JPH01204021A - Optical variable attenuator - Google Patents

Abstract

PURPOSE:To control the quantity of light attenuation without any mechanical movable part by magnetizing a magnetooptical element by a superconducting coil, and varying the quantity of a current supplied to the coil and thus adjusting the quantity of light attenuation. CONSTITUTION:The magnetooptical element 7 is arranged between a polarized wave maintaining optical fiber 10 and a 2nd optical fiber 5, and the superconducting coil 12 is provided to a cylinder 11 made of a ferromagnetic body surrounding the element. The light from the optical fiber 10 is entered into the magnetooptical element 7, attenuated by an analyzer 9, and coupled with a 2nd optical fiber 5. At this time, the current flowing to the superconducting coil 12 is adjusted to adjust the quantity of light attenuation. Consequently, there is no mechanical movable part, so there is not any deterioration in characteristics due to the wear of a component and the life of the device can be prolonged. Further, the power consumption is made extremely small because of the superconducting coil 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a variable optical attenuator that is arranged in an optical path to attenuate light and is capable of changing the amount of optical attenuation.

[Conventional technology]

FIG. 2 is a diagram showing a conventional variable optical attenuator.

In the figure, (1) is a first optical fiber that emits light.

(2) is the first lens that converts the light emitted from the first optical fiber +11 into collimated light, and (3) is the optical attenuation that attenuates the light beam sent from the first lens (2) side. plate, (41 is a second lens that focuses the light transmitted through the light attenuation plate, and (5) is an optical fiber that optically couples the light focused by the second lens 141K.

Next, the operation will be explained. The light emitted from the first optical fiber (1) is converted into collimated light by the first lens (2). This collimated light is then passed through a light attenuation plate (
3), the light is attenuated by the second lens (4), and is optically coupled to the second optical fiber (51).At this time, the light attenuation plate (3) usually has multiple attenuation factors. It has become possible to replace the light attenuation plate (3), and the amount of attenuation of the light becomes variable.As shown in Figure 3, the mechanism for replacing the light attenuation plate (3) is It is common to use a composite damping plate (6) which is shaped like a plate and is divided radially into two parts, each of which has a different attenuation rate.

[Problem to be solved by the invention]

Since the conventional optical variable attenuator is constructed as described above, the mechanism for replacing the optical attenuation plate (3) was a core wall. Further, in the optical variable attenuator having a mechanism as shown in FIG. 3, power is required to rotate the composite attenuation plate (61).

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to provide a variable optical attenuator that can change the amount of optical attenuation without moving parts.

[Means to solve the charge]

The variable optical attenuator according to the present invention magnetizes a Faraday rotator with a superconducting coil and changes the amount of polarization plane rotation of polarized light passing through the Faraday rotator by changing the current cap flowing through the superconducting coil. This is to adjust the amount of transmitted light from the analyzer installed at the subsequent stage.

[Effect]

In this invention, the amount of optical attenuation is determined by changing the amount of current that steadily flows through the superconducting coil.

controlled.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

In Fig. 1, C7) is a magneto-optical element, (8) is a polarizer fixed near the magneto-optical element ()), and (9) is a magneto-optical element (71) which is almost symmetrical to the polarizer 181. The analyzer (2) is placed at the magneto-optical element (71
The first lens is placed behind the polarizer 1B+ when viewed from above, and the second lens (αυtf & The first lens (seeing from the optical element (7)
2), a polarization-maintaining optical fiber (51 is a magneto-optical element) (a second optical fiber placed at a position almost symmetrical to the polarization-maintaining optical fiber with 71 as the center, manufactured by U Company Magneto-Optics) A ferromagnetic cylinder is installed so as to surround the element (7) (although 13 is wound around the ferromagnetic cylinder a11).

The superconducting coil C3, which is insulated from the ferromagnetic cylinder a11, is a current adjusting means for adjusting the current cap flowing through the superconducting coil a3.

The operation of the variable optical attenuator configured as described above will be explained. The light emitted from the polarization-maintaining optical fiber α is collimated by the first lens (2), and only the light in a specific polarization direction that passes through the polarizer (8) enters the magneto-optical element +71. be done. The light transmitted through the magneto-optical element (71) is attenuated by the analyzer +91 and coupled to the second optical fiber +51 through the second lens (4), but the amount of attenuation of the light by the analyzer (91) is.

It depends on the angle of the polarization direction of the light transmitted through the magneto-optical element and the polarization direction transmitted through the analyzer (9). The polarization direction of the light transmitted through the magneto-optical element (71) is determined by the magneto-optical element (71).
Because it depends on the magnetic field applied to 71.

By controlling the magnitude of this magnetic field by adjusting the current cap that flows through the superconducting coil α2, it is possible to adjust the attenuation sound of the light produced by the analyzer (9).

In this case, the adjustable range of the amount of light attenuation is determined by the polarizer (8),
determined by the extinction ratio of the magneto-optical element (7) and the analyzer +91. Other polarized light may be used, and the same effects as in the above embodiments can be achieved.

〔Effect of the invention〕

As described above, according to the present invention, the amount of optical attenuation is adjusted by controlling the amount of current flowing through the superconducting coil, so there is no mechanically moving part in the device, and there is no need to worry about wear and tear of parts. This eliminates characteristic deterioration and has the effect of extending the life of the device. Furthermore, since a current continues to flow through a superconducting coil ideally without any external energy supply, power consumption is ideally zero when the amount of optical attenuation is constant.

[Brief Description of the Drawings] Figure 1 is a sectional view showing the attenuator previously described according to an embodiment of the present invention, Figure 2 is a sectional view showing a conventional variable optical attenuator, and Figure 3 is a sectional view of a conventional variable optical attenuator. FIG. 2 is a sectional view showing an attenuator using a composite attenuation plate as an optical attenuation plate. +71 is a magneto-optical element, az is a superconducting coil, C3 is a current adjustment means, and (9) is an analyzer. Note that the same reference numerals in the two figures indicate the same or equivalent parts.

Claims (1)

[Claims] a magneto-optical element having a Faraday rotation function; a superconducting coil for magnetizing the Faraday rotator; a current adjusting means for varying the amount of current flowing through the superconducting coil; Among them, an optical variable attenuator equipped with an analyzer that detects only one polarization direction.