Optical connector and method for manufacturing optical connector plug

Abstract

To provide an optical connector capable of connecting an optical fiber with low loss, and a method for manufacturing the optical connector plug.　An optical connector includes an optical connector plug (100). The optical connector plug (100) has a waveguide (20) formed using a photocurable resin (13). The waveguide (20) is connected to a core end surface of an optical fiber (10) whose one end is fixedly inserted in the optical connector plug (100), and can transmit an optical signal of a core of the optical fiber (10) to the other end. The waveguide has a tapered form in which an end surface of the other end is larger than an end surface of the one end.

Description

Optical connector and method of manufacturing optical connector plug

[0001] The present disclosure relates to an optical connector and a method for manufacturing an optical connector plug.

[0002] With the spread of the Internet, the transmission capacity of information networks is expanding year by year. Methods for expanding the transmission capacity of optical fibers include time division multiplexing, wavelength division multiplexing, and space division multiplexing. In particular, space division multiplexing is a technology that achieves large capacity by arranging multiple cores or multiple modes in a single optical fiber. With single-mode uncoupled multicore fibers, by using an interface such as fine-in-fan-out, it is possible to expand the transmission capacity using conventional transceiver devices as is.

[0003] Furthermore, one method for increasing transmission capacity is mode-division multiplexing, which increases capacity by placing multiple propagation modes in one core and transmitting different signals in each mode. This technology uses an interface such as fine-in-fan-out to use each mode in each core as a different signal transmission path, thereby increasing transmission capacity.

[0004] In order to utilize space division multiplexing transmission technology in data centers, access networks, etc., it is necessary to lay multicore fiber optical cables that serve as transmission paths for space division multiplexing transmission. In order to maintain the scalability of laying multicore fiber cables, optical connectors that can connect multicore fibers are required. In multicore fiber connector technology, the fiber cores are positioned off-center with respect to the outer diameter of the fiber, so they need to be mounted with rotational alignment to achieve low connection loss. Non-Patent Documents 1 and 2 have proposed technologies for achieving low connection loss.

[0005] Satoshi Morishima, Yuki Saito, Osamu Shimakawa, Masaru Manabe, Tetsuya Nakanishi, Tomomi Sano, Tetsuya Hayashi, "Multicore Fiber Splicing Technology," IEICE General University, BCI-1-5, 2021. Hidetaka Terasawa, Takeshi Yukikawa, Keisuke Kondo, Okihiro Sugihara, "Fabrication of Near-Infrared Self-Written Optical Waveguides and Their Application to Multichannel Optical Waveguides," IEICE General University, C-13-2, 2013.

[0006] (1) Regarding single-mode connectors with one core propagation mode Non-Patent Document 1 describes a method for suppressing rotational misalignment when fabricating a single-core or multi-core connector plug for connecting multicore fibers. However, this technology requires precise alignment, including rotational alignment, and has the problem of requiring the use of parts and rotational alignment methods with higher precision than conventional connectors.

[0007] Non-Patent Document 2 describes a technique for connecting specific combinations of multicore fibers using self-forming waveguides. However, since optical connectors are required to be connectable in any combination, cores need to be arranged in standardized design target positions, but does not describe a method for arranging cores in the design target positions.

[0008] (2) Mode multiplexing transmission with multiple core propagation modes When connecting cores with multiple propagation modes, mode conversion may occur at the optical connection point even if no optical loss occurs. In mode multiplexing transmission, different signals are transmitted in each mode, so if mode conversion occurs, the signals will interfere with each other, leading to signal degradation.

[0009] The technology in Non-Patent Document 1 discloses a splice performance of 0.07 dB on average for splicing single-mode cores. For example, if a two-mode core is used and the splice loss between the fundamental modes is 0.07 dB, and that loss is due to mode conversion from the fundamental mode to a higher-order mode, the extinction ratio (the ratio of the fundamental mode propagating light before the splice point to the light converted to the higher-order mode) is -18 dB. For example, in wavelength multiplexing transmission, wavelength multiplexing / demultiplexing devices require an extinction ratio of -30 dB or less, so an extinction ratio of -18 dB can be considered high for multiplexed transmission. As described above, the technology in Non-Patent Document 1 has issues with mode conversion.

[0010] Furthermore, the technique of Non-Patent Document 2 does not describe a method for arranging cores at the design target positions of an optical connector.

[0011] The present disclosure has been made in consideration of the above circumstances, and an object of the present disclosure is to provide an optical connector capable of connecting optical fibers with low loss, and a method for manufacturing an optical connector plug.

[0012] One aspect of the present disclosure is an optical connector including an optical connector plug, the optical connector plug having a waveguide formed using a photocurable resin, one end of the waveguide being connected to a core end face of an optical fiber inserted and fixed into the optical connector plug, and capable of transmitting an optical signal from the core of the optical fiber to the other end, the end face of the other end being tapered larger than the end face of the one end.

[0013] One aspect of the present disclosure is a method for manufacturing an optical connector plug for use in an optical connector, the optical connector plug having a ferrule capable of holding a connection end of an optical fiber and photocurable resin, the connection end of the optical fiber inserted and fixed within the ferrule, the photocurable resin filled within the ferrule so as to abut the connection end of the optical fiber, and a sealing material that forms a detachable end face of the ferrule and prevents the photocurable resin from leaking out, and by irradiating the photocurable resin with light of a wavelength that increases the refractive index and hardens the photocurable resin from the core of the optical fiber, the refractive index increases and hardens in the irradiated portion of the photocurable resin, thereby forming a tapered waveguide.

[0014] One aspect of the present disclosure is a method for manufacturing an optical connector plug for use in an optical connector, the optical connector plug having a ferrule capable of holding a connection end of an optical fiber and photocurable resin, the connection end of the optical fiber inserted and fixed into the ferrule, the photocurable resin filled in the ferrule so as to abut the connection end of the optical fiber, and a sealant that forms a detachable end face of the ferrule and prevents the photocurable resin from leaking out, the detachable end face of the ferrule being opposed to a core end face of another optical fiber inserted and fixed into another optical connector plug for fabricating a waveguide, the core of the optical fiber being irradiated with light of a wavelength that increases the refractive index of the photocurable resin and hardens the photocurable resin, and the core of the other optical fiber being irradiated with light of the same wavelength onto the photocurable resin, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin, thereby forming a tapered waveguide.

[0015] One aspect of the present disclosure is a method for manufacturing an optical connector plug for use in an optical connector, the optical connector plug having a ferrule capable of holding a connection end of an optical fiber and photocurable resin, the connection end of the optical fiber inserted and fixed within the ferrule, photocurable resin filled within the ferrule so as to abut against the connection end of the optical fiber, and a sealant that forms a detachable end face of the ferrule and prevents the photocurable resin from leaking out, wherein light of a wavelength that increases the refractive index of the photocurable resin and hardens it is irradiated from the core of the optical fiber to the photocurable resin, and light of the wavelength is irradiated from the detachable end face side to the photocurable resin via a photomask or a focusing lens, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin, thereby forming a tapered waveguide.

[0016] According to the present disclosure, it is possible to provide an optical connector capable of connecting optical fibers with low loss, and a method for manufacturing an optical connector plug.

[0017] FIG. 1 is a diagram showing the structure of an optical connector plug of an optical connector. FIG. 2 is an enlarged view of a portion of the optical connector plug shown in FIG. 1. FIG. 3 is a diagram showing a modified example of a sealing material for the optical connector plug. FIG. 4 is a diagram showing an example of an arrangement of multiple optical fibers in the optical connector plug. FIG. 5 is a diagram showing a modified example of an arrangement member for the optical connector plug. FIG. 6 is a diagram showing an example of a connection configuration of an optical connector. FIG. 7 is a diagram showing another example of a connection configuration of an optical connector. FIG. 8 is a diagram explaining a first method for manufacturing an optical connector plug. FIG. 9 is a diagram showing a modified example of the first method for manufacturing an optical connector plug. FIG. 10 is a diagram showing an example of the relationship between the axial misalignment D of an optical fiber and the excess loss TD. FIG. 11 is a diagram explaining a second method for manufacturing an optical connector plug. FIG. 12 is an enlarged view of a portion of the optical connector plug shown in FIG. 11. FIG. 13 is a diagram explaining a third method for manufacturing an optical connector plug. FIG. 14 is a diagram explaining a method for manufacturing an optical connector plug for connecting a multi-core fiber. FIG. 15 is an enlarged view of a portion of the optical connector plug shown in FIG. 14. FIG. 16 is a diagram showing an example of a connector plug structure of a single-core optical connector. Fig. 17 is a diagram showing a modified example of a sealing material for a single-core optical connector plug. Fig. 18 is a diagram showing an example of a connection configuration of a single-core optical connector. Fig. 19 is a diagram explaining a first method for manufacturing a single-core optical connector plug. Fig. 20 is a diagram explaining a second method for manufacturing a single-core optical connector plug. Fig. 21 is an enlarged view of a portion of the single-core optical connector plug shown in Fig. 20. Fig. 22 is a diagram explaining a third method for manufacturing a single-core optical connector plug. Fig. 23 is a diagram explaining a method for manufacturing a single-core optical connector plug for connecting a multicore fiber. Fig. 24 is an enlarged view of a portion of the optical connector plug shown in Fig. 23.

[0018] Next, several embodiments will be described in detail with reference to the drawings. In the description, the same components are designated by the same reference numerals and duplicated explanations will be omitted.

[0019] The first and second embodiments describe single mode embodiments, and the third and fourth embodiments describe multimode embodiments.

[0020] [First embodiment] Fig. 1 is a diagram showing an example of the structure of a connector plug of an optical connector according to a first embodiment. Fig. 1 is a cross-sectional view (side cross-sectional view) of an optical connector plug 100 taken along a plane parallel to the longitudinal direction of an optical fiber 10.

[0021] The optical connector of this embodiment includes an optical connector plug 100, which has a waveguide formed using a photocurable resin 13, one end of which is connected to a core end face of an optical fiber 10 inserted and fixed in the optical connector plug 100 and capable of transmitting an optical signal from the core of the optical fiber 10 to the other end, the end face of the other end being tapered larger than the end face of the one end. The optical connector plug 100 may also have a ferrule 11 capable of holding the connection end of the optical fiber 10 and the photocurable resin 13, and a sealant 14 which forms the detachable end face of the ferrule 11 and prevents the photocurable resin from leaking out. The photocurable resin 13 is filled in the ferrule 11 so as to abut against the connection end of the optical fiber 10.

[0022] The illustrated optical connector plug 100 includes connection ends of a plurality of optical fibers 10 inserted and fixed in a ferrule 11, the ferrule 11, an adhesive 12, a photocurable resin 13 that forms a self-forming optical waveguide (hereinafter referred to as "waveguide"), a sealing material 14, and an alignment member 16. The end face 15 of the ferrule 11 may be formed at an angle.

[0023] The optical connector plug 100 is a multi-fiber optical connector plug, and may be, for example, an F12-type multi-fiber optical fiber connector (MT connector). Alternatively, an F13-type multi-fiber optical fiber connector (MPO connector) may be used as the optical connector plug 100. In this case, the end face of the MT ferrule may be formed at an angle. The MT ferrule is housed in an MPO plug housing, and the MPO plug is connected within an MPO adapter. The multi-fiber optical connector is not limited to an MT connector or an MPO connector, as long as it can connect multiple optical fibers in a detachable manner.

[0024] Fig. 2 is an enlarged view of a portion of the cross-sectional view of the optical connector plug 100 shown in Fig. 1. As shown in the figure, the photocurable resin 13 is connected to the optical fiber 10 inside the ferrule 11. A tapered waveguide 20 capable of transmitting an optical signal is formed in the photocurable resin 13. The ferrule 11 is filled with the photocurable resin 13.

[0025] The sealing material 14 is provided on the ferrule end surface 15 and prevents the photocurable resin 13 from flowing out of the ferrule 11. The sealing material 14 holds the photocurable resin 13 inside the ferrule 11. The sealing material 14 forms the attachment / detachment end surface of the ferrule 11. The sealing material 14 is also referred to as the attachment / detachment end surface 14.

[0026] 1 and 2, the sealing material 14 may be disposed in a shape that protrudes from the ferrule end face 15. Alternatively, as shown in Fig. 3, a portion of the ferrule end face 15 may be recessed, and the sealing material 14 may be embedded in the ferrule end face 15. The sealing material 14 may have any shape and be disposed in any manner as long as it is possible to prevent the photocurable resin 13 from leaking out of the ferrule end face 15.

[0027] The sealing material 14 may be made of, for example, glass or resin. The sealing material 14 may have any shape as long as it can emit light propagating through the waveguide 20 formed in the photocurable resin 13 or propagate incident light to the waveguide 20. Furthermore, the sealing material 14 may be formed with a waveguide capable of transmitting an optical signal together with the waveguide 20.

[0028] Fig. 4 is a diagram for explaining a plurality of optical fibers 10 arranged in the optical connector plug 100. Fig. 4 is a cross-sectional view of the optical connector plug 100 cut along a plane perpendicular to the longitudinal direction of the optical fibers 10. The cross-sectional view shown is a cross-sectional view of a portion where the adhesive 12 and the alignment member 16 are present.

[0029] The optical fibers 10 are arranged at equal intervals by an aligning member 16 toward the ferrule end face 15, and are adhesively fixed to the ferrule 11 by an adhesive 12. The adhesive 12 is injected through a hole (not shown) provided in the top of the ferrule 11.

[0030] In order to arrange the optical fibers 10 at equal intervals, for example, V-grooves, semicircular grooves, circular holes, etc. are formed in the arrangement member 16. The shape formed in the arrangement member 16 may be any shape as long as it allows the optical fibers 10 to be arranged at equal intervals. In the example shown in Fig. 4, eight optical fibers 10 are arranged, but the number of optical fibers 10 is not limited to eight as long as it is two or more.

[0031] 5, the alignment member 16 may have a tapered shape to facilitate insertion of the optical fiber 10. The optical fiber 10 may be, for example, a single-core fiber, a multi-core fiber, or a polarization-maintaining fiber, as long as it is an optical fiber that transmits light of any wavelength.

[0032] 6 is a diagram showing an example of a connection configuration of the optical connector 200 of this embodiment. Here, axial alignment is performed by inserting a guide pin (not shown) into a guide hole (not shown) arranged on the ferrule end face 15, and a pressing force is applied to the opposing optical connector plugs 100 by a spring (not shown), causing the sealing materials 14 (attachment / detachment end faces) to tightly contact each other to form the optical connector 200. This allows the optical fibers 10 inserted and fixed in the opposing optical connector plugs 100 to be connected with low loss.

[0033] 7, a refractive index matching material 18 may be applied between the opposing sealing materials 14. The refractive index matching material 18 may be in a gel or solid state. When a solid refractive index matching material 18 is used, there is no need to remove and reapply the refractive index matching material 18 when connecting or disconnecting the optical connector, which reduces the amount of work required for connecting or disconnecting the optical connector.

[0034] 8 is a diagram illustrating a first method for producing the optical connector plug 100 used in the optical connector of this embodiment. In the first production method, light having a wavelength that increases the refractive index of the photocurable resin 13 and hardens the resin is irradiated onto the photocurable resin 13 from the core of the optical fiber 10, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin 13, thereby forming a tapered waveguide 20.

[0035] Specifically, a hollow portion connecting the end face of the optical fiber placed in the ferrule 11 and the ferrule end face 15 (detachable end face 14) is filled with photocurable resin 13. Then, a light source 19 with a wavelength that increases the refractive index of the photocurable resin 13 and hardens it is connected to the optical fiber 10 of the optical connector plug 100, and light of that wavelength is irradiated onto the photocurable resin 13 from the core 10a of the optical fiber. This increases the refractive index of the irradiated portion of the photocurable resin 13 and hardens it, forming a tapered waveguide 20 as shown in FIG. 2. After the waveguide 20 is formed, the light source 19 is removed, and the optical connector plug 100 is completed.

[0036] 9 , a cladding 21 may be formed around the waveguide 20. After the waveguide 20 is formed, the photocurable resin 13 may be removed from the portion where the waveguide 20 is not formed, and the ferrule 11 may be filled with another photocurable resin 13b capable of forming a cladding having a lower refractive index than the waveguide 20. Light having a wavelength that causes the other photocurable resin 13b to harden may be irradiated from the ferrule end face 15 side, thereby hardening the other photocurable resin 13b, thereby forming the cladding 21 around the waveguide 20.

[0037] Specifically, the photocurable resin 13 is removed from the injection port 22 provided in the ferrule 11, and instead photocurable resin 13b capable of forming a cladding 21 having a lower refractive index than the waveguide 20 by light irradiation is injected. Then, a light source 37 having a wavelength that causes the photocurable resin 13b to harden is prepared, and the cladding 21 may be formed by irradiating the light source 37 with light 37a having the wavelength. The injection port 22 may be provided in the ferrule 11 in advance for removing the photocurable resin 13 and injecting the photocurable resin 13b.

[0038] For example, if the optical fiber 10 is a single-mode optical fiber as defined in Recommendation G.654 of the International Telecommunications Union's Telecommunications Standardization Sector (ITU-T), the mode field diameter, which corresponds to the core diameter of the single-mode fiber, can be in the range of 9.5 μm to 15 μm. Therefore, the mode field diameter of the core 10 a of the optical fiber 10 can be selected in the range of 9.5 μm to 15 μm. When axial misalignment occurs in an optical connector connection, the larger the mode field diameter, the lower the excess loss caused by the axial misalignment.

[0039] 10 shows an example of the relationship between the amount of axial misalignment D of the optical fiber and the excess loss TD. The relationship between the amount of axial misalignment D of the optical fiber and the excess loss TD can be expressed by the following equation.

[0040]

[0041] W1 and W2 are the mode field diameters of the cores (waveguides 20) of the opposing ferrule end faces 15 of the two optical connector plugs 100 that make up the optical connector 200. Fig. 10 shows the loss when the mode field diameters of the two cores are both 9.5 µm and the loss when the mode field diameters of the two cores are both 15 µm.

[0042] For example, when the axial misalignment D is 2.0 μm, the mode field diameter of the core at the ferrule end face 15 in the tapered waveguide 20 is expanded to 15 μm. This reduces the excess loss TD from approximately 0.77 dB when the mode field diameter is 9.5 μm to approximately 0.31 dB. Note that the optical fiber 10 is not limited to the specified single-mode optical fiber as long as it is capable of transmitting light at the desired wavelength.

[0043] 11 is a diagram illustrating a second manufacturing method for the optical connector plug 100 used in the optical connector 200 of this embodiment. In the second manufacturing method, the core end face of another optical fiber 30 inserted and fixed in another optical connector plug 300 for manufacturing a waveguide is placed opposite the detachable end face 14 of the ferrule 11, and light of a wavelength that increases the refractive index of the photocurable resin 13 and hardens the photocurable resin 13 is irradiated from the core of the optical fiber 10 onto the photocurable resin 13, while light of the same wavelength is irradiated from the core of the other optical fiber 30 onto the photocurable resin 13, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin 13, thereby forming a tapered waveguide 20.

[0044] Specifically, another optical connector plug 300 for fabricating a waveguide (a connector plug for fabricating a waveguide) is connected to the optical connector plug 100 of the optical connector 200. The other optical connector plug 300 includes a plurality of optical fibers 30, a ferrule 31, an adhesive 32, and an alignment member 36.

[0045] The core 30a of the optical fiber 30 inserted and fixed into the other optical connector plug 300 has the same cutoff wavelength characteristics as the core 10a of the optical fiber 10 of the optical connector plug 100, and has a larger diameter than the core 10a. Light sources 19, 39 with a wavelength that increases the refractive index of the photocurable resin 13 and hardens it are connected to the optical fiber 10 of the optical connector plug 100 and the optical fiber 30 of the other optical connector plug 300, respectively. Light of the wavelength is then irradiated from the cores 10a, 30a of the optical fibers 10, 30. This increases the refractive index of the irradiated portion of the photocurable resin 13 and hardens it, creating a tapered waveguide 20 as shown in FIG. 12 . After the waveguide 20 is created, the other optical connector plug 300 and the light source 19 are removed, completing the optical connector plug 100. The optical fiber 30 has a core 30a and a cladding 30b.

[0046] The optical connector plug 300 may be an optical connector plug used in a high-precision optical connector manufactured with minimal error from the design target of the optical connector. For example, a standard connector specified by the IEC (International Electrotechnical Commission) may be used.

[0047] In the case of a multicore fiber connector without a reference connector, an optical connector with low connection loss may be selected, for example, using the following procedure. A plurality of optical connectors are fabricated in which the core positions are aligned so that there is little error from the design target by image alignment or the like, and those with small errors are selected from among them to extract sample group A. Another plurality of optical connectors are fabricated in which the core positions are aligned, and those with small errors are selected from among them to extract sample group B, which is different from sample group A. A plurality of optical connectors are fabricated in which the core positions are aligned, and those with small errors are selected from among them to extract sample group C, which is different from sample groups A and B. The optical connectors of sample groups A, B, and C are then connected together to select an optical connector that achieves even lower connection loss. The optical connector plugs of the optical connectors selected in this manner may be used as other optical connector plugs 300.

[0048] 13 is a diagram illustrating a third method for producing the optical connector plug 100 according to the first embodiment. In the third method, the photocurable resin 13 is irradiated with light of a wavelength that increases the refractive index of the photocurable resin 13 and hardens the resin, from the core of the optical fiber 10, and the photocurable resin 13 is irradiated with light of the wavelength from the attachment / detachment end face 14 side through a photomask 42, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin 13, thereby forming a tapered waveguide 20.

[0049] Specifically, in the third manufacturing method, instead of using another optical connector plug 300, photolithography using a photomask 42 and a light source 38 is used. The photomask 42 and the light source 38 with a wavelength that increases the refractive index of the photocurable resin 13 and hardens it are disposed near the ferrule end face 15 of the optical connector plug 100. In addition, a light source 19 with a wavelength that increases the refractive index of the photocurable resin 13 and hardens it is connected to the optical fiber 10 of the optical connector plug 100.

[0050] By irradiating light of a wavelength that increases the refractive index of the photocurable resin 13 and hardens it from the core 10a of the optical fiber 10 and the photomask 42, respectively, the refractive index of the irradiated portion of the photocurable resin 13 increases and hardens, thereby generating a waveguide 20.

[0051] The mode field diameter of the light irradiated from the light source 38 can be adjusted by changing the shape of the photomask 42. By irradiating the photocurable resin 13 with light that has a mode field diameter larger than that of the core 10a of the optical fiber 10 using the photomask 42, it is possible to create a tapered waveguide 20. After the waveguide 20 is created, the photomask 42 and the light sources 19 and 38 are removed, and the optical connector plug 100 is produced.

[0052] In the first manufacturing method described above, the optical connector plug 100 is irradiated with light of a wavelength that increases the refractive index of the photocurable resin 13 and hardens it, in the second manufacturing method another connector plug 300 for manufacturing a waveguide is used, and in the third manufacturing method photolithography is used to irradiate the photocurable resin 13 with light of the wavelength. Note that the manufacturing method of the optical connector plug 100 is not limited to these, and any method that can manufacture a tapered waveguide 20 may be used.

[0053] 14 is a diagram illustrating a method for fabricating an optical connector plug 100 for connecting a multicore fiber. Here, a method for fabricating the optical connector plug 100 using the second fabrication method described above will be described as an example. Another optical connector plug 300 is connected to the optical connector plug 100. The core 30a of the optical fiber 30 of the other optical connector plug 300 has the same cutoff wavelength characteristics as the core 10a of the optical fiber 10 of the optical connector plug 100, and has a larger diameter than the core 10a. The optical fiber 10 of the optical connector plug 100 and the optical fiber 30 of the other optical connector plug 300 are each connected to a single-core fiber 40 via a fan-out 41. Light sources 19, 39 with a wavelength that increases the refractive index and hardens the photocurable resin 13 are connected to each single-core fiber 40, and light of the wavelength is irradiated from the cores 10a, 30a of the optical fibers 10, 30.

[0054] This causes an increase in the refractive index and hardening of the photocurable resin 13 in the irradiated portion, forming a plurality of tapered waveguides 20 as shown in Fig. 15. After the waveguides 20 are formed, the other optical connector plugs 300 and the fan-out 41 are removed to produce the optical connector plug 100. Although Fig. 14 and Fig. 15 show an example of a multicore fiber having four cores, the number of cores in the multicore fiber may be two or more, and the core arrangement may be any arrangement.

[0055] [Second embodiment] Fig. 16 is a diagram showing an example of a connector plug structure of an optical connector according to a second embodiment. Fig. 16 is a cross-sectional view (side cross-sectional view) of an optical connector plug 500 cut along a plane parallel to the longitudinal direction of an optical fiber 50.

[0056] The optical connector plug 500 of this embodiment has a waveguide formed using a photocurable resin 53, one end of which is connected to a core end face of an optical fiber 50 inserted and fixed in the optical connector plug 500 and capable of transmitting an optical signal from the core of the optical fiber 50 to the other end, the end face of the other end being tapered larger than the end face of the one end. The optical connector plug 500 may also have a ferrule 51 capable of holding the connection end of the optical fiber 50 and the photocurable resin 53, and a sealant 54 which forms the detachable end face of the ferrule 51 and prevents the photocurable resin from leaking out. The photocurable resin 53 is filled in the ferrule 51 so as to abut against the connection end of the optical fiber 50.

[0057] The optical connector plug 500 of this embodiment is a single-core optical connector plug, and includes a connection end of a single optical fiber 50 inserted and fixed in a ferrule 51, the ferrule 51, a plug frame 52, a photocurable resin 53 that forms a self-forming optical waveguide (waveguide), a sealant 54, a tab 56, a flange 57, a spring 58, and a stop ring 59. The sealant 54 is disposed on a ferrule end face 55 so as to prevent the photocurable resin 53 filled in the ferrule 51 from leaking out.

[0058] An F04 type optical fiber connector (SC connector) may be used as the single-core optical connector plug 500. Also, an F14 type optical fiber connector (MU connector) may be used as the optical connector plug 500 instead of the SC connector.

[0059] The optical connector plug 500 may have any shape as long as the single-core optical fiber 50 adhesively fixed to the ferrule 51 can be connected to an opposing optical fiber via an adapter (not shown). That is, the presence or absence of the flange 57, spring 58, stop ring 59, plug frame 52, and knob 56, as well as their shapes, are not limited to those shown in Figure 16. The single-core optical connector of this embodiment is not limited to an SC connector or an MU connector as long as it can connect a single-core optical fiber in a detachable manner.

[0060] The photocurable resin 53 is connected to the optical fiber 50 inside the ferrule 51 and serves to form a tapered self-forming optical waveguide capable of transmitting an optical signal. The photocurable resin 53 is prevented from flowing out of the ferrule end face 55 by the sealing material 54, and is held inside the ferrule 51.

[0061] The sealing material 54 may be disposed so as to protrude from the ferrule end face 55 as shown in FIG. 16 , or may be disposed so as to be embedded in the ferrule end face 55 by forming a recess in the ferrule end face 55 as shown in FIG. 17 . The sealing material 54 may have any shape and be disposed in any position as long as it can prevent the photocurable resin 53 from leaking out of the ferrule end face 55. The sealing material 54 is also referred to as a detachable end face 54. For example, glass or resin may be used for the sealing material 54. The sealing material 54 may have any shape as long as it can emit light propagating through a waveguide formed in the photocurable resin 53 or propagate incident light into the waveguide. A waveguide capable of transmitting an optical signal may be formed in the sealing material 54 and in conjunction with the waveguide formed in the photocurable resin 53.

[0062] The single-core optical fiber 50 may be, for example, a single-core fiber, a multi-core fiber, a polarization-maintaining fiber, or the like, as long as it is an optical fiber that transmits light of an arbitrary wavelength.

[0063] 18 is a diagram showing an example of a connection configuration of an optical connector according to the second embodiment. Axial alignment is performed by inserting two opposing ferrules 51 into a sleeve 63 attached to an adapter (not shown). Then, a pressing force is applied to the optical fiber 50 and the ferrule end face 55 by a spring 58, forming an optical connector 600 in a configuration in which the sealing materials 54 are in close contact with each other, and the optical fiber 50 is connected.

[0064] To reduce return loss, a refractive index matching material (not shown) may be applied between the sealing materials 54. The refractive index matching material may be in a gel or solid state. When a solid refractive index matching material is used, there is no need to remove and reapply the matching material when connecting or disconnecting the optical connector, which reduces the amount of work required for connecting or disconnecting the optical connector.

[0065] 19 is a diagram illustrating a first manufacturing method of the optical connector plug 500 of the second embodiment. In the first manufacturing method, light having a wavelength that increases the refractive index of the photocurable resin 53 and hardens the resin is irradiated onto the photocurable resin 53 from the core of the optical fiber 50, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin 53, thereby forming a tapered waveguide.

[0066] Specifically, a light source 69 with a wavelength that increases the refractive index of the photocurable resin 53 and hardens it is connected to the optical fiber 50 of the optical connector plug 500, and light of that wavelength is irradiated onto the photocurable resin 53 from the core 50a of the optical fiber 50. This increases the refractive index of the irradiated portion of the photocurable resin 53 and hardens it, creating a tapered waveguide. After the tapered waveguide is created, the light source 69 is removed, and the optical connector plug 500 is completed.

[0067] After the waveguide is formed, a cladding may be formed in the same manner as in the first manufacturing method of the first embodiment. Specifically, after the waveguide is formed, the photocurable resin 53 is removed from an injection port (not shown) formed in the ferrule 51, and instead a photocurable resin capable of forming a cladding having a lower refractive index than the waveguide by light irradiation is injected. A light source with a wavelength that causes the photocurable resin for the cladding to harden may be prepared, and the cladding may be formed by irradiating light from the light source.

[0068] For example, if the optical fiber 50 is a single-mode optical fiber as defined in Recommendation G.654 of the International Telecommunications Union's Telecommunications Standardization Sector (ITU-T), the mode field diameter (corresponding to the core diameter of the single-mode fiber) can be in the range of 9.5 μm to 15 μm, and the mode field diameter with respect to the core 50a can be selected in the range of 9.5 μm to 15 μm. When axial misalignment occurs in an optical connector connection, the larger the mode field diameter, the lower the excess loss due to the axial misalignment. For example, when the axial misalignment amount D is 2.0 μm, the mode field diameter of the core (waveguide 60) at the ferrule end face 55 in a tapered waveguide is expanded to 15 μm. This reduces the excess loss TD from approximately 0.77 dB when the mode field diameter is 9.5 μm to approximately 0.31 dB. The optical fiber 10 is not limited to the defined single-mode optical fiber, as long as it can transmit light at the desired wavelength.

[0069] 20 is a diagram illustrating a second method for producing the optical connector plug 500 of the second embodiment. In the second production method, the core end face of another optical fiber 70 inserted and fixed in another optical connector plug 700 for producing a waveguide is arranged to face the detachable end face 54 of the ferrule 51, and light of a wavelength that increases the refractive index of the photocurable resin 53 and causes curing is irradiated from the core of the optical fiber 50 onto the photocurable resin 53, while light of the same wavelength is irradiated from the core of the other optical fiber 70 onto the photocurable resin 53, thereby increasing the refractive index and curing the irradiated portion of the photocurable resin 53, thereby forming a tapered waveguide 60.

[0070] Specifically, another optical connector plug 700 for creating a waveguide is connected to the optical connector plug 500. The core 70a of the optical fiber 70 of the other optical connector plug 700 has the same cutoff wavelength characteristics as the core 50a of the optical fiber 50 of the optical connector plug 500 and has a larger diameter than the core 50a. Light sources 69 and 89 with a wavelength that increases the refractive index of the photocurable resin 53 and hardens it are connected to the optical fiber 50 of the optical connector plug 500 and the optical fiber 70 of the other optical connector plug 700, respectively, and light of the wavelength is irradiated onto the photocurable resin 53 from the cores 50a and 70a of the optical fibers 50 and 70. This increases the refractive index of the irradiated portion of the photocurable resin 53 and hardens it, forming a tapered waveguide 60 as shown in FIG. 21 . After the waveguide 60 is created, the other optical connector plug 700 and the light source 69 are removed, thereby completing the optical connector plug 500.

[0071] The optical connector plug 700 may be a high-precision connector manufactured with minimal error from the design target of the optical connector. For example, a standard connector specified by the IEC (International Electrotechnical Commission) may be used.

[0072] In the case of a multicore fiber connector without a reference connector, an optical connector with low connection loss may be selected, for example, using the following procedure. A plurality of optical connectors are fabricated in which the core positions are aligned so that there is little error from the design target by image alignment or the like, and those with small errors are selected from among them to extract sample group A. Another plurality of optical connectors are fabricated in which the core positions are aligned, and those with small errors are selected from among them to extract sample group B, which is different from sample group A. A plurality of optical connectors are fabricated in which the core positions are aligned, and those with small errors are selected from among them to extract sample group C, which is different from sample groups A and B. The optical connectors of sample groups A, B, and C are then connected together to select an optical connector that achieves even lower connection loss. The optical connector plugs of the optical connectors selected in this manner may be used as other optical connector plugs 300.

[0073] 22 is a diagram illustrating a third method for producing the optical connector plug 500 of the second embodiment. In the third method, the photocurable resin 53 is irradiated with light of a wavelength that increases the refractive index of the photocurable resin 53 and hardens the resin, from the core of the optical fiber 50, and the photocurable resin 53 is irradiated with light of the wavelength from the attachment / detachment end face 54 side through a photomask 62, thereby increasing the refractive index of the irradiated portion of the photocurable resin 53 and hardening the resin, thereby forming a tapered waveguide 60.

[0074] Specifically, instead of using another optical connector plug 700, photolithography technology is used using a photomask 62 and a light source 88. The photomask 62 and a light source 88 with a wavelength that increases the refractive index of the photocurable resin 53 and hardens it are disposed near the ferrule end face 55 of the optical connector plug 500. In addition, a light source 69 with a wavelength that increases the refractive index of the photocurable resin 53 and hardens it is connected to the optical fiber 50 of the optical connector plug 500.

[0075] By irradiating light of a wavelength that increases the refractive index of the photocurable resin 53 and hardens it from the core 50a of the optical fiber 50 and the photomask 62, respectively, the refractive index of the irradiated portion of the photocurable resin 53 increases and hardens, thereby generating a tapered waveguide 60.

[0076] The mode field diameter of light 88a emitted from light source 88 can be adjusted by changing the shape of photomask 62. By irradiating light curable resin 53 with light that has a mode field diameter larger than that of core 50a of optical fiber 50 using photomask 62, it is possible to create tapered waveguide 60. After creating waveguide 60, photomask 62 and light sources 69 and 88 are removed, and optical connector plug 500 is produced.

[0077] In the first manufacturing method described above, optical connector plug 500 is irradiated with light of a wavelength that increases the refractive index of photocurable resin 53 and hardens it, in the second manufacturing method another connector plug 700 for manufacturing a waveguide is used, and in the third manufacturing method photolithography is used to irradiate light of the wavelength to photocurable resin 53. Note that the manufacturing method of optical connector plug 500 is not limited to these, and any method that can manufacture tapered waveguide 60 may be used.

[0078] 23 is a diagram illustrating a method for fabricating an optical connector plug 500 for connecting a multicore fiber. Here, a method for fabricating the optical connector plug 500 using the second fabrication method described above will be described as an example. Another optical connector plug 700 is connected to the optical connector plug 500. The core 70a of the optical fiber 70 of the other optical connector plug 700 has the same cutoff wavelength characteristics as the core 50a of the optical fiber 50 of the optical connector plug 500, and has a diameter larger than the diameter of the core 50a.

[0079] The optical fiber 50 of the optical connector plug 500 and the optical fiber 70 of another optical connector plug 700 are each connected to a single-core fiber 80 via a fan-out 61. Light sources 69, 89 with a wavelength that increases the refractive index of the photocurable resin 53 and hardens it are connected to each single-core fiber 80, and light of the wavelength is irradiated onto the photocurable resin 53 from the cores 50 a, 70 a of the optical fibers 50, 70.

[0080] This causes an increase in the refractive index and hardening of the photocurable resin 13 in the irradiated portion, resulting in the generation of a plurality of tapered waveguides 60 as shown in Fig. 24. After the waveguides 60 are generated, the other optical connector plugs 700 and the fan-out 61 are removed to produce the optical connector plug 500. Although Fig. 23 and Fig. 24 show an example of a multicore fiber having four cores, the number of cores in the multicore fiber may be two or more, and the core arrangement may be any arrangement.

[0081] [Third Embodiment] Figure 16 is a diagram showing an example of a connector plug structure of an optical connector according to a third embodiment. The connector plug structure 9 of this embodiment is similar to the connector plug structure of the second embodiment described above. That is, an optical connector plug 500 of this embodiment has a waveguide formed using a photocurable resin 53, one end of which is connected to a core end face of an optical fiber 50 inserted and fixed into the optical connector plug 500, and which is capable of transmitting an optical signal from the core of the optical fiber 50 to the other end, and the end face of the other end is tapered and larger than the end face of the one end. The optical connector plug 500 may also include a ferrule 51 capable of holding the connection end of the optical fiber 50 and the photocurable resin 53, and a sealant 54 that forms the detachable end face of the ferrule 51 and prevents the photocurable resin from leaking out. The photocurable resin 53 is filled in the ferrule 51 so as to abut against the connection end of the optical fiber 50.

[0082] The illustrated optical connector plug 500 is a single-core optical connector plug and includes a connection end of a single optical fiber 50 inserted and fixed in a ferrule 51, the ferrule 51, a plug frame 52, a photocurable resin 53 that forms a self-forming optical waveguide (waveguide), a sealant 54, a tab 56 (housing), a flange 57, a spring 58, and a stop ring 59. The sealant 54 is disposed on a ferrule end face 55 to prevent the photocurable resin 53 filled in the ferrule 51 from leaking out. The sealant 54 is also referred to as a detachable end face 54. The single-core optical connector plug 500 can be, for example, an SC connector, an MU connector, or other optical connector plug, but is not limited to these.

[0083] The optical connector plug 500 may have any shape as long as the single-core optical fiber 50 adhesively fixed to the ferrule 51 can be connected to an opposing optical fiber via an adapter (not shown). That is, the presence or absence of the flange 57, spring 58, stop ring 59, plug frame 52, and knob 56, as well as their shapes, are not limited to those shown in Figure 16. The single-core optical connector of this embodiment is not limited to an SC connector or an MU connector as long as it can connect a single-core optical fiber in a detachable manner.

[0084] The photocurable resin 53 is connected to the optical fiber 50 inside the ferrule 51 and serves to form a tapered self-forming optical waveguide capable of transmitting an optical signal. The photocurable resin 53 is prevented from flowing out of the ferrule end face 55 by the sealing material 54, and is held inside the ferrule 51.

[0085] One end of the tapered waveguide is connected to the core end face of the optical fiber 50, and the other end is connected to the sealing material 54, which is the detachable end face. The cross-sectional size of the tapered waveguide at the connection position with the sealing material 54 is larger than the cross-sectional size at the connection position with the core end face of the optical fiber. The sealing material 54 may be arranged so as to protrude from the ferrule end face 55 as shown in FIG. 16 , or may be arranged so as to be embedded in the ferrule end face 55 with the ferrule end face 55 having a concave shape as shown in FIG. 17 . The sealing material 54 may have any shape and arrangement as long as it can prevent the photocurable resin 53 from leaking out from the ferrule end face 55. For example, glass, resin, or the like can be used for the sealing material 54. The sealing material 54 may have any shape as long as it can emit light propagating through the waveguide formed in the photocurable resin 53 or propagate incident light into the waveguide. A waveguide capable of transmitting an optical signal together with the waveguide formed in the photocurable resin 53 may be formed in the sealing material 54 .

[0086] The single-core optical fiber 50 of this embodiment may be, for example, a single-core multimode fiber or a multi-core multimode fiber, as long as it is an optical fiber that transmits light of any wavelength in multiple propagation modes. In this embodiment, a case where a multi-core multimode fiber is used will be described.

[0087] A first method for producing the optical connector plug of this embodiment will be described with reference to Fig. 19. In the first method, light having a wavelength that increases the refractive index of the photocurable resin 53 and hardens the resin is irradiated onto the photocurable resin 53 from the core of the optical fiber 50, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin 53, thereby forming a tapered waveguide.

[0088] Specifically, a light source 69 with a wavelength that increases the refractive index of the photocurable resin 53 and hardens it is connected to the optical fiber 50 of the optical connector plug 500 according to this embodiment, and light with that wavelength is irradiated onto the photocurable resin 53 from the core 50a of the optical fiber 50. This causes the irradiated light to spread in a tapered shape within the photocurable resin 53, increasing the refractive index and hardening the irradiated portion of the photocurable resin 53, thereby forming a tapered waveguide. After the tapered waveguide is formed, the light source 69 is removed, and the optical connector plug 500 is completed.

[0089] The light source 69 has the same wavelength as the communication light to be transmitted through the optical connector, and the light is propagated in the same propagation mode as the propagation mode used for communication to generate a tapered waveguide. As a method for this, for example, when connecting a multimode fiber using three propagation modes, LP01 mode, LP11 mode, and LP02 mode, there is a method in which the light output from the light source 69 is first propagated in the optical fiber 50 in the LP01 mode to harden the photocurable resin 53, then propagated in the LP11 mode to harden the photocurable resin 53, and then propagated in the LP02 mode to harden the photocurable resin 53.

[0090] After the waveguide is created, the photocurable resin 53 is removed, and a photocurable resin capable of forming a cladding having a lower refractive index than the waveguide by light irradiation is injected, and a light source with a wavelength that causes the injected photocurable resin to harden is prepared, and the cladding can be formed by irradiating the injected photocurable resin with light of a wavelength that causes the injected photocurable resin to harden.

[0091] Alternatively, a photocurable resin 53 having the characteristic of being cured at two or more different wavelengths may be used to form a waveguide, and then a light source of a wavelength different from that used when the waveguide was formed may be used to cure the remaining uncured photocurable resin 53, thereby forming a cladding with a low refractive index.

[0092] The refractive index of the cladding changes depending on whether or not the cladding is cured, and if it is cured, the physical properties of the photocurable resin injected and the wavelength used for curing. A change in the refractive index of the cladding changes the mode field diameter of the light propagating through the formed waveguide. Taking advantage of this, after forming the waveguide, the loss and mode conversion state can be measured, and if necessary, the refractive index of the cladding can be changed to change the mode field diameter of the waveguide and improve the loss and mode conversion state.

[0093] The formed waveguide has an extremely fine structure and may be broken if an external force is applied. However, since the waveguide of this embodiment is formed within the ferrule 51 and the sealing material 54, it is protected from external forces by the ferrule 51. The ferrule 51 is protected from external forces by the plug frame 52. The plug frame 52 is protected from external forces by the tab 56. In this way, this embodiment can provide an optical connector in which the waveguide is less likely to be broken.

[0094] 18 is a diagram showing an example of a connection configuration of an optical connector according to the third embodiment. Axial alignment is performed by inserting two opposing ferrules 51 into a sleeve 63 attached to an adapter (not shown). Then, a pressing force is applied to the optical fiber 50 and the ferrule end face 55 by a spring 58, forming an optical connector 600 in a form in which the detachable end faces 54 are in close contact with each other, and the optical fiber 50 is connected. A refractive index matching material may be applied between the detachable end faces 54 to reduce return loss.

[0095] When using the sleeve 63 and ferrule 51, if components conforming to the international standard IEC 61755-3-1 are used, the maximum misalignment of the optical fiber core axes is 2.0 μm.

[0096] For example, suppose the mode field diameter of a particular propagation mode in the optical fiber 50 is 10 μm. Suppose this mode field diameter expands to, for example, 20 μm at the detachable end face 54 due to the tapered waveguide. When axial misalignment occurs in an optical connector connection, the larger the mode field diameter, the more the loss and mode conversion caused by the axial misalignment decrease. The relationship between the amount of axial misalignment D of the optical fiber and the proportion T of propagating light that transmits without loss or mode conversion can be expressed by the following equation:

[0097]

[0098] W1 and W2 are the mode field radii of the propagating light at the detachable end faces 54 of the two optical connector plugs 500 of the optical connector 600. When the optical fiber core axis misalignment during connector connection is 2.0 μm, the above formula shows that the proportion of light that transmits without loss or mode conversion is 85.2% when the mode field diameter is 10 μm, and 96.1% when the mode field diameter is 20 μm. Therefore, by enlarging the mode field diameter using a tapered waveguide, loss and mode conversion can be significantly reduced.

[0099] For example, in a typical single-mode fiber for communication, the angle of light emitted from the end of the optical fiber is approximately 10 degrees, and a tapered waveguide of only 30 μm is sufficient to widen the mode field diameter to 20 μm. Because the tapered waveguide is short, almost no optical loss occurs during propagation through the tapered waveguide.

[0100] When the number of propagation modes increases from 1, the numerical aperture of the optical fiber increases, so the exit angle increases and the length of the tapered waveguide required becomes shorter.

[0101] As described above, by using the optical connector 600 of the third embodiment, it is possible to reduce the amount of axial misalignment of the optical fiber 50. As a result, the length of the tapered waveguide in the optical connector plug 500 can be shortened, and optical loss in the tapered waveguide can be suppressed.

[0102] Furthermore, in this embodiment, the tapered waveguide is formed using light having the same wavelength and propagation mode as the communication light emitted from the core of the optical fiber 50. This allows the tapered waveguide to be formed in a shape that matches the shape of the communication light, thereby suppressing propagation mode conversion within the tapered waveguide.

[0103] A second method for producing the optical connector plug of this embodiment will be described with reference to Figure 20. In the second production method, the core end face of another optical fiber 70 inserted and fixed in another optical connector plug 700 for producing a waveguide is arranged opposite the detachable end face 54 of the ferrule 51, and light of a wavelength that increases the refractive index of the photocurable resin 53 and causes it to harden is irradiated from the core of the optical fiber 50 onto the photocurable resin 53, while light of the same wavelength is irradiated from the core of the other optical fiber 70 onto the photocurable resin 53, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin 53, thereby forming a tapered waveguide 60.

[0104] Specifically, another optical connector plug 700 (a connector plug for fabricating a waveguide) is connected to the optical connector plug 500. The diameter of the core 70a of the optical fiber 70 of the other optical connector plug 700 is larger than the diameter of the core 50a of the optical fiber 50 of the optical connector plug 500. Light sources 69, 89 of a wavelength that increases the refractive index of the photocurable resin 53 and hardens it are connected to the optical fiber 50 of the optical connector plug 500 and the optical fiber 70 of the other optical connector plug 700, respectively, and light of the wavelength is irradiated onto the photocurable resin 53 from the cores 50a, 70a of the optical fibers 50, 70.

[0105] This causes an increase in the refractive index and hardening of the irradiated portion of the photocurable resin 53, producing a tapered waveguide 60 as shown in Fig. 21. After the waveguide 60 is produced, the other optical connector plug 700 and the light source 69 are removed, thereby producing the optical connector plug 500. The other optical connector plug 700 may be a high-precision connector manufactured with minimal error from the design target of the optical connector.

[0106] A third manufacturing method for the optical connector plug of this embodiment will be described with reference to Figure 22. In this third manufacturing method, a condenser lens 62 is used instead of the photomask 62 described in the third manufacturing method of the second embodiment. In this third manufacturing method, light of a wavelength that increases the refractive index of the photocurable resin 53 and hardens it is irradiated onto the photocurable resin 53 from the core of the optical fiber 50, and light of the same wavelength is irradiated onto the photocurable resin 53 from the attachment / detachment end face 54 side via the condenser lens 62, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin 53, thereby forming a tapered waveguide 60.

[0107] 22 , a condenser lens 62 and a light source 88 with a wavelength that increases the refractive index of the photocurable resin 53 and hardens the resin are disposed near the ferrule end face 55 of the optical connector plug 500. A light source 69 with a wavelength that increases the refractive index of the photocurable resin 53 and hardens the resin is connected to the optical fiber 50 of the optical connector plug 500. Light with the wavelength is then irradiated from the core 50 a of the optical fiber and the condenser lens 62, respectively, thereby increasing the refractive index of the irradiated portion of the photocurable resin 53 and hardening the resin, thereby forming a tapered waveguide 60.

[0108] The shape of the condenser lens 62 makes it possible to adjust the mode field diameter and convergence angle of light 88a emitted from the light source 88. By using the condenser lens 62 to irradiate the photocurable resin 53 with light that has a mode field diameter larger than that of the core 50a of the optical fiber 50, it is possible to create a tapered waveguide 60. After the waveguide 60 is created, the condenser lens 62 and the light sources 69 and 88 are removed, and the optical connector plug 500 is produced.

[0109] 23 is a diagram illustrating a method for fabricating an optical connector plug 500 for connecting a multicore fiber. Here, a method for fabricating the optical connector plug 500 using the second fabrication method described above will be described as an example. Another optical connector plug 700 is connected to the optical connector plug 500.

[0110] The optical fiber 50 of the optical connector plug 500 and the optical fiber 70 of another optical connector plug 700 are each connected to a single-core fiber 80 via a fan-out 61. Light sources 69, 89 with a wavelength that increases the refractive index of the photocurable resin 53 and hardens it are connected to each single-core fiber 80, and light of the wavelength is irradiated onto the photocurable resin 53 from the cores 50a, 70a of the optical fibers 50, 70. The diameter of the core 70a of the optical fiber 70 of the other optical connector plug 700 is larger than the diameter of the core 50a of the optical fiber 50 of the optical connector plug 500.

[0111] This causes an increase in the refractive index and hardening of the photocurable resin 53 in the irradiated portion, resulting in the generation of a plurality of tapered waveguides 60 as shown in Fig. 24. After the waveguides 60 are generated, the other optical connector plugs 700 and the fan-out 61 are removed to produce the optical connector plug 500. Although Fig. 23 and Fig. 24 show an example of a multicore fiber having four cores, the number of cores in the multicore fiber may be two or more, and the core arrangement may be any arrangement.

[0112] [Fourth Embodiment] Fig. 1 is a diagram showing an example of a connector plug structure of an optical connector according to a fourth embodiment. The optical connector plug 100 of this embodiment is a multi-fiber optical connector plug similar to the optical connector plug 100 of the first embodiment. The optical connector plug 100 of this embodiment has a waveguide formed using a photocurable resin 13, one end of which is connected to a core end face of an optical fiber 10 inserted and fixed into the optical connector plug 100 and capable of transmitting an optical signal from the core of the optical fiber 10 to the other end, and the end face of the other end is tapered larger than the end face of the one end. The optical connector plug 100 may also have a ferrule 11 capable of holding the connection end of the optical fiber 10 and the photocurable resin 13, and a sealant 14 that forms the detachable end face of the ferrule 11 and prevents the photocurable resin from leaking out. The photocurable resin 13 is filled in the ferrule 11 so as to abut against the connection end of the optical fiber 10.

[0113] The illustrated optical connector plug 100 includes connection ends of a plurality of optical fibers 10 inserted and fixed in a ferrule 11, the ferrule 11, an adhesive 12, a photocurable resin 13 that forms a self-forming optical waveguide, a sealant 14, and an alignment member 16. The sealant 14 is also referred to as a detachable end face 14. The multi-fiber optical connector may be any multi-fiber optical connector that can detachably connect a plurality of optical fibers collectively, and is not limited to a multi-fiber optical connector such as an MT connector or an MPO connector.

[0114] 2, the photocurable resin 13 is connected to the optical fiber 10 inside the ferrule 11, and a tapered waveguide 20 capable of transmitting an optical signal is formed in the photocurable resin 13. One end of the tapered waveguide 20 is connected to the end face of the core 10a of the optical fiber 10, and the other end is connected to the detachable end face 14. The cross-sectional size of the waveguide 20 is larger at the connection position with the detachable end face 14 than at the connection position with the optical fiber end face.

[0115] The sealing material 14 may be disposed in a shape that protrudes from the ferrule end face 15 as shown in FIG. 1 , or may be disposed in a shape that is embedded in the ferrule end face 15 by making the ferrule end face 15 concave as shown in FIG. 2 . The sealing material 14 may have any shape that can prevent the photocurable resin 13 from leaking out from the ferrule end face 15. For example, glass or resin may be used for the sealing material 14, and the sealing material may have any shape that can emit light propagating through the waveguide 20 formed in the photocurable resin 13 or propagate incident light into the waveguide 20 formed in the photocurable resin 13. When a glass material is used for the sealing material 14, a waveguide may be formed inside the glass material by laser drawing or the like.

[0116] As shown in Fig. 4, the optical fibers 10 are arranged at equal intervals by an arranging member 16 toward the ferrule end face 15, and are adhesively fixed to the ferrule 11 by adhesive 12 injected through a hole (not shown) provided in the top of the ferrule 11. In order to arrange the optical fibers 10 at equal intervals, the arranging member 16 is provided with, for example, a V-groove, a semicircular groove, a circular hole, or the like. However, the grooves and holes provided in the arranging member 16 may have any shape as long as they can arrange the optical fibers 10 at equal intervals. Although Fig. 4 shows eight optical fibers arranged, the number of optical fibers 10 is not limited to eight, and may be two or more.

[0117] The optical fibers 10 may be, for example, single-core multimode fibers or multi-core multimode fibers, and may be optical fibers that transmit light of any wavelength in multiple propagation modes. In this embodiment, a case where a multi-core multimode fiber is used will be described.

[0118] A first method for fabricating the optical connector plug of this embodiment will be described with reference to Fig. 8. In the first fabrication method, light having a wavelength that increases the refractive index of the photocurable resin 13 and hardens the resin is irradiated onto the photocurable resin 13 from the core of the optical fiber 10, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin 13, thereby forming a tapered waveguide 20.

[0119] Specifically, a light source 19 with a wavelength that increases the refractive index of the photocurable resin 13 and hardens it is connected to the optical fiber 10 of the optical connector plug 100, and light of that wavelength is irradiated onto the photocurable resin 13 from the core 10a of the optical fiber 10. As a result, the light from the core 10a spreads in a tapered shape within the photocurable resin 13, increasing the refractive index and hardening the irradiated portion of the photocurable resin 13, thereby forming a tapered waveguide 20. After the waveguide 20 is formed, the light source 19 is removed, and the optical connector plug 100 is completed.

[0120] The light from the light source 19 has the same wavelength as the communication light to be transmitted through the optical connector, and the light is propagated in the same propagation mode as that used for communication to generate the waveguide 20 .

[0121] 9, a cladding 21 may be formed around the waveguide 20. Specifically, after the waveguide 20 is formed, the photocurable resin 13 is removed through an injection port 22 provided in the ferrule 11, and instead a photocurable resin 13b capable of forming a cladding 21 having a lower refractive index than the waveguide 20 by light irradiation is injected. Then, a light source 37 having a wavelength that causes the photocurable resin 13b to harden is prepared, and the cladding 21 may be formed by irradiating the light source 37 with light 37a having the wavelength. The injection port 22 may be provided in advance in the ferrule 11 for removing the photocurable resin 13 and injecting the photocurable resin 13b.

[0122] 6 is a diagram showing an example of a connection configuration of an optical connector according to the fourth embodiment. Axial alignment is performed by inserting guide pins (not shown) into guide holes 17 arranged on the ferrule end faces 15, and a spring (not shown) applies a pressing force to the opposing optical connector plugs, thereby forming an optical connector 200 in a form in which the detachable end faces 14 are in close contact with each other, and optical fibers are connected. To reduce return loss, a refractive index matching material 18 may be applied between the detachable end faces 14 (see FIG. 7).

[0123] Assume that a certain propagation mode field diameter of the optical fiber 10 is, for example, 10 μm. Assume that this is expanded to, for example, 20 μm at the detachable end face 14 by the tapered waveguide 20. When axial misalignment occurs in an optical connector connection, the larger the mode field diameter, the smaller the loss and mode conversion caused by the axial misalignment. The relationship between the amount of axial misalignment D of the optical fiber 10 and the proportion T of propagating light that transmits without loss or mode conversion can be expressed by the following equation.

[0124]

[0125] W1 and W2 are the mode field radii of the cores (waveguides 20) of the opposing ferrule end faces 15 of the two optical connector plugs 100 that make up the optical connector 200. When the optical fiber core axis misalignment during connector connection is 2.0 μm, the transmittance is 85.2% when the mode field diameter is 10 μm, and 96.1% when the mode field diameter is 20 μm, according to the above formula. Thus, by expanding the mode field diameter using the waveguide 20, loss and mode conversion can be significantly reduced.

[0126] Furthermore, since the waveguide 20 is formed with light of the same wavelength and propagation mode as the communication light emitted from the core 10a of the optical fiber 10, a tapered waveguide is generated based on the propagation state, thereby suppressing propagation mode conversion within the tapered waveguide 20.

[0127] A second method for producing the optical connector plug of the fourth embodiment will be described with reference to Figure 11. In the second method, the core end face of another optical fiber 30 inserted and fixed in another optical connector plug 300 for producing a waveguide is placed opposite the detachable end face 14 of the ferrule 11, and light of a wavelength that increases the refractive index of the photocurable resin 13 and hardens the resin is irradiated from the core of the optical fiber 10 onto the photocurable resin 13, while light of the same wavelength is irradiated from the core of the other optical fiber 30 onto the photocurable resin 13, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin 13, thereby forming a tapered waveguide 20.

[0128] Specifically, another optical connector plug 300 for fabricating a waveguide (a connector plug for fabricating a waveguide) is connected to the optical connector plug 100. The other optical connector plug 300 includes a plurality of optical fibers 30, a ferrule 31, an adhesive 32, and an alignment member 36. The diameter of the core 30a of the optical fiber 30 of the other optical connector plug 300 is larger than the diameter of the core 10a of the optical fiber 10 of the optical connector plug 100. Light sources 19 and 39 with a wavelength that increases the refractive index of the photocurable resin 13 and hardens it are connected to the optical fiber 10 of the optical connector plug 100 and the optical fiber 30 of the other optical connector plug 300, respectively, and light with the wavelength is irradiated onto the photocurable resin 13 from the cores 10a and 30a of the optical fibers 10 and 30.

[0129] This causes an increase in the refractive index and hardening of the irradiated portion of the photocurable resin 13, forming a tapered waveguide 20 as shown in Fig. 12. After the waveguide 20 is formed, the other optical connector plug 300 and the light source 19 are removed, thereby producing the optical connector plug 100. The other optical connector plug 300 may be a high-precision connector manufactured with minimal error from the design target of the optical connector.

[0130] 13 will be used to explain a third method for producing the optical connector plug 100 in the fourth embodiment. In the third production method, instead of using another optical connector plug 300, a condenser lens 42 is used. That is, light of a wavelength that increases the refractive index of the photocurable resin 13 and causes it to harden is irradiated onto the photocurable resin 13 from the core of the optical fiber 10, and light of the wavelength is also irradiated onto the photocurable resin 13 from the attachment / detachment end face 14 side via the condenser lens 42, thereby causing an increase in the refractive index and hardening of the irradiated portion of the photocurable resin 13, and forming a tapered waveguide 20.

[0131] 13, a condenser lens 42 and a light source 38 of a wavelength that increases the refractive index of and hardens the photocurable resin 53 are disposed near the ferrule end face 15 of the optical connector plug 100. Also, a light source 19 of a wavelength that increases the refractive index of and hardens the photocurable resin 13 is connected to the optical fiber 10 of the optical connector plug 100. Then, by irradiating light of the wavelength from the core 10a of the optical fiber and the condenser lens 42, respectively, the refractive index of the irradiated portion of the photocurable resin 13 increases and hardens, thereby producing a tapered waveguide 20.

[0132] The shape of the condenser lens 42 makes it possible to adjust the mode field diameter and convergence angle of the light 38a emitted from the light source 38. By using the condenser lens 42 to irradiate the photocurable resin 13 with light that has a mode field diameter larger than that of the core 10a of the optical fiber 10, it is possible to create a tapered waveguide 20. After the waveguide 20 is created, the condenser lens 42 and the light sources 19 and 38 are removed, and the optical connector plug 100 is produced.

[0133] In the first manufacturing method described above, optical connector plug 100 is irradiated with light of a wavelength that increases the refractive index of photocurable resin 13 and hardens it, in the second manufacturing method another connector plug 300 for manufacturing a waveguide is used, and in the third manufacturing method a condenser lens 42 is used to irradiate light of the wavelength to photocurable resin 13. Note that the manufacturing method of optical connector plug 100 is not limited to these, and any method may be used as long as it can manufacture tapered waveguide 20.

[0134] A method for fabricating an optical connector plug 100 for connecting a multicore fiber will be described using Figure 14. Here, as an example, a method for fabricating the optical connector plug 100 will be described using the second fabrication method described above. Another optical connector plug 300 is connected to the optical connector plug 100. The core 30a of the optical fiber 30 of the other optical connector plug 300 has cutoff wavelength characteristics equivalent to those of the core 10a of the optical fiber 10 of the optical connector plug 100, and has a diameter larger than the diameter of the core 10a.

[0135] The optical fiber 10 of the optical connector plug 100 and the optical fiber 30 of another optical connector plug 300 are each connected to a single-core fiber 40 via a fan-out 41. Light sources 19, 39 with a wavelength that increases the refractive index of the photocurable resin 13 and hardens it are connected to each single-core fiber 40, and light of the wavelength is irradiated onto the photocurable resin 13 from the cores 10a, 30a of the optical fibers 10, 30.

[0136] This causes an increase in the refractive index and hardening of the photocurable resin 13 in the irradiated portion, forming a plurality of tapered waveguides 20 as shown in Fig. 15. After the waveguides 20 are formed, the other optical connector plugs 300 and the fan-out 41 are removed to produce the optical connector plug 100. Although Fig. 14 and Fig. 15 show an example of a multicore fiber having four cores, the number of cores in the multicore fiber may be two or more, and the core arrangement may be any arrangement.

[0137] The optical connectors of the first to fourth embodiments described above are optical connectors including an optical connector plug, the optical connector plug having a waveguide formed using a photocurable resin, one end of the waveguide being connected to a core end face of an optical fiber inserted and fixed into the optical connector plug, and capable of transmitting an optical signal from the core of the optical fiber to the other end, and the end face of the other end being tapered larger than the end face of the one end.

[0138] Furthermore, a first method for producing (manufacturing) an optical connector plug used in the optical connectors of the first to fourth embodiments includes an optical connector plug having a ferrule capable of holding a connection end of an optical fiber and photocurable resin, the connection end of the optical fiber inserted and fixed within the ferrule, photocurable resin filled within the ferrule so as to abut the connection end of the optical fiber, and a sealant that forms the detachable end face of the ferrule and prevents the photocurable resin from leaking out, and by irradiating the photocurable resin with light from the core of the optical fiber at a wavelength that increases the refractive index of the photocurable resin and hardens the irradiated portion of the photocurable resin, an increase in refractive index and hardening occur in the irradiated portion of the photocurable resin, thereby forming a tapered waveguide.

[0139] A second manufacturing method (manufacturing method) of an optical connector plug used in the optical connectors of the first to fourth embodiments is a manufacturing method of an optical connector plug used in an optical connector, the optical connector plug having a ferrule capable of holding a connection end of an optical fiber and photocurable resin, the connection end of the optical fiber inserted and fixed in the ferrule, the photocurable resin filled in the ferrule so as to abut the connection end of the optical fiber, and a sealant that forms a detachable end face of the ferrule and prevents the photocurable resin from leaking out, and the detachable end face of the ferrule is arranged opposite a core end face of another optical fiber inserted and fixed in another optical connector plug for manufacturing a waveguide, and light of a wavelength that increases the refractive index of the photocurable resin and hardens the photocurable resin from the core of the optical fiber is irradiated onto the photocurable resin, and light of the same wavelength is irradiated onto the photocurable resin from the core of the other optical fiber, thereby increasing the refractive index of the irradiated portion of the photocurable resin and hardening the resin, thereby forming a tapered waveguide.

[0140] A third method for producing (manufacturing) an optical connector plug used in the optical connectors of the first to fourth embodiments is a method for producing an optical connector plug used in an optical connector, the optical connector plug having a ferrule capable of holding a connection end of an optical fiber and photocurable resin, the connection end of the optical fiber inserted and fixed into the ferrule, photocurable resin filled in the ferrule so as to abut against the connection end of the optical fiber, and a sealant that forms a detachable end face of the ferrule and prevents the photocurable resin from leaking out, and the photocurable resin is irradiated with light of a wavelength that increases the refractive index of the photocurable resin and hardens from the core of the optical fiber, and the photocurable resin is irradiated with light of the wavelength from the detachable end face side via a photomask or a focusing lens, thereby increasing the refractive index of the irradiated portion of the photocurable resin and hardening it, thereby forming a tapered waveguide.

[0141] According to the optical connector of this embodiment, it is possible to provide a low-loss optical connector in a combination of fibers having core placement errors due to manufacturing accuracy among optical connectors manufactured to unified specifications.

[0142] Furthermore, according to the method for manufacturing an optical connector plug of this embodiment, when combining fibers that have core placement errors due to manufacturing accuracy in optical connectors manufactured to unified specifications, precise core alignment is not required, and a low-loss optical connector can be easily manufactured, thereby reducing costs.

[0143] Furthermore, by emitting the light that causes curing from the optical fiber core, the tapered waveguide is reliably formed at the position of the light emitted from the optical fiber core, thereby enabling the optical fiber core and the tapered waveguide to be connected with low loss.

[0144] The present disclosure is not limited to the above-described embodiments, and various modifications and combinations are possible.

[0145] 10, 30, 50, 70 Optical fiber 10a, 30a, 50a, 70a Core 10b, 30b, 50b, 70b Cladding 100, 500 Optical connector plug 11, 31, 51, 71 Ferrule 12, 32 Adhesive 13, 13b, 53 Photocurable resin 14, 54 Sealing material (detachable end face) 15, 55 Ferrule end face 16, 36 Arrangement member 18 Refractive index matching material 19, 37, 38, 39, 69, 88, 89 Light source 20, 60 Waveguide (self-written optical waveguide) 200, 600 Optical connector 21 Cladding 22 Inlet 300, 700 Other optical connector plug (connector plug for waveguide fabrication) 37a 38a, 88a Optical 40, 80 Single-core fiber 41, 61 Fan-out 42, 62 Photomask, condenser lens 52, 72 Plug frame 56, 76 Knob 57, 77 Flange 58, 78 Spring 59, 79 Stop ring 63 Sleeve

Claims

1. An optical connector including an optical connector plug, wherein the optical connector plug has a waveguide formed using a photocurable resin, one end of the waveguide being connected to a core end face of an optical fiber inserted and fixed in the optical connector plug, and capable of transmitting an optical signal from the core of the optical fiber to the other end, wherein the end face of the other end is tapered so as to be larger than the end face of the one end.

2. The optical connector according to claim 1, wherein the optical connector plug comprises: a ferrule capable of holding the connection end of the optical fiber and the photocurable resin; and a sealant that forms the detachable end face of the ferrule and prevents the photocurable resin from leaking out.

3. A method for manufacturing an optical connector plug used in an optical connector, the optical connector plug having: a ferrule capable of holding a connection end of an optical fiber and photocurable resin; the connection end of the optical fiber inserted and fixed within the ferrule; photocurable resin filled within the ferrule so as to abut against the connection end of the optical fiber; and a sealant that forms a detachable end face of the ferrule and prevents the photocurable resin from leaking out, wherein light of a wavelength that increases the refractive index of the photocurable resin and hardens the irradiated portion of the photocurable resin is irradiated from the core of the optical fiber onto the photocurable resin, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin, thereby forming a tapered waveguide.

4. A method for manufacturing an optical connector plug as described in claim 3, wherein, after forming the waveguide, the photocurable resin is removed from the portion where the waveguide is not formed, and another photocurable resin capable of forming a cladding having a lower refractive index than the waveguide is filled into the ferrule, and light of a wavelength that causes the other photocurable resin to harden is irradiated from the detachable end face side, thereby hardening the other photocurable resin and forming the cladding around the waveguide.

5. A method for manufacturing an optical connector plug used in an optical connector, the optical connector plug having: a ferrule capable of holding a connection end of an optical fiber and photocurable resin; the connection end of the optical fiber inserted and fixed in the ferrule; photocurable resin filled in the ferrule so as to abut against the connection end of the optical fiber; and a sealant that forms a detachable end face of the ferrule and prevents the photocurable resin from leaking out; the method comprising: arranging a core end face of another optical fiber inserted and fixed in another optical connector plug for fabricating a waveguide so as to face the detachable end face of the ferrule; irradiating the photocurable resin from the core of the optical fiber with light of a wavelength that increases the refractive index of the photocurable resin and hardens it, and irradiating the photocurable resin with light of the same wavelength from the core of the other optical fiber, thereby increasing the refractive index of the light-irradiated portion of the photocurable resin and hardening it, thereby forming a tapered waveguide.

6. The method for manufacturing an optical connector plug according to claim 5, wherein the diameter of the core of said other optical fiber is larger than the diameter of the core of said optical fiber.

7. A method for manufacturing an optical connector plug used in an optical connector, the optical connector plug having: a ferrule capable of holding a connection end of an optical fiber and photocurable resin; the connection end of the optical fiber inserted and fixed within the ferrule; photocurable resin filled in the ferrule so as to abut against the connection end of the optical fiber; and a sealant that forms a detachable end face of the ferrule and prevents the photocurable resin from leaking out, wherein the method comprises irradiating the photocurable resin with light of a wavelength that increases the refractive index of the photocurable resin and hardens it from the core of the optical fiber, and irradiating the photocurable resin with light of the wavelength from the detachable end face side through a photomask or a condenser lens, thereby increasing the refractive index of the irradiated portion of the photocurable resin and hardening it, thereby forming a tapered waveguide.

8. A method for manufacturing an optical connector plug described in any one of claims 4 to 7, wherein the light irradiated from the core of the optical fiber to the photocurable resin has the same wavelength and propagation mode as the communication light to be transmitted through the optical connector.

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