JP2013011704A - Fiber stub with optical element, optical receptacle using the same, and optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fiber stub on which a small-size optical isolator element is highly accurately mounted, which is easily processed and has high productivity, and provide an optical receptacle using the same and an optical module.SOLUTION: A fiber stub 4 in which an optical fiber 2 is inserted in the axial direction of a ferrule 1 includes an optical element 3 at a rear end face 1b of the ferrule 1. The projection area of the rear end face 1b to a surface perpendicular to the optical axis is smaller than the projection area of the entire ferrule 1. The rear end-side outer peripheral surface 1e of the ferrule 1 is tapered towards the rear end face 1b. The ferrule 1 has a tapered face tapered towards the rear end face 1b and a small-size optical isolator element 3 can be highly accurately mounted thereon. The fiber stub is easily processed and has high productivity.

Description

  The present invention relates to a fiber stub equipped with optical elements such as an optical isolator element, a Faraday rotator, and a mirror, and an optical receptacle and an optical module using the same.

  In optical communication, an optical isolator is used for the purpose of preventing return light to the semiconductor laser element. The optical isolator is fixed in, for example, an optical receptacle. FIG. 5 is a cross-sectional view showing an example of a conventional optical receptacle.

  A conventional optical receptacle 30 includes a fiber stub 31 in which an optical fiber 31 a is inserted into a ferrule 31 b, a holder 32 that holds the rear end side of the fiber stub 31, and a sleeve 33 that is attached to the front end side of the fiber stub 31. The shell 34 that covers the outside of the sleeve 33 and is held by the holder 32 is combined. An optical isolator 35 including an optical isolator element 35a and a magnet 35b is fixed to the rear end surface of the fiber stub 31 (see, for example, Patent Document 1).

  A semiconductor laser element (not shown) is disposed on the rear end side (left side in the figure) of the optical receptacle 30. Return light that enters the semiconductor laser element from the front end side (right side in the drawing) of the optical receptacle 30 is blocked by the optical isolator 35. In this way, the operation of the semiconductor laser element is not affected by the return light.

  By the way, if the fixing position of the optical isolator 35 on the rear end face of the fiber stub 31 deviates from the optical axis position, the insertion loss increases. Therefore, it is necessary to carefully fix the optical isolator element 35a to the fiber stub 31. . Therefore, a method for facilitating the fixing work of the optical isolator has been devised.

  FIG. 6 shows an example of an optical fiber pigtail 40 to which an optical isolator is fixed (see, for example, Patent Document 2).

  In FIG. 6, the optical isolator 45 includes an optical isolator element 45a and a magnet 45b. The outer diameter of the rear end portion (left side portion in the figure) of the ceramic capillary 41b is processed to the same diameter as the diameter of the circumscribed circle of the optical isolator element 45a. On the other hand, the inner diameter of the cylindrical magnet 45b is a dimension that fits exactly with the circumscribed circle of the optical isolator element 45a and the outer diameter of the ceramic capillary 41b, and the optical isolator element 45a can be positioned and fixed by the inner diameter portion of the magnet 45b. It is like that. As a result, the optical isolator element 45a is prevented from being displaced and fixed from the optical axis.

JP 2004-93695 A JP 2002-82308 A

In recent years, optical receptacles 20 and 45 have been made smaller, thereby reducing optical receptacle 20.
There is a demand to make the optical fiber pigtail 40 and the like cheaper. In the optical fiber pigtail 40, when the optical isolator element 45a is made smaller, the amount of grinding of the outer shape of the ceramic capillary 41b increases accordingly. An increase in the amount of grinding causes an increase in processing cost due to an increase in processing time. Furthermore, the processing accuracy of the peripheral surface of the protruding portion on which the optical isolator element 45a of the ceramic capillary 41b is mounted, the root portion of the protruding portion, and the like is required, and there is a problem that productivity does not increase.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fiber stub that can be easily processed, has excellent productivity, and can accurately mount an optical element such as a small optical isolator element.

  A fiber stub with an optical element according to an embodiment of the present invention includes a ferrule, an optical fiber inserted in a through-hole provided in an axial direction from a front end surface to a rear end surface of the ferrule, and the through end on the rear end surface. An optical element attached to cover the opening of the hole, and the projected area of the rear end surface onto the surface perpendicular to the optical axis is smaller than the projected area of the entire ferrule, and the outer periphery on the rear end side of the ferrule The surface is a tapered surface toward the rear end surface.

  In the fiber stub with an optical element, it is preferable that the rear end side outer peripheral surface has a taper angle smaller on the rear end surface side.

  The mounting surface of the optical element is preferably inside the rear end surface.

  It is preferable that a projected area of the optical element on a plane including the rear end face is equal to or smaller than an inner area of the outer periphery of the rear end face.

  Furthermore, the rear end surface is preferably an inclined surface inclined with respect to a plane perpendicular to the optical axis.

  The projected shape of the rear end surface on the surface perpendicular to the optical axis is preferably circular.

  The optical element may include a Faraday rotator.

  An optical receptacle with an optical element according to an embodiment of the present invention has a fiber stub with the optical element and a cylindrical shape, and has an opening into which a plug ferrule of an optical connector is inserted at one end and an opening at the other end. It has a sleeve into which the tip end side of the ferrule is inserted, an insertion hole, and a rear end side of the ferrule has a holder inserted into the insertion hole.

  The optical element may include a Faraday rotator, and a magnet for applying a magnetic field to the optical element may be fixed around an opening on the rear end side of the insertion hole of the holder.

  In this case, it is preferable that a counterbore hole for embedding a part of the magnet is formed around the opening on the rear end side of the insertion hole of the holder.

  And it is preferable that the said ferrule is inserted in the said holder so that the said rear end surface of the said fiber stub with an optical element may be located inside the said magnet.

  An optical module according to an embodiment of the present invention includes an optical unit having a light emitting element and the optical receptacle with the optical element, and the optical unit so that light from the light emitting element is incident on the optical element. The optical receptacle is fixed.

  According to a fiber stub with an optical element according to an embodiment of the present invention, the rear end face is provided with an optical element joined so as to cover the opening of the through hole, and the rear end face is perpendicular to the optical axis. Since the projected area is smaller than the projected area of the entire ferrule and the outer peripheral surface on the rear end side of the ferrule is a tapered surface toward the rear end surface, it is easy to process the rear end surface to a small size according to the mounting surface of the optical element. Excellent productivity. Further, the rear end face can be processed to be small according to the shape of the optical element, and the alignment of the optical element is easy.

  In the optical receptacle with an optical element, when the rear end side outer peripheral surface has a shape in which the taper angle becomes smaller on the rear end surface side, the angle formed between the rear end surface and the rear end side outer peripheral surface is sharp. In addition, since the length of the rear end side outer peripheral surface can be shortened, the length of the fiber stub can be shortened.

  When the mounting surface of the optical element is located inside the rear end surface, the optical element can be more easily aligned.

  In this case, if the projected area of the optical element onto the plane including the rear end face is equal to or smaller than the inner area of the outer periphery of the rear end face, the optical element can be easily aligned.

  In the optical receptacle with an optical element, if the rear end surface is inclined with respect to a plane perpendicular to the optical axis, the optical element is attached to be inclined with respect to the optical axis. It is possible to prevent the light reflected by the light from returning on the same optical path. In addition, the inclination direction of the inclined surface can be determined from the rear end side of the fiber stub.

  If the projected shape on the surface perpendicular to the optical axis of the rear end surface is circular, the processing of the outer peripheral surface of the rear end side of the ferrule can be facilitated.

  When the optical element includes a Faraday rotator, an optical signal can be processed on the optical path, and a compact device having a polarization selection function can be obtained.

  According to the optical receptacle according to the embodiment of the present invention, since the fiber stub having excellent mechanical strength is inserted into the holder portion, the optical receptacle can be easily assembled.

  In addition, if the optical element includes a Faraday rotator, and a magnet that applies a magnetic field to the optical element is fixed around the opening on the rear end side of the insertion hole of the holder, an optical receptacle incorporating an optical isolator shall be obtained. Can do.

  If a counterbore hole for embedding a part of the magnet is formed around the opening on the rear end side of the insertion hole of the holder, the magnet can be easily aligned and difficult to come off.

  According to an optical module according to an embodiment of the present invention, the above optical receptacle is used, and an optical module that is easy to assemble and has high functionality can be provided.

(A) is a longitudinal cross-sectional view which shows an example of embodiment of the fiber stub with an optical isolator of this invention, (b) is the perspective view which expanded the rear-end surface part of the fiber stub with an optical isolator of (a). (A), (b), (c) is a longitudinal cross-sectional view which shows the other example of embodiment of the fiber stub with an optical isolator of this invention. It is a longitudinal cross-sectional view which shows the example of the optical receptacle using the fiber stub with an optical isolator of FIG. It is a longitudinal cross-sectional view which shows the example of the optical module using the optical receptacle of FIG. It is a longitudinal cross-sectional view which shows the example of the optical receptacle using the conventional fiber stub with an optical isolator. It is a principal part longitudinal cross-sectional view which shows the example of the conventional optical fiber pigtail.

  Hereinafter, each example of the embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a longitudinal sectional view showing a cross section including a central axis of a fiber stub 4 with an optical element according to an embodiment of the present invention.

  In the fiber stub 4, the optical fiber 2 is inserted into a through hole 1 c provided in the central axis direction from the front end surface 1 a to the rear end surface 1 b of the ferrule 1 made of a ceramic material such as zirconia ceramics or alumina ceramic, or a glass material. Is. The optical fiber 2 is held on the ferrule 1 by an adhesive.

  The area of the rear end face 1b of the fiber stub 4 projected onto a plane orthogonal to the central axis of the ferrule 1 is smaller than the projected area of the ferrule 1 on this orthogonal plane. That is, the rear end surface 1 b is smaller than the cross section of the central portion of the ferrule 1. The rear end side outer peripheral surface 1e of the ferrule 1 is a tapered surface that tapers toward the rear end surface 1b having a small area.

  An opening of the through hole 1c is opened in the rear end face 1b, and the optical element 3 is placed so as to cover the opening. Since the optical fiber 2 is inserted into the through hole 1c, the optical element 3 is connected to the optical path across the optical axis of the optical fiber 2.

  The outer diameter of the rear end face 1b and the width of the optical element 3 must be at least larger than the spot diameter of a beam incident from a semiconductor laser described later. The spot diameter of the beam is generally 0.1 mm to 0.2 mm in diameter. On the other hand, it is desirable that the width of the optical element 3 be as small as possible according to cost requirements. For example, a parallelepiped shape having a width of 0.2 mm to 0.4 mm and a thickness of 0.6 mm to 1.0 mm is used. Corresponding to the size of the optical element 3, the outer diameter of the rear end face 1b is set to 0.3 mm to 0.6 mm, for example. When the beam spot diameter can be further reduced, the diameter can be further reduced. As the ferrule 1, one having an outer diameter standard of 1.25 mm or 2.5 mm is often used.

  The size of the optical element 3 and the rear end face 1b is such that even if the side face or corner of the optical element 3 is at the outer peripheral position of the outer peripheral face 1b, the opposite side face or corner opposite the side face or corner crosses the optical fiber 2. The size is on the other side. That is, the size relationship is such that the optical element 3 always covers the end face of the optical fiber 2 when the optical element 3 is attached inside the rear end face 1 b.

  The length of the rear end side outer peripheral surface 1e provided with the tapered surface of the ferrule 1 is desirable from the viewpoint of reducing the size of the fiber stub 4, but in order to shorten it, the taper angle (or the taper surface gradient angle) is increased. Then, the angle of the angle formed between the rear end surface 1b and the tapered surface becomes a large obtuse angle, and the liquid adhesive applied to the rear end surface 1b may not stay on the rear end surface 1b due to surface tension. Therefore, the taper angle should be 45 ° or less.

Therefore, when the rear end side outer peripheral surface 1e is formed of a multi-step tapered surface or a concave curved surface as shown in FIGS. ) The length L of the outer peripheral surface 1e on the rear end side on which the tapered surface is provided can be made short while α is reduced. In FIG. 2 (a), the taper surface has a two-step tapered surface with a gradient angle, but there is no problem even if the taper surface has three or more steps. FIG. 2B shows a concave curved surface in which the taper angle of the tapered surface continuously decreases from the front end surface 1a side to the rear end surface 1b side. As in these examples, it is preferable that the taper angle or gradient angle α on the rear end surface 1b side is smaller than the taper angle or gradient angle β on the front end surface 1a side.

  Further, as shown in FIG. 2 (c), it is preferable to provide a chamfered portion between the rear end side outer peripheral surface 1e and the remaining outer peripheral surface of the ferrule 1 to make the corners smooth. For example, the chamfered surface has a gradient angle C of 20 ° to 30 °. It is even better if a chamfer of about R = 0.1 mm is provided.

  The tapered surface (rear end side outer peripheral surface 1e) is not limited to a conical shape. For example, the rear end side outer peripheral surface 1e may have an elliptical cross section, or may have a polygonal pyramid shape such as a rectangular cross section. For example, the tapered surface 1e having a rectangular cross section can be produced by dicing the rear end of the ferrule 1.

  Such a ferrule 1 is manufactured as follows using, for example, a ceramic material.

  First, a ceramic cylinder such as zirconia ceramics or alumina ceramics that has been shaped and fired into a cylinder having a predetermined length is prepared. Next, the ceramic cylinder is fixed to a lathe, and the outer peripheral surface is formed by turning with a diamond grindstone. Alternatively, it is formed into a circular shape by rotating the ceramic cylinder against the rotating grindstone. Finally, after the optical fiber 2 is inserted and fixed in the through hole 1c, the back end surface 1b is set to a surface perpendicular to the optical axis in order to suppress return light due to near-end reflection to a light emitting element such as a semiconductor laser. Polishing is performed together with the optical fiber 2 so as to be inclined by 2 ° to 10 °, preferably 4 ° to 8 °.

  The rear end surface 1b is formed by obliquely polishing the cone shape of the rear end portion of the ferrule 1. For example, when the rear end portion shape of the ferrule 1 is a cone, the rear end surface 1b is formed in an elliptical shape. When the rear end face 1b is viewed from the axis on the rear end side of the ferrule 1, it looks circular. However, with respect to the outer peripheral surface of the ferrule 1, the circular center of the rear end surface 1b appears to be eccentric in the inclination direction. Thereby, the inclination direction of the rear end face 1b can be determined.

  In the case of the conventional ceramic capillary 41b shown in FIG. 6, for example, the inclination direction of the inclined rear end face needs to be determined by viewing the ceramic capillary 41b from the side. For this reason, it is necessary to mark the outer peripheral surface of the metal ferrule 42 and the like indicating the inclination direction of the inclined surface before attaching the magnet 45b or the like. Since it can be determined, the inclination direction of the rear end face 1b can be easily determined even after being fixed to the holder 12 or the like described later.

  Further, when used in an optical receptacle, the distal end surface 1a of the ferrule 1 is subjected to a curved surface polishing process of R = 7 mm to 25 mm in order to come into contact with the distal end of a plug ferrule of an optical connector (not shown).

Next, the optical isolator element 3 is bonded to the rear end face 1 b of the ferrule 1. The projected area of the optical isolator element 3 on the plane perpendicular to the optical axis is preferably equal to or less than the projected area of the rear end face 1b on the plane perpendicular to the optical axis. That is, it is preferable that the optical isolator element 3 has a size that can be installed in a region surrounded by the outer periphery of the rear end face 1b. This is so that the optical isolator element 3 bonded to the rear end face 1b can be accommodated in the rear end face 1b without protruding laterally from the rear end face 1b. Another reason is to prevent the optical isolator element from contacting the inner peripheral surface of the magnet 10.

  The optical isolator element 3 is formed by laminating a polarizer 3a, a Faraday rotator 3b, and an analyzer 3c in order. The optical isolator element 3 is rotated so that the angle of the transmission polarization plane of the polarizer 3a and the analyzer 3c is 45 °. They are cored and bonded together with an adhesive. And it cuts into the rectangular parallelepiped shape of the magnitude | size accommodated in the outer periphery of the rear-end surface 1b of the ferrule 1.

  As shown in FIGS. 1A and 1B, the optical isolator element 3 has a predetermined angle in accordance with the polishing angle of the rear end face 1b with respect to the plane in which the entrance surface and the exit surface are perpendicular to the optical axis. It is even more preferable that it is inclined and the side surface is a parallelepiped parallel to the optical axis. Since the rear end face 1b is inclined with respect to a plane perpendicular to the optical axis, in this case, the rear end face 1b has an elliptical shape. Therefore, the light incident surface and the light exit surface of the optical isolator element 3 may be rectangular and pasted so that the long side having a predetermined angle relationship with the polarization angle is in the major axis direction of the rear end surface 1b.

  The cut optical isolator element 3 is fixed by bonding to the rear end face 1b of the ferrule 1 or the like. When a liquid adhesive is dropped on the rear end surface 1b of the ferrule 1, the wet end spreads on the rear end surface 1b so as to bulge up due to the surface tension of the adhesive. When the optical isolator element 3 is placed thereon, the optical isolator element 3 moves to the center position of the rear end face 1b due to the surface tension of the adhesive, and the optical isolator element 3 is pressed against the rear end face 1b at that position. It is recommended that the adhesive be solidified.

  Thus, if the outer dimensions of the optical isolator element 3 and the outer diameter of the rear end face 1b are appropriately set, the center of the optical isolator element 3 substantially coincides with the center of the rear end face 1b using the surface tension of the adhesive. Therefore, it can be bonded so as to cover the end face of the optical fiber 2.

  Examples of the optical element 3 include a polarizer, a birefringent crystal, a polarizing beam splitter, and a wavelength filter in addition to the optical isolator element 3. By using a polarizer, a birefringent crystal, and a polarizing beam splitter, it is possible to provide a fiber stub 4 with an optical element having a polarization selection function. Further, when a wavelength filter is used, a fiber stub 4 with an optical element having a wavelength selection function can be provided.

  FIG. 3 shows an example of an optical receptacle 10 with an optical element using the fiber stub 4 with an optical element shown in FIG. The optical receptacle 10 with an optical element includes a holder 12 that holds the rear end portion of the fiber stub 4 with an optical element, and a sleeve 13 into which the tip side of the fiber stub 4 with an optical element is inserted. A sleeve case 14 that protects and holds the sleeve 13 may be used.

  As the material of the holder 12, a stainless material such as SUS304 having excellent corrosion resistance and weldability is often used, but a metal material capable of welding such as iron, nickel or an alloy thereof may be used.

  The holder 12 has a cylindrical shape having an insertion hole 12a at the center, and the fiber stub 4 is press-fitted into the insertion hole 12a. While applying a pressing force to the front end surface 1a of the ferrule 1 in the fiber stub 4, the rear end surface 1b is press-fitted into the insertion hole 12a from the rear end surface 1b side to a specified position near the opening opposite to the insertion hole 12a.

Next, the optical element 3 such as the optical isolator element is bonded to the rear end face 1 b of the ferrule 1. Even if the rear end surface 1b is an inclined surface, the inclination direction can be easily determined as described above, and the operation of bonding the optical element to the center position of the rear end surface 1b can be easily performed.

  Thereafter, the fiber stub 4 is inserted so that one end of the sleeve 13 covers the front end side of the fiber stub 4, and the sleeve case 14 is covered outside the sleeve 13. The sleeve case 14 is fixed by inserting into the hole.

  The sleeve 13 has a cylindrical shape made of phosphor bronze, a ceramic material, or the like, and a split sleeve that is slit in the entire axial direction can be used. In particular, a split sleeve 13 made of zirconia ceramic is often used. Moreover, you may use the precision sleeve 13 without a slit.

  The tip of a plug ferrule (not shown) for the optical connector is inserted and held in the opening on the other end side of the sleeve 13. Then, the tip surface of the plug ferrule and the tip surface of the fiber stub 4 are brought into contact with each other in the sleeve 13, whereby the optical fiber 2 in the fiber stub 4 and the optical fiber in the plug ferrule are held coaxially. Optically connected.

  The sleeve case 14 is formed in a cylindrical shape using a material such as metal or plastic. The entire split sleeve 13 is housed in a state separated from the inner wall of the sleeve case 14. Thus, when the plug ferrule is inserted into the split sleeve 13, the split sleeve 13 can be expanded in diameter.

  By the way, when the optical element 3 includes the Faraday rotator 3 b like an optical isolator, a cylindrical magnet 15 may be fixed to the rear end portion of the holder 12 so as to surround the optical element 3. As a result, a magneto-optical effect is generated in the Faraday rotator 3b and functions such as an optical isolator are exhibited.

  The magnet 15 has an inner diameter that can accommodate the optical element 3. For example, the magnet 15 has a diameter of 0.6 mm to 0.8 mm, and an outer diameter is a cylindrical shape having a diameter larger than that of the insertion hole 12 a in order to be joined around the opening of the insertion hole 12 a. Have It is preferable that the rear end surface 1b of the ferrule 1 is also disposed inside the magnet 15 because the optical element 3 is placed in the magnetic field in the magnet 15.

  For example, the magnet 15 is joined to the rear end surface 12b of the holder 12 via an adhesive or the like. Moreover, if the counterbore hole 12c which accommodates a part of magnet 15 is provided in the rear-end surface 12b of the holder 12, and the magnet 15 is adhere | attached and fixed in the counterbore hole 12c, the magnet 15 can be hold | maintained firmly. preferable. For example, as will be described later, when the optical axis of the optical receptacle 10 is aligned, even if the magnet 15 comes into contact with the lens holder 26, the magnet 15 is difficult to peel off, and the reliability is improved.

  Further, when the magnet 15 is bonded to the holder 12 via an adhesive or the like, the adhesive may flow into the insertion hole 12a side of the holder 12, but the rear end side outer peripheral surface 1e of the fiber stub 4 is a tapered surface. Therefore, a space is formed between the insertion hole 12a and the rear end outer peripheral surface 1e, and the adhesive flowing into the space is fastened. Thereby, since the adhesive for fixing the magnet 15 does not reach the optical isolator element 3, the adhesion reliability of the optical isolator element 3 is improved. Furthermore, since the fiber stub 4 and the holder 12 are bonded, the holding power of the fiber stub 4 is also improved.

  Next, FIG. 4 shows an example of an optical module 20 using the optical receptacle 10 of FIG.

The optical module 20 is obtained by joining a metal sleeve 27 of an optical unit 21 containing a light emitting element such as a laser diode (LD) and a holder 12 of the optical receptacle 10 by laser welding or the like inside a semiconductor package. In FIG. 4, peripheral elements such as wiring in the optical module 20 and other monitoring PDs (photodiodes) are omitted.

  The optical module shown in FIG. 4 includes an optical receptacle 10 with an optical isolator and an optical unit 21 attached to the rear end side.

  The optical unit 21 includes a semiconductor laser 22, a heat sink 23, a metal stem 24, a lens 25, and a lens holder 26.

  The semiconductor laser 22 is mounted on the heat sink 23 by solder. The heat sink 23 is mounted and fixed by solder, with a support portion protruding vertically on the plane of the cylindrical metal stem 24.

  The lens holder 26 is formed in a cylindrical shape so as to cover the periphery of the cylindrical surface of the metal stem 24 and is made of a material capable of resistance welding. The lens holder 26 is fixed so as to accommodate the semiconductor laser 22 and the heat sink 23. In addition, the lens 25 is fixed to the lens holder 26 on the inner periphery 26 a on the downstream side of the laser optical path of the semiconductor laser 22 with low melting point glass or the like.

  The optical receptacle 10 with an optical isolator includes a fiber stub 4 with an optical isolator, a metal holder 12, a sleeve 13, and a sleeve case 14.

  The optical module 20 adjusts the position so that the laser light emitted from the optical module 20 is coupled to the optical fiber 2 of the fiber stub 4 fixed to the optical receptacle 10, and the metal sleeve 27 of the optical module 20 at that position is adjusted. It is assembled by fixing the holder 12 of the optical receptacle 10 using spot welding or the like.

  In the optical module 20, the optical signal excited from the light emitting element 22 such as a laser diode passes through the optical isolator element 3 by the lens 25 and is collected on the end face of the optical fiber 2. The optical signal condensed on the end face of the optical fiber 2 and optically coupled to the optical fiber 2 is connected to the optical fiber of the plug ferrule that is in contact with the front end face 1a of the fiber stub 4, and transmitted to the outside of the optical connector. . The connection point between the optical fiber 2 and the optical fiber of the plug ferrule, and other optical signals that travel in the reverse direction after the optical signal is reflected are blocked by the optical isolator element 3 and returned to the light emitting element 22. Be blocked.

  In the embodiment shown in FIGS. 1 to 4, the optical element 3 fixed to the rear end face 1 b of the fiber stub 4 is an optical isolator with a magnet using the magnet 15. However, the present invention is not limited to this. Absent. Any optical element 3 that is fixed to the rear end face 1b of the fiber stub 4 and needs to be aligned with the optical fiber 2 in the fiber stub 4 may be used.

  For example, the optical element 3 may be an optical isolator that does not require the magnet 15. For example, 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, it is not necessary to fix the magnet 15 to the surrounding holder 12 after the optical isolator element 3 is bonded to the rear end face 1b provided at the front end of the fiber stub 4.

The optical element fixed to the rear end of the fiber stub 4 may be a Faraday Rotator Mirror comprising 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 rear end of the fiber stub, the return light of the laser beam can be suppressed. Further, a filter having a multilayer coating of dielectrics on the glass surface may be used.

  As described above, the fiber stub 4 with an optical element is provided with a tapered surface on the rear end side outer peripheral surface 1e on the light incident side of the fiber stub 4, and the rear end surface 1b is obliquely polished, so that the amount of polishing can be reduced and the tapered surface is formed. The working time can be reduced to less than half compared with the time required for conventional step machining. If a processing method such as rotating the grindstone side is used, it can be reduced to about 20%. Further, the axial displacement of the rear end face 1b could be reduced. Further, the ferrule 1 is less likely to have chipping or the like on the outer periphery of the rear end face 1b, can reduce the processing time, has excellent productivity, and has good mechanical strength compared to the conventional stepped fiber stub. I was able to process it.

  Further, the projected area on the surface perpendicular to the optical axis of the ferrule 1 has a rear end surface 1b smaller than the area on the cross section perpendicular to the optical axis of the ferrule 1, and the rear end side outer peripheral surface 1e of the ferrule 1 By using a fiber stub 4 having a tapered surface, a small optical isolator element 3 can be mounted with high accuracy and a fiber stub 4 having excellent mechanical strength can be provided. It is possible to provide an optical receptacle 10 and an optical module 20 that are easy to assemble and low in cost.

  The present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the scope of the present invention. For example, in the example of the above-described embodiment, the example in which the tip surface 1a side of the ferrule 1 is PC-polished has been shown. However, the fiber stub 4 with the optical element is not limited to the shape on the tip surface 1a side. For example, the tip surface 1a may not be PC-polished and the optical fiber 2 may not be cut at the tip surface 1a. By so press-fitting such an optical element-equipped fiber stub 4 into a SUS ferrule, a so-called optical fiber pigtail can be obtained.

  In the description of the above embodiment, the terms “upper, lower, left and right” are merely used to describe the positional relationship in the drawings, and do not mean the positional relationship in actual use.

1: Ferrule,
1a: tip surface,
1b: rear end face,
1e: Tapered surface,
2: Optical fiber
3: Optical element,
4: Fiber stub with optical elements,
10: Optical receptacle with optical element,
12: Holder,
12a: insertion hole 12c: counterbore hole 13: sleeve,
14: Sleeve case,
15: Magnet
20: Optical module 21: Optical unit 22: Light emitting element 23: Heat sink 24: Metal stem 25: Lens 26: Lens holder 27: Metal sleeve

Claims (12)

A ferrule, an optical fiber inserted into a through hole provided in an axial direction from the front end surface to the rear end surface of the ferrule, and an optical element attached to the rear end surface so as to cover the opening of the through hole. The projected area of the rear end surface onto the surface perpendicular to the optical axis is smaller than the projected area of the entire ferrule, and the outer peripheral surface of the rear end side of the ferrule is a tapered surface toward the rear end surface. A fiber stub with optical elements. 2. The fiber stub with an optical element according to claim 1, wherein the rear end side outer peripheral surface has a taper angle smaller on the rear end surface side. The optical receptacle with an optical element according to claim 1, wherein a mounting surface of the optical element is inside the rear end face. 4. The fiber stub with an optical element according to claim 1, wherein a projected area of the optical element onto a plane including the rear end face is equal to or less than an inner area of an outer periphery of the rear end face. 5. The optical receptacle with an optical element according to claim 1, wherein the rear end surface is an inclined surface inclined with respect to a plane perpendicular to the optical axis. 6. The optical receptacle with an optical element according to claim 1, wherein a projected shape of the rear end surface onto a surface perpendicular to the optical axis is a circular shape. The fiber stub with an optical element according to claim 1, wherein the optical element includes a Faraday rotator. A fiber stub with an optical element according to any one of claims 1 to 7, wherein the fiber stub has a cylindrical shape, and has an opening into which one end of the optical connector plug ferrule is inserted. An optical receptacle with an optical element, comprising: an inserted sleeve; and a holder having an insertion hole and a rear end side of the ferrule inserted into the insertion hole. 9. The optical element according to claim 8, wherein the optical element includes a Faraday rotator, and a magnet that applies a magnetic field to the optical element is fixed around an opening on a rear end side of the insertion hole of the holder. Optical receptacle with optical elements. The optical receptacle with an optical element according to claim 9, wherein a counterbore hole for embedding a part of the magnet is formed around an opening on a rear end side of the insertion hole of the holder. The optical receptacle with an optical element according to claim 9 or 10, wherein the ferrule is inserted into the holder so that the rear end surface of the fiber stub with the optical element is located inside the magnet. An optical unit having a light emitting element and an optical receptacle with an optical element according to claim 8, wherein the light from the light emitting element is incident on the optical element. An optical module, wherein a receptacle is fixed.

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