JP4776934B2 - Fiber stub with optical element, optical receptacle and optical module - Google Patents

Description

  The present invention relates to a fiber stub equipped with an optical element such as an optical isolator, an optical receptacle, and an optical module.

  An optical element such as an optical isolator is often incorporated in a small-sized semiconductor laser module mounted on an optical transceiver used for optical communication at high density to prevent reflected return light. Conventional fiber stubs with optical isolators and optical receptacles and optical modules using the same are disclosed in, for example, Patent Documents 1 and 2. The internal structure will be described with reference to FIGS. FIG. 8 is a longitudinal sectional view of a main part of a conventional fiber stub with an optical isolator. FIG. 9 is a longitudinal sectional view of an optical module using the fiber stub with an optical isolator shown in FIG.

  The optical module shown in FIG. 9 is a coaxial type semiconductor laser module, and the end of the optical fiber is an optical receptacle type. In FIG. 9, the monitoring PD (photodiode) and the lead wires for wiring to the PD are omitted. The optical module includes an optical unit 100 including a semiconductor laser 12, a heat sink 13, a metal stem 14, a lens 15, and a lens holder 16, an optical isolator 11, and an optical receptacle 17.

  In the optical unit 100, the semiconductor laser 12 is mounted on the heat sink 13 by solder. The heat sink 13 is similarly fixed on the metal stem 14 with solder. A lens holder 16 made of metal is resistance-welded to the metal stem 14. Inside the lens holder 16, the lens 15 is fixed by low melting point glass or the like.

  The optical fiber 1 has a through hole 27 at the center, and is held by a ferrule 2 made of ceramic or glass material with an adhesive. The optical fiber 1 and the ferrule 2 constitute a fiber stub 3. The tip of the fiber stub 3 is press-fitted and fixed in the through hole 28 of the metal holder 5. Further, the front end surface 4 of the fiber stub 3 is obliquely polished at 8 ° in order to suppress return light due to near-end reflection to the light emitting element 12 such as a semiconductor laser.

  An optical isolator element 9 for further preventing return light to the light emitting element 12 is fixed to the front end surface of the fiber stub 3. The optical isolator element 9 includes a polarizer 6, a Faraday rotator 7, and an analyzer 8. The optical isolator element 9 is bonded to each other with an adhesive so that the transmission polarization planes of the polarizer 6 and the analyzer 8 have an angle of 45 °. The optical isolator element 9 is cut so as to be within the outer diameter of the distal end surface 4 of the fiber stub 3, and is bonded and fixed to the distal end surface 4 of the fiber stub 3. At this time, the transmission polarization plane of the polarizer 6 is mounted and fixed so as to be vertical or horizontal with respect to the maximum inclination direction of the front end face 4 (8 ° obliquely polished surface) of the fiber stub 3.

  The magnet 10 has a cylindrical shape and applies a magnetic field to the Faraday rotator 7 in the optical isolator element 9. The magnet 10 is bonded and fixed to the metal holder 5 so that the tip of the fiber stub 3 is inserted inside. An optical isolator 11 is constituted by the optical isolator element 9 and the magnet 10.

  On the other hand, the rear end surface 24 of the fiber stub 3 is subjected to curved surface polishing so as to be fitted to the tip of a plug ferrule of an optical connector (not shown). A hollow cylindrical sleeve 18 made of ceramic or metal is covered on the rear end side of the fiber stub 3, and the sleeve 18 is covered with a shell 19. The shell 19 is made of metal or plastic, and is inserted and fixed to the metal holder 5. The fiber stub 3, the metal holder 5, the sleeve 18, and the shell 19 constitute an optical receptacle 17.

The optical module is assembled as follows. First, the optical unit 100 and the optical receptacle 17 with the optical isolator 11 are prepared. Next, the position of the optical receptacle 17 with respect to the optical unit 100 is adjusted so that the light emitted from the semiconductor laser 12 is condensed by the lens 15 onto the optical fiber 1 via the optical isolator 11. Thereafter, the metal holder 5 of the optical receptacle 17 is fixed to the lens holder 16 by laser welding or the like. A counterbore 21 is formed inside the lens holder 16 in the optical unit 100 so that a space is formed so that the optical isolator 11 does not contact the inner wall of the lens holder 16 when the position of the optical receptacle 17 is adjusted. Is formed.
JP 2000-162475 A JP 2002-158389A

  When the optical element 9 such as an optical isolator element, a Faraday rotator, or a mirror is bonded and fixed to the distal end surface 4 of the fiber stub 3, the optical surface of the optical element 9 must be disposed so as not to overlap the end surface of the optical fiber 1. Don't be. However, in the conventional structure shown in FIGS. 8 and 9, especially when the optical element 9 is downsized, the area of the distal end surface 4 is larger than that of the optical element 9. There is no means for regulating the position of the optical element 9. Therefore, when the optical element 9 is fixed to the front end surface 4 of the fiber stub 3 with an adhesive, the position of the optical element 9 may be displaced. If the position of the optical element 9 is shifted, the optical element 9 may come off from the end face of the optical fiber 1 inserted and fixed in the through hole 27.

  For this reason, the area of the optical element 9 fixed to the front end surface 4 of the fiber stub 3 needs to be relatively large in consideration of the positional deviation during the bonding of the optical element 9. For example, when the beam diameter incident on the optical element 9 is about φ0.3 mm, it is difficult to make the optical element 9 smaller than 0.45 mm length × 0.45 mm width. This leads to an increase in the size of the entire optical module.

  When the optical element is a general optical isolator, a magnet for applying a magnetic field to the optical isolator element is required. Since the conventional optical module has a structure in which the cylindrical magnet 10 is inserted and fixed in the fiber stub 3 and attached to the end face of the metal holder 5, there is a problem that the outer diameter of the magnet 10 is increased. In order to reduce the size of the magnet 10, it is also conceivable that the inner diameter of the magnet 10 is made smaller than the outer diameter of the fiber stub 3 so that the tip of the fiber stub 3 is accommodated in the through hole 28 of the holder 5. However, in such a structure, there existed a subject that the adhesive fixing force of the magnet 10 fell and the position of the magnet 10 and the optical isolator element 9 shifted | deviated.

  Furthermore, the inner peripheral portion of the lens holder 16 has a diameter larger than the outer diameter of the magnet 10 and has a depth that the magnet 10 does not hit even if the optical receptacle 17 is moved back and forth during optical axis adjustment. It is necessary to provide a dedicated counterbore part 21. When the magnet 10 contacts the inside of the counterbore part 21, peeling of the joint part of the magnet 10 will occur. For this reason, the counterbore part 21 needs to be made large enough, and as a result, the size of the lens holder 16 also increases. That is, the optical module is increased in size.

  Further, in the conventional structure, the optical isolator 11 cannot be formed at the tip of the fiber stub 3 unless the fiber stub 3 is assembled in the metal holder 5. For this reason, diversification of products is not easy and the assembly procedure is limited. That is, if a variety of products having different shapes of the metal holder 5 are prepared, it is necessary to change the shape and size of the magnet 10 and the optical isolator element 9 for each product. For this reason, there are many different parts for each product type, and product management becomes extremely complicated. If the specifications of the metal holder 5 are not determined, the sizes of the magnet 10 and the optical isolator element 9 are not determined, and the characteristic inspection performed by attaching the optical isolator 11 to the fiber stub 3 cannot be performed. For this reason, the fiber stub 3 with an optical isolator could not be prepared, and there was a problem that it was difficult to cope with a short delivery time.

Accordingly, an object of the present invention is to provide a fiber stub with an optical element, an optical receptacle, and an optical module that are small in size and low in cost.
Another object is to increase the degree of freedom in the assembly procedure of the optical receptacle with an optical isolator.
It is another object of the present invention to simplify product management and shorten delivery time by unifying optical isolator parts.

In view of the above problems, an optical receptacle with an optical element of the present invention includes a ferrule made of one of a ceramic material and a glass material, an optical fiber inserted and fixed in a through-hole in the central portion of the ferrule, and a tip surface of the ferrule And forming a protrusion including the through hole on the tip surface by stepping the tip surface of the ferrule, and connecting the optical element to the outer diameter of the protrusion. And a fiber stub with an optical element bonded to the end face of the projecting portion, and an opening at both ends The optical connector plug ferrule is held in one opening, and the rear end side of the ferrule of the fiber stub is inserted in the other opening. And sleeves, a holder having a through hole, having a holder comprising inserting fixed to the through hole of the tip end of the ferrule, located partly in the through hole of the holder of the projecting portion As described above, the fiber stub is inserted.

  Furthermore, the optical module of the present invention includes an optical unit having a light emitting element and the optical receptacle, and is configured such that light from the light emitting element can enter the optical element of the optical receptacle.

  According to the present invention, since the optical element is bonded to the tip surface of the protrusion formed at the tip of the fiber stub, the optical element is bonded to the tip of the protrusion due to the surface tension of the adhesive when the optical element is bonded with the adhesive. Protruding from the surface can be prevented. In addition, the optical element is likely to be almost at the center of the tip surface of the protrusion due to the surface tension of the adhesive. For this reason, alignment when the optical element is bonded to the fiber stub is facilitated, and the process yield can be improved or simplified.

  Further, even if the area of the optical element is reduced, the optical element can be bonded without being displaced from the optical fiber. Therefore, the optical element can be remarkably reduced in size as compared with the conventional structure. In the cross section perpendicular to the optical axis of the optical element, it is preferable that the area of the optical element is equal to or less than the area of the front end surface of the protrusion.

  Examples of the optical element include an optical isolator element with a magnet, a magnet-less optical isolator element, a Faraday rotator mirror, an AR coated transparent plate, and the like. The effects of facilitating the alignment of the optical element and the miniaturization can be obtained regardless of the type of the optical element. However, in the case of an optical isolator element with a magnet, a particularly remarkable effect is obtained.

  That is, as a result of miniaturization of the optical isolator element, a magnet for applying a magnetic field to the optical isolator element can also be miniaturized. Therefore, the entire optical isolator is reduced in size. As a result, an optical fiber stub with an optical isolator and an optical receptacle incorporating the optical fiber stub are also downsized. Further, when the optical receptacle is incorporated in an optical module such as a semiconductor laser, the optical isolator is accommodated so that the position of the optical isolator can be adjusted, so that the counterbore portion can be made small or unnecessary, and the entire optical module can be downsized.

  Furthermore, when the optical element is an optical isolator element with a magnet, the present invention makes it possible to fix the magnet to the tip of the fiber stub. That is, an optical isolator (optical isolator element + magnet) can be formed directly at the tip of the fiber stub. For example, if the magnet is formed in a cylindrical body and the protruding portion at the tip of the fiber stub is formed in a columnar shape, the protruding portion of the ferrule can be inserted into the magnet and fixedly held.

  In this case, if the outer diameter of the magnet is the same as or smaller than the outer diameter of the ferrule, when inserting the fiber stub with the magnet into the metal holder of the optical receptacle, the magnet itself is also inserted into the metal holder. Can be. Therefore, the optical receptacle can be reduced in size and cost.

  In addition, since the optical isolator can be attached to the tip of the fiber stub, the shape and dimensions of the magnet and the optical isolator element can be made constant regardless of the shape of the metal holder. Therefore, the parts of the optical isolator can be unified, and product management becomes easy.

  In addition, before attaching the fiber stub to the metal holder, the optical characteristics of the fiber stub with the optical isolator can be inspected. For this reason, it is possible to make a fiber stub with an optical isolator as a common part. Thereby, even when a product with a different metal holder shape is ordered, it can be delivered in a short time.

The optical receptacle manufacturing method according to the present invention includes a step of attaching an optical element to the protruding portion of the fiber stub, forming a fiber stub with an optical element, fixing the tip of the fiber stub with the optical element to a holder, Forming an optical receptacle by fixing an end to a sleeve into which an optical connector can be inserted, and in the step of attaching the optical element, the optical element and the optical fiber are aligned using the surface tension of the adhesive It is characterized by that .

  If an optical element such as an optical isolator is attached to the fiber stub before attaching the fiber stub to the holder, it is possible to inspect the optical characteristics of the fiber stub with the optical element in parallel with the molding process of the holder. Also, when there are various holder specifications, optical receptacles can be delivered in a short period of time by producing fiber stubs with optical elements in advance.

  Moreover, it is preferable to provide the inspection process which inspects the optical characteristic of the fiber stub with an optical element after the process of forming the fiber stub with the optical element and before the process of forming the optical receptacle. For example, if the optical element is an optical isolator, it is preferable to measure insertion loss and isolation.

When measuring the insertion loss, light is incident from the optical isolator side of the fiber stub with the optical isolator, and the maximum output P _{1 of the} light emitted from the rear end of the fiber stub while rotating the fiber stub with the optical isolator around the optical axis. was measured, it is possible to measure the insertion loss on the basis of the maximum output P _1. On the other hand, when measuring isolation, light is incident from the rear end side of the fiber stub with an optical isolator, and the maximum output P _{2 of the} light emitted from the optical isolator while rotating the fiber stub with the optical isolator around the optical axis. was measured, it is possible to measure the isolation on the basis of the maximum output P _2. If the insertion loss and isolation are measured by such a method, a polarization scrambler for making the output light of the light source into a random polarization becomes unnecessary. Also, insertion loss and isolation can be measured simply by reversing the direction of the fiber stub instead of reversing the polarity of the magnet. Therefore, the insertion loss and isolation inspection device and inspection process can be simplified.

  As described above, according to the present invention, a small and low-cost fiber stub with an optical element, an optical receptacle, and an optical module can be provided.

  In particular, when the optical element is an optical isolator, it is possible to increase the degree of freedom in the procedure for assembling the optical receptacle with the optical isolator. In addition, product management can be simplified and delivery time can be shortened by unifying optical isolator parts.

Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol shall be used about the same thing as a prior art.
(Fistub with optical isolator)
FIG. 1 is a longitudinal sectional view showing a fiber stub 3 with an optical isolator according to the present invention. The optical fiber 1 is inserted through the through hole 27 in the central portion of the ferrule 2 made of a ceramic material or glass material such as zirconia or alumina, and is held by an adhesive. The ferrule 2 and the optical fiber 1 constitute a fiber stub 3.

  Further, the tip of the fiber stub 3 is stepped 22 and is provided with a cylindrical protrusion 23 having an outer diameter of φ0.5 mm or less. The protrusion 23 is preferably formed so that the optical axis of the optical fiber 1 is located at the center thereof. Further, the outer diameter of the protruding portion 23 needs to be larger than at least the spot diameter of a beam incident from a semiconductor laser described later. The spot diameter of the beam is generally Φ0.2 to 0.25 mm. The height of the protrusion 23 needs to be high enough to maintain the shape of the liquid adhesive applied to the tip of the protrusion by surface tension. Therefore, it is preferable that the height at the center of the step surface of the protrusion is at least 80 μm or more. Moreover, when fitting the protrusion part 23 with a cyclic | annular magnet, it is preferable to make it the height of 150 micrometers or more so that the fixed strength of a magnet may become high. On the other hand, if the protrusion 23 is too high, there is a problem that the protrusion 23 is likely to be chipped. Therefore, the height of the protrusion 23 is preferably 350 μm or less. The cross-sectional shape of the protrusion 23 is not limited to a circle. For example, the protrusion 23 may be a substantially cylindrical shape with an elliptical cross section, or may be a prismatic shape with a rectangular cross section. The protrusion 23 having a rectangular cross section can be produced by dicing the tip of the fiber stub 3.

  Further, the tip surface 29 of the protrusion 23 is polished so as to be inclined by 8 ° with respect to a surface perpendicular to the optical axis in order to suppress return light due to near-end reflection to the optical element 12 such as a semiconductor laser. Yes. An optical isolator element 9 to be described later is joined to the front end surface 29 (hereinafter referred to as “step surface 29”) of the protruding portion 23. The step surface 29 may be a plane perpendicular to the optical axis without the step surface 29 being polished obliquely.

  When used for an optical receptacle, the rear end surface 24 of the fiber stub 3 is subjected to curved surface polishing so as to come into contact with the tip of a plug ferrule of an optical connector (not shown).

  In the present invention, it is preferable that the projected area of the optical isolator element 9 on the plane perpendicular to the optical axis is equal to or smaller than the projected area of the stepped surface 29 on the plane perpendicular to the optical axis. That is, it is preferable that the size of the optical isolator element 9 be set in a region surrounded by the outer periphery of the step surface 29. This is because the optical isolator element 9 joined to the stepped surface 29 can be accommodated within the outer diameter without protruding laterally from the protrusion 23. Another reason is to prevent the optical isolator element from colliding with the inner peripheral surface of the magnet 10.

  As shown in FIG. 3, in the optical isolator element 9, the light incident surface and the light exit surface are inclined at a predetermined angle with respect to the surface 26 perpendicular to the optical axis. Accordingly, the area of the surface 26 perpendicular to the optical axis is smaller than the contact area with the step surface 29 of the ferrule. In the present embodiment, for example, the outer diameter of the vertical section 26 is equal to or less than the outer diameter of the protruding portion 23 of the fiber stub 3 and is formed, for example, 0.35 mm in length × 0.35 mm or less in width. Yes.

  The optical isolator element 9 includes a polarizer 6, a Faraday rotator 7, and an analyzer 8. After rotating and aligning in advance so that the angle of the transmission polarization plane of the polarizer 6 and the analyzer 8 is 45 °, the polarizer 6 and the analyzer 8 are fixed to each other by an adhesive. Further, the incident / exit surface is formed so as to be inclined at 8 ° which is the same as the polishing angle of the fiber stub 3. The optical isolator element 9 is cut into a size that can be accommodated within the outer diameter of the protrusion 23 of the fiber stub 3. Then, the cut optical isolator element 9 is bonded and fixed to the step surface 29 at the tip of the fiber stub 3. At this time, the transmission polarization plane of the polarizer 6 is set to be vertical or horizontal with respect to the maximum inclination direction of the step surface 29 of the fiber stub 3 that is obliquely polished at 8 °.

  FIGS. 4A to 4C are schematic views showing a method for bonding and fixing the optical isolator element 9 to the protruding portion 23 at the tip of the fiber stub 3. First, as shown in FIG. 4A, the fiber stub 3 is set so that the stepped surface 29 formed at the tip thereof is horizontal, and an appropriate amount of adhesive 32 is applied on the stepped surface 29. The adhesive 32 is preferably a liquid having a large surface tension before curing.

  Next, the optical isolator element 9 is placed on the liquid adhesive 32 applied to the protruding portion 23 of the fiber stub 3. At this time, due to the surface tension of the adhesive 32, the optical isolator element 9 does not protrude outside the protrusion 23. Therefore, if the outer diameter of the optical isolator element 9 is appropriately set, the center of the optical isolator element 9 can be made to substantially coincide with the center of the through hole 27 by utilizing the surface tension of the adhesive 32.

  Next, as shown in FIG. 4C, the optical isolator element 9 is pressed against the step surface 29 of the fiber stub. Thereafter, the adhesive 32 is cured by heating in an oven. By curing the adhesive 32 after pressing the optical isolator element 9 against the stepped surface 29, it is possible to prevent the optical isolator element 9 from slipping during the curing and causing a positional shift.

  According to this method, even if the optical isolator element 9 is downsized, it does not protrude from the stepped surface 29 of the protruding portion 23 due to the surface tension of the adhesive, and the through hole 27 into which the optical fiber 1 is inserted and fixed is substantially at the center. Can be installed as In order to effectively use the surface tension, in the state where the optical isolator element 9 is placed on the stepped surface 29, the outer diameter of the contact surface (exit-side end face) 9a with the protruding portion 23 of the optical isolator element 9 is It is preferable to make it smaller than the outer diameter of the stepped surface 29. For example, in FIG. 5, the contact surface 9a of the optical isolator element is smaller than the maximum dimension indicated by the broken line 34 (a dimension in which the vertex of the rectangular contact surface 9a coincides with the outer periphery of the substantially elliptical step surface 29). preferable. On the other hand, the optical isolator element 9 must be larger than the incident beam diameter of the semiconductor laser. The incident beam diameter of the semiconductor laser is generally 0.2 to 0.25 mmφ. Therefore, it is preferable that the contact surface 9a of the optical isolator element 9 has such a size that a circle of at least φ0.2 mm is included. Further, if the contact surface 9 a of the optical isolator element is too small compared to the stepped surface 29, the optical fiber 1 is easily detached from the optical isolator element 9. For example, in FIG. 5, the contact surface 9 a of the optical isolator element has a minimum dimension indicated by a one-dot chain line 36 (the outer periphery of the optical fiber 1 when the two vertices of the rectangular contact surface 9 a are in contact with the outer periphery of the step surface 29. Is preferably larger than the dimension that contacts the outer periphery of the contact surface 9a.

  In FIG. 1, a magnet 10 for applying a magnetic field to the Faraday rotator 7 has a cylindrical shape, and its outer diameter is the same as or smaller than φ1.25 mm, which is the minimum outer diameter of a commonly used fiber stub 3. It is preferable to set the following. If the outer diameter of the magnet 10 is made smaller than the outer diameter of the fiber stub 3 in this way, the magnet can be prevented from protruding beyond the ferrule in the diameter direction of the ferrule, and the entire fiber stub with the optical isolator can be made substantially cylindrical. . Therefore, when designing an optical module to be described later, a part of the magnet 10 can be inserted and fixed in the through hole 28 of the metal holder 5 together with the fiber stub 3 as shown in FIG. As a result, the optical receptacle and the optical module can be miniaturized.

  The inner diameter of the magnet 10 is set to be equal to or larger than the outer diameter of the protruding portion 23 of the fiber stub 3. Thereby, the magnet 10 can also be press-fitted into the stepped portion 22 of the fiber stub 3. The magnet 10 is fixed to the fiber stub by an adhesive. However, if the magnet 10 is press-fitted into the stepped portion 22, the fixing strength of the magnet can be further improved. Thus, by fixing the magnet 10 to the protruding portion 23 of the fiber stub 3, the fiber stub 25 with an optical isolator is formed.

(Optical module, optical receptacle)
FIG. 2 shows a longitudinal sectional view of a coaxial type semiconductor laser module according to an embodiment of the present invention. In FIG. 2, the monitoring PD (photodiode) and lead wires for wiring to the PD (photodiode) are omitted. The optical module shown in FIG. 2 includes an optical receptacle 30 with an optical isolator and an optical unit 100 attached to the front end surface thereof.

  The optical unit 100 includes a semiconductor laser 12, a heat sink 13, a metal stem 14, a lens 15, and a lens holder 16. The semiconductor laser 12 is mounted on the heat sink 13 with solder. The heat sink 13 is similarly mounted and fixed by solder on a metal stem 14 with a support portion protruding vertically on a cylindrical plane. The lens holder 16 is formed in a cylindrical shape so as to cover the periphery of the cylindrical surface of the metal stem 14 and is made of a material capable of resistance welding. The lens holder 16 is fixed so as to accommodate the semiconductor laser 12 and the heat sink 13. Further, the lens 15 is fixed to the lens holder 16 on the inner periphery 20 on the downstream side of the laser optical path of the semiconductor laser 12 with low melting point glass or the like.

  The optical receptacle 30 with an optical isolator includes a fiber stub 25 with an optical isolator, a metal holder 5, a sleeve 18, and a shell 19. The rear end surface of the fiber stub 25 with an optical isolator is subjected to curved surface polishing so as to be fitted to the tip of a plug ferrule of an optical connector (not shown). A hollow cylindrical sleeve 18 made of ceramic or metal is covered on the rear end side of the fiber stub 25 with an optical isolator, and the sleeve 18 is covered with a shell 19. The shell 19 is made of metal or plastic, and is inserted and fixed to the metal holder 5.

  The metal holder 5 is generally formed in a bottomed cup shape, and has a through hole 28 penetrating in the thickness direction from the center of the bottom surface. The distal end side of the fiber stub 25 with an optical isolator is press-fitted and held in the through hole 28. As the material of the metal holder 5, a stainless material having excellent corrosion resistance and weldability, such as SUS304, is used, but a weldable material such as iron or nickel may be used.

  As the sleeve 18, a split sleeve in which a cylinder made of phosphor bronze, a ceramic material or the like is slit in the entire length can be used. An optical connector plug ferrule (not shown) is held in the opening on one side of the sleeve 18, and the rear end side of the ferrule of the fiber stub 25 with an optical isolator is inserted from the opening on the other side of the sleeve 18.

  The shell 19 is formed in a cylindrical shape, and the entire sleeve 18 is accommodated in the shell 19 in a state of being separated from the side wall of the metal holder 5. The shell 19 can be press-fitted and held in the metal holder 5. Metal or plastic is used as the material of the shell 19. Then, a shell 19 covers the sleeve 18 into which the fiber stub 3 is press-fitted, and the shell 19 is inserted and fixed in the metal holder 5 to constitute the optical receptacle 17.

  In the present embodiment, the magnet 10 of the optical isolator 11 is partially inserted and fixed in the through hole 28 of the metal holder. As a result, the joint between the magnet 10 and the fiber stub 3 is protected, and the optical receptacle can be miniaturized. That is, when the optical receptacle 17 is aligned with the optical axis, the magnet 10 does not peel off even if the magnet 10 comes into light contact with the inner peripheral surface 20 of the lens holder 16 and the reliability is improved. In addition, a small and low-cost optical module can be provided.

  Further, according to the present embodiment, the dimensions of the magnet 10 and the optical isolator element 9 of the optical isolator 11 can be determined regardless of the dimensions of the metal holder 5. Conventionally, it is necessary to change the design of the optical isolator 11 for each specification of the metal holder, but in this embodiment, the components of the optical isolator can be unified regardless of the specification of the metal holder. Therefore, product management of optical receptacles and optical modules is facilitated.

(Optical module manufacturing procedure)
Next, the manufacturing procedure of the optical module will be described.
First, an optical receptacle 30 with an optical isolator is prepared. In order to manufacture the optical receptacle 30 with an optical isolator, the optical isolator 11 may be attached after the optical receptacle 17 is formed as in the conventional example shown in FIG. However, according to the present invention, the optical isolator 11 can be attached to the fiber stub 3 before the fiber stub 3 is attached to the metal holder 5. Accordingly, it is possible to inspect the isolation characteristics and the like of the fiber stub with an optical isolator in parallel with the molding process of the metal holder. In addition, a fiber stub with an optical isolator can be produced in advance. Accordingly, it is possible to cope with a short delivery time of the optical receptacle.

  Next, the optical receptacle 30 with an isolator and the optical unit 100 are assembled. In the optical module, light emitted from the semiconductor laser 12 is collected by the lens 15 and introduced into the optical fiber 1 via the optical isolator 11. Therefore, it is necessary to adjust the position of the optical receptacle 17 so that the light collected by the lens 15 is correctly incident on the optical fiber 1. After the tip of the optical receptacle 30 with an isolator is inserted into the lens holder 16 of the optical unit 100, the position of the optical receptacle 30 is adjusted by moving the position back and forth. At this time, in the optical receptacle 30 of the present embodiment, since the outer diameter of the optical isolator 11 is sufficiently smaller than the inner periphery 20 of the lens holder 16, it is necessary to provide a counterbore portion 21 as shown in the conventional example of FIG. Absent. Moreover, even if the optical isolator 11 contacts the inner wall of the lens holder 16, the magnet 10 in the optical isolator 11 is firmly fixed to the fiber stub 3, so that defects such as separation of the magnet 10 are unlikely to occur. . When the position adjustment of the optical receptacle 17 is completed, the metal holder 5 of the optical receptacle 17 is fixed to the lens holder 16 by laser welding or the like.

(Optical property inspection method)
An inspection method of optical characteristics (insertion loss and isolation) in the present embodiment will be described. As described above, in this embodiment, the inspection can be performed after the optical receptacle with the optical isolator is assembled, or the fiber stub with the optical isolator can be assembled first and the inspection can be performed. If a fiber stub with an optical isolator is first assembled and inspected, it is possible to deliver optical receptacles and optical modules in a short time.

First, a case where optical measurement is performed after an optical receptacle with an optical isolator is assembled will be described. In order to measure insertion loss and isolation measurement, the light source 40 is first prepared. As shown in FIG. 6A, the light source 40 includes a light generating device 42 such as a laser, a polarization scrambler 44, and an optical connector 46, which are connected by optical fibers. The reason why the polarization scrambler 44 is used here is to make the light emitted from the light source 40 into a randomly polarized light. Then, the output P _{0 of the} light source 40 is measured by the detector 48.

When measuring insertion loss and isolation, the optical connector 46 of the light source 40 is inserted into the optical receptacle 30 with an optical isolator, and light enters from the output side of the optical receptacle 30. Then, the output of the light emitted from the optical isolator 9 is measured by the detector 48. At this time, when the maximum output when the magnet 10 is measured with the reverse polarity is P ₁ , the insertion loss is (P ₀ −P ₁ ). On the other hand, when the maximum output when the magnet 10 is measured with positive polarity is P ₂ , the isolation is (P ₀ −P ₂ ). Thus, when measuring the optical characteristics of the optical receptacle 30 with an optical isolator, a polarization scrambler is required, and the polarity of the magnet 10 needs to be reversed for each measurement, so the measurement is complicated.

  Next, a method for measuring the insertion loss and isolation of the fiber stub 25 with an optical isolator in the present embodiment will be described. According to this Embodiment, it can measure with the following simple methods.

First, as shown in FIG. 7A, a measurement light source 50 in which a lens-equipped laser unit (LD-CAN) 52 is combined with a driving driver 51 is prepared. As the lens-equipped laser unit 52, the optical unit 100 itself of an optical module may be used. In that case, there exists an advantage which can test | inspect the characteristic of the optical isolator in a final optical module more correctly. The output P ₀ of the measurement light source 50 is measured by the detector 48 in advance.

Next, the insertion loss is measured. As shown in FIG. 7B, a fiber stub 25 with an optical isolator is installed on an XYZθ stage that can rotate around the optical axis of the measurement system, and light from the light source 50 is incident from the optical isolator 11 side. The output of light emitted from the rear end surface (PC end surface) of the fiber stub 25 is measured by the detector 48. If the output is measured while the fiber stub 25 is rotated and the obtained maximum optical output value is P ₁ , the insertion loss is (P ₀ −P ₁ ).

Next, the isolation may be measured by inverting the direction of the fiber stub 25 with an optical isolator in the same measurement system as the insertion loss. That is, as shown in FIG. 7C, light is incident from the rear end face (PC end face) of the fiber stub, and the output of the light emitted from the optical isolator 11 side is measured by the detector 48. If the output is measured while the fiber stub 25 is rotated and the obtained maximum optical output value is P ₂ , the isolation is (P ₀ −P ₂ ).

  As described above, according to the inspection method of the present embodiment, since the output is measured while rotating the fiber stub 25 with the optical isolator, the polarization scrambler for making the output light of the light source into the random polarization becomes unnecessary. Further, the insertion loss and the isolation can be measured only by reversing the direction of the fiber stub 25 itself instead of reversing the polarity of the magnet. Therefore, the insertion loss and isolation inspection device and inspection process can be simplified.

  Such an inspection method is made possible by utilizing the fact that the outer diameter standard of the fiber stub 25 is almost determined and the outer diameter accuracy is high. That is, in the case of the optical receptacle, the shape of the metal holder varies depending on the application and the user, and the metal holder is often provided with a flange. For this reason, it is necessary to prepare many types of rotating stages for rotating the optical receptacle, and the preparation of the measuring apparatus becomes extremely complicated. Moreover, the accuracy of the outer diameter of the metal holder is as bad as ± 50 μm or more, and the eccentricity due to rotation is large. For this reason, it is difficult to stably measure the light output while rotating the optical receptacle. On the other hand, since the outer diameter standard of the fiber stub 25 is almost determined, it is sufficient to prepare several types of rotary stages. Further, since the outer diameter accuracy of the fiber stub made of zirconia or the like is as high as ± 1 to 2 μm, there is almost no eccentricity during rotation. Therefore, it is possible to measure the light output stably even while rotating the optical receptacle.

  In the embodiment shown in FIGS. 1 to 7, the case where the optical element fixed to the tip of the fiber stub is an optical isolator with a magnet has been described, but the present invention is not limited to this. Any optical element that is fixed to the tip of the fiber stub and needs to be aligned with the optical fiber in the fiber stub may be used.

For example, the optical element may be an optical isolator that does not require a magnet. Since the latching garnet itself has a magnetic force, a magnetless optical isolator can be configured by using the latching garnet for the Faraday rotator. In the case of a magnet-less optical isolator, there is no need to fix the magnet around the optical isolator element after the optical isolator element is bonded to the protrusion provided at the tip of the fiber stub. Therefore, the outer diameter of the tip of the fiber stub 3 is not different from that of the main body. Further, since the optical isolator is bonded and fixed to the protrusion at the tip of the fiber stub, it is located on the inner side of the outer periphery of the fiber stub. Therefore, even when a fiber stub is inserted into the lens holder of the semiconductor laser module for alignment, it is not necessary to provide a counterbore hole for preventing contact inside the lens holder. Therefore, the semiconductor laser module can be reduced in size.

  The optical element fixed to the tip of the fiber stub may be a Faraday Rotator Mirror composed of a Faraday rotator and a magnet provided with a total reflection mirror coating. Also in this case, the same effect as in the case of the optical isolator with magnet can be obtained. The fiber stub with Faraday rotator and mirror is suitable for optical sensor applications. Furthermore, the optical element may be simply glass with AR coating. By providing this glass at the tip of the fiber stub, the return light of the laser light can be suppressed.

  Hereinafter, as an example of the present invention, an optical module including a fiber stub with an optical isolator and an optical receptacle shown in FIGS. 1 and 2 was produced. The optical module was a coaxial optical receptacle type semiconductor laser module.

  In FIG. 1, an optical fiber 1 is bonded and fixed to a through hole 27 in the center of a ferrule 2 made of zirconia and having an outer diameter of φ1.25 mm, thereby forming a fiber stub 3. A step 22 was applied to the tip end side of the fiber stub 3, and a protrusion 23 having an outer diameter of φ0.5 mm was provided. And the level | step difference surface 29 of this protrusion part 23 was diagonally polished by 8 degrees. Further, the rear end surface of the fiber stub 3 was subjected to a curved surface polishing process for fitting with a plug ferrule tip of an optical connector (not shown).

  On the other hand, as shown in FIG. 3, the optical isolator element 9 has an incident / exit surface of 8 ° which is the same as the polishing angle of the fiber stub 3. Further, the vertical section 26 with respect to the optical axis was cut into a length of 0.3 mm and a width of 0.3 mm so as to be accommodated within the outer diameter of the protruding portion 23 of the fiber stub 3. Note that the polarizer 6, the Faraday rotator 7 and the analyzer 8 of the optical isolator element 9 are rotated and aligned in advance so that the angle of the transmission polarization plane of the polarizer 6 and the analyzer 8 is 45 °, and then adhesive is used. Bonded and fixed. Further, the transmission polarization plane of the polarizer 6 was installed so as to be perpendicular to the 8 ° oblique polishing surface of the step surface 29 of the fiber stub 3.

  The cylindrical magnet 10 for applying a magnetic field to the Faraday rotator 7 has an outer diameter of φ1.2 mm, an inner diameter of φ0.6 mm, and a length of 1 mm. Further, the fiber stub 3 was inserted and fixed to the step 22 of the fiber stub 3 with an adhesive. Thus, a fiber stub 25 with an optical isolator was formed.

  In FIG. 2, the semiconductor laser 12 is mounted and fixed on the heat sink 13 by soldering. The heat sink 13 was similarly mounted and fixed on the metal stem 14 with solder. The lens 15 was fixed to a lens holder 16 made of stainless steel with low melting point glass, and the lens holder 16 was resistance welded to the metal stem 14.

  The tip end side of the fiber stub 25 with an optical isolator was press-fitted and fixed at a position where the step 22 of the fiber stub 3 did not protrude from the through hole 28 of the metal holder 5. Further, the rear end side of the fiber stub 3 was inserted into a sleeve 18 made of zirconia, and the sleeve 18 was inserted into a shell 19 made of stainless steel. Then, the shell 19 was press-fitted and fixed to the metal holder 5 to form the optical receptacle 17. Then, after the position of the optical receptacle 17 was adjusted so that the light collected by the lens 15 was correctly incident on the optical fiber 1, the metal holder 5 of the optical receptacle 17 was fixed to the lens holder 16 by laser welding.

Table 1 shows a comparison between the conventional semiconductor laser module and the semiconductor laser module according to this embodiment. The vertical cross-sectional area of the light incident side end face with respect to the optical axis of the fiber stub and the polishing time, the vertical cross-sectional area with respect to the optical axis of the optical isolator element, the outer diameter of the magnet, and the presence / absence of the counterbore portion for the optical isolator of the inner diameter of the lens holder are compared.

In the optical module of this embodiment, the protrusion 23 is provided on the light incident side of the fiber stub 3 and the stepped surface 29 is obliquely polished, so that the area of the polished surface is 20% or less compared to the conventional example. It has become. For this reason, the working time during the oblique polishing can be reduced by about 50% even including the additional step of the step processing 22. Further, the area of the vertical section 26 with respect to the optical axis of the optical isolator element 9 bonded and fixed to the stepped surface 29 of the protrusion 23 is set to about 0.12 mm ² in this embodiment compared to about 0.2 mm ² in the conventional example. As a result, the number of cuts was increased and the cost was reduced.

  Furthermore, the outer diameter of the cylindrical magnet 10 is reduced to 40 mm compared to the conventional example, φ1.2 mm, and the optical isolator 11 is reduced in size by being inserted and fixed in the step 22 of the fiber stub 3. Further, since the optical isolator 11 can be formed without waiting for the processing of the metal holder 5 that holds the fiber stub 3, it is possible to unify the size of the optical isolator 11, simplify the product management, and cope with a short delivery time.

  Further, since the outer diameter of the optical isolator 11 is smaller than the outer diameter of the fiber stub 3, it is not necessary to provide a dedicated counterbore portion 21 for housing the optical isolator 11 on the inner periphery 20 of the lens holder 16 of the optical module. The holder 16 can also be reduced in price, and it has become possible to provide a small and low-cost optical module in which the magnet does not peel off to the extent that it comes in light contact with the inner periphery.

FIG. 1 is a longitudinal sectional view of a fiber stub with an optical isolator according to the present invention. FIG. 2 is a longitudinal sectional view of the semiconductor laser module of the present invention. FIG. 3 is a perspective view of the optical isolator element 9 of the present invention. FIGS. 4A to 4C are schematic views showing a method of bonding an optical isolator to the protruding portion of the fiber stub. FIG. 5 is a schematic plan view showing the relationship between the end face (step surface) of the protrusion and the size of the optical isolator. 6 (A) and 6 (B) are schematic diagrams illustrating a method for measuring the optical characteristics of an optical receptacle with an optical isolator. 7A to 7C are schematic views for explaining a method for measuring optical characteristics of a fiber stub with an optical isolator. FIG. 8 is a longitudinal sectional view of a main part of a conventional fiber stub with an optical isolator. FIG. 9 is a central longitudinal sectional view of a conventional semiconductor laser module.

Explanation of symbols

1 optical fiber, 3 fiber stub, 5 metal holder, 9 optical isolator element, 10 magnet, 11 optical isolator, 12 semiconductor laser, 13 heat sink, 14 no metal throwing away, 16 lens holder, 15 lens, 17 optical receptacle, 18 sleeve, 19 shell, 23 protrusion, 25 fiber stub with optical isolator, 27 through hole, 30 optical receptacle with optical isolator, 100 optical unit

Claims (9)

A ferrule made of one of a ceramic material or a glass material, an optical fiber inserted and fixed in a through-hole in the ferrule central portion , an optical element having a Faraday rotator joined to a tip surface of the ferrule, and the Faraday A magnet that applies a magnetic field to the rotor, and by stepping the tip surface of the ferrule, a protrusion including the through hole is formed on the tip surface, and the optical element is connected to the outer diameter of the protrusion. A fiber stub with an optical element that is smaller than the optical element when the optical element is in contact with the outer periphery of the protrusion, and is bonded to the end face of the protrusion;
A sleeve opened at both ends, holding a plug ferrule for an optical connector in one opening, and inserting the ferrule rear end side of the fiber stub in the other opening;
A holder having a through hole, the holder formed by inserting and fixing the tip side of the ferrule into the through hole,
The optical receptacle with an optical element , wherein the fiber stub is inserted into the holder and the sleeve so that a part of the magnet is positioned in the through hole of the holder . 2. The optical receptacle with an optical element according to claim 1 , wherein the magnet is formed in a cylindrical shape, the protrusion is formed in a columnar shape, and the magnet is fitted into the protrusion. 2. The optical receptacle with an optical element according to claim 1 , wherein the outer diameter of the magnet is equal to or smaller than the outer diameter of the ferrule.   The optical receptacle with an optical element according to claim 1, wherein an end surface of the protruding portion is obliquely processed. An optical module comprising: an optical unit having a light emitting element; and an optical receptacle with an optical element according to claim 1,
An optical module, wherein light from the light emitting element is incident on the optical element. A method of manufacturing an optical receptacle according to claim 1,
Attaching the optical element to the protrusion of the fiber stub and forming a fiber stub with an optical element;
Fixing the tip of the fiber stub with the optical element to a holder and fixing the rear end to a sleeve into which an optical connector can be inserted to form an optical receptacle, and
In the step of attaching the optical element, the optical element and the optical fiber are aligned using the surface tension of the adhesive so that the optical element does not protrude outside the protrusion. Receptacle manufacturing method. 7. The optical receptacle according to claim 6 , further comprising an inspection step of inspecting optical characteristics of the fiber stub with an optical element after the step of forming the fiber stub with the optical element and before the step of forming the optical receptacle. Manufacturing method. In the above SL inspection process, light is incident from the optical element side of the optical element with the fiber stub, the maximum output P ₁ of the light emitted from the fiber stub rear while rotating the fiber stub with the optical element about the optical axis The optical receptacle manufacturing method according to claim 7, wherein the insertion loss is measured based on the maximum output P ₁ . In the above SL inspection process, the light incident from the rear end side of the optical element with the fiber stub, the maximum output P ₂ of the light emitted from the optical element while rotating the fiber stub with the optical element about the optical axis measured, the optical receptacle of the manufacturing method according to claim 7, characterized in that measuring the isolation on the basis of the maximum output P _2.

Images