Master ferrule, master connector, inspection device and method for manufacturing master ferrule

Abstract

To provide a ferrule for a master cord of which performance does not deteriorate, even if measurement of an MT ferrule is repeated, and a master connector and an inspection device which do not need to replace a master ferrule.SOLUTION: A master ferrule 100 for inspecting a ferrule made of a resin includes an optical fiber insertion hole 112 for inserting an optical fiber, a guide hole 111 for inserting a guide pin, a boot insertion hole 121 for inserting a boot for a ferrule to which a plurality of optical fibers are inserted, and a flange part 120 projecting from the ferrule body 110, and is integrally formed by stainless steel containing iron and chromium. The stainless steel contains iron, chromium and nickel, and preferably has Vickers hardness of 500 or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a master ferrule for inspecting a resin ferrule, a master connector, an inspection device, and a method for manufacturing the master ferrule. [Background technology]

[0002] In recent years, there have been attempts to replace conventional electrical communications with optical communications, and it is being considered to use optical communications not only for conventional long-distance communications, but also for communications between terminals in local areas. In this situation, optical connectors are required to ensure connection accuracy while further improving productivity. Optical connectors used to connect optical fibers together use ferrules to connect the end faces of optical fibers with high positional accuracy. In recent years, as optical communications have become faster and denser, MT ferrules that support multiple cores and allow multiple optical fibers to be connected simultaneously with one connector are widely used. MT ferrules have many holes on the connection end face through which optical fibers are inserted, and the positions of these holes are designed with sub-micron accuracy. Therefore, it is necessary to inspect each production lot or each product to ensure that connection accuracy is maintained.

[0003] For example, Patent Document 1 (JP Patent Publication No. 2006-058400) describes a technique for simply and reliably checking whether an optical fiber is butted against a ferrule positioning member by bringing a master ferrule into contact with the ferrule. The manufacturing method described in Patent Document 1 is an optical connector assembly tool in which, of multiple pressing members provided on an optical fiber insertion table having an optical fiber guide groove for inserting an optical fiber into a ferrule held in the ferrule holding portion, the one closest to the ferrule holding portion is used as a pressing member for preventing the optical fiber from floating up, which allows the optical fiber to move in the direction opposite to the direction of feeding it into the ferrule, and the master ferrule is abutted against the ferrule while the bare optical fiber remains parallel to the central axis of the optical fiber insertion hole of the ferrule, thereby preventing uneven distribution of the optical fiber tip within the optical fiber insertion hole.

[0004] Patent Document 2 (JP Patent Publication No. 8-184420) describes a technique for improving the measurement accuracy of optical fiber position measurement in an optical MT connector. The method for measuring core position deviation of an MT connector described in Patent Document 2 involves connecting a reference connector, whose core position deviation amount and direction are known in advance, to a connector under test using a guide pin that fits into a guide pin hole, and measuring the connection loss of the connectors. Next, the guide pin is replaced with a thinner one, and the connector under test is shifted toward the end face while both connectors are connected, and the amount and direction of shift that minimizes the connection loss for each optical fiber is found, and the core position deviation of the connector under test is measured by finding the relative position deviation with respect to the reference connector.

[0005] Patent Document 3 (JP Patent Publication JP-A-9-80264) describes a technique for shortening the measurement time required for inspecting the connection characteristics of a large number of MT connectors, which requires a large number of tasks. The manufacturing method for a multi-core optical connector described in Patent Document 3 makes the rear end of the guide hole slightly narrower than the remaining portions, so that when the master connector of the present invention is used to inspect the connection characteristics of a large number of MT connectors, etc., the guide pin remains on the master side when the ferrule is attached or detached, eliminating the need to insert the guide pin for each measurement and shortening the measurement time.

[0006] Patent Document 4 (JP Patent Publication No. 2015-512531) describes a new optical fiber connector design that provides low insertion loss and low return loss, is easy to use, has high reliability due to its low sensitivity to the environment, and can be manufactured at low cost. In the fiber optic connector design described in Patent Document 4, the ferrule body is made of a metallic material that may be selected to have high rigidity (e.g., stainless steel), chemical inertness (e.g., titanium), high temperature stability (e.g., nickel alloys), a low coefficient of thermal expansion (e.g., Invar) or to match the coefficient of thermal expansion of other materials (e.g., Kovar, which is compatible with glass). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2006-058400 A [Patent Document 2] Japanese Patent Application Publication No. 8-184420 [Patent Document 3] Japanese Patent Application Publication No. 9-80264 [Patent Document 4] Special Publication No. 2015-512531 Summary of the Invention [Problem to be solved by the invention]

[0008] From the viewpoint of dimensional stability and moldability, MT ferrules are generally made of polyphenylene sulfide resin (PPS resin) and are usually manufactured by injection molding. MT ferrules manufactured in this way are standardized by IEC61754 and the like, and incorporating MT ferrules that comply with this standard into optical connectors enables optical communication connections with low loss. Therefore, the quality of the MT connector has a significant impact on the performance of the optical connection of the optical connector, so quality control of the MT connector is of great industrial significance.

[0009] In optical connector manufacturing sites, quality inspection of MT ferrules is generally performed by optically connecting a standard ferrule (master ferrule) for a master cord that serves as a reference to the ferrule to be inspected, measuring the connection loss of the ferrule to be inspected, and evaluating the performance. Then, using one master ferrule as a reference, many MT ferrules to be inspected are connected to perform the performance inspection of the MT ferrules. In this case, the master ferrule was selected by performing an image inspection of the connection end face and repeatedly connecting multiple MT ferrules to adopt the one that gave the best evaluation. In other words, the method adopted was to appropriately select the one that seemed to be of good quality from among ordinary MT ferrules.

[0010] However, because such conventional master ferrules are MT ferrules made of ordinary resin, there was a problem that when they were repeatedly attached to and detached from the MT ferrule being inspected, the resin would undergo plastic deformation, resulting in increased connection loss. In particular, when making a physical contact connection (PC connection), a large force of several N is applied to the connection end face, and furthermore, in order to prevent Fresnel reflection, the connection end face is often polished at an angle (usually 8°) before optical connection. Therefore, when connecting or disconnecting an optical connector, a large force is applied to the connection end face and guide pin hole of the MT ferrule, which can cause the resin to deform and increase connection loss. In addition, the guide pins used in optical connectors are generally made of SUS303 (stainless steel).When an optical connector is repeatedly connected and disconnected, the guide pins are repeatedly inserted and removed from the guide pin holes in the master ferrule, causing the guide pin holes to wear out, resulting in poor positional accuracy during optical connection.

[0011] Furthermore, as described above, the connection loss of the master ferrule worsens, making it necessary to replace the master ferrule frequently. However, the master ferrule is selected by appropriately choosing one that appears to be of good quality from among ordinary MT ferrules. However, every time the master ferrule is replaced, the inspection standards change, making it impossible to perform accurate quality inspections.

[0012] The manufacturing method of the optical connector described in Patent Document 1 involves abutting the master ferrule against the ferrule while keeping the bare optical fiber parallel to the central axis of the optical fiber insertion hole of the ferrule. However, since this master ferrule is a normal MT ferrule as defined in JIS C5981, etc., it cannot solve the above problem. The method for measuring core position deviation of an MT connector described in Patent Document 2 seeks to obtain relative position deviation and improves measurement accuracy, but it optically connects normal MT ferrules to each other and cannot solve the above problem. The ferrule used in the inspection described in Patent Document 3 has an improved guide hole shape, but the ferrule used is made of resin and cannot solve the above problem. Furthermore, Patent Document 4 discloses that one embodiment of a ferrule is made of a metal material, but the ferrule body is composed of multiple parts and is not intended to be used as a master ferrule for inspecting standardized resin ferrules.

[0013] The present invention has been made to solve the above problems, and an object of the present invention is to provide a master ferrule whose performance does not deteriorate even when measurements of MT ferrules are repeated. Another object of the present invention is to provide a master ferrule, a master connector, and an inspection device which can perform more accurate quality inspection without the need to replace the master ferrule. [Means for solving the problem]

[0014] (1) A master ferrule according to one aspect is a master ferrule for inspecting a resin ferrule, and is provided with an optical fiber insertion hole for inserting an optical fiber, a guide hole for inserting a guide pin, a boot insertion hole for inserting a ferrule boot through which a plurality of the optical fibers are inserted, and a flange portion protruding from the ferrule body, and is integrally formed from stainless steel containing iron and chromium.

[0015] The master ferrule according to one aspect has an optical fiber insertion hole, a guide hole, a boot insertion hole, and a flange portion, which are integrally formed from stainless steel containing iron and chromium, so that the hardness can be made higher than that of a typical MT ferrule that is molded from resin. The standard ferrule for the master cord (master ferrule) is used for connecting optical connectors many times, and the resin becomes deformed and the holes become worn, causing the connection loss to deteriorate over time. In particular, when an obliquely polished ferrule is connected to a PC, a large contact force is applied obliquely to the contact surface of the ferrule, the guide pin insertion hole, and each optical fiber, causing a noticeable deterioration problem. According to one aspect of the master ferrule, even when subjected to repeated stress accompanying attachment and detachment of an optical connector or a large spring force accompanying a PC connection, it does not deform, the connection loss remains unchanged, and there is almost no degradation in performance. Also, unlike resin ferrules, the guide pin holes are less likely to wear out even when the guide pins are repeatedly inserted and removed, so the positional accuracy of the fiber holes is ensured and there is almost no degradation in performance.

[0016] Furthermore, stainless steel, which contains iron and chromium, has an established track record of die cutting processing technology, and it is possible to improve the processing accuracy of the hole position compared to resin ferrules. Therefore, it can be used as a reference for more accurate evaluation. In addition, conventional resin ferrules are susceptible to stress on the die pins during molding, making it difficult to form all of the optical fiber insertion holes and guide holes in parallel. On the other hand, metal ferrules have high heat dissipation properties, and parallel holes can be formed with high accuracy by cutting the connection end face with a micro-diameter drill. Therefore, even if polished multiple times, the positional accuracy of the optical fiber insertion hole does not change, making it possible to create a master ferrule whose performance does not deteriorate. As a result, master ferrules that previously had to be discarded when the connection end face deteriorated due to removal and attachment can be reused by polishing the connection end face again.

[0017] (2) A master ferrule according to a second aspect of the present invention is the master ferrule according to the first aspect of the present invention, wherein the stainless steel contains iron, chromium and nickel and has a Vickers hardness of 500 or less.

[0018] Since the master ferrule is made of stainless steel, it can be made highly accurate and hard, and is less susceptible to deterioration over time, making it possible to provide a master ferrule whose performance does not deteriorate. In particular, stainless steels that contain iron, chromium, and nickel (such as SUS304) have a linear expansion coefficient similar to that of PPS resin. By using a master ferrule with a similar linear expansion coefficient to the resin ferrule to be measured, a more accurate performance evaluation can be performed.

[0019] Furthermore, the hardness of stainless steel (Vickers hardness: HV) is lower than that of quartz glass (1000 or more), and in particular, it is preferable that the hardness of SUS304 (about 190) is equal to or lower than that of glass (500 or more). Therefore, by polishing the connection end face with a polishing device for general MT ferrules, the optical fiber can be made to protrude slightly from the end face. This ensures a reliable physical contact connection (PC connection) with the resin MT ferrule being measured.

[0020] (3) A master ferrule according to a third aspect of the present invention is the master ferrule according to the second or third aspect of the present invention, further comprising an optical fiber inserted into the optical fiber insertion hole, and a ferrule boot through which the optical fiber is inserted, and the optical fiber may be fixed in the optical fiber insertion hole with a thermosetting resin.

[0021] In an embodiment, this corresponds to a master ferrule into which an optical fiber is assembled. This makes it possible to easily measure the performance of MT ferrules using MT clips or the like. In addition, various connector manufacturers manufacture optical connectors for MT ferrules, but the master ferrule with an integrated optical fiber can be used by all companies, making it highly versatile.

[0022] (4) A master connector according to another aspect uses the master ferrule according to any one of the first to third aspects of the present invention in a connecting portion, and can be optically connected to a resin ferrule.

[0023] This makes it possible to provide a master connector that does not require replacement of the master ferrule. Furthermore, it is possible to provide a master connector that allows for more accurate quality inspection than before.

[0024] (5) An inspection device according to another aspect uses the master ferrule according to any one of the first to third aspects of the present invention in a connecting portion, and is capable of inspecting the performance of a resin ferrule.

[0025] This makes it possible to provide an inspection device that does not require replacement of the master ferrule. Furthermore, the inspection device can perform more accurate quality inspection than before.

[0026] (6) A method for producing a master ferrule according to another aspect is a method for producing a master ferrule according to any one of the first to third inventions, in which the optical fiber insertion hole and the guide hole are formed by cutting.

[0027] Conventional MT ferrules are made by injection molding resin, in which optical fiber insertion holes and guide holes are formed using long, rod-shaped die pins. However, when viscous resin is injected into the die at high temperature and pressure, the die pins are subjected to stress and tilt, making it extremely difficult to form multi-fiber insertion holes that are parallel with high accuracy. Therefore, although conventional MT ferrules have optical fiber insertion holes positioned with high precision on the connection end face, polishing the connection end face multiple times increases the eccentricity of the optical fiber insertion hole, resulting in a problem of deterioration of connection characteristics.

[0028] On the other hand, according to the manufacturing method of the master ferrule according to the sixth aspect of the present invention, the optical fiber insertion holes and guide holes are formed by cutting using a micro-diameter drill, so that all holes in the ferrule body can be formed parallel with high precision. As a result, even if a connection end face obtained by optical polishing once is polished again, the positional relationship between the optical fiber insertion hole and the guide hole in the new connection end face remains almost unchanged. Therefore, even in cases where the master ferrule has been deteriorated or damaged due to repeated attachment and detachment, or where the spherical shape of the optical fiber protruding from the connection end face has deteriorated, in which the master ferrule had to be replaced in the past, the master ferrule can be made usable again by polishing the connection end face again. [Brief description of the drawings]

[0029] [Figure 1] 1A to 1C are a front view, a side view, and a cross-sectional view of a master ferrule according to an embodiment. [Diagram 2] This is a photograph of the master ferrule with an optical fiber installed. [Diagram 3]This is a photo of the master connector equipped with a master ferrule. [Figure 4] 1 is a photograph of a connection end face of a master ferrule incorporating an optical fiber. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] The preferred embodiments of the present invention are as follows, but the present invention is not limited thereto. Furthermore, at least a part of the configuration of each embodiment can be appropriately combined with a part of another embodiment without departing from the spirit and scope of the present invention.

[0031] The master ferrule 100 of the present invention is a standard ferrule for a master code used to measure the optical characteristics of a resin ferrule 500. The master ferrule 100 has known optical characteristics, a shape of a connection end face, and the like, and is optically connected to the ferrule 500 to be measured and used as a reference. In measuring the ferrule 500, the master ferrule 100 with the optical fiber 300 inserted therethrough and the ferrule 500 with the optical fiber 300' inserted therethrough are brought into strong contact while being precisely aligned using the guide pin 400, and the connection loss of the light at this time is measured. For example, if the positional accuracy of some of the fiber holes in the ferrule 500 is poor, the amount of light from that optical fiber will be low, and if it is below a specified value, the ferrule 500 will be evaluated as an NG product. Such measurements are repeated many times during the manufacturing process, so that a large number of ferrules 500 are attached to and detached from the master ferrule 100. The master ferrule 100 used in this embodiment is shown as an example assuming the case of measuring a 24-core MT ferrule of the IEC 61754 standard, but the present invention is not limited to this embodiment, and can be applied by appropriately modifying the design so long as it is a multi-core MT ferrule using guide pins.

[0032] (Master Ferrule 100) 1(a), (b), (c), and (d) are a front view, a left side view, a right side view, and a cross-sectional view taken along line AA, respectively, of a master ferrule 100 according to this embodiment. A connecting end face 101 is provided on the front face (left side face) of the master ferrule 100 of this embodiment, and the connecting end face 101 is optically polished so as to be connectable with the connecting end face of another ferrule 500 for measurement. A boot insertion hole 121 for inserting a ferrule boot 200 is provided on the rear end face 102 (right side face) of the master ferrule 100. A window portion 115 for introducing adhesive is opened on the top face (front side) of the master ferrule 100, and communicates with the boot insertion hole 121 through an internal space 116. As shown in FIG. 1(d), the boot insertion hole 121 is designed to have a larger opening area than the internal space 116, and the inserted ferrule boot 200 is usually inserted up to a step portion connecting the boot insertion hole 121 and the internal space 116. In the following description of this specification, the direction connecting the connection end face 101 and the rear end face 102 (the left-right direction in FIG. 1(a)) is referred to as the length direction or connection direction, the direction perpendicular to the length direction (the up-down direction in FIG. 1(a)) is referred to as the width direction, and the direction perpendicular to the length direction and width direction is referred to as the up-down direction or thickness direction.

[0033] Fig. 2 is a photograph of the master ferrule 100 with an optical fiber incorporated therein, in which an optical fiber 300 is incorporated into the master ferrule 100 of Fig. 1. As shown in Fig. 1 and Fig. 2, the master ferrule 100 of this embodiment comprises a ferrule body 110 and a flange portion 120 formed to protrude from the ferrule body 110 in the entire circumferential direction.

[0034] This flange 120 is used to fix the master ferrule 100 when polishing the connection end face 101, and is also used to fix the master ferrule 100 inside the master connector 10. Therefore, the surface forming the flange 120 forms the reference surface during polishing, and is also the part to which stress is applied during polishing and connection of the master connector 10. The master ferrule 100 illustrated in this embodiment has the flange portion 120 formed up to a position 2.0 mm in the longitudinal direction from the rear end face 102 of the ferrule body 110 and protruding 0.3 mm from the ferrule body 110, but is not limited to this. Also, the master ferrule 100 of this embodiment has the flange portion 120 protruding in the entire circumferential direction of the ferrule body 110, but the flange portion 120 may protrude only partially from the ferrule body 110 depending on the type of master connector 10 used.

[0035] The size of the master ferrule 100 exemplified in this embodiment is such that the length of the ferrule body 110 in the connection direction is 8.0 mm, the width direction (guide pin direction) is 6.4 mm (7.0 mm including the flange portion 120), and the vertical direction (thickness direction) is 2.5 mm (3.0 mm including the flange portion). A window 115 for filling with adhesive is formed on the top surface of the ferrule body 110, and is formed so that the rear end face side of the optical fiber insertion hole 112 and the guide groove 114 can be seen from the top surface side. The size of the window 115 in this embodiment is 1.5 mm in the length direction and 3.0 mm in the width direction, but the design may be changed as appropriate to make it easier for the worker to work. A boot insertion hole 121 for inserting a boot is formed in the rear end face 102 of the ferrule body 110, and communicates with the window portion 115 via an internal space 116. The opening of the boot insertion hole 121 in this embodiment is 3.6 mm in the width direction and 1.7 mm in the thickness direction, and the internal space 116 is designed to be somewhat narrow at 1.4 mm only in the thickness direction. As a result, even when the ferrule boot 200 is inserted into the boot insertion hole 121, the internal space 116 can be secured, and the optical fiber 300 can be reliably fixed with an adhesive.

[0036] 2, a fiber tape in which a plurality of optical fibers are bundled can be inserted into the ferrule boot 200, and the optical fibers are exposed at the ends of the fiber tape from which their coatings have been removed. The internal space 116 can be filled with adhesive injected through the window 115, and the optical fiber can be inserted into the internal space 116 filled with adhesive. A semicircular guide groove 114 is formed on the internal space 116 side of the optical fiber insertion hole 112, which allows the optical fiber to be easily inserted into the optical fiber insertion hole 112. The master ferrule 100 with the optical fiber 300 inserted in this manner will be in a state in which the adhesive and optical fiber 300 protrude from the connection end face 101, so by removing any unnecessary adhesive and optical fiber 300 and optically polishing the connection end face 101, it will be possible to optically connect it to the ferrule 500 to be measured.

[0037] In this embodiment, the master ferrule 100 and the ferrule 500 to be measured have the same structural outer shape, but the type of ferrule 500 is not limited as long as it is connectable to the master ferrule 100. That is, if the arrangement of the guide pin holes and the optical fiber insertion holes and the diameters of the guide pin holes and the optical fiber insertion holes are the same, they are compatible and optical connection is possible. For example, the ferrule 500 to be measured may be a short type in which the length of the ferrule body 110 (the distance between the connection end face and the rear end face) is half, or may be a slim type in which the thickness of the ferrule body 110 is half.

[0038] (Fiber insertion hole / Guide hole) In the master ferrule 100 of this embodiment, a plurality of optical fiber insertion holes 112 for inserting, positioning, and fixing the removed portion of the optical fiber 300 into the ferrule body 110, and guide grooves 114 that are connected to the rear ends of each optical fiber insertion hole 112 and are parallel to each other are formed in the ferrule body 110 from the connection end face 101 to the rear end face 102. The optical fiber insertion holes 112 are arranged at a predetermined pitch so that adjacent holes are parallel to each other, and the axis of the optical fiber insertion holes 112 is perpendicular to the connection end face of the master ferrule 100. This allows the connection end faces of the optical fibers to abut precisely on the same axis. The master ferrule 100 of this embodiment is exemplified as a 24-core MT ferrule in which the optical fiber insertion holes 112 are arranged in two rows of 12 cores, but this number of connection cores can be appropriately changed as necessary. For example, 12 cores or 16 cores may be arranged in one row, or these can be arranged in two, three, or four rows. Also, the master ferrule 100 of this embodiment is exemplified as an MT ferrule in which the optical fiber insertion holes 112 are arranged at a pitch of 0.25 mm, but this pitch can also be appropriately changed depending on the number of cores, etc.

[0039] The angle of the optical fiber insertion hole 112 with respect to the connection end face is quantified as a bend angle. The bend angle of the optical fiber insertion hole 112 is the angle between a perpendicular line to the connection end face and the center line of the optical fiber insertion hole when viewed from a position at a depth of 0.3 mm to 0.5 mm from the connection end face 101 of the master ferrule 100. The absolute value of the bending angle of the optical fiber insertion hole 112 is preferably 0.4° or less, and more preferably 0.3° or less. In general resin ferrules, PPS resin, which has excellent molding stability, is used, and the PPS resin is manufactured by injection molding using a long, rod-shaped mold pin. In this case, when the molten resin is injected into the mold, the resin forms a vortex near the mold pin, and the mold pin is subjected to stress, so it is difficult to control the bending angle of the hole to be sufficiently small. On the other hand, since the master ferrule 100 of this embodiment is made of metal, the hole can be formed with high accuracy even when it is cut. Therefore, since the bending angle of the optical fiber insertion hole 112 can be designed to be small, the positional accuracy of the optical fiber insertion hole 112 can be maintained high even when the connection end face 101 is polished multiple times, and the MT ferrule of the master code that can be used as a reference can continue to exhibit sufficient performance.

[0040] The bending angle in this embodiment is a numerical value measured as follows. That is, the amount of fiber hole misalignment at the end face of the master ferrule 100 is measured by a 2 / 3-dimensional automatic dimension measuring machine. The amount of fiber hole misalignment is measured by setting the intersection of the line connecting the midpoints of the two guide holes and its perpendicular bisector as the coordinate (0,0), measuring the position of each fiber hole, and calculating the difference between the measured value and the design value as the amount of misalignment. Furthermore, the amount of fiber hole misalignment is calculated in the same manner as above even at a depth position of 0.3 mm or more and 0.5 mm or less from the end face. In this way, the fiber hole bending angle is calculated from the difference between the amount of fiber hole misalignment at the end face and the amount of fiber hole misalignment at a predetermined depth position.

[0041] The optical fiber insertion hole 112 of this embodiment is formed with a reduced diameter section 113 whose diameter gradually decreases from the base end side (guide groove 114 side) through which the optical fiber 300 is inserted toward the tip side (connection end face 101 side). This reduced diameter section is provided at a position about 1 / 5 from the tip side of the optical fiber insertion hole 112, and it is preferable that the inner diameter of the optical fiber insertion hole 112 is reduced to about 1 / 6. The master ferrule 100 exemplified in this embodiment is capable of inserting an optical fiber with a cladding diameter of 0.125 mm, and in this case, it is preferable that the inner diameter of the tip side of the optical fiber insertion hole 112 is 0.1255 mm, and the inner diameter of the base side is 0.200 mm. This creates a clearance of 0.5 μm with the optical fiber on the tip side, and an adhesive is filled into this gap and hardens and shrinks, allowing the optical fiber to be reliably fixed to the optical fiber while precisely ensuring the positional accuracy of the optical fiber connection end face. The inner diameter of the optical fiber insertion hole 112 can be changed as appropriate according to the cladding diameter of the optical fiber to be inserted, and the cladding diameter of the optical fiber can be appropriately set to 50 μm, 80 μm, 125 μm, 250 μm, etc. The type of optical fiber can also be appropriately selected, and for example, a single mode optical fiber, a multimode optical fiber, a polarization maintaining fiber, a multicore fiber, etc. can be used.

[0042] In the master ferrule 100 of this embodiment, a part of the connection end face 101 of the master ferrule 100 is polished at an angle of 8°. This makes it possible to suppress Fresnel reflection and reduce connection loss when PC connection is performed. In this case, although the connection end face 101 is inclined at an angle, the two ferrules are abutted in a straight line by the guide pin 400, and the optical fibers 300, 300' held by the ferrules are optically connected in a straight line. In this embodiment, the connection end surface 101 is polished at an 8° angle, but normal vertical polishing may be used. The connection method is not limited to PC connection, and a refractive index matching material may be applied to or inserted into the connection end surface 101, or an optical lens array or the like may be inserted.

[0043] The optical fiber 300 attached to the master ferrule 100 of this embodiment has 12 cores bundled together as one optical fiber ribbon, and the optical fiber ribbons are inserted in two stages into the boot insertion hole 121. This optical fiber ribbon is led out from the leading portion of the boot insertion hole 121 of the master ferrule 100 while being protected by the ferrule boot 200 made of an elastic material such as rubber or synthetic resin. As the optical fiber ribbon, an optical fiber tape core wire in which coated optical fiber strands are integrated with a common coating, or an optical fiber ribbon cord in which a protective coating is further applied on the optical fiber tape core wire, etc. can be used.

[0044] The master ferrule 100 of this embodiment has two guide holes 111 in parallel with the optical fiber insertion hole 112. A guide pin 400 is inserted and fixed into this guide hole 111, and optically connects the optical fiber 300 and the optical fiber 300' by butting the connection end face of the ferrule 500 to be measured. In this way, the axial centers of all the optical fibers 300, 300' are precisely positioned by the guide pin 400, and the connection faces are butted together by a coupling clip, connector, or the like, to make an optical connection. In this embodiment, the two guide holes 111 are spaced apart from each other at a pitch of 4.6 mm, and the inner diameter of each guide hole 111 is exemplified as 0.8 mm.

[0045] In the example of FIG. 2, a guide pin 400 of 0.7 mm similar to that of an existing MT ferrule is used. Conventional resin MT ferrules generally have guide holes of about 0.699 mm, which is slightly smaller than the outer diameter of the guide pin 400, in order to ensure the positional accuracy of the connection end face. However, the inner diameter of the guide hole 111 of the master ferrule 100 of this embodiment is designed to be equal to or larger than the outer diameter of the guide pin 400, and is preferably 0.3 mm larger than the outer diameter of the guide pin 400, and more preferably 0.1 mm larger. Since the master ferrule 100 of this embodiment is made of metal, sufficient positional accuracy can be ensured even within the above range. Furthermore, the master ferrule 100 of this embodiment can be cabled using the standard method for MT connectors (JIS C5981) and MT ferrules (JIS C5964-5), and can be coupled using a positioning pin coupling method. Since the master ferrule 100 of this embodiment complies with the standards for the existing pin coupling method, it can be connected using conventional connecting parts, and is therefore compatible with existing MT ferrules.

[0046] (alloy) The master ferrule 100 is integrally formed from an alloy containing iron and chromium. Examples of alloys containing iron and chromium in this embodiment include stainless steels, such as chromium-based stainless steels, martensitic stainless steels such as SUS410, ferritic stainless steels such as SUS430, austenitic stainless steels such as SUS304 and SUS316, austenitic-ferritic stainless steels such as SUS329J1, and precipitation hardening stainless steels.

[0047] Of these, austenitic stainless steel is preferable because it provides precision machinability, corrosion resistance, and heat resistance. Of these, it is more preferable to use SUS304, which contains 18 mass % chromium and 8 mass % nickel. In particular, SUS304 has a linear expansion coefficient α ( / ℃, 0~100℃) of 18×10 -6 Therefore, it is possible to provide a master ferrule 100 that minimizes the effect of the measurement environment on connection loss. In addition, since SUS304 can have a hardness (Vickers hardness: HV) of about 190, it is possible to provide a master ferrule 100 that enables optical connection with low loss.

[0048] That is, since the positioning of each fiber in the MT ferrule is precisely determined based on coordinates with reference to the guide hole 111, the linear expansion coefficient of the material at the measurement environment temperature significantly affects the positioning of the connection end face. The linear expansion coefficient α ( / °C, 0 to 100°C) of the alloy used in the master ferrule 100 is preferably 16 to 21, more preferably 17 to 20. This allows the master ferrule 100 to have low connection loss and high quality. The method for measuring the linear expansion coefficient α in this case is based on JIS Z2285.

[0049] In addition, in order to connect optical fibers to each other by PC connection, the optical fiber needs to slightly protrude from the connection end face of the MT ferrule. This is greatly influenced by the hardness (Vickers hardness: HV) of the MT ferrule. That is, when the connection end face is polished using a polishing device for MT ferrules, the hardness of the MT ferrule is set to a predetermined range lower than the hardness of glass (500 or more) or the hardness of quartz glass (1000 or more), so that the connection end face of the MT ferrule is preferentially polished and the end face of the optical fiber can be suitably protruded. The hardness (Vickers hardness: HV) of the master ferrule 100 is preferably 80 or more and 400 or less, more preferably 100 or more and 300 or less. This allows the master ferrule 100 to have low connection loss and high quality. The method for measuring the Vickers hardness in this case is based on JIS Z2244.

[0050] (polishing) The connection end face 101 of the master ferrule 100 of this embodiment can be polished using a known polishing device. The polishing method can be the same as that for the resin MT ferrule. For example, the resin and optical fiber 300 protruding from the connection end face 101 are simply removed, and the connection end face 101 is polished at an angle of 8° in a flat polishing process. Furthermore, by appropriately polishing the connection end face 101 with a fine abrasive in a buff polishing process, the tip of each optical fiber 300 can be made to protrude a required amount (several microns) from the connection end face 101 of the master ferrule 100 so that PC contact can be made. In this case, in the surface polishing step, a plurality of polishing steps, such as a rough polishing step, a medium polishing step and a finish polishing step, can be provided by using polishing members having different hardness and grain size. Furthermore, the hardness and grain size of the polishing member can be appropriately adjusted depending on the hardness of the alloy of the master ferrule 100 .

[0051] Ordinary resin ferrules 500 are molded by injection molding PPS resin. In this case, the optical fiber insertion holes and guide holes are formed using long, rod-shaped mold pins, so it is extremely difficult to mold all the optical fiber insertion holes in parallel with high precision. Therefore, if the connection end face is deeply polished, the eccentricity of the optical fiber insertion holes becomes large, which causes a problem of increased connection loss.

[0052] On the other hand, the master ferrule of this embodiment is made of SUS, which has excellent cutting workability, and also has excellent heat dissipation properties, so holes can be drilled with high precision using a micro-diameter drill. Therefore, even if the connection end face obtained by optical polishing once is polished again, the positional relationship between the optical fiber insertion hole and the guide hole remains almost unchanged. Therefore, if the master ferrule is deteriorated or damaged due to repeated attachment and detachment, or if the spherical shape of the optical fiber protruding from the connection end face is deteriorated, the connection end face can be polished again to make the master ferrule usable again.

[0053] (Connection test) At the optical connector manufacturing site, the manufactured MT ferrule is filled with adhesive, a boot and an optical fiber are inserted, and the connection end face is polished to obtain a ferrule with an optical fiber built in. This ferrule with an optical fiber built in is usually made of a resin such as PPS. The resin ferrule 500 thus obtained is generally incorporated into a connector such as an MPO connector, and then connected to the master connector 10, and the connection loss, return loss, and the like are measured. The master connector 10 is a connector that serves as an inspection standard, and the fiber core position and connection loss at the connection end face are strictly controlled based on JIS C5982, etc. The master ferrule 100 of the master connector 10 has known optical characteristics such as the insertion loss amount and return loss amount, and end face shapes such as the fiber curvature radius, end face protrusion amount, and core eccentricity amount, so that the performance of the ferrule 500 to be inspected can be evaluated by connecting the ferrule 500.

[0054] Generally, performance evaluation of an optical connector is performed for each production lot or each production run, and each time the ferrule 500 to be inspected is attached to and detached from the master connector 10, which causes a problem that the performance of the conventional master connector 10 deteriorates with use due to wear and deformation. In particular, a resin MT ferrule is designed so that the inner diameter of the guide hole is slightly smaller than the outer diameter of the guide pin, or is the same inner diameter. Therefore, when a resin MT ferrule is used in the master connector 10, the guide pin hole is easily worn and deformed, which causes the axial center of the guide pin to shift, resulting in a problem that the eccentricity of the fiber core is shifted and accurate inspection is not possible. Therefore, when the inspection result of the master connector 10 exceeds the allowable value or when the number of measurements reaches a predetermined number, the master ferrule 100 deteriorates, and it is necessary to interrupt the inspection and replace the master connector 10 with a new master ferrule 100 built in. In addition, since the bonding between the master ferrule 100 and the ferrule 500 to be measured is performed at the submicron level, careful and precise operation is required, but there is a problem in that the resin master ferrule 100 is easily damaged. Therefore, when an operator who performs a large number of tests performs the bonding operation roughly even once, the resin master ferrule 100 is damaged and accurate testing becomes impossible.

[0055] On the other hand, the master ferrule of this embodiment does not deform, and the connection loss remains unchanged with almost no performance degradation even when subjected to repeated stress accompanying attachment and detachment of the master connector 10 or a large spring force accompanying PC connection. Also, unlike a resin MT ferrule, the guide pin holes are less likely to wear even when the guide pins are repeatedly inserted and removed, so the positional accuracy of the fiber holes is ensured and there is almost no performance degradation. Furthermore, SUS and other alloys have accumulated die cutting processing technology, and it is possible to improve the processing accuracy of hole positions compared to resin molded products. In particular, since it is possible to cut the guide pin holes parallel with extremely high accuracy, the quality of the master connector 10 can be maintained even if the connection end surface is polished multiple times. Therefore, a more accurate evaluation can be performed by using it as a reference.

[0056] (Reference example) Although the master ferrule of this embodiment is made of stainless steel, it can be made of cemented carbide instead. In this case, the cemented carbide can be obtained by mixing tungsten carbide (WC) and cobalt (Co) and sintering the mixture. The physical properties of the cemented carbide, such as hardness, can be adjusted by the combination of the particle size of the tungsten carbide and the amount of added cobalt. Cemented carbide has extremely excellent abrasion resistance, so even if the MT ferrule to be measured is repeatedly inserted and removed, there is almost no deterioration in connection loss. In particular, the guide pins used in optical connectors are generally made of SUS303 (stainless steel), but cemented carbide is harder and more abrasion resistant than stainless steel, so it is less likely to wear out when inserting and removing the guide pin. In addition, cemented carbide can be processed using die cutting technology, so it is possible to achieve high accuracy in the positioning of the optical fiber insertion hole and the guide hole compared to resin molding. In addition, cemented carbide is less dependent on the environment and is less susceptible to corrosion such as rust, so it can be used as a reference for accurate evaluation over a long period of time.

[0057] (Example) An optical fiber made of quartz was inserted into the master ferrule 100 of this embodiment, and was subjected to 8° oblique protrusion polishing using an optical connector polisher (ATP-3200 manufactured by NTT-AT) in the same manner as for a normal PPS MT ferrule. FIG. 4 is a micrograph of the connection end face of the master ferrule 100 obtained in the example. In the master ferrule of the embodiment, the eccentricity of the fiber core was 0.5 μm or less. In addition, as shown in FIG. 3, even when the master ferrule of the embodiment was incorporated into an MPO connector and subjected to repeated insertion / removal tests (IEC61300-2-2), it was confirmed that the connection loss was 0.5 dB or less, posing no problem.

[0058] In the present invention, master ferrule 100 corresponds to the "master ferrule", ferrule body 110 corresponds to the "ferrule body", optical fiber insertion hole 112 corresponds to the "optical fiber insertion hole", guide hole 111 corresponds to the "guide hole", boot insertion hole 121 corresponds to the "boot insertion hole", flange portion 120 corresponds to the "flange portion", master connector 10 corresponds to the "master connector", and ferrule 500 to be measured corresponds to the "ferrule".

[0059] Although the preferred embodiment of the present invention is as described above, the present invention is not limited thereto. It is understood that various other embodiments can be made without departing from the spirit and scope of the present invention. Furthermore, although the actions and effects of the configuration of the present invention are described in the present embodiment, these actions and effects are merely examples and do not limit the present invention. [Explanation of symbols]

[0060] 10 Master Connector 100 Master Ferrule 101 Connection end face 102 Rear end surface 110 Ferrule body 111 Guide hole 112 Optical fiber insertion hole 113 Reduced diameter part 114 Guide groove 115 Window 116 Interior Space 120 Flange 121 Boot insertion hole 200 Boots 300,300' Optical Fiber 400 Guide pin 500 Ferrules (measurement target)

Claims

1. A master ferrule for inspecting a resin ferrule, comprising: an optical fiber insertion hole for inserting an optical fiber, a guide hole for inserting a guide pin, a boot insertion hole for inserting a ferrule boot having a plurality of optical fibers inserted therethrough, and a flange portion protruding from a ferrule body; A master ferrule formed in one piece from stainless steel containing iron and chromium.

2. 2. The master ferrule of claim 1, wherein the stainless steel contains iron, chromium and nickel and has a Vickers hardness of 500 or less.

3. the optical fiber inserted into the optical fiber insertion hole; a ferrule boot through which the optical fiber is inserted; 2. The master ferrule according to claim 1, wherein the optical fiber is fixed in the optical fiber insertion hole with a thermosetting resin.

4. 13. A master connector, comprising: a master ferrule according to claim 1 used in a connecting portion, capable of optically connecting with said resin ferrule.

5. 13. An inspection device, comprising: the master ferrule according to claim 1 used in a connection portion; and capable of inspecting the performance of the resin ferrule.

6. 2. A method for producing a master ferrule according to claim 1, comprising the steps of: The optical fiber insertion hole and the guide hole are formed by cutting.

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