JP4038163B2 - Optical receptacle - Google Patents

Description

The present invention relates to a receptacle used for an optical communication module or the like.

  An optical module for converting an optical signal into an electrical signal has a structure in which an optical element such as a semiconductor laser or a photodiode is housed in a case, and the optical signal is introduced or derived through an optical fiber (Patent Document). 1).

  A receptacle-type optical module in which a connector is connected among the above optical modules includes an optical element 22 at one end of an optical receptacle 14 as shown in FIG. 3, and a plug ferrule of an optical connector (SC connector) at the other end. 15 is connected.

  As shown in FIG. 3, the optical receptacle 14 includes a ferrule 17 made of a ceramic material such as zirconia or alumina, and a fiber stub obtained by inserting and fixing an optical fiber 18 made of quartz glass or the like in a through hole of the ferrule 17. The rear end of 16 is fixed to the holder 20 by press-fitting, the front end is inserted into the inner hole of the sleeve 19, and they are press-fitted or adhesively fixed to the sleeve case 21.

  In recent years, miniaturization of optical modules has been demanded due to the demand for high-density mounting, and the total length of optical receptacles has also been required to be shortened. In addition, a smaller connector such as an SC connector or an LC connector is used as a connector connected to the optical receptacle. Therefore, as shown in FIG. 4, a fiber stub 16 in which an optical fiber 18 is inserted and fixed in a through hole of the ferrule 17, a sleeve 19 for holding a plug ferrule 15 connected to the front end surface of the fiber stub 16, an outer periphery of the sleeve end An optical receptacle 26 comprising a grip ring 25 that constrains the free deformation of the sleeve end that is press-fitted into the sleeve has been devised. Even if the length L2 of the fiber stub 16 held by the sleeve 19 is shortened by press-fitting the grip ring 25 to the outside of the sleeve holding the fiber stub 16, and restraining the free deformation of the sleeve 19, it is sufficient. A strong holding force of the fiber stub 16 is obtained (see Patent Document 2).

  When an optical module is configured using the optical receptacle 26 described above, a case 24 having an optical element 22 and a lens 23 is welded to the rear end surface side of the optical receptacle 26 having the fiber stub 16 as shown in FIG. Thus, the plug ferrule 15 is inserted into the sleeve 19 from the other end face side of the optical receptacle 26, and the end face of the optical fiber is brought into contact with each other to exchange optical signals.

At this time, the outer diameter of the ferrule 17 is that of an SC connector type.
About 2.5mm, small type connecting LC connector is about φ1.25mm, outer diameter tolerance is ± 1μm or less, outer diameter of optical fiber 18 provided in its through hole is about 125μm, outer diameter The tolerance is about ± 1 μm, which is defined by JIS and IEC standards. Conventionally, cores (not shown) with a diameter of about 10 μm that propagate the optical signal formed at the center of the optical fiber 18 have little loss. Each component (sleeve 19, ferrule 17, etc.) is processed with high precision for connection, and the sleeve 19 holds the fiber stub 16 and the plug ferrule 15 stably and with high precision.

Further, the end face of the optical fiber 18 in the fiber stub 16 is mirror-polished to a curved surface having a curvature radius of about 5 to 30 mm in order to reduce connection loss at the time of contact, and the opposite end face is an optical element such as an LD. In order to prevent the light emitted from the optical fiber 18 from being reflected at the tip of the optical fiber 18 and returning to the optical element, it is mirror-polished to an inclined surface of about 4 to 10 ° together with the ferrule 17 inserted through the optical fiber 18. Yes.
JP 2001-66468 A Japanese Patent No. 3314667

However, in the case of the conventional optical receptacle 14 shown in FIG. 3, when the dimension is changed from the φ2.5 mm ferrule of the SC connector to the φ1.25 mm ferrule of the LC connector in order to meet the demand for miniaturization, the outer diameter of the ferrule becomes small. Accordingly, the outer diameter area of the ferrule is reduced to about 1/2, so that the fiber stub fixing method similar to the conventional method, for example, the length L3 where the fiber stub is fixed to the holder, the outer diameter D of the fiber stub 16, and the holder 20 If the relationship between the inner diameter D1 of the fiber stub fixing part is applied as it is, the contact area between the holder 20 and the fiber stub 16 is greatly reduced, so that the fixing strength becomes very small, and the fiber stub 16 moves when the optical connector is connected. As a result, there is a problem that the reproducibility of the connection loss is deteriorated.

  Further, in the case of the optical receptacle 26 as shown in FIG. 4, since the grip ring 25 restrains the free deformation of the sleeve 19, the deformation of the sleeve 19 when the plug ferrule 15 is inserted into and removed from the sleeve 19 is uneven. As a result, the insertion force and the removal force become unstable, and there is a problem that the detachability is deteriorated.

  Further, since the length L2 of the fiber stub 16 held by the sleeve 19 is shortened, the fiber stub 16 is held in an unstable state, and the fiber stub 16 is held by the sleeve 19 each time the plug ferrule 15 abuts. There was a problem that the state was different and the reproducibility of the connection loss was deteriorated.

  In recent years, the plug ferrule 15 has been given importance to the characteristics of insertion loss fluctuation and reflection attenuation fluctuation (uiggle characteristics) with respect to a load extending in a direction perpendicular to the optical axis. When the length L2 is shortened, this wiggle characteristic is deteriorated.

  Furthermore, since the holding state is unstable, there is a problem that slippage occurs between the optical fiber connecting portions, and the end face of the optical fiber 18 may be scratched, making it impossible to introduce and derive optical signals.

In view of the above, the optical receptacle of the present invention excludes a fiber stub in which an optical fiber is inserted and fixed into a through-hole of a ferrule, a holder that fixes the rear end of the fiber stub, and a rear end of the fiber stub A sleeve inserted into the part, and the sleeve has a thick portion formed at one end where the fiber stub is inserted, thereby increasing the holding force per unit length of the fiber stub. It is a featured optical receptacle.

  Furthermore, the step length of the portion having a large outer diameter in the sleeve is shorter than the insertion length of the fiber stub into the sleeve.

  Furthermore, the optical receptacle of the present invention is characterized in that the fiber stub is fixed to the holder by bonding or by a combination of press-fitting and bonding.

  An optical module of the present invention includes the optical receptacle of the present invention, an optical element and a lens, and a case welded to the holder.

According to the optical receptacle of the present invention, the rear end portion of the fiber stub in which the optical fiber is inserted and fixed into the through-hole of the ferrule is fixed to the holder, and the sleeve for holding the plug ferrule connected to the front end surface of the fiber stub is provided. In the optical receptacle that holds the tip of the fiber stub, a thick portion is formed at one end of the sleeve, and the fiber stub is inserted and held on the thick portion side, so that the unit length of the fiber stub is The holding power is increased, the C surface or R of the plug ferrule insertion side fiber stub is controlled to 0.1 mm or less, and no stress is applied to the sleeve from the outside other than the stress due to the fiber stub insertion. The receptacle keeps the fiber stub stable even if the fiber stub sleeve is short. Since the holding state of the fiber stub 3 by the sleeve 4 does not differ every time the plug ferrule is connected, high connection loss reproducibility is obtained, and furthermore, since the holding state is stable, It is possible to improve reliability in introducing and deriving an optical signal without causing slippage between the optical fiber connecting portions and without damaging the end face of the optical fiber.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an embodiment of an optical receptacle 7 of the present invention. A fiber stub 1 in which an optical fiber 3 is inserted and fixed to a ferrule 2 and a holder 5 for fixing a rear end portion of the fiber stub 1 are shown. And a sleeve case 6 and a sleeve 4 for holding the plug ferrule 10 connected to the tip end face of the fiber stub, and the tip of the fiber stub 1 is inserted and held in the sleeve 4.

  As shown in FIG. 1, the sleeve 4 used at this time is processed to have a stepped outer diameter at the end on the side where the fiber stub 1 is inserted and held, and the wall thickness is the thickness of the portion holding the plug ferrule 10. A thicker portion 4a that is larger is formed. Thereby, the retention strength of the thick part 4a can be increased.

  The thickness of the thick part 4a is preferably 1.5 to 2.5 times that of the other parts. This is because if the thicker portion 4a is thinner than this, sufficient fiber stub cannot be held, and if it is thicker than this, the sleeve 4 is broken due to increased stress and the insertion force of the plug ferrule 10 becomes difficult to insert. This is because there is a fear of becoming.

  The length L4 of the thick portion 4a is preferably in the range of 4/5 to 1/5 of the insertion length L2 of the fiber stub 1. This is because when the length L4 is longer than the above range, it becomes difficult to insert the plug ferrule 10, and when it is shorter than that, the holding power of the fiber stub becomes insufficient.

  By setting the thick portion 4a within the above range, a sufficient holding force can be obtained even if the holding portion of the fiber stub 1 is short, and the insertion force on the plug ferrule 10 side can be managed to an appropriate level.

  As for the formation of the thick portion 4a, in addition to the above, a tapered shape as shown in FIG. 2 (a), a curved shape as shown in FIG. 2 (b), or a separate member as shown in FIG. You may form by covering.

The ferrule 2 constituting the fiber stub 3 is made of a metal such as stainless steel or phosphor bronze, an epoxy, a plastic such as a liquid crystal polymer, or a ceramic such as alumina or zirconia, and is preferably formed of zirconia ceramic. Specifically, partial stabilization mainly comprising tetragonal crystals, containing ZrO ₂ as a main component, at least one of Y ₂ O ₃ , CaO, MgO, CeO ₂ , Dy ₂ O _{3 and the} like as a stabilizer. Zirconia ceramics are preferably used, and such partially stabilized zirconia ceramics are advantageous in fixing by press-fitting because they have excellent wear resistance and moderate elastic deformation.

  As a processing method of the ferrule 2, first, when the ferrule 2 is formed from, for example, zirconia ceramics, a cylindrical or cuboid shaped body that becomes the ferrule 2 by a predetermined molding method such as injection molding, press molding, extrusion molding or the like in advance. After that, the molded body is fired at 1300 to 1500 ° C. and subjected to cutting or polishing to a predetermined dimension. Note that a predetermined shape may be formed in advance on the formed body by cutting or the like, and then fired.

  The end surface 8 at the tip of the fiber stub 3 is processed into a curved surface having a radius of curvature of about 5 to 30 mm in order to reduce the connection loss with the optical connector, and the end surface 9 is formed by the light emitted from an optical element such as an LD. 3 is mirror-polished to an inclined surface of about 4 to 10 ° in order to prevent reflected light that is reflected by the end face of 3 and returns to the optical element. Further, the plug ferrule side C surface or R may be processed to 0.1 mm or less, or this chamfering may not be required.

  Further, the sleeve 4 is made of a material such as zirconia, alumina, or copper. It is often made of a ceramic material such as zirconia, mainly considering wear resistance. As a processing method, for example, when forming with a ceramic material such as zirconia, a cylindrical or columnar molded body that becomes the sleeve 4 is obtained in advance by a predetermined molding method such as injection molding, press molding, extrusion molding, and the like. The molded body is fired at 1300 to 1500 ° C. and cut or polished to a predetermined dimension to form the thick portion 4a. Note that a predetermined shape may be formed in advance on the formed body by cutting or the like, and then fired.

  In addition, the surface roughness of the inner diameter of the sleeve 4 is preferably an arithmetic average roughness (Ra) of 0.2 μm or less in consideration of the insertability, and the tolerance of the outer diameter of the fiber stub 1 and the inner diameter of the sleeve 4 is to obtain a low connection loss. The inner diameter of the sleeve 4 is preferably designed to have an insertion force of 0.98 N or more in order to securely hold the fiber stub 1.

  The fiber stub 1 is fixed to the holder 5 by press-fitting or bonding or by using both press-fitting and bonding.

  Furthermore, since the holder 5 is often welded to the case 24 (see FIG. 3) as an optical module, it is made of a material that can be welded, such as stainless steel, copper, iron, and nickel. Stainless steel is mainly used in consideration of corrosion resistance and weldability.

  Furthermore, since the sleeve case 6 does not need to consider wear resistance and weldability, a wide range of materials such as stainless steel, copper, iron, nickel, plastic, zirconia, and alumina are used. Stainless steel is often used in the same manner as the holder 5 in order to increase the reliability mainly by matching the thermal expansion coefficient with the holder 5.

  In the optical receptacle 7 of the present invention, since there is no grip ring that restrains the free deformation of the sleeve 4, when the plug ferrule 10 is inserted into or removed from the sleeve 4, the sleeve 4 can be freely deformed. The insertion force and removal force can be stabilized and good detachability can be obtained. In addition, the length of the fiber stub inserted into the sleeve can be shortened for shortening. That is, since the thickness of the fiber stub sleeve is increased, a sufficient holding force of the fiber stub sleeve can be obtained even if the insertion length of the fiber stub sleeve is short.

  In addition, the C-face or R on the plug ferrule side of the fiber stub is controlled to be 0.1 mm or less for the fiber stub so as to suppress the connection loss and the return loss fluctuation for the load perpendicular to the optical axis to the plug ferrule. Improves stability.

  Furthermore, since it is in a stable holding state, slippage does not occur in the optical fiber connecting portions, the end face of the optical fiber 3 is not damaged, and the reliability in introducing and deriving the optical signal can be improved.

  Examples of the present invention will be described.

(Experiment 1)
First, an optical receptacle shown in FIG. 1 as an example of the present invention and an optical receptacle shown in FIG. 4 as a comparative example were manufactured. The optical connector connected to the optical receptacle was an LC connector.

  In the sleeve for the optical receptacle of FIG. 1, the thickness of the thick portion 4a is twice that of the other portions, and the length L4 of the thick portion 4a is the insertion length of the fiber stub into the sleeve. It produced so that it might become 1/3 of L2.

  The ferrule used for each fiber stub is made of zirconia ceramics, a cylindrical ceramic molded body is obtained by extrusion molding, baked and hardened in a firing process, and cut to form a ferrule sample having the shape shown in FIG. 1 and FIG. A shaped ferrule sample was obtained.

  An optical fiber is inserted and fixed in the through hole of each ferrule obtained in this way, the tip end surface is mirror-polished to a curved surface with a curvature radius of about 20 mm, and the rear end on the opposite side is light emitted from an optical element such as an LD. In order to prevent the reflected light from being reflected at the tip of the optical fiber and returning to the optical element, mirror polishing was performed on an inclined surface of 8 ° to obtain a fiber stub.

  Then, the fiber stub obtained by inserting the tip end of the fiber stub into the sleeve is inserted into the metal fitting. In the case of the sample of the present invention of FIG. 1, the rear end side of the fiber stub is press-fitted into the holder. Then, a grip ring was press-fitted outside the sleeve, and finally an optical receptacle was fabricated by press-fitting the fiber stub, sleeve, and grip ring assembly into the sleeve case.

表１より明らかなように、本発明の光レセプタクルの挿入、抜去力は１．7８〜２．１０Ｎの範囲で安定しており、また接続損失も０．０２〜０．１２ｄＢの範囲で安定している。これに対し従来の光レセプタクルの挿入、抜去力は０．８４〜４．１５Ｎの範囲でバラツキが大きく、接続損失も０．０２〜０．６７ｄＢ
の範囲で再現性が悪いことがわかる。 Then, the plug ferrule of the optical connector was repeatedly inserted and removed from the tip side of each optical receptacle sample, the insertion / extraction force was measured with a push-pull gauge, and the connection loss was measured with a power meter.

As is apparent from Table 1, the insertion and extraction force of the optical receptacle of the present invention is stable in the range of 1.78 to 2.10 N, and the connection loss is stable in the range of 0.02 to 0.12 dB. ing. On the other hand, the insertion / extraction force of the conventional optical receptacle has a large variation in the range of 0.84 to 4.15 N, and the connection loss is also 0.02 to 0.67 dB.
It can be seen that the reproducibility is poor within the range.

表２から、今回実験にて作成した図１の光レセプタクルにおいてファイバスタブ長を図３のものより、23％削減したものにおいても、通常品と同様の特性が得られた。この際、ホルダへのファイバスタブの圧入代は同等とした。 (Experiment 2)
Next, with respect to the optical receptacle of FIG. 3 except for the sleeve and the fiber stub length, comparison was made with respect to the removal force, insertion loss, and insertion loss variation due to lateral load.

From Table 2, the same characteristics as those of the normal product were obtained even when the fiber stub length of the optical receptacle of FIG. 1 prepared in this experiment was 23% shorter than that of FIG. At this time, the press-fitting allowance of the fiber stub into the holder was made equal.

  Although we did not use the stepped sleeve as shown in Fig. 1, we tried to collect data on insertion loss and fluctuation in insertion loss when lateral load was applied in the structure of Fig. 3 with a fiber stub length reduced by 23%. The measurement value fluctuated so much that stable measurement was not possible. This represents the limit of shortening in the structure of FIG.

(Experiment 3)
Next, as shown in Fig. 6, the C surface 27 is processed like a normal ferrule on the plug ferrule connection side of the fiber stub (in the case of the LC connector, the length of the C surface of the fiber stub is about 0.3 to 0.4 mm) As shown in Fig. 1, the C-plane length was 0.1 mm or less, and the variation in insertion loss and return loss during lateral loading was compared.

  The results are shown in FIGS. 7 and 8, the horizontal axis represents the load applied in the direction perpendicular to the optical axis, that is, the horizontal load value, and the vertical axis represents the loss fluctuation when the initial value (without load) is set to “0”. I am struggling.

  7 and 8, the characteristics when the C surface is controlled to 0.1 mm or less compared with the case where the C surface is the same as that of a normal connector ferrule are greatly improved in the lateral load. In particular, in terms of return loss, those with a C-plane of 0.1 mm or less maintain good PC connection between fibers up to a load of 600 gf.

It is sectional drawing which shows one Embodiment of the optical receptacle of this invention. (A)-(c) is sectional drawing which shows other embodiment of the sleeve used for the optical receptacle of this invention. It is sectional drawing which shows the conventional optical module. It is sectional drawing which shows the conventional optical receptacle. It is sectional drawing which shows the other conventional optical module. It is sectional drawing which shows the conventional optical receptacle. It is a graph which shows the relationship between the load and connection loss in an optical module. It is a graph which shows the relationship between the load and connection loss in an optical module.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Fiber stub 2: Optical fiber ferrule 3: Optical fiber 4: Sleeve 4a: Thick part 5: Holder 6: Sleeve case 7: Optical receptacle 8: Tip surface of fiber stub 9: Tip surface of fiber stub 10: Plug ferrule 14: optical receptacle 15: plug ferrule 16: fiber stub 17: ferrule 18: optical fiber 19: sleeve 20: holder 21: sleeve case 22: optical element 23: lens 24: case 25: grip ring 26: optical receptacle 27: stub C side

Claims (5)

  A fiber stub with an optical fiber inserted and fixed in the through hole of the ferrule;
  A holder that fixes the rear end of the fiber stub;
  A sleeve inserted in a portion excluding the rear end of the fiber stub, and
  The optical receptacle according to claim 1, wherein the sleeve has a thick portion at one end where the fiber stub is inserted.   2. The optical receptacle according to claim 1, wherein the length of the thick portion of the sleeve is shorter than the insertion length of the fiber stub.   3. The optical receptacle according to claim 1, wherein the thickness of the thick part is 1.5 to 2.5 times that of the other part.   The optical receptacle according to claim 1, wherein the thick portion has an inner diameter equal to that of the other portion and an outer diameter larger than that of the other portion.   An optical receptacle according to any one of claims 1 to 4,
  An optical module comprising an optical element and a lens, and a case welded to the holder.

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