JPH0354773B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical field to which the invention pertains The present invention relates to a method and apparatus for automatically measuring various transmission characteristics of optical fibers. Taking the measurement of a multimode fiber as an example, items to be measured include loss, band, structure, etc., and the present invention measures the loss, band, etc. of light incident on one end of an optical fiber and light emitted from the other end. The present invention relates to an automatic measuring method and device for measurement items that require measuring the relationship between light and light.

(b) Prior art and its problems The measurement items necessary for evaluating optical fibers include the outer diameter of the fiber, the geometric structure such as the core diameter and its non-circularity, fiber parameters such as the refractive index distribution, and the optical There are transmission characteristics represented by loss, transmission band, etc. Among these, optical loss and transmission band are especially important when designing a transmission line. Regarding optical loss, we use the transmission method, which directly measures the amount of attenuation of light propagating in the optical fiber under test, the backscattering method, which measures the amount of attenuation of Rayleigh backscattered light generated in the fiber, and the transmission band method. Typically, measurements are made in the frequency domain or in the time domain, but in either case, the measurement requires the measurement of the end of the optical fiber to be measured, the output port that transmits the light from the light source on the measuring instrument side, and the photodetector. A connection must be made with the entrance port that transmits the light to. FIG. 8 shows a typical example of a conventional transmitted light detection device.
The optical fiber 31 to be measured has its end 31a connected to the light source 3.
2 or an optical fiber 36 connected to the photodetector 33
and is connected at the connecting portion 35. optical fiber 3
4 is inserted and connected between the optical fibers 36 connected to the light source 32, and is used for adjusting the propagation mode (for example, obtaining steady mode excitation).

However, in the above conventional device, once,
That is, each time one item is measured, the optical fiber to be measured must be replaced and the connection must be made again. Here, since the connection of optical fibers requires high-precision connection, there was a problem in that each measurement was very time-consuming.

(c) Purpose of the Invention The present invention has been made in view of the above-mentioned conventional circumstances, and is capable of sequentially measuring multiple items with high precision and efficiency by simply setting the optical fiber to be measured on the measuring device once. It is an object of the present invention to provide a method for measuring characteristics of an optical fiber and an apparatus therefor.

(d) Structure of the Invention The present invention includes a setting stage in which both ends of an optical fiber to be measured are set on a carrier so as to be approximately parallel to each other;
A plurality of measurement stages are provided in which optical measurement system entrance/exit ports are arranged approximately in parallel, and the carrier on which the optical fiber to be measured is set is sequentially moved from the setting stage to the measurement stage, and the optical fiber to be measured is sequentially moved from the setting stage to the measurement stage. In the method and apparatus for optically measuring characteristics of an optical fiber to be measured, both ends of a measurement optical fiber and the optical measurement system input/output port are aligned, and the optical measurement system input/output port of the measurement stage is aligned with the optical measurement system input/output port. It is necessary to place the optical fiber on a means movable in the light input/output direction via a means movable in a direction perpendicular to the output direction, and to align both ends of the optical fiber to be measured with the light input/output port. Accordingly, the set stage optically automatically detects the axial positions of the tips of both ends of the optical fiber to be measured with respect to the reference position of the carrier, and each measurement stage detects the light input/output port and the reference position of the carrier. The distance in the axial direction of the optical fiber to be measured from the position of the optical fiber to be measured is automatically detected, and the axial distance between the tips of both ends of the optical fiber to be measured and the inlet/output port for the light is determined by means movable in the direction of incidence and emission of the light. automatic adjustment to a predetermined value, and further optically automatically align both ends of the optical fiber to be measured and the light input/output port by means movable in a direction perpendicular to the light input/output direction. Features.

(e) Effects of the Invention According to the above configuration, once both ends of the optical fiber to be measured are set on the carrier at the set stage, the both ends of the optical fiber to be measured and the optical measurement system are then set at the plurality of measurement stages. Axial direction and axial alignment with the input and output ends can be performed optically and automatically.

(F) Embodiments of the Invention FIG. 1 shows a schematic diagram of an apparatus for carrying out the method of the present invention. In the present invention, the optical fibers to be measured 10 to 10d have both ends 1 to 1d placed on the carriers 11 to 11d in the optical fiber holders 7 to 10d.
7d at set stage A,
Next, the measurement stage B is sent in the direction of arrow 12,
Moved to C, D, E. In each measurement stage, a pair of moving tables 13a, 13a' to 13d, 1
Fiber holders 8a, 8a'~ placed on 3d'
Measurement side optical fibers 6 are connected to photodetectors 3a to 3d and light sources 2a to 2d on 8d and 8d', respectively.
a, 6a' to 6d, 6d' are set. In such a measuring device, an optical fiber to be measured placed on a carrier is sequentially moved through stages A→B→C→
Feed from D to E, and move carriers 11 to 1 so that the optical fiber to be measured and the measuring instrument side optical fiber are coaxially aligned.
1d, the light source, optical fiber on the measuring side, optical fiber to be measured, optical fiber on the measuring instrument side, and photodetector are connected in series, and the characteristics of the optical fiber to be measured can be measured. I can do it. However, in measuring the characteristics of optical fibers, the accuracy of optical fiber connections is extremely important.
That is, when connecting optical fibers to each other, the mode of light entering the optical fiber to be measured and the mode of light emitting from it must be maintained at the connection portion. For example, as mentioned in the explanation of the prior art in FIG. 8, the optical fiber 34 is inserted into the optical fiber 36 to obtain steady mode excitation. The light must be incident on the optical fiber to be measured. Taking the example of a graded index fiber, in order to connect the optical fibers while maintaining the excitation mode, the distance between the end faces must be within 10 to 15 μm, and the axis misalignment must be within μm. is desirable.

Hereinafter, the alignment of the tips of the optical fibers in the method of the present invention will be explained. First, the spacing between the end faces of the optical fibers requires high precision as described above. Here, both ends 1 to 1d of the optical fibers set on carriers 11 to 11d are moved together with the carriers to each measurement stage B to E and positioned, but the positional accuracy of both ends 1 to 1d of the optical fibers to be measured on each stage is is determined by the positioning accuracy of the optical fiber set at set stage A and the carrier at each measurement stage. However, in order to obtain an end face spacing of 10 to 15 μm or less as described above, each of these tolerances is allowed to be only a few μm or less. In order to solve this problem, in the present invention, the carrier 1 at the tip of the optical fiber end 1 to be measured is first set at the set stage A.
Optical position detection is performed with respect to the reference position of 1. Since optical detection is non-contact, it can improve measurement accuracy and is effective in keeping the optical fiber clean. As an example, the following method is used for this purpose. Figure 2 shows the concept of the detection method.
1 is the end of the optical fiber to be measured, 20 is a photodiode, 21 is a lens system for focusing the image of the end 1 of the optical fiber to be measured on the photodiode 20, 22
23 is a transmitted illumination light, and 23 is a lens system for illumination. The above is the optical fiber tip position detection device 1 to be measured.
4. (See Figure 1 Set Stage A)
This detection device 14 is arranged at a predetermined position relative to the reference position of the carrier 11. Further, as the photodiode 20, an array of minute photodiodes as shown in FIG. 3 is used. Here, for example, if the interval 24 between the minute photodiodes is 25 μm and the magnification of the lens system 21 is 40 times, appropriate illumination light is obtained from the illumination systems 22 and 23 in FIG. This makes it possible to detect the relative position of the tip surface of the optical fiber end 1 to be measured with respect to the reference position of the carrier 11 with an accuracy of 25 μm÷40≈0.6 μm. For this diode, a plurality of rows arranged as shown in FIG. 4 may be used. Furthermore, in order to accurately detect the position of the tip of the optical fiber to be measured, the detector may be moved on a plane perpendicular to the end of the optical fiber to be measured to scan the position of the end of the optical fiber. FIG. 5 is a conceptual diagram thereof. The array of diodes detects the surface to be measured from 25 to 25a to 2.
By moving the optical fiber in the direction of arrow 26 to the position 5k, the position of the tip surface of the optical fiber to be measured can be accurately grasped for each surface to be measured, and if the end is chipped,
If it is slanted, the state of the end face can be known, and even if there is some error in the position perpendicular or parallel to the axis of the optical fiber to be measured, the scanning range is wide, so detection can be performed reliably. Fifth
Similar detection can be performed by using photodiodes having a plurality of columns as shown in FIG. 4 instead of the scanning shown in the figure. Further, the detected value can be stabilized by performing appropriate temporal or geometric calculation processing. In the above example, a lens system is used for the illumination system and detection system, but instead of a lens system, it is also possible to use a small diameter optical fiber or a bundle of optical fibers, depending on the accuracy of detection. You can choose. With respect to the position of the tip surface of the optical fiber end 1 to be measured relative to the reference position of the carrier 11 detected as described above, in the present invention, the measuring instrument side optical fibers 6a, 6a' to 6d, 6d' and the ends 1 to 1d of the optical fibers to be measured are aligned. For this purpose, a movable table 13 on which holders 8a, 8a' to 8d, 8d' of the optical fibers on the measuring instrument side are mounted.
a, 13a' to 13d, 13d' to arrow 15 in Fig.
, that is, in the direction of light emission and light incidence, in order to obtain a predetermined distance according to the detection distance between the tip of the optical fiber to be measured and the tip of the optical fiber on the measuring instrument side. For example, as shown in FIG.
If the set stage A detects that l ₁ , then if the distance l 2 between the tip of the optical fiber 6 on the measuring instrument side and the reference position 16 on the carrier 11 can be found on _{the measurement stage, then l 2 and} l It is sufficient to move the movable table 13 so that the difference from ₁ is the interval necessary for measurement.

Note that when positioning is performed by moving a plurality of carriers linearly, contact between the optical fiber to be measured and the optical fiber on the measuring side may become a problem, but according to the above example, when the carriers 11 to 11d move, the optical fiber on the measuring side 6a, 6a' to 6d, 6d' to the moving table 13
By moving the optical fibers a, 13a' to 13d and 13d', they can be retracted as seen from the ends 1 to 1d of the optical fibers to be measured, so that contact between the optical fibers can be easily avoided. Furthermore, when connecting optical fibers, a refractive index matching agent, so-called matching oil, is generally applied, but since the position of the optical fiber end can be detected before applying the matching oil, detection accuracy may deteriorate or become impossible due to matching oil. There is no fear that this will happen.

In the above example, the moving table 13 was moved directly in the direction of the optical fiber axis, but in order to ensure operation, the distance _l2 between the reference plane on the carrier and the tip of the optical fiber 6 on the photometer side was automatically measured before this movement. It is a good idea to do this. In order to obtain the value of l ₂ at each measurement stage, for example, as shown in FIG. It's good to do that. Here, the tip position of the measurement side optical fiber 6 is set to be at a constant position from the beginning with respect to the movable table 13, and the sensor 17 is connected to the carrier 11.
By detecting the distance between the reference position and the moving table 13, the above-mentioned l ₂ can be found.

According to the positioning method according to the present invention, since the axial positioning of the optical fiber to be measured and the measurement side optical fiber can be automatically performed on each measurement stage, it is possible to automatically position the optical fiber under measurement on each measurement stage.
This has the advantage of not being directly affected by the positioning accuracy of the carrier that has been moved.

Note that when positioning is performed by moving a plurality of carriers linearly, contact between the optical fiber to be measured and the optical fiber on the measuring side may become a problem, but according to the above example, when the carriers 11 to 11d move, the optical fiber on the measuring side 6a, 6a' to 6d, 6d' to the moving table 13
By moving the optical fibers a, 13a' to 13d and 13d', they can be moved backward as seen from the ends of the optical fibers to be measured 1 to 1d, so that contact between the optical fibers can be easily avoided. Furthermore, when connecting optical fibers, a refractive index matching agent, so-called matching oil, is generally applied, but since the position of the optical fiber end can be detected before applying the matching oil, the detection accuracy may deteriorate due to the matching oil. There is no fear that it will be impossible.

Next, the alignment of the optical fiber to be measured and the measuring instrument side optical fiber will be explained. In the present invention, the fiber holders 8a and 8 on the measuring instrument side are arranged so that the optical power detected by the photodetectors 3a to 3d is maximized.
a' to 8d and 8d' are connected to the measuring instrument side optical fiber 6, respectively.
Adjustments are made by moving in a direction perpendicular to the axes a, 6a' to 6d, 6d', that is, in a direction perpendicular to the direction in which light enters and exits. This includes fiber holders 8a, 8a' to 8
d, 8d′ in a plane perpendicular to the axis of the optical fiber.
It is sufficient to gradually change the position in the direction, monitor the optical power, and automatically find the peak of the optical power, but this method is used in fusion splicing of single mode optical fibers, etc. It's a method. In the present invention, this axial alignment is preferably performed after the axial positioning of the optical fiber to be measured and the measuring instrument side optical fiber. As mentioned above, since the axial spacing is minute, the change in the detected light power at the photodetector in response to changes in the amount of axial misalignment becomes large, which improves the precision and high speed of axial alignment. This is because it can improve reliability and reliability.

In the above embodiments, an example is shown in which optical fibers are used for the light exit port from the light source and the light entrance port for the photodetector, but it is also possible to use a lens system instead of the optical fiber. In addition to the above, it is also conceivable to directly emit the light using a light source with a wide output width, or to make the light directly enter the detector. However, in the case of such direct input/output, the positioning accuracy is not severe, so precise positioning as explained in the above embodiment is not necessary.

In the above explanation, an example was shown in which the stage for setting the optical fiber to be measured and the detection of the axial position of the tip surface of the optical fiber to be measured are performed on the same stage A, but before measurement, they can be performed on separate stages. It doesn't matter how many times or places you go. By separating the setting stage from the measurement stage as described above, it is possible to move the optical fiber to be measured while setting it, thereby improving the efficiency of measurement work.

(g) Effects of the invention As described above, the present invention has the following effects.

By providing a set stage and a plurality of measurement stages, and by sequentially transporting the optical fiber to be measured between these stages (in steps using a conveyor, etc.) and performing a predetermined measurement each time, it is possible to By once setting both ends of the fiber to be measured on the carrier, measurements of multiple optical fiber measurement items can be performed sequentially and simultaneously on multiple optical fibers to be measured at each measurement stage. This has the advantage of saving labor.

In the above measurements, the precision alignment between both ends of the optical fiber to be measured and the input/output port of the optical measurement system is performed.
(After being transported by a conveyor or the like and roughly aligned,) the mutual axial distance is optically and automatically determined by a means (moving table; 13a, 13a' to 13d, 13d') movable in the light input/output direction. means (fiber holders; 8a, 8' to 8d,
8d'), the axial alignment is optically and automatically adjusted, and as a result, both ends of the optical fiber to be measured and the input/output port of the optical measurement system are precisely aligned in the axial direction and aligned with each other. done,
Precise measurements can be made.

This has the advantage that it becomes possible to successively measure multiple items of the optical fiber to be measured with high precision and efficiency without requiring any human intervention.

The above axial positioning is performed by (optically) detecting (optically) the axial distance l ₁ between the tips of both ends of the optical fiber to be measured and the reference position of the carrier on the set stage. Using l ₁ as a reference, for example, in each of the other measurement stages, the distance l ₂ between the input/output port of the optical measurement system and the reference position of the carrier described above is simply detected using a sensor, etc. Since the desired axial distance l ₂ - _{l 1} between the tips of both ends of the optical fiber to be measured and the entrance/exit port of the optical measurement system is automatically adjusted, the precise axial positioning process itself is extremely easy. It has the advantage of being easy and efficient.

[Brief explanation of drawings]

FIG. 1 is a top view showing the overall outline of the optical fiber characteristic measuring device according to the present invention, FIG. 2 is a conceptual diagram of the device for detecting the tip position of the optical fiber to be measured on the set stage, and FIGS. Conceptual diagram showing a specific example of the arrangement of the photodiodes in Figure 2, No. 5
The figure is a conceptual diagram showing a method for precisely detecting the tip position of an optical fiber to be measured, and FIGS. 6 and 7 are conceptual diagrams showing a method for measuring the axial distance between the tips of the optical fiber to be measured and the optical fiber on the measuring instrument side. , FIG. 8 is a top view showing an overall outline of a conventional optical fiber characteristic measuring device. 1 to 1d...Both ends of the optical fiber to be measured, 2a to 1d
2d...Light source, 3a-3d...Photodetector, 6a'-
6d'... Output port of light from the light source, 6a to 6d...
Light entrance to photodetector, 8a, 8a' to 8d, 8
d'... Means movable in a direction perpendicular to the light input/output direction, 10 to 10d... Optical fiber to be measured, 11
~11d...Carrier, 13a, 13a'~13
d, 13d'... Means movable in the light input/output direction.

Claims (1)

[Scope of Claims] 1. A set stage in which both ends of an optical fiber to be measured are set on a carrier so as to be approximately parallel to each other, and a plurality of measurement stages in which optical measurement system entrance/exit ports are arranged generally in parallel, are provided. The carrier on which the optical fiber to be measured is set is sequentially moved from the setting stage to the measuring stage, and at each of the measuring stages, both ends of the optical fiber to be measured and the input/output port of the optical measurement system are positioned, and the optical measuring system is optically exposed. In the method of measuring characteristics of a measurement optical fiber, the optical measurement system entrance/exit opening of the measurement stage is movable in a direction perpendicular to the direction of incidence and exit of the light; The positioning of both ends of the optical fiber to be measured and the light input/output port is performed by optically automatically adjusting the axial position of the tips of both ends of the optical fiber to be measured relative to the reference position of the carrier on the set stage. detecting the detection, and automatically adjusting the axial distance between the tip of both ends of the optical fiber to be measured and the light input/output port to a predetermined value by means movable in the light input/output direction on each of the measurement stages; A method for measuring characteristics of an optical fiber, comprising automatically aligning both ends of the optical fiber to be measured and the light input/output port using a means movable in a direction perpendicular to the light input/output direction. . 2. The method according to claim 1, wherein the method for optically automatically detecting the axial position of the tip of both ends of the optical fiber to be measured in the set stage with respect to the carrier reference position uses a photodiode. Optical fiber characteristics measurement method. 3. The optical fiber characteristic measuring method according to claim 1, wherein the distance in the axial direction of the optical fiber to be measured between the light input/output port and the reference position of the carrier is automatically detected. 4. In each of the measurement stages, the axial distance between the light input/output port and the reference position of the carrier can be automatically detected by a sensor mounted on the means movable in the input/output direction. A method for measuring characteristics of an optical fiber according to claim 3. 5. The optical fiber characteristic measuring method according to claim 1, wherein the means movable in the light input/output direction is a moving table. 6. The method for measuring characteristics of an optical fiber according to claim 1, wherein each of the optical measurement system entrance and exit ports is a measuring instrument side optical fiber. 7. Claim 1, wherein each of the optical measurement system entrance and exit ports comprises a lens system.
Optical fiber characteristics measurement method described in Section 1. 8. The optical fiber characteristic measuring method according to claim 6, wherein the means movable in a direction perpendicular to the light input/output direction is a fiber holder. 9. Claim 6, characterized in that the alignment between both ends of the optical fiber to be measured and the light input/output port is performed by axial alignment subsequent to adjustment of the axial distance. A method for measuring characteristics of an optical fiber described in . 10 The optical automatic axis alignment between both ends of the optical fiber to be measured and the light input/output port allows light to pass through the optical fiber to be measured by the action of the optical measurement system, and the detected optical power is 9. The method for measuring characteristics of an optical fiber according to claim 8, wherein the method is carried out by moving the fiber holder in a direction perpendicular to the direction in which the light enters and exits so as to maximize the amount of light. 11 A means movable in the light input/output direction for mounting the optical measurement system input/output port, and a means disposed thereon movable in the direction perpendicular to the light input/output direction, respectively. 2. The method for measuring characteristics of an optical fiber according to claim 1, comprising a pair of combinations in which the entrance and exit ports are placed separately. 12. A set stage for setting both ends of the optical fiber to be measured on a carrier generally in parallel, and a plurality of measurement stages for measuring the characteristics of the optical fiber to be measured placed on the carrier that has been moved from the set stage. In an optical fiber characteristic measuring apparatus comprising a plurality of measurement stages, each of which has an optical measurement system entrance/exit opening arranged approximately parallel to each other, an optical fiber to be measured is connected to both ends of the optical fiber and the optical measurement system entrance/exit opening. In order to align the optical measuring system in the axial direction and the axial center, the optical measurement system entrance/exit port is placed on a means movable in the direction of light incidence/exit via a means movable in a direction perpendicular to the direction of incidence/exit of light. An apparatus for measuring characteristics of an optical fiber, wherein the set stage is equipped with automatic axial position detection means for the tips of both ends of the optical fiber to be measured with respect to the reference position of the carrier. 13. Claim 12, wherein the automatic axial position detection means for the tip of both ends of the optical fiber to be measured in the set stage with respect to the reference position of the carrier uses a photodiode.
The optical fiber characteristic measuring device described in 2. 14 The means movable in the light input/output direction includes means for automatically detecting the axial distance between the light input/output port and the reference position of the carrier when the carrier is on each of the measurement stages. An optical fiber characteristic measuring device according to claim 12, characterized in that: 15. The means for automatically detecting the axial distance between the light input/output port and the reference position of the carrier on the measurement stage is a sensor provided on the means movable in the light input/output direction. An optical fiber characteristic measuring device according to claim 14. 16. The optical fiber characteristic measuring device according to claim 12, wherein each of the optical measurement system entrance and exit ports is made of a measuring instrument photometric fiber. 17. The optical fiber characteristic measuring device according to claim 12, wherein each of the entrance and exit ports for the light from the light source includes a lens system. 18. Claim 16, wherein the means movable in the light input/output direction is a moving table, and the means movable in the direction perpendicular to the light input/output direction is a fiber holder. The optical fiber characteristic measuring device described in . 19. Claim 1, wherein the fiber holder is moved by the action of the optical measurement system to seek a point where light is passed through the optical fiber to be measured and the detected optical power is maximum. 18
The optical fiber characteristic measuring device described in 2. 20 A means movable in the light input/output direction for mounting the optical measurement system input/output port and a means disposed thereon movable in a direction perpendicular to the light input/output direction are arranged to accommodate the light input/output port, respectively. 13. The optical fiber characteristic measuring device according to claim 12, characterized in that the optical fiber characteristic measuring device is comprised of a pair of combinations so that the entrance and exit ports are placed separately.