 12, having a wavelength band including substantially the same wavelength as Λ2.

[0026] Here, Λ1 and Λ2 are set to different values. As a result, the wavelength of the wavelength band of the first photonic bandgap formed inside the first structure portion 11a (hereinafter referred to as the first wavelength band as appropriate) and the wavelength of the wavelength band of the second photonic bandgap formed inside the second structure portion 11b (hereinafter referred to as the second wavelength band as appropriate) are different from each other. For example, in the case of FIG. 2, Λ2 is smaller than Λ1, so the wavelength of the second wavelength band is shorter than the wavelength of the first wavelength band.

[0027] According to the optical fiber 10 configured as described above, the first structure 11a allows light having a wavelength included in a first wavelength band to be confined and transmitted inside the first structure 11a (including the core 12), and the second structure 11b allows light having a wavelength included in a second wavelength band different from the first wavelength band to be confined and transmitted inside the second structure 11b (including the core 12).

[0028] FIG. 3 is a diagram illustrating an example of the power distribution of light transmitted by the optical fiber 10. In FIG. 3, the horizontal axis represents the radial position of the cladding 11, and the core 12 is located at the center of the cladding 11. FIG. 3(a) illustrates an example of the power distribution of light confined inside the first structure 11a by the first structure 11a, and FIG. 3(b) illustrates an example of the power distribution of light confined inside the second structure 11b by the second structure 11b. As shown in FIGS. 3(a) and 3(b), the light confined inside the second structure 11b by the second structure 11b has a broader power distribution than the light confined inside the first structure 11a by the first structure 11a. In this case, for example, the power density of the light confined inside the second structure 11b can be made lower than the power density of the light confined inside the first structure 11a. That is, the optical fiber 10 can transmit light of different wavelength bands with different power distributions and power density distributions.

[0029] FIG. 4 illustrates an example of a wavelength band of light transmitted by the optical fiber 10. In FIG. 4, wavelength band B1 is a wavelength band of light confined by the first structure portion 11a and is included in the first wavelength band. Wavelength band B2 is a wavelength band of light confined by the second structure portion 11b and is included in the second wavelength band. In the case of FIG. 4, the second wavelength band has a shorter wavelength than the first wavelength band. For example, wavelength band B1 is a 1.31 μm band or a 1.55 μm band, which is an example of an optical communication wavelength band, and light L1 confined by the first structure portion 11a is WDM signal light such as Dense-Wavelength Division Multiplexing (DWDM) signal light for communication. Wavelength band B2 is a 0.8 μm band or a 1.0 μm band, which is an example of a wavelength band used for optical power transmission, and light L2 confined by the second structure portion 11b is light for power transmission. In this way, the optical fiber 10 can transmit light for different purposes that is included in different wavelength bands using a single optical fiber.

[0030] The 1.31 μm and 1.55 μm bands are suitable for practical communication because various communication devices for those wavelength bands exist, such as light sources with precisely controlled wavelengths and many transceiver devices for WDM communication. The 0.8 μm and 1.0 μm bands are also suitable for practical power transmission because high-power, efficient light sources exist that output light in those wavelength bands.

[0031] As described above, the optical fiber 10 according to the first embodiment is highly functional or multifunctional.

[0032] (Embodiment 2) 5 is a schematic configuration diagram of an optical communication system according to embodiment 2. The optical communication system 100 includes the optical fiber 10 according to embodiment 1, an optical transmitter 20, and an optical receiver 30.

[0033] The optical transmitter 20 includes a signal light transmitting module 21, a power transmitting module 22, and an optical multiplexer 23. Here, the signal light transmitting module 21 and the power transmitting module 22 are examples of a plurality of optical transmitting sections.

[0034] The signal light transmission module 21 outputs WDM signal light for communication, such as light L1 shown in FIG. 4, to the optical multiplexer 23. The WDM signal light has a wavelength included in a first wavelength band of a first photonic bandgap in the optical fiber 10. The power transmission module 22 outputs power transmission light, such as light L2 shown in FIG. 4, to the optical multiplexer 23. The power transmission light has a wavelength included in a second wavelength band of a second photonic bandgap in the optical fiber 10.

[0035] The optical multiplexer 23 multiplexes the WDM signal light and the power transmission light and outputs the multiplexed light to the optical fiber 10. The configuration of the optical multiplexer 23 is not particularly limited, but it may be, for example, a spatial coupling type optical multiplexer mainly composed of optical elements such as lenses, filters, and diffraction gratings, or a fiber type optical multiplexer mainly composed of optical fibers.

[0036] The optical receiver 30 includes a signal light receiving module 31, an optical / electrical converter (O / E) 32, and an optical demultiplexer 33. Here, the signal light receiving module 31 and the optical / electrical converter 32 are an example of a plurality of optical receiving sections.

[0037] The optical demultiplexer 33 demultiplexes and outputs the WDM signal light and power transmission light transmitted through the optical fiber 10. The configuration of the optical demultiplexer 33 is not particularly limited, and may be the same as that of the optical multiplexer 23, for example.

[0038] The signal light receiving module 31 receives the WDM signal light output from the optical demultiplexer 33. The signal light receiving module 31 converts the DWDM signal light into an electrical signal. This electrical signal may be output to, for example, a higher-level device. The photoelectric converter 32 receives the power transmission light output from the optical demultiplexer 33. The photoelectric converter 32 converts the energy of the power transmission light into electrical power and supplies this electrical power to the signal light receiving module 31. The supplied electrical power is used to drive the signal light receiving module 31.

[0039] According to the optical communication system 100 configured as above, both DWDM signal light for communication and power transmission light for power feeding can be transmitted through a single optical fiber 10.

[0040] In particular, it is preferable to separate the wavelength band for communication, which includes the WDM signal light, from the wavelength band for power transmission, which includes the power supply light, into a wide wavelength band, such as a 1.55 μm band and a 0.8 μm band, which can suppress nonlinear effects that may occur in, for example, the signal light receiving module 31, the optical multiplexer 23, or the optical demultiplexer 33, and also facilitate the separation of the wavelength band for communication from the wavelength band for power transmission.

[0041] In the optical communication system 100, the power generated by the photoelectric converter 32 is supplied to the signal light receiving module 31, but it may also be supplied to other electronic devices.

[0042] Furthermore, although the core portion is an air hole in the above embodiment, the core portion may be made of glass or the same material as the cladding portion.

[0043] Furthermore, in the above embodiment, the wavelength of the second wavelength band formed by the second structure surrounding the second structure is shorter than the wavelength of the first wavelength band formed by the first structure, but the wavelength relationship of the wavelength bands is not limited to this, and for example, the wavelength of the second wavelength band may be longer than the wavelength of the first wavelength band.

[0044] In addition, in the above embodiment, the number of structural parts of the optical fiber is two, but there is no particular limitation as long as there is more than one, and it may be three or more. Correspondingly, the number of optical transmitting parts in the optical transmitter may also be three or more, and the number of optical receiving parts in the optical receiver may also be three or more.

[0045] In the above embodiment, for example, one of the two transmitted wavelength bands is light for communication and the other is light for power transmission, but both may be light for communication, or both may be light for power transmission. Even if there are more transmitted wavelength bands, the type of wavelength band can be arbitrarily determined by the design of the structure depending on the application, etc.

[0046] Furthermore, in the above embodiment, the structure portion has a periodic refractive index structure formed by holes, but the periodic refractive index structure may be formed by something other than holes as long as it can form a photonic band gap.

[0047] Furthermore, the present invention is not limited to the above-described embodiments. The present invention also includes configurations in which the above-described components are appropriately combined. Furthermore, further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspects of the present invention are not limited to the above-described embodiments, and various modifications are possible. [Explanation of symbols]

[0048] 10: Optical fiber 11: Cladding part 11a: 1st structure part 11aa, 11ba: Vacancy 11b:Second structural part 12: Core part 20: Optical transmitter 21: Signal optical transmission module 22: Power transmission module 23: Optical multiplexer 30: Optical receiver 31: Signal optical receiving module 32: Photoelectric converter 33: Optical demultiplexer 100: Optical communication system B1, B2: Wavelength bands L1, L2: light

Claims

1. A clad portion; a core portion disposed inside the cladding portion; Equipped with the cladding portion has a plurality of structural portions that are concentrically arranged to surround the core portion, each of which forms a photonic band gap therein; The wavelengths of the wavelength bands of the photonic band gaps formed by the plurality of structural portions are different from each other. Optical fiber.

2. The core portion is a hole. The optical fiber of claim 1 .

3. the plurality of structures include a first structure that forms a first photonic band gap and a second structure that surrounds the first structure and forms a second photonic band gap; The wavelength band of the second photonic band gap has a shorter wavelength than the wavelength band of the first photonic band gap. The optical fiber of claim 1 .

4. Each of the plurality of structures has a plurality of periodically arranged holes. The optical fiber of claim 1 .

5. the plurality of structures include a first structure that forms a first photonic band gap and a second structure that surrounds the first structure and forms a second photonic band gap; The intervals between the plurality of holes arranged in the second structure are smaller than the intervals between the plurality of holes arranged in the first structure. The optical fiber according to claim 4.

6. The optical fiber according to claim 1; an optical transmitter including a plurality of optical transmitting units, each of which outputs light having a wavelength included in a wavelength band of the photonic band gap of the optical fiber to the optical fiber; an optical receiver having a plurality of optical receiving units for receiving the plurality of lights transmitted through the optical fiber, respectively; Equipped with Optical communication system.

7. Any one of the plurality of optical receiving units converts the optical energy of the received light into electric power and supplies the electric power to any other one of the plurality of optical receiving units.

7. The optical communication system according to claim 6.

8. The wavelength of the light received by the optical receiving unit that supplies the power is shorter than the wavelength of the light received by the optical receiving unit to which the power is supplied.

8. The optical communication system according to claim 7.

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