JP2005134550A - Fiber stub, optical receptacle using the fiber stub, method for manufacturing the optical receptacle, and optical module using the optical receptacle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an optical module of high reliability and high performance by forming a ferrule end surface of a shape suitable for an optical receptacle used for the optical module. <P>SOLUTION: The fiber stub inserted and fixed with an optical fiber into a through-hole of the ferrule is provided with a shape having a stepped portion in which the external diameter at the front end surface of the fiber stub is made smaller than the external diameter of the ferrule, by which the foreign matter sticking to the end surface of the fiber stub can be dropped into the stepped portion by cleaning and therefore the fiber stub capable of cleanly maintaining the end surface of the fiber stub and enhancing the characteristic stabilization and coupling efficiency of the optical module and the optical receptacle using the same are realized. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fiber stub, an optical receptacle using the fiber stub, a manufacturing method thereof, and an optical module using the fiber stub.

  As means for transmitting an optical signal, there are an optical fiber connection by an optical connector, a method of converting an optical signal into an electric signal by an optical module, and the like.

When using an optical connector, it is known that the ferrule end face should have an inclined spherical shape with an inclination of 7 degrees or more in order to reduce harmful reflected return light loss. In order to suppress the axial misalignment between the optical fiber and the optical fiber, a ferrule 17 having a straight cylinder top end portion 18 and a connecting portion 19 having a chamfer with an acute angle finish as shown in FIG. 4 has been devised. (See Patent Documents 1 and 2)
Conventionally, in order to convert an optical signal into an electrical signal, an optical element such as a semiconductor laser or a photodiode is accommodated in the case, and this case is provided to face the end face of the optical fiber, and the optical signal is transmitted to the optical fiber. An optical device is disclosed that enters or exits an end face and introduces or derives an optical signal through an optical fiber.

  Here, a semiconductor laser element is housed in a case and an optical signal is derived from a light emitting module, and a photodiode is housed in the case and an optical signal is introduced into a light receiving module. It is called a module.

  The receptacle-type optical module to which an optical connector is connected among the optical modules includes an optical element 21 at one end of the optical receptacle 26 as shown in FIG. 5, and an optical connector is detachably connected to the other end. Is.

  The optical receptacle 26 includes a ferrule 21 made of zirconia, and a rear end portion of a fiber stub 20 obtained by inserting and fixing the optical fiber 22 into the inner diameter of the ferrule 21. The sleeve case 25 is inserted into the inner diameter of the sleeve 23, and the sleeve case 25 is fixed to the holder 24 by press fitting, bonding, welding, or the like.

  Further, when the optical module 33 is configured using the optical receptacle 26 described above, a case 29 including an optical element 27 and a lens 28 is joined to the rear end surface side including the fiber stub 20 of the optical receptacle 26 by welding, An optical connector plug ferrule 30 is inserted into the sleeve 23 from the other end face side of the optical receptacle 26, and the end face 20a of the fiber stub 20 and the end face 30a of the plug ferrule 30 are brought into contact with each other. Can be connected to exchange optical signals.

  The outer diameter of the ferrule 21 and the optical connector plug ferrule 30 is about 1 to 3 mm, the outer diameter tolerance is ± 1 μm or less, the outer diameter of the optical fibers 22 and 31 provided on the inner diameter is about 125 μm, and the outer diameter tolerance is There is a core with a diameter of about 10 μm at which the optical signal propagates in the center at about ± 1 μm, and the cores of the optical fibers 22 and 31 are connected to each other with low loss. The sleeve 23 holds the fiber stub 20 and the optical connector plug ferrule 30 stably and with high accuracy.

  Further, the end surface 20a of the fiber stub 20 and the end surface 30a of the optical connector plug ferrule 30 are 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. The rear end inclined portion 20b on the side is inclined by about 4 to 10 ° in order to prevent the light emitted from the optical element 27 such as an LD from being reflected by the distal end portion of the optical fiber 22 and returning to the optical element 27. The surface is mirror-polished.

  An optical isolator 32 is attached to the rear end inclined portion 20b of the fiber stub 20 in order to prevent reflected return light to the laser light source.

In recent years, in order to stabilize the characteristics of optical modules and increase the coupling efficiency, it has been demanded to strictly manage the flaw stub end surface flaws and the adhesion state of foreign matters.
JP-A-10-68840 JP-A-11-316320

  However, a ferrule 17 having a connecting portion 19 having a chamfer with an acute angle finish and a straight cylindrical top end portion 18 used in the conventional optical connector shown in FIG. 4 is mainly a ferrule for reducing harmful return light loss. Since it is used in the case of an optical connector having an inclined spherical shape whose end face is inclined by 7 degrees or more, it has a shape suitable for an optical connector, and is not a shape suitable for an optical receptacle used in an optical module. It was.

  Further, in the case of the conventional optical module as shown in FIG. 5, since the vicinity of the end face 20a of the fiber stub 20 has a sealed structure, it is very difficult to remove foreign matters attached to the end face 20a of the fiber stub 20. It is difficult, and even if cleaning is performed, it is difficult to increase the stability of the optical module characteristics and increase the coupling efficiency because foreign substances can only be moved from the vicinity of the optical fiber 22 to the vicinity of the outer periphery of the ferrule 21. was there.

  Further, when the optical receptacle 26 is manufactured, the end surface 20a of the fiber stub 20 is often pushed by using a jig or the like to fix the fiber stub 20 to the holder 24. At this time, the end surface 20a of the fiber stub 20 is cured. There is a problem that the scratches that come in contact with the tool or the minute foreign matter attached to the jig falls on the end surface 20a of the fiber stub 20 to deteriorate the characteristics of the optical module.

  Furthermore, in the ferrule 17 having the straight cylindrical upper end portion 18 and the connecting portion 19 having chamfering with an acute angle finish used for the conventional optical connector, the end surface 20a of the fiber stub 20 is pushed to the holder 24 using a jig or the like. Even if the fiber stub 20 is fixed, the diameter of the end face 20a is small, so the area to be pressed becomes small and cannot be fixed stably, and the chamfered part with an acute angle finish prevents the stepped part from being pushed stably. It was impossible, and it was impossible to adopt it for an optical receptacle.

  In view of the above, the present invention provides a fiber stub in which an optical fiber is inserted and fixed in a through-hole of a ferrule, and has a stepped portion in which the outer diameter of the distal end surface of the fiber stub is smaller than the outer diameter of the ferrule. It is a feature.

  Furthermore, the bottom surface of the stepped portion of the fiber stub is formed in a horizontal plane perpendicular to the axis.

  Further, when the outer diameter of the fiber stub is R and the outer diameter of the small diameter portion of the stepped portion is r, 0.3 ≦ r / R ≦ 0.9 is satisfied.

Furthermore, when the outer diameter of the small diameter portion is r and the length of the stepped portion is H,
0.1 ≦ H / r ≦ 0.6 is satisfied.

  Further, the fiber stub is fixed to a holder.

  The optical receptacle manufacturing method is characterized in that a stepped portion of the fiber stub is pushed and fixed to the holder.

  The optical receptacle is attached to a case having an optical element.

  According to the configuration of the present invention, in the fiber stub in which an optical fiber is inserted and fixed in the through-hole of the ferrule, the tip surface of the fiber stub has a stepped shape having a diameter smaller than the outer diameter of the ferrule. The foreign matter attached to the end face can be dropped onto the stepped portion by cleaning and the end face state can be kept clean, so that the characteristics of the optical module can be stabilized and the coupling efficiency can be increased.

  Or because the fiber stub is an optical receptacle in which the above-mentioned stepped portion of the fiber stub is pushed and the fiber stub is fixed to the holder, the end face of the fiber stub may be damaged by a jig, or fine foreign matter attached to the jig There is no possibility of falling on the end face of the fiber stub, and a highly reliable optical receptacle can be realized.

  Furthermore, since the optical module of the present invention is provided with a case containing an optical element that emits an optical signal in the optical receptacle, a high-reliability, low-cost, and high-performance optical module can be realized. .

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an embodiment of an optical receptacle of the present invention.

  FIG. 2 is a side sectional view showing an optical module using the optical receptacle of the present invention.

  As shown in FIG. 1, an optical receptacle 10 of the present invention includes a fiber stub 1 in which an optical fiber 3 is inserted and fixed in a through hole 2 a formed in the center of a ferrule 2, and a holder 5 for fixing one of the fiber stubs 1. The other end of the fiber stub 1 is held on the sleeve 4 for holding the plug ferrule 11 connected to the front end surface 1a of the fiber stub 1.

  The fiber stub 1 has a stepped portion 7 having a small-diameter portion 8 whose tip surface 1 a has a diameter smaller than the outer diameter R of the ferrule 2.

  By having the stepped portion 7, foreign matter attached to the tip end surface 1a of the fiber stub 1 can be dropped onto the bottom surface 7a of the stepped portion 7 by cleaning, and the state of the tip end surface 1a can be kept clean. I can do it.

  The ferrule 2 constituting the fiber stub 1 is made of a metal such as stainless steel or phosphor bronze, a plastic such as an epoxy or a liquid crystal polymer, or a ceramic such as alumina or zirconia, and is particularly preferably formed of zirconia ceramic. Specifically, it is preferable to use a partially stabilized zirconia ceramic containing ZrO2 as a main component, containing at least one of Y2O3, CaO, MgO, CeO2, Dy2O3 and the like as a stabilizer and mainly composed of tetragonal crystals, Such partially stabilized zirconia ceramics are advantageous in fixing by press-fitting because they have excellent wear resistance and are appropriately elastically deformed.

  As a processing method of the ferrule 2, when the ferrule 2 is formed from, for example, zirconia ceramics, a cylindrical or rectangular parallelepiped shaped body that becomes the ferrule 2 by a predetermined molding method such as injection molding, press molding, extrusion molding or the like is obtained in advance. Then, 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 front end surface 1a of the fiber stub 1 is processed into a curved surface having a curvature radius of about 5 to 30 mm in order to reduce the connection loss with the optical connector, and the end surface of the rear end is emitted from an optical element 12 such as an LD (laser diode). In order to prevent the reflected light from being reflected by the end face of the optical fiber 3 and returning to the optical element 12, the optical signal is mirror-polished to an inclined surface of about 4 to 10 °.

  It is desirable that the bottom surface 7a of the stepped portion 7 of the fiber stub 1 has a horizontal plane perpendicular to the axis, and the connecting portion 9 and the bottom surface 7a have a right angle.

  When manufacturing an optical receptacle, the end face of the fiber stub 1 is often pressed using a jig or the like to fix the fiber stub 1 to the holder 5, so that the bottom surface 7a is a horizontal plane perpendicular to the axis as shown in FIG. This is because this part can be used to push with the jig 16 and the like, and the fixing work becomes easy.

  The fiber stub 1 is preferably formed so as to satisfy 0.3 ≦ r / R ≦ 0.9, where R is the outer diameter and r is the outer diameter of the small diameter portion 8 of the stepped portion 7. When manufacturing the optical receptacle, the tip surface 1a of the fiber stub 1 is pushed using the jig 16 or the like to fix the fiber stub 1 to the holder 5, and the tip surface 1a is scratched or adhered. Considering strict management, it is desirable that the above value is small. However, if the value is smaller than 0.3, the area of the front end face 1a of the fiber stub 1 necessary for connecting the optical connector to the optical receptacle 10 is insufficient. There is a risk of worsening the bond.

  If it is larger than 0.9, the diameter difference becomes very small, and the effect of dropping foreign matter on the fiber stub tip surface 1a into the stepped portion 7 by cleaning becomes small. The operation of pressing the jig 16 or the like and fixing the fiber stub 1 to the holder 5 is also difficult.

  Further, the fiber stub 1 is formed to satisfy 0.1 ≦ H / r ≦ 0.6, where r is the outer diameter of the small diameter portion 8 of the stepped portion 7 and H is the length of the stepped portion. It is desirable. If it is smaller than 0.1, the stepped portion 7 may disappear due to the polishing process of the front end face 1a performed when the fiber stub 1 is manufactured. If it is larger than 0.6, the small-diameter portion 8 becomes long, so that the strength of the fiber stub 1 is lowered, and there is a possibility that the fiber stub 1 may be damaged when the fiber stub 1 is fixed to the holder 5 using the jig 16 or the like.

  Further, since the length gripped by the sleeve 4 is also shortened, when the optical connector plug ferrule 11 is connected to the optical receptacle 10, the fiber stub 1 may move and cause a loss.

  The holder 5 has a cylindrical storage portion 5a that is fitted and stored in the outer periphery of the sleeve case 6 in a state where one end of the fiber stub 1 is inserted and fixed to the sleeve 4 stored in the sleeve case 6. A fiber stub fixing portion 5b having a through hole formed at substantially the center of the portion 5a and to which the other end portion of the fiber stub 1 is fixed.

  Since the holder 5 is often welded to the case 14 that houses the optical element 12 of FIG. 2 as an optical module, a material that can be welded such as stainless steel, copper, iron, nickel, etc. is used. Stainless steel is used in consideration of the properties and weldability.

  The entire sleeve 4 is completely accommodated in the sleeve case 6, and a material such as zirconia, alumina, or copper is used as the material, but a zirconia ceramic material is mainly used in consideration of wear resistance.

  The surface roughness of the inner diameter of the sleeve 4 is preferably Ra 0.2 μm or less in consideration of the insertability, and the outer diameter of the fiber stub 1 and the inner diameter tolerance of the sleeve 4 are preferably ± 1 μm or less in order to obtain a low connection loss. The inner diameter of the sleeve 4 is desirably designed to be 0.98 N or more in order to hold the fiber stub 1 securely.

Furthermore, the sleeve case 6 is for stably connecting to the holder 5 described later, and it is not necessary to consider wear resistance and weldability, so stainless steel, copper, iron, nickel, plastic, zirconia, alumina As in the case of the holder 5, stainless steel is mainly used in order to increase the reliability by matching the thermal expansion coefficient with the holder 5.
When an optical module is configured using the optical receptacle 10 of the present invention shown in FIG. 1, an optical element 12 and a lens 13 are provided on one side of the optical receptacle 10 provided with the fiber stub 1 as shown in FIG. The case 14 is joined by welding or the like.

  Here, an optical isolator 15 is attached to the rear end inclined portion 20b of the fiber stub 1 in order to prevent reflected return light to the laser light source.

  Examples of the present invention will be described.

An optical receptacle 10 shown in FIG. 1 as an example of the present invention and an optical receptacle 26 shown in FIG. 5 as a comparative example were manufactured.
The ferrules 2 and 21 used for the fiber stubs 1 and 20 are made of zirconia ceramics, and a cylindrical ceramic molded body is obtained by extrusion molding, baked and sintered in a firing process, and cut to form a ferrule having the shape shown in FIG. 2 and a ferrule 21 having the shape shown in FIG.

  The optical fibers 3 and 22 are inserted and fixed to the ferrules 2 and 21 obtained in this way, the front end surfaces 1a and 20a are mirror-polished to a curved surface with a curvature radius of about 20 mm, and the rear end portion on the opposite side is a light such as an LD. In order to prevent the light emitted from the elements 12 and 27 from being reflected by the end faces of the optical fibers 3 and 22 and returning to the optical elements 12 and 27, mirror polishing is performed on an inclined surface of 8 ° to form a fiber stub. .

  Then, the fiber stubs 1 and 20 obtained by inserting the tip ends of the fiber stubs 1 and 20 into the sleeves 4 and 23, and in the case of the embodiment of the present invention shown in FIG. The sample of the comparative example is pressed into the holder 5 by pressing the tip end surface 20a of the fiber stub 20 using the jig 16, and the sleeve 23 and the sleeve case 25 are attached, and the optical receptacles 10 and 26 are attached. 20p was produced.

  Then, the tip surfaces 1a and 20a of the fiber stubs 1 and 20 of the optical receptacles 10 and 26 thus prepared were cleaned with an industrial cotton swab soaked in ethanol for 1 minute, and the fiber stubs 1 and 20 were cleaned using a 400 × microscope. The number of foreign matters and the number of scratches on the end faces 1a and 20a were counted.

The results are shown in Table 1.

  As a result, in the comparative example, the amount of foreign matter was 4 to 31, and 7 were scratched, whereas in the present invention, the number of foreign matter was 0 to 2 and there was no scratched, It was confirmed that the end face was in good condition.

  Next, as an example, 10 p of the optical receptacle 10 was manufactured by changing the r / R and H / r in various ways by the same method as described above.

As a comparative example, 3p of the optical receptacle 26 shown in FIG.
Then, in the same manner as described above, the number of foreign matters and scratches on the tip surfaces 1a and 20a of the fiber stubs 1 and 20 are counted, and an optical connector is inserted and connected from the tip side of the optical receptacles 10 and 26 to the power meter. The connection loss was measured.

The results are shown in Table 2.

  As a result, when H / r = 0.5, the NO. In the samples 1 and 2, the number of foreign matters is 0 and there is no flaw, and the end surface is in a good state. However, the area of the front end surface 1a of the fiber stub 1 necessary for connecting the optical connector plug ferrule 11 to the optical receptacle 10 Was insufficient and the loss was relatively poor at 0.4 dB.

  NO / r is greater than 0.9. In the case of 10 samples, the loss is as good as 0.1 dB, but the number of foreign matters is 8 and the state of the end face is relatively poor.

From the above, it is preferable that the range of r / R that can maintain a good end face state while maintaining a good loss is 0.3 ≦ r / R ≦ 0.9.

  Next, when r / R = 0.5, NO. In the samples 11 to 14, a sample in which the stepped portion 7 has partially disappeared due to the polishing process when manufacturing the fiber stub 1, and therefore the number of foreign matters on the tip surface 1 a is 7 to 10. Relatively many.

  NO / H is greater than 0.6. In the case of the samples of 21 to 23, the number of foreign matters is 0 to 2 and there is no scratch, and the end face is in a good state, but the loss is slightly large, 0.3 dB to 0.4 dB.

From the above, it was confirmed that the range of H / r that can maintain a good end face state while maintaining a good loss is 0.1 ≦ H / r ≦ 0.6.

  In addition, sample NO. In 24-26, the quantity of foreign matters was 14-27, there were two scratches, and the loss was also as bad as 0.8 dB-1.0 dB.

It is sectional drawing which shows embodiment of the optical receptacle of this invention. It is sectional drawing which shows the optical module using the optical receptacle of this invention. It is sectional drawing which shows the manufacturing method of the optical receptacle of this invention. It is sectional drawing which shows the ferrule for optical connectors which has the connection part which has the chamfering of the chamfer of the conventional straight cylinder top front-end | tip and acute angle finish. It is sectional drawing which shows the conventional optical module.

Explanation of symbols

1: Fiber stub 1a: Tip surface 2: Ferrule 2a: Through hole 3: Optical fiber 4: Sleeve 5: Holder 5a: Storage portion 5b: Fiber stub fixing portion 6: Sleeve case 7: Stepped portion 7a: Bottom surface 8: Small diameter Part 9: Connection part 10: Optical receptacle 11: Optical connector plug ferrule 12: Optical element 13: Lens 14: Case 15: Optical isolator 16: Jig 17: Ferrule 18: Tip part 19: Connection part 20: Fiber stub 20a: Front end surface 20b: Rear end inclined portion 21: Ferrule 22: Optical fiber 23: Sleeve 24: Holder 25: Sleeve case 26: Optical receptacle 27: Optical element 28: Lens 29: Case 30: Optical connector plug ferrule 30a: End surface 31: Optical fiber 32: optical isolator 33: optical module

Claims (7)

A fiber stub in which an optical fiber is inserted and fixed in a through-hole of the ferrule, the fiber stub having a stepped portion in which an outer diameter of a front end surface of the fiber stub is smaller than an outer diameter of the ferrule. 2. The fiber stub according to claim 1, wherein a bottom surface of the stepped portion of the fiber stub is formed in a horizontal plane perpendicular to the axis. 3. The condition of 0.3 ≦ r / R ≦ 0.9 is satisfied, where R is the outer diameter of the fiber stub and r is the outer diameter of the small diameter portion of the stepped portion. No phi stub. When the outer diameter of the small diameter portion is r and the length of the stepped portion is H,
The fiber stub according to claim 1, wherein 0.1 ≦ H / r ≦ 0.6 is satisfied. An optical receptacle comprising the fiber stub according to claim 1 fixed to a holder. 6. The method of manufacturing an optical receptacle according to claim 5, wherein a stepped portion of the fiber stub is pushed and fixed to the holder. An optical module comprising the optical receptacle according to claim 5 attached to a case having an optical element.

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