Optical fiber device, method for manufacturing optical fiber device, and aircraft

Abstract

A rugged sealed fiber optic connector (12) and a method for manufacturing such a durable and sealed fiber optic connector. The sealed fiber optic connector is epoxy-free and achieves sealing through a series of high temperature soldering steps with appropriate soldering temperature levels. The design of the sealed fiber optic connector is universal for both glass fiber and plastic fiber connections. In addition, the universal sealed fiber optic connector is ruggedized to withstand harsh avionics environments without causing fiber damage within the connector.

Description

Technical Field

[0001] The present disclosure relates generally to the design and manufacture of fiber optic connectors. In particular, the present disclosure relates to sealed fiber optic connectors for use with fiber optic sensors used to measure the level of a liquid in a reservoir, such as the level of fuel in a fuel tank of an aircraft. Background Art

[0002] Known systems for detecting the level of fuel in a fuel tank or compartment using an optical sensor system. In some embodiments, the optical sensor system includes an optical fiber installed in the fuel tank and includes a light source (e.g., a laser) and an optical detector (e.g., a photodetector) located outside the fuel tank. In a proposed embodiment, light from an external light source is received by a side-emitting optical fiber in the fuel tank via an optical fiber connector installed in an opening in the wall of the fuel tank. Similarly, light from a pair of side-receiving optical fibers in the fuel tank is received by an external optical detector via corresponding optical fiber connectors. The optical detector converts the optical data carried by the light from the side-receiving optical fiber into electrical signals. These electrical signals are transmitted to a computer system (also located outside the fuel tank). For example, the computer system can be a part of a flight control system or a computer located on an aircraft. The computer system can be configured to estimate the amount or level of fuel present in the fuel tank or its compartment based on the data carried by the light propagated through the optical fiber connector.

[0003] As used herein, the term "fiber optic connector" refers to a connector that optically couples optical fibers to each other. The main function of a fiber optic connector is to hold the terminal portion of the optical fiber so that the core of the optical fiber is axially aligned with the optical path of the optical fiber assembly to which the connector matches, for example, so that the light from one optical fiber is optically coupled to another optical fiber. Some fiber optic connectors are designed to match the terminal portion of one optical fiber with the terminal portion of another optical fiber. In order to minimize Fresnel loss, the terminals of the respective optical fibers should be in physical contact. Typically, an optical connector includes a "ferrule", which is a component for holding one or more optical fibers in physical contact so that the ends of the optical fibers are optically coupled. As used herein, the term "ferrule" refers to an elongated body having an axial hole segment configured to support an optical fiber segment.

[0004] In situations where a fiber optic connector passes through the wall of a fuel tank, the fiber optic connector must be hermetically sealed to prevent fuel vapor or liquid from leaking out at the interface of the fiber optic connector and the opening in which the connector is mounted. A known sealed fiber optic connector designed for connecting a glass optical fiber (GOF) fuel level sensor to a GOF may suffer fiber damage within the sealed connector. An existing design uses an epoxy or glass sealing process to achieve sealing, which cannot withstand extensive temperature cycling and / or high vibration environments. In addition, a typical sealed connector based on the prior art requires replacement of the entire connector on the fuel tank wall if the fiber terminal is damaged. Another consideration in the design of a sealed fiber optic connector is that a new generation of plastic optical fiber (POF) fuel level sensors will eventually replace GOF fuel level sensors in the future.

[0005] It would be desirable to provide a sealed fiber optic connector that is not susceptible to damage to the fiber or loss of sealability and that can be used universally with both GOF and POF fuel level sensors. Summary of the invention

[0006] The subject matter disclosed in more detail below relates to a sealed fiber optic connector and a method for manufacturing such a fiber optic connector that is both durable and sealed. The manufacturing process is epoxy-free, eliminating the effects of stress from the epoxy that may cause fiber breakage and loss of sealing due to epoxy delamination. The sealed fiber optic connector disclosed herein uses a high-reliability fiber welding process to achieve sealing that can withstand harsh aerospace environments such as a large number of temperature cycles and high vibration environments. More specifically, the sealing of the fiber optic connector is achieved through a series of high-temperature welding steps with appropriate welding temperature levels. Successive welding steps use a series of different solder materials with a reduced melting temperature, thereby ensuring that during the process of manufacturing the partition assembly, the heating process involved in the subsequent welding steps will not adversely affect the solder used in the previous welding steps. The sealing of the connector does not rely on the seal at the terminal inserted into the connector. If the terminal is damaged, there is no need to replace or replace the connector itself on the fuel tank wall; instead, the connection can be repaired by replacing or re-terminating. Compared with replacing the sealed connector on the fuel tank wall, this solution saves time and labor. Furthermore, the design of the sealed optical fiber connector proposed herein is universal for both glass optical fiber (GOF) connections and plastic optical fiber (POF) connections.

[0007] Although an example fiber optic connector suitable for an aircraft fuel tank fiber optic sensor application will be described in detail, the concepts disclosed herein are equally applicable to systems and methods for measuring liquid levels in a reservoir such as a storage tank or other container using an optical sensor. In many commercial and military applications, the level of a liquid is continuously measured. For example, liquid level sensors are commonly used in fuel tanks of aircraft, automobiles, and trucks. Liquid level sensors are also used to monitor liquid levels in storage tanks for fuel distribution, wastewater treatment, chemical storage, food processing, etc.

[0008] As used herein, the term "welding" refers to a process of joining two or more items together by melting a filler metal (solder) at the interface between the facing items, the filler metal having a melting point lower than the melting points of the adjacent metals. According to one embodiment of the welding system disclosed herein, a first solder material including gold and tin (hereinafter "gold / tin solder") has a first melting temperature, a second solder material including silver and tin (hereinafter "silver / tin solder") has a second melting temperature less than the first melting temperature, and a third solder material including lead and tin (hereinafter "lead / tin solder") has a third melting temperature less than the second melting temperature. These solders are used in successive stages during a process of manufacturing a baffle assembly suitable for sealing an opening installed in a wall of a reservoir such as a fuel tank.

[0009] Although various embodiments of fiber optic devices (eg, fiber optic connectors) and methods for making fiber optic devices will be described in detail below, one or more of those embodiments may be characterized by one or more of the following aspects.

[0010] One aspect of the subject matter disclosed in detail below is an optical fiber device, the optical fiber device comprising: a ferrule, made of a ceramic material (e.g., zirconia) and having a hole along a central axis, the hole comprising a first cavity and a second cavity at opposite ends of the ferrule and a precision micro-hole section connecting the first cavity and the second cavity, wherein the micro-hole section is coaxial with the first cavity and the second cavity; a first metal layer, on a surface of the first cavity; a second metal layer, on a surface of the second cavity; a first solder ring, disposed in the first cavity and having an opening; a second solder ring, disposed in the second cavity and having an opening; a coated optical fiber ferrule, coated with a metal layer, a first portion of the coated optical fiber ferrule disposed in the opening of the first solder ring, a second portion of the coated optical fiber ferrule disposed in the micro-hole section of the ferrule, and a third portion of the coated optical fiber ferrule disposed in the opening of the second solder ring, wherein the first solder ring and the second solder ring are made of a first solder material having a first melting temperature. The first portion of the coated optical fiber ferrule is bonded to the first cavity by fusion of the first solder ring and the first metal layer on the surface of the first cavity; the second portion of the coated optical fiber ferrule is bonded to the second cavity by fusion of the second solder ring and the second metal layer on the surface of the second cavity. The optical fiber device also includes a metallization on the central region of the outer surface of the ferrule and a second solder material layer applied on the metallization, wherein the second solder material has a second melting temperature lower than the first melting temperature. The regions of the ferrule on opposite sides of the central region are inserted into the first split sleeve and the second split sleeve, respectively. The optical fiber device also includes: an optical fiber alignment fixture (made of metal) bonded to the ferrule by the solder material layer; and a diaphragm fixture (made of metal) bonded to the optical fiber alignment fixture by a third solder ring and a fourth solder ring made of a third solder material, the third solder material having a third melting temperature less than the second melting temperature.

[0011] Another aspect of the subject matter disclosed in detail below is a method for manufacturing an optical fiber device, the method comprising: (a) coating the respective surfaces of the first cavity and the second cavity of a ferrule with metal, the ferrule being made of a ceramic material and having an axial hole including the first cavity and the second cavity and a micro-hole section connecting the first cavity and the second cavity; (b) coating an optical fiber ferrule with a metal layer to provide a coated optical fiber ferrule, the length of the optical fiber ferrule being greater than the length of the ferrule; (c) placing a central portion of the coated optical fiber ferrule within the micro-hole section, and respective end portions of the coated optical fiber ferrule protruding beyond the first end face and the second end face of the ferrule, respectively; (d) placing one end of the coated optical fiber ferrule in a micro-hole section having a first end face and a second end face of the ferrule; (e) placing the first solder ring in the first cavity; (f) placing the other end of the coated optical fiber ferrule in the opening of the second solder ring made of the first solder material; (g) placing the second solder ring in the second cavity; (h) soldering the coated optical fiber ferrule to the surface of the first cavity and the second cavity of the ferrule by heating the first solder ring and the second solder ring simultaneously to a temperature equal to or greater than the melting temperature of the first solder material; (i) metalizing a central area of ​​the outer surface of the ferrule; (j) applying a second solder material layer on the metalized central area, wherein the second solder material has a second melting temperature lower than the first melting temperature. temperature; (k) inserting one end of the ferrule into a portion of the first split sleeve and the other end of the ferrule into a portion of the second split sleeve to form a ferrule assembly; (l) placing the ferrule assembly in an opening in a middle portion of a hole of an optical fiber alignment fixture made of metal and having a first external annular protrusion; (m) welding the ferrule assembly in the optical fiber alignment fixture by heating the first external annular protrusion to a degree that the temperature of the second solder material layer is equal to or greater than the second melting temperature; (n) placing a third solder ring and a fourth solder ring made of a third solder material adjacent to the corresponding end faces of the first external annular protrusion of the optical fiber alignment fixture to form a ferrule assembly; (a) placing the first outer annular protrusion of the optical fiber alignment fixture and the third and fourth solder rings in the hole of a partition fixture made of metal and having a second outer annular protrusion and an outer flange, so that the corresponding end portions of the optical fiber alignment fixture protrude beyond the first end face and the second end face of the partition fixture respectively; (b) welding the optical fiber alignment fixture in the partition fixture by heating the second outer annular protrusion of the partition fixture to a degree that the temperature of the third and fourth solder rings is equal to or greater than the third melting temperature to form a partition assembly.

[0012] Another aspect of the subject matter disclosed in detail below is an aircraft, the aircraft comprising: a fuel tank having a wall with an opening; a bulkhead assembly sealingly mounted in the opening in the wall of the fuel tank; a first fiber optic cable disposed within the fuel tank and comprising a first terminal inserted into a first cavity at one end of the bulkhead assembly and a first optical fiber terminated within the first terminal; a second fiber optic cable disposed outside the fuel tank and comprising a second terminal inserted into a second cavity at the other end of the bulkhead assembly and a second optical fiber terminated within the second terminal. The bulkhead assembly comprises: a ferrule having a bore section; an optical fiber ferrule comprising a first portion disposed within the bore section of the ferrule, a first end face in contact with an end face of the first optical fiber, and a second end face in contact with an end face of the second optical fiber for optically coupling the first optical fiber to the second optical fiber.

[0013] According to one embodiment, the ferrule is made of a ceramic material and has a first cavity and a second cavity connected by a hole segment, and the first cavity and the second cavity have corresponding metal-plated surfaces; the partition assembly also includes a first solder ring arranged in the first cavity and a second solder ring arranged in the second cavity; the optical fiber ferrule also includes a second part coupled to the first cavity through the first solder ring and a third part coupled to the second cavity through the second solder ring.

[0014] Other aspects of fiber optic devices and methods for making fiber optic devices are disclosed and claimed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The features, functions, and advantages discussed in the preceding sections can be achieved independently in various embodiments or can be combined in other embodiments. To illustrate the above and other aspects, various embodiments will be described below with reference to the accompanying drawings.

[0016] Figures 1A to 1F are diagrams showing various side views of components of a ferrule assembly during successive stages of a universal sealed connector manufacturing process according to one embodiment.

[0017] FIG. 2A to FIG. 2F It shows that Figures 1A to 1F A diagram of the internal features of the component depicted in FIG. Figure 2A , Figure 2E and Figure 2F is a cross-sectional view; Figure 2B-Figure 2D It is a side view.

[0018] FIG. 3A to FIG. 3F It means respectively in Figures 1A to 1F FIG. 1 is a perspective view of the components depicted in FIG.

[0019] Figure 4A It means in Figure 1A-1F FIG. 5 is a diagram of a perspective view of a ferrule assembly prior to insertion into a fiber alignment fixture during a universal sealing connector manufacturing process as partially depicted in FIG.

[0020] Figure 4B Is indicated in the ferrule assembly (in Figure 1F , Figure 2F and Figure 3F ) is a diagram of a perspective view of a fiber optic alignment fixture during welding within the fiber optic alignment fixture, wherein the welding operation is performed Figure 1A-1F and Figure 4A Another step in the universal sealed connector manufacturing process is partially depicted in FIG.

[0021] Figure 5 It means in Figure 4B FIG. 4 is a diagram of a perspective view of a pair of solder rings after a soldering step, not yet placed in an annular recess formed in an annular protrusion of a fiber alignment fixture.

[0022] Fig. 6A It means that the optical fiber alignment fixture is inserted into the spacer fixture with a flange before the optical fiber alignment fixture is inserted into the spacer fixture with a flange. Figure 5 A side view of a fiber optic alignment fixture with a corresponding solder ring is depicted in FIG, wherein the insert is in Figure 1A-1F , Figure 4A , Figure 4B and Figure 5 Another step in the universal sealed connector manufacturing process is partially depicted in FIG.

[0023] Figure 6B It indicates that the fiber alignment fixture is inserted into Fig. 6A FIG. 1 is a diagram of a partial cross-sectional view of a baffle fixing device depicted in FIG. 1 to form a baffle assembly suitable for installation in an opening in a fuel tank wall.

[0024] Figure 7 is a diagram showing a partial cross-sectional view of an optical fiber alignment fixture coupled to a bulkhead fixture during a welding operation, wherein the welding operation is performed Figure 1A-1F , Figure 4A , Figure 4B , Figure 5 and Fig. 6A Another step in the universal sealed connector manufacturing process is partially depicted in FIG.

[0025] Figure 8 is a hybrid diagram showing a partially exploded view of the components of a universal sealed fiber optic connector prior to installation in an opening in a fuel tank wall, wherein the components include a welded rear bulkhead assembly, two silicone rubber gaskets and an outer mounting flange shown in cross-section.

[0026] Fig. 9 is a diagram showing a perspective cross-sectional view of the installed universal sealed fiber optic connector after the terminal retention clip is inserted into the fiber alignment fixture.

[0027] Fig.10 is a diagram showing a partial perspective cross-sectional view of the installed universal sealed fiber optic connector after inserting respective terminals into opposite ends of a fiber optic alignment fixture, wherein one terminal is terminated to a fiber optic cable disposed within a fuel tank and the other terminal is terminated to a fiber optic cable disposed outside the fuel tank.

[0028] Fig.11 is a partial cross-sectional view of a completed universal sealed fiber optic connector mounted on a fuel tank wall, wherein the universal sealed fiber optic connector includes a Figure 2D-2F The fiber optic ferrules shown in FIG. 4 optically couple an inner fiber optic cable and an outer fiber optic cable to each other.

[0029] Fig. 12A This is a diagram showing a side view of an ARINC 801 (A801) terminal.

[0030] Fig. 12B It indicates Fig. 12A FIG. 4 is a diagram depicting a side view of the internal features of the A801 ​​terminal.

[0031] Fig.13A and 13B Portions of a flow chart identifying steps of a universal sealed connector manufacturing process according to one embodiment.

[0032] Fig.14 is a hybrid diagram showing a design of a dual POF fuel level sensor, which includes a light source that supplies light to an optical fiber within a fuel tank via a first universal sealed fiber optic connector of the type disclosed herein, and also includes an electronic processor that processes data carried by light received from the optical fiber within the fuel tank via a second universal sealed fiber optic connector and a third universal sealed fiber optic connector of the type disclosed herein.

[0033] Reference will hereinafter be made to the drawings, in which similar elements in different drawings have the same reference numerals. DETAILED DESCRIPTION

[0034] For purposes of illustration, various embodiments of fiber optic devices (e.g., fiber optic connectors) and methods for making fiber optic devices will now be described in detail. At least some of the details disclosed below relate to optional features or aspects, which, in some applications, may be omitted without departing from the scope of the claims appended hereto. The disclosed fiber optic devices may be applied to measure liquid levels in fuel tanks of vehicles (such as, aircraft) or other types of liquid storage containers including vertical structures. Fuel tanks and other liquid storage containers are collectively referred to herein as "reservoirs."

[0035] In particular, exemplary embodiments of sealed fiber optic connectors and methods of assembling the same are described in detail below. However, not all features of actual implementations are described in this specification. Those skilled in the art will appreciate that in the development of any such actual implementation, many implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with related systems and related business constraints, which will vary from one implementation to another. In addition, it will be appreciated that such development work may be complex and time consuming, but will still be routine work for those of ordinary skill in the art who benefit from this disclosure.

[0036] Figures 1A to 1F are diagrams showing various side views of components of a ferrule assembly during successive stages of a universal sealed connector manufacturing process according to one embodiment. FIG. 2A to FIG. 2F It shows that Figures 1A to 1F A diagram of the internal features of the component depicted in FIG. FIG. 3A to FIG. 3F It means respectively in Figures 1A to 1F FIG. 1 is a perspective view of the components depicted in FIG.

[0037] The manufacturing process begins with a dimensionally accurate ferrule 30 ( Figure 1A ). Figure 2A As seen in FIG. 1 , the ferrule 30 has a hole 32 along a central axis, the hole including a first cavity 32a and a second cavity 32b at opposite ends of the ferrule 30 and a microporous section 32c connecting the first cavity 32a and the second cavity 32b. Figure 2A In the example depicted in FIG. 1 , the first cavity 32a and the second cavity 32b are formed by respective cylindrical inner surfaces 40a and 40b and respective tapered inner surfaces 42a and 42b of the ferrule 30. The inner diameter of each tapered inner surface decreases linearly to a minimum diameter at which the tapered inner surface intersects the end of the micro-bore section 32c. The micro-bore section 32c (which is sized and shaped to hold the optical fiber) and the first cavity 32a and the second cavity 32b (which is sized and shaped to receive the optical fiber) are formed by the cylindrical inner surfaces 40a and 40b and the tapered inner surfaces 42a and 42b of the ferrule 30. The inner diameter of each tapered inner surface decreases linearly to a minimum diameter at which the tapered inner surface intersects the end of the micro-bore section 32c. Figure 2D The first solder ring 34a and the second solder ring 34b shown in FIG. 3 are coaxial. The ferrule 30 has a cylindrical outer surface 36 and end surfaces 44a and 44b (in FIG. Figure 3A ), the end surfaces respectively surround corresponding openings at opposite ends of the bore 32 (or more specifically, the openings where the first and second cavities 32a, 32b intersect the end surfaces 44a and 44b, respectively). Preferably, the end surfaces 44a and 44b are perpendicular to the central axis A ( Figure 2A A planar annular surface oriented as shown in FIG.

[0038] The next step in the sealed fiber optic connector manufacturing process is to plate the cylindrical inner surfaces 40a and 40b of the ferrule 30 with a metal. For illustration, an example manufacturing process using a specific element from the periodic table will be described below. According to such an example embodiment, the metal plated onto the cylindrical inner surfaces 40a and 40b is gold.

[0039] The next step in the manufacturing process is to metallize the central region of the cylindrical outer surface 36 of the ferrule 30. The metallization 46 is Figure 1B , Figure 2B and Figure 3B According to one proposed embodiment, the metallization 46 comprises three different metal layers. The central area of ​​the cylindrical outer surface 36 is first coated with a titanium layer adhered to the ceramic surface of the ferrule 30; then, the titanium layer is coated with a palladium layer; and finally, the palladium layer is coated with a gold layer.

[0040] In the next step of the sealed fiber optic connector manufacturing process, Figure 1C , Figure 2C and Figure 3C As depicted in FIG, a gold-coated fiber stub 48 is inserted into the hole 32 of the ferrule 30. Preferably, the fiber stub is made of glass. Figure 1C , Figure 2C and Figure 3C As can be seen in FIG. 1 , the length of the gold-coated fiber ferrule 48 is greater than the length of the ferrule 30, so that the corresponding ends of the gold-coated fiber ferrule 48 protrude beyond the vertical planes of the end faces 44a and 44b of the ferrule 30. In this state, as in Figure 2C As best seen in FIG. 4 , the middle portion of the gold-coated fiber ferrule 48 is disposed within the micro-bore section 32 c of the ferrule 30 .

[0041] In the next step, the first solder ring 34 a and the second solder ring 34 b having openings with diameters slightly larger than the outer diameter of the gold-coated optical fiber ferrule 48 are slid onto the corresponding ends of the gold-coated optical fiber ferrule 48 , respectively. Figure 1C , Figure 2C and Figure 3C A state is depicted in which the ends of the gold-coated optical fiber ferrule 48 have passed through the openings of the first solder ring 34a and the second solder ring 34b, respectively, but the first solder ring 34a and the second solder ring 34b have not yet been placed in the first cavity 32a and the second cavity 32b of the ferrule 30, respectively.

[0042] According to the proposed embodiment used as an example herein, the first solder ring 34a and the second solder ring 34b are made of a first solder material including gold and tin (hereinafter referred to as "gold / tin solder"). The melting temperature of this exemplary gold / tin solder is less than the melting temperature of gold (1063°C) and greater than the melting temperature of tin (232°C). For example, the ratio of gold to tin in the gold / tin solder of the first solder ring 34a and the second solder ring 34b can be selected so that the melting temperature of the gold / tin solder is equal to 320°C.

[0043] After the first solder ring 34a and the second solder ring 34b have been placed in the first cavity 32a and the second cavity 32b, respectively ( Figure 2C Not shown, but see Figure 2D ), the gold-coated fiber ferrule 48 is welded to the two gold-coated cylindrical inner surfaces 40a and 40b of the ferrule 30 by a radio frequency induction heating process at 320°C (which is high enough to melt the gold / tin solder of the first solder ring 34a and the second solder ring 34b). The cooled gold / tin solder will melt the gold-coated fiber ferrule 48 ( Figure 2C ) is securely held within the ferrule 30, and a first portion 48a of the coated fiber ferrule 48 is disposed in the first cavity 32a, a second portion 48b of the coated fiber ferrule 48 is disposed in the second cavity 32b, and a third portion 48c of the coated fiber ferrule 48 is disposed in the microhole section 32c of the ferrule 30.

[0044] After the gold-coated fiber ferrule 48 has been soldered into the ferrule 30, the corresponding ends of the gold-coated fiber ferrule 48 are cut flush with the end faces 44a and 44b of the ferrule 30 ( Figure 2C Not shown, but see Figure 2D ). The ferrule 30 is then immersed in a pot of molten solder material (hereinafter referred to as the "second solder material") that is different from the first solder material. The immersed ferrule 30 is slowly pulled up. After the second solder material has cooled, the metallized central area on the outside of the ferrule is coated with a thick layer of the second solder material (hereinafter referred to as the "solder layer 50"). The ferrule 30 with the solder layer 50 is generally referred to as a "pre-tinned ferrule". The end face of the embedded gold-coated fiber optic ferrule 48 and the pre-tinned ferrule 30 are then cleaned. Figure 1D , Figure 2D and Figure 3D 3 shows the state of the ferrule 30 after the optical fiber end has been cleaved, coated with a second solder material, and cleaned.

[0045] According to the proposed soldering material used in the described example embodiments, the second solder material includes silver and tin (hereinafter referred to as "silver / tin solder"). The melting temperature of this exemplary silver / tin solder is less than the melting temperature of silver (961°C) and less than the melting temperature of tin (232°C). The melting temperature of the silver / tin solder is also less than the melting temperature of the gold / tin solder. The ratio of silver to tin in the silver / tin solder can be selected so that the melting temperature of the silver / tin solder is about 220°C. At certain ratios, some alloys become eutectic alloys - that is, the melting point of the alloy is lower than the melting point of either component. For example, a eutectic alloy consisting of 3.5wt.% silver and 96.5wt.% tin has a melting point of 221°C.

[0046] In the next stage of the sealed fiber optic connector manufacturing process, two aligned split sleeves 52a and 52b are prepared (at Figure 1E , Figure 2E and Figure 3E ). The aligned split sleeves 52a and 52b are cylindrical tubes made of a ceramic material (such as zirconium oxide) or bronze. Each aligned split sleeve is provided with a single longitudinal slit 54 extending over the entire length of the sleeve. The portions of the ferrule on the opposite sides of the solder layer 50 are then inserted into the respective aligned split sleeves 52a and 52b to form Figure 1F , Figure 2F and Figure 3F The complete ferrule assembly 56 is depicted in FIG.

[0047] The next stage in the connector manufacturing process is Figure 4A and Figure 4B Shown in. Figure 4A The ferrule assembly 56 is shown prior to insertion into a fiber alignment fixture 60 made of metal. According to some proposed embodiments, the fiber alignment fixture 60 may be made of copper, tungsten, or Kovar. Kovar is a nickel-cobalt-iron alloy having a composition designed to have substantially the same thermal expansion characteristics as borosilicate glass to allow for a tight mechanical bond between the two materials over a range of temperatures.

[0048] As in Figure 6B As seen in the partial cross-sectional view of FIG. 1 , the fiber alignment fixture 60 has a bore 62 along a central axis. The bore 62 includes a first cavity 62a and a second cavity 62b at opposite ends of the fiber alignment fixture 60 and a micro-hole section 62c connecting the first cavity 62a and the second cavity 62b. The micro-hole section 62c (which is sized and shaped to retain the ferrule assembly 56) and the first cavity 62a and the second cavity 62b (which are sized and shaped to receive the Fig.10The first and second terminals 80a, 80b, as seen in FIG. 6A and 6B, are coaxial. The micro-hole section 62c is disposed in the middle portion of the fiber alignment fixture 60 and has internal features designed to hold the ferrule assembly 56 in a middle position for welding.

[0049] Refer again Figure 4A , the fiber optic alignment fixture 60 has an outer annular protrusion 70 at a middle portion, and has cylindrical outer surfaces 68a and 68b on opposite sides of the outer annular protrusion 70. For reasons explained below, a pair of annular recesses 78a and 78b are formed at corresponding circumferential corners of the outer annular protrusion 70. The fiber optic alignment fixture 60 also has end surfaces 72a and 72b (at Figure 4A ), the end faces respectively surround corresponding openings at opposite ends of the hole 62 (or more specifically, the openings where the first cavity 62a and the second cavity 62b of the hole 62 intersect with the end faces 72a and 72b, respectively). Preferably, the end faces 72a and 72b are perpendicular to the central axis B of the fiber alignment fixture 60 (which is perpendicular to the central axis B of the fiber alignment fixture 60). Figure 2A A planar annular surface oriented coaxially with the center axis A of the ring 30 as seen in FIG.

[0050] After the ferrule assembly 56 has been inserted into the micro-hole section 62c of the fiber alignment fixture 60, the fixture and the assembly are joined by a welding operation in which the solder layer 50 is melted and then cooled. Figure 3A-Figure 3F and Figure 4A Another step in the universal sealed connector manufacturing process is partially depicted in FIG.

[0051] Figure 4B is a diagram showing a perspective view of the fiber alignment fixture 60 during soldering of the ferrule assembly 56 within the fiber alignment fixture 60. The outer annular protrusion 70 of the fiber alignment fixture 60 is clamped by a pair of clamps 74a and 74b. The clamps 74a and 74b are then heated to a degree that the temperature of the solder layer 50 is equal to or greater than the melting temperature of the silver / tin solder. In one proposed embodiment, the silver / tin solder of the solder layer 50 is heated to a temperature higher than the melting temperature of the silver / tin solder (e.g., higher than 221° C.). As the silver / tin solder is cooled and solidified, the ferrule assembly 56 is bonded to the inner middle portion of the fiber alignment fixture 60.

[0052] In the next stage of the connector manufacturing process, the fiber alignment fixture 60 (with the ferrule assembly 56 inside) is ready for insertion into the Fig. 6A64. The first step in the process of installing the fiber optic alignment fixture 60 in the bulkhead fixture 64 involves placing the third solder ring 58a and the fourth solder ring 58b in the corresponding annular recesses 78a and 78b of the outer annular protrusion 70. Figure 5 The third and fourth solder rings 58a and 58b are shown as not yet placed in the annular recesses 78a and 78b.

[0053] According to the proposed embodiment used as an example here, the third solder ring 58a and the fourth solder ring 58b are made of a third solder material including lead and tin (hereinafter referred to as "lead / tin solder"). The melting temperature of this exemplary lead / tin solder is less than the melting temperature of lead (327°C) and less than the melting temperature of tin (232°C). For example, the ratio of lead to tin in the lead / tin solder of the third solder ring 58a and the fourth solder ring 58b can be selected so that the melting temperature of the lead / tin solder is about 180°C. For example, a eutectic alloy composed of 63 wt.% lead and 37 wt.% tin has a melting point of 183°C.

[0054] Fig. 6A is a diagram showing a side view of the fiber optic alignment fixture 60 before the fiber optic alignment fixture 60 is inserted into the hole 66 formed in the bulkhead fixture 64. The fiber optic alignment fixture 60 has a third solder ring 58a and a fourth solder ring 58b disposed in corresponding annular recesses 78a and 78b. The bulkhead fixture 64 is made of metal (e.g., nickel-plated aluminum). The structure of the bulkhead fixture 64 includes a mounting flange 82 having a through hole 92, and the bulkhead fixture 64 can be attached to the wall of a fuel tank or other storage device through the mounting flange. The bulkhead fixture 64 also has an outer annular protrusion 88 disposed adjacent to the mounting flange 82. The outer annular protrusion 88 has a circular circumferential surface that will be disposed in the circular opening 5 (see fuel tank 2 (see)) when the completed fiber optic connector is installed in the wall 3. Fig.14 )of Figure 8 ). The partition fixing device 64 has a silicone rubber gasket ( Figure 6B Not shown, but see Figure 8 and Fig. 9 The annular groove 91 of the silicone rubber gasket 76a) in the bottom surface.

[0055] Figure 6B It indicates that the optical fiber alignment fixture 60 is inserted into Fig. 6A After the partition fixing device 64 is formed into a partition assembly 86 suitable for installation in the wall 3 of the fuel tank 2 and other storage (such as Fig. 9 A partial cross-sectional view of the Figure 6BAs seen in the drawings, the bulkhead fixture 64 has an internal structure including a cylindrical hole 66 having an inner diameter slightly larger than the outer diameter of the outer annular protrusion 70 of the fiber alignment fixture 60. When the fiber alignment fixture 60 and the bulkhead fixture are joined by welding, corresponding annular gaps 85a and 85b are formed between the hole 66 of the bulkhead fixture 64 and the corresponding cylindrical outer surfaces 68a and 68b of the fiber alignment fixture 60. The internal structure of the bulkhead fixture 64 also includes an inner annular protrusion 90 that projects radially inwardly and serves as a stopper to prevent further axial travel of the fiber alignment fixture 60 when the annular side of the outer annular protrusion 70 abuts against the facing annular side of the inner annular protrusion 90, Figure 6B in (and in Figure 7 and Figure 8 (center) depicts the abutment state.

[0056] When the optical fiber is aligned with the fixture 60 (with the welding ring) as Figure 6B When properly positioned within bulkhead fixture 64 as shown in FIG. 1 , third solder ring 58a is disposed between inner annular protrusion 90 of bulkhead fixture 64 and outer annular protrusion 70 of fiber alignment fixture 60, while fourth solder ring 58b (still disposed in annular recess 78b of fiber alignment fixture 60) contacts the inner wall of hole 66 of bulkhead fixture 64. With the correct positional relationship established, fiber alignment fixture 60 and bulkhead fixture 64 are ready to be joined by first melting and then solidifying third solder ring 58a and fourth solder ring 58b.

[0057] Figure 7 is a diagram showing a partial cross-sectional view of the fiber optic alignment fixture 60 within the bulkhead fixture 64 during a soldering operation. The outer annular protrusion 88 of the bulkhead fixture 64 is clamped by a pair of clamps 74a and 74b. The clamps 74a and 74b are then heated to a degree that the temperature of the third solder ring 58a and the fourth solder ring 58b is equal to or greater than the melting temperature of the lead / tin solder. In one proposed embodiment, the lead / tin solder of the third solder ring 58a and the fourth solder ring 58b is heated to a temperature that is higher than the melting temperature of the lead / tin solder (e.g., higher than 183°C). As the lead / tin solder is cooled and solidified, the fiber optic alignment fixture 60 is bonded to the bulkhead fixture 64 to form the bulkhead assembly 86.

[0058] In the next stage of the connector manufacturing process, bulkhead assembly 86 is ready for installation into the wall of the fuel tank. Figure 83 is a hybrid diagram showing a partially exploded view of the components of a universal sealed fiber optic connector prior to installation in an opening 5 in a fuel tank wall 3, including a bulkhead assembly 86 shown in cross section. The bulkhead assembly 86 is first passed from the interior of the fuel tank through a silicone rubber gasket 76a and then through the opening 5 in the fuel tank wall 3. On the exterior of the fuel tank, another silicone rubber gasket 76b is placed around the portion of the bulkhead assembly 86 that protrudes to the exterior of the fuel tank. Then, a mounting flange 38 (made of metal and having a threaded hole) is placed around the portion of the bulkhead assembly 86 that protrudes outward.

[0059] like Figure 8 As shown in FIG. 1 , the mounting flange 38 has a cylindrical hole 83 for receiving the bulkhead fixture 64, an annular groove 93 for receiving a portion of the silicone rubber gasket 76b, and a corresponding clamping screw ( Figure 8 Not shown, but see Fig. 9 After the threaded holes 97 of the mounting flange 38 and the through holes 92 of the mounting flange 82 have been aligned with the corresponding through holes formed in the fuel tank wall 3, the clamping screws 84 (see Fig. 9 ) is screwed into the threaded hole 97 of the mounting flange 38 to clamp the partition assembly 86 to the fuel tank wall 3.

[0060] Fig. 9 is a diagram showing a perspective cross-sectional view of the installed universal sealed fiber optic connector 12. When the threaded holes in the mounting flange are aligned with the through holes in the fuel tank wall 3, the clamping screws 84 are passed through the aligned holes. The mounting flange 38 and the mounting flange 82 are fastened together to the fuel tank wall 3 by a set of clamping screws 84. The silicone rubber gaskets 76a and 76b hermetically seal the bulkhead assembly 86 to the opening 5 in the fuel tank wall 3.

[0061] Still refer to Fig. 9 The next step in the sealed fiber optic connector manufacturing process is to place two terminal retaining clips 94a and 94b within the bore 62 of the fiber alignment fixture 60. One terminal retaining clip 94a is placed in the first cavity 62a of the bore 62; the other terminal retaining clip 94b is placed in the second cavity 62b of the bore 62. The bore 62 has built-in mechanical features to retain the terminal retaining clips 94a and 94b within the fiber alignment fixture 60.

[0062] After the terminal retention clips 94a and 94b have been placed within the fiber alignment fixture 60, the two terminals are inserted into the opposing ends of the sealed fiber optic connector 12 using an insertion tool. Fig.10 is a diagram showing a partial perspective cross-sectional view of the installed sealed fiber optic connector 12 after respective terminals 80 a and 80 b are inserted into opposite ends of the fiber alignment fixture 60 . Fig.11FIG. 1 is a cross-sectional top view of a universal sealed fiber optic connector 12 mounted on a fuel tank wall 3. Fig.10 and Fig.11 As shown in FIG. 1 , one terminal 80a is terminated to a fiber optic cable 96a disposed outside the fuel tank, and the other terminal 80b is terminated to a fiber optic cable 96b disposed inside the fuel tank. The terminals 80a and 80b are held by terminal retaining clips 94a and 94b, respectively. When the terminals 80a and 80b are as shown in FIG. Fig.10 When fully inserted as depicted in FIG. 1 , the end faces of the optical fibers (which may be made of glass or plastic) of the fiber optic cables 96a and 96b pass through the ferrule assembly 56 (eg, Figure 2F ) in the optical fiber ferrule 48 (as shown in Figure 2D ) optical coupling. Installation of the fiber optic connector 12 is accomplished by inserting a respective rubber boot 98a and 98b at each of the fiber alignment fixtures 60, which are slid onto the ends of the terminals 80a and 80b, respectively, to provide support. Optionally, each rubber boot 98a and 98b has a hole including two cylindrical passages that are axially aligned but have different inner diameters. The inner diameter of the first cylindrical passage is slightly larger than the outer diameter of the jacket portion of the fiber optic cable; the inner diameter of the second cylindrical passage is slightly larger than the outer diameter of the end of the terminal.

[0063] According to one proposed embodiment for use in an aircraft fuel tank, each terminal may be in Fig. 12A and Fig. 12B An ARINC 801 (A801) terminal 80 of the type depicted in FIG. The A801 ​​terminal 80 is made of metal and has a unitary structure having individual terminal portions 81a-81d of different outer diameters.

[0064] Fig. 12A is a diagram showing a side view of an A801 ​​terminal 80 terminating a fiber optic cable 96. Terminal portion 81a has a first outer diameter that enables terminal portion 81a to fit tightly within split sleeve 52a or 52b of ferrule assembly 56. Terminal portions 81b and 81c are configured to fit within first cavity 62a or second cavity 62b of fiber alignment fixture 60, which cavity includes respective portions having different inner diameters that match the outer diameters of terminal portions 81b and 81c. Terminal portion 81d has an outer diameter that is smaller than the outer diameter of terminal portion 81c, which allows a terminal retaining clip (e.g., Fig. 9 The terminal retaining clip 94a or 94b) seen in Figure 1 effectively latches the A801 ​​terminal 80 in place.

[0065] Fig. 12B It means that Fig. 12A801 terminal 80 is depicted in FIG. Terminal portions 81a and 81b each have a microbore section 15 sized to receive an unjacketed optical fiber 11 of a fiber optic cable 96. Terminal portions 81c and 81d each have a cylindrical bore section 17 sized to receive a portion of a fiber optic cable 96 having a jacket 13.

[0066] Each optical fiber is a flexible, optically transparent or translucent optical fiber made of extruded glass or plastic. The optical fiber can be used as a waveguide or light pipe to transmit light between the two ends of the optical fiber. The term "optical fiber" as used herein refers to a cylindrical dielectric waveguide that transmits light along its axis. The optical fiber includes a transparent core surrounded by a transparent cladding (hereinafter referred to as "cladding"), and the transparent cladding and the transparent core are both made of dielectric materials. Light is retained in the core by the phenomenon of total internal reflection. In order to confine the optical signal in the core, the refractive index of the core is greater than the refractive index of the cladding. The boundary between the core and the cladding can be abrupt (such as in a step-index optical fiber) or gradual (such as in a gradient-index optical fiber). The sealed optical fiber connector disclosed herein is universal in the sense that the connector can optically couple glass optical fibers or plastic optical fibers.

[0067] The description of one embodiment presented above includes identification of exemplary materials. Other material selections are also acceptable if compatible with the high temperature soldering process of the connector. In order to summarize the manufacturing process of the optical fiber connector without specifying the material, reference will now be made to FIG. 13A to FIG. 13B A flowchart is presented to describe a method for manufacturing a fiber optic device according to one embodiment.

[0068] Reference Fig.13A, the first step in the manufacturing method 102 is to coat the respective surfaces of the first cavity and the second cavity of the ferrule with metal (step 104). In addition, the optical fiber ferrule is coated with a metal layer to provide a coated optical fiber ferrule, the length of the optical fiber ferrule being greater than the length of the ferrule (step 106). Then, the central portion of the coated optical fiber ferrule is placed in the micro-hole section of the ferrule, and the respective end portions of the coated optical fiber ferrule are made to protrude beyond the first end face and the second end face of the ferrule respectively (step 108). After step 108, one end of the coated optical fiber ferrule is placed in the opening of a first solder ring made of a first solder material having a first melting temperature (step 110). Then, the first solder ring is placed in the first cavity of the ferrule (step 112). Similarly, the other end of the coated optical fiber ferrule is placed in the opening of a second solder ring made of the first solder material (step 114). Then, the second solder ring is placed in the second cavity (step 116). The coated fiber ferrule is then soldered to the surfaces of the first and second cavities of the ferrule by RF induction heating the first and second solder rings to a temperature above the melting temperature of the first solder material (step 118). After the fiber ferrule has been soldered within the ferrule, the opposing ends of the coated fiber ferrule are cut flush with the corresponding end faces of the ferrule (step 120). The central region of the outer surface of the ferrule is then metallized (step 122). After metallization, a circumferential layer of a second solder material is applied over the metallized central region, the second solder material having a second melting temperature lower than the first melting temperature of the first solder material (step 124). After the second solder material is applied, one end of the ferrule is inserted into the first portion of the first split sleeve (step 126) (the second portion of the first split sleeve will receive a portion of the first terminal), and the other end of the ferrule is inserted into the first portion of the second split sleeve (step 128) (the second portion of the second split sleeve will receive a portion of the second terminal) to form a ferrule assembly. Then, the ferrule assembly is placed in an opening in a middle portion of a hole of a fiber optic alignment fixture made of metal (step 130). Then, the ferrule assembly is welded in the fiber optic alignment fixture by heating the outer annular protrusion of the fiber optic alignment fixture to such an extent that the temperature of the second solder material layer is equal to or greater than the second melting temperature (step 132). After the ferrule assembly has been welded in the fiber optic alignment fixture, a third solder ring and a fourth solder ring made of a third solder material are placed in respective annular recesses formed adjacent to respective end faces of the outer annular protrusion of the fiber optic alignment fixture (step 134). The third solder material has a third melting temperature that is lower than the second melting temperature. Then, the outer annular protrusion of the fiber optic alignment fixture and the third solder ring and the fourth solder ring are placed in the hole of a diaphragm fixture made of metal (step 136).The optical fiber alignment fixture is then welded within the bulkhead fixture by heating the outer annular protrusion of the bulkhead fixture to a degree that the temperature of the third and fourth weld rings is equal to or greater than the third melting temperature to form a bulkhead assembly (step 138). The resulting bulkhead assembly is then sealingly mounted in an opening formed in the wall of a fuel tank or other reservoir (step 140).

[0069] For the purpose of illustration, the Fig.10 and Fig.11 A sealed fiber optic connector of the type shown in a fuel level measurement system. Fig.14 1 is a hybrid diagram showing the design of a dual POF fuel level sensor, which includes a light source that supplies light to a side-emitting plastic optical fiber (SPOF) 4 in a fuel tank 2 via a first sealed fiber optic connector 12a, and an electronic processor 20 that processes data carried by light received from two fluorescent plastic optical fibers (FPOF) 6a and 6b in the fuel tank 2 via a second sealed fiber optic connector 12c and a third sealed fiber optic connector 12b, respectively. The light emitted by the SPOF 4 is Fig.14 Indicated by arrows.

[0070] exist Fig.14 In the example shown in FIG. 1 , optical fibers 4, 6a and 6b are used to measure the level h of fuel in the fuel tank 2. In other embodiments, the same device can be used to detect other liquids. For example, the system described above can be used to detect the presence of water in a container or the presence of hydraulic fluid in a reservoir of a hydraulic system. The example of detecting fuel in a fuel tank is presented for illustrative purposes and is not meant to limit the scope of use of the system. Fig.14 The system shown in the figure.

[0071] Fig.14 6a and 6b having different light response efficiencies. Each of the FPOFs 6a and 6b is positioned at a distance from a SPOF 4 within a fuel tank 2 of an aircraft. The fuel tank 2 contains fuel 10. The fuel level measurement system includes an electronic processor 20 (or controller) configured to achieve stable and reliable fuel level sensing as disclosed in U.S. Pat. No. 10,175,087, the disclosure of which is incorporated herein by reference in its entirety. Physically, as the fuel level changes, the optical power output of each FPOF is the sum of the optical power output due to photons from the SPOF 4 that are not absorbed by the air 8 and the optical power output due to photons from the SPOF 4 that are not absorbed by the fuel 10.

[0072] like Fig.14As shown in FIG. 1 , the output of the FPOF 6a is connected to a first variable optical attenuator 14a (indicated by a box labeled VOA1), while the output of the FPOF 6b is connected to a second variable optical attenuator 14b (indicated by a box labeled VOA2). These variable optical attenuators are optical attenuators that attenuate the optical power output of the FPOF (i.e., reduce the intensity of the optical power output of the FPOF) by applying an external voltage. The degree of attenuation can be adjusted by changing the magnitude of the applied external voltage. The adjustment of the magnitude of the external voltage applied to the first variable optical attenuator 14a and the second variable optical attenuator 14b is controlled by corresponding control signals received from the electronic processor 20 via the electrical connector 22, which is shown in FIG. Fig.14 , and is electrically coupled to electronic processor 20 as shown in FIG.

[0073] The design of the dual FPOF fuel level sensor uses FPOF 6a as the fuel level sensing FPOF and uses FPOF 6b as the reference FPOF. During the calibration process, electronic digital data representing the relative properties of the fuel level and the corresponding optical power output are recorded in a lookup table stored in a non-transitory tangible computer-readable storage medium such as a non-volatile memory of the electronic processor 20. In addition, a third-order equation suitable for the digital calibration data is derived. When the optical power output from FPOF 6a is a value between two stored values, the third-order equation can be used to interpolate between the two stored values ​​in the lookup table. The relationship between the fuel level h and the optical power is derived from the measurement data obtained during the calibration and stored (as electronic digital data) in the memory of the processor.

[0074] The FPOFs 6a and 6b are connected to a first variable optical attenuator 14a and a second variable optical attenuator 14b via sealed optical fiber connectors 12c and 12b, respectively. The optical powers output from the first variable optical attenuator 14a and the second variable optical attenuator 14b are optically coupled to a first optical detector 16a and a second optical detector 16b, respectively. The magnitude of the signal output by the first optical detector 16a and the second optical detector 16b increases monotonically as the intensity of the light emitted from the ends of the FPOFs 6a and 6b increases. The photocurrent output from the first optical detector 16a is electrically coupled to a first transimpedance amplifier 18a (indicated by a box marked as TIA1), and the photocurrent output from the second optical detector 16b is electrically coupled to a second transimpedance amplifier 18b (indicated by a box marked as TIA2). A transimpedance amplifier is a current-to-voltage converter, most often implemented using an operational amplifier. The first transimpedance amplifier 18a and the second transimpedance amplifier 18b convert the photocurrent into corresponding voltages V1 and V2 that are linearly proportional to the optical power output from the first variable optical attenuator 14a and the second variable optical attenuator 14b. Fig.14As shown in , voltages V1 and V2 are applied to corresponding input ports of electronic processor 20 through electrical connector 22 .

[0075] The light source 24 that provides optical power input to the SPOF 4 via the sealed fiber optic connector 12a is a high power LED or a laser. Fig.14 The horizontal arrows in FIG. 2 represent light (i.e., photons) propagating from SPOF 4 to FPOFs 6a and 6b during operation of light source 24. Light source 24 is electrically coupled to light source power controller 26 (operated by Fig.14 The light source power controller is configured to stabilize the optical power input during temperature variations and throughout the lifetime of the operation of the dual FPOF fuel level sensor in response to control signals from the electronic processor 20.

[0076] The electronic processor 20 is configured to send fuel level data to a fuel level indicator 28 in the aircraft. The electronic processor 20 may be a dedicated microprocessor or a general purpose computer and may calculate the measured level (i.e., altitude) of the fuel by using a lookup table, a calibration curve, or by appropriately solving an equation. The fuel level indicator 28 may present information identifying the amount of fuel present within the fuel tank 2 based on the optical power data received by the electronic processor 20. The fuel level indicator 28 may take the form of a display device having a display processor that is programmed to display the measurement result (e.g., fuel amount) graphically and / or alphanumerically on a display screen.

[0077] Still refer to Fig.14 , the electronic processor 20 may be a computer or part of a flight control system located on an aircraft. When identifying the amount of fuel present in an irregularly shaped fuel tank, the electronic processor 20 may execute various routines to calculate the amount of fuel present based on the optical power data received from the corresponding pairs of FPOFs 6a and 6b appropriately placed in the various compartments of the fuel tank 2. The fuel information processing software may include routines for taking into account the shape of the fuel tank 2 to determine the amount of fuel remaining in the fuel tank 2. The fuel information processing software may also include routines for calibrating a process for forming a baseline before first use or for maintaining the accuracy of fuel readings. The readings provided to the fuel level indicator 28 by the electronic processor 20 may be integrated or averaged before presentation and may be provided at different time intervals.

[0078] Although fiber optic devices (e.g., fiber optic connectors) and methods for making fiber optic devices have been described with reference to various embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the teachings herein. In addition, many modifications may be made to adapt the concepts and adaptations of the practices disclosed herein to a particular situation. Therefore, it is intended that the subject matter covered by the claims is not limited to the disclosed embodiments.

[0079] In addition, this disclosure includes examples according to the following clauses:

[0080] Clause 1. A fiber optic device, comprising:

[0081] A ferrule (30) made of a ceramic material and having a hole (32) along a central axis, the hole comprising a first cavity and a second cavity (32a, 32b) at opposite ends of the ferrule and a microporous section (32c) connecting the first cavity and the second cavity, wherein the microporous section is coaxial with the first cavity and the second cavity;

[0082] a first metal layer on a surface (40a) of the first cavity;

[0083] a second metal layer on the surface (40b) of the second cavity;

[0084] A first welding ring (34a) disposed in the first cavity and having an opening;

[0085] a second welding ring (34b) disposed in the second cavity and having an opening; and

[0086] A coated optical fiber ferrule (48) coated with a metal layer, wherein a first portion (48a) of the coated optical fiber ferrule is disposed in an opening of the first solder ring, a second portion (48c) of the coated optical fiber ferrule is disposed in the micro-hole section of the ferrule, and a third portion (48b) of the coated optical fiber ferrule is disposed in an opening of the second solder ring.

[0087] The first solder ring and the second solder ring are made of a first solder material having a first melting temperature.

[0088] Clause 2. The optical fiber apparatus of clause 1, wherein:

[0089] The first portion of the coated optical fiber ferrule is bonded to the first cavity by fusion of the first solder ring and the first metal layer on the surface of the first cavity;

[0090] The second portion of the coated fiber ferrule is bonded to the second cavity by fusion of the second solder ring and the second metal layer on the surface of the second cavity.

[0091] Clause 3. The optical fiber device of Clause 1, wherein the first and second ends of the coated optical fiber stub are flush with the first and second end faces of the ferrule, respectively.

[0092] Clause 4. The fiber optic device of Clause 1, wherein the metal is gold.

[0093] Clause 5. The optical fiber apparatus of Clause 4, wherein the first solder material is a gold / tin solder.

[0094] Clause 6. The fiber optic device of Clause 1, further comprising a metallization (46) on a central region of an outer surface (36) of the ferrule.

[0095] Clause 7. The optical fiber apparatus of Clause 6, wherein the metallization comprises a titanium layer on a central region of an outer surface of the ferrule, a palladium layer on the titanium layer, and a gold layer on the palladium layer.

[0096] Clause 8. The optical fiber device of Clause 6, further comprising a second solder material layer (50) applied on the metallization, wherein the second solder material has a second melting temperature lower than the first melting temperature.

[0097] Clause 9. The fiber optic apparatus of Clause 8, wherein the solder material is silver / tin solder.

[0098] Clause 10. The optical fiber apparatus of clause 1, further comprising:

[0099] a second solder material layer (50) disposed around a central region of the outer surface of the ferrule, wherein the second solder material has a second melting temperature lower than the first melting temperature;

[0100] a first split sleeve and a second split sleeve (52a, 52b), one end of the ferrule being disposed within a first portion of the first split sleeve and the other end of the ferrule being disposed within a first portion of the second split sleeve to form a ferrule assembly (56), the second portion of each of the first split sleeve and the second split sleeve being configured to receive a terminal end (80) comprising a terminal portion of an optical fiber (11),

[0101] Wherein, the second solder material layer is arranged between corresponding end surfaces of the first cleavage sleeve and the second cleavage sleeve.

[0102] Clause 11. The optical fiber device according to clause 10, further comprising an optical fiber alignment fixture (60) made of metal and having an external annular protrusion (70) and a hole (62), the hole having a first cavity and a second cavity (62a, 62b) formed in opposite end portions and a hole segment (62c) in the middle portion, the first cavity and the second cavity being configured to receive corresponding terminals (80a, 80b), the hole segment connecting the first cavity and the second cavity and being configured to hold the ferrule assembly, wherein a portion of the external annular protrusion of the middle portion protruding from it is bonded to the ferrule through the second solder material layer.

[0103] Clause 12. The optical fiber device of clause 11, further comprising:

[0104] a bulkhead fixture (64) made of metal and having an outer flange (82) and a hole (66) in which a portion of the fiber alignment fixture including the outer annular protrusion is seated; and

[0105] A third solder ring and a fourth solder ring (58a, 58b) bond the outer annular protrusion to the diaphragm fixture, wherein the third solder ring and the fourth solder ring are made of a third solder material having a third melting temperature lower than the second melting temperature.

[0106] Clause 13. A method for manufacturing an optical fiber device, the method comprising:

[0107] (a) using metal to plate the respective surfaces of a first cavity and a second cavity of a ferrule, the ferrule being made of a ceramic material and having an axial hole (104) including the first cavity and the second cavity and a micro-hole section connecting the first cavity and the second cavity;

[0108] (b) coating the optical fiber ferrule with a metal layer to provide a coated optical fiber ferrule, wherein the length of the optical fiber ferrule is greater than the length of the ferrule (106);

[0109] (c) placing a central portion of the coated optical fiber stub within the micro-hole section, and respective end portions of the coated optical fiber stub protruding beyond the first end face and the second end face (108) of the ferrule;

[0110] (d) placing one end of the coated optical fiber ferrule in an opening of a first solder ring made of a first solder material having a first melting temperature (110);

[0111] (e) placing the first welding ring in the first cavity (112);

[0112] (f) placing the other end of the coated optical fiber ferrule in an opening of a second solder ring made of the first solder material (114);

[0113] (g) placing the second welding ring in the second cavity (116);

[0114] (h) soldering the coated optical fiber stub to the surfaces of the first cavity and the second cavity of the ferrule by simultaneously heating the first solder ring and the second solder ring to a temperature equal to or greater than the melting temperature of the first solder material (118).

[0115] Clause 14. The method according to Clause 13, further comprising: cutting the one end of the coated optical fiber ferrule flush with the first end surface of the ferrule, and cutting the other end (120) of the coated optical fiber ferrule flush with the second end surface of the ferrule.

[0116] Clause 15. The method according to clause 13, further comprising:

[0117] (i) metallizing a central region of the outer surface of the ferrule (122);

[0118] (j) applying a second solder material layer on the metallized central area, wherein the second solder material has a second melting temperature (124) lower than the first melting temperature.

[0119] Clause 16. The method according to clause 15, further comprising:

[0120] (k) inserting one end of the ferrule into a portion of a first split sleeve and inserting the other end of the ferrule into a portion of a second split sleeve to form a ferrule assembly (126),

[0121] Wherein, the second solder material layer is arranged between corresponding end surfaces of the first cleavage sleeve and the second cleavage sleeve.

[0122] Clause 17. The method according to clause 16, further comprising:

[0123] (1) placing the ferrule assembly within an opening in a middle portion of a bore of a fiber alignment fixture made of metal and having a first outer annular protrusion (130);

[0124] (m) soldering the ferrule assembly within the fiber alignment fixture by heating the first outer annular protrusion to a level where the temperature of the second solder material layer is equal to or greater than the second melting temperature (132).

[0125] Clause 18. The method according to clause 17, further comprising:

[0126] (n) placing a third solder ring and a fourth solder ring made of a third solder material in respective annular recesses formed adjacent to respective end surfaces of the first outer annular protrusion, wherein the third solder material has a third melting temperature (134) lower than the second melting temperature;

[0127] (o) placing the first outer annular protrusion and the third and fourth solder rings of the optical fiber alignment fixture into a hole of a bulkhead fixture made of metal and having a second outer annular protrusion and an outer flange, so that corresponding end portions of the optical fiber alignment fixture protrude beyond the first end face and the second end face (136) of the bulkhead fixture, respectively;

[0128] (p) welding the optical fiber alignment fixture within the baffle fixture to form a baffle assembly (138) by heating the second outer annular protrusion of the baffle fixture to a degree where the temperature of the third solder ring and the fourth solder ring is equal to or greater than the third melting temperature.

[0129] Clause 19. The method of Clause 18, wherein the first solder material is a gold / tin solder, the second solder material is a silver / tin solder, and the third solder material is a lead / tin material.

[0130] Clause 20. The method of clause 18, further comprising: sealingly installing the baffle assembly in an opening in a wall of a fuel tank (140).

[0131] Clause 21. An aircraft, comprising:

[0132] A fuel tank (2) having a wall (3) with an opening (5);

[0133] a bulkhead assembly (86) sealingly mounted in the opening in the wall of the fuel tank;

[0134] a first fiber optic cable (96b) disposed within the fuel tank and including a first terminal (80b) inserted into a first cavity (62b) at one end of the bulkhead assembly and including a first optical fiber (11) terminated within the first terminal;

[0135] a second fiber optic cable (96a) disposed outside the fuel tank and comprising a second terminal (80a) inserted into a second cavity (62a) at the other end of the bulkhead assembly and a second optical fiber (11) terminated in the second terminal,

[0136] Wherein, the partition assembly comprises:

[0137] A ferrule (30) having a bore section (32c);

[0138] The optical fiber ferrule (48) includes a first portion (48c) disposed in the hole section of the ferrule, a first end face in contact with the end face of the first optical fiber, and a second end face in contact with the end face of the second optical fiber, for optically coupling the first optical fiber to the second optical fiber.

[0139] Clause 22. An aircraft according to clause 21, wherein:

[0140] The ferrule is made of ceramic material and has a first cavity and a second cavity (32a, 32b) connected by the hole segment, the first cavity and the second cavity having corresponding metal-plated surfaces (40a, 40b);

[0141] The partition assembly also includes a first welding ring (34a) disposed in the first cavity and a second welding ring (34b) disposed in the second cavity;

[0142] The optical fiber ferrule also includes a second portion (48a) coupled to the first cavity via the first solder ring and a third portion (48b) coupled to the second cavity via the second solder ring.

[0143] As used herein, the term "solder ring" refers to solder material that is initially in the shape of a ring having a constant initial cross-sectional profile around its circumference, but which may subsequently deform during melting such that the melted solder material, while still ring-shaped, has a different cross-sectional profile that may not be constant.

Claims

1. An optical fiber device, comprising: A ferrule (30) made of a ceramic material and having a hole (32) along a central axis, the hole comprising a first cavity and a second cavity (32a, 32b) at opposite ends of the ferrule and a microporous section (32c) connecting the first cavity and the second cavity, wherein the microporous section is coaxial with the first cavity and the second cavity; a first metal layer on a surface (40a) of the first cavity; A second metal layer on the surface (40b) of the second cavity; A first welding ring (34a) is disposed in the first cavity and has an opening; A second welding ring (34b) disposed in the second cavity and having an opening; and A coated optical fiber ferrule (48) coated with a metal layer, wherein a first portion (48a) of the coated optical fiber ferrule is disposed in an opening of the first solder ring, a second portion (48c) of the coated optical fiber ferrule is disposed in the micro-hole section of the ferrule, and a third portion (48b) of the coated optical fiber ferrule is disposed in an opening of the second solder ring, The first solder ring and the second solder ring are made of a first solder material having a first melting temperature, Wherein, the optical fiber device further comprises: a metallization (46) on a central region of the outer surface (36) of the ferrule, The optical fiber device further comprises a second solder material layer (50) applied on the metallization, wherein the second solder material has a second melting temperature lower than the first melting temperature, Wherein, the optical fiber device further comprises: a first split sleeve and a second split sleeve (52a, 52b), one end of the ferrule being disposed within a first portion of the first split sleeve and the other end of the ferrule being disposed within a first portion of the second split sleeve to form a ferrule assembly (56), the second portion of each of the first split sleeve and the second split sleeve being configured to receive a terminal end (80) comprising a terminal portion of an optical fiber (11), Wherein, the second solder material layer is arranged between corresponding end surfaces of the first cleavage sleeve and the second cleavage sleeve.

2. The optical fiber device of claim 1, wherein: The first portion of the coated fiber ferrule is bonded to the first cavity by fusion of the first solder ring and the first metal layer on the surface of the first cavity; and The second portion of the coated optical fiber ferrule is bonded to the second cavity by fusion of the second solder ring and the second metal layer on the surface of the second cavity, And wherein the first end and the second end of the coated optical fiber ferrule are flush with the first end surface and the second end surface of the ferrule respectively.

3. The optical fiber device according to claim 1, wherein: The metal is gold.

4. The optical fiber device according to claim 3, wherein: The first solder material is gold / tin solder.

5. The optical fiber device according to claim 1, in, The metallization includes a titanium layer on a central region of an outer surface of the ferrule, a palladium layer on the titanium layer, and a gold layer on the palladium layer.

6. The optical fiber device according to claim 4, wherein: The second solder material is silver / tin solder.

7. The optical fiber device according to claim 6, wherein: The first solder material has a first melting temperature that is less than a melting temperature of gold and greater than a melting temperature of tin, and the second solder material has a second melting temperature that is less than a melting temperature of the gold / tin solder.

8. The optical fiber device according to claim 1, further comprising an optical fiber alignment fixture (60) made of metal and having an external annular protrusion (70) and a hole (62), the hole of the optical fiber alignment fixture having a first cavity and a second cavity (62a, 62b) formed in opposite end portions and a hole segment (62c) in a middle portion, the first cavity and the second cavity of the optical fiber alignment fixture being configured to receive corresponding terminals (80a, 80b), the hole segment connecting the first cavity and the second cavity of the optical fiber alignment fixture and being configured to hold the ferrule assembly, wherein A portion of the middle portion from which the outer annular protrusion protrudes is bonded to the ferrule through the second solder material layer, The optical fiber device further comprises: a bulkhead fixture (64) made of metal and having an outer flange (82) and a hole (66), wherein a portion of the optical fiber alignment fixture including the outer annular protrusion is disposed in the hole of the bulkhead fixture; and A third solder ring and a fourth solder ring (58a, 58b) bond the outer annular protrusion to the diaphragm fixture, wherein the third solder ring and the fourth solder ring are made of a third solder material having a third melting temperature lower than the second melting temperature.

9. A method for manufacturing an optical fiber device, the method comprising: (a) a plating step 104: plating corresponding surfaces of a first cavity and a second cavity of a ferrule with metal, wherein the ferrule is made of a ceramic material and has an axial hole, wherein the axial hole includes the first cavity and the second cavity and a micro-hole section connecting the first cavity and the second cavity; (b) coating step 106: coating the optical fiber ferrule with a metal layer to provide a coated optical fiber ferrule, wherein the length of the optical fiber ferrule is greater than the length of the ferrule; (c) placing step 108: placing the central portion of the coated optical fiber stub in the micro-hole section, wherein the corresponding end portions of the coated optical fiber stub protrude beyond the first end surface and the second end surface of the ferrule, respectively; (d) placing step 110: placing one end of the coated optical fiber ferrule in an opening of a first solder ring made of a first solder material having a first melting temperature; (e) placing step 112: placing the first welding ring in the first cavity; (f) placing step 114: placing the other end of the coated optical fiber ferrule in the opening of the second solder ring made of the first solder material; (g) placing step 116: placing the second welding ring in the second cavity; (h) welding step 118: welding the coated optical fiber ferrule to the surfaces of the first cavity and the second cavity of the ferrule by simultaneously heating the first solder ring and the second solder ring to a temperature equal to or greater than the melting temperature of the first solder material; (i) Cutting step 120: cutting one end of the coated optical fiber ferrule flush with the first end surface of the ferrule, and cutting the other end of the coated optical fiber ferrule flush with the second end surface of the ferrule; (j) Metallization step 122: metallizing a central area of ​​the outer surface of the ferrule; (k) applying step 124: applying a second solder material layer on the metallized central area, wherein the second solder material has a second melting temperature lower than the first melting temperature; (l) inserting step 126: inserting one end of the ferrule into a portion of a first split sleeve and inserting the other end of the ferrule into a portion of a second split sleeve to form a ferrule assembly, wherein the second solder material layer is disposed between respective end surfaces of the first split sleeve and the second split sleeve; (m) placing step 130: placing the ferrule assembly in an opening in a middle portion of a hole of a fiber alignment fixture made of metal and having a first outer annular protrusion; (n) a welding step 132 of welding the ferrule assembly within the optical fiber alignment fixture by heating the first outer annular protrusion to a degree that the temperature of the second solder material layer is equal to or greater than the second melting temperature; (o) installing step 134: placing a third solder ring and a fourth solder ring made of a third solder material in respective annular recesses formed adjacent to respective end surfaces of the first outer annular protrusion, wherein the third solder material has a third melting temperature lower than the second melting temperature; (p) placing step 136: placing the first outer annular protrusion and the third and fourth solder rings of the optical fiber alignment fixture into a hole of a bulkhead fixture made of metal and having a second outer annular protrusion and an outer flange, such that corresponding end portions of the optical fiber alignment fixture protrude beyond a first end surface and a second end surface of the bulkhead fixture, respectively; and (q) Welding step 138: Welding the optical fiber alignment fixture within the bulkhead fixture by heating the second outer annular protrusion of the bulkhead fixture to a degree that the temperature of the third weld ring and the fourth weld ring is equal to or greater than the third melting temperature to form a bulkhead assembly.

10. An aircraft, comprising: A fuel tank (2) having a wall (3) with an opening (5); an optical fiber device (12) made by the method of claim 9 and mounted in an opening in a wall of the fuel tank, wherein the bulkhead assembly (86) is sealingly mounted in the opening in the wall of the fuel tank; a first fiber optic cable (96b) disposed within the fuel tank and comprising a first terminal (80b) inserted into a first cavity (62b) at one end of the bulkhead assembly and comprising a first optical fiber (11) terminated within the first terminal; a second fiber optic cable (96a) disposed outside the fuel tank and comprising a second terminal (80a) inserted into a second cavity (62a) at the other end of the bulkhead assembly and a second optical fiber (11) terminated in the second terminal, and An optical fiber ferrule (48) comprises a first end face in contact with the end face of the first optical fiber and a second end face in contact with the end face of the second optical fiber, so as to optically couple the first optical fiber to the second optical fiber.

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