JP4206366B2 - Optical receptacle and splice loss measurement method - Google Patents

Description

  The present invention relates to an optical receptacle that can be used as one component of a transmission / reception module for optical communication and can reduce connection loss, and a connection loss measurement method for measuring the connection loss.

  The recent trend of the optical communication market is to replace the fiber to the home (FTTH) and fiber to the building (FTTB) methods, which have been the mainstream until now, fiber to the premises (the ultimate goal of optical communication). (FTTP) is being promoted.

  In pursuing this system, the Passive Optical Network (PON) system including the 1:32 single star system in which the center and each subscriber's house are directly connected by an optical fiber is a promising communication system. It is becoming a simple method.

  This system is a system in which a branching device (splitter) is inserted in the middle of an optical fiber from a telephone station to a subscriber's house, and is branched by the splitter and drawn into a plurality of subscriber houses. By adopting this method, the cost per subscriber can be kept low by sharing some sections (optical fiber and transmission equipment) with a plurality of subscribers.

  Therefore, if this method is adopted, the economics of the optical module used is pursued, and the regional characteristics of the United States are taken into consideration, the optical output as the module needs to correspond to a distance of 20 km with a dynamic range of 25 dB or less. .

  In response to this request, the following performance is calculated. That is, the loss due to the branching unit is 17.5 dB, the loss due to the 20 km line is 3 dB, the connection loss of the connector is 0.5 dB (assuming a 4-stage connection point, the loss due to the splice connection point is 2 dB, and the margin is 1 dB).

  In such a demand, the connection loss of the connection portion of the receptacle is at most 0.5 dB as in the prior art, and it is difficult to construct such a communication system, and it is not possible to increase the dynamic range of optical output. It has become clear that it will be a major challenge for the construction of FTTP, where economic efficiency is the most important issue.

  Therefore, reducing the connection loss of the receptacle is the most effective means for satisfying the economy and satisfying the performance. Therefore, the reduction of the connection loss of the receptacle has been greatly screamed.

  To reduce the connection loss of the receptacle, concentricity (ratio of inner diameter to outer diameter of the through hole), inner diameter, hole collapse (change in concentricity near the inner diameter tip) during fiber stub performance It is required to define not only the standard values but also the distribution of these characteristics. In order to realize low loss, the connection loss of the split sleeve and the relationship between the outer diameter of the optical fiber and the inner diameter of the ferrule are required.

  The demand for reducing the loss of the receptacle is that not only the connection loss to the master connector but also the connection loss within a specified optical connector group within the specified probability range, for example, random connection, due to the characteristics of connection loss. Therefore, 97% or more is required to achieve a reduction in loss by satisfying 0.1 dB.

  In response to such a request, a random connection is statistically processed and calculated using a simulator that calculates a statistical distribution of connection loss. Concentricity, inner diameter, hole collapse, etc., which are the performance of conventional fiber stubs A product that satisfies the performance cannot be provided by a guarantee method (for example, a concentricity of 0.5 μ or less) that passes the performance of the product if it satisfies the value specified in the standard that stipulates that it falls within a certain range. Has occurred.

  Here, the structure of a conventional optical receptacle is shown in FIG. As shown in FIG. 4, the optical receptacle metal fitting 1 having a through hole 1a, a fiber stub 40 whose rear end is press-fitted into the through hole 1a, and the tip of the fiber stub 40 are inserted from one opening. And a cylindrical metal fitting 2 that covers the sleeve 3 and is fixed to the metal fitting 1. In the fiber stub 40, the fiber 5 is inserted into the inner diameter of the ferrule 4, the tip of the ferrule 4 is formed by the PC surface 6, and the other is formed by the oblique polishing surface 7. The fiber stub 40 is inserted into the through hole 10 of the metal fitting 1 and the sleeve 2 is attached, and then the metal fitting 2 is attached.

The function of the receptacle 8 is to connect by connecting the PC surface 6 of the fiber stub 4 to the connector, and the end surface 7 has a function to connect to the laser diode without connecting the return light. (See Patent Document 1).
Japanese Patent Laid-Open No. 10-332988

  However, in the optical receptacle 8 having the conventional structure, when the fiber stub 40 is inserted into the sleeve 3 in which the slit 30 is formed, the connection loss varies depending on the direction in which the connection loss is connected to the adapter portion (not shown, the same applies hereinafter). Had problems. Although the range of this variation has not been a problem with conventional requirements, it may become a problem of product yield in the modern requirements for realizing a low loss as described above. There was a need to provide an optical receptacle.

  In addition, for the construction of FTTP, there is a demand for a structure of an optical receptacle in which connection loss is reduced in order to satisfy economy and satisfy performance.

  As a result of intensive studies on the connectivity between the optical receptacle and the adapter portion, the present inventor has found that when the optical receptacle is attached to the adapter portion, the slit in the rotation direction of the sleeve with respect to the attachment direction of the adapter portion as shown in FIG. Although there is variation at the position, the inventors have found that the connection loss is improved when the slit is directed downward, and have reached the present invention. There are various reasons for this, but in the standard on the adapter part side, since there is a mechanism to connect at the upper part on the adapter part side, a high stress is applied on the upper side at the time of connection. It is considered that the connection loss is deteriorated when the optical axis of the fiber stub is shaken when the stub is positioned on the upper side.

  Accordingly, the present invention provides a fiber stub whose front end surface is connected to the plug ferrule, a sleeve in which a slit is formed in the longitudinal direction to insert and hold the front end of the fiber stub, and the rear end of the fiber stub is on one side. An optical receptacle comprising a holder having a first through-hole inserted and fixed from a plurality of second through-holes formed around the side surface of the holder toward the first through-hole, and the second through-hole It is preferable to provide an optical receptacle characterized in that a positioning pin that is fixed while being engaged with the slit is disposed on at least one of the above.

  The positioning pin has a diameter smaller than the width of the slit of the sleeve, is formed larger than the diameter of the second through-hole, and provides an optical receptacle characterized in that the positioning pin is press-fitted into the holder. Good.

  Furthermore, it has a pictail having a first measurement fiber stub in which an optical fiber connected to a measurement light source is inserted and fixed, and a first precision sleeve and a third through hole for inserting the first measurement fiber stub on one end side. An optical unit comprising a light source metal fitting for press-fitting the first precision sleeve and holding a lens for condensing light from the pictail; a receptacle metal fitting having a fourth through hole; The second precision sleeve and the rear end portion to be press-fitted are inserted into the second precision sleeve, and the optical receptacle (hereinafter referred to as “measurement object”) according to claim 1 is inserted into one opening of the sleeve. A positioning unit comprising a second measurement fiber stub positioned by positioning the measured object with the positioning unit. In the connection loss measurement method for measuring the receptacle connection loss by condensing light from the measurement light source on the optical fiber end surface of the stub, the fiber stub of the object to be measured is press-fitted into the first through hole of the holder, Press-fit from one end to the tip of the fiber stub, and measure the connection loss while rotating the sleeve while the tip is in contact with the tip of the second measuring fiber stub inserted from the other end of the sleeve. And determining the rotation direction of the sleeve that minimizes the connection loss, and positioning the holder and the sleeve by inserting a positioning pin into the second through hole corresponding to the slit at the determined position. A loss measurement method may be provided.

  Further, it is preferable to provide a connection loss measuring method characterized in that the mode field diameter of the first measurement fiber stub is formed to be equal to or smaller than the mode field diameter of the fiber stub.

  Further, the positioning unit includes a pressing member that elastically presses and contacts in the axial direction in a state where the tip surface of the second measurement fiber stub coincides with the tip surface of the fiber stub of the object to be measured. It is preferable to provide a connection loss measuring method characterized by comprising a stopper for preventing the movement in the axial direction.

  According to this invention, while having the some 2nd through-hole formed toward the said 1st through-hole around the side surface of the above-mentioned holder, engaging the said slit with at least one of the said 2nd through-hole. Since the fixed positioning pin is arranged, the sleeve can be fixed at the lower position in the rotational direction of the sleeve with the least connection loss. After that, even if the plug ferrule is inserted, the sleeve rotates due to external stress. Therefore, it is possible to manufacture a receptacle that maintains a low connection loss even when insertion and extraction are repeated.

  In addition, since the position of the slit is fixed at the low loss position, it is possible to improve the manufacturing yield of the low loss optical receptacle.

  Furthermore, if the above-described connection loss measurement method is used, the connection loss due to the fiber stub and the sleeve, which are three elements of the connection loss that is considered to occur in the receptacle, the connection loss due to the press-fitting angle with the slant polished surface, and the metal fitting, the dirt It is possible to precisely measure the connection loss as a total amount of connection loss due to foreign matter.

  Therefore, the connection loss on the PC surface can be expected to be close to 0.1 dB (at the time of random connection) or less, and the performance improvement is about 0.4 dB from the connection loss of 0.5 dB that has been estimated conventionally. It becomes possible.

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

  FIG. 1 is a cross-sectional view of an apparatus for explaining a method for measuring a receptacle connection loss according to the present invention. FIGS. 2 (a) and 2 (b) are cross-sectional views for explaining steps for manufacturing the apparatus. FIG. It is sectional drawing which shows a certain optical receptacle.

  First, as shown in FIG. 3, the optical receptacle of the present invention, which is the object to be measured, has a cylindrical fitting (holder) 1 having a through-hole 1a having a cup shape that penetrates the center and gradually expands on one side, and a slit 3a. A fiber stub 40 is formed by inserting the optical fiber 5 into the center of the sleeve 3 and the ferrule 4 formed in the longitudinal direction, the tip portion of the ferrule 4 being formed by the PC surface 6, and the other being formed by the oblique polishing surface 7. The cylindrical metal fitting 2 can be press-fitted into the cup-shaped side of the through hole 1a of the metal fitting 1.

  Then, the rear end portion of the fiber stub 40 is press-fitted into the through hole 1 a of the metal fitting 1, the front end portion of the fiber stub 40 is inserted from one opening of the sleeve 3, and the metal fitting 2 is attached so as to cover the sleeve 3. 1 is fixed to the cup-shaped through hole 1a.

  A feature of the present invention is that a plurality of through holes 9 are provided up to the through hole 1a on the outer periphery of the metal fitting 1 formed in a cylindrical shape, and the apparatus using the connection loss measuring method shown below is used. By rotating the sleeve 3, the slit 30 is aligned with the through hole 1 a having the lowest connection loss between the slit 30 of the sleeve 3 and the fiber stub 40, and the positioning pin 10 is press-fitted and fixed at that position. The optical receptacle is completed by attaching the metal fitting 2 to the metal fitting 1 by press fitting. Since the through hole 1a is a hole, the shape of the path is not limited to a cylindrical shape, and may be a groove shape.

  Here, it is preferable that the positioning pin 10 to be used has a diameter smaller than the width of the slit 30 of the sleeve 3 and is larger than the diameter of the through hole 9. This is because the slit 30 of the sleeve 3 originally has a role of holding the ferrule 4 by being deformed when the ferrule 4 is inserted, and the function when the diameter larger than the slit 30 is inserted. It is because it will be damaged.

  The fiber stub 4 used for the optical receptacle 8 uses, for example, a ferrule with very precise concentricity and inner diameter, and uses a fiber that matches the inner diameter, thereby realizing low loss. In the same manner, for example, by using the sleeve 3 for low loss in which the roundness and cylindricity of the inner diameter are controlled and the realization of low loss is guaranteed, the connection loss described later is used. Can be minimized.

  Further, the structure of the positioning pin 10 shown in FIG. 1 is merely an example, and is not limited to this. An appropriate mechanism is provided in the metal fitting 1 or the metal fitting 2, and the slit 30 of the sleeve 3 is used by utilizing this mechanism. It is preferable to have a function of stopping the rotation of the sleeve 3 by using.

FIG. 2 shows another structural example of the present invention. In the figure, a slit 31 is formed in the metal fitting 1 in the longitudinal direction, and a positioning pin 10 is attached to the bottom of the slit 31. Thereby, the effect that the process of the holder 1 is easy compared with FIG. 3 is acquired.

  Next, an apparatus in which the receptacle connection loss measuring method of the present invention is used includes an optical unit 11 and a positioning unit 21 connected to a measurement light source as shown in the figure.

  As shown in FIG. 1, the optical unit 11 is made of metal and is formed in a cylindrical shape, and has a pictail 14 having a fiber stub 14a in which an optical fiber 140 connected to a measurement light source is inserted and fixed, and one end side. A precision sleeve 13 for inserting a fiber stub 14a and a metal fitting 12 for a light source for holding a lens 16 having a through-hole 12a and press-fitting the precision sleeve 13 and collecting light from the pictail 14 are formed. A stopper 15 is press-fitted into the precision sleeve 13 so that the tip of the fiber stub 14a contacts and is positioned. The lens 16 is fitted in a counterbore formed around the exit of the through hole 12a, and screws 17 for adjusting the angles θ and ψ of the light beam passing through the lens 16 are arranged at four points around the lens 16 (in the drawing). Is visible so that two points can be seen). Note that the angles θ and ψ of the light beam are adjusted in the X and Y directions of the screw 17 so that a circular light beam is output. Here, the angle θ refers to the inclination of the lens with respect to the X axis, for example, and the angle ψ refers to the inclination with respect to the Y axis, for example. In addition, the precision sleeve 13 is attached to the optical unit 11, and then the inner diameter is ground again to improve the inner diameter accuracy, whereby the precision of the inner diameter of the sleeve and the cylindricity are precisely manufactured. The same shall apply hereinafter.

  Then, a precision sleeve 13 is embedded in the metal fitting 12 by press-fitting, and a pigtail 14 using a fiber 140 whose mode field is smaller than the fiber 5 used in the receptacle 8 described later is inserted, and the position determined by the stopper 15 Fixed to. The light emitted from the pigtail 14 is condensed by the lens 16. This is capable of absorbing 0.2 μm of accuracy of precision sleeves 13 and 23, which will be described later, used for adjusting the optical axis, and 0.5 μm of cylindricity of the long ferrule 30 described later. The mode field diameter of the optical fiber 140 used for the fiber stub 14a at this time is preferably about 1 μm smaller than the optical fiber 5 of the fiber stub 4.

  The pigtail 14 receives light output from a laser diode (not shown) provided in the measurement light source. The reason why this pigtail 14 is used as the light source is that if the light source has an aspect ratio, the connection efficiency differs as a result. As a result, the connection efficiency becomes a value specific to the light source to be used. Because it is not appropriate.

  Thus, after adjusting the angles θ and ψ, the lens 16 is accurately fixed with UV resin, YAG, solder, or the like.

  On the other hand, the positioning unit 21 includes an L-shaped metal fitting 22 and a connector 25 made of metal.

  The connector 25 has a fiber stub 27 that is inserted from the other side of the sleeve 3 of the receptacle 8 and abuts against the distal end surface of the fiber stub 4. The fiber stub 27 is provided to detect the light beam that has passed through the receptacle 8, and the tip surface of the fiber stub 27 abuts on the PC surface 6 of the fiber stub 4. Further, the rear end portion of the fiber stub 27 includes a spring 28 that elastically presses the PC surface 6 of the fiber stub 4 in the Z direction (axial direction) and a latch 26 that connects the metal fitting 22. .

  A through hole 22 a is formed in the metal fitting 22. A precision sleeve 23 is press-fitted in the through hole 22a to hold the fiber stub 27, and the movement of the receptacle 8 in the Z direction by the pressed fiber stub 27 moves in the Y direction and is prevented. A stopper 29 made of a cylindrical body is provided. The stopper 29 is configured such that a through-hole 29 a is formed on the side of the metal fitting 22 where the receptacle 8 is disposed, and the precision sleeve 24 is press-fitted into the through-hole 29 a and can be inserted into the precision sleeve 24. The movement error in the Z direction of the receptacle 8 is absorbed.

  In the positioning unit 21, the connector 25 is fixed to the metal fitting 22 by the latch 26. The fiber stub 27 constituting the connector 25 is disposed so as to protrude through the precision sleeve 23, and the above-described spring 28 is attached to the other end of the protrusion.

  When the receptacle 8 is attached to the receptacle connection loss measuring apparatus having such a structure and the receptacle 8 is fixed using the stopper 29, the receptacle 8 is made of the metal fitting 1 and the stopper 29, and the ferrule only by the spring 28, the fiber stub 27 and the split sleeve 3. The position of the fiber 5 on the four obliquely polished surfaces 7 is determined.

  Then, after the ferrule 4 is press-fitted into the metal fitting 1 in the receptacle 8, the position of the oblique polishing surface 7 on the reference surface (end surface of the metal fitting 1) can be created with an accuracy of approximately ± 10 μm at present. When the oblique polishing surface 7 is irradiated, if the position adjustment is performed by the lens 16 so that the convergent light from the measurement light source forms a beam waist, the size of the beam diameter does not change within this degree of positional accuracy. In addition, since the mode field of the optical unit 11 is small, almost 100% of the light beam can be connected.

  Further, the clad mode light generated at the time of connection at the oblique polishing surface 7 is totally reflected by the core when passing through an optical fiber (not shown) connected to the connector 25, so that the light is scattered outside the clad. Therefore, since the optical fiber is attenuated until it passes through a certain distance, the cladding mode light can be effectively attenuated by setting it to 2 m or more, and the connection loss of the receptacle can be accurately measured.

  Next, the optical axis adjustment of the optical unit 11 and the positioning unit 21 will be described. This adjustment of the optical axis is very important in forming the receptacle connection loss measuring apparatus of the present invention. The reason is that the measurement accuracy of the connection loss is obtained unless the light beam from the pigtail 14 enters the receptacle 8 along the optical axis and is connected to the connector 25 by the connection with the PC surface 6 and is emitted to the photodetector. Or the mounting position dependency is increased, and accurate connection loss measurement is hindered.

  Basically, in order to perform a correct measurement, it is required that the optical axis of the receptacle 8 and the optical axis of the optical unit 11 coincide. This requirement is to match the optical axis of the fiber stub 27. Accordingly, this results in matching the optical axes of the precision sleeve 13 of the optical unit 11 and the precision sleeve 23 of the positioning unit 21. For this reason, this is achieved by the method shown in FIG.

  As shown in FIG. 2A, the optical axis of the positioning unit 21 and the optical unit 11 without the lens 16 are made to coincide with each other by using a precision long ferrule 30 (precision cylinder) created by a ferrule manufacturing technique. Then, the position of these two precision sleeves 13 and 23 can be fixed with an accuracy of ± 0.5 μm or less. If the sleeves 13 and 23 used in such an apparatus are selected, this accuracy can be ± 0.2 μm.

  After aligning the optical axes in this way, the positioning unit 21 and the optical unit 11 are fixed apart by a necessary interval.

Next, as shown in FIG. 2 (b), the long ferrule 30 is removed, and the fiber stubs 14a and 27 are inserted into the precision sleeves 13 and 23, and the lens 16 is mounted and the screw 17 is adjusted according to the required position. After the connection loss is maximized, the lens 16 is fixed. In this case, a stopper for accurately fixing the position of the fiber stub 14a may be press-fitted into the precision sleeve 13. By adjusting the optical axes of the optical unit 11 and the positioning unit 21 by the method described above, The desired optical axis can be adjusted.

  Finally, the connector 25 with the fiber stub 27 as shown in FIG. 1 is attached, the length of the stopper 15 is adjusted, the fiber stub 14a is connected to the oblique polishing surface 7, and then the stopper 29 is attached to measure. Complete the device.

  Then, the optical receptacle 8 as described above (with no metal fitting 2 attached) is inserted into the fiber stub 27, the holder 1 is fixed, and the connection loss is reduced while rotating the sleeve 3 so as to rotate according to the through hole 9. taking measurement. Then, the rotation is stopped at the position of the through-hole 9 facing the slit 30 of the sleeve 3 that causes the smallest connection loss, and then the position is fixed by the positioning pin 10. Then, the optical receptacle 8 is removed, and the metal fitting 2 is press-fitted and fixed to the metal fitting 1 to complete the optical receptacle.

  The present invention was created with the following configuration. A fiber stub 4 having an outer diameter of 2.5 mmφ was prepared using a low-loss ferrule. The inner diameter of the ferrule was 125.0 to 125.5 μm, and assembly was performed using the optical fiber 5 having an outer diameter of 124.8 μm. The length of the fiber stub 4 is 5 mm, and a press-fitting part 2 mm and a mounting part 3 mm of the sleeve 3 are secured. The normal fiber stub 4 has an inclined end surface 7. In order to avoid connection loss due to the end surface 7, the surface is a vertical surface, AR coating is applied to this surface, and a reflectance of −31 dB is secured on the surface. I can do it.

  The sleeve 3 has a low connection loss and has a length of 6 mm and a connection loss of 0.02 dB. The through hole 9 was 0.8 mm. The dimension of the positioning pin 10 was 0.4 mm at the tip portion and 0.43 mm at the rear portion.

  In the assembly, first, four through holes 9 penetrating to the through hole 1a were formed in the metal fitting 1, and the fiber stub 4 was press-fitted into the through hole 1a, and the sleeve 3 was covered at this stage. Thereafter, the connection loss is measured by the measuring apparatus shown in FIG. 1, and the position of the four through holes 9 at which the connection loss is reduced is compared while rotating the sleeve 3, so that the connection loss is minimized. The positions of 30 opposing through holes 9 were determined. The stopper 10 was press-fitted into the hole 9 and attached together with the slit 30 of the sleeve 3, and then the shell 2 was press-fitted to complete the receptacle.

  Next, when the receptacle 8 was attached to the measuring apparatus and the connection loss was measured again, 0.7 dB was obtained as the connection loss.

It is sectional drawing of the apparatus explaining the receptacle connection loss measuring method of this invention. (A), (b) is sectional drawing explaining the step which manufactures the apparatus. (A) is sectional drawing of the optical receptacle in this invention, (b) is a perspective view explaining a sleeve. It is sectional drawing of the other optical receptacle of this invention. It is a figure explaining the relationship between the position of the rotation direction of the slit of a sleeve, and a connection loss. It is sectional drawing which shows the structure of the conventional optical receptacle.

Explanation of symbols

1 Bracket 2 Bracket 3 Sleeve 4 Ferrule 5 Fiber 6 PC surface 7 Polishing surface 8 Optical receptacle

Claims (5)

A fiber stub whose front end surface is connected to the plug ferrule, a sleeve in which a slit is formed in the longitudinal direction to insert and hold the fiber stub, and a rear end of the fiber stub is inserted and fixed from one side. An optical receptacle comprising a holder having a through hole has a plurality of second through holes formed toward the first through hole around a side surface of the holder, and at least one of the second through holes has the above-mentioned An optical receptacle comprising a positioning pin that is fixed while being engaged with a slit. 2. The optical receptacle according to claim 1, wherein the positioning pin has a diameter smaller than a width of the slit of the sleeve, is formed larger than a diameter of the second through hole, and press-fits the positioning pin into the holder. . A pictain having a first measurement fiber stub in which an optical fiber connected to a measurement light source is inserted and fixed, a first precision sleeve for inserting the first measurement fiber stub on one end side, and a third through hole. 1 an optical unit comprising a metal fitting for a light source for press-fitting a precision sleeve and holding a lens for collecting the light from the pictail;
A receptacle metal fitting having a fourth through hole, a second precision sleeve press-fitted into the fourth through hole, and a rear end portion inserted into the second precision sleeve, and a tip portion according to claim 1. A positioning unit consisting of a second measurement fiber stub that is positioned by inserting a "measurement object") into one of the openings of the sleeve;
In the connection loss measurement method for measuring the receptacle connection loss by condensing the light from the measurement light source on the optical fiber end face of the fiber stub in the state where the object to be measured is positioned by the positioning unit,
After the fiber stub of the object to be measured is press-fitted into the first through hole of the holder, it is press-fitted from one end of the sleeve to the tip of the fiber stub, and the tip is inserted from the other end of the sleeve. While measuring the connection loss while rotating the sleeve in contact with the tip of the fiber stub, the rotation direction of the sleeve that minimizes the connection loss is determined, and the second corresponding to the slit at the determined position. A connection loss measurement method comprising positioning a holder and a sleeve by inserting a positioning pin into a through hole. 4. The connection loss measuring method according to claim 3, wherein a mode field diameter of the first measurement fiber stub is formed to be equal to or smaller than a mode field diameter of the fiber stub. The positioning unit includes a pressing member that elastically presses and abuts in the axial direction in a state in which the tip surface of the second measurement fiber stub coincides with the tip surface of the fiber stub of the object to be measured, and the shaft that is pressed The connection loss measuring method according to claim 3, further comprising a stopper that prevents movement in a direction.

Images