JPS59192204A - Optical attenuator - Google Patents

Abstract

PURPOSE:To reduce size and to permit easy setting of an attenuating rate by setting respectively the core centers of optical fibers embedded in two optical fiber holders in prescribed positions at the end face of the non-opposing holder and the end face of the opposing holder. CONSTITUTION:An optical attenuator is constituted of two circular cylindrical holders 5, 6 embedded therein with single mode fibers in such a way that the one end of the core center coincides with the center of the holders and the other end deviates therefrom by several 10mum and having the end faces polished to specular surfaces and an outside pipe 4 having the inside diameter slightly larger than the outside diameter of the holder. The holder 6 is fixed in the pipe and the holder 5 is made rotatable in the pipe apart by a specified distance (d) from the end face of the holder 6. The size is thus reduced and the easy setting of the attenuating rate is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical attenuator inserted between optical fibers to attenuate optical power propagating within the optical fibers, particularly a single optical attenuator.
This invention relates to an optical attenuator for mode fibers.

Generally, an optical attenuator is one of the important optical circuit components used for adjustment and calibration of optical communication systems, various measurements, and section loss adjustment of optical fiber transmission lines.

Optical attenuators for multimode fibers often use metal vapor deposition films to attenuate optical power. On the other hand, in an optical attenuator for a single mode fiber, in order to attenuate optical power, in addition to the method of using a metal vapor deposited film, as shown in FIG. 3
There is also a method of providing a gap d between the holders 1 and 2.

FIG. 2 shows the relationship between the distance between the end faces and the amount of optical attenuation in the latter case. This method has a simple structure and is suitable for miniaturization.

However, if you simply change the distance between opposing optical fibers to obtain the required amount of optical attenuation, the attenuator dimensions will differ depending on the amount of attenuation, which may be difficult to use in civil engineering cases where mounting dimensional accuracy is strict. .

Further, if fine adjustment of the attenuation amount is required, the opposing fiber must be moved in the axial direction with high precision.

For example, to adjust to 20 dB±0.5 dB, the second
As can be seen from the figure, fine adjustments of ±0, 1- are required.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical attenuator which is small and whose attenuation amount can be easily set, which overcomes the drawbacks of the gap-type optical attenuator described above.

Describing the structure of the present invention, the present invention provides an optical attenuator that is inserted between optical fibers, one of which is fixed in a pipe that is an outer cylinder of the optical attenuator, and the other is rotatable, and both end surfaces are mirror-finished. The two finished optical fiber holders are
The two optical cores are arranged opposite to each other with a distance of several hundred μm to several τm, and the core center of the optical fiber inside the holder is located at the center of the same end face on the non-opposing holder end face, and the core center of the optical fiber is located at the center of the same end face on the non-opposing holder end face, and on the opposing holder end face. are optical attenuators that are both equally eccentric by several tens of μm from the center of the same end surface.

The basic configuration and embodiments of the present invention will be described below with reference to the drawings.

The basic configuration of the optical attenuator of the present invention is shown in FIG.

The optical attenuator of the present invention consists of two cylindrical holders in which a single mode fiber is embedded in the holder so that the core center coincides with the holder center at one end, and the other end is eccentric by several tens of micrometers, and the end surfaces are polished to a mirror finish. 5, 6, and an outer cylinder nozzle 4 having an inner diameter slightly larger than the outer diameter of the holder for aligning the two holders. The holders 5 and 6 are placed in a vibrator so that they face each other with their eccentric cores facing each other. The holder 6 is fixed in the pipe, and the holder 5 is spaced a certain distance from the end face of the holder 6. The fiber core 7 in the holder 5 can be rotated in the vibrator at a distance of several hundred μm to several -) d.During the polar 550 rotation, the fiber core 7 in the holder 5 rotates around the center of the vibrator (center of the holder) as shown in Fig. 4. The axis deviation tY between the core 8 in the fixed holder and the core 7 in the rotating holder is
When the amount of core eccentricity is represented by X)'=2xcos(1).

FIG. 5 shows the relationship between the rotation angle θ and the amount of axial deviation of the core. The amount of axis deviation of the core varies in the range from 0 to 2x by rotating the treader 5.

In the optical attenuator of the present invention, the minimum amount of attenuation is given by the core ino (the distance between the end faces), the center of the core is eccentric, and a reduction device is further added due to the rotation of the large holder.

By combining the two, it is possible to obtain a wide attenuation range and also to easily determine minute amounts of attenuation with good reproducibility.

FIG. 6 shows the relationship between the amount of core deviation and the amount of attenuation when the distance d between the fiber end faces is used as a parameter. However, a light core with a core diameter of 1074 m is used.

To describe a specific example of implementing the present invention, a single-mode fiber with a core diameter of 10 μm was used as the yellow fiber. When the distance between the end faces of the optical fibers was 1.6 m and the amount of centering of the optical fiber core with respect to the center of the eyeper holder was 40 μm, force characteristics were obtained as shown in FIG. That is, by rotating the holder, the light intensity could be set between 20 and 3 dB with good reproducibility. In order to statically determine the attenuation amount ``It'' with an accuracy of ±0.5 dB within this range, it was only necessary to determine the rotation angle with an accuracy of ±5°, which was easy.Also, the external dimensions of the entire optical attenuator were , about 10 mg in diameter and 20 yrtm in length,
I was able to make it smaller.

As explained above, according to the present invention, the structure of the optical attenuator can be studied and simplified, and therefore the optical attenuator can be made smaller, and the required amount of attenuation can be set with high precision.

Therefore, it is extremely useful if applied to a simple variable attenuator or fixed attenuator in a single mode fiber optical system.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an example of a conventional optical attenuator, and FIG. 2 is a cross-sectional view of an optical fiber having a core diameter of 10 μm. A characteristic diagram showing the relationship between separation and attenuation amount, FIG. 3 is a sectional view of the basic configuration of the optical attenuator of the present invention 6, FIG. 4 is a diagram for explaining the axis misalignment between the cores, and FIG. A characteristic diagram showing the relationship between the amount of deviation of the core and the amount of optical attenuation when the distance between the holders is used as a parameter. FIG. 3 is a characteristic diagram showing the relationship between the holder rotation angle and the attenuation amount in a specific example of implementation. 4... External tube vibrator, 5... Marked rotating optical fiber holder, 6... Group fixed optical fiber holder, 7, 8...
...Optical fiber core. Figure 1 Optical fiber r, q

Claims (1)

[Claims] In an optical attenuator that is inserted between optical fibers, two optical fiber holders, one fixed and the other rotatable, each having a mirror-finished end surface, are placed inside a vibrator, which is an outer cylinder of the optical attenuator. They are arranged facing each other with a distance of several hundred μm to several meters apart,
The core centers of the optical fibers embedded in the two optical fiber holders are located at the center of the non-opposing holder end faces, and are equally eccentric by several tens of μm from the center of the opposing holder end faces. An optical attenuator characterized by: