JPH06294911A - Optical fixed attenuator and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture an optical fixed attenuator capable of easily obtaining a target optical attenuation quantity with high precision and reducing the production of defectives as much as possible at low cost. CONSTITUTION:The end surface of one ferrule 3 between a couple of ferrules 3 and 5 is formed into a slanting plane having a 1st tilt angle theta1 to a plane F crossing the optical axis P of an optical fiber 2, and the end surface of the other ferrule 5 is formed into a slanting plane having a 2nd tilt angle theta2 a little larger than the 1st tilt angle. Then the slanting plane of the ferrule 5 is coated with an optical attenuation film 19 to specific thickness, and the slanting planes 3a and 5a of the couple of ferrules are arranged opposite each other while having the optical axes P of optical fibers 2 aligned with each other, thereby constituting the optical fixed attenuator 1. Then the ferrule 3 is rotated in its circumferential direction by a specific angle on the ferrule 5 to adjust the attenuation value to a target value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixed optical attenuator used in an optical communication system, and more particularly to improvement of a fixed optical attenuator used for adjusting the optical input level of a light receiving module.

[0002]

2. Description of the Related Art Generally, a fixed optical attenuator is used for matching the light amount of an optical signal transmitted through an optical fiber cable with the dynamic range of a monitor or a measuring device of an optical transmission line of an optical communication system. In the system, it is indispensable as a pseudo line when the received light intensity exceeds an appropriate level.

As such a conventional fixed optical attenuator,
For example, the ones shown in FIGS. 6 and 7 are known.

A light attenuating element 1a shown in FIG. 6 is an optical attenuating element incorporated in a typical conventional fixed optical attenuator. For example, a metal film or a metal oxide is formed on an end face of a ferrule 3 having an optical fiber 2 at its center. A light attenuating film 4 composed of several kinds of metal mixed films, which are often used as an ND filter, is coated by a vacuum vapor deposition method, a sputtering method, or the like, and the optical axis of the optical fiber 2 is aligned with the light attenuating film 4 via a gap L. The opposing end faces of the ferrules 5 are butted against each other, the adhesive 6 is poured into the space L to bond them, and the two ferrules 3,
The end of 5 is fixed by a split sleeve 7, and the amount of light attenuation corresponding to the film thickness of the light attenuation film 4 is obtained.

On the other hand, the optical attenuator 1b shown in FIG. 7 is disclosed in Japanese Patent Laid-Open No. 62-121405, and the abutting surfaces of the respective ferrules 3 and 5 are aligned with the optical axis of the optical fiber 2. A flat surface inclined with respect to each other is provided, and a polyester film 8 on which a light-attenuating film 9 having a target light-attenuating amount is vapor-deposited is provided between the abutting surfaces so as not to come into contact with any ferrule end surface. Then, as in the case of the light attenuating element 1a of FIG. 6, the adhesive 6 and the sleeve 7 are used for fixing.

[0006]

However, in the conventional light attenuating elements 1a and 1b, a metal film or the like is vapor-deposited as the light attenuating film 4, so that a target accurate light attenuating amount can be obtained. It has the drawback of being very difficult. Because, in the light attenuating element 1a, the light attenuating film 4 having a coating film thickness corresponding to the target light attenuation amount is used.
Even if formed on the end face of the ferrule 3, a loss due to the optical axis deviation at the time of assembling the element, a bending of the optical axis, and a loss with the adhesive 6 are added in addition to the attenuation by the attenuating film 4. Therefore, the loss accuracy will be poor in the end. In this element 1a, the metal film 4 is directly vapor-deposited on the end face of the ferrule 3, so that the number of constituent elements of the element 1a is reduced by the polyester film 8 as compared with the light attenuating element 1b. Therefore, there is an advantage that the assembly work becomes easy,
A film thickness variation due to vapor deposition occurs, and a desired light attenuation amount cannot be obtained, which must be disposed of together with the ferrules 3 and 5 which are highly accurately polished, and the cost is increased accordingly.

Further, in the optical attenuation element 1b of FIG. 7,
When adjusting the optical axis between both ferrules 3 and 5, the metal film 9
Since the vapor-deposited surface of is in contact with the opposite end face of the ferrule 5, the vapor-deposited film is scratched, and even if the desired light attenuation amount is initially obtained, the light attenuation amount is largely changed later and the loss accuracy is reduced. There are drawbacks. In addition, this optical attenuator 1b
Uses a polyester film 8 whose surface is coated with a metal film 9, so that the number of constituent parts is greater than that of the light attenuating element 1a, and the assembling work becomes difficult.
As in the case of the above-described optical attenuator 1a, contact with the metal film 9,
Problems such as scratches occur. Further, since the polymer film is used as the base of the metal film 9, there still remains a problem in heat resistance and stability.

Therefore, which of the optical attenuation elements 1a, 1
There is a problem also in b, and there is a drawback that a highly accurate optical fixed attenuator cannot be obtained.

The present invention solves the above-mentioned problems, easily obtains a target high-precision optical attenuation amount, reduces the occurrence of defective products as much as possible, and is an inexpensive optical fixed attenuator, and the same. It is intended to provide a manufacturing method.

[0010]

In order to solve the above-mentioned problems, an optical fixed attenuator according to the present invention has a pair of ferrules each having an optical fiber strand in the center thereof, each end surface of which is opposed to each other, and the opposed end surfaces are opposed to each other. In a fixed optical attenuator comprising a light attenuating element having a light attenuating film coated on one of the end faces thereof, and a connector for connecting the light attenuating element and an optical fiber cable of a predetermined length, the optical attenuator is opposed to each other. The end face of one of the pair of ferrules is formed as an inclined plane having a first inclination angle (θ1) with respect to the plane (F) orthogonal to the optical axis of the optical fiber wire, and is opposed to the plane. The end face of the other ferrule is formed as an inclined plane having a second inclination angle (θ2) slightly larger than the first angle with respect to the orthogonal plane.

In this case, the first inclination angle (θ1) is
It is preferable that the second tilt angle (θ2) is 3 to 20 degrees, and the second tilt angle (θ2) is 0.1 to 5.0 degrees larger than the first tilt angle.

Further, in the method of manufacturing an optical fixed attenuator according to the present invention, one end of a ferrule of a pair of ferrules having an optical fiber strand in the central portion has a plane (that is perpendicular to the optical axis of the optical fiber strand). F) is formed into an inclined plane having a first inclination angle (θ1), and the end surface of the other ferrule is formed into a second inclination slightly larger than the first inclination angle with respect to the plane. Formed on an inclined plane having an angle (θ2), a light-attenuating film having a predetermined thickness is coated on one of the inclined planes, and then each inclined plane of the pair of ferrules is connected to the optical axis of the optical fiber strand. The fixed optical attenuators are arranged so as to face each other so as to be substantially coincident with each other, and then one of the ferrules is replaced by a light whose attenuation amount of the optical attenuation film is targeted with respect to the other ferrule. It is characterized in that it is rotated in the circumferential direction while being pressed with a predetermined pressure until the attenuation amount is reached.

In this case, a light-transmissive resin is injected between the end faces of the two ferrules, and then one of the ferrules is rotated by a predetermined angle in the circumferential direction with respect to the other ferrule. It is preferable to fix the ferrule.

[0014]

In the optical fixed attenuator and the method for manufacturing the same according to the present invention, since the inclined end faces of the ferrules are formed obliquely at the first and second inclination angles with respect to the optical axis of the optical fiber element, In the abutting state of the inclined planes, the distance on the optical axis between both end surfaces becomes the smallest, and when one of the ferrules is rotated in the outer peripheral direction with respect to the other ferrule, the distance between the optical axes is increased with the rotation. It becomes larger, becomes the largest in the state rotated by 180 degrees, and further rotates, the distance becomes smaller conversely. The distance and the light attenuation amount have a certain functional relationship, and as the distance increases, the light attenuation amount also increases accordingly.

Therefore, one of the ferrules is coated with an attenuating film having a light attenuation amount slightly lower than the target light attenuation amount on the inclined plane of the ferrule, and one of the ferrules is rotated relative to the other ferrule. As a result, the amount of attenuation of the coating film can be corrected, and the target amount of optical attenuation can be obtained when the coating film is rotated by a predetermined angle.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings.

Embodiment 1 FIG. 1 is a longitudinal sectional view of an optical fixed attenuator according to the present invention, FIG.
3 is a longitudinal sectional view of a light attenuating element used in the fixed optical attenuator of FIG. 1, and FIG. 3 is a perspective view of the sleeve of FIG.

In the figure, a fixed optical attenuator 1 is an optical attenuating element 1 for attenuating the amount of light passing through the inside of an optical fiber element wire 2 at a butting portion 11 of a pair of ferrules 3, 5.
c, and a housing 10 for holding the light attenuating element 1c and connecting optical fiber cables (not shown) at the left and right ends of the light attenuating element 1c.

The housing 10 has a female threaded connector 13 for connecting the optical fiber male screw connector (not shown) to the ferrule 3, and a male threaded connector 14 for connecting the optical fiber male screw connector (not shown) to the ferrule 5. A ring-shaped flange 15 fixed to the outer peripheral surface of the ferrule 3, and a compression coil spring that allows the element 1c to move to the right in the figure in order to buffer the shock generated when the optical fiber cable is connected to the optical attenuation element 1c. 16 and 16. Optical attenuator 1c
As shown in FIG. 2, the pair of ferrules 3 and 5 and the light-attenuating film 19 coated on the end surface of the ferrule 5 are provided.
And a split sleeve 18 for fixing the ends of the ferrules 3 and 5, respectively.

Each of the ferrules 3 and 5 is made of, for example, ceramic, metal or the like, and the optical fiber wire 2 made of, for example, a fluorine-based synthetic resin or glass fiber is inserted into the ferrules 3 and 5 and fixed with an adhesive. Things
The butt end surface 3a of the ferrule 3 is an inclined plane having a first inclination angle θ1 with respect to the orthogonal plane F of the axis P of the optical fiber 2, and the butt end surface 5a of the opposing ferrule 5 is formed.
Has been processed and polished so that the second inclination angle is θ2 with respect to the orthogonal plane F. The end face 5a of the abutting portion of the ferrule 5 is coated with a light-attenuating film 19 having a predetermined thickness by a method described later.
The reason why the opposite end faces of the ferrules are made to have different inclination angles θ1 and θ2 is that the ferrules 3 and 5 are always in contact with the inclined end face 3a of the ferrule 3 at the tip Q of the light attenuation film 19. As a result, by rotating in the circumferential direction, a gap of a predetermined length is formed between both ferrules on the optical axis P to obtain a desired light attenuation amount. In order to exert such a function, the first tilt angle θ1
Is preferably 3 to 20 degrees, and the second tilt angle θ2 is the first
The angle is preferably 0.1 to 5.0 degrees larger than the inclination angle θ1. If the first inclination angle θ1 is less than 3 degrees, the reflected light (light traveling backward in the optical fiber wire 2) on the end face 3a of the abutting portion increases, which causes noise. Processing becomes difficult. The second tilt angle θ2 may be a slight angle as long as the light attenuation film 19 on the optical axis P is not in contact with at least the tilt plane 3b of the ferrule 3 in the state of FIG. If the inclination angle is larger than this, the ferrules 3 and 5 will be used later.
By rotating one of the relative to the other,
It is not necessary because the gap L on the optical axis between both ferrules works in the direction of expansion.

As the light attenuation film 19, it is preferable to coat an Inconel material, which is generally used as an ND filter, or a semiconductor material such as chromium, nickel, germanium, and silicon, by a vapor deposition method, and the coating thickness is several tens A. It is preferably in the range of ° to several µm. Although the light attenuating film 19 is coated on the inclined surface 5a of the ferrule 5 in this embodiment, it may be coated on the inclined plane of one of the ferrules. Further, as described above, since the front end portion Q of the light attenuating film 19 is always in contact with the facing inclined end surface 3a of the ferrule 3, there is a possibility that the light attenuating film 19 is damaged, peeled off, or damaged. The presence of these debris on the optical axis P causes a significant decrease in the attenuation accuracy. Therefore, it is preferable that the coating film has a higher adhesion strength to the ferrule 5, and a slight contact between the ferrules may damage the coating surface. In order to prevent the occurrence of such a phenomenon, it is preferable to use a material in which a peeling test is performed in advance and the peeling area of the damping film is about 5% or less of the total surface area, more preferably 0%. The split sleeve 18 is, for example, as shown in the perspective view of FIG.
A cylindrical body made of a material such as a spring material or phosphor bronze is provided with slits 20 and a plurality of holes 21 having an inner diameter of about 0.3 to 0.8 mm in the axial direction.

Next, a method of manufacturing the optical fixed attenuator 1 of the present invention will be described step by step.

First, as the ferrules 3 and 5, the outer shape 2.
Using a high-strength zirconia pipe with a diameter of 6 mm and an inner diameter of 0.127 + 0.01 mm, insert a single-mode optical fiber wire having a core diameter of 10 μm and a clad diameter of 125 μm into the ferrules 3 and 5 as an epoxy fiber. It was adhered and fixed with the two-component adhesive of. Then, each of the ferrules 3 and 5 is cut into a length of 11.3 mm, and the core coaxiality of the optical fiber wire is 1 μm.
Below, and its outer diameter is 2.499 ± 0.005 mm
After centering so that
The inclination angles θ1 and θ2 of the abutting portion end faces 3a and 5a of the ferrules 3 and 5 with respect to the orthogonal plane F of the optical axis P are 8 degrees,
It was cut to 8.5 degrees and each was subjected to optical polishing.

On the other hand, the opposite end surfaces 3b and 5b of the ferrules 3 and 5 were cut so as to form a plane perpendicular to the optical axis P, and then the end surfaces were similarly polished. further,
When inserting the end faces of the ferrules 3 and 5 into the split sleeve 18 which will be described later, be careful not to scratch the sleeve at the corners of the ferrule end faces, and also to provide the missing powder, cutting powder, etc. when the split sleeve is scratched. Is the end face 3 of both ferrules 3 and 5.
A chamfering process of about 0.5 mm was performed on the outer peripheral portion of each ferrule so as not to enter between a and 5a.

Next, the polished inclined plane 5a was coated with a metal of an Inconel material by a vapor deposition method to form a light attenuation film 19.

Here, since the preferable adhesion strength of the damping film 19 is greatly influenced by the substrate heating temperature at the time of vapor deposition, the substrate material and the substrate surface condition, the relation of the adhesion strength at the substrate heating temperature will be described below in advance. investigated.

First, the thickness is 1 mm, the width is 10 mm, and the length is 50.
mm yttria partially stabilized zirconia substrate surface-polished to have a surface roughness of 0.3 μm or less, and six synthetic quartz glass having the same size as the above and a refractive index of 1.45 were prepared, and a fixed amount (12 mg ) Inconel material is placed in a crucible of a vacuum evaporation system, the degree of vacuum is set to 3 × 10 ⁻⁶ Torr or less, and the heating substrate temperature is 30 ° C., 50 ° C., 100 ° C., respectively.
The temperature was sequentially raised to 150 ° C., 200 ° C. and 250 ° C., and vacuum deposition was performed at each heating temperature.

In order to measure the adhesion strength of the thus-deposited metal film 19, a transparent adhesive tape (manufactured by Nichiban Co., Ltd.) having a width of 18 mm, a length of 50 mm and an adhesion strength of 1270 g / 25 mm was attached to the deposition surface, A peel test was carried out by slowly peeling from one end of the tape at a constant speed. As a result, the vapor deposition film deposited on the synthetic quartz glass substrate at a low substrate heating temperature of 30 ° C. hardly peels in the peeling test, but in the case of the partially stabilized zirconia substrate, the substrate heating temperature is 30%.
It was found that most of the films peeled off in the above test, and when the substrate heating temperature was raised to 150 ° C, the peeled area became 5% of the total surface area of the damping film, and when the temperature was further raised, the peeled area decreased. There was found. Therefore, in the present embodiment, the heating temperature of the ferrule 5 during vapor deposition is set to 150.
Decided every time. When the ferrule 5 is heated to 150 ° C. and vapor-deposited, it is preliminarily investigated whether the adhesive agent fixing the optical fiber wire 2 and the ferrule 5 is carbonized and damages the fiber wire. I have confirmed that there is not.

Furthermore, the distance between the crucible and the substrate was kept constant at 140 mm with a vapor deposition device (not shown), and the relationship between the evaporation amount and the light attenuation amount was obtained.

From this relationship, four kinds of optical attenuation values (4.5 dB, 9.5 dB, 14.5 dB, 19.5 d) whose butt loss is about 0.5 to 1.0 dBm less than the target optical attenuation amount are obtained.
The amount of evaporation required for vapor-depositing B) was determined and vapor-deposited on the end face 5a of the ferrule 5 to form the light attenuation film 19.

Next, the ferrule 5 on which the light attenuating film 19 is vapor-deposited in this manner is inserted until the vapor deposition surface comes exactly at the center of the split sleeve 18 having a length of 7 mm.
An ultraviolet adhesive was applied to the hole 21 of the split sleeve 18 on the side where the ferrule 5 was inserted to fix both of the split sleeve 18 and the split sleeve 18, and then ultraviolet rays were irradiated to cure the adhesive.

Then, the end portion of the ferrule 3 on the inclined plane side is inserted into the split sleeve 18, and the tip portion Q of the ferrule 5 is inserted.
The optical attenuating element 1c was manufactured by pushing in until it abuts on the point.

Next, the ferrule 3 is inserted into the split sleeve later so that the light attenuating element 1c has a target light attenuation amount.
Is rotated in the outer peripheral direction by a predetermined phase angle while pressing in the abutting direction, thereby changing the distance L on the optical axis P between the abutting end faces of the ferrules 3 and 5, and changing the optical attenuation amount of the optical attenuating film 19 itself. It was corrected and adjusted to the target attenuation.

Next, the light attenuation amount of the light attenuating element 1c was measured by using the light attenuation amount measuring device 22 shown in FIG. 4 according to the procedure described below.

In the figure, 23 is a light source device for transmitting a predetermined amount of light, 24 is a power meter for measuring the amount of incident light, and the optical attenuating element 1c is held between them.
A rotating device 25 is provided, and an optical fiber cable 26 having a male connector 26a at both ends and an exciter 26b in the middle of the path between these devices, and a male connector 27.
It was connected by an optical fiber cable 27 having a.

The device 25 for holding and rotating the optical attenuator 1c is
A pair of stands 29a and 29b are erected on the base 28, and the stand 29a is the optical fiber cable 2
6 right side male connector 26a with screw 2 provided on the top
9b, and the stand 29b is fixed to the optical fiber cable 2 via the guide 31 of the compression coil spring 30.
7, the left male connector 27a is fixed. 32 is
The ferrule 5 of the light attenuating element 1c is held by an adapter that connects the light attenuating element 1c and the male connectors 26a and 27a. Reference numeral 33 is a lever for rotating the ferrule 3 of the light attenuating element 1c with respect to the ferrule 5 by a predetermined angle in the direction of the arrow in the figure, and is attachable to and detachable from the ferrule 3 with a screw 33a.

Therefore, according to the optical attenuation amount measuring device 22, the optical attenuation amount of the optical attenuation element 1c can be easily corrected to the target optical attenuation amount, and the optical attenuation amount can be corrected to the target optical attenuation amount. You can easily check whether you are there.

In the measuring device 22 constructed as described above, the lengths of 1.
In order to measure the amount of optical attenuation in the case of using the 5 m single mode fiber and not using the optical attenuator 1c at all, as shown by the broken line in the figure, the rotation device 25 is bypassed, and the optical fiber cable 2 is directly connected by the adapter 32.
The right male connector 26a of No. 6 and the left male connector 27a of the optical fiber cable 27 were connected. And
Light having a wavelength of 1300 nm was emitted from the light source device 23, and the light amount Po (dBm) of the incident light was measured by the power meter 24.

Next, the adapter 32 is loosened and the right male connector 26a is fixed to the stand 29a with a screw 29b. The left male connector 27a in which the adapter 32 and the guide guide 31 are integrated is passed through the spring 30 to the stand 29.
Pass it through the sliding hole (not shown) of b, and then insert the ferrule 3
1 is inserted into the male connector 26a through the split sleeve 12 shown in FIG. 1, and the right end of the other ferrule 5 is fixed to this adapter by moving the adapter 32 slightly to the right in the figure. .

By the above operation, the ferrules 3 and 5 are
As a result of being set in the state of FIG. 2, both ferrules are in contact with each other at a constant pressure at the tip portion Q of the damping film 19 due to the pressing force of the compression spring 30.

In this state, the amount of light emitted from the light source device 23 is measured by the power meter 24, and the display unit 2
The light amount value P1 (dBm) displayed by LED on 4a was read. The difference P between the light amounts Po and P1 thus obtained
1-P0 (dB) is the light attenuation amount of the light reducing element 1c when the ferrule 3 is rotated by a predetermined angle with respect to the ferrule 5, and the power meter 2 so that this difference becomes a target value.
While watching 4, the ferrule 3 is gradually rotated in the circumferential direction.

FIG. 5 shows the relationship between the rotation angle (θ3) of the ferrule 3 and the light attenuation amount. In this figure, the ferrule 3 is 180 degrees which is the maximum variable range with respect to the ferrule 5. It is a graph in which the corresponding attenuation amount when rotating up to is plotted on the vertical axis.

As shown in this figure, about -9.5 to -15
It shows that the dBm can be adjusted by rotating the ferrule 3. In this embodiment, as shown by the broken line in the figure, the target value of -10 dBm could be obtained at the rotation angle θ3 of about 10 degrees.

When the LED display on the display section 24a reaches the target value, ultraviolet adhesive is injected through the hole 21 provided in the split sleeve 18 and irradiated with ultraviolet rays to bond and fix the ferrule 3 and the split sleeve 18 together. To do. At this time, it is important that the adhesive does not wrap around the optical axis P between the ferrules. In the light attenuating element 1c of the present embodiment, as shown in FIG. 3, since the split sleeve 18 is provided with a large number of holes 21, it is possible to easily and easily inject the adhesive through these holes. The adhesive could be quickly permeated by a capillary phenomenon due to a slight gap formed between the ferrule and the split sleeve. The adhesive used at this time was an ultraviolet curable resin (Aronix UV-3810, manufactured by Toagosei Co., Ltd.).
Was used for curing in a short time by irradiating with ultraviolet rays.

Ten optical attenuating elements 1c were manufactured by the method described above, and the housing 10 explained in FIG. 1 was incorporated into the optical fixed attenuator 1. When the optical attenuation of the fixed optical attenuator 1 with the target attenuation value of 10 dBm thus obtained was confirmed by the measuring device 22, the difference between the target attenuation and the actually obtained attenuation was ± 0.5 dBm. High-accuracy ones within the range were obtained, and 95% of all were within the above-mentioned accuracy.

A comparison with the conventional fixed optical attenuator having the same number of the fixed optical attenuators 1a and 1b of FIGS. 6 and 7 as that of the fixed optical attenuator 1 of the present embodiment is shown. With the fixed attenuator, the amount of attenuation was only about ± 2 dBm, which was inferior in accuracy to the target site. In addition, about 20% of the ferrule end faces came into contact with the attenuating film and were damaged during the adjustment, making it unusable or not reaching the target optical attenuation value.

The variable distance L between the inclined planes on the optical axis P can be calculated in advance if the ferrule diameter D and the first and second inclination angles θ1 and θ2 are known. The splice loss with respect to the axis deviation Xo when the single mode fibers are butted against each other at the interval Z, the spot size Wo of the fiber, the wavelength λ0 in vacuum,
If the refractive index n in the atmosphere is known in advance, it can be recognized as a theoretical value, so it is possible to obtain a certain amount of light attenuation by calculation. Since various losses other than the distance L such as bending of the shaft are added, the actual attenuation does not match. However, according to the manufacturing method of the present invention, since the optical attenuation amount approaches the target value while rotating any one of the ferrules,
The above-mentioned troublesome calculation is not necessary, and the operator can easily manufacture the optical fixed attenuator having an accurate attenuation amount without requiring any skill.

Example 2 As described in Example 1, most of the manufactured optical fixed attenuators can be adjusted by the manufacturing method of Example 1, but the attenuation amount of the optical attenuator was measured. At times, the value of the attenuation amount shows a value slightly larger than the target attenuation value,
A ferrule that cannot be corrected by rotating the ferrule,
If there is a vapor-deposited ferrule that has been set to a value very close to the target optical attenuation value only with the attenuation film in advance, the optical fixed attenuator with the target optical attenuation amount will be obtained by re-correcting by the method described below. be able to.

That is, the optical attenuator is removed from the adapter 32 and the male connector 26a shown in the schematic diagram of the measuring device of FIG.
The ferrule 3 inserted in the split sleeve 18 is pulled out.

Next, the inclined flat surface 5a of the ferrule 5 with the split sleeve 18 is coated with an epoxy-based two-component curing adhesive in consideration of the optical matching effect, and the inclined flat surface 3a of the ferrule 3 extracted. Butt again and insert into the sleeve until both planes make contact. The optical attenuating element thus obtained is adjusted to the desired attenuation amount while observing the power meter 24 in the same way as in the first embodiment by the measuring device 22 of FIG.

The obtained optical attenuation element has a target attenuation value of 10
It was confirmed that a high-precision fixed optical attenuator of dBm within ± 0.5 dBm can be obtained.
About half of those that did not reach the target attenuation value even if the adjustment was made by can be adjusted to the target light attenuation value, and were manufactured by using the method of Example 1 and this Example 2 together. About 95% of the total number became usable.

In this way, the ferrule 3 and the ferrule 5
When epoxy adhesive is injected between the optical attenuation film 19 and
When there is air in the gap between both ferrules as in the case of Example 1, the optical attenuation amount greatly changes to −5 dB as shown in FIG. 5, but in the case of this example, the air layer Due to the presence of a two-part curable epoxy resin that takes into account the optical matching effect on the
It becomes Bm or less, and the light attenuation value does not change much even if the rotation angle is largely changed during adjustment. The reason is that the Fresnel reflection from the gap and the incident surface of the attenuating film can be suppressed low, and the optical attenuation of the epoxy adhesive injected into the gap is smaller than that of the air layer. Therefore,
According to this adjusting method, since the change in the attenuation amount with respect to the rotation of the ferrule is remarkably small, there is an effect that the adjusting work becomes very easy.

[0053]

As described above, according to the optical fixed attenuator of the present invention, the end portions of the pair of ferrules each having the optical fiber strand have different first and second inclination angles (θ1). , Θ2) is formed on an inclined plane having one of the ferrules and a light attenuating film is vapor-deposited on the inclined plane of one of the ferrules. It is not necessary to accurately set the attenuation amount of the light attenuating film to a predetermined value in advance, as is the case with the related art, simply by rotating the optical attenuator. That is,
A ferrule having a large light attenuation value can be easily adjusted to a desired attenuation value simply by rotating one of the ferrules at the time of assembly.

Further, since the pair of ferrules have their respective inclined planes formed at different inclination angles, they are always in contact with each other at a position apart from the optical axis of the optical fiber strand.
Therefore, even if one of the ferrules is rotated with respect to the other ferrule during the adjustment of the optical attenuation amount or the optical axis adjustment work, only the vicinity of the outer circumferences of the inclined planes of the other ferrules are in contact with each other, and the light coated on the optical axis is contacted. Since the attenuating film does not come into contact with other inclined planes, the attenuating film is not scratched or damaged, and the defect rate of the optical fixed attenuator is significantly reduced. further,
Unlike the conventional device shown in FIG. 7, the optical fixed attenuator of the present invention does not require the work of sandwiching the polyester film with the metal film between the end faces of the ferrule, so that the manufacturing cost can be significantly reduced.

Further, according to the method for manufacturing an optical fixed attenuator according to the present invention, one of the ferrules of the pair of ferrules is rotated by a predetermined angle in the circumferential direction with respect to the other ferrule, and the target is obtained. Since one of the ferrules is rotated in the circumferential direction with respect to the other ferrule, the attenuation amount of the optical attenuating film can be accurately set to a predetermined value in the conventional manner. Even if the obtained optical fixed attenuator has a large variation in optical attenuation, it can be easily and accurately corrected to the desired attenuation value simply by rotating one ferrule during assembly. An optical fixed attenuator is obtained.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an optical fixed attenuator according to the present invention.

FIG. 2 is a vertical sectional view of an optical attenuating element used in the optical fixed attenuator of FIG.

FIG. 3 is a perspective view of the sleeve of FIG.

FIG. 4 is a schematic diagram of an optical attenuation measuring device for measuring the attenuation of the optical attenuating element of FIG.

5 is a diagram showing the relationship between the optical attenuation measured by the optical attenuation measuring device of FIG. 4 and the rotation angle of the ferrule.

FIG. 6 is a vertical sectional view of an optical attenuating element used in a conventional optical fixed attenuator.

FIG. 7 is a vertical sectional view of an optical attenuating element used in a conventional optical fixed attenuator.

[Explanation of symbols]

 1 ... Optical fixed attenuator 1a, 1b, 1c ... Optical attenuator 2 ... Optical fiber strand 3 ... Ferrule 3a ... End face (inclined plane) of ferrule 3 ... Optical attenuation film 5 ... Ferrule 5a ... Ferrule 5 end face (inclined flat surface) 11 ... Butt portion 18 ... Split sleeve 19 ... Optical attenuation film 22 ... Optical attenuation amount measuring device 26 ... Optical fiber cable 27 ... Optical fiber cable F ... Plane orthogonal to optical axis P ... Optical axis θ1 ... First tilt angle θ2 ... Second tilt angle θ3 ... Rotation angle of ferrule 3

Claims (4)

[Claims] 1. A light attenuating element in which each end face of a pair of ferrules having optical fiber strands in the center is opposed to each other, and an optical attenuating film is coated on one of the opposed end faces. In a fixed optical attenuator provided with a connector for connecting the optical attenuating element and an optical fiber cable of a predetermined length, an end face of one of the opposed ferrules is an optical axis of the optical fiber strand. With respect to the plane (F) orthogonal to the vertical plane (F), the end face of the other ferrule facing the orthogonal plane is formed to have a first inclination angle (θ1) with respect to the orthogonal plane. A fixed optical attenuator formed on an inclined plane having a slightly larger second inclination angle (θ2). 2. The first inclination angle (θ1) is 3 to 20.
The optical fixed attenuator according to claim 1, wherein the second inclination angle (θ2) is an inclination angle that is 0.1 to 5.0 degrees larger than the first inclination angle. . 3. A first inclination angle (θ1) with respect to a plane (F) orthogonal to an optical axis of the optical fiber element wire, wherein an end surface of one of the ferrules having a fiber optic element wire in a central portion thereof. And an end face of the other ferrule with a second inclination angle (θ2) slightly larger than the first inclination angle with respect to the plane.
On one of the inclined planes, a light-attenuating film having a predetermined thickness is coated on one of the inclined planes, and then, the inclined planes of the pair of ferrules are arranged so that the optical axes of the optical fiber strands substantially coincide with each other. To form a fixed optical attenuator by arranging the two ferrules opposite to each other, and then setting either one of the ferrules to the other ferrule until the attenuation amount of the optical attenuation film reaches a target optical attenuation amount. A method for manufacturing an optical fixed attenuator, which is characterized by rotating in a circumferential direction while pressing with pressure. 4. A light-transmissive resin is injected between the end faces of both ferrules, and then one of the ferrules is rotated by a predetermined angle in the circumferential direction with respect to the other ferrule, after which the both ferrules are rotated. The method for manufacturing an optical fixed attenuator according to claim 3, characterized in that