JPH0634819A - Optical fiber type attenuator - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a light quantity attenuator for an optical waveguide that is small and can be mass-produced at low cost. [Structure] A plurality of optical fibers 1 including a core and a clad,
2 are bundled and partially stretch-fused, and the stretch-fused portion 3
Is a fiber optic coupling body in which the thickness of the clad is thinner than the wavelength of the transmitted light and the transmitted light can be transferred to the mutual optical fibers. The leaky optical fiber 1 is a leaky optical fiber 1, and the remaining optical fiber is a transmission fiber 2 for transmitted light. As the light leakage treatment, light scattering treatment, light transmission treatment or light absorption treatment is preferable. When the transmitted light is incident from the incident side end of the transmission fiber 2, a part of the transmitted light is diverted to the core of the light leakage fiber 1 at a portion where the thickness of the cladding is thin in the middle. A part of the light that has been blocked from passing through the cladding of the transmission fiber 2 becomes a cladding mode wave as it is.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber type attenuator which is used in an equalizer, a receiver padting (light receiving amount buffer), etc. and which attenuates and adjusts the intensity of transmitted light propagating through an optical fiber or the like.

[0002]

2. Description of the Related Art In an optical communication system or the like, from the viewpoint of an allowable range of received light intensity of an optical receiver or prevention of damage to the optical receiver, the optical fiber propagates through an optical fiber such as a flexible fiber or an optical waveguide rod. In some cases, the amount of signal light to be used must be attenuated.

Conventionally used light intensity attenuators are generally relatively large in size, and when they must be provided for each terminal of an optical communication circuit, they have a problem that they occupy too much equipment space. There is also a problem that each one is very expensive and very uneconomical.

Although small-sized and filter-interpolated attenuators have been known in the past, they usually have a problem that they are difficult to produce and unsuitable for mass production.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a light quantity attenuator for an optical fiber which is small in size and can be mass-produced at low cost.

[0006]

The light quantity attenuator of the present invention made to achieve the above object comprises a plurality of optical fibers 1 and 2 composed of a core and a clad, as shown in the front view of FIG. An optical fiber combination in which a part of the bundle is stretched and fused, and the thickness of the cladding of the stretched and fused portion 3 is smaller than the wavelength of the transmitted light so that the transmitted light can be transferred to the mutual optical fibers. A part of the plurality of optical fibers 1 and 2 is a leaky optical fiber 1 whose both end faces are leak-treated, and the remaining optical fibers are transmission fibers 2 of transmitted light.

Light scattering treatment is preferable as the light leakage treatment. In accordance with this, or the light translucency treatment may be performed alone. Light absorption treatment may be used.

[0008]

The transmitted light travels in a wave form in the core mode from the incident side to the exit side while totally reflecting inside the optical fiber in which the clad is tubularly covered with the clad at the interface with the clad. In the present invention, the leaky fiber 1 and the transmission fiber 2 are partially stretch-fused, and the stretch-fused portion 3 has a thin cladding. When the transmitted light is incident from the incident side end of the transmission fiber 2, a part of the transmitted light tries to pass through the clad enclosure at a portion where the thickness of the clad is thin. When the thickness of the clad that combines both the transmission fiber 2 and the leaky fiber 1 is thinner than the wavelength of the transmitted light at the stretch-fusion unit 3, several% to several tens% of the entire transmitted light is diverted to the core of the leaky fiber 1. . A part of the light that has been blocked from passing through the cladding of the transmission fiber 2 becomes a cladding mode wave as it is. Light redirected to the core of the leaky fiber 1 is the leaky fiber 1
Leaks from the end of the.

The amount of light of the core mode wave of the transmission fiber 2 is attenuated and travels to the emission side. The attenuation rate is the degree of coupling between the transmission fiber 2 and the leaky fiber 1, the optical path length that the light converges toward the fused portion, and then branches, the both ends 4 of the leaky fiber 1.
Fluctuates depending on the state of. A desired attenuation rate can be secured by controlling these.

In manufacturing, the transmission fiber 2 and the light leakage fiber 1 may be brought into contact with each other, heated, and stretched and fused.

[0011]

EXAMPLES Examples of the present invention will be described below. FIG. 1 is a front view of an embodiment of a light quantity attenuator to which the present invention is applied.
As shown in FIG. 1, a flexible long transmission fiber 2 composed of a core and a clad covering the core and a short optical leakage fiber 1 are bundled in parallel. Both are made of glass and have a diameter of 1
The diameter of the central core is 25 μm, and the diameter of the central core is 9.2 μm. Both fibers 1 and 2 are stretched and fused near the center of the leaky fiber 1,
At that portion, the stretched and fused portion 3 is formed to be thin.

The end surface of the end portion 4 of the light leaking fiber 1 is obliquely cut and processed for scattering, and a black pigment is applied for light absorption processing.

An optical fiber type attenuator was manufactured by the method shown in FIGS. As shown in FIG. 2, a long transmission fiber 2 and an end-faced short light leakage fiber 1 were bundled in parallel, and a parallel clamp 5 was attached to both fibers 1 and 2 to bring a flame 6 close to each other.

As shown in FIG. 3, a light source 7 for laser light having a wavelength λ = 1310 nm is provided at one end of the transmission fiber 2 and a light quantity measuring device 8 is provided at the other end, and the laser light is emitted from the light source 7 to the transmission fiber 2 in the core mode. The amount of light emitted and emitted through the transmission fiber 2 was measured by the light amount measuring device 8 on the other end side.
Both fibers 1 and 2 in contact with each other were heated with a flame 6 aiming at the vicinity of the center point of the leaky fiber 1, and the parallel clamp 5 was pulled in the wide direction as shown by the arrow. While pulling, both fibers 1 and 2 were fused.

The amount of light received by the light quantity measuring device 8 decreased with the progress of the stretch fusion. 25 dB by monitoring the light quantity measuring device 8
The stretching was stopped when. An attenuator having an attenuation target error of ± 1 dB or less was obtained.

In the case of the optical fiber type attenuator thus obtained, when the transmitted light is incident from one end of the transmission fiber 2, a part of the transmitted light is guided to the core of the leaky optical fiber 1 by the extension fusion portion 3. Change. The light entering the light leakage fiber 1 is absorbed by the black pigment at its end face. The light that has not been absorbed is repeatedly reflected back and forth between the end surface and the peripheral surface of the fiber, focused on the tip, and scattered from the tip. A part of the remaining light amount in the transmission fiber 2 is converted into the cladding mode. Attenuated light is emitted from the other end core of the transmission fiber 2.

The end portion 4 of the light leakage fiber 1 may not be obliquely cut, but may be subjected to other light leakage treatment. That is, the tip may be tapered in a conical shape, or may be scattered light processed by frosted glass treatment. The antireflection film coating treatment may be performed by coating a transparent film thinner than the wavelength of transmitted light, or only the light absorption treatment may be performed by coating a dark color pigment or the like.

In manufacturing the attenuator, the end face of the leaky optical fiber 1 may be processed by heating and fusion-stretching instead of heating and then fusion-stretching the end face of the leaky optical fiber 1 in advance. .

[0019]

As described above in detail, according to the present invention, it is possible to obtain an optical fiber type attenuator which is small in size and can be mass-produced at low cost. The damping rate can also be controlled precisely.

[Brief description of drawings]

FIG. 1 is a front view of an embodiment of a light quantity attenuator to which the present invention is applied.

FIG. 2 is a diagram showing a state in which a transmission fiber and a leaky fiber are set in parallel and clamped.

FIG. 3 is a diagram showing a state of being heated and stretched.

[Explanation of symbols]

Reference numeral 1 is a leaky fiber, 2 is a transmission fiber, 3 is a stretch-fused portion, and 4 is an end of the leaky fiber.

Claims (4)

[Claims] 1. A plurality of optical fibers consisting of a core and a clad are bundled and a part thereof is stretch-fused, and the clad at the stretch-fused part is thinner than the wavelength of the transmitted light and the transmitted light is mutually transmitted. Optical fiber combination that can be transferred to other optical fibers, some of the optical fibers are leaky optical fibers with both end faces subjected to light leak treatment, and the remaining optical fibers are transmission fibers for transmitted light. An optical fiber type attenuator. 2. The optical fiber type attenuator according to claim 1, wherein the light leakage treatment on both end faces of the light leakage fiber is a light scattering treatment. 3. The optical fiber type attenuator according to claim 1, wherein the light leakage treatment on both end faces of the light leakage fiber is a light transmission treatment. 4. The optical fiber type attenuator according to claim 1, wherein the light leakage treatment on both end faces of the light leakage fiber is a light absorption treatment.