JP3335902B2 - Optical attenuator and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical attenuator comprising an optical fiber and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, there has been known an optical attenuator having a longitudinal sectional structure as shown in FIG. This optical attenuator has a structure in which a translucent dielectric thin film G is deposited on at least one of the optical fiber ends 3 and 4 of the optical fibers 1 and 2, and the dielectric thin film G is sandwiched between the optical fiber ends 3 and 4. The amount of light attenuation is adjusted by the thickness of the deposited dielectric thin film G.
The light hν incident on one optical fiber 1 (or 2) is attenuated by the dielectric thin film G, and the attenuated light hν ′ is guided to the other optical fiber 2 (or 1). .

[0003]

However, in the above-mentioned conventional optical attenuator, in order to manufacture the optical attenuator, at least the dielectric thin film G is disposed on the ends 3 and 4 of the optical fibers.
It is necessary to perform a vapor deposition step for vapor deposition and a coupling step of aligning and integrating the optical fibers 1 and 2 with each other. Further, these vapor deposition steps and the coupling step cannot be performed by one continuous manufacturing process. There is a problem that the number of manufacturing steps is large and workability is poor.

When a part of the light hν incident on one of the optical fibers 1 (or 2) is reflected on the contact surface between the optical fiber ends 3 and 4 and the dielectric thin film G, the reflected light deteriorates the transmission quality. Therefore, generally, optical fibers 1 and 2
The optical fiber ends 3 and 4 are cleaved and polished obliquely, and a dielectric thin film G is deposited on the polished surface to prevent the generation of reflected light. However, since the optical characteristics of the optical attenuator vary depending on the polishing accuracy of the optical fiber end faces 3 and 4, it has been difficult to manufacture optical attenuators having uniform optical characteristics at a high yield.

In order to obtain the optical attenuation of only the dielectric thin film G, it is necessary to align the optical fibers 1 and 2 with extremely high precision so that no coupling loss occurs. However, this high-precision alignment is difficult, and from this point, it is also difficult to manufacture an optical attenuator having uniform optical characteristics at a high yield.

Further, the optical fibers 1 and 4 are fixed with an adhesive material having optical transparency, or the vicinity of the optical fiber ends 3 and 4 is fixed with an adhesive while being supported by a glass member or a ceramic member. , 2 are integrated. However, a change in the refractive index of the adhesive due to a change in temperature or humidity causes an increase in reflected light, and a difference in the thermal expansion coefficient between the optical fibers 1 and 2 and the optical fiber ends 3 and 4 may cause a bond. Due to the deviation, there is a problem that the reflected light at the dielectric thin film G increases, the optical coupling efficiency decreases, and the like.

SUMMARY OF THE INVENTION The present invention has been made to overcome the above-mentioned problems of the prior art. In an optical attenuator formed of an optical fiber, at least one portion of the optical fiber is provided. The structure was provided with a tapered light attenuating portion which was thinned by integral molding by heating and stretching and twisted .

According to this structure, the light incident on one optical fiber end of the optical fiber is attenuated by the amount of light attenuation corresponding to the tapered shape of the light attenuating portion, and the attenuated light is guided to the other optical fiber end of the optical fiber. Is done.

At this time, since the optical attenuator has a structure in which the optical attenuator is twisted , the amount of light attenuated in the optical attenuator is finely adjusted, resulting in a more accurate optical attenuator.

In a method of manufacturing an optical attenuator formed of an optical fiber, at least one of the optical fibers may be used.
By heating and stretching while twisting the portion, the thinned tapered light attenuating portion is integrally formed.

According to this manufacturing method, the light attenuating portion for attenuating the light can be integrally formed with one optical fiber, and an optical attenuator having a very simple structure and low cost and high accuracy can be realized.

Further, light of a constant intensity is incident on one optical fiber end of the optical fiber, the intensity of light emitted from the other optical fiber end of the optical fiber is observed, and the amount of light attenuation between the incident light and the emitted light is observed. The amount of light attenuation of the light attenuating section is adjusted based on the above.

According to this manufacturing method, a desired amount of light attenuation can be set with extremely high accuracy.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the optical attenuator of the present invention will be described below with reference to the drawings. FIG. 1A is a perspective view showing an external structure of an optical attenuator according to the present embodiment, and FIG. 1B is a longitudinal sectional view thereof.

1A and 1B, an optical attenuator 5 includes an optical fiber FB in which a tapered optical attenuator 6 is integrally formed, and a thermal expansion coefficient of glass, ceramics, crystallized glass, or the like. Substantially cylindrical holding member (hereinafter, referred to as a substrate) 7 formed of a small hard material
It is comprised including.

A long groove 8 is formed in the substrate 7 along the longitudinal direction. The light attenuating portion 6 and both end portions 9, 10 of the optical fiber FB are accommodated in the long groove 8, and both end portions 9, 10 are accommodated therein. Long groove 8 with adhesive AD such as thermosetting resin
Is fixed inside. The substrate 7, the light attenuating section 6 accommodated in the substrate 7, and both end portions 9, 10 are formed by the optical attenuator 5.
Of the optical fiber FB is a so-called pigtail.

The optical attenuator 5 has a bidirectional property of attenuating the light hν incident on one of the pigtails of the optical fiber FB by the optical attenuator 6 and guiding the attenuated light hν ′ to the other pigtail. are doing.

Next, a method of manufacturing the optical attenuator 5 will be described with reference to FIG.
This will be described with reference to FIG. First, as shown in FIG. 1A, the jacket of the optical fiber FB is partially removed to partially expose the optical fiber FB. Both end portions 9, 10 of the exposed portion 6 'are mounted on an actuator (not shown).

Next, as shown in FIG. 1B, the exposed portion 6 'is heated and softened by a flame 11 of a mixed gas of oxygen and propane, and the actuator is activated to start and end the end portions 9, 10 Is pulled apart in the X and X 'directions in the figure, whereby the softened portion of the exposed portion 6' is stretched straight along the optical fiber axis. Due to this heating and stretching, the softened portion of the exposed portion 6 'is thinned, and the core diameter and the cladding diameter are gradually reduced along the axial direction of the optical fiber axis, and the tapered light attenuating portion 6 becomes thicker again. Is formed.

Here, the amount of light attenuation changes according to the angle between the optical fiber axis and the tapered shape in the light attenuating section 6 (hereinafter referred to as the taper angle). That is, in order to form the light attenuating portion 6 having a desired light attenuation amount, the taper angle needs to be equal to or more than a predetermined angle, and when the taper angle is changed, the light attenuation amount in the light attenuating portion 6 changes. I do.

Therefore, in the present embodiment, the optical fiber F
The temperature of the flame 11, the heating range of the exposed portion 6 ′ by the flame 11, and the heating start timing, while light of a constant intensity is incident from one pigtail of B and the intensity of the light emitted from the other pigtail is observed one by one. The above heating process and stretching process are performed while adjusting control parameters such as a heating end timing, a pulling force applied to the exposed portion 6 ′, a start timing and an end timing of applying the pulling force, and the output light with respect to the incident light is adjusted. The heating process and the stretching process are completed when the light attenuation reaches a desired value, thereby forming the light attenuating section 6 having the desired light attenuation.

After the light attenuator 6 is formed, the optical fiber FB is housed in the long groove 8 of the substrate 7 shown in FIG.
To complete.

As described above, the optical attenuator 5 of the present embodiment
Since the light attenuator 6 is integrally formed into one optical fiber FB by the above-described heating and stretching, there is no coupling structure in which separate optical fibers are coupled as in the conventional optical attenuator shown in FIG. It has excellent transmission quality and stable optical characteristics without causing problems such as generation of reflected light and reduction of optical coupling efficiency.

Further, the light attenuating section 6 is connected to one optical fiber F.
Because it is realized in B, it becomes a very simple structure,
Manufacturing costs can be reduced.

In addition, since the above-described heating and stretching are performed in one continuous manufacturing process, the number of manufacturing steps can be significantly reduced and workability can be improved. Further, by the above-described heat treatment and stretching treatment, an optical attenuator having uniform optical characteristics can be manufactured with a high yield.

In addition to the amount of light attenuation, the wavelength selectivity can be adjusted according to the tapered shape of the light attenuating section 6. For this reason, for example, when the transmission loss characteristic for each wavelength in the communication optical fiber line transmitting the optical signal of two or more wavelengths is different, the optical attenuator 5 is coupled to the communication optical fiber line, Applications such as attenuating high-intensity wavelength components to compensate for transmission loss characteristics are possible.

Further, the optical signal of two or more wavelengths transmitted through the optical fiber line for communication is adjusted to the optimum light receiving sensitivity of the light receiving element built in the optical receiver, and the light emitting element built in the optical transmitter is adjusted. It is possible to improve the overall transmission quality of the optical fiber transmission network by introducing two or more optical signals emitted from the optical fiber into a communication optical fiber line with the same optical intensity.

In the above description, one optical attenuator 6
Has been described, but as shown in FIG.
The light attenuation portions 6a may be formed at a plurality of locations. With such a structure, when the amount of light attenuation cannot be adjusted with high accuracy by only one light attenuator 6, an effect such as fine adjustment by a plurality of light attenuators can be obtained. Further, the amount of light attenuation for light of two or more wavelengths can be individually set in each light attenuator.

Further, as shown in FIG. 3 (b), the above-mentioned heating process and stretching process are performed while twisting both end portions 9 and 10 in opposite directions ya and yb, so that the light attenuating section 6 is twisted. May be added. When the optical attenuator 6 is twisted in this way, a desired amount of optical attenuation can be finely adjusted, and a more accurate optical attenuator can be formed.

As for the type of the optical fiber FB, a single mode optical fiber, a multimode optical fiber,
The optical attenuator of the present invention can be formed by using various types of optical fibers such as an optical fiber using quartz glass.

Further, in the optical attenuator 5 shown in FIG. 1, the mechanical strength is increased by holding the optical attenuator 6 on the substrate 7, but as shown in the longitudinal sectional view of FIG. 6 and the substrate 7 may be covered with a heat-shrinkable tube 12, housed in a metal cylindrical tube 13 and fixed with an adhesive 14 to further increase the mechanical strength.

The reason why the light attenuation effect can be obtained by forming a thinner tapered light attenuation portion 6 at one end of the optical fiber FB having a uniform diameter is that the core diameter in the light attenuation portion 6 becomes smaller. It is thought that the effective cross-sectional area is reduced, and the amount of light leaked to the clad becomes the amount of light attenuation. In addition, since the clad diameter is reduced, it is considered that the clad passes through the clad and leaks out of the light attenuating section 6.

[0032]

As described above, according to the present invention, since the light attenuating portion for attenuating light is formed by one optical fiber, an optical attenuator having a very simple structure and a low cost and high accuracy is provided. Can be provided. Furthermore, since the optical attenuator is formed of a single optical fiber and realizes a structure without a mechanical coupling portion, an optical attenuator having stable optical characteristics and uniform optical characteristics is manufactured with a high yield. be able to.

Further, since molding can be performed by a continuous manufacturing process of heating and stretching while twisting the light attenuating portion, the number of manufacturing steps can be significantly reduced and workability can be improved.

Further, by adjusting the tapered shape of the light attenuating section, it is possible to form light attenuators having various light attenuations.

Further, by adjusting the taper shape, an optical attenuator having wavelength selectivity can be formed, so that applications such as improvement of transmission quality in an optical fiber transmission network are possible.

[Brief description of the drawings]

FIG. 1 is a perspective view and a longitudinal sectional view showing a structure of an optical attenuator according to an embodiment.

FIG. 2 is an explanatory diagram illustrating a method for manufacturing an optical attenuator according to the present embodiment.

FIG. 3 is an explanatory diagram showing a modified example of the optical attenuator of the present embodiment.

FIG. 4 is a longitudinal sectional view showing a structure in a case where the optical attenuator of the present embodiment has a structure with higher strength.

FIG. 5 is a longitudinal sectional view showing a structure of a conventional optical attenuator.

[Explanation of symbols]

 5: Optical attenuator 6, 6a: Optical attenuator 6 '... Exposed part 7: Substrate 8: Long groove 11: Flame FB: Optical fiber

Claims (3)

(57) [Claims] 1. An optical attenuator formed of an optical fiber, wherein at least one portion of the optical fiber is thinned by integral molding by heating and stretching , and twisted.
An optical attenuator comprising a tapered optical attenuator to which is added . 2. A method for manufacturing an optical attenuator formed of an optical fiber, wherein at least one portion of the optical fiber is twisted.
A method for manufacturing an optical attenuator, wherein a thinned tapered optical attenuator is integrally formed by heating and stretching. 3. A light having a constant intensity is incident on one optical fiber end of the optical fiber, the intensity of light emitted from the other optical fiber end of the optical fiber is observed, and the amount of light attenuation between the incident light and the emitted light is measured. and adjusting the optical attenuation amount of the optical attenuating unit based on claim 2
3. The method for manufacturing an optical attenuator according to claim 1.