JP2002156554A - Optical fiber pigtail having optical part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve attaching precision for an optical part and to realize cost reduction, in an optical fiber having an optical fiber holder with at least one thin diameter hole, the optical fiber held within the thin diameter hole and at least one optical part which is fixed to the optical fiber holder and the end surface of the optical fiber by the use of a light transmission adhesive. SOLUTION: The optical fiber holder and the end surface of the optical fiber are formed by machining, moreover a projecting part is formed in the optical fiber holder so as to be adjacent to the fiber end, and the optical part is fixed so that the side surface of the optical part is brought into contact with the side surface of the projecting part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber pigtail with various optical components used for optical communication, optical information processing, optical sensors and the like.

[0002]

2. Description of the Related Art In order to explain the present invention, an optical fiber pigtail with an optical isolator will be described as an example.

An optical isolator is a device used in combination with a laser module used as a light source for optical communication, optical information processing, and the like, and has a function of transmitting light in the forward direction and blocking light in the reverse direction. The light emitted from the laser light source is reflected and scattered when passing through various optical elements and optical fibers. However, when such light returns to the laser side, the output of the light source becomes unstable and noise is generated in the signal. An optical isolator is used to block this return light. Such an optical isolator is one of the key devices for optical fiber communication, and with the development of information communication in recent years, low cost and high productivity have been strongly desired.

FIG. 9 shows an example of the optical isolator.
Here, an optical isolator element 4 is used in which a flat Faraday rotator 3 is disposed between two polarizers 1 and 2 as optical components, and each is bonded with a light transmitting adhesive.
This is fixed to the tip of the optical fiber 7 held in the small-diameter hole of the optical fiber holder 6 fixed in the metal fitting 5 by using a light transmitting adhesive, and the ring-shaped permanent magnet 8 is further fixed to the optical isolator element. 4 is arranged on the outer periphery.

[0005] The optical fiber holder 6 and the end face 9 of the optical fiber 7 held in the small-diameter hole are processed into a flat polished surface by polishing. In order to suppress the reflected light on the end face 9 from returning to the laser side, the normal direction of the end face 9 is processed so as to be inclined with respect to the incident optical axis.

The two polarizers 1 and 2 in the optical isolator element 4 are adjusted such that the transmission directions of the two polarizers 1 and 2 are shifted by 45 °, and the Faraday rotator 3 is used to polarize light having a predetermined wavelength at the saturation magnetic field intensity. It has a thickness that rotates the surface by 45 °. The optical isolator element 4 is manufactured by a process of performing optical adjustment with a large-sized optical element and then cutting out a large number of pieces into a desired size.

Here, in order to couple outgoing light from the laser to the optical fiber 7 efficiently, the optical isolator element 4 is made rectangular and its long side is parallel to the inclination direction of the end face 9. This is shown in FIG. In FIG. 10, since the light beam from the laser enters from the direction of the arrow 10, it passes obliquely through the optical isolator element 4. Therefore, the optical isolator element 4 needs to have a larger size in a direction parallel to the inclination direction of the end face 9.

Further, the light emitted from the laser is transmitted to an optical fiber 7.
In order to couple light efficiently, the transmission polarization direction of the incident-side polarizer of the optical isolator element 4 is configured to be parallel to the tilt direction. In general, the transmittance and reflectance of light passing between two media change according to the polarization direction. Here, according to Fresnel's equation, the transmittance is a P-wave parallel to the tilt direction of the medium boundary surface. Becomes maximum and becomes minimum in the S wave perpendicular to the inclination direction. Accordingly, the configuration is such that the light incident on the optical isolator element 4 is a P-wave, that is, the transmission polarization direction of the incident-side polarizer is parallel to the tilt direction.

Although the optical fiber pigtail with an optical isolator has been described here, the present invention can be similarly applied to an optical fiber pigtail with a Faraday rotating mirror.

[0010]

However, the above-mentioned optical fiber pigtail with optical components shown in FIG. 9 has the following problems.

End face 9 to which optical isolator element 4 is fixed
Is generally formed by polishing in order to prevent irregular reflection when the light emitted from the laser enters the optical fiber 7. In the polishing process, a diamond film in which diamond abrasive grains are dispersed and fixed by a binder is fixed on a surface plate, and the tip of the optical fiber holder 6 is pressed against the plate under a constant pressure to perform polishing. In addition, diamond films are available for rough finishing, medium finishing, and final finishing, and have different abrasive grain sizes. These are sequentially replaced, and the polished surface is smoothed. Although this operation is performed using a polishing machine, the number of batch processes that can be performed at one time is as small as about ten and several pieces.

Further, the diamond film deteriorates as the processing is continued, so that the polishing amount per time is not constant. Therefore, since it is necessary to perform polishing while visually confirming the shape of the tip of the optical fiber holder 6 and the surface roughness of the end face 9, this processing requires a large amount of work time, which hinders cost reduction. It was a big factor.

Further, the optical isolator element 4 is manufactured by a process of performing optical adjustment with a large-sized optical element and then cutting out a large number of pieces into a desired size. The number of the optical isolator elements 4 to be cut out is inevitably larger and smaller, and accordingly, the bonding area for fixing the optical isolator elements 4 to the end face 9 is reduced.

Due to this influence, the allowable range of the positional deviation of the optical isolator element 4 with respect to the optical fiber 7 is reduced, and the mounting position accuracy of the optical isolator element 4 is required to be improved, but the optical isolator element 4 is fixed on the end face 9. At this time, since the position of the optical isolator element 4 is shifted due to a decrease in viscosity during curing and heating of the light transmitting adhesive and an influence of surface tension, it is difficult to accurately fix the optical fiber 7 to the end of the optical fiber 7. It is. In addition, since the inclination direction of the end face 9 is determined based on the shape or the marking made before polishing, it is difficult to accurately match the inclination direction with the direction of the optical isolator element 4.

Furthermore, since the size of the optical isolator element 4 is reduced, the area of the bonding portion between the end face 9 and the optical isolator element 4 and the bonding area between the optical elements constituting the optical isolator element 4 are reduced. Also decrease.

[0016]

SUMMARY OF THE INVENTION The present invention has been made in view of these problems, and has an optical fiber holder having at least one small diameter hole, and an optical fiber held in the small diameter hole. And at least one optical component fixed to the end face of the optical fiber holder using a light transmissive adhesive, wherein a protrusion is formed on the end face of the optical fiber holder, and the protrusion is formed. The optical component is fixed by bringing the side surface of the optical component into contact with the side surface.

Further, the projecting portion of the optical fiber holder is formed by cutting.

Further, a side surface of the projecting portion formed on the optical fiber holder is formed in a direction perpendicular or parallel to an inclined direction of an end face of the optical fiber holder.

Further, the optical component is an optical isolator in which at least one polarizer and at least one Faraday rotator are stacked.

Further, the optical fiber holder is made of light transmissive glass.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to FIG. 1 by taking an example of an optical fiber pigtail with an optical isolator according to the description of the prior art.

Again, two polarizers 1 are used as optical components.
An optical isolator element 14 is used in which a flat Faraday rotator 13 is disposed between the first and second 12 and 12 and each is bonded with a light transmitting adhesive. This is fixed to the tip of an optical fiber 17 held in a small-diameter hole of an optical fiber holder 16 fixed in a metal fitting 15 using a light-transmitting adhesive, and a ring-shaped permanent magnet 18 is further fixed to an optical isolator element. 14 are arranged on the outer periphery.

The tip of the optical fiber holder 16 has a slope 19
And the projection 20 are formed by cutting, but the inclined surface 19 is formed so that the normal direction is inclined with respect to the incident optical axis in order to suppress the reflected light from returning to the laser side. . The optical isolator element 14 is fixed so that its side surface is in contact with the side surface of the protrusion 20.

Here, the Faraday rotator 13 is, for example, a bismuth-substituted garnet, and is set to have a thickness for rotating the polarization plane of light having a predetermined wavelength at a saturated magnetic field intensity by 45 °. However, if a self-biased Faraday rotator is used as the Faraday rotator 13, it is not necessary to apply a magnetic field by the magnet 18.

The two polarizers 11 and 12 are absorption polarizers or birefringent crystals. When an absorption polarizer is used, the transmission direction of the two polarizers 11 and 12 is adjusted so as to be shifted in the 45 ° rotation direction. Also,
As shown in the prior art, the optical isolator element 14 is cut into a rectangle so that the emitted light from the laser is efficiently coupled to the optical fiber 17, and the long side thereof is configured to be parallel to the inclination direction of the inclined surface 19. . Further, the transmission polarization direction of the incident side polarizer 11 of the optical isolator element 14 is configured to be parallel to the tilt direction.

The optical isolator element 14 is manufactured by a process of performing optical adjustment using a large-sized optical element and then cutting out a large number of pieces into a desired size. Here, if an optical isolator is to be constructed at a lower cost, the number of the optical isolator elements 14 to be cut out is inevitably larger and smaller, but according to the present invention, the optical isolator elements 14 are cut out.
The projection 20 provided on the side of the optical fiber holder 16
To contact the side of the optical fiber,
The parallelism of the side surface of the protruding portion 20 with respect to the inclination direction of the inclined surface 19 can also be processed with high accuracy. Accordingly, both the position of the optical isolator element 14 with respect to the optical fiber position and the direction of the optical isolator element with respect to the inclination direction of the inclined surface 19 Fixing can be performed accurately.

Further, since the contact area between the optical fiber holder 16 and the optical isolator element 14 is increased, the viscosity of the light-transmitting adhesive during curing and heating is not easily reduced, and the position shift due to the influence of surface tension or the like is less likely to occur.

Further, since the contact portion between the side surface of the optical isolator element 14 and the side surface of the protrusion 20 is fixed, the optical isolator element 14 is firmly fixed on the optical fiber holder 16. Further, since each optical element constituting the optical isolator element 14 is bonded to the optical fiber holder 16, the strength of the optical isolator element 14 itself also increases. This means that the optical isolator element 14 can be set smaller, and that the price can be reduced.

Further, in FIG.
Is made of ceramic such as zirconia or alumina or glass, and can be easily cut by dicing or the like. In particular, when glass is selected as the material, the material is the same as that of the optical fiber 17 held in the small-diameter hole, and the selection of the cutting conditions is facilitated. Further, when a light transmissive glass is selected, the position of the optical fiber 17 can be easily confirmed from the appearance, so that the alignment in the direction parallel to the side surface of the protruding portion 20 of the optical isolator element 14 can be performed accurately. .

The surface of the inclined surface 19 is rougher than the surface processed by polishing. This is because the particle size of the diamond blade used for cutting is larger than the particle size of the diamond film used for polishing, and when the diameter is reduced, the frictional resistance between the diamond blade and the workpiece increases, and the diamond blade Wear is faster and there is a risk of chipping of the blade.

As described above, the inclined surface 19 is a rough surface.
In the optical fiber pigtail with an optical component according to the present invention, a light transmitting adhesive for fixing the optical component is applied to the end face of the optical fiber 17, and the refractive index of the optical fiber 17 is determined.
If the refractive index is matched with the refractive index of the core portion, no reflection occurs at the boundary between the light-transmitting adhesive and the end face of the optical fiber 17, so that irregular reflection of light and a decrease in coupling efficiency to the optical fiber due to unstable behavior do not occur. .

In the shape shown in FIG. 1, the side surface of the projecting portion 20 at the tip of the optical fiber holder is formed so as to be parallel to the inclination direction of the inclined surface 19, but in addition to FIGS. Can be formed as shown in FIG. In the shape shown in FIG. 2, the side surface of the projecting portion 20 is formed to be perpendicular to the inclination direction of the inclined surface 19. In the shape shown in FIG. 3, projecting portions 20 are formed on both sides of the optical isolator element 14. In the shape shown in FIG. 7, the side surface of the projecting portion 20 is formed so as to be parallel to the inclination direction of the inclined surface 19, and a relief portion 24 is further formed.

FIGS. 4 to 6 show a method of forming each shape by cutting. The shape shown in FIG.
The cutting blade 2 which rotates the optical fiber holder 16 as shown in FIG.
The optical fiber holder 16 can be formed by arranging it at an angle with respect to the direction of the rotation shaft 22 and cutting a part of the tip of the optical fiber holder 16. The shape shown in FIG. 2 can be formed by arranging the optical fiber holder 16 at an angle with respect to the fixed base 23 as shown in FIG. Further, the shape shown in FIG. 3 can be formed by arranging the optical fiber holder 16 on the fixed base 23 as shown in FIG. Further, the shape shown in FIG. 7 is formed by the same processing as the method shown in FIG. 4, but the first cutting part 25 and the second cutting part 26 shown in FIG. Formed.

Although only three optical fiber holders 16 are arranged in FIGS. 4 to 6, in actual processing, several tens of optical fiber holders are arranged in parallel to collectively form the tip shape. Can be formed. Therefore, the tip of the optical fiber holder can be formed at a lower cost as compared with polishing.

The optical fiber holder shown in FIG.
At the time of cutting, the optical fiber holder 16 can be arranged in parallel to the fixed base 23, and cutting can be easily performed. Further, the optical fiber holder 16 shown in FIG.
Can accurately arrange the optical isolator element 14 in its long side direction, that is, the direction in which the incident light beam obliquely passes through the inside of the optical isolator element 14, so that the incident light ray The risk of being interrupted is reduced. Further, the optical fiber holder 16 shown in FIG.
Since the bonding area between the optical isolator element 14 and the optical fiber holder 16 increases, more secure fixing is possible. In the fiber holder 16 shown in FIG. 7, the optical isolator element can be fixed in close contact with the end face 19 and the side face of the protruding portion 20, so that the positional accuracy is improved and the optical characteristics are stabilized. When the optical fiber holder is processed into the shape shown in FIGS. 1, 2 and 7, the inclined surface is processed by the side surface of the cutting blade as compared with the case where the optical fiber holder is processed into the shape shown in FIG. A smoother processed surface can be obtained.

In the above embodiment, a fiber pigtail with an optical isolator has been described. However, the present invention can be applied to an optical fiber pigtail having optical components such as a Faraday rotator instead of the optical isolator.

[0037]

EXAMPLE An optical fiber pigtail with an optical isolator shown in FIG. 7 was manufactured as an example of the present invention. Hereinafter, the details will be described with reference to FIG.

In the figure, reference numeral 15 denotes a metal fitting, in which an optical fiber holder 16 made of light transmissive glass is fixed using epoxy resin. The optical fiber 17 is held in the small-diameter hole of the optical fiber holder 16 using epoxy resin. An inclined surface 19 and a protruding portion 20 are formed at the tip of the optical fiber holder 16 by cutting. In particular, the inclined surface 19 is formed to have an inclination of 8 ° with respect to the optical fiber 17. In processing the protrusion 20, a relief 24 is provided so that the side surface of the optical isolator element 14 sufficiently contacts the side surface of the protrusion 20. Further, the optical isolator element 14 is fixed to the tip of the optical fiber 17 on the inclined surface 19 with a light transmitting adhesive, and a ring-shaped permanent magnet 18 made of Sm-Co is formed around the optical isolator element 14 with epoxy resin. Fix it.

The projection of the optical fiber holder is formed by dicing twice to form the escape portion 24. This is shown in FIG. The first cutting portion 25 has a diamond blade particle size of # 800, a blade thickness of 0.2 mm, and a rotation speed of 1500.
The second cutting portion 26 was formed by cutting at 0 rpm and a cutting speed of 0.5 mm / sec.
pm and a cutting speed of 1 mm / sec.

The refractive index of the light-transmitting adhesive applied to the tip of the optical fiber is 1.556, which is set near the refractive index of the optical fiber core of 1.470. The reflectance is 0.09%, which is sufficiently small. Therefore, when receiving the emitted light from the laser, even if the end face of the optical fiber is rough, the incident light does not cause irregular reflection or unstable behavior at the end face of the optical fiber, and the coupling efficiency to the optical fiber may be reduced. Absent.

The optical isolator element 14 includes two polarizers 1
The Faraday rotator 13 is arranged between the first and second 12 and bonded to each other with a light-transmitting adhesive. The thickness of the polarizer is 0.2 mm, the thickness of the Faraday rotator is about 0.3 mm, and the thickness of the entire optical isolator element 14 is 0.7 mm.
Becomes Although the element size is made as small as possible, it is premised that the incident light from the laser is not blocked.
5 mm x 0.3 mm short side.

At the time of fixing, the side surface of the optical isolator element is brought into contact with the side surface of the protruding portion 20, and this is used as a guide. In addition,
In the alignment in the direction parallel to the side surface of the protruding portion of the optical isolator element 14, the alignment is performed based on the position of the optical fiber viewed from the inclined surface 19.

Here, the coupling efficiency of the optical fiber pigtail with an optical isolator manufactured according to the above configuration with the laser output light was compared with the conventional optical fiber pigtail with an optical isolator shown in FIG. Table 1 shows the results.

[0044]

[Table 1]

Table 1 shows the measurement results of five materials,
The variation range is shown. As a result, in the conventional example, the position shift occurs when the optical isolator element is fixed, so that the incident light from the laser is blocked by the side surface of the optical isolator element and the coupling efficiency varies. Is accurately fixed to the end of the optical fiber, so that the coupling efficiency is stable and the range of variation is small.

Further, the production time required for one product according to the embodiment of the present invention was compared with that of a conventional product. Table 2 shows the results. However, here, only the process of processing the tip of the optical fiber holder and the process of fixing the optical isolator element, which are the processes in which the manufacturing time differs, are omitted, and the other processes are omitted. For processes that can be batch processed, the total manufacturing time is divided by the number of products that have been batch processed.

[0047]

[Table 2]

As shown in the results of Table 2, in the embodiment of the present invention, the manufacturing time required for each product is reduced in each step.

The reason why the manufacturing time was reduced in the optical fiber holder tip processing step is that the end face of the optical fiber holder was formed by lump polishing of 12 products in the conventional example. In this case, the cutting was performed by batch cutting of 30 products.

Further, the diamond blade used in the cutting process in the embodiment of the present invention is less likely to be deteriorated as compared with a diamond sheet used for polishing a conventional product. For this reason, since the cutting amount per time is constant, there is no need to check the product visually during the processing.

Further, in the optical isolator element fixing step, the reason for the reduction in the manufacturing time is that in the conventional example, the optical isolator position adjustment direction on the optical fiber holder is two directions, vertical and horizontal. According to the embodiment of the present invention, the direction is parallel to the side surface of the protrusion provided on the optical fiber holder.

Further, in the embodiment of the present invention, the contact area between the optical isolator element and the optical fiber holder is increased as compared with the conventional example. Therefore, the optical isolator is less likely to be displaced due to the influence of the viscosity of the light transmitting adhesive, the surface tension, and the like, and the necessity for the position correction is eliminated.

[0053]

As described above, according to the present invention, an optical fiber holder having at least one small diameter hole, an optical fiber held in the small diameter hole, the optical fiber holder and the optical fiber holder are provided. In an optical fiber having at least one optical component fixed to an end face of the optical fiber using a light-transmitting adhesive, a projection is formed on the optical fiber holder so as to be adjacent to a fiber end, and The following effects are obtained by fixing the optical component so that the side surface is in contact with the side surface of the protrusion.

The optical component can be accurately, firmly and easily fixed to the end face of the optical fiber holder.

Further, if the optical fiber holder and the optical fiber end face are formed by cutting, the processing can be performed easily and collectively, and the cost can be reduced.

Further, by forming the side surface of the projection formed on the optical fiber holder in a direction perpendicular or parallel to the inclination direction of the optical fiber holder and the end face of the optical fiber, the direction of the optical component can be reduced. Can be accurately fixed in the inclination direction of the end face of the optical fiber holder.

Further, by setting the material of the optical fiber holder to light transmissive glass, it becomes easy to determine the cutting conditions of the optical fiber holder, and the optical component is attached to the end face of the optical fiber holder. It can be fixed accurately and easily.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an optical fiber pigtail with an optical component according to the present invention.

FIG. 2 is a perspective view showing another embodiment of the optical fiber pigtail with optical components of the present invention.

FIG. 3 is a perspective view showing another embodiment of the optical fiber pigtail with optical components of the present invention.

FIG. 4 is a perspective view showing a cutting method of the optical fiber pigtail with the optical component shown in FIG. 1;

FIG. 5 is a perspective view showing a cutting method of the optical fiber pigtail with optical components shown in FIG. 2;

FIG. 6 is a perspective view showing a cutting method of the optical fiber pigtail with the optical component shown in FIG. 3;

FIG. 7 is a perspective view showing another embodiment of the optical fiber pigtail with an optical component of the present invention.

8 is a perspective view showing a cut portion of an optical fiber holding section in the optical fiber pigtail with optical components shown in FIG. 7;

FIG. 9 is a perspective view showing a conventional optical fiber pigtail with optical components.

FIG. 10 is a cross-sectional view showing the direction of incidence of a laser beam on an optical fiber.

[Explanation of symbols]

 1, 2, 11, 12: polarizer 3, 13: Faraday rotator 4, 14: optical isolator element 5, 15: metal fitting 6, 16: optical fiber holder 7, 17: optical fiber 8, 18: ring-shaped permanent Magnet 9: Polished surface 10: Light incident direction from laser 19: Inclined surface 20: Projecting portion 21: Cutting blade 22: Rotating shaft of cutting blade 23: Fixed base 24: Escape 25: First cutting portion 26: Second Cutting part of

Claims (5)

[Claims] An optical fiber holder having at least one small-diameter hole, an optical fiber held in the small-diameter hole, and fixed to an end face of the optical fiber holder using a light-transmitting adhesive. And at least one optical component, wherein a projection is formed on an end face of the optical fiber holder,
An optical fiber pigtail with an optical component, wherein the side surface of the optical component is fixed by abutting the side surface of the projection. 2. The optical fiber pigtail with an optical component according to claim 1, wherein the projection of the optical fiber holder is formed by cutting. 3. The optical fiber holder according to claim 1, wherein a side surface of the projecting portion formed on the optical fiber holder is formed in a direction perpendicular or parallel to an inclined direction of an end surface of the optical fiber holder. Fiber pigtail with optical components. 4. An optical fiber pigtail with an optical component according to claim 1, wherein said optical component is an optical isolator in which at least one polarizer and at least one Faraday rotator are laminated. 5. An optical fiber pigtail with an optical component according to claim 1, wherein said optical fiber holder is made of light transmissive glass.