KR970002731B1 - An optic attenuator - Google Patents

Abstract

An optical attenuator which can continuously and exactly variable an optical signal at the wide variable region is disclosed. The optical attenuator comprises: an input part(23,23') of the optical attenuator including a first lens(25,25') and a first supporting means; an output part(24,24') of the optical attenuator having a second lens(26,26') and a second supporting means; an optical sorting plate(60) for sorting lights from the first lens(25) to the second lens(26) and located between the input part and the output part; and a rotation driving means(27) for rotating the input part and the output part.

Description

Optical attenuator

1 is a schematic configuration diagram of a conventional optical attenuator.

2 is a schematic diagram of another conventional optical attenuator.

3 is a block diagram of an optical attenuator according to the present invention.

4A to 4D are graphs showing the variable attenuation region of the optical attenuator according to the present invention.

5 is a graph showing the amount of attenuation according to the rotation angle of the optical attenuator according to the present invention.

6 is a structural diagram of an optical attenuator according to the present invention.

7 (a), (b) and (c) are partial schematic diagrams of an optical attenuator according to the present invention.

8 is an external view of an optical attenuator according to the present invention.

* Explanation of symbols for main parts of the drawings

21 optical attenuator input 22 optical attenuator output

23,24: optical fiber 25: first lens

26: second lens 27: rotation axis

29: cross section of the second lens 30: cross section of the first lens

41: first holder 42: second holder

43: cylinder 44,74: rotating drive body

46: outer case 47,77: spring

49a, 49b, 79a, 79b: stopper 51, 81: auxiliary case

100: optical attenuator

FIELD OF THE INVENTION The present invention relates to optical attenuators used in optical applications, such as optical transmission systems, and more particularly to variable optical attenuators of simple construction that can vary optical signals continuously and precisely over a wide variable range.

In general, in an optical transmission system, an optical signal is transmitted at high power, and the optical signal transmitted at high power is attenuated by an optical attenuator for proper use at the receiving end. The optical attenuator which attenuates the high power optical signal can be used to adjust and calibrate the optical communication system, to measure various kinds or to adjust the interval loss of the optical fiber transmission path, and can be used in various devices related to the light. .

Several types of attenuators have been developed to meet these various applications, one of which is shown in FIG. The conventional optical attenuator shown in FIG. 1 is disclosed in US Pat. No. 5,087,122, which blocks light with the light blocker 6 in parallel light produced by a lens of a predetermined type. The optical attenuator has a first optical fiber 1 and a second optical fiber 2 composed of a core 1a, 2a and a clad 1b, 2b, and of a predetermined type disposed in front of each optical fiber. It consists of a lens (4, 5), a light blocker (6) for blocking the light propagating between the lens, the light rays (3) emitted into the air from the tip of the core (1a) of the first optical fiber 1 Diffusion and propagation with inherent numerical aperture (NA: Numerical Aperture) value passes through the lens 4 of the predetermined type, becomes parallel light, and is connected again through the lens 5 to connect the second optical fiber 2. Proceed to core 2a. The light blocker 6 between the lenses 4 and 5 rotates in the direction of the arrow with the point P as the main axis, and the tip 7 of the light blocker 6 rotates in a clockwise direction by drawing an arc 8 in parallel. Blocking the light beams attenuates the amount of light propagating toward the core 2a.

Another type of optical attenuator is shown in FIG. 2, which is disclosed in Japanese Patent Laid-Open No. 59-192204, which attenuates an optical signal by using an axial shift between optical fibers. The optical attenuators are provided with holders 11 and 12 which are spaced apart from each other by a predetermined distance d to hold the first optical fiber 13 and the second optical fiber 14 inclinedly. The first optical fiber 13 and the second optical fiber 14 are inserted obliquely in the holders 11 and 12, respectively, to reduce back-reflection during optical signal transmission. The basic operation of the optical attenuator is such that the shaft 11 is shifted from the second optical fiber 14 when the holder 11 including the first optical fiber 13 is rotated about the rotational axis 16.

However, the conventional optical attenuator shown in FIG. 1 has a total attenuation within the rotation angle range of 40 ° of the optical blocker, and the range of rotation angle θ is about 20 ° to obtain a practically 20 dB attenuation. to be. Therefore, in order to increase the precision of rotation, there is a disadvantage that a very complicated and expensive fine rotation control device must be attached.

In addition, the conventional optical attenuator shown in FIG. 2 has a problem that the size of the conventional optical attenuator is simple, but there is a lack of practicality. In order to easily rotate the optical fiber, an air gap must be provided between the two optical fibers. The default attenuation thus exists initially. For example, when the air cap d is about 0.4 mm, there is a problem that an initial amount of attenuation of about 10 dB exists at a rotation angle of 0 °. In addition, there is a disadvantage that the total attenuation width is limited to 20dB or less within the rotation angle range 180 °.

The present invention has been made to solve the above problems, and provides an optical attenuator that can attenuate an optical signal in a high degree and a wide area with a low cost, simple structure and a simple structure, and can be used at high power. Has its purpose.

In order to achieve the above object, an optical attenuator according to the present invention comprises an optical attenuator inserted between an optical signal input device including an optical fiber and an optical signal output device to attenuate the optical signal. An optical attenuator input section including a first lens for making an optical signal incident from the optical fiber into parallel light, and a predetermined first support means for supporting a portion of the optical fiber of the first lens and the optical input device; An optical attenuator output section including a second lens positioned opposite said first lens and focusing parallel light, and predetermined second supporting means for supporting a portion of an optical fiber of said second lens and said optical output device; And an optical alignment plate disposed between the optical attenuator input unit and the output unit, the optical alignment plate having a hole having a predetermined size for aligning light traveling from the first lens to the second lens. It is characterized in that predetermined rotation driving means for rotating the light reducer input unit and the output unit, respectively, is provided with a line of rotation parallel to the parallel light spaced at a predetermined interval from one side of the first lens or the second lens. .

Hereinafter, preferred embodiments of the optical attenuator according to the present invention will be described in detail with reference to the accompanying drawings.

3 and 6, the optical attenuator 100 according to the present invention is roughly divided into an optical attenuator input 21, an optical attenuator output 22, and an optical alignment plate 60. 21 is a first lens 25 for outputting incident light as parallel light, an optical fiber 23 having a predetermined length for outputting light to the first lens 25, and the optical fiber 23 and the first lens 25. ) Is composed of a first holder (41) for holding fixed at predetermined intervals, and the optical attenuator output section (22) has a second lens (26) for focusing parallel light and focused on the second lens (26). And an optical fiber 24 having a predetermined length for receiving light, and a second holder 42 for fixing and supporting the optical fiber 24 and the second lens 26 at predetermined intervals, and the optical alignment plate 60. The hole 61 for aligning the light traveling from the first lens 25 to the second lens 26 is provided.

In addition, the optical attenuator input unit 21 and the output unit 22 are respectively coupled to the first holder 41 and the second holder 42 so that the optical attenuator input unit 21 and the entirety of the output unit 22 may be provided in the first lens. (25) or rotary drive members (44, 74) which can be rotated about a rotation axis (27) on an extension line of one end (SP) of the second lens (26). Here, it is preferable that the rotation axis 27 is a line parallel to the light rays emitted from the first lens 25 at a predetermined interval from the one end SP of the first lens 25.

Further, the optical attenuator of the present invention is provided with an outer case 46 which protects the optical attenuator input portion 21 and the optical attenuator output portion 22 and surrounds the entirety thereof.

The first lens 25 and the second lens 26, which are components of the optical attenuator 100 according to the present invention, are rod-shaped green (GRIN: Gradient Index) lenses, and the optical fibers 23 and 24 are formed of a core ( Core: 23a, 24a and clad; 23b, 24b.

The operation and operation of the optical attenuator according to the present invention configured as described above, which can attenuate light according to rotation of the optical attenuator input unit or output unit, are as follows.

3 and 6, the light L emitted from the end of the optical fiber core 23a of the optical attenuator input unit 21 into the air spreads with a unique numerical aperture NA and then proceeds to the first. After passing through the lens 25 becomes parallel light, the parallel light is aligned while passing through the hole 61 of the light alignment plate 60 and focused again through the second lens 26 of the rotating part 22 to form an optical fiber. Proceeds to core 24a.

At this time, when the optical attenuator input portion 21 is rotated 180 ° from its original position (shape shown in solid line) as shown by the dashed line by the rotation driver 74 (FIG. 6), the first lens of the input portion 21 The optical fiber 23 and the optical fiber 23 are converted into positions of the first lens 25 'and the fiber 23' under the rotation axis 27 so that the light L emitted from the optical attenuator input portion 21 is an optical alignment plate. Reflected or absorbed by 60 prevents it from entering the optical attenuator output 26. That is, the light entering the optical fiber core 24a of the optical attenuator output unit 22 by traveling from the optical attenuator input unit 21 according to the rotation of the optical attenuator input unit 21 becomes variable (that is, attenuation). The attenuation range is adjusted according to the rotation angle of the optical attenuator input 21. Such contents will be described with reference to FIG. 4 as follows.

4 (a) to (d) show the first and second lenses facing each other when the optical attenuator output part 22 is fixed and the optical attenuator input part 21 is rotated at a predetermined angle along the rotation axis 27. It is the schematic which showed the cross section 29, 30 of (25, 26) superimposed on XY plane. Here, the area of the cross section 30 of the first lens 25 represents the total amount of light emitted from the fiber core 23a. In addition, the diagonal portion 32 is a portion where the end surfaces 29 and 30 of the first and second lenses 25 and 26 overlap each other, and the parallel light L emitted through the first lens 25 of FIG. The area incident through the second lens 26 (that is, incident light) is shown.

In FIG. 4, the dotted line 31 is a trajectory according to the rotation of the center point C of the cross section 30 of the first lens 25 with respect to the rotation axis 27 (an axis not shown in the ground but perpendicular to the XY plane). (FIG. 4 (a)). As the rotation angle θ of the first lens end surface 30 increases, the size of the diagonal portion 32 gradually decreases (FIG. 4B), and when the rotation angle θ is 180 °, the diagonal portion 32 ) The area becomes 0 (Fig. 4 (c)). Here, the rotation angle θ is 0 ° when the first and second lenses 25 and 26 are exactly coincident with each other and are opposed to each other, and 180 ° when the first and second lenses 25 and 26 are completely shifted.

If the rotation angle θ passes 180 °, the area of the oblique portion 32 is increased again (Fig. 4 (d)). As a result, the amount of light emitted from the optical attenuator input 21 and entering the optical attenuator output 22 gradually decreases as the rotation angle of the optical attenuator input 21 increases (within 180 degrees). The rotation angle θ of the optical attenuator input portion 21 and the area S of the oblique portion 32 are calculated by the following equation.

S = πr ² -r ² (sinθ + πθ / 180) (1)

Where r is the cross-sectional radius of the first and second lenses.

If the light rays emitted from the lens cross section are uniform throughout the cross section, the area S of the first lens cross section 30 and the oblique portion 32 is compared using the above equation and the amount of attenuation according to the rotation angle θ is obtained. (dB) is determined by the following equation.

dB = ­10log (1-sinθ / π-θ / 180) (2)

5 is a graph showing the change in the amount of attenuation (dB) according to the change of the rotation angle using the equation (2). As the rotation angle increases, the attenuation gradually increases, and as the rotation angle increases above 150 °, the attenuation increases greatly. Substantially, the range of commercially available attenuation is 20 dB, and the range of rotation angle for obtaining this range in the present invention is around 150 ° as shown in the drawing, so that the amount of attenuation can be simply obtained without a precision device.

However, the change in the attenuation amount dB according to the rotation angle change of the optical attenuator input portion 21 shown in FIG. 5 does not substantially change like a solid line but changes like a dotted line, which is the rotation of the optical attenuator input portion 21. This is because the light attenuated by the light is diffracted or diffusely reflected at the hole 61 of the light alignment plate 60 so that a part of the light is incident on the light attenuator output 22. In addition, the dotted line portion to the left of the solid line is due to the undesirable light saturation phenomenon. Accordingly, the degree of light attenuation may be improved by rotating the light attenuator output unit 22 to improve the degree of light attenuation due to the undesirable incident light as described above. That is, first, the optical attenuator input unit 21 is rotated to obtain an appropriate optical attenuation rate. Then, when the optical attenuator output unit 21 is rotated to increase the optical attenuation ratio, the attenuation amount change as shown in FIG. 5 can be obtained.

6 is a substantial configuration diagram of the variable optical attenuator 100 according to the present invention, in which the optical fibers 23 and 24 are fixed positions which are machined eccentrically with respect to the central axis 27 of the holder 41 and 42, respectively. The first and second lenses 41 and 42 are respectively attached to the end faces of the first and second holders 41 and 42 facing each other to maintain a predetermined interval. In order to reduce the amount of reflection of light, opposite surfaces of the first and second lenses 25 and 26 may be subjected to an anti-reflective coating. In addition, a light absorbing agent may be coated on the surfaces of the first and second holders 41 and 42 except for the first and second lenses 25 and 26 as needed for use, thereby minimizing noise due to scattering.

The first and second holders 41 and 42 are inserted into the predetermined cylinder 43 and aligned with respect to the rotation axis 27. In order to rotate the first and second lenses 25 and 26, the optical fibers 23 and 24, and the holders 41 and 42 about the rotation axis 27, the disk-shaped rotation driving bodies 44 and 74 may be first. In order to be attached to one side of the two holders 41 and 42, respectively, and to prevent the rotary drive members 44 and 74 including the first and second holders 41 and 42 from being pulled out of the cylinder 43, the rotary drive member ( Springs 47 and 77 are inserted between 44 and 74 and outer case 46. When the rotary drives 44 and 74 rotate more than 180 °, there is a concern that the area of the oblique portion 32 is increased again as shown in FIG. 4 (d). To prevent this, as shown in FIG. 6, protrusions 48 and 78 are attached to one side of the rotary drive bodies 44 and 74, and first and second stoppers 49a on opposite surfaces of the outer case 46. , 49b, 79a, and 79b were attached so that the rotation of the rotary drives 44 and 74 could be performed within a 180 ° range, thereby minimizing damage due to torsion of the optical fibers 23 and 24.

In addition, the optical fibers 23 and 24 also rotate together when the rotational actuators 44 and 74 rotate, and thus damage to the optical fibers 23 and 24 may occur, thereby preventing the optical fibers of the present invention. The attenuator 100 has auxiliary cases 51 and 81 which can include optical fibers 23 and 24 of a predetermined length, respectively. One side of the auxiliary case (51, 81) is attached to one side of the outer case 46, the other side of the coupling material (52, 82) (e.g., to fix the optical fibers 23,24) , An epoxy material), to weaken the torsional damage of the other optical fibers 23 and 24 due to the rotation of the rotary drives 44 and 74. The light alignment plate 60 is positioned between the first and second lenses 25 and 26 and fixed to the cylinder 43.

7 (a), (b), and (c) show an optical attenuator input portion 21 and an optical attenuator output portion 22 including holders 41 and 42 in the optical attenuator 100 of the present invention shown in FIG. ) Excerpt from the detailed excerpt configuration. Referring to FIG. 7A, the optical fibers 23 and 24 are eccentrically inserted into the first and second holders 41 and 42 by a predetermined position P at the center of the rotation shaft 27. The centers of the cross-sections of the first and second lenses 25 and 26 are placed at the end portions K and L of the optical fibers 23 and 24, respectively, and one side surface of the first and second lenses 25 and 26 is formed. 25 s and 26 s are both positioned to coincide with the center of the rotation shaft 27.

In order to increase the optical accuracy, the first and second lenses 25 and 26 are attached to the circular structures 55 and 56 into which the optical fibers 23 and 24 are inserted, as shown in FIG. 55 and 56 may be inserted into the holders 41 and 42, respectively, to be fixedly supported. This is an embodiment for precisely adjusting the positions of the optical fibers 23 and 24, the holders 41 and 42, and the first and second lenses 25 and 26.

In addition, in order to further improve the optical precision, the structure of FIG. 7 (b) may be improved as shown in FIG. 7 (c), which is a circular structure 55 and 56 into which optical fibers 23 and 24 are inserted. After inserting the first and second lenses 25 and 26 to a predetermined depth, the circular structures 55 and 56 may be inserted into the holders 41 and 42 to be fixedly supported. This is another embodiment in which the adhesion and connectivity of the holders 41 and 42, the optical fibers 23 and 24, and the first and second lenses 25 and 26 are stabilized.

8 is an external configuration diagram of a variable light attenuator according to the present invention. Referring to FIG. 8, a portion of the rotary drive bodies 44 and 74 is exposed on the upper surface of the outer case 46, so that the optical attenuator input and output units 21 and 22 (FIG. 3) can be easily rotated. It was made. The reference angles 58a, 58b, 88a, and 88b are indexed to predetermined portions of the rotary drive bodies 44 and 74 and the outer case 46 so that the rotation angles of the rotary drive bodies 44 and 74 can be confirmed. I could see it.

As described above, the optical attenuator according to the present invention can provide a larger amount of attenuation than the conventional one by the rotation of an optical fiber with a rod-shaped green lens. Since the range is from 0 ° to 150 °, simple fabrication is possible without precision devices, and low cost of the variable optical attenuator can be achieved. In addition, since the structure using the optical lens is less than 2dB insertion loss, it can provide an advantage that can be used even at high power.

Claims (12)

An optical attenuator inserted between an optical signal output device of an optical signal input device including an optical fiber to attenuate the optical signal, the optical attenuator comprising: a first optical signal incident from the optical fiber of the optical signal input device to make parallel light; An optical attenuator input section including a lens and predetermined first supporting means for supporting a portion of the optical fiber of the first lens and the optical input device; An optical attenuator output section including a second lens positioned opposite said first lens and focusing parallel light, and predetermined second supporting means for supporting a portion of an optical fiber of said second lens and said optical output device; And an optical alignment plate disposed between the optical attenuator input unit and the output unit, the optical alignment plate having a hole having a predetermined size for aligning light traveling from the first lens to the second lens. And a predetermined rotation driving means for rotating the optical attenuator input unit and the output unit, respectively, having a line parallel to the parallel light spaced at a predetermined distance from one side of the first lens or the second lens as a rotation axis. 2. An optical attenuator according to claim 1, further comprising an outer case surrounding them to protect the optical attenuator input and the optical attenuator output. The auxiliary case according to claim 1 or 2, further comprising an optical fiber of a predetermined length and attached to both sides of the outer case to prevent torsional damage of the optical fiber due to rotation of the optical attenuator input unit or output unit. And an optical attenuator further provided. According to claim 1 or 2, wherein a predetermined protrusion is provided on each of the rotation driving means and a stopper on each of the opposing surfaces of the outer case so that the optical attenuator input portion or output portion is rotated only within a 180 ° range. Featured optical attenuator. The optical attenuator according to claim 1, wherein the first and second supporting means are coupled by a cylindrical body having a predetermined shape spaced apart from each other. The rotary drive means is coupled to one side of each of the first and second support means to rotate the first and second support means including the first and second lenses and the optical fiber in the cylindrical body. An optical attenuator, characterized in that. 7. A spring according to any one of claims 1, 2 and 6, wherein a spring is provided between the outer case and the respective rotation drive means to prevent the respective rotation drive means from being separated from the first and second support means. The optical attenuator characterized by the above-mentioned. The optical attenuator according to claim 1, wherein the amount of reflected light from the lens is reduced by applying an antireflection coating to the first lens and the second lens. The optical attenuator according to claim 1, wherein light scattering is prevented by adding a light absorbing agent to the first and second supporting means. The optical attenuator of claim 1, wherein the rotation axis is on an extension line of one side of the first lens or the second lens. The optical precision of claim 1, wherein the optical fiber is inserted into a fiber support member, and the first and second lenses are attached to the support member, and then the support member is inserted into and fixed to the first and second support means, respectively. Optical attenuator characterized in that the improved. The support member of claim 1 or 11, wherein the first and second lenses are attached to the optical fiber by inserting the first and second lenses to a predetermined depth in the fiber support member into which the optical fiber is inserted. The optical attenuator, characterized in that to improve the structural stability by inserting into the first and second supporting means respectively.