A sealed optical fiber ring assembly and its manufacturing and leak detection method

Abstract

The present invention relates to a sealed optical fiber ring assembly and a method for making and leaking the same, aiming to solve the problem of low sealing of optical fiber rings in the prior art. The present invention provides a sealed optical fiber ring assembly, wherein the optical fiber ring is installed in an annular sealed cavity formed by an annular cover plate and an optical fiber ring skeleton, the pigtail of the optical fiber ring extends into a protective sleeve and is led out through a fiber passage, and the gaps between the pigtail and the protective sleeve, between the protective sleeve and the annular cover plate, and between the protective sleeve and the inner tube of the skeleton are filled with sealant; thereby, the sealing of the optical fiber ring is achieved; the present invention also provides a method for making a sealed optical fiber ring assembly and a method for leaking the sealed optical fiber ring assembly, which effectively improve the sealing of the optical fiber ring, thereby improving the environmental adaptability and long-term repeatability of the optical fiber gyroscope.

Description

Technical Field

[0001] The invention relates to the sealing of an optical fiber ring, and in particular to a sealing optical fiber ring component and a manufacturing and leakage detection method thereof. Background Art

[0002] Fiber optic gyroscopes have the advantages of impact resistance, high sensitivity, long life, large dynamic range, and short start-up time, and have been widely used in inertial navigation systems.

[0003] High-precision fiber optic gyroscopes are usually composed of a combination of fiber optic ring modules, digital demodulation circuits, ASE light sources, 1×3 couplers, and P IN-FET components. The fiber optic ring module includes a fiber optic ring. The fiber optic ring is the core component of the fiber optic gyroscope, which is used to sense the Sagnac phase difference between two counter-propagating light waves caused by the input angular velocity. Changes in air pressure, water vapor, and salt spray in the external environment will affect the performance of the fiber optic ring, and thus affect the accuracy, reliability, and long-term stability of the fiber optic gyroscope.

[0004] Therefore, the sealing of the fiber optic ring is particularly important. The sealing performance of the traditional fiber optic ring mainly depends on the sealing performance of the fiber optic inertial group. The fiber optic inertial group usually adopts a static sealing structure with an O-ring sealing rubber strip. However, due to the complex structure, multiple external interfaces and large size of the fiber optic inertial group, it is difficult to achieve good airtightness. Therefore, the fiber optic ring cannot be well sealed, which in turn affects the environmental adaptability and long-term repeatability of the fiber optic gyroscope. Summary of the invention

[0005] The present invention aims to solve the problem of low sealing performance of optical fiber rings in the prior art, and provides a sealed optical fiber ring component and a manufacturing and leak detection method thereof.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The sealed optical fiber ring assembly of the present invention is special in that it comprises an optical fiber ring frame, an annular cover plate, a protective sleeve and an optical fiber ring;

[0008] The optical fiber ring frame comprises a frame inner tube, a frame outer tube and an annular bottom plate;

[0009] The frame inner tube and the frame outer tube are coaxially arranged, and an annular cover plate is installed at one end of both, and an annular bottom plate is installed at the other end; thus an annular sealing cavity is formed between the frame inner tube, the frame outer tube, the annular cover plate and the annular bottom plate;

[0010] The wall of the inner tube of the skeleton is provided with a fiber passage which connects the annular sealing cavity with the outside;

[0011] The optical fiber ring is installed in the annular sealed cavity, and the pigtail of the optical fiber ring is covered with a protective sleeve and led out from the fiber passage;

[0012] The gaps between the pigtail and the protective sleeve, between the protective sleeve and the annular cover plate, and between the protective sleeve and the framework inner tube are all filled with sealant.

[0013] Furthermore, the sealant includes silicone rubber, light-curing glue and epoxy glue;

[0014] The silicone rubber is filled in the opening on one side where the fiber passage communicates with the annular sealing cavity;

[0015] The optical curing glue is filled in the gap between the pigtail and the protective sleeve;

[0016] The epoxy glue is filled in the gap between the protective sleeve and the annular cover plate and the inner tube of the framework, and is also filled in the two arc-shaped gaps between the annular cover plate and the inner tube of the framework. The two arc-shaped gaps are distributed on both sides of the fiber passage.

[0017] Furthermore, the optical fiber ring is bonded in the annular sealing cavity by epoxy glue.

[0018] Furthermore, an annular folded edge bent toward the center is provided at one end of the skeleton inner tube close to the annular cover plate, and an annular notch matched with the inner side of the annular cover plate is provided at the bending position;

[0019] The fiber passage is provided on the annular folded edge;

[0020] At least three mounting holes are evenly arranged on the annular folded edge along its circumference.

[0021] Furthermore, the annular cover plate and the outer tube of the framework are laser welded;

[0022] The gaps between the annular cover plate and the annular notch other than the arc-shaped gap are laser welded.

[0023] Furthermore, the skeleton inner tube, the skeleton outer tube and the annular bottom plate are an integrated structure.

[0024] Based on the above-mentioned sealed optical fiber ring assembly, the present invention further provides a method for manufacturing a sealed optical fiber ring assembly, which is special in that it is implemented in the following steps:

[0025] Step 1) insert the pigtail of the optical fiber ring into the protective sleeve, and inject optical curing glue into the protective sleeve;

[0026] Step 2) bonding the optical fiber ring to the optical fiber ring frame by epoxy glue, and taking out the pigtail with the protective sleeve from the fiber passage;

[0027] Step 3) Laser welding the outer side of the annular cover plate to the outer tube of the frame, laser welding the inner side of the annular cover plate to the annular notch, and reserving an arc gap on both sides of the fiber passage;

[0028] Step 4) sealing a side opening of the fiber passage communicating with the annular sealing cavity by coating with silicone rubber;

[0029] Step 5) Epoxy glue is applied in the gap between the protective sleeve and the annular cover plate and the inner tube of the framework, and epoxy glue is applied in the two arc-shaped gaps between the inner side of the annular cover plate and the annular notch.

[0030] Based on the above-mentioned sealed optical fiber ring assembly and its manufacturing method, the present invention also provides a leak detection method for a sealed optical fiber ring assembly, which is special in that it is implemented in accordance with the following steps:

[0031] Step 1), manufacturing the sealed optical fiber ring assembly by the above-mentioned method for manufacturing the sealed optical fiber ring assembly;

[0032] Step 2), placing the prepared sealed optical fiber ring assembly into a vacuum pressure box;

[0033] Step 3), evacuate the vacuum pressure box and keep it for 0.5h to 2h;

[0034] Step 4), filling the vacuum pressure box with high-pressure helium and maintaining the pressure for 0.5h to 2h;

[0035] Step 5), take out the sealed optical fiber ring assembly and let it stand in the air for 4 hours to 8 hours;

[0036] Step 6), placing the sealed optical fiber ring assembly into a leak detection box;

[0037] Step 7), using a helium mass spectrometer leak detector to evacuate the leak detection box and perform a leak rate test;

[0038] If the leakage rate is qualified, the sealed optical fiber ring assembly is qualified;

[0039] If the leakage rate is unqualified, reseal the sealed optical fiber ring assembly and repeat steps 1) to 7) until the leakage rate is qualified.

[0040] Furthermore, in the step 3), after the vacuum pressure box is evacuated, the vacuum is maintained for 1 hour;

[0041] The pressure holding time in step 4) is 1 hour.

[0042] The beneficial effects of the present invention are:

[0043] 1. The present invention installs the optical fiber ring in an annular sealed cavity formed by an annular cover plate and an optical fiber ring skeleton, the pigtail of the optical fiber ring extends into a protective sleeve and is led out through a fiber passage, and sealant is filled in the gaps between the pigtail and the protective sleeve, between the protective sleeve and the annular cover plate, and between the protective sleeve and the inner tube of the skeleton; thereby, the sealing of the optical fiber ring is achieved; further, the optical fiber ring in the optical fiber ring module is individually sealed to prevent the performance of the optical fiber ring from being affected by changes in air pressure, water vapor, salt spray, etc. in the external environment, which can effectively improve the sealing of the optical fiber ring, thereby improving the environmental adaptability and long-term repeatability of the optical fiber gyroscope.

[0044] 2. The present invention uses three kinds of sealants: photocurable sealant fills the protective sleeve, and silicone rubber is not easy to flow and is a flexible material. Therefore, the silicone rubber can protect the protective sleeve on the one hand, and on the other hand, it can block the connecting port between the fiber channel and the annular sealing cavity to prevent the easily flowing epoxy glue from flowing into the annular sealing cavity and affecting the performance of the optical fiber ring; and because the epoxy glue has good adhesion, finally the epoxy glue is used to bond and seal other gaps, which can effectively improve the sealing of the optical fiber ring module.

[0045] 3. In the present invention, the optical fiber ring is bonded in the annular sealed cavity by epoxy adhesive, so that the optical fiber ring is reliably fixed in the sealed cavity.

[0046] 4. The present invention provides an annular folded edge bent toward the center at one end of the skeleton inner tube, and opens a fiber passage on the annular folded edge. On the one hand, the annular folded edge can increase the strength of the skeleton inner tube; on the other hand, the fiber passage is opened on the annular folded edge, so that the pigtail with a protective sleeve in the fiber passage is more stable; on the third hand, a mounting hole is provided on the annular folded edge, so that the entire optical fiber ring assembly is more conveniently connected to the external platform.

[0047] 5. In the present invention, the annular cover plate and the optical fiber ring frame are all laser welded except for the two arc-shaped gaps on both sides of the fiber channel. Laser welding makes the connection and sealing between the annular cover plate and the optical fiber ring frame more reliable; two arc-shaped gaps are reserved during welding, thereby avoiding laser damage to the optical fiber.

[0048] 6. The present invention adopts a helium mass spectrometry back pressure leak detection method to perform a leak test on a separately arranged sealed optical fiber ring assembly. The sealed optical fiber ring assembly pressurized with helium is placed in a leak detection box, vacuumed, and a leak rate test is performed until the leak rate is qualified. The method is simple and easy to implement, and can improve the reliability of the sealed optical fiber ring assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 is a structural schematic diagram of a sealed optical fiber ring assembly of this embodiment;

[0050] Figure 2 is a schematic structural diagram of a sealed optical fiber ring assembly without an optical fiber ring installed in this embodiment;

[0051] Figure 3 yes Figure 2 The enlarged view of point A in the middle;

[0052] Figure 4 is a schematic structural diagram of the annular cover plate in this embodiment;

[0053] Figure 5 is a schematic diagram of the structure of the optical fiber ring in this embodiment;

[0054] Figure 6 Schematic diagram of the structure of the protective sleeve in this embodiment;

[0055] Figure 7 is a schematic diagram of the assembly process of the sealed optical fiber ring assembly in this embodiment;

[0056] Figure 8 It is a flow chart of a leak detection method for a sealed optical fiber ring assembly in this embodiment.

[0057] In the figure, 1-optical fiber ring skeleton, 11-skeleton inner tube, 12-skeleton outer tube, 13-annular bottom plate, 14-annular folded edge, 141-annular notch, 16-mounting hole, 2-annular cover plate, 3-protective sleeve, 4-optical fiber ring, 41-pigtail, 5-annular sealing cavity, 51-epoxy glue, 6-fiber passage. DETAILED DESCRIPTION

[0058] In order to make the purpose, advantages and features of the present invention clearer, the following is a further detailed description of a sealed optical fiber ring assembly and a leak detection method proposed by the present invention in combination with the accompanying drawings and specific embodiments. According to the following specific implementation methods, the advantages and features of the present invention will be clearer. It should be noted that: the drawings are all in a very simplified form and are not in precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention; secondly, the structure shown in the drawings is often a part of the actual structure.

[0059] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0060] Combination Figure 1 to Figure 6 As shown, a sealed optical fiber ring assembly of this embodiment includes an optical fiber ring frame 1, an annular cover plate 2, a protective sleeve 3 and an optical fiber ring 4;

[0061] The optical fiber ring frame 1 comprises a frame inner tube 11, a frame outer tube 12 and an annular bottom plate 13; the annular bottom plate 13 is arranged at one end of the frame inner tube 11 and the frame outer tube 12 to form a U-shaped groove, and the frame inner tube 11, the frame outer tube 12 and the annular bottom plate 13 are an integrated structure;

[0062] The other end of the skeleton inner tube 11 is provided with an annular folded edge 14 bent toward its center, and an annular notch 141 adapted to the inner side of the annular cover plate 2 is provided at the bending part; a fiber passage 6 is provided on the annular folded edge 14; three mounting holes 16 are evenly arranged along the circumference of the annular folded edge 14 for connecting with the external platform.

[0063] The inner side of the annular cover plate 2 and the annular notch 141 are laser welded, and two arc-shaped gaps on both sides of the fiber channel 6 are reserved without welding to avoid damaging the optical fiber; the outer side of the annular cover plate 2 is laser welded to the other end of the outer tube 12 of the framework; thereby, an annular sealed cavity 5 is formed between the annular cover plate 2 and the optical fiber ring framework 1; the fiber channel 6 makes the annular sealed cavity 5 and the outside pass through; the optical fiber ring 4 is bonded to the annular sealed cavity 5 by epoxy glue 51, and the pigtail 41 of the optical fiber ring 4 is covered with a protective sleeve 3 and led out from the fiber channel 6; the gap between the pigtail 41 and the protective sleeve 3 is filled with optical glue; the side opening of the fiber channel 6 communicating with the annular sealed cavity 5 is filled with silicone rubber, and the epoxy glue 51 is filled in the gap between the protective sleeve 3 and the annular cover plate 2 and the inner tube 11 of the framework, and is filled in the two arc-shaped gaps between the annular cover plate 2 and the inner tube 11 of the framework. Thus, the sealing of the optical fiber ring is achieved.

[0064] like Figure 7 As shown, the specific assembly steps of a sealed optical fiber ring assembly of this embodiment are:

[0065] Step 1) passing the pigtail 41 of the optical fiber ring 4 through the protective sleeve 3, and injecting light-curing glue into the protective sleeve 3 to cure and seal;

[0066] Step 2) bonding the optical fiber ring 4 to the annular bottom plate 13 of the optical fiber ring frame 1 by epoxy glue, and taking out the pigtail 41 with the protective sleeve 3 from the fiber passage 6;

[0067] Step 3) Cover the opening of the optical fiber ring frame 1 with the annular cover plate 2, and the outer side of the annular cover plate 2 and the outer tube 12 of the frame are completely welded by laser welding, and the gap between the inner side of the annular cover plate 2 and the annular notch 141 except the arc-shaped gaps on both sides of the fiber channel 6 is also welded by laser welding;

[0068] Step 4) coating the fiber passage 6 with silicone rubber, and sealing the communication port between the fiber passage 6 and the annular sealing cavity 5 with the silicone rubber;

[0069] Step 5) Epoxy glue is applied in the gap between the protective sleeve 3 and the annular cover plate 2 and the skeleton inner tube 11 , and epoxy glue is applied in the two arc-shaped gaps between the inner side of the annular cover plate 2 and the annular notch 141 .

[0070] A leak detection method for a sealed optical fiber ring assembly of this embodiment uses a helium mass spectrometer back pressure leak detection method to detect leaks in the optical fiber ring sealing structure; Figure 8As shown, the specific steps are as follows:

[0071] First, put the above-mentioned sealed optical fiber ring assembly into a vacuum pressure box, evacuate the vacuum pressure box, and keep it for 1 hour after evacuation; then fill the vacuum pressure box with high-pressure helium under vacuum conditions. If there are leaks in the welds or glue injection and coating positions between the optical fiber ring skeleton and the cover plate, helium will enter the annular sealed cavity formed by the optical fiber ring skeleton and the annular cover plate through the leaks; after maintaining the pressure for 1 hour, take the sealed optical fiber ring assembly out of the vacuum pressure box and let it stand in the air for 5 to 6 hours until all the helium on the outer surface of the sealed optical fiber ring assembly has dissipated and there is no helium on the outer surface; then put the sealed optical fiber ring assembly that has been pressurized with helium into a leak detection box, evacuate the leak detection box using a helium mass spectrometer leak detector, and perform a leak rate test.

[0072] If the leakage rate meets the design requirements, the sealing performance of the sealed optical fiber ring assembly is good; if the leakage rate does not meet the design requirements, recheck the laser welding welds and the injection and coating positions, re-inject and re-seal the leak holes or the positions where leak holes may exist, and repeat the leak detection method after sealing until the leakage rate meets the design requirements.

Claims

1. A sealed optical fiber ring assembly, characterized in that: It comprises an optical fiber ring frame (1), an annular cover plate (2), a protective sleeve (3) and an optical fiber ring (4); The optical fiber ring frame (1) comprises a frame inner cylinder (11), a frame outer cylinder (12) and an annular bottom plate (13); The skeleton inner cylinder (11) and the skeleton outer cylinder (12) are coaxially arranged, and an annular cover plate (2) is installed at one end of both, and an annular bottom plate (13) is installed at the other end; thereby an annular sealing cavity (5) is formed between the skeleton inner cylinder (11), the skeleton outer cylinder (12), the annular cover plate (2) and the annular bottom plate (13); The wall of the inner tube (11) of the skeleton is provided with a fiber passage (6) which connects the annular sealing cavity (5) with the outside; The optical fiber ring (4) is installed in an annular sealed cavity (5), and a protective sleeve (3) is sleeved on the pigtail (41) of the optical fiber ring (4) and led out from the fiber passage (6); The gaps between the pigtail (41) and the protective sleeve (3), between the protective sleeve (3) and the annular cover plate (2), and between the protective sleeve (3) and the skeleton inner tube (11) are all filled with sealant; The sealant includes silicone rubber, light curing glue and epoxy glue (51); The silicone rubber is filled in a side opening where the fiber passage (6) communicates with the annular sealing cavity (5); The optical curing glue is filled in the gap between the pigtail (41) and the protective sleeve (3); The epoxy glue (51) is filled in the gap between the protective sleeve (3) and the annular cover plate (2) and the skeleton inner tube (11), and is also filled in the two arc-shaped gaps between the annular cover plate (2) and the skeleton inner tube (11), and the two arc-shaped gaps are distributed on both sides of the fiber passage (6).

2. A sealed optical fiber ring assembly according to claim 1, characterized in that: The optical fiber ring (4) is bonded to the annular sealing cavity (5) by epoxy glue (51).

3. A sealed optical fiber ring assembly according to claim 1 or 2, characterized in that: An annular folded edge (14) bent toward the center of the skeleton inner tube (11) is provided at one end close to the annular cover plate (2), and an annular notch (141) adapted to the inner side of the annular cover plate (2) is provided at the bending portion; The fiber passage (6) is provided on the annular folded edge (14); At least three mounting holes (16) are evenly arranged on the annular folded edge (14) along its circumference.

4. A sealed optical fiber ring assembly according to claim 3, characterized in that: The annular cover plate (2) and the skeleton outer cylinder (12) are laser welded; The gaps between the annular cover plate (2) and the annular notch (141), except for the arc-shaped gap, are laser welded.

5. A sealed optical fiber ring assembly according to claim 4, characterized in that: The skeleton inner cylinder (11), the skeleton outer cylinder (12) and the annular bottom plate (13) are an integrated structure.

6. A method for manufacturing the sealed optical fiber ring assembly according to any one of claims 1 to 5, characterized in that: Follow the steps below to implement it: Step 1) inserting the pigtail (41) of the optical fiber ring (4) into the protective sleeve (3), and injecting optical curing glue into the protective sleeve (3); Step 2) bonding the optical fiber ring (4) to the optical fiber ring frame (1) by epoxy adhesive, and taking out the pigtail (41) with the protective sleeve (3) from the fiber passage (6); Step 3) laser welding the outer side of the annular cover plate (2) to the outer tube of the framework (12), laser welding the inner side of the annular cover plate (2) to the annular notch (141), and reserving an arc gap on both sides of the fiber passage (6); Step 4) sealing a side opening of the fiber passage (6) communicating with the annular sealing cavity (5) by coating with silicone rubber; Step 5) Epoxy glue is applied in the gap between the protective sleeve (3) and the annular cover plate (2) and the skeleton inner tube (11), and epoxy glue is applied in the two arc-shaped gaps between the inner side of the annular cover plate (2) and the annular notch (141).

7. A leak detection method for a sealed optical fiber ring assembly according to any one of claims 1 to 5, characterized in that: Follow the steps below to implement it: Step 1), manufacturing the sealed optical fiber ring assembly as claimed in any one of claims 1 to 5 by the method as claimed in claim 6; Step 2), placing the prepared sealed optical fiber ring assembly into a vacuum pressure box; Step 3), evacuate the vacuum pressure box and keep it for 0.5h to 2h; Step 4), filling the vacuum pressure box with high-pressure helium and maintaining the pressure for 0.5h to 2h; Step 5), take out the sealed optical fiber ring assembly and let it stand in the air for 4 hours to 8 hours; Step 6), placing the sealed optical fiber ring assembly into a leak detection box; Step 7), using a helium mass spectrometer leak detector to evacuate the leak detection box and perform a leak rate test; If the leakage rate is qualified, the sealed optical fiber ring assembly is qualified; If the leakage rate is unqualified, reseal the sealed optical fiber ring assembly and repeat steps 1) to 7) until the leakage rate is qualified.

8. A leak detection method for a sealed optical fiber ring assembly according to claim 7, characterized in that: After the vacuum pressure box is evacuated in step 3), the vacuum is maintained for 1 hour; The pressure holding time in step 4) is 1 hour.

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