Optical connector and assembly method for optical connector

Abstract

[Problem] To provide an optical connector and an assembly method for the optical connector that make it possible to achieve easy, highly accurate assembly while also preventing an increase in component count and simplifying structure and assembly. [Solution] An optical connector (1) is formed from at least a lens (5), a lens sleeve (2) that holds the lens, and a ferrule (4) into which an optical fiber (3) is inserted. The lens has a convex part (5a), and the lens sleeve has a taper part (2a). In a cross-section of the lens and the lens sleeve, the convex part is in point contact with the surface of the taper part at a plurality of locations (C) but does not otherwise contact the lens sleeve, and the lens is at a gap from the lens sleeve except at the plurality of locations. An assembly method for the optical connector (1) involves inserting the lens (5) into the lens sleeve (2) such that the convex part (5a) is in point contact with the taper part (2a) at the plurality of locations (C) but does not otherwise contact the lens sleeve and such that a gap is formed between the lens and the lens sleeve except at the plurality of locations.

Description

Optical connector and method for assembling the same

[0001] The present invention relates to an optical connector and a method for assembling an optical connector.

[0002] An optical connector is configured to include a ferrule into which an optical fiber is inserted and at least one lens (see, for example, Patent Document 1 or Patent Document 2).

[0003] Figure 2 of Patent Document 1 discloses an optical connector with a focusing lens in which the spherical surface of the lens is pressed against a tapered annular lens receiving seat surface by a compression spring, and the tapering action of the annular lens receiving seat surface allows the lens to be automatically centered and held in a fixed position.

[0004] FIG. 1 of Patent Document 2 discloses an expanded beam type optical fiber connector in which the compression of a sealing O-ring generates an elastic force that pushes the sleeve, ferrule, spacer plate, and lens toward the edge of the body, resulting in strong physical contact.

[0005] Japanese Utility Model Application Publication No. 60-070807 Japanese Patent No. 2795539

[0006] However, the optical connector with a focusing lens described in Patent Document 1 requires a compression spring, and the optical fiber connector described in Patent Document 2 requires a sealing O-ring (elastic pressure member) in order to press the lens, in addition to the components that make up the optical connector body.

[0007] This leads to an increase in the number of parts, and the increased number of parts also leads to a more complicated structure and assembly of the optical connector.

[0008] The present invention has been made in consideration of the above-mentioned problems, and aims to provide an optical connector and an optical connector assembly method that can be easily assembled with high precision while preventing an increase in the number of parts and simplifying the structure and assembly.

[0009] The above-mentioned problems are solved by the present invention as follows: That is, the optical connector of the present invention is an optical connector comprising at least a lens, a lens sleeve that holds the lens, and a ferrule into which an optical fiber is inserted, wherein the lens has a convex portion, the lens sleeve has a tapered portion, and in a cross-sectional state of the lens and the lens sleeve, multiple points of the convex portion are in point contact with the surface of the tapered portion, the convex portion other than the multiple points that are in point contact is not in contact with the lens sleeve, and the lens other than the multiple points has a gap with respect to the lens sleeve.

[0010] Furthermore, the method of assembling an optical connector of the present invention is characterized in that a lens having a convex portion is inserted into a lens sleeve having a tapered portion, and in the cross-sectional state of the lens and lens sleeve, multiple points of the convex portion are brought into point contact with the surface of the tapered portion, while the convex portion other than the multiple points of point contact is not brought into contact with the lens sleeve, and gaps are formed between the lens and the lens sleeve other than the multiple points.

[0011] According to the optical connector or the method for assembling the optical connector of the present invention, there is no need for an additional part for pressing the lens, in addition to the parts that make up the optical connector body. Therefore, it is possible to prevent an increase in the number of parts, and it is also possible to simplify the structure and assembly of the optical connector. Furthermore, as the assembly is simplified, high-precision assembly becomes possible easily.

[0012] 5(a)-5(c) are side views of optical connectors according to embodiments and examples of the present invention.

[0034] FIG. 1 is a cross-sectional side view taken along the dashed line (AA) of FIG. 1.

[0035] FIG. 3 is a cross-sectional side view taken along the dashed line (BB) of FIG. 3. (a) is a front view of a lens sleeve constituting the optical connector of FIG. 1. (b) is a right side view of the lens sleeve of FIG. 5(a). (c) is a rear view of the lens sleeve of FIG. 5(a). (B) is a cross-sectional side view taken along the dashed line (EE) of FIG. 5(b). (a) is a cross-sectional side view showing an assembly process of the optical connector of FIG. 1, and is a cross-sectional side view showing a process of inserting a lens into an insertion hole of the lens sleeve. (b) is a cross-sectional side view showing a process of inserting a lens into an insertion hole of the lens sleeve from the state of FIG. 7(a), and then inserting a ferrule with an optical fiber inserted into the insertion hole into the insertion hole. (c) is a cross-sectional side view showing a state in which a ferrule has been inserted into the insertion hole of the lens sleeve from the state of FIG. 7(b).

[0036] FIG. 7(b) is a cross-sectional side view showing a partially enlarged enlargement of the circled D portion of FIG. 7(b). Fig. 7 is a partially enlarged side cross-sectional view of the circled portion F in Fig. 6. Fig. 8 is a perspective view showing a state in which the point contact points C with the lens sleeve extend over 360° on the curved surface of the convex portion of the lens shown in Fig. 3.

[0013] The first feature of this embodiment is that the optical connector is composed of at least a lens, a lens sleeve that holds the lens, and a ferrule into which an optical fiber is inserted, the lens having a convex portion and the lens sleeve having a tapered portion, and in the cross-sectional state of the lens and the lens sleeve, multiple points of the convex portion are in point contact with the surface of the tapered portion, and the convex portion other than the multiple points that are in point contact is not in contact with the lens sleeve, and the lens other than the multiple points has a gap with respect to the lens sleeve.

[0014] The second feature is an optical connector in which a curved surface is formed on the convex portion, the cross section of the tapered portion is linear and formed over 360°, and multiple points are formed over 360° on the curved surface.

[0015] The third feature is that the corners of the tapered portion are not rounded, and the convex portion does not contact the corners.

[0016] The fourth feature is an optical connector in which the optical axis of the lens coincides with the central axis of the lens sleeve.

[0017] The fifth feature is a method for assembling an optical connector in which a lens having a convex portion is placed into a lens sleeve having a tapered portion, and in the cross-sectional state of the lens and the lens sleeve, multiple points of the convex portion are brought into point contact with the surface of the tapered portion, while the convex portion other than the multiple points where they are in point contact is not brought into contact with the lens sleeve, and gaps are formed between the lens and the lens sleeve other than the multiple points.

[0018] The sixth feature is a method for assembling an optical connector in which a curved surface is formed on the convex portion, and the cross section of the tapered portion is formed linearly over 360°, with multiple locations extending over 360° on the curved surface.

[0019] The seventh feature is an optical connector assembly method in which the corners of the tapered portion are not rounded and the protrusion does not come into contact with the corners.

[0020] The eighth feature is an assembly method for an optical connector in which the optical axis of the lens and the central axis of the lens sleeve are aligned.

[0021] These configurations and methods eliminate the need for additional parts to press the lens, in addition to the parts that make up the optical connector body. This prevents an increase in the number of parts, and simplifies the structure and assembly of the optical connector. Furthermore, the simplification of assembly makes it possible to easily perform high-precision assembly.

[0022] Hereinafter, an embodiment of the present invention will be described in detail with reference to Figures 1 to 10. The same components shown in the various drawings are designated by the same reference numerals, and duplicated descriptions will be omitted where appropriate.

[0023] As shown in FIGS. 1 and 2, the optical connector 1 according to this embodiment is composed of at least a lens 5, a lens sleeve 2 that holds the lens 5, and a ferrule 4 into which an optical fiber 3 is inserted.

[0024] 3 and 4, the lens 5 is manufactured by integral molding so as to have a convex portion 5a that functions as a convex lens and a body portion 5b. The entire convex portion 5a has a curved surface and is formed into a convex lens shape. The curved shape of the convex portion 5a is formed line-symmetrically over 360° with respect to the optical axis X5 of the lens 5. The body portion 5b is molded into a cylindrical shape with flat chamfered upper and lower portions.

[0025] The lens 5 is produced by molding. To facilitate the removal of the molded lens 5 from the mold during molding, a taper may be formed in part of the outer shape of the body 5b as shown in FIG.

[0026] Examples of materials for the lens 5 include cycloolefin copolymer (COC), cycloolefin polymer (COP), polycarbonate (PC), poly methyl methacrylate (PMMA), polyetherimide (PEI), silicone, and glass.

[0027] The curved surfaces of the protrusions 5a are mirror-finished, with a root mean square (Sq) of 30 μm or less. Furthermore, the curved surfaces of the protrusions 5a are coated with an AR coating made of SiO2.

[0028] The body end surface 5c of the lens 5 is formed so as to be perpendicular to the optical axis X5.

[0029] As shown in Figures 5 and 6, the lens sleeve 2 has a cylindrical outer shape and is configured with a cylindrical shape consisting of two stages with different outer diameters. As shown in Figure 5(b), the left side view of the lens sleeve 2 is symmetrical to the right side view. Furthermore, the top view and bottom view of the lens sleeve 2 appear to have the same shape as the right side view.

[0030] 5(a), 6, and 9, a light propagation hole 2c is formed at one end of the lens sleeve 5. An insertion hole 2d is provided that is continuous with the light propagation hole 2c and extends along the central axis X2 of the lens sleeve 2 to the opposite end.

[0031] Furthermore, the lens sleeve 2 has a tapered portion 2a. The light propagation hole 2c and the insertion hole 2d are integrally molded so as to be connected via the tapered portion 2a. As shown in Figures 6 and 9, the cross section of the tapered portion 2a is formed in a linear, conical shape over 360°. Furthermore, at the connecting portion between the light propagation hole 2c and the tapered portion 2a, a corner portion 2b is formed circumferentially over 360°.

[0032] 2 and 8, in a cross-sectional view, the lens 5 and lens sleeve 2 are in point contact with the surface of the tapered portion 2a at at least two or more points on the convex portion 5a. In Fig. 8, the point contact points between the lens 5 and the tapered portion 2a are indicated by the symbol C. By having at least two points of point contact, the lens 5 can be stably contacted and held on the tapered portion 2a. Therefore, contact between the convex portion 5a and the lens 5 and the lens sleeve 2 at points other than the multiple points of point contact is prevented, preventing damage to the lens 5.

[0033] The curved surface of the convex portion 5a and the tapered portion 2a can be molded into any shape as long as they can make point contact with each other. Therefore, the convex portion 5a may be molded into a curved surface only at the point where it makes point contact with the tapered portion 2a. The cross-sectional shape of the tapered portion 2a is not limited to a linear shape as long as it can make point contact with the convex portion 5a. However, from the perspective of ease of molding the lens sleeve 2 and the convex portion 5a, it is desirable that the cross section of the tapered portion 2a be linear and that the entire convex portion 5a be molded into a convex lens-like curved surface, as shown in Figures 3, 4, 6, and 8.

[0034] When the entire surface of the convex portion 5a is curved like a convex lens, the radius of curvature R of the curved surface is 0.52 mm to 0.58 mm. The diameter of the body portion 5b is 1.22 mm (+0.015 mm / -0.025 mm). The taper angle of the tapered portion 2a with respect to the central axis X2 is 98° to 102°.

[0035] The lens sleeve 2 can be made of SUS303 or SUS304. The lens sleeve 2 can be manufactured by machining. Other methods for manufacturing the lens sleeve 2 include deep drawing, metal injection molding (MIM), and electroforming.

[0036] When the lens 5 is inserted inside the lens sleeve 2, no part of the lens 5, including the convex portion 5a, other than the multiple points of the convex portion 5a that are in point contact with the tapered portion 2a, is in contact with the lens sleeve 2. Therefore, the lens 5 other than the multiple point contact points C has a gap with the tapered portion 2a and insertion hole 2d of the lens sleeve 2. As described above, even if a taper is provided on part of the body portion 5b, the lens 5 has a gap with the tapered portion 2a and insertion hole 2d other than the multiple point contact points C.

[0037] As shown in Figure 9, the corners 2b of the lens sleeve 2 are not rounded. The corners 2b may be rounded or left as they are. However, in the optical connector 1 of this embodiment, the diameter of the maximum diameter of the tapered portion 2a (i.e., the diameter of the insertion hole 2d) is a very small dimension of 1.241 mm to 1.251 mm. Therefore, if the corners were rounded, the tapered portion 2a near the corners 2b would be scraped off, potentially eliminating the point contact with the protrusions 5a. Therefore, it is desirable that the corners 2b not be rounded. Furthermore, as shown in Figure 8, when the protrusions 5a are in point contact with the tapered portion 2a at multiple point contact locations C, the protrusions 5a do not contact the corners 2b.

[0038] The ferrule 4 is circular, has a through-hole in the center for inserting the optical fiber 3, and is made of ceramics such as zirconia.

[0039] The outer diameter of the ferrule 4 is set slightly larger than the diameter of the insertion hole 2d of the lens sleeve 2. Specifically, the outer diameter of the ferrule 4 and the insertion hole 2d are set so that the ferrule 4 can be inserted into and fitted into the insertion hole 2d with the optical fiber 3 inserted. Therefore, the diameter of the insertion hole 2d is set slightly smaller than the outer diameter of the ferrule 4, and larger than the diameter of the body portion 5b so that the lens 5 can be inserted therein.

[0040] 2, the end face 4a (see FIG. 7(b)) of the ferrule 4 on the side inserted into the insertion hole 2d and the end of the optical fiber 3 are formed so as to be perpendicular to the central axis of the ferrule 4 and the core axis of the optical fiber 3. Furthermore, the end of the optical fiber 3 is inserted into the ferrule 4 so as to be flush with the end face 4a of the ferrule 4.

[0041] Furthermore, the vicinity of the end face 4a of the ferrule 4 is formed in a tapered shape so that it can be easily fitted into and inserted into the insertion hole 2d.

[0042] The optical fiber 3 is a graded-index multimode optical fiber with a core diameter of 50 μm and a propagation wavelength of 850 nm or 1300 nm. In order to prioritize ease of viewing, hatching is omitted from the cross-sectional views of the optical fiber 3 in Figures 2 and 7.

[0043] 1 and 2 is configured such that the optical axis X5 of the lens 5 coincides with the central axis X2 of the lens sleeve 2. As described above, the body end face 5c of the lens 5 is formed so as to be perpendicular to the optical axis X5, and the end face 4a of the ferrule 4 is formed so as to be perpendicular to the central axis of the ferrule 4. Therefore, the optical connector 1 is configured such that the body end face 5c and the end face 4a are in surface contact with each other.

[0044] The light emitted from the optical fiber 3 is expanded or converged by the lens 5 before being emitted.

[0045] Next, we will explain the method of assembling the optical connector 1. As shown in Figure 7(a), first, the lens 5 having the convex portion 5a is inserted into the insertion hole 2d of the lens sleeve 2 having the tapered portion 2a.

[0046] Since the lens 5 is inserted into the insertion hole 2d from the convex portion 5a side, the lens 5 is inserted until the surface of the convex portion 5a makes point contact with the tapered portion 2a. Therefore, as shown in Figures 7(b) and 8, in the cross-sectional state of the lens 5 and the lens sleeve 2, the convex portion 5a makes point contact with the surface of the tapered portion 2a at at least two or more points. However, other than the multiple point contact points C, the parts of the lens 5 including the convex portion 5a do not make contact with the tapered portion 2a of the lens sleeve 2 or the insertion hole 2d. Therefore, it is assumed that a gap is formed between the lens 5 and the lens sleeve 2 other than the point contact points C.

[0047] In a preferred embodiment, the cross section of the tapered portion 2a is linear and formed into a conical surface over 360°, and the convex portion 5a is formed into a curved surface like a convex lens over the entire surface. Therefore, the point contact between the tapered portion 2a and the convex portion 5a is formed into a curved shape over 360° on the curved surface of the convex portion 5a as shown in Figure 10, and the contact state between the tapered portion 2a and the convex portion 5a is maintained. In addition, no part of the convex portion 5a should come into contact with the corner portion 2b.

[0048] Next, as shown in Figures 7(b) and 7(c), the ferrule 4 with the optical fiber 3 inserted therein is mated and inserted into the insertion hole 2d, and the end face 4a of the ferrule 4 is pressed against the body end face 5c of the lens 5, so that the convex portion 5a is pressed against the tapered portion 2a.

[0049] A desirable configuration is one in which the ferrule end face 4a is formed perpendicular to the central axis of the ferrule 4, and the barrel end face 5c of the lens 5 is formed perpendicular to the optical axis X5. A more desirable configuration is one in which the cross section of the tapered portion 2a is formed linearly and conically over 360°. Therefore, with the barrel end face 5c and the end face 4a in surface contact, the end face 4a presses the barrel end face 5c and the convex portion 5a of the lens 5 uniformly over 360° against the tapered portion 2a. The tapered shape of the tapered portion 2a then positions the lens 5 at the center of the lens sleeve 2. Even if the lens 5 moves within the lens sleeve 2 during this positioning, the lens 5 does not contact the lens sleeve 2 except at multiple point contact locations C on the convex portion 5a, and a gap is formed between the lens 5 and the lens sleeve 2 at locations other than the point contact locations C.

[0050] 7(c), when the insertion of the ferrule 4 into the insertion hole 2d is completed, the optical axis X5 of the lens 5 and the central axis X2 of the lens sleeve 2 are aligned coaxially, and the alignment of the lens 5 and the lens sleeve 2 is automatically completed. Therefore, the optical connector 1 can be assembled with high precision.

[0051] Even after the alignment work is complete, a gap remains between the lens 5 and the lens sleeve 2, except for point contact location C, and no part of the convex portion 5a or lens 5 other than point contact location C comes into contact with the tapered portion 2a or insertion hole 2d of the lens sleeve 2. Furthermore, the point contact location between the tapered portion 2a and the convex portion 5a is formed in a curved shape over 360° on the curved surface of the convex portion 5a, as shown in Figure 10, so that the contact state between the tapered portion 2a and the convex portion 5a is maintained. Additionally, no part of the convex portion 5a comes into contact with the corner 2b.

[0052] One advantage of configuring the outer shape of the lens sleeve 2 as a cylinder with two different outer diameters is that the relatively thin outer diameter portion makes it possible to appropriately control the insertion / removal force of the LC ferrule. When an LC ferrule is inserted into the insertion hole 2d as the ferrule 4, the lens sleeve 2 deforms to open toward the outer diameter side, so the lens sleeve 2 has a relatively thin outer diameter portion to prevent the outer diameter from becoming too large due to this deformation. More specifically, the relatively thin outer diameter portion is formed to match the inner diameter of the SC sleeve so that the outer diameter of the lens sleeve 2 does not become larger than the designed outer diameter value.

[0053] As described above, according to the optical connector 1 and its assembly method according to this embodiment, there is no need for an additional part for pressing the lens 5, in addition to the parts that make up the main body of the optical connector 1. This makes it possible to prevent an increase in the number of parts, and to simplify the structure and assembly of the optical connector 1. Furthermore, the simplification of the assembly makes it possible to easily assemble the optical connector 1 with high precision.

[0054] Furthermore, by forming a curved surface on the convex portion 5a and forming the cross section of the tapered portion 2a linearly and over 360°, and by providing multiple point contact points C between the convex portion 5a and the tapered portion 2a over 360° on the curved surface of the convex portion 5a as shown in FIG. 10, the contact state between the lens 5 and the lens sleeve 2 can be more reliably ensured. Therefore, the optical connector 1 can be assembled with higher precision. Furthermore, by providing point contact points C over 360° on the curved surface of the convex portion 5a, the lens 5 can be stably contacted and held by the tapered portion 2a. Therefore, contact between the convex portion 5a and the lens 5 other than at the point contact points C and the tapered portion 2a and insertion hole 2d of the lens sleeve 2 is prevented, and damage to the lens 5 during insertion and alignment can be more reliably prevented. Furthermore, while allowing the convex portion to make point contact with the lens sleeve 2, the point contact location C is curved and is brought into point contact with the surface of the tapered portion 2a, thereby making the convex portion 5a shock-resistant, and therefore, damage to the lens 5 can be more reliably prevented.

[0055] Furthermore, the AR coating applied to the curved surface of the protrusion 5a also serves to prevent damage to the protrusion 5a.

[0056] Furthermore, the corners 2b of the tapered portion 2a are not rounded, and the convex portion 5a does not come into contact with the corners 2b, thereby simplifying the structure and manufacturing process of the lens sleeve 2. Furthermore, even if the corners 2b are not rounded, contact with the lens 5 can be prevented, preventing damage to the convex portions 5a and corners 2b.

[0057] Examples of the present invention will be described below, but the present invention is not limited to only the following examples.

[0058] The optical connector and its assembly method in this embodiment are the optical connector 1 and its assembly method shown in Figures 1 to 10. Through verification by the applicant, the radius of curvature R of the curved surface of the convex portion 5a was set to 0.55 mm, the diameter of the body portion 5b to 1.22 mm (+0.015 mm / -0.025 mm), the taper angle of the tapered portion 2a with respect to the central axis X2 to 98° to 102°, and the diameter of the insertion hole 2d to 1.241 mm to 1.251 mm.

[0059] When the optical connector 1 according to this embodiment was observed after assembly, it was confirmed that it was possible to make the point contact locations C extend over 360° on the curved surface of the convex portion 5a, as described above.

[0060] Furthermore, it was confirmed that contact between the corner 2b and the lens 5 was prevented.

[0061] Furthermore, a gap is formed between the convex portion 5a and the lens 5 and the tapered portion 2a and insertion hole 2d of the lens sleeve 2 except at the point contact point C, and it was confirmed that damage to the lens 5 was prevented when inserting and centering the lens 5.

[0062] REFERENCE SIGNS LIST 1 Optical connector 2 Lens sleeve 2a Tapered portion of lens sleeve 2b Corner portion of lens sleeve 2c Light transmission hole of lens sleeve 2d Insertion hole of lens sleeve 3 Optical fiber 4 Ferrule 4a End face of ferrule 5 Lens 5a Convex portion of lens 5b Body portion of lens 5c End face of body portion of lens C Point contact location X2 Central axis of lens sleeve X5 Optical axis of lens

Claims

1. An optical connector comprising at least a lens, a lens sleeve that holds the lens, and a ferrule into which an optical fiber is inserted, wherein the lens has a convex portion, the lens sleeve has a tapered portion, and in the cross-sectional state of the lens and the lens sleeve, multiple points of the convex portion are in point contact with the surface of the tapered portion, and the convex portion other than the multiple points that are in point contact is not in contact with the lens sleeve, and the lens other than the multiple points has a gap from the lens sleeve.

2. An optical connector according to claim 1, wherein a curved surface is formed on the convex portion, the cross section of the tapered portion is linear and extends over 360°, and the multiple locations extend over 360° on the curved surface.

3. An optical connector according to claim 1 or 2, wherein the corners of said tapered portion are not rounded and said convex portion does not contact the corners.

4. The optical connector according to claim 1, wherein the optical axis of said lens and the central axis of said lens sleeve coincide with each other.

5. A method of assembling an optical connector in which a lens having a convex portion is inserted into a lens sleeve having a tapered portion, and in the cross-sectional state of the lens and lens sleeve, multiple points of the convex portion are brought into point contact with the surface of the tapered portion, while the convex portion other than the multiple points of point contact is not brought into contact with the lens sleeve, and gaps are formed between the lens and the lens sleeve other than the multiple points.

6. A method for assembling an optical connector according to claim 5, wherein a curved surface is formed on the convex portion, the cross section of the tapered portion is formed linearly over 360°, and the multiple locations are arranged over 360° on the curved surface.

7. A method for assembling an optical connector according to claim 5 or 6, wherein the corners of the tapered portion are not rounded and the protrusion does not come into contact with the corners.

8. The method for assembling an optical connector according to claim 5, wherein the optical axis of the lens and the central axis of the lens sleeve are aligned.

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