Optical fibers that combine and separate light waves

Abstract

The purpose of the present disclosure is to make it possible, using a small configuration, to connect optical fibers each of which has a different number of cores.　The present disclosure is an optical fiber (91) having a core (11) that is uniform and continuous in the propagation direction, wherein said fiber is a fiber for multiplexing / demultiplexing light and is characterized by: including light guide paths (13) for optically connecting one end surface (E2) of the optical fiber (91) and lateral surfaces of the core (11); and light guide path (13) end sections, which are on the lateral surface-side of the core (11), being connected to the core (11).

Description

[Technical Field]

[0001] This disclosure relates to an optical fiber that enables the connection of optical fibers with different numbers of cores. [Background technology]

[0002] Various devices have been proposed to connect optical fibers with different numbers of cores, such as multi-core fibers and single-core fibers (see, for example, Non-Patent Document 1). Non-Patent Document 1 describes using a spatial optical system with lenses to connect each core of a multi-core fiber to individual single-core fibers.

[0003] Non-patent document 1 uses a spatial optical system, which requires the light to be extracted outside the optical fiber. Miniaturization is difficult with devices using such a spatial optical system. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] ECOC2021, We1A.4 (OPTOQUEST) [Non-Patent Document 2] OE vol.23, no.13, pp.16760-16771 [Overview of the project] [Problems that the invention aims to solve]

[0005] This disclosure aims to enable the connection of optical fibers with different core counts using a compact configuration. [Means for solving the problem]

[0006] The optical multiplexing and demultiplexing fiber according to this disclosure is an optical fiber having a core within a cladding, wherein the cladding has an optical waveguide that optically connects one end face of the optical fiber to a side surface of the core, and the end of the optical waveguide on the side surface of the core is coupled to the core.

[0007] The optical combining and splitting device according to the present disclosure comprises an optical combining and demultiplexing fiber and a multicore fiber disposed on one end face of the optical combining and demultiplexing fiber, wherein at least one of the cores of the multicore fiber is connected to the optical waveguide of the optical combining and demultiplexing fiber.

[0008] In the optical multiplexing and demultiplexing fiber according to this disclosure, the end of the optical waveguide on the side of the core may be inclined with respect to the core. In this case, the portion of the core that couples with the optical waveguide may be provided with an LPG (Long Period Fiber Grating), and light of a wavelength or mode determined by the LPG may be coupled to the optical waveguide. Here, the angle of the inclination and the structure of the optical waveguide may be determined according to the components of light to be coupled between the core and the optical waveguide and the light intensity of each component of light. Furthermore, the LPG may be controllable by pressure applied from the outer circumference of the cladding.

[0009] In the optical multiplexing and demultiplexing fiber according to this disclosure, the end of the optical waveguide on the side of the core may be a directional coupler arranged parallel to the core. In this case, the coupling length in the directional coupler and the structure of the optical waveguide may be determined according to the optical components to be coupled between the core and the optical waveguide and the optical intensity of each optical component.

[0010] Furthermore, the above disclosures can be combined as much as possible. [Effects of the Invention]

[0011] According to this disclosure, a compact configuration makes it possible to connect optical fibers with different numbers of cores. [Brief explanation of the drawing]

[0012] [Figure 1] Shows a configuration example of a wavelength-division multiplexing fiber according to the present disclosure. [Figure 2] Shows a connection example between a wavelength-division multiplexing fiber and a multi-core fiber. [Figure 3] Shows a configuration example of an optical waveguide. [Figure 4] Shows a configuration example of an optical waveguide. [Figure 5] Shows an example of a wavelength-division branching device according to the present embodiment. [Figure 6] Shows an example of a wavelength-division branching device according to the present embodiment. [Figure 7] Shows a configuration example of a wavelength-division multiplexing fiber according to the present disclosure.

Mode for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below. These examples are merely illustrative, and the present disclosure can be implemented in various modified and improved forms based on the knowledge of those skilled in the art. In this specification and the drawings, components with the same reference numerals indicate the same components.

[0014] (First Embodiment) FIG. 1 shows a configuration example of a wavelength-division multiplexing fiber according to the present disclosure. The wavelength-division multiplexing fiber 91 of the present disclosure has M (M≧1) cores 11 that are uniform and continuous in the propagation direction within the cladding 12, and has an optical waveguide 13 that optically connects the end face E2 and the side surface of the core 11. Hereinafter, in the present disclosure, the optical waveguide 13 is referred to as a tap waveguide. The tap waveguide 13 is an optical waveguide capable of propagating light between an arbitrary position in the longitudinal direction of the core 11 and the end face E2. The tap waveguide 13 is arranged so as to coincide with the position of the core of the connection destination at the output end face E2.

[0015] The figure shows an example where the coupling position of the core 11 with the tap waveguide 13 in the longitudinal direction differs for each tap waveguide 13, but the disclosure is not limited to this. For example, multiple tap waveguides 13 may be coupled at the same position in the longitudinal direction of the core 11. Also, the structure of the core 11 and cladding 12, excluding the tap waveguides 13, can be any optical fiber. For example, it may be a single core or a multicore, single-mode or multi-mode, and the material may also be arbitrary. Below, an example will be described in which the core 11 in the optical multiplexing / demultiplexing fiber 91 propagates a single mode, and the optical multiplexing / demultiplexing fiber 91 functions as an SMF.

[0016] Figure 2 shows an example of connecting an optical multiplexing / demultiplexing fiber 91 and a multicore fiber 92. The optical multiplexing / demultiplexing fiber 91 of this disclosure is an SMF except for the tap waveguide 13. Therefore, the end face E2 of the SMF is directly connected to the end face of the MCF 92, and the tap waveguide 13 is fabricated within the SMF using laser processing (see, for example, Non-Patent Document 2). Here, a femtosecond laser can be used for processing. This makes it possible to fabricate the optical multiplexing / demultiplexing fiber 91 of this disclosure and to branch from one core 11 to each of the cores 21-1, 21-2, 21-3, and 21-4 provided in the MCF 92.

[0017] The optical multiplexing and demultiplexing fiber 91 of this disclosure has the following effects. • It allows for low-loss and compact optical branching and connection from SMF to MCF92. • Space-saving and easy to handle. As will be described later, the wavelength, mode, and power can also be controlled.

[0018] The tap waveguide 13 can employ any configuration that allows light to be extracted from the core 11. For example, to extract light from the core 11, Configuration A: Combination of LPG (Long Period Fiber Grating) and tapped waveguides ·Configuration B: Directional coupler You can use it.

[0019] (Second Embodiment) Figure 3 shows a specific example of Configuration A. The core 11 is provided with an LPG 14, and a tap waveguide 13 is coupled to the portion of the core 11 where the LPG 14 is disposed. By adopting this configuration, the present disclosure can couple light of a wavelength or mode defined by the LPG 14 among the propagating light in the core 11 to the tap waveguide 13.

[0020] For example, when extracting light from the core 11 using the LPG 14 and the tap waveguide 13, the central wavelength λ of the extracted light can be controlled by the pitch (Λ LPG ) of the LPG 14. When the propagating light in the core 11 is in the LP 01 mode and the LP 11 mode, the pitch Λ LPG of the LPG 14 can be derived by the following equation using the effective refractive indices (n 01 , n 11 ) of the LP eff_01 , n eff_11 mode propagating in the core 11 and the central wavelength. (Equation 1) Λ LPG = λ center / (n eff_01 - n eff11 ) (1)

[0021] The tap waveguide 13 has an inclined portion 13T inclined with respect to the longitudinal direction of the core 11 and a waveguide portion 13D optically connecting the inclined portion 13T and the end face E2. The inclined portion 13T is coupled to the core 11. Thus, the end portion on the side surface side of the core 11 of the tap waveguide 13 is inclined at an angle θt with respect to the longitudinal direction of the core 11.

[0022] By adjusting the angle θt of the inclined section 13T and the waveguide structure, the optical components such as the coupled wavelength and coupled mode, and the coupled light intensity for each optical component, can be adjusted between the core 11 and the inclined section 13T. Here, the waveguide structure of the inclined section 13T is an arbitrary parameter that can change the optical components or coupled light intensity coupled with the core 11, and examples include the diameter, refractive index, and length of the inclined section 13T.

[0023] Thus, this disclosure allows for the extraction of wavelength, mode, and coupling amount while controlling them by using a tap waveguide 13 that is diagonally drawn on the LPG 14 and the core 11. Although the figure shows an example where the inclined portion 13T and the waveguide portion 13D are linear, this disclosure is not limited to this, and any shape can be adopted according to the optical design. In addition, the LPG 14 can be manufactured using laser processing, similar to the tap waveguide 13.

[0024] (Third embodiment) Figure 4 shows a specific example of configuration B. The tap waveguide 13 has a coupling section 13C that couples with the core 11 and a waveguide section 13D that optically connects the coupling section 13C to the end face E2. The coupling section 13C is a directional coupler positioned parallel to the core 11 at a distance that allows it to be optically coupled with the side surface of the core 11. By adopting this configuration, the present disclosure makes it possible to couple the wavelength and mode of light from the propagating light of the core 11 that the coupling section 13C couples with into the tap waveguide 13.

[0025] Bond length L of joint 13C C Furthermore, by adjusting the waveguide structure, the optical components such as the coupling wavelength and coupling mode coupled between the core 11 and the coupling portion 13C, as well as the coupled light intensity for each optical component, can be adjusted. For example, when extracting light from the core 11 using a directional coupler, the coupling length L of the coupling portion 13C can be adjusted. c By changing this parameter, the extracted wavelength and mode can be controlled. Here, the waveguide structure of the coupling portion 13C is an arbitrary parameter that can change the component of light coupled with the core 11 or the coupled light intensity, for example, diameter and refractive index.

[0026] Thus, this disclosure constructs a directional coupler by fabricating a waveguide for the coupling portion 13C adjacent to the core 11 for a certain length, and allows extraction while controlling the wavelength and coupling amount, similar to the second embodiment. Although the figure shows an example where the coupling portion 13C and the waveguide portion 13D are linear, this disclosure is not limited to this, and any shape can be adopted depending on the optical design.

[0027] (Fourth embodiment) In this embodiment, an example of the configuration of an optical combining / dividing device using the optical combining / demultiplying fiber 91 of the present disclosure will be described. Figure 5 shows an example of the wavelength combining / dividing device of this embodiment using the above-described configuration A.

[0028] In configuration A, the wavelength or mode can be selected using the LPG 14, and the light determined by the LPG 14 is coupled to the tap waveguide 13. Therefore, the optical splitting device of this embodiment has a function to control the wavelength or mode to be extracted for each tap waveguide 13 when extracting light.

[0029] For example, the wavelengths of LPG14-1, 14-2, 14-3, and 14-4 are set to wavelengths λ1, λ2, λ3, and λ4, respectively. This allows the following to occur: when light of wavelength λ1 propagates through core 11, the light of wavelength λ1 is branched to tap waveguide 13-1; when light of wavelength λ2 propagates through core 11, the light of wavelength λ2 is branched to tap waveguide 13-2; when light of wavelength λ3 propagates through core 11, the light of wavelength λ3 is branched to tap waveguide 13-3; and when light of wavelength λ4 propagates through core 11, the light of wavelength λ4 is branched to tap waveguide 13-4.

[0030] In this embodiment, tap waveguides 13-1, 13-2, 13-3, and 13-4 are connected to cores 21-1, 21-2, 21-3, and 21-4 of the multicore fiber 92, respectively. Therefore, the optical multiplexing and demultiplexing fiber 91 can output light of wavelengths λ1, λ2, λ3, and λ4 propagating through core 11 to cores 21-1, 21-2, 21-3, and 21-4, respectively.

[0031] In this embodiment, the optical multiplexing and demultiplexing fiber 91 is shown as having configuration A as described above, but this disclosure is not limited thereto, and configuration B may also be used.

[0032] (Fifth embodiment) In this embodiment, a switching structure that actively controls the connected core using the optical multiplexing and demultiplexing fiber 91 of the present disclosure will be described. Figure 6 shows an example of the optical multiplexing and branching device of this embodiment using the above-described configuration A.

[0033] Similar to the fourth embodiment, an example of connecting an N-core-MCF and an SMF will be used for explanation. The LPG14 can be actively controlled by applying pressure from the outer circumference of the cladding 12, such as a mechanical type. Therefore, in this embodiment, the LPG14 is actively controlled, and only the LPG14 located immediately before the tap waveguide 13 corresponding to the core 11 to be connected is operated.

[0034] For example, in the fourth embodiment, LPG14-1, 14-2, and 14-4 are turned OFF so they do not operate, and LPG14-3 is turned ON so it operates. This allows only wavelength λ3 of the light propagating from core 11 to be branched to core 21-3.

[0035] In the fourth embodiment, the optical multiplexing and demultiplexing fiber 91 has tapped waveguides 13 fabricated in the SMF. Therefore, the optical multiplexing and branching device of this embodiment can switch the light propagating from the SMF to any of the cores 21-1, 21-2, 21-3, and 21-4 of the MCF 92.

[0036] In the above-described optical multiplexing and demultiplexing fiber 91, an example is shown in which one core 11 is located within the cladding 12, but as shown in Figure 7, there may be two or more cores 11. Furthermore, while the above-described optical multiplexing / demultiplexing fiber 91 shows an example where four tap waveguides 13 are connected to one core 11, as shown in Figure 7, the number of tap waveguides 13 connected to one core 11 can be any number of one or more. Furthermore, although an example is shown in which the end of the tapped waveguide 13 is located on only one end face E2, as shown in Figure 7, the end faces of the tapped waveguide 13 may be located on both end faces E1 and E2.

[0037] Thus, this disclosure does not limit the number of cores in the optical multiplexing / demultiplexing fiber 91 and can be used to connect MCF92 with different core counts. Similarly, the connection from MCF92 to SMF in the reverse direction can be considered. That is, it is also possible to couple from the tap waveguide 13 to the core 11.

[0038] 11, 21-1, 21-2, 21-3, 21-4, 21-5: Core 12: Clad 13, 13-1, 13-2, 13-3, 13-4: Tapped waveguides 13T: Inclined part 13D: Waveguide 13C: Joint part 14, 14-1, 14-2, 14-3, 14-4: LPG 91: Optical multiplexing and demultiplexing fiber 92: MCF

Claims

1. An optical fiber having a first core within the cladding, A multicore fiber connected to one end face of the optical fiber, A photomultiplier / branching device comprising, The optical fiber is The cladding has a plurality of optical waveguides that optically connect one end face of the optical fiber to the side surface of the first core. The plurality of optical waveguides have their side ends relative to the first core inclined with respect to the first core. The plurality of optical waveguides have a waveguide structure in which at least one of the following conditions is met: the angle of inclination, the length of the inclined optical waveguide, the diameter of the inclined optical waveguide, and the refractive index of the inclined optical waveguide, depending on the branching mode and the coupled light intensity of the mode. The portion of the first core that is coupled to the plurality of optical waveguides is provided with a plurality of LPGs (Long Period Fiber Gratings) that extract predetermined wavelengths from the first core. The plurality of LPGs can be controlled by pressure applied from the outer circumference of the cladding. One of the plurality of LPGs, an LPG to which pressure is applied from the outer circumference of the cladding, couples light of a wavelength and mode determined by the LPG and the waveguide structure to the optical waveguide. At least one of the cores in the multicore fiber is connected to the optical waveguide in the optical fiber. A photomultiplier / branching device characterized by the following features.

2. An optical fiber having a first core within the cladding, A multicore fiber connected to one end face of the optical fiber, A photomultiplier / branching device comprising, The optical fiber is The cladding has a plurality of optical waveguides that optically connect one end face of the optical fiber to the side surface of the first core. The plurality of optical waveguides have their side ends relative to the first core inclined with respect to the first core. The plurality of optical waveguides have a waveguide structure in which at least one of the following conditions is met: the angle of inclination, the length of the inclined optical waveguide, the diameter of the inclined optical waveguide, and the refractive index of the inclined optical waveguide, depending on the branching wavelength and the coupled light intensity of the said wavelength. The portion of the first core that is coupled to the plurality of optical waveguides is provided with a plurality of LPGs (Long Period Fiber Gratings) that extract predetermined modes from the first core. The plurality of LPGs can be controlled by pressure applied from the outer circumference of the cladding. One of the plurality of LPGs, an LPG to which pressure is applied from the outer circumference of the cladding, couples light of a wavelength and mode determined by the LPG and the waveguide structure to the optical waveguide. At least one of the cores in the multicore fiber is connected to the optical waveguide in the optical fiber. A photomultiplier / branching device characterized by the following features.

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