JPH08179148A - Optical axis adjusting method and device - Google Patents

Abstract

PURPOSE: To provide an optical axis adjusting device which increases the efficiency of temporary adjusting operation for an optical axis by parallel processings for temporary adjustments of plural connection parts and is reduced in cost by eliminating the need for components and devices for the temporary adjustment of the optical axis. CONSTITUTION: This device consists of a reflected light measurement optical system consisting of semiconductor lasers 20 and 23, photodiodes 21 and 24, and optical branching units 22 and 25, six-axial fine adjusting stages 29 and 31 for driving single-mode optical fibers 26 and 28, a fixed stage 30 for fixing an optical waveguide 27, and a controller 32 for driving and controlling the six-axial fine adjusting stages 29 and 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to precise connection between various optical components such as an optical fiber array and a flat plate type optical waveguide array by monitoring the intensity of transmitted light passing through the connecting portion. The present invention relates to a method and an apparatus for automatically performing temporary adjustment so that the intensity of transmitted light transmitted through a connection portion can be detected as a pre-step of adjusting the optical axis.

[0002]

2. Description of the Related Art Devices used for optical communication and optical measurement,
In the optical transmission line of the system, a large number of optical components such as an optical fiber, a flat-plate type optical waveguide, and a semiconductor laser are connected, and moreover, they must be positioned and connected in the order of microns. For this reason, it has become an important issue to speed up the work of connecting optical components to each other, to improve efficiency, and to save labor.

In the optical component connecting step, the degree of freedom of positioning of the optical axis is used as a variable, and the intensity of the transmitted light passing through the connecting portion is used as an evaluation function, and the maximum value of the transmitted light intensity is obtained by a given search algorithm. Therefore, in order to perform such optical axis adjustment, information on the transmitted light intensity is essential,
In order to start the optical axis adjustment, the optical axis of the optical component to be connected must be preliminarily adjusted with an accuracy of about 10 μm so that a detectable level of transmitted light intensity can be obtained.

A conventional example relating to such temporary adjustment of the optical axis will be described with reference to FIGS. 11 and 12. FIG. 11 shows a method of observing the emitted light at the end of the optical waveguide using a microscope. (1) Light from the semiconductor laser light source 1 is applied to one end face of the optical waveguide 3 on the fixed stage 7 through the optical fiber 2 and the optical fiber 2 is scanned using the 6-axis fine movement stage 6. (2) The light propagating through the optical waveguide 3 and emitted from the other end face of the optical waveguide 3 is observed using the microscope 4 and the CCD camera 5. With this procedure, the optical axis position at the connection point 9 is adjusted via the controller 8. FIG. 12 shows a method of temporarily using the multimode fiber 13 having a large core diameter for temporary adjustment. For example, if a multimode fiber having a core diameter of about 50 μm and a core diameter about 5 times as large as that of a single mode fiber is used as a light receiving fiber, it is not necessary to perform high-precision positioning on the light receiving side. It will be easier. In the figure, 14 is an optical power meter, and 15 is a 6-axis fine movement stage.

[0005]

In the conventional methods such as the method of observing the light emitted from the end of the optical waveguide by using the microscope and the method of temporarily adjusting the optical axis by using the multimode fiber, the microscope and the CCD are used. The cost of the optical axis adjusting device increases because parts and devices such as a camera and a multimode fiber are required. Further, in the conventional method, since the method of measuring and observing the light transmitted through the connection portion is adopted, for example, when connecting three parts of the optical fiber, the optical waveguide, and the optical fiber, the input side and the output side are connected. It is necessary to perform sequential adjustment at the connection part, and further, after the optical axis adjustment on one side is completed, when the multimode fiber or microscope is replaced with an optical component to be connected, a positioning error of the fine movement stage will always occur. Therefore, there is a problem that an additional adjustment process for eliminating the error is further required, so that the total number of processes is increased and the working time is increased.

The present invention has been made to solve the above-mentioned problems, and its purpose is to (1) improve the efficiency of temporary adjustment work of an optical axis by parallel processing of temporary adjustment of a plurality of connection parts,
(2) To reduce the cost of the device by eliminating the need for parts and devices required for temporary adjustment of the optical axis.

[0007]

In order to achieve the above-mentioned object, the present invention provides a method for connecting optical parts according to claim 1,
The position of the waveguide part can be determined by irradiating the waveguide part and its peripheral part of the optical part with light from another optical part to be connected and monitoring the reflected light intensity of the waveguide part and the peripheral part. The optical axis is automatically positioned so as to identify and detect the optical signal intensity passing through the connection portion.

Further, in claim 2, a reflected light intensity measuring system comprising a light source for monitoring the reflected light intensity, a photodetector and an optical branching device, and the position of the waveguide portion obtained as a result of the reflected light intensity measurement. The optical axis adjusting device is composed of a fine movement stage for positioning with respect to, and a control system for driving the fine movement stage.

[0009]

According to the optical axis adjusting method of the first aspect, in the optical component connecting step, another optical component to be connected to the waveguide portion (core) and the peripheral portion (clad) of the optical component is to be connected. By irradiating light and monitoring the intensity of the reflected light from the core and clad, the position of the core is specified, and the optical axis is automatically positioned so that the optical signal intensity can be detected. Since it is not necessary to measure the intensity of the optical signal transmitted between the connecting optical components, it is possible to perform the temporary adjustment of the optical axes in parallel at the plurality of connecting portions, and the connecting process can be shortened.

According to the optical axis adjusting device of claim 2,
A device having the operation of claim 1 can be realized.

[0011]

1 to 5 show a first embodiment of the present invention, and an optical axis adjusting method and apparatus of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of an optical axis adjusting device which can carry out the optical axis adjusting method of the present invention. This optical axis adjusting device includes reflected light measuring optical systems 33 and 34 including semiconductor lasers 20 and 23, photodiodes 21 and 24, and optical splitters 22 and 25.
A 6-axis fine movement stage 29, 31 for driving the single-mode optical fibers 26, 28, a fixed stage 30 for fixing the optical waveguide 27, a 6-axis fine movement stage 29,
It is composed of a controller 32 for driving and controlling 31. Here, the optical axis is adjusted at the connection points 35 and 36. In this way, the device configuration is symmetrical with the optical waveguide sandwiched, and the optical axis can be adjusted at the connection points 35 and 36 at the same time.

The principle of the optical axis adjusting method of the present invention will be described with reference to FIG. 2 by taking the optical axis adjustment of the optical fiber 37 and the optical waveguide 38 as an example. Core part 39 and clad part 4 of the optical fiber 37
0, and since the core portion 41 and the cladding portion 42 of the optical waveguide have different refractive indexes of the materials, light is guided through the core portion. For materials having different refractive indices, the reflectance also differs depending on the refractive index. When the light propagating in the air is incident on the material, assuming that the refractive index of the air is 1 and the refractive index of the material is n, the reflectance R of that portion is expressed by Equation 1.

[0014]

[Equation 1]

Here, the value of the current optical fiber is put into the calculation. When the end surface of the optical fiber is a reflecting surface, the optical waveguide 38
If the refractive index of the core portion 41 is n ₁ =, 1.470 and the refractive index of the cladding portion 42 is n ₂ = 1.458, then the reflectance R _{1 of the} core portion R ₁ = 0.036 and the reflectance R _{2 of the} cladding portion R ₂ =
It becomes 0.033. Therefore, the positions of the core portion and the clad portion can be specified by detecting the optical signal intensity difference due to this reflectance difference.

FIG. 3 is a block diagram of an experimental apparatus for confirming the present optical axis adjusting method. This experimental device corresponds to one side portion of the optical axis adjusting device shown in FIG.

The experimental apparatus is a semiconductor laser light source (wavelength:
1.55 μm) 43, optical power meter 44, optical splitter 4
5, a 6-axis fine movement stage 47, a fixed stage 48, single mode optical fibers 50, 51, and a controller 49 for driving and controlling the 6-axis fine movement stage 47. While detecting the reflected light intensity signal 55 from the optical power meter 44, the controller 49 sends the stage drive movement amount signal 54 to 6
It is sent to the axis fine movement stage 47 and the optical axis is adjusted at the connection point 52. The matching grease 46 in the figure is for eliminating the influence of reflection from the coated fiber end surface.

FIG. 4 shows the experimental apparatus shown in FIG.
The connecting optical components (single mode optical fibers 56, 57) used in the confirmation experiment are shown. In the experiment, the single-mode optical fiber 57 is scanned and the single-mode optical fiber 56 is scanned.
The optical axes are temporarily adjusted by measuring the reflected light from the core portion 58 and the clad portion 59 and detecting the reflected light intensity difference.

FIG. 5 is an experimental result and is a graph showing the difference in reflected light intensity between the core portion 58 and the clad portion 59. 0.34 μW in the core part 58, 0.25 μ in the clad part 59
The reflected light intensity of W was measured. Since this measured value is the value after being branched by the 1x2 coupler, the reflected light at the actual connection point is a value that is twice the experimental value, and 0.68μ at the core part.
W, 0.50 μW in the clad part. Here, since the input light intensity from the light source was 110 μW, the reflected light intensity at the core portion 58 expected from the theoretical value in this case is 7.92 μW considering that there are two reflecting surfaces, and The reflected light intensity at the clad portion 59 is 7.26 μW.
In the core part 58, 9.5% of the expected value is observed. This ratio is similar to the actually measured value of the reflected light intensity at the clad portion 59. Considering the loss of the coupler, about 10% of the input light should be observed, and the remaining loss is considered to be due to the parallelism of both end faces of the connection part and the influence of the space between the connection parts. It is shown to be in good agreement with theory, and it is understood that the method of the present invention allows the identification of the core.

6 and 7 are views for explaining the second embodiment of the present invention. In a system in which it is necessary to reduce the reflected return light at the connection portion, a component in which the connection end face is processed obliquely is used. It is shown that the optical axis adjusting method of the present invention can be used even in such a case.

FIG. 6 is a schematic view of a connecting optical component for confirming the optical axis adjustment (optical fibers 60 and 63 (angle 8 °) whose connection end faces are obliquely polished. At this time, when the end faces are parallel to each other, Even if the light emitted from the obliquely polishing optical fiber 63 is reflected by the end surface of the obliquely polishing optical fiber 60, it does not return to the light source with the obliquely polishing optical fiber 63 as a reflecting surface, but the obliquely polishing optical fiber 63 is once inclined at a certain angle. Then, the reflected light of the incident light from the optical fiber 63 returns to the light source side through the optical fiber 63. By utilizing this fact, the same device as that of the first embodiment is used. You can conduct a confirmation experiment by actually tilting one fiber and detecting the difference in reflected light intensity to identify the core part,
Then, centering is performed by returning the fibers tilted so that the optical axes of both fibers are parallel to each other with the reflection point at the core portion as the center of rotation, to the original state.

Therefore, FIG. 7 shows the result of an experiment for measuring the difference in reflected light intensity by the obliquely polished optical fiber using the experimental apparatus of the first embodiment. From the figure, it can be seen that the reflected light intensity difference can be detected as 0.20 μW in the core portion and 0.12 μW in the cladding portion as in the case of the first embodiment. In addition, this value substantially matches the relationship between the theoretical reflectance and the actually measured reflected light intensity described in the first embodiment.

As described above, even in the connection between the end faces that are obliquely polished, the reflected light intensity difference can be detected by temporarily inclining the fiber by the method of the present invention.
It is shown that the optical axis adjustment can be performed in the same manner as in.

FIG. 8 is a diagram for explaining a third embodiment of the present invention, which is basically the same as the device used in the first embodiment. The single mode optical fiber 64 is scanned in the XY directions in the figure using the fine movement stage 65, and the core portion 67 of the single mode optical fiber 66 is automatically specified by the method of the present invention. From the results of this experiment, when the scanning of the fiber was stopped when the set threshold value (0.3 μW) was exceeded, the light intensity of the light source was 4 for 300 μW.
A transmitted light intensity of about 0 μW was obtained. Further, FIG. 9 shows the results of measuring the relationship between the intensity of the transmitted light transmitted through the connection part and the intensity of the reflected light obtained at that time, with a photodiode installed on the output side.

FIG. 9 is a graph in which the vertical axis represents the light intensity and the horizontal axis represents the number of scans. Although the measured values in this figure include the reflected light from the photodiode, the figure shows that there is a correlation between changes in the transmitted light intensity and the reflected light intensity. As described above, it is shown that the transmitted light intensity can be obtained to some extent at the position where the reflected light intensity difference is obtained, and as a result, it is demonstrated that the optical axis temporary adjustment is possible by the method of the present invention. .

FIG. 10 is a schematic view of a connecting part composed of three parts of an optical fiber used for explaining an optical axis temporary adjustment experiment at a plurality of connecting parts which is a fourth embodiment of the present invention. In this experiment, the experimental apparatus configuration of FIG. 1 in Example 1 was used, and the fine movement stages for driving the single mode optical fibers 70 and 71 were set to operate independently. The single mode optical fibers 70 and 71 are separately scanned at the connecting portions 68 and 69, and the reflected light at both end surfaces of the single mode optical fiber 72 is measured. As shown in the previous embodiment, the reflected light intensity becomes high. By the way, the optical fiber of each of them was positioned. Here, when the intensity of the transmitted light passing through the single mode optical fibers 70, 71, 72 was measured, the maximum light intensity of 80 μ when the precision alignment was performed by another method.
18.5 μW was obtained for W. Thus, it was shown that the method of the present invention can perform optical axis temporary adjustment at a plurality of connecting portions in parallel.

In the present invention, the above-mentioned first, second, third,
The type of the optical component, the angle between the end faces, etc. described in Section 4 are not limited, and the present invention can be applied to various optical components having different refractive indexes in the waveguide portion and its peripheral portion. Applications are not excluded from the scope of the invention. Further, the optical axis adjusting method and apparatus of the present invention are useful for temporary adjustment of the optical axis, but can also be applied to precision adjustment.

[0028]

As described above, according to the optical axis adjusting method of the first aspect, the temporary adjustment of the optical axes in the plurality of connection portions can be executed in parallel, so that, for example, the optical fiber, the optical waveguide, the optical When connecting three fiber parts, the adjustment time is halved compared to the conventional method, and even if there are many connections, adjustments can be made at the same time. can get. Also, microscope, C
Since no parts such as a CD camera are required, it is expected that the device can be inexpensively constructed.

Further, according to the optical axis adjusting device of the second aspect, it is possible to realize a device that achieves the effect of the first aspect,
It is extremely effective for practical use.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical axis adjusting device according to a first embodiment.

FIG. 2 is a schematic diagram for explaining the principle of the optical axis adjusting method of the present invention.

FIG. 3 is a configuration diagram of an experimental apparatus for confirming the optical axis adjusting method in the first embodiment.

FIG. 4 is a schematic diagram of a connecting optical component (optical fiber) for confirming the optical axis adjustment in the first embodiment.

FIG. 5 is a graph showing a reflected light intensity difference in the experiment of Example 1.

FIG. 6 is a schematic view of a connection part (obliquely polished optical fiber) for confirming the optical axis adjustment in Example 2.

7 is a graph showing a detected reflected light intensity difference in Example 2. FIG.

FIG. 8 is an optical axis adjusting experimental device in Example 3;

FIG. 9 is a graph showing the relationship between the intensity of transmitted light and the intensity of reflected light and the number of scans in Example 3.

FIG. 10 is a schematic diagram of a plurality of parts for temporary optical axis adjustment experiment in Example 4.

FIG. 11 is a configuration diagram for explaining a conventional example (observation of transmitted light with a microscope).

FIG. 12 is a configuration diagram for explaining a conventional example (using multimode fiber).

[Explanation of symbols]

 1 semiconductor laser light source 2 single mode optical fiber 3 optical waveguide 4 microscope 5 CCD camera 6 6 axis fine movement stage 7 fixed stage 8 controller 9 semiconductor laser light source 13 multimode optical fiber 14 optical power meter 15 6 axis fine movement stage 20 semiconductor laser 21 photo Diode 22 Optical splitter 23 Semiconductor laser 24 Photodiode 25 Optical splitter 26 Single mode optical fiber 27 Optical waveguide 28 Single mode optical fiber 29 6-axis fine movement stage 30 Fixed stage 31 6-axis fine movement stage 32 Controller 33 Reflected light intensity measurement optical system 34 Reflected Light Intensity Measurement Optical System 35 Connection Point 1 36 Connection Point 2 37 Single Mode Optical Fiber 38 Optical Waveguide 39 Core 40 Cladding 41 Core 42 Cladding 43 Semiconductor Laser Light Source 44 Light Power meter 45 Optical splitter 46 Matching grease 47 6-axis fine movement stage 48 Fixed stage 49 Controller 50 Single mode optical fiber 51 Single mode optical fiber 52 Connection point 53 Reflected light measurement optical system 54 Movement amount signal 55 Reflected light intensity signal 56 Single mode Optical fiber 57 Single mode optical fiber 58 Core 59 Clad 60 Oblique polishing optical fiber 61 Cladding 62 Core 63 Oblique polishing optical fiber 64 Single mode optical fiber 65 Pulse stage 66 Single mode optical fiber 67 Core 68 Connection section 69 Connection section 70 Single mode light Fiber 71 single mode optical fiber 72 single mode optical fiber

Claims (2)

[Claims] 1. In the optical component connecting step, light is radiated from another optical component to be connected to the waveguide portion and its peripheral portion of the optical component so that the reflected light intensity of the waveguide portion and the peripheral portion is increased. An optical axis adjusting method characterized in that the position of the waveguide section is specified by monitoring, and the optical axis is positioned so that the optical signal intensity transmitted through the connection section can be detected. 2. A reflected light intensity measuring system comprising a light source for monitoring the reflected light intensity, a photodetector and an optical branching device, and positioning with respect to the position of the waveguide portion obtained as a result of the reflected light intensity measurement. An optical axis adjusting device comprising a fine movement stage for performing the movement and a control system for driving the fine movement stage.