Optical fiber feed through

Abstract

To provide optical fiber feed through capable of achieving a low loss.SOLUTION: Optical fiber feed through of the present invention has: (A) a flange; (B) a tubular member fixed with a first sealant through the flange; and (C) an optical fiber through a through hole of the tubular member. The through hole of the tubular member has a first section, a second section, and a third section from one of end parts of the tubular member. A diameter of the first section is larger than a diameter of the second section and covers a coating of the optical fiber in the first section. Also, the diameter of the second section matches the coating of the optical fiber in the second section, and the optical fiber is directly fixed in the through hole with a second sealant in the third section.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to optical fiber feedthroughs. [Background technology]

[0002] Optical sensors that utilize superconductivity can detect photons with high detection efficiency, high speed, or high energy resolution. These optical sensors that utilize superconductivity must be cooled below their critical temperature to exhibit the superconducting phenomenon. For this reason, superconducting optical sensors are installed inside a refrigerator. The inside of the refrigerator is maintained in a vacuum to thermally isolate it from the external environment. An optical fiber is used to transmit photons from the external environment to the optical sensor, and the optical fiber is guided from the atmosphere outside the refrigerator into the vacuum inside the refrigerator via an optical fiber feedthrough. The optical fiber is optically coupled to the optical sensor, allowing the photons to be detected by the optical sensor.

[0003] With the recent development of quantum technology, there is a demand for optical sensors to be able to measure the quantum state of light generated in the external environment with high fidelity without destroying that quantum state. The quantum state of light is easily destroyed by the loss of photons traveling through optical fiber. Therefore, extremely low loss in the optical fiber, including the optical fiber feedthrough, is required for the entire transmission path.

[0004] Another problem is that light from the external environment can get into optical fibers as stray light and be transmitted through the optical fiber as noise photons. Although the probability of such stray photons getting into optical fibers is low, because the original quantum state consists of an extremely small number of photons at the single-photon level, in industrial applications using photons, even a small number of stray photons can become large noise photons.

[0005] Furthermore, if the airtightness of the optical fiber feedthrough is compromised due to aging or other reasons, it becomes difficult to maintain a vacuum, causing the temperature of the refrigerator to rise and preventing the optical sensor using the superconducting phenomenon from working.

[0006] Here, some examples of documents that disclose structures similar to optical fiber feedthroughs are given below.

[0007] For example, Patent Document 1 discloses an optical fiber sealing tube for introducing an optical fiber signal into equipment requiring airtightness, in which an inner pipe is provided with a resin injection port, an optical fiber cord is passed through the inner pipe, and molten resin is injected through the resin injection port to form an airtight seal. Protective tubes are attached to both ends of the inner pipe to fix both ends of the optical fiber cord. However, spaces are generated on both sides of the airtight seal, which poses a problem in that if the optical fiber cord is bent outside the protective tube, the resulting stress is easily transmitted to the airtight seal.

[0008] Patent Document 2 also discloses the following light guide. Specifically, the light guide uses an optical fiber (in the embodiment, an optical fiber bundle) to guide light emitted from a light source disposed outside a sealed space into the interior of the sealed space. The optical fiber is inserted into a through hole formed in the axial direction of a cylindrical light guide fixing member, and the light guide fixing member has an inlet port formed on its side surface that communicates with the through hole. The coating material of the optical fiber located in the through hole of the light guide fixing member that communicates with the inlet port is peeled off, and the optical fiber is filled with a filler through the inlet port. The light guide fixing member is fixed in a light guide communicating hole formed in a blocking wall of the sealed space in a sealed state so that its position in the rotational direction can be adjusted. In this document, the coating of the optical fiber is partially peeled off and fixed with a filler, but it is difficult to achieve sufficient airtightness for operating a cryogenic refrigerator. Furthermore, the coating is basically single-layered, which presents a problem in that load due to bending of the optical fiber outside the through hole of the light guide fixing member is easily transmitted to the part fixed with the filler. Furthermore, in this document, the inlet of the light guide fixing member is provided outside the sealed space, and the length of the light guide fixing member outside the sealed space becomes long, which may cause problems depending on the installation environment of the light guide. In addition, since the optical fiber bundle is closely spaced, there is a possibility that photons leaking from one optical fiber in the optical fiber bundle may enter another optical fiber as stray light.

[0009] It is known that, for example, as shown in Non-Patent Document 1, a black reinforcing tube is attached to an optical fiber for light-sensitive applications. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 8-171023 [Patent Document 2] Japanese Patent Application Publication No. 4-86705 [Non-patent literature]

[0011] [Non-Patent Document 1] [Searched on March 18, 2024] Internet<URL:https: / / www.thorlabs.co.jp / newgrouppage9.cfm?objectgroup_id=312> Summary of the Invention [Problem to be solved by the invention]

[0012] SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention, according to one aspect, to provide an optical fiber feedthrough that can achieve low optical loss. [Means for solving the problem]

[0013] The optical fiber feedthrough according to the present invention comprises (A) a flange, (B) a tubular member that passes through the flange and is fixed with a first sealing material, and (C) an optical fiber that is passed through a through hole in the tubular member. The through hole in the tubular member has a first section, a second section, and a third section from one end of the tubular member, the diameter of the first section being larger than the diameter of the second section and adapted to fit the coating of the optical fiber in the first section. The diameter of the second section is also adapted to fit the coating of the optical fiber in the second section, and the optical fiber in the third section is directly fixed in the through hole with the second sealing material. [Effects of the Invention]

[0014] According to one aspect, it becomes possible to achieve low optical loss in optical fiber feedthroughs. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a top view of an optical fiber feedthrough according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the optical fiber feedthrough according to the first embodiment. [Figure 3] FIG. 3 is a right side view of the optical fiber feedthrough according to the first embodiment. [Figure 4] FIG. 4 is a left side view of the optical fiber feedthrough according to the first embodiment. [Figure 5] FIG. 5 is a perspective view of the optical fiber feedthrough according to the first embodiment. [Figure 6] FIG. 6 is a perspective view of a tubular member according to the first embodiment. [Figure 7] FIG. 7 is a right side view of the flange according to the first embodiment. [Figure 8] FIG. 8 is a diagram for explaining a method for producing an optical fiber feedthrough according to the first embodiment. [Figure 9] FIG. 9 is a perspective view of an optical fiber feedthrough according to a first example of the second embodiment. [Figure 10] FIG. 10 is a right side view of an optical fiber feedthrough according to a first example of the second embodiment. [Figure 11] FIG. 11 is a perspective view of an optical fiber feedthrough according to a second example of the second embodiment. [Figure 12] FIG. 12 is a right side view of an optical fiber feedthrough according to a second example of the second embodiment. [Figure 13] FIG. 13 is a top view of the optical fiber feedthrough according to the third embodiment. [Figure 14] FIG. 14 is a longitudinal sectional view of an optical fiber feedthrough according to the third embodiment. [Figure 15] FIG. 15 is a side view of an optical fiber feedthrough according to the third embodiment. [Figure 16] FIG. 16 is a cross-sectional view of an optical fiber feedthrough according to the third embodiment. [Figure 17] FIG. 17 is a right side view of the optical fiber feedthrough according to the third embodiment. [Figure 18] FIG. 18 is a left side view of the optical fiber feedthrough according to the third embodiment. [Figure 19]FIG. 19 is a perspective view of an optical fiber feedthrough according to the third embodiment. [Figure 20] FIG. 20 is a perspective view of a tubular member according to the third embodiment. [Figure 21] FIG. 21 is a right side view of the flange according to the third embodiment. [Figure 22] FIG. 22 is a perspective view of an optical fiber feedthrough according to a first example of the third embodiment. [Figure 23] FIG. 23 is a right side view of an optical fiber feedthrough according to a first example of the third embodiment. [Figure 24] FIG. 24 is a perspective view of an optical fiber feedthrough according to a second example of the third embodiment. [Figure 25] FIG. 25 is a right side view of an optical fiber feedthrough according to a second example of the third embodiment. [Figure 26] FIG. 26 is a diagram showing a schematic diagram of an apparatus for an experiment on optical loss. [Figure 27] FIG. 27 is a diagram showing the measurement results of the optical loss. [Figure 28] FIG. 28 is a diagram showing a schematic diagram of an experimental setup for measuring the effectiveness of preventing stray light. [Figure 29] FIG. 29 is a graph showing the results of pulse laser measurements under indoor lighting for the cases of yellow tertiary coating and black tertiary coating. [Figure 30] FIG. 30 is a graph showing the background measurement results under room lighting for the cases of yellow tertiary coating and black tertiary coating. [Figure 31] FIG. 31 is a graph showing the background measurement results when the room lights are turned off for the cases of a yellow tertiary coating and a black tertiary coating. [Figure 32] FIG. 32 is a table summarizing the experimental results of FIGS. [Figure 33] FIG. 33 is a diagram showing a schematic diagram of an experimental device for measuring the amount of leakage. [Figure 34]FIG. 34 is a diagram showing the measurement results of the amount of leakage. [Figure 35] FIG. 35 is a diagram showing the measurement results of the cooling performance. DETAILED DESCRIPTION OF THE INVENTION

[0016] [Embodiment 1] 1 shows a top view of an optical fiber feedthrough according to this embodiment. The feedthrough according to this embodiment includes a flange 30 connected to, for example, a vacuum chamber, a substantially cylindrical tubular member 10 having a through-hole through which a partially coated optical fiber strand 20 is passed, and a strain relief 15 attached to the tip of the tubular member 10.

[0017] The outer frame portion 30a of the flange 30 is attached to, for example, the outer wall of a vacuum chamber, and can be formed in any shape to fit that part. After the flange 30 is connected to the vacuum chamber, the right side of the flange 30 is exposed to the atmosphere, and the left side of the flange 30 is in a vacuum. The flange 30 also has a holding portion 30d in which a recess is provided to be filled with a sealing material that fixes the tubular member 10.

[0018] The tubular member 10 is made of, for example, metal, passes vertically through the center of the flange 30, and is fixed to the flange 30 with a sealant. The outer diameter of the left end of the tubular member 10 is smaller than the outer diameter of the right end, and a strain relief 15 is attached. In addition, an injection port 10b for a sealant 12 is provided on the side of the tubular member 10, to the left of the flange 30, i.e., on the side that is placed in a vacuum. The sealant 12 is, for example, a black resin, and fixes the optical fiber 20 in the through-hole of the tubular member 10 and hermetically seals it. The injection port 10b may be located on the side that is placed in the atmosphere, but in that case, the length of the portion of the tubular member 10 that is placed in the atmosphere would be long, which may cause space problems.

[0019] As defined in JIS C 6835:2017, the optical fiber 20 according to this embodiment has an optical fiber cladding whose exterior is primarily coated with a plastic material such as ultraviolet-curable resin or silicone resin. The optical fiber 20 is coated with a secondary coating 16 and a tertiary coating 17 from the right side of the right end 10d of the tubular member 10, and a secondary coating 13 from the right side of the left end of the strain relief 15. The tertiary coating 17 is a black coating to prevent stray light.

[0020] The strain relief 15 has a right end portion attached to the left end portion of the tubular member 10, and has a tapered shape from right to left because the optical fiber strand 20 coated with the secondary coating 13 comes out from the left end portion.

[0021] FIG. 2 shows a cross section taken along line AA' in FIG. 1, ie, a cross section of the feedthrough.

[0022] On the atmosphere side of the flange 30, a recess 30b is provided in the holding portion 30d, into which a sealant 31 for fixing the tubular member 10 is filled. The sealant 31 prevents air leakage from the gap between the tubular member 10 and the flange 30. On the vacuum side, the inside of the flange 30 is configured to match the shape of the device to which the feedthrough is attached. For example, in FIG. 2, a recess 30c is provided as an example of attachment in accordance with the NW / KF standard defined in the ISO standard (ISO 2861). Furthermore, if there is no problem with connection to the device inside the vacuum chamber, a sealant 32 may be used to reinforce the gap between the tubular member 10 and the flange 30. A hole through which the tubular member 10 passes is provided in the center of the flange 30, and the diameter of the hole in the flange 30 also changes at the portion 10a where the outer diameter of the tubular member 10 changes. This allows the tubular member 10 to fit onto the flange 30, and prevents the tubular member 10 from being drawn into the vacuum even if the left side of the flange 30 is in a vacuum state and atmospheric pressure is applied.

[0023] The through hole of the tubular member 10 is divided into a first section 10e, a second section 10f, a third section 10g, and a fourth section 10h. In the first section 10e, the optical fiber 20 is coated with a secondary coating 16 and a tertiary coating 17, and the diameter of the coating is adjusted to match these coatings. In the second section 10f, the optical fiber 20 is coated with a secondary coating 16, and the diameter of the coating is adjusted to match these coatings. In other words, the inner diameter of the first section 10e is larger than the inner diameter of the second section 10f.

[0024] In the third section 10g, the optical fiber 20 is directly fixed in the through-hole of the tubular member 10 by the sealing material 12. In this embodiment, the diameter of the third section 10g is larger than the diameter of the second section 10f, in order to provide sufficient space for fixing the optical fiber 20 with the sealing material 12. The third section 10g has a length sufficient for maintaining airtightness while suppressing the stress that the sealing material 12 applies to the optical fiber 20. The diameter of the injection port 10b is determined taking into consideration the viscosity of the sealing material 12, etc., so that any air bubbles that may enter the sealing material 12 can be removed through the injection port 10b.

[0025] The sealing material 12 may extend toward the second section 10f or the fourth section 10h and come into contact with the secondary coating 16 and the tertiary coating 17, the secondary coating 13 and the tertiary coating 14, but must remain within the outermost diameter of the tubular member 10 from the injection port 10b.

[0026] In the fourth section 10h, the optical fiber 20 is coated with a secondary coating 13 and a tertiary coating 14, and the diameter thereof is adapted to match these coatings. That is, the diameter of the fourth section 10h is the same as the diameter of the first section 10e.

[0027] The tubular member 10 protects the optical fiber 20 from bending. Furthermore, the optical fiber 20 is protected from physical damage at the end 10d side of the tubular member 10 by being coated with the secondary coating 16 and the tertiary coating 17, and similarly, at the end 10c side of the tubular member 10, the attachment of the secondary coating 13 and the tertiary coating 14 and the strain relief 15 also protects the optical fiber 20 from physical damage.

[0028] Furthermore, the optical fiber 20 is coated with the secondary coating 16 and the tertiary coating 17 in the first section 10e, and with the secondary coating 16 in the second section 10f, so that it is stably held in the center of the through hole. In this way, since not only the first section 10e but also the second section 10f is provided and coated accordingly, the effects of bending and vibration of the optical fiber are less likely to be transmitted to the sealing material 12, which leads to maintaining airtightness and sealing properties for a long period of time.

[0029] Moreover, since the optical fiber 20 is fixed directly by the sealing material 12 in the third section 10g, stress is less likely to be applied to the optical fiber 20, thereby achieving low loss. Furthermore, given the above-described coating state at the ends 10d and 10c of the tubular member 10, the bending radius of the optical fiber 20 is expected to be equal to or greater than the minimum bending radius allowable for the optical fiber 20, and optical loss is expected to be zero or very small. Furthermore, the provision of not only the first section 10e but also the second section 10f, which stably holds the optical fiber 20, also reduces stress on the optical fiber 20, contributing to suppression of optical loss.

[0030] In this figure, the optical fiber 20 is coated with the secondary coating 13 and the tertiary coating 14 for a certain length outside the fourth section 10h, i.e., outside the left end 10c of the tubular member 10, thereby protecting the optical fiber 20. On the vacuum side, the optical fiber 20 is coated with the secondary coating 13 and is pulled out from a hole provided at the tip of the strain relief 15. The strain relief 15 protects the optical fiber 20 and accommodates the portion coated with the secondary coating 13 and the tertiary coating 14, as well as the portion coated with the secondary coating 13. The diameter of the hole at the tip of the strain relief 15 is adjusted to fit the secondary coating 13, and this portion protects the optical fiber 20.

[0031] 3 shows a right side view of the optical fiber feedthrough. The outermost part is the outer frame part 30a of the flange 30, inside which is the holding part 30d, and further inside which is the sealing material 31 filled in the recess 30b provided in the holding part 30d. The tubular member 10 fixed with the sealing material 31 is provided in the center of the recess 30b, and the through hole of the tubular member 10 has the tertiary coating 17 on the outside, the secondary coating 16 on the inside thereof, and the optical fiber 20 passing through the center.

[0032] 4 shows a left side view of the optical fiber feedthrough. The outermost part is the outer frame portion 30a of the flange 30, inside which is provided a recess 30c. Within this recess 30c is a sealing material 32 that secures the tubular member 10, but since the strain relief 15 is attached to the outside of the tubular member 10, the tubular member 10 itself is not visible. The optical fiber strand 20 covered with the secondary coating 13 is drawn out to the vacuum side at the center.

[0033] Figure 5 shows a perspective view of an optical fiber feedthrough viewed obliquely from above on the vacuum side. A tubular member 10 passes through a flange 30, and the tubular member 10 is fixed by a sealant 31 in a recess 30b provided in a holding portion 30d. In this example, the tubular member 10 is also fixed by a sealant 32 in a recess 30c. A strain relief 15 is attached to the vacuum side end of the tubular member 10, and an optical fiber 20 coated with a secondary coating 13 is drawn out to the vacuum side. On the atmosphere side, an optical fiber 20 coated with a secondary coating 16 and a tertiary coating 17 is inserted into the through-hole of the tubular member 10.

[0034] Furthermore, Fig. 6 shows a perspective view of the tubular member 10 alone. As shown in Fig. 6, the outer diameter of the tubular member 10 changes at a portion 10a in the center of the tubular member 10, with the outer diameter at end 10d being larger than the outer diameter at end 10c. This allows the tubular member 10 to fit inside the hole of the flange 30. The injection port 10b is connected to a third section 10g in the through hole of the tubular member 10, and allows the sealing material 12 to be injected.

[0035] Because the tubular member 10 and the flange 30 are fitted together in this manner, the stress applied to the sealing material 31 and the sealing material 32 is reduced, and it is expected that the sealing performance can be maintained for a long period of time.

[0036] Fig. 7 shows a right side view of the flange 30 alone. As shown in Fig. 7, hole 30e formed in recess 30c of holding portion 30d becomes hole 30f having a smaller diameter than hole 30e midway, and hole 30e is in contact with the right side of portion 10a of tubular member 10 (end 10d side), and hole 30f is in contact with the left side of portion 10a of tubular member 10 (end 10c side).

[0037] The above-described structure not only achieves low loss but also maintains airtightness, and furthermore, by employing the black tertiary coating 17, it is possible to prevent stray light.

[0038] The optical fiber feedthrough according to this embodiment is fabricated in the following manner.

[0039] (1) The flange 30 and the tubular member 10 are prepared in advance in the shapes shown in FIGS.

[0040] (2) An optical fiber 20 is coated with a secondary coating 16 having the lengths of the second section 10f and the first section 10e plus a length required on the atmospheric side of the tubular member 10, and a tertiary coating 17 having the length of the first section 10e plus a length required on the atmospheric side of the tubular member 10, and is then inserted into the through-hole of the tubular member 10 from the right side (atmosphere side) of the tubular member 10. As shown in Figure 8 (A) , the optical fiber 20 is coated with the atmospheric-side secondary coating 16 and tertiary coating 17 and passed through the through-hole of the tubular member 10. A connector is attached to the right end of the optical fiber 20.

[0041] (3) A secondary coating 13 having the length of the fourth section 10h plus a length required on the vacuum side of the tubular member 10, and a tertiary coating 14 having the length of the fourth section 10h plus a length required on the vacuum side of the tubular member 10 (for example, a small length as shown in FIG. 2) are prepared (the left member in FIG. 8A), and these are used to coat the optical fiber 20 from the left side, resulting in the state shown in FIG. 8B.

[0042] (4) After that, the sealing material 12 is injected through the injection port 10b and waited until the sealing material 12 hardens. If any air bubbles are present, they are removed.

[0043] (5) After the sealing material 12 has solidified, insert it into the hole from the atmosphere side of the flange 30, place the sealing material 31 in the recess 30b of the flange 30, and wait until it hardens. Alternatively, the sealing material 32 may be placed in the recess 30c.

[0044] (6) Then, the strain relief 15 is inserted from the left side of the optical fiber 20 with the secondary coating 13, and is placed over the left side of the tubular member 10. This results in the state shown in Figure 8(C).

[0045] In this way, the optical fiber feed-through structure shown in FIGS. 1 to 5 can be realized.

[0046] [Embodiment 2] In the first embodiment, one tubular member 10 with one optical fiber strand 20 passing through it is made to pass through the flange 30, but if the flange 30 is large enough, multiple tubular members 10 may be made to pass through the flange.

[0047] 9 shows a perspective view of an optical fiber feedthrough in which a flange 40 is used that conforms to the NW / KF standard (NW16 in this case) defined in the ISO standard (ISO2861) and has a structure similar to that of the flange 30 in the first embodiment. The flange 40 differs from the flange 30 in that it has holes through which four tubular members 10, each carrying one optical fiber 20, pass. The sealing material 32 is omitted from Fig. 9.

[0048] 10 shows a right side view of the optical fiber feedthrough according to this embodiment. A recess 40b is provided in the holding portion 40d of the flange 40, and the recess 40b is filled with a sealing material 41. Each of the four tubular members 10 is the same as in the first embodiment.

[0049] Fig. 11 shows a perspective view of an optical fiber feedthrough in which a flange 50 is used that conforms to the NW / KF standard (NW25 in this case) defined in the ISO standard (ISO2861) and has a structure similar to that of the flange 30 in the first embodiment. The flange 50 differs from the flange 30 in that it has holes through which eight tubular members 10, each with one optical fiber 20 passing, pass. The sealing material 32 is omitted from Fig. 11.

[0050] Fig. 12 shows a right side view of the optical fiber feedthrough shown in Fig. 11. A recess 50b is provided in the holding portion 50d of the flange 50, and the recess 50b is filled with a sealing material 51. Each of the eight tubular members 10 is the same as in the first embodiment.

[0051] As described above, the optical fiber feedthrough according to the first embodiment can be easily expanded to a similar structure including a plurality of tubular members 10. There is no limit to the number of members if the size of the flange is changed. In this way, the tubular member 10 is passed through the recess 40b or 50b in the holding portion 40d or 50d of the flange 40 or 50 and fixed while maintaining hermeticity with the sealing material 41 or 51, which makes it easy to expand the number of tubular members 10.

[0052] Even if a plurality of tubular members 10 are introduced, the optical fibers 20 are independent of each other, and the problem of crosstalk does not occur.

[0053] [Embodiment 3] In the first and second embodiments, an example has been shown in which a single optical fiber 20 is used, but it is also possible to use, for example, a ribbon-type optical fiber defined in JIS C6838:2020. A ribbon-type optical fiber is a plurality of optical fiber strands integrated together using an ultraviolet curing resin or the like. Here, a case in which a 12-core optical fiber 200 is used will be described. However, the number of cores is arbitrary.

[0054] 13 shows a top view of an optical fiber feedthrough according to this embodiment. The feedthrough according to this embodiment includes a flange 300 connected to, for example, a vacuum chamber, an elliptical or rectangular tubular member 100 having a through-hole through which a partially coated optical fiber 200 is passed, and a strain relief 150 attached to the tip of the tubular member 100.

[0055] The outer frame portion 300a of the flange 300 is attached to, for example, the outer wall of a vacuum chamber, and can be shaped to fit the shape of that portion. After the flange 300 is connected to the vacuum chamber, the right side of the flange 300 is exposed to the atmosphere, and the left side of the flange 300 is in a vacuum. The flange 300 also has a holding portion 300d that is provided with a recess into which a sealing material that fixes the tubular member 100 is filled.

[0056] The tubular member 100 is made of, for example, metal, penetrates vertically through the center of the flange 300, and is fixed to the flange 300 with a sealant. The outer diameter of the left end of the tubular member 100 is smaller than the outer diameter of the right end, and a strain relief 150 is attached. In addition, an injection port 100b for the sealant 120 is provided on the side (here, the top side) of the tubular member 100, to the left of the flange 300, i.e., on the side that is placed in a vacuum. Note that, because the optical fiber 200 is tape-shaped, an injection port 100b is also provided on the bottom side of the tubular member 100 so that the sealant 120 can be appropriately injected. The sealant 120 is, for example, a black resin, and fixes the optical fiber 200 in the through-hole of the tubular member 100 and hermetically seals it. The position of the injection port 100b may be provided on the side that is placed in the atmosphere, but in that case the length of the part of the tubular member 100 that is placed in the atmosphere will be long, which may cause problems in terms of space.

[0057] The optical fiber 200 is covered with a secondary coating 160 and a tertiary coating 170 from the right side of the right end 100d of the tubular member 100, and a secondary coating 130 from the right side of the left end of the strain relief 150. The tertiary coating 170 is a black coating to prevent stray light.

[0058] The strain relief 150 has a right end portion attached to the left end portion of the tubular member 100, and has a tapered shape from right to left because the optical fiber core 200 coated with the secondary coating 130 comes out from the left end portion.

[0059] FIG. 14 shows a cross section taken along line BB' in FIG. 13, ie, a vertical cross section of the feedthrough.

[0060] On the atmosphere side of the flange 300, a recess 300b is provided in a holding portion 300d, into which a sealant 310 for fixing the tubular member 100 is filled. A recess 300c is also provided on the vacuum side of the flange 300. The sealant 310 prevents air from leaking from the gap between the tubular member 100 and the flange 300. Furthermore, if the recess 300c does not interfere with connection to the device in the vacuum chamber, it is sealed with a sealant 320. A hole is provided in the center of the flange 300 through which the tubular member 100 passes. At a portion 100a where the outer diameter of the tubular member 100 changes, the diameter of the hole in the flange 300 also changes. This allows the tubular member 100 to fit into the flange 300, preventing the tubular member 100 from being drawn into the vacuum even if the left side of the flange 300 is in a vacuum state and atmospheric pressure is applied.

[0061] The through hole of the tubular member 100 is divided into a first section 100e, a second section 100f, a third section 100g, and a fourth section 100h. In the first section 100e, the optical fiber 200 is coated with a secondary coating 160 and a tertiary coating 170, and the diameter of the first section 100e is adjusted to match these coatings. In the second section 100f, the optical fiber 200 is coated with a secondary coating 160, and the diameter of the second section 100f is adjusted to match this coating. In other words, the diameter of the through hole in the first section 100e is larger than the diameter of the through hole in the second section 100f. Note that, in this application, even if the cross section of a through hole is elliptical or rectangular, the major axis or long side and the minor axis or short side are referred to as the diameter.

[0062] In the third section 100g, the optical fiber 200 is directly fixed in the through-hole of the tubular member 100 by the sealing material 120. In this embodiment, the diameter of the third section 100g is larger than that of the second section 100f to provide sufficient space for the sealing material 120 to fix the optical fiber 200. The third section 100g has a length sufficient for maintaining airtightness while suppressing the stress that the sealing material 120 applies to the optical fiber 200. The diameter of the injection port 100b is determined taking into account the viscosity of the sealing material 120, etc., so that air bubbles can be removed from the sealing material 120 if they are trapped therein. The injection ports 100b are provided on both the upper and lower sides in FIG. 14. This is to ensure that the sealing material 120 is injected reliably because the optical fiber 200 is tape-shaped.

[0063] The sealing material 120 may extend toward the second section 100f or the fourth section 100h and come into contact with the secondary coating 160 and the tertiary coating 170, the secondary coating 130 and the tertiary coating 140, but must remain within the outermost diameter of the tubular member 100 from the injection port 100b.

[0064] In the fourth section 100h, the optical fiber 200 is coated with a secondary coating 130 and a tertiary coating 140, and the diameter thereof is adapted to match these coatings. That is, the diameter of the fourth section 100h is the same as the diameter of the first section 100e.

[0065] The tubular member 100 protects the optical fiber 200 from bending. Furthermore, the optical fiber 200 is protected from physical damage on the end 100d side of the tubular member 100 by being coated with the secondary coating 160 and the tertiary coating 170, and similarly, the optical fiber 200 is protected from physical damage on the end 100c side of the tubular member 100 by the attachment of the secondary coating 130 and the tertiary coating 140 and the strain relief 150.

[0066] Furthermore, the optical fiber 200 is coated with the secondary coating 160 and the tertiary coating 170 in the first section 100e, and with the secondary coating 160 in the second section 100f, so that it is stably held in the center of the through hole. In this way, since not only the first section 100e but also the second section 100f is provided and coated accordingly, the effects of bending and vibration of the optical fiber are less likely to be transmitted to the sealing material 120, which leads to maintaining airtightness and sealing properties for a long period of time.

[0067] Moreover, since the optical fiber 200 is fixed directly by the sealing material 120 in the third section 100g, stress is less likely to be applied to the optical fiber 200, thereby achieving low optical loss. Furthermore, given the above-described coating state at the ends 100d and 100c of the tubular member 100, the bending radius of the optical fiber 200 is expected to be equal to or greater than the minimum bending radius allowable for the optical fiber 200, and optical loss is expected to be zero or very little. Furthermore, the provision of not only the first section 100e but also the second section 100f, which stably holds the optical fiber 200, also reduces stress on the optical fiber 200, contributing to suppression of optical loss.

[0068] In this figure, the optical fiber 200 is coated with the secondary coating 130 and the tertiary coating 140 for a small length outside the fourth section 100h, i.e., outside the left end 100c of the tubular member 100, thereby protecting the optical fiber 200. On the vacuum side, the optical fiber 200 is coated with the secondary coating 130 and is pulled out from a hole provided at the tip of the strain relief 150. The strain relief 150 protects the optical fiber 200 and accommodates the portion coated with the secondary coating 130 and the tertiary coating 140, as well as the portion coated with the secondary coating 130. The diameter of the hole at the tip of the strain relief 150 is adjusted to fit the secondary coating 130, and this portion protects the optical fiber 200.

[0069] Fig. 15 is a side view of the optical fiber feedthrough shown in Fig. 9. Fig. 16 is a cross-sectional view taken along plane CC' in Fig. 15. Unlike the cross-section in Fig. 14, Fig. 16 shows 12 bare optical fibers because the optical fiber core 200 has been cut, although it is difficult to see in the drawing. Another difference is that the injection port 100b is not visible. Other than that, it is the same as Fig. 14.

[0070] 17 shows a right side view of an optical fiber feedthrough according to this embodiment. The outermost portion is an outer frame portion 300a of a flange 300, and inside that is a holding portion 300d. Further inside is a sealant 310 filled in a recess 300b provided in the holding portion 300d. The tubular member 100 fixed with the sealant 310 is provided in the center of the recess 300b. The through-hole of the tubular member 100 has a tertiary coating 170 on the outside, a secondary coating 160 on the inside, and an optical fiber 200 passing through the center.

[0071] 18 shows a left side view of an optical fiber feedthrough according to this embodiment. The outermost part is an outer frame portion 300a of a flange 300, and inside this is provided a recess 300c. Within this recess 300c is a sealing material 320 that fixes the tubular member 100, but since the strain relief 150 is attached to the outside of the tubular member 100, the tubular member 100 itself is not visible. The optical fiber 200 covered with the secondary coating 130 is drawn out to the vacuum side at the center.

[0072] 19 shows a perspective view of an optical fiber feedthrough as viewed obliquely from above on the vacuum side. A tubular member 100 passes through a flange 300, and the tubular member 100 is fixed by a sealant 310 in a recess 300b provided in a holding portion 300d. Here, the tubular member 100 is also fixed by a sealant 320 in a recess 300c. A strain relief 150 is attached to the vacuum side end of the tubular member 100, and an optical fiber 200 coated with a secondary coating 130 is drawn out to the vacuum side. On the atmosphere side, an optical fiber 200 coated with a secondary coating 160 and a tertiary coating 170 is inserted into a through-hole in the tubular member 100.

[0073] Furthermore, Fig. 20 shows a perspective view of the tubular member 100 alone. As shown in Fig. 20, the outer diameter of the tubular member 100 changes at a portion 100a in the center of the tubular member 100, with the outer diameter at end 100d being larger than the outer diameter at end 100c. This allows the tubular member 100 to fit inside the hole of the flange 300. The injection port 100b is connected to a third section 100g of the through hole of the tubular member 100, and is designed to allow the sealing material 120 to be injected.

[0074] Because the tubular member 100 and the flange 300 are fitted together in this manner, stress applied to the sealing material 310 and the sealing material 320 is reduced, and it is expected that the sealing performance can be maintained for a long period of time.

[0075] Fig. 21 shows a right side view of the flange 300 alone. As shown in Fig. 21, hole 300e formed in recess 300b of holding portion 300d becomes hole 300f having a smaller diameter than hole 300e midway, and hole 300e is in contact with the right side of portion 100a of tubular member 100 (end 100d side), and hole 300f is in contact with the left side of portion 100a of tubular member 100 (end 100c side).

[0076] The above-described structure not only achieves low loss but also maintains airtightness, and furthermore, by employing the black tertiary coating 170, it is possible to prevent stray light.

[0077] The method for fabricating the optical fiber feedthrough structure according to this embodiment is the same as that according to the first embodiment, and therefore a description thereof will be omitted.

[0078] [Embodiment 4] In the third embodiment, one tubular member 100 with one optical fiber core 200 passing through it is made to pass through the flange 300, but as in the second embodiment, if the flange 300 is large enough, multiple tubular members 100 may be made to pass through the flange.

[0079] 22 shows a perspective view of an optical fiber feedthrough in the case where a flange 400 is used that conforms to the NW / KF standard (here, NW16) defined in the ISO standard (ISO2861) and has a structure similar to that of the flange 300 in the third embodiment. The flange 400 differs from the flange 300 in the portion having holes through which three tubular members 100, each with one optical fiber 200 passing therethrough, pass.

[0080] 23 shows a right side view of an optical fiber feedthrough according to this embodiment. A recess 400b is provided in the holding portion 400d of the flange 400, and the recess 400b is filled with a sealing material 410. The three tubular members 100 are the same as those in the third embodiment. Here, the three tubular members 100 are arranged vertically, but the arrangement is not limited to this.

[0081] In this way, three 12-core optical fiber cores 200 are used, so a total of 36 optical fiber cores can be introduced into the vacuum chamber.

[0082] 24 shows a perspective view of an optical fiber feedthrough in the case where a flange 500 is used that conforms to the NW / KF standard (NW25 in this case) defined in the ISO standard (ISO2861) and has a structure similar to the flange 300 in the third embodiment. The flange 500 differs from the flange 300 in the portion having holes through which eight tubular members 100, each with one optical fiber 200 passing therethrough, pass.

[0083] Fig. 25 shows a right side view of the optical fiber feedthrough shown in Fig. 24. A recess 500b is provided in the holding portion 500d of the flange 500, and the recess 500b is filled with a sealing material 510. Each of the eight tubular members 100 is the same as in the third embodiment.

[0084] In this way, eight 12-core optical fiber cores 200 are introduced into the vacuum chamber, so a total of 96 optical fiber cores can be introduced into the vacuum chamber.

[0085] As described above, the optical fiber feedthrough according to the third embodiment can be easily expanded to a similar structure including a plurality of tubular members 100. There is no limit to the number of members if the size of the flange is changed. In this way, the tubular members 100 are passed through the recesses 400b or 500b in the holding portions 400d or 500d of the flanges 400 or 500 and fixed with the sealing material 410 or 510 while maintaining hermeticity, which makes it easy to expand the number of tubular members 100.

[0086] [Examples and their effects] 1. Optical loss Optical loss is an important characteristic of optical fiber feedthroughs, especially in the field of quantum information. If optical loss exists, photons entering from the atmosphere side are lost in the feedthrough, causing a serious problem in that correct quantum information cannot be transmitted to the vacuum side. Therefore, optical loss must be kept to a minimum.

[0087] Here, an experiment is carried out using a device such as that shown in FIG. 26, for example, with respect to a feedthrough having four tubular members 10 as shown in FIG. 8 and through which four optical fiber strands 20 pass.

[0088] In the device shown in Figure 26, a light source outputting a 1550 nm laser is connected to each optical fiber in the feedthrough via an isolator, a half-wave plate (HWP), a polarizer (POL), a shutter, a 50:50 spectrometer, and connectors. A power meter 1 is connected to the spectrometer to measure the input light. Each optical fiber in the feedthrough is fused to the optical fiber on the experimental equipment side. As shown in Figure 8, the optical fiber on the air side of the feedthrough is connected to a power meter 2 to measure the output light via an optical connector connected to that optical connector. The loss of the optical connectors and fusion points was evaluated separately and excluded from the experimental results to derive the loss of the feedthrough alone. The loss at each fusion point was 0.02 dB. The loss of the optical connector was minimized by adjusting the angle of the optical fiber, resulting in a value of less than 0.009 dB.

[0089] The experimental results are shown in Fig. 27. Fig. 27 shows the optical loss [dB], average value, standard deviation, and 95% confidence interval for each of the four optical fibers. As shown, the loss due to the feedthrough in this embodiment is -7.3 × 10 on average. -5 It was found that the maximum value in the 95% confidence interval was 0.013 dB or less (0.3%) in dB. This shows that the feedthrough according to this embodiment has almost no effect on the optical fiber transmittance.

[0090] 2. Black tertiary coating In this embodiment, stray light is prevented by using a black material with high light blocking properties for the atmosphere-side tertiary coating 17 or 170. An experiment was conducted to confirm this effect.

[0091] The experiment was conducted using the apparatus shown in FIG. 28. Specifically, the optical fiber feedthrough according to this embodiment was connected to a quantum sensor installed in a refrigerator, and then connected to a light source (pulse laser) via a connector, an optical isolator, and an optical attenuator. A pulse laser with a wavelength of 1.5 μm was used as the light source, with the quantum information communication field in mind. The intensity was adjusted using an optical attenuator to produce weak light with an average number of photons per pulse of approximately 3, and the light was output toward the quantum sensor. The three optical fibers between the light source and the connector were coated with a black tertiary coating. As a comparative example, it is preferable to use an optical fiber on the atmospheric side of the optical fiber feedthrough coated with a yellow tertiary coating. However, this was simulated here by inserting an optical fiber patch cable (1 m long) with a yellow tertiary coating between the optical isolator and the optical fiber feedthrough.

[0092] 1) Measurement results of pulsed laser under indoor lighting Figure 29 shows the relationship between photon energy [eV] and photon counts using a pulsed laser for the cases where a yellow tertiary coating was used (dotted line) and where a black tertiary coating was used (solid line). The illuminance under room lighting was approximately 800 lx.

[0093] In Figure 29, it can be seen that in the case of the black tertiary coating, optical pulses are correctly detected at energies that are integer multiples of 0.8 eV, which corresponds to the energy of one photon with a wavelength of 1.5 μm.

[0094] On the other hand, in the case of the yellow tertiary coating, the continuum component overlaps in the photon energy range from 1.44 eV to 2.24 eV (corresponding to wavelengths from 550 nm to 860 nm), which clearly indicates that photons of room white light penetrate into the optical fiber through the yellow tertiary coating. In particular, characteristic peaks are seen at photon energies of 1.84 eV and 2.08 eV, which correspond to wavelengths of 673 nm and 693 nm, respectively.

[0095] This shows that using a black tertiary coating on the optical fiber on the atmospheric side of the optical fiber feedthrough is effective from the viewpoint of preventing the intrusion of stray light.

[0096] The peak at 0.6 eV (wavelength 2100 nm) represents the photon counting result due to blackbody radiation from room temperature.

[0097] 2) Measurement results of background photons under indoor lighting The transmission of the pulsed laser was stopped by an optical isolator, and the stray photons (i.e., background photons) entering from the optical fiber between the optical isolator and the optical fiber feedthrough were evaluated. Figure 30 shows the relationship between photon energy [eV] and background photon counts for the cases where a yellow tertiary coating was used (dotted line) and where a black tertiary coating was used (solid line).

[0098] In the case of the yellow tertiary coating, it is clearly seen that a continuous component exists in the visible range, whereas in the case of the black tertiary coating, the stray photons are effectively suppressed.

[0099] The dark count rate was calculated from all photon counts with photon energy of 1.0 eV or more (wavelength of 1240 nm or less), and was 7.76 kcps for the yellow tertiary coating and 0.326 cps for the black tertiary coating.

[0100] In other words, it was found that the dark count rate was reduced to 1 / 24,000 by using the black tertiary coating compared to the case where the yellow tertiary coating was used.

[0101] 3) Measurement results of background photons when indoor lighting is turned off The transmission of the pulsed laser was stopped by the optical isolator, and the room lights were also turned off, and stray photons (i.e., background photons) entering from the optical fiber between the optical isolator and the optical fiber feedthrough were evaluated.

[0102] Even in this case, the laboratory environment was not completely dark, and there was light from the experimental equipment and PC monitors. The brightness in this environment was so low that it was difficult to walk around the laboratory, and the illuminance was 0.25 lx.

[0103] Figure 31(a) shows the relationship between photon energy [eV] and background photon counts when a yellow tertiary coating is used, and (b) shows the relationship between photon energy [eV] and background photon counts when a black tertiary coating is used.

[0104] As can be seen, the background photon counts for the yellow tertiary coating are significantly reduced compared to the results shown in Figure 30. However, background photons in the visible range are still observed. For the black tertiary coating, there is almost only a peak corresponding to the photon count results due to blackbody radiation from room temperature.

[0105] The dark count rate for photon energies above 1.0 eV is 0.264 cps for the black tertiary coating and 6.74 cps for the yellow tertiary coating.

[0106] As mentioned above, the illuminance near the optical fiber feedthrough in this experiment was 0.25 lx. Therefore, in the case of a yellow tertiary coating, it is estimated that the illuminance must be 0.01 lx or less to obtain the same dark count as when a black tertiary coating is used.

[0107] The dark count rates in the second and third experiments are summarized in Figure 32. As shown above, by using a black tertiary coating for the air-side tertiary coating, the dark count rate can be kept below 1 cps even under indoor lighting. This suggests the high practicality of the optical fiber feedthrough according to this embodiment, in that a low dark count rate can be obtained regardless of the environment, including applications in the quantum information field.

[0108] 3. Demonstration of hermetic sealing and low-temperature environment operation It is preferable to minimize the area where the optical fiber 20 or the optical fiber core 200 contacts the sealing material 12 or 120, thereby suppressing the stress applied to the optical fiber 20 or the optical fiber core 200 and minimizing the resulting optical loss. For example, in the first embodiment, the sealing material 12 has a diameter of 2 mm or less and a length of 6 mm or less.

[0109] It was confirmed whether the airtight sealing using such a sealing material had sufficient performance for practical use.

[0110] In this demonstration, 1) the amount of leakage was evaluated using a leak detector, and 2) the cooling performance of the refrigerator was evaluated using an optical fiber feedthrough.

[0111] 1) Evaluation of the amount of leak by the leak detector

[0112] 33, the vacuum side of an optical fiber feedthrough equipped with four tubular members 10 as shown in Fig. 8 and passing four optical fiber strands 20 through it is connected to a vacuum pipe, and this vacuum pipe is connected to a vacuum exhaust pump via a valve. A leak detector is also connected to the vacuum pipe, and the amount of leakage was measured and compared when the atmosphere side (dotted line portion) of the optical fiber feedthrough was filled with air (BG) and when it was filled with helium.

[0113] Specifically, the valve was opened and evacuation was performed using a vacuum pump. After a sufficient degree of vacuum was reached, the valve was closed and measurements were performed using a leak detector.

[0114] Figure 34 shows the change in the amount of leakage over time. The moment the valve was closed was set as the starting time, and the amount of leakage was measured with a leak detector for 10 minutes thereafter.

[0115] In FIG. 34, the circles indicate the amount of leakage when helium is used, and the squares indicate the amount of leakage when air is used (background measurement).

[0116] As can be seen from Figure 34, the maximum amount of helium leakage is 5.4 × 10 -10 Pam 3 / s, which was almost the same as the background.

[0117] This shows that the optical fiber feedthrough according to this embodiment provides sufficient airtight sealing.

[0118] 2) Evaluation of the cooling performance of a refrigerator using optical fiber feedthrough An optical fiber feedthrough as shown in Figure 8 was actually connected to a refrigerator, and an experiment was conducted to see if it could be cooled down to the minimum temperature (10 mK or less) specified by the refrigerator.

[0119] More specifically, an optical fiber feedthrough as shown in Figure 8 was connected to the vacuum port of the cryogen-free dilution refrigerator. The optical fiber was thermally connected to the first and second temperature stage plates of the pulse tube (PT), and was then fixed on the stage of the mixing chamber, which ultimately reached the lowest temperature. The refrigerator was then evacuated and cooling was initiated.

[0120] Figure 35 shows the temperature change over time, with the two-dot chain line representing the temperature change over time in the first stage of PT, the dotted line representing the temperature change over time in the second stage of PT, and the solid line representing the temperature change over time in the mixing chamber. As shown, the lowest temperature reached in the mixing chamber was 6.7 mK.

[0121] Thus, it was found that the optical fiber feedthrough functioned as a light source to transmit light into a low-temperature environment in a vacuum without impairing the performance of the refrigerator.

[0122] Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. In particular, parts that need to be changed depending on the device to which the optical fiber feedthrough is connected are not limited to the shapes shown in the drawings, and other shapes may be adopted. Furthermore, specific features in the above-described embodiments may be arbitrarily selected or omitted depending on the purpose.

[0123] The above-described embodiment can be summarized as follows.

[0124] The optical fiber feedthrough according to this embodiment includes (A) a flange, (B) a tubular member that passes through the flange and is fixed with a first sealing material, and (C) an optical fiber that is passed through a through hole in the tubular member. The through hole in the tubular member has a first section, a second section, and a third section from one end of the tubular member, and the diameter of the first section is larger than the diameter of the second section and is matched to the coating of the optical fiber in the first section. The diameter of the second section is matched to the coating of the optical fiber in the second section, and the optical fiber in the third section is directly fixed in the through hole with the second sealing material.

[0125] The optical fiber is fixed directly by the second sealing material in the third section, so it is less susceptible to stress, and the provision of the second section in addition to the first section ensures that the optical fiber is stably held within the through-hole of the tubular member, reducing stress on the optical fiber and suppressing optical loss. In addition, the effect of bending the optical fiber outside the tubular member is less likely to be transmitted to the second sealing material, which helps maintain airtightness with the second sealing material.

[0126] It is preferable that the optical fiber extending outward from one end of the tubular member is covered with the same coating as that in the first section, in order to protect the optical fiber.

[0127] It is also preferable that the outermost coating of the optical fiber in the first section is black, since one end of the tubular member is assumed to be placed in air, and this is to prevent stray light from lighting or the like from entering.

[0128] Furthermore, the feedthrough may include a plurality of tubular members, preferably extending parallel to one another through the flange and secured with the first sealing material, allowing for the use of multiple optical fibers.

[0129] Furthermore, the flange described above may have a holding portion that has a hole through which the tubular member passes and that includes a recess into which the first sealing material is filled. With such a structure, it becomes easier to mount many tubular members.

[0130] Furthermore, a portion of the tubular member corresponding to the third section or a hole for injecting the second sealant provided in that portion may be provided on the side of the flange from which the other end of the tubular member protrudes (e.g., the vacuum side). While Figure 2 and other figures show an example in which the entire third section is provided on the vacuum side, a portion of the third section may be disposed inside the flange. This allows the length of one end of the tubular member to be shortened.

[0131] Furthermore, the optical fiber may be a single optical fiber strand or a wire in which a plurality of optical fiber strands are integrated (for example, a multi-core ribbon-type optical fiber core wire). Due to the structure of the tubular member, various optical fibers can be used.

[0132] The feedthrough described above may further include a strain relief. In this case, the through hole of the tubular member may further include a fourth section on the other end side of the tubular member, the diameter of the fourth section being the same as that of the first section and aligned with the coating of the optical fiber in the fourth section, and a strain relief may be attached to the other end of the tubular member. This provides increased protection at the other end of the tubular member as well.

[0133] Furthermore, the thickness of the tubular member may be formed to taper from the one end to the other end at the portion where the tubular member passes through the fringe, in order to prevent the tubular member from being pulled in from one end to the other end. [Explanation of symbols]

[0134] 10,100 Tubular member 20 Optical fiber wire 200 optical fiber core 30, 40, 50, 300, 400, 500 flange

Claims

1. A flange and a tubular member that passes through the flange and is secured by a first seal; an optical fiber passed through a through hole of the tubular member; and the through hole of the tubular member has a first section, a second section, and a third section from one end of the tubular member, a diameter of the first section being larger than a diameter of the second section and adapted to fit a coating of the optical fiber in the first section; a diameter of the second section that is adapted to fit the coating of the optical fiber in the second section; In the third section, the optical fiber is directly fixed in the through hole with a second sealing material. Fiber optic feedthrough.

2. The optical fiber extending outward from one end of the tubular member has the same coating as that in the first section. The feedthrough of claim 1 .

3. The outermost coating of the optical fiber in the first section is black. The feedthrough structure of claim 1 .

4. a plurality of the tubular members; A plurality of the tubular members extend parallel to one another through the flange and are fixed with the first sealing material. The feedthrough of claim 1 .

5. The flange has a holding portion provided with a hole through which the tubular member passes and including a recess into which the first sealing material is filled. The feedthrough of claim 1 .

6. On the side of the flange from which the other end of the tubular member emerges, The tubular member has a hole for injecting the second sealing material, the hole being provided in a portion corresponding to the third section or the portion. The feedthrough of claim 1 .

7. The optical fiber is a single optical fiber strand or a wire in which a plurality of optical fiber strands are integrated. The feedthrough of claim 1 .

8. Further having a strain relief, the through hole of the tubular member further has the fourth section on the other end side of the tubular member, the diameter of the fourth section is the same as the diameter of the first section and is adapted to fit the coating of the optical fiber in the fourth section; The strain relief is attached to the other end of the tubular member. The feedthrough of claim 1 .

9. The tubular member is formed so that the thickness of the tubular member becomes thinner from the one end side to the other end side at the portion where the tubular member passes through the fringe. The feedthrough of claim 1 .

Images