JP2004280043A - Receptacle having optical isolator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the full length of a receptacle having an optical isolator without deteriorating the characteristics of the receptacle and to prevent the occurrence of scratches and damages caused by projecting the optical isolator element from a magnet. <P>SOLUTION: The receptacle consists of a fiber stub whose tip surface is connected with an optical fiber, a sleeve to which the tip section of the stub is inserted to be held, a holder on which a first through-hole is formed so as to insert and fix the back tip section of the stub into the through-hole from one side, an optical isolator element in which a polarizer and a Faraday rotator are integrated and the polarizer and the back tip surface of the stub are joined and a column shaped magnetic body in which a second through-hole is formed. In the receptacle having the optical isolator, the magnet is joined from the other side of the holder, the optical isolator element is arranged in the second through-hole and the back tip surface of the fiber stub is arranged in the first through-hole. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a receptacle with an optical isolator used for optical communication.

  2. Description of the Related Art Conventionally, an optical isolator with an optical fiber is widely known, and has a structure in which an optical isolator element is joined to an end of a capillary as shown in Patent Document 1, for example, and is schematically shown in FIG. As shown in the figure, an optical isolator element 13 in which two polarizers 6 and 7 are integrated via a Faraday rotator 8 is fixed to a tip of a capillary 18, and the tip protrudes from a holder 4. The body 9 is joined to the end face of the holder 4, and has a structure in which the projecting portions of the optical isolator element 13 and the capillary 18 are arranged in the through hole 15. As described above, disposing the optical isolator element 13 in the through-hole 15 not only allows the Faraday rotator 8 to obtain the saturation magnetic field strength from the magnet body 9 but also prevents the optical isolator element 13 from being damaged by an accident. In order to

  Incidentally, the above-mentioned optical isolator element 13 is used in optical communication for preventing reflected return light from an optical component to a laser light source.

  The general function of such an optical isolator element 13 will be described with reference to FIGS. However, although the configuration is slightly different from that of FIG. 9, the components having the same function are denoted by the same reference numerals. FIG. 12 is a cross-sectional view of the polarization-dependent optical isolator element 13, and FIG. 13 shows the behavior of polarized light in the forward and reverse directions. Here, the forward direction indicates a direction in which light incident on the optical isolator is transmitted, and the reverse direction indicates a direction in which light incident on the optical isolator element is not transmitted. As shown in FIG. 12, in a general optical isolator element 13, two polarizers 6 and 7 are disposed in an outer package 20, and a Faraday rotator 8 is disposed between the polarizers 6 and 7. It is composed of a magnet 9 for applying a magnetic field to the rotor 8 and a holding member 21.

  Then, as shown in FIG. 13, in the forward direction, the light emitted from the LD 22 becomes parallel light by the lens 23 and enters the polarizer 6. After passing through the polarizer 6, the light becomes linearly polarized light, and the Faraday rotator 8 rotates the plane of polarization by 45 ° and passes through the polarizer 7. In the opposite direction, the light that has passed through the polarizer 7 is rotated by 45 degrees by the Faraday rotator 8. However, since the light becomes a polarization plane orthogonal to the transmission polarization plane of the polarizer 6 due to the non-reciprocity of the Faraday rotator 8, the light is attenuated by the polarizer 7 and does not return to the LD 22. This has the function of passing light from one direction and blocking the passage of light in the opposite direction.

By the way, in recent years, downsizing of an optical module has been demanded, so that the overall length of a receptacle, the length of a magnet of an optical isolator, and the outer diameter have been reduced. Further, with the spread of the optical access system, there has been an increasing demand for a function capable of two-way communication capable of making a call from a user, and an optical device corresponding thereto has been required.
See JP-A-2000-162475

  However, in Patent Document 1, the optical isolator element 13 is fixed to the tip of the optical capillary 18, the tip protrudes from the holder 4, and the magnet body 9 connects the projecting portions of the optical isolator element 13 and the capillary 18 with the through holes 15. When the magnet body 9 is shortened by shortening the overall length, the optical isolator element 13 protrudes from the magnet body 9 and is directly attached to the optical isolator element 13 during assembly work. There was a problem that the contact caused scratches or defects, resulting in poor appearance.

  Therefore, the flaws scatter the passing light when the light passes through the optical isolator, and the defective portion does not pass the light, so that the insertion loss characteristic is deteriorated, resulting in poor characteristics. There is a problem that is significantly worsened.

  At present, no receptacle with an optical isolator has been manufactured as a product that meets the requirements of bidirectional communication. In particular, a wavelength division filter that reflects light of a specific wavelength for bidirectional communication has been replaced with a small optical filter. There is a problem that the size is further increased when the receptacle with the isolator is provided.

  In view of the above problems, a receptacle with an optical isolator of the present invention has a fiber stub having a distal end surface connected to a plug ferrule, a sleeve for inserting and holding a distal end of the fiber stub, and a rear end of the fiber stub. An optical isolator element in which a holder having a first through-hole inserted and fixed from the side and at least two polarizers are integrated via a Faraday rotator and joined to the rear end face of the fiber stub And a columnar magnet body having a second through-hole formed therein, and the magnet body is joined from the other side of the holder, and the optical isolator element is disposed in the second through-hole. Wherein the rear end surface of the fiber stub is located in the first through hole.

  Further, a concave portion in which the magnet body is fitted may be formed on the other side of the holder, and the Faraday rotator of the optical isolator element may have a structure provided in the second through hole. Furthermore, a structure in which the entire optical isolator is provided in the first through hole and the second through hole may be employed.

  Further, the optical isolator element further includes a wavelength division filter that reflects light of a specific wavelength bonded to and integrated with the one polarizer, and the wavelength division filter has a rear end face of the fiber stub. It is characterized by being joined.

  Still further, a third through hole is formed in a side wall of the magnet so that light from the rear end face of the fiber stub can be reflected by the wavelength division filter and emitted to the outside.

  According to the configuration of the present invention, for example, in the case of a cylindrical magnet having the same residual magnetic flux density and two-sided magnetization, the magnetic field strength in a direction away from the end of the magnet body has a short width. As described above, the position of the Faraday rotator can be made as close as possible to the position of the holder by making the rear end face of the fiber stub be in the first through hole as described above. It has been found that a receptacle with an optical isolator can be provided which can shorten the entire length without deteriorating the characteristics of the rotor.

  With such a configuration, it is possible to provide a receptacle with an optical isolator capable of performing bidirectional communication corresponding to a demand for miniaturization even if an optical isolator element having an integrated wavelength division filter is attached.

  By forming a concave portion on the other side of the holder in which the magnet body fits, the overall length of the optical isolator-equipped receptacle can be further shortened, and at the same time, it serves as a guide for positioning the magnet body and joins the magnet body. It is possible to prevent an accidental accident in which the optical isolator element is brought into contact with the optical isolator element due to the positional deviation at that time and the optical isolator element is damaged.

  In addition, by disposing the Faraday rotator of the optical isolator element in the second through-hole, it is possible to stably block return light without deteriorating the characteristics of the Faraday rotator, thereby improving the isolation level. Can be provided.

  Furthermore, since the entire optical isolator element is located in the first through hole and the second through hole, the optical isolator element does not protrude from the second through hole of the magnet body, and the magnet body protects the optical isolator element and causes an accident. Thus, it is possible to provide a receptacle with an optical isolator that prevents the above accident.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. It is to be noted that the same reference numerals denote the same components in the conventional technology.

  FIG. 1 is a cross-sectional view of a receptacle with an optical isolator according to a first embodiment of the present invention. The front end of the receptacle is connected to a plug ferrule (not shown), the fiber stub 1 holding an optical fiber 2 in the center, the fiber stub 1 is fixed, and the plug ferrule is held in contact with the front end of the fiber stub 1. A sleeve 3 that surrounds the sleeve 3, a sleeve case 5 that surrounds the sleeve 3, a fiber stub 1, a sleeve 3, and a holder 4 that fixes the sleeve case 5. , 7 and one Faraday rotator 8 are joined and fixed, and the magnet body 9 is joined and fixed to the end face 12 of the holder 4 including the optical isolator element 13.

  At this time, most of the optical isolator elements 13 are arranged in the second through holes 15, and the rear end face 10 of the fiber stub 1 is in the first through holes 14.

  The present inventors have conducted intensive studies and found that, for example, in the case of a cylindrical magnet having the same residual magnetic flux density and two-sided magnetization, the magnetic field strength in a direction away from the end of the magnet body 9 has a short width. The position of the Faraday rotator 8 is made as close as possible to the position of the holder 4 by setting the rear end face 10 of the fiber stub 1 in the first through hole 14 as described above. It has been found that the overall length can be shortened without deteriorating the characteristics of the Faraday rotator 8.

  However, the Faraday rotator 8 is desirably disposed in the through hole 15 of the magnet body 9 because the magnetic field strength of the magnet body 9 further decreases from the end to the outside. As shown in FIG. 7, the concave dimension L from the bonding surface 12 of the holder 4 to the fiber position of the rear end portion 10 of the fiber stub 1 is a distance from the bonding surface 12 to the front end of the rear end portion 10 of the fiber stub 1. Is represented by A, the dimension of the obliquely polished portion from the position of the fiber 2 at the rear end 10 is represented by B, and the obliquely polished angle is represented by θ.

L = A + B sin θ
In order to obtain a sufficient magnetic field strength from the magnet body 9, it is desirable that L <polarizer thickness.

  FIG. 2 shows a sectional view of a receptacle with an optical isolator according to a second embodiment of the present invention. The difference from the structure shown in FIG. 1 is that a concave portion 16 is provided in the end surface 12 of the holder 4 and the magnet body 9 including the optical isolator element 13 is fixedly joined. Thereby, the entire length of the receptacle with an optical isolator can be further shortened, and at the same time, it serves as a positioning guide for the magnet 9, and the magnet 9 comes into contact with the optical isolator element 13 due to a positional shift when the holder 4 is joined. It is possible to prevent an unexpected accident in which the optical isolator element 13 is damaged such as a scratch or a defect. Further, since the side surface of the magnet 9 can be joined in addition to the joining surface 12, the adhesive strength can be increased.

  FIG. 3 is a sectional view showing a receptacle with an optical isolator according to a third embodiment of the present invention. Since the Faraday rotator 8 of the optical isolator element 13 completely enters the second through hole 15, the Faraday rotator 8 can obtain a sufficient saturation magnetic field strength from the magnet body 9. Can block return light and can stabilize the isolation characteristics without deteriorating.

  FIG. 4 shows a sectional view of a receptacle with an optical isolator according to a fourth embodiment of the present invention. Since the entire optical isolator element 13 is located in the first through hole 14 and the second through hole 15, the optical isolator element 13 does not project from the second through hole 15 of the magnet body 9, and the magnet body 9 is To prevent damage such as scratches or loss.

  FIG. 5 is a sectional view showing a receptacle with an optical isolator according to a fifth embodiment of the present invention. The wavelength division filter 19 has a function of reflecting light of a specific wavelength on the filter surface. Borosilicate glass or the like is used as a material for the filter.

  The wavelength division filter 19 is joined and integrated so as to match the optical surface of the polarizer 7 to constitute the optical isolator element 13. The wavelength division filter 19 is configured to be joined to the rear end face 10 of the fiber stub 1. This allows light from the optical fiber 2 to enter the wavelength division filter 19.

  Further, a third through hole 17 is formed in the side wall of the magnet body 9 so that light emitted from the optical fiber 2 on the rear end face 10 of the fiber stub 1 can be reflected by the reflection surface of the wavelength division filter 19 and emitted to the outside. are doing. The third through-hole 17 may be a notch as shown in the drawing as long as the side wall penetrates outward from the second through-hole 15.

  Since the entire optical isolator element 13 integrated with the wavelength division filter 19 is located in the first through hole 14 and the second through hole 15, the optical isolator element 13 protrudes from the second through hole 15 of the magnet 9. In addition, the optical isolator element 13 can be protected to prevent damage such as scratches or breakage.

  Further, since the third through hole 17 is formed, the signal light λ2 (up) having a predetermined wavelength from the front end face of the fiber stub 1 in the opposite direction to the LD (not shown) transmission light λ1 (down) has a wavelength. Since the light is reflected by the split filter 16 and goes out of the third through-hole 17 to the outside and is received by the light receiving device (not shown), it is possible to cope with miniaturized two-way communication.

  The stub 1 used for the receptacle in the present invention is formed to have an outer diameter of φ1.2 mm to φ2.6 mm, and may be made of glass or resin other than zirconia or alumina ceramics. The sleeve 3 can be a cylindrical sleeve, a split sleeve, or a multi-point support sleeve, and the material can be a metal such as zirconia or alumina ceramics or tin bronze. The holder 4 is preferably made of a metal that can be YAG-welded to the LD module. The sleeve case 5 is formed of a wide range of materials such as stainless steel, copper, iron, nickel, plastic, zirconia, and alumina. In particular, the sleeve case 5 is desirably formed of a material having the same thermal expansion coefficient as the holder 5 provided on the outer periphery.

  Although not shown, a connector with an optical fiber is fitted to the end of the fiber stub 1 so that signal light emitted from a laser diode (LD) (not shown) can be transmitted. In order to maintain a low connection loss with the connector, the tip portion 11 of the fiber stub 1 is subjected to PC polishing, PC polishing in which a deteriorated layer is removed, and oblique polishing and oblique PC polishing to prevent near-end reflection of an end face. I have. Further, FC connectors, SC connectors, MU connectors, LC connectors, and the like are used as connectors fitted to the receptacles.

  The polarizers 6 and 7 used in the present invention include a polarizer that absorbs a polarization direction orthogonal to a transmission polarization direction, such as a type in which dielectric particles are included in a glass substrate or a dielectric laminate type, and a birefringent crystal. The present invention can also be implemented with a polarizer that separates polarized light and shifts reflected return light from the optical path of the LD.

  Further, the Faraday rotator 8 can be implemented by a Bi-substituted garnet or a YIG garnet to which Tb, Gd, and Ho are added.

  Here, an experiment and a sample trial production in the present invention were performed.

  In the experiment, the magnetic field strength was measured at the equally divided length from the center position of the entire length of the magnet body 9 to the magnet end face, and it was confirmed whether the saturation magnetic field strength of the Faraday rotator 8 could be satisfied. The magnets used in the experiment have the same dimensions for both the inner and outer diameters, but differ in the overall length. Three types of magnets having a total length of Y, a total length of 0.65 Y, and a total length of 0.8 Y used in the prior art were used.

  From the results shown in FIG. 6, it was confirmed that the shorter the total length, the smaller the amount of decrease in the magnetic field strength at the magnet end, and satisfied the saturation magnetic field strength of the Faraday rotator. It has been found that the Faraday rotator is unsuitable because the strength of the Faraday rotator cannot satisfy the characteristics at the end of the magnet of the prior art, which is lower than the saturation magnetic field strength.

  From this, it was confirmed that it is effective to shorten the entire length of the magnet body 9 in order to shorten the entire length of the optical isolator receptacle and satisfy the isolator characteristics.

  Next, the length L shown in FIG. 7 is set so that the Faraday rotator 8 of the optical isolator element 13 bonded and fixed to the rear end portion 10 of the fiber stub 1 shown in FIG. 1 does not enter the first through hole. As shown in FIG. 10, 40 samples of the Faraday rotator 8 in the first through-hole were prototyped.

  The manufacturing method is described below. A glass substrate containing a 0.2 mm thick polarizer 6 or 7 containing a dielectric material such as a metal and a wafer of a Faraday rotator 8 are fixed with an adhesive, and this assembly and another polarizer 6 or 7 are optically adjusted. After that, the wafer was fixed with an adhesive to produce a wafer for an optical isolator. At this time, the light transmitting surface of the polarizer 6 on the side where the LD emission light is incident is coated with an anti-air AR coating, and both surfaces of the light transmitting surface of the Faraday rotator 8 are coated with an adhesive AR coating. .

  In the optical receptacle, the rear end 10 of the fiber stub 1 into which the optical fiber 2 is inserted and fixed is press-fitted or fixed to the holder 4, the sleeve 3 is inserted into the tip 11, and they are press-fitted or inserted into the sleeve case 5. Adhesively fixed.

  The manufactured wafer is manufactured by dicing or the like so that the light passing surface side is cut into a rectangle of 0.5 × 0.6 mm. The polarization transmission direction of the incident side polarizer 6 of the manufactured optical isolator element 13 was set to be parallel to 0.5 mm, and was fixed to the rear end face 10 of the fiber stub 1 with an adhesive. Next, the cylindrical magnet body 9 was arranged on the outer periphery of the fiber stub 1, and the magnet body 9 and the end face 12 of the holder 4 were fixed with an adhesive.

  From the results of the trial production shown in FIG. 8, the sample of the present invention shown in FIG. 1 can obtain better isolation and sufficiently satisfy the desired standard. It was found that the sample No. did not supply the desired magnetic field strength to the Faraday rotator 8 and thus the polarization plane did not have the desired rotation angle, and the isolation characteristics were deteriorated as compared with FIG.

  Further, fifty samples of the embodiment of the present invention shown in FIG. 1 and 50 samples of the embodiment shown in FIG. 11 were manufactured on a trial basis, and the occurrence frequency of appearance defects was compared depending on whether or not the polarizer 6 protruded from the magnet body 9. As a result, as compared with the sample of the embodiment of the present invention shown in FIG. 1 and the sample of the embodiment of the present invention shown in FIG. It was confirmed that the structure that did not protrude from the body 9 was sufficiently effective in preventing appearance defects.

1 is a cross-sectional view of a receptacle with an optical isolator according to a first embodiment of the present invention. It is sectional drawing of the receptacle with an optical isolator which is 2nd Embodiment of this invention. It is sectional drawing of the receptacle with an optical isolator which is 3rd Embodiment of this invention. It is sectional drawing of the receptacle with an optical isolator which is 4th Embodiment of this invention. It is sectional drawing of the receptacle with an optical isolator which is 5th Embodiment of this invention. It is data showing the saturation magnetic field strength of the magnet used in the receptacle with the optical isolator. It is the schematic which shows the concave amount of the fiber stub rear end surface in a receptacle with an optical isolator by numerical formula. 11 is a diagram illustrating isolation characteristics between the embodiment of the present invention shown in FIG. 1 and the embodiment shown in FIG. It is sectional drawing of the conventional optical isolator. FIG. 4 is a cross-sectional view illustrating a state where a fiber stub pull-in amount is large in a receptacle with an optical isolator. FIG. 4 is a cross-sectional view showing a state in which a polarizer protrudes from a magnet in the receptacle with an optical isolator. It is sectional drawing of the conventional polarization dependent optical isolator. FIG. 4 is a diagram illustrating the behavior of forward and backward polarized light in a polarization-dependent optical isolator.

Explanation of reference numerals

1: fiber stub 2: optical fiber 3: sleeve 4: holder 5: sleeve case
6: Polarizer 7: Polarizer 8: Faraday rotator 9: Magnet 13: Optical isolator element 14: First through hole 15: Second through hole 16: Depression 17: Third through hole 19: Wavelength division filter

Claims (6)

A fiber stub having a distal end surface connected to the plug ferrule, a sleeve for inserting and holding the distal end of the fiber stub, and a holder having a first through hole for inserting and fixing the rear end of the fiber stub from one side; An optical isolator element in which at least two polarizers are integrated via a Faraday rotator and bonded to the rear end face of the fiber stub, and a columnar magnet body having a second through hole formed therein Wherein the magnet body is joined from the other side of the holder, and the optical isolator element is disposed in the second through hole. In the receptacle with the optical isolator, the rear end face of the fiber stub is the first through hole. A receptacle with an optical isolator, wherein the receptacle is located inside. 2. The receptacle with an optical isolator according to claim 1, wherein a concave portion is formed on the other side of said holder to fit said magnet body. 3. The receptacle with an optical isolator according to claim 1, wherein the Faraday rotator of the optical isolator element is provided in the second through hole. The receptacle with an optical isolator according to any one of claims 1 to 3, wherein the entire optical isolator is provided in the first through hole and the second through hole. The optical isolator element further includes a wavelength division filter that reflects light of a specific wavelength bonded to the one polarizer and integrated, and the wavelength division filter is bonded to a rear end face of the fiber stub. The receptacle with an optical isolator according to any one of claims 1 to 4, characterized in that: 6. The side wall of the magnet body, wherein a third through hole is formed to allow light from the rear end face of the fiber stub to be reflected by the wavelength division filter and emitted to the outside. The receptacle with the optical isolator according to any one of the above.

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