JP2005157147A - Optical receptacle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems in which connection loss increases since a fiber stub is not stably held because of less holding strength for the fiber stub 2 by a sleeve 4 as the sleeve insertion length L1 of the fiber stub 2 is made short and an optical fiber 7 do not come into contact when abutting against a plug ferrule 20, and further reproducibility of the connection loss deteriorates since the fiber stub 2 is held by the sleeve 4 differently each time the optical fiber abuts. <P>SOLUTION: The optical receptacle includes the fiber stub having at least one small-diameter hole, the optical fiber held in the small-diameter hole, and the holder where one end of the fiber stub is pressed in and held, and is characterized in that the sleeve for holding a plug ferrule abutting against the optical fiber is held at the opposite end of the fiber stub and a holder-side end surface of the optical fiber held in the fiber stub is caved in a holder-side end of the fiber stub. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical receptacle used for optical communication, optical information processing, an optical sensor, and the like.

  Conventionally, in order to convert electrical signals and optical signals to each other, light emitting and receiving elements such as semiconductor lasers and photodiodes are housed in a case, and this case is provided facing the optical fiber, and the optical signal is transmitted through the optical fiber. An optical device for introducing or deriving is disclosed.

  Here, the one that houses the semiconductor laser in the case and derives the optical signal is called a light emitting module, and the one that houses the photodiode in the case and introduces the optical signal is called a light receiving module. is called.

  Among the above optical modules, as shown in FIG. 11, a receptacle-type optical module 21 is provided with a light emitting and light receiving element 9 at one end of an optical receptacle 2 and a plug ferrule 20 connected to the other end to introduce or derive an optical signal. Has been devised (see Patent Document 1).

  The optical receptacle 1 was obtained by inserting and fixing a ferrule 6 made of a ceramic material such as zirconia or alumina, and an optical fiber 7 made of quartz glass or the like in a small-diameter hole 6a of the ferrule 6 as shown in FIG. The fiber stub 2 is configured by fixing the rear end portion of the fiber stub 2 to the holder 3 by press-fitting, inserting the tip portion into the inner hole of the sleeve 4, and press-fitting or adhesively fixing them to the sleeve case 5.

  Furthermore, when the optical module 21 shown in FIG. 11 is configured by using the optical receptacle 1 described above, a case 22 having a light emitting / receiving element 9 and a lens 8 is provided on the rear end side of the optical receptacle 1 with a spacer. After the optical adjustment, each is fixed by spot welding with a YAG laser, and the light emitting / receiving element 9 and the optical fiber 7 are optically connected via the lens 8.

  Further, the plug ferrule 20 is inserted into the sleeve 4 from the distal end side of the optical receptacle 1 so that the end face of the optical fiber 7 on the optical receptacle 1 side and the end face of the optical fiber 7 on the plug ferrule 20 side are brought into contact with each other. Can be exchanged.

  The end surface on the sleeve 4 side of the fiber stub 2 is mirror-polished to a curved surface with a radius of curvature of about 5 to 30 mm in order to reduce the connection loss due to contact between the optical fibers 7, and the end surface 2 a on the holder side receives an optical signal. In order to prevent the reflected light generated when passing through the light source from returning to the light source side, it is mirror polished to an inclined surface of about 4 to 10 ° together with the ferrule 6 holding the optical fiber 7.

Further, in the light emitting module 21 shown in FIG. 12 as an example of an optical receptacle with an optical isolator, in order to prevent the reflected return light from the optical path from entering the semiconductor laser side and the transmission of the optical signal becoming unstable, A configuration in which an optical isolator element 18 is arranged on the holder-side end surface 2a of the optical receptacle 2 has been devised.

  The optical isolator has a function of transmitting forward light and blocking reverse light.

  The light emitted from the semiconductor laser is reflected and scattered when passing through the optical fiber and various optical elements. However, when these lights return to the semiconductor laser, the output becomes unstable and noise occurs in the signal.

  An optical isolator is used to block this return light.

  Here, an optical isolator element 18 in which a flat Faraday rotator 17 is disposed between two polarizers 15 and 16 and each is bonded with a light-transmitting adhesive is used.

This is fixed to the holder-side end surface 2a of the fiber stub 2 using a light-transmitting adhesive, and a ring-like permanent magnet 19 is applied to the outer periphery of the optical isolator element 18 in order to apply a saturation magnetic field to the Faraday rotator 17. Deploy.
JP 2001-66468 A

  In recent years, miniaturization of optical modules has been demanded, and the optical receptacle 1 shown in FIG. 10 is also demanded to be miniaturized. However, the fitting portion of the optical receptacle 1 with the plug ferrule 20 is standardized. The length L3 from the front end surface of the sleeve case 5 to the front end surface of the fiber stub 2 cannot be shortened.

  On the other hand, when the sleeve insertion length L1 of the fiber stub 2 is shortened, the holding strength of the fiber stub 2 by the sleeve 4 is reduced, so that the holding becomes unstable and the mutual optical fibers 7 are brought into contact with the plug ferrule 20. They are not in close contact with each other, resulting in poor connection loss.

  Further, since the holding state of the fiber stub 2 by the sleeve 4 is different for each contact, there is a problem that the reproducibility of the connection loss is deteriorated.

  Furthermore, since the holding state is unstable, the connecting portion between the optical fibers 7 slips, and the optical fiber 7 may be damaged, and there is a problem that the introduction and derivation of the optical signal becomes impossible.

  Further, if the holder press-fitting length L2 of the fiber stub 2 is shortened, the holding strength of the fiber stub 2 by the holder 3 is reduced, and the fiber stub 2 is affected by the impact when the plug ferrule 20 abuts and the pressing load constantly received from the plug ferrule 20. 2 shifts inside the holder 3, and the relative positions of the light emitting and light receiving elements 9 and the lens 8 are shifted, so that the respective optical connections are not made.

  Further, when the optical isolator element 18 is bonded to the holder-side end surface 2a of the fiber stub 2, the Faraday rotator 17 constituting the optical isolator element 18 needs to be disposed inside the ring-shaped permanent magnet 19, so that the fiber The holder-side end surface 2a of the stub 2 comes closer to the rear end surface of the holder 3, and the total length of the fiber stub 2 and the optical receptacle 1 becomes longer.

  In view of the above problems, the present invention provides a fiber stub having at least one small-diameter hole, an optical fiber held in the small-diameter hole, a holder for holding one end of the fiber stub by press-fitting, A sleeve for holding a plug ferrule that comes into contact with an optical fiber is held at the opposite end of the fiber stub, and the holder side end surface of the optical fiber held in the fiber stub is relative to the holder side end of the fiber stub. An optical receptacle characterized by being depressed.

  Further, the holder-side end surface of the optical fiber held in the fiber stub is recessed by 10 μm or more with respect to the holder-side end surface of the fiber stub.

  The fiber stub is provided with a tapered recess on the holder side end surface.

  In addition, a groove portion is formed on an end surface on the holder side of the fiber stub.

  Further, the optical element is bonded and fixed to the end surface on the holder side of the fiber stub.

  Further, the optical isolator element comprising at least one Faraday rotator and at least one polarizer is bonded and fixed to an end surface on the holder side of the fiber stub.

According to the configuration of the present invention, the holder-side end of the optical fiber held in the thin hole of the fiber stub is depressed with respect to the holder-side end of the fiber stub. While maintaining the press-fitting length and the insertion length to the sleeve,
It is possible to approach the lens and the light emitting / receiving element side in the optical module.

  For this reason, the total length of the optical module is shortened.

  Also, in the fiber stub in which the optical element is bonded and fixed to the holder side end of the fiber stub, the holder side end of the optical fiber is similarly depressed with respect to the holder side end of the fiber stub, The entire optical module can be shortened.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIG.

  As shown here, the optical receptacle 1 includes a fiber stub 2, a holder 3, a sleeve 4, and a sleeve case 5. The holder side rear end 2a of the fiber stub 2 is press-fitted and fixed to the holder 3, The tip is inserted into the inner hole of the sleeve 4.

  Further, the sleeve case 5 is press-fitted or bonded and fixed to the holder 3.

  In the fiber stub 2, an optical fiber 7 made of quartz glass or the like is inserted into the small-diameter hole 6 a of the ferrule 6, and the end surface on the sleeve 4 side has a radius of curvature to reduce the connection loss with the plug ferrule 20. It is processed into a curved surface of about 5 to 30 mm.

  The ferrule 6 is made of a ceramic material such as zirconia or alumina, and the sleeve 4 is made of a material such as zirconia, alumina, or copper, but the ferrule 6 and the sleeve 4 are both zirconia mainly considering wear resistance. It is preferable that it consists of ceramic materials, such as.

Furthermore, since the holder 3 is often fixed to other parts by welding when constituting an optical module, it is made of a material that can be welded, such as stainless steel, copper, iron, nickel, etc. Stainless steel is used in consideration of weldability. Since sleeve case 5 does not require wear resistance and weldability, a wide range of materials such as stainless steel, copper, iron, nickel, plastic, zirconia, and alumina are used. In order to increase the reliability mainly by matching the thermal expansion coefficient with the holder 3, stainless steel is often used in the same manner as the holder 3.

  Here, the holder-side end surface 7a of the optical fiber 7 is disposed so as to be depressed by D with respect to the holder-side end surface 2a of the fiber stub 2, and is fixed with an adhesive.

  Here, in general, when mirror-polishing the holder-side end surface 2a of the fiber stub 2, if cerium oxide powder is used as the free abrasive grains and finish polishing is performed using a buffing sheet, the end-side surface of the optical fiber 7 on the holder side 7 a is depressed about several μm from the holder-side end surface 2 a of the fiber stub 2.

  Therefore, if the holder-side end surface 7a of the optical fiber 7 is recessed at least 10 μm or more from the holder-side end surface 2a of the fiber stub 2, even if PC polishing should be performed, the holder-side end surface 7a of the optical fiber 7 is polished. Will not wrap around.

  The holder-side end surface 7a of the optical fiber 7 is cleaved or mirror-polished to an inclined surface of about 4 to 10 ° in order to prevent the optical signal from being reflected here and returning to the light source side.

  In addition, the concave portion generated by the depression of the optical fiber 7 is filled with a light-transmitting adhesive whose refractive index is matched with the core portion of the optical fiber 7. The reflection of the optical signal can be prevented.

  In this case, however, the rear end portion of the ferrule 6 filled with the light-transmitting adhesive must be mirror-polished to an inclined surface of about 4 to 10 °.

  Here, FIG. 2 shows a configuration (a) of an optical module using the optical receptacle of the present invention and a configuration (b) of an optical module using a conventional optical receptacle.

  As shown here, in the optical receptacle 1 according to the present invention, the holder-side end surface 7 a of the optical fiber 7 is recessed by D with respect to the holder-side end surface 2 a of the fiber stub 2.

  Therefore, the relative position between the holder-side end surface 7a of the optical fiber 7 and the lens 8 is the same as in the configuration (b) using the conventional optical receptacle, but the holder-side end surface 2a of the ferrule 6 and the fiber stub 2 is The lens 8 is approaching, and the entire optical receptacle is also approaching the lens 8 side. As a result, the overall dimension of the optical module is shortened by L.

  At this time, since the insertion length L1 of the fiber stub 2 with respect to the sleeve 4 is the same as that of the conventional optical receptacle and a sufficient insertion length can be obtained, the holding strength of the fiber stub 2 by the sleeve 4 can be sufficiently obtained. Can do.

  Accordingly, the holding is stable, the connection loss and the reproducibility when contacting the plug ferrule are good, and no slippage occurs in the mutual optical fiber connection portions.

  Also, the press-fitting length L2 of the fiber stub 2 with respect to the holder 3 is the same as that of the conventional optical receptacle, and a sufficient press-fitting length L2 can be obtained, so that the holding strength of the fiber stub 2 by the holder 3 can be sufficiently obtained. it can.

  Therefore, even when an impact when the plug ferrule 20 abuts or a load that is constantly received from the plug ferrule 20 is applied to the fiber stub 2, the light emission of the fiber stub 2 and the relative position relative to the light receiving element 9 and the lens 8 do not occur. Each optical connection is maintained.

  When the fiber stub 2 is press-fitted into the holder 3, the holder-side end surface 2 a of the fiber stub 2 should not exceed the rear end surface of the holder 3 in order to maintain the holding strength of the holder 3.

  This will be described with reference to FIG.

  When the fiber stub 2 is press-fitted into the holder 3, if the holder-side end surface 2a of the fiber stub 2 is pressed into the rear end surface of the holder 3 while leaving only the dimension A, an unexpanded portion is formed in the holder 3. Since it is smaller than the outer diameter of the fiber stub 2, it becomes a stopper 10.

  The load applied to the fiber stub 2 is a load from the plug ferrule side. However, since the stopper 10 is formed, the light emission of the fiber stub 2 and the shift of the relative position with respect to the light receiving element 9 and the lens 8 do not occur. The optical connection is maintained.

  The light that enters and exits the holder-side end surface 7a of the optical fiber 7 propagates in the air while expanding the beam diameter.

  In the case of a general single mode fiber, the divergence angle NA is 0.12.

  According to the first embodiment of the present invention shown in FIG. 1, the holder-side end surface 7 a of the optical fiber 7 is disposed so as to be depressed by D with respect to the holder-side end surface 2 a of the fiber stub 2. When the amount D exceeds a certain value, the light entering and exiting the holder-side end surface 7a of the optical fiber 7 is vignetted on the inner wall of the small-diameter hole 6a of the ferrule 6.

  Here, in the second embodiment of the present invention shown in FIG. 4, the tapered recess 11 is formed in the rear end portion of the ferrule 6 in advance, and the holder side end surface 7a of the optical fiber 7 is formed at the bottom of the tapered recess. The light entering and exiting the optical fiber 7 is prevented from being vignetted on the inner wall of the small-diameter hole 6a of the ferrule 6 by being recessed and fixed by D from the end surface on the side of the fiber stub holder.

  If the inclination angle θ of the tapered recess 11 is equal to or greater than the NA of the light entering and exiting the optical fiber 7, the holder-side end surface 7 a of the optical fiber 7 can be disposed at the bottom portion of the tapered recess 11. The outer periphery of the optical fiber 7 can be reinforced with the ferrule 6.

  As a result, the risk of breakage due to breakage or disconnection of the optical fiber 7 is reduced, and the reliability of the entire optical receptacle 1 is improved.

  If the tapered concave portion 11 shown in FIG. 4 is filled with a light-transmitting adhesive, it is possible to prevent foreign matter from adhering to the holder-side end surface 7a of the optical fiber 7, and to further improve the reliability of the optical receptacle 1. It is possible to improve.

  However, in this case, the holder-side end surface 7a of the optical fiber 7 corresponds to being disposed closer to the holder-side end surface 2a of the fiber stub 2 than the actually disposed position.

  This is shown in FIG.

  Now, assuming that the tapered concave portion 11 is filled with a light-transmitting adhesive having a refractive index n, light entering and exiting the holder-side end surface 7a of the optical fiber 7 disposed at the position indicated by the solid line A is tapered. It is assumed that the inside of the recess 11 propagates with NA = R ′ indicated by a solid line B.

Here, R ′ is expressed by Equation 1 from an equation for obtaining the divergence angle of the 0th-order Gaussian beam.

  In Equation 1, λ is the wavelength of light entering and exiting the optical fiber, ωo is the mode field diameter of the optical fiber, and the beam waist diameter of the Gaussian beam.

  On the other hand, light that enters and exits the holder-side end surface 2a of the fiber stub 2 propagates at NA = R indicated by the alternate long and short dash line C.

The divergence angle of R is expressed by Equation 2 as in Equation 1.

Equations 3 and 2 are derived, and the refractive index n of the light-transmitting adhesive is greater than 1. Therefore, NA = R ′ of light propagating through the tapered recess 11 is NA of light propagating in the air. Therefore, the value is smaller than R.

  When the tapered concave portion 11 is not filled with a light-transmitting adhesive, in order to obtain the light emission pattern indicated by the alternate long and short dash line C, the optical fiber 7 must be disposed at the position indicated by the dotted line D. The optical fiber 7 corresponds to being arranged closer to the holder-side end surface 2 a of the fiber stub 2.

  Next, a third embodiment of the present invention will be described with reference to FIG.

  Here, the holder-side end surface 2a of the fiber stub 2 has a groove shape 14 processed in advance before being press-fitted and fixed to the holder 3. By this processing, the holder-side end surface 7a of the optical fiber 7 becomes the holder side of the fiber stub 2. The configuration is such that only D is depressed with respect to the end face 2a.

  If the holder-side end surface 7a of the optical fiber 7 is cut into an inclined surface of about 4 to 10 ° by groove processing, even if the optical signal is reflected by the holder-side end surface 7a of the optical fiber 7, it does not return to the light source side. .

  In addition, the groove shape 14 of the holder side end surface 2a of the fiber stub 2 can be easily obtained by cutting by dicing.

  As shown in FIG. 7, the fiber stubs 2 in which the optical fibers 7 are inserted into the small-diameter holes of the ferrule 6 are tilted with respect to the reference plane 12 and aligned and fixed. Thereafter, the groove shape 14 is collectively processed by the disc-shaped dicing blade 13.

  Note that the end surface of the optical fiber 7 cut along with the groove shape processing of the fiber stub 2 has a finish that is rougher than the processed surface by polishing.

  This is because the particle size of the diamond blade 13 used for cutting is larger than the particle size of the diamond film used for polishing, and reducing this increases the frictional resistance between the diamond blade 13 and the fiber stub 2, There is a risk that wear of the diamond blade 13 is accelerated and the diamond blade 13 is chipped.

  However, if the dicing blade 13 having a particle size of # 280 or more is used, the end surface 7a on the holder side of the optical fiber 7 is almost in a mirror state, and the coupling efficiency to the optical fiber 7 is reduced due to irregular reflection of light and unstable behavior. Does not occur.

  Moreover, the reflection of the optical signal from the holder-side end surface 7a of the optical fiber 7 can also be prevented by filling the groove shape 14 with a light-transmitting adhesive whose refractive index is matched with the core portion of the optical fiber 7. Can do.

  In this case, however, the rear end portion of the filled light-transmitting adhesive must be mirror-polished to an inclined surface of about 4 to 10 °.

  Next, a fourth embodiment of the present invention will be described with reference to FIG.

  Here, an optical element is bonded and fixed to the holder-side end surface 2a of the fiber stub 2 with an optical adhesive.

  Examples of the optical element include a dielectric mirror having a dielectric multilayer film on a glass plate, a wave plate made of a birefringent crystal, an optical isolator element 18 comprising a Faraday rotator 17 and at least one polarizer 15, 16, etc. It is.

  In FIG. 8, a flat Faraday rotator 17 is disposed between two polarizers 15 and 16 as an optical element, and an optical isolator element 18 in which each is bonded with a light-transmitting adhesive is used.

  This is fixed to the holder-side end surface 2a of the fiber stub 2 with a light-transmitting adhesive, and a ring-shaped permanent magnet 19 is disposed on the outer periphery of the optical isolator element 18.

  Here, the Faraday rotator 17 is, for example, a bismuth-substituted garnet, and is set to have a thickness that rotates the polarization plane of light having a predetermined wavelength at the saturation magnetic field strength by 45 °.

  However, if a self-biased Faraday rotator 17 is used as the Faraday rotator 17, it is not necessary to apply a magnetic field by the ring-shaped permanent magnet 19.

  The two polarizers 15 and 16 are absorption polarizers or birefringent crystals. When an absorption type polarizer is used, the transmission direction of the two polarizers 15 and 16 is adjusted so as to be shifted in the 45 ° rotation direction.

  The optical isolator element 18 is manufactured by a process of performing optical adjustment with a large optical element, and then cutting out a large number of elements to a desired size.

  The Faraday rotator 17 constituting the optical isolator element 18 needs to be applied with a magnetic field greater than the saturation magnetic field strength.

  Here, the magnetic field intensity on the central axis of the ring-shaped permanent magnet 19 is shown in FIG.

  The magnetic field strength distribution shown in FIG. 9 is the magnetic field strength of a ring-shaped permanent magnet made of samarium cobalt having an outer diameter of 2.3 mm, an inner diameter of 1.5 mm, and a thickness of 1.5 mm.

As shown here, the magnetic field strength becomes maximum at the central portion of the ring-shaped permanent magnet 19, and approximately 1.8 × 10 ⁻¹ T is obtained. On the end face, it becomes 0.55 × 10 ⁻¹ T.

Further, outside the magnet, the magnetic field strength is −0.57 × 10 ⁻¹ T, and the direction of the magnetic field is also reversed.

Since the saturation magnetic field strength of the Faraday rotator 17 used for the optical isolator element 18 is generally 0.6 × 10 ⁻¹ T or more, it is necessary to dispose it at least inside the ring-shaped permanent magnet 19. .

  Here, assuming that the holder-side end surface 2a of the fiber stub 2 is polished obliquely as shown in FIG. 8, in order to arrange the Faraday rotator 17 inside the ring-shaped permanent magnet 19, a fiber is used. It is necessary to bring the holder side end surface 2a of the stub 2 closer to the rear end surface side of the holder 3, and the total length of the fiber stub 2 is inevitably increased.

  However, in the optical receptacle 1 according to the present invention, the holder-side end surface 7a of the optical fiber 7 is disposed so as to be recessed by D with respect to the holder-side end surface 2a of the fiber stub 2, so that the entire fiber stub 2 is on the lens 8 side. As a result, the overall dimensions of the optical module are further shortened.

  In FIG. 8, the groove shape 14 is formed in accordance with the method shown in FIG. 6 as a method for causing the holder-side end surface 7 a of the optical fiber 7 to be recessed from the holder-side end surface 2 a of the fiber stub 2.

  A first embodiment of the present invention will be described with reference to FIG.

  The fiber stub 2 is made of a ferrule made of zirconia having a total length of 2.3 mm, and a tapered recess 11 having a depth of 0.5 mm is formed at the rear end.

  In addition, the taper-shaped concave portion 11 was processed with a processing angle θ of 15 °.

  Here, an optical fiber 7 provided with an inclined surface of 4 ° using an angled fiber cleaver manufactured by NETTTTEST is inserted from the tapered recess 11 side, and the holder-side end surface 7a of the optical fiber 7 is used as a holder for the fiber stub 2. It fixed using the light-transmitting adhesive so that it might leave | separate 0.48 mm from the side end surface 2a.

  Thereafter, the tip surface of the fiber stub 2 is processed into a curved surface with a curvature radius of 16 ± 9 mm.

  In addition, Epo-Tek353ND by Epoxy Technology was used as the light transmissive adhesive, and Corning single mode fiber SMF28 was used as the optical fiber 7.

  The tapered recess 11 provided at the rear end of the fiber stub 2 is also filled with a light-transmitting adhesive, and the holder-side end surface 2a of the fiber stub 2 is mirror-polished to a 4 ° inclined surface. .

  If the inclination direction of the holder-side end surface 7 a of the optical fiber 7 and the inclination direction of the holder-side end surface 2 a of the fiber stub 2 are set in opposite directions, the light enters and exits the fiber stub 2 with respect to the central axis of the fiber stub 2. The optical axis of the optical signal to be transmitted can be made closer to parallel, and the positions of the lens, light emitting element, and light receiving element in the optical module can be arranged on a straight line.

  Therefore, the entire optical module can be further downsized.

  Since the tapered concave portion 11 is filled with a light-transmitting adhesive having a refractive index of 1.56, the holder-side end surface 7a of the optical fiber 7 is arranged closer to the holder-side end surface 2a of the fiber stub 2. It corresponds to that.

  For the configuration in which the holder-side end surface 7a of the optical fiber 7 is disposed at a distance of 0.48 mm from the holder-side end surface 2a of the fiber stub 2, as in this embodiment, the holder-side end surface 2a of the fiber stub 2 is This corresponds to the holder side end surface 7a of the optical fiber 7 being disposed at a position of 0.31 mm.

  Therefore, it is possible to obtain a configuration in which the actual optical fiber length is 1.99 mm while using the fiber stub 2 made of the ferrule 6 having a total length of 2.3 mm.

  Therefore, according to the first embodiment, it is possible to obtain the optical receptacle 1 whose overall length is shortened by 0.31 mm compared to the conventional optical receptacle 1.

  This time, the insertion loss characteristics and reflection characteristics of the optical receptacle according to the first embodiment and the conventional optical receptacle, each of five, were evaluated.

  The insertion loss was measured by using the respective optical receptacles, manufacturing the receptacle type optical module 21 shown in FIG. 11, and connecting the plug ferrule 20.

  The reflection characteristics were measured using a JDS return loss meter with measurement light incident from the plug ferrule 20 side.

The results are shown in Table 1.

  As a result, the optical receptacle according to the present invention showed an optical loss of 0.015 dB in terms of insertion loss and 1.18 dB in terms of reflection characteristics compared to the conventional optical receptacle, but the optical characteristics of the optical receptacle were good as absolute values. The characteristics can be obtained.

  Next, a second embodiment of the present invention will be described with reference to FIG.

  The fiber stub 2 is composed of a ferrule 6 made of zirconia having a total length of 2.3 mm, and an optical fiber 7 is inserted and fixed.

  Here, the front end surface of the fiber stub 2 is processed into a curved surface with a curvature radius of 17 ± 5 mm, and a groove shape 14 is formed at the rear end portion by dicing.

  Note that the groove shape 14 by dicing is processed so that the bottom portion is inclined at 8 °, whereby the holder-side end surface 7a of the optical fiber 7 is also formed with an inclined surface of 8 °.

  Further, the processing is performed so that the holder-side end surface 7 a of the optical fiber 7 is depressed by 0.5 mm with respect to the holder-side end surface 2 a of the fiber stub 2.

  For dicing, a blade having a thickness of 0.3 mm and a particle size of # 400 was used, and processing was performed at a blade rotation speed of 10000 rpm and a cutting speed of 0.2 mm / sec.

  As a result, a mirror surface state is formed on the end surface 7 a on the holder side of the optical fiber 7.

  Therefore, it is possible to obtain a configuration in which the actual optical fiber length is 1.8 mm while using the fiber stub 2 made of the ferrule 6 having a total length of 2.3 mm.

  Therefore, according to the second embodiment, it is possible to obtain the optical receptacle 1 whose overall length is shortened by 0.5 mm compared to the conventional optical receptacle 1.

  This time, the insertion loss characteristics and reflection characteristics of the five optical receptacles according to the second embodiment were evaluated.

  In addition, the evaluation method of each optical characteristic used the method similar to the time of the optical receptacle measurement by the above-mentioned 1st Example.

The results are shown in Table 2.

  As a result, the optical receptacle according to the present invention can be confirmed to improve the reflection characteristic by 3.96 dB without any problem in actual use, although the deterioration of the insertion loss is 0.04 dB compared to the conventional optical receptacle. As the absolute value of the characteristic, good optical characteristics can be obtained.

  The deterioration of the insertion loss is considered to be due to the fact that the smoothness of the surface is slightly deteriorated by cutting the rear end face 7a of the optical fiber 7 by dicing.

  Further, a third embodiment of the present invention will be described with reference to FIG.

  The fiber stub 2 is composed of a ferrule 6 made of zirconia having a total length of 2.3 mm, and an optical fiber 7 made of quartz glass is inserted and fixed.

  Here, the front end surface of the fiber stub 2 is processed into a curved surface with a curvature radius of 17 ± 5 mm, and the holder side end surface 2a is polished so that the inclination becomes 8 °.

  Further, the holder-side end surface 2a of the fiber stub 2 is similar to the optical receptacle 1 shown in the second embodiment of the present invention in that the holder-side end surface 7a of the optical fiber 7 is spaced from the holder-side end surface 2a of the fiber stub 2. A groove shape 14 is formed by dicing so as to be depressed by 5 mm.

  An optical isolator element 18 is bonded and fixed to the holder-side end surface 2 a of the fiber stub 2.

  The optical isolator element 18 is obtained by arranging a flat Faraday rotator 17 between two absorption polarizers 15 and 16 and bonding them with a light-transmitting adhesive.

  Further, a ring-shaped permanent magnet 19 is bonded to the outer periphery of the optical isolator element 18.

  Thus, according to the third embodiment, a fiber stub 2 comprising a ferrule 6 having a total length of 2.3 mm is used while an optical element such as an optical isolator element 18 is provided at the rear end of the fiber stub 2. However, a configuration in which the substantial optical fiber length is 1.8 mm can be obtained.

  Therefore, according to the third embodiment, it is possible to obtain an optical receptacle with an optical element whose overall length is shortened by 0.5 mm compared to a conventional optical receptacle.

  This time, the insertion loss characteristics and the isolation characteristics of the optical receptacle with the optical isolator element according to the third embodiment and the conventional optical receptacle with the optical isolator element were evaluated.

  The insertion loss characteristic was evaluated using the same method as used in the optical receptacle measurement according to the first embodiment.

  For the isolation characteristics, the plug ferrule 20 is connected to a single optical receptacle with an optical isolator element, measurement light is incident from the plug ferrule 20 side, and the intensity of transmitted light is measured using an optical multimeter manufactured by Agilent Technologies. Measured and calculated.

The results are shown in Table 3.

  As a result, the optical receptacle with an element for an optical isolator according to the present invention has a characteristic deterioration of 0.17 dB in terms of insertion loss with respect to the conventional optical receptacle.

  This is an increase in loss caused by light reflected at the holder-side end surface 7a of the optical fiber 7, but there is no problem in practical use.

  Note that the reflected light generated on the holder-side end surface 7a of the optical fiber 7 is blocked by the isolator element 18 and therefore does not return to the light source side.

  Further, if an antireflection film or the like is applied to this portion, an increase in loss can be easily reduced.

  The loss increase can also be reduced by filling the groove shape 14 with a light-transmitting adhesive whose refractive index is matched to the refractive index of the core of the optical fiber 7.

  As for the isolation characteristics, the optical receptacle with an optical isolator element according to the present invention can provide sufficient isolation characteristics as in the conventional optical receptacle with an optical isolator element.

(A) is side surface sectional drawing which shows 1st embodiment of the optical receptacle of this invention, (b) is a front view of the figure. (A) is side surface sectional drawing which showed the structure of the optical module using the optical receptacle of this invention, (b) is side sectional drawing which showed the structure of the optical module using the conventional optical receptacle. (A) is side surface sectional drawing which shows 1st embodiment of the optical receptacle of this invention, (b) is an enlarged view of the holder side end surface part in 1st embodiment of the optical receptacle of this invention. . (A) is side surface sectional drawing which shows 2nd embodiment of the optical receptacle of this invention, (b) is a front view of the figure. (A) is side surface sectional drawing of the fiber stub part in 2nd embodiment of the optical receptacle of this invention, (b) is an enlarged view of the holder side end surface part in 2nd embodiment of the optical receptacle of this invention. FIG. (A) is side surface sectional drawing which shows 3rd embodiment of the optical receptacle of this invention, (b) is a front view of the figure. It is a perspective view which shows the manufacturing method of the optical receptacle by 3rd embodiment of this invention. (A) is side surface sectional drawing which shows 1st Embodiment of the optical receptacle with an optical element of this invention, (b) is the front view of the figure. (A) is a perspective view which shows the magnetic field strength examination part in a ring-shaped permanent magnet, (b) is a graph which shows the magnetic field strength on the central axis in a ring-shaped permanent magnet. (A) is side surface sectional drawing which shows the conventional optical receptacle, (b) is a front view of the figure. It is side surface sectional drawing which showed the structure of the optical module using the conventional optical receptacle. (A) is side surface sectional drawing which shows the conventional optical receptacle with an optical element, (b) is a front view of the figure.

Explanation of symbols

1: optical receptacle 2: fiber stub 2a: fiber stub holder side end surface 3: holder 4: sleeve 5: sleeve case 6: ferrule 6a: narrow hole 7: optical fiber 7a: optical fiber holder side end surface 8: lens 9 : Light emitting and light receiving element 10: Stopper 11: Tapered recess 12: Reference surface 13: Dicing blade 14: Groove shape 15, 16: Polarizer 17: Faraday rotator 18: Optical isolator element 19: Ring-shaped permanent magnet 20: Plug ferrule 21: receptacle type optical module 22: case 23, 24: spacer

Claims (6)

A fiber stub having at least one small-diameter hole, an optical fiber held in the small-diameter hole, a holder for holding one end of the fiber stub by press-fitting, and a plug ferrule that contacts the optical fiber are held. And a holder side end surface of the optical fiber held in the fiber stub is recessed with respect to the holder side end of the fiber stub. Optical receptacle. 2. The optical receptacle according to claim 1, wherein a holder-side end surface of the optical fiber held in the fiber stub is recessed by 10 μm or more with respect to a holder-side end surface of the fiber stub. The optical receptacle according to claim 1, wherein a tapered concave portion is provided on an end surface on the holder side of the fiber stub. The optical receptacle according to claim 1, wherein a groove is formed on an end surface of the fiber stub on the holder side. The optical receptacle according to claim 1, wherein an optical element is bonded and fixed to an end surface on the holder side of the fiber stub. 6. The optical receptacle according to claim 5, wherein an optical isolator element comprising at least one Faraday rotator and at least one polarizer is bonded and fixed to an end surface of the fiber stub on the holder side.

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