JPH0364815B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a measuring device for measuring optical fiber characteristics.More specifically, the present invention relates to a measuring device for measuring optical fiber characteristics. The present invention relates to an apparatus for measuring optical fiber characteristics.

Prior art The measurement items necessary for inspection of optical fibers include the mechanical structure such as the outer diameter of the fiber, core diameter, its noncircularity, eccentricity, and mode field diameter, and fiber parameters such as refractive index distribution. There are transmission characteristics represented by optical loss, transmission band, etc. Among these, for example, optical loss and transmission band are especially important when designing a transmission path.

Regarding optical loss, there are two methods: the transmission method, which directly measures the amount of attenuation of light propagating in the optical fiber under test, and the backscattering method, which measures the amount of attenuation of Rayleigh backscattered light generated in the fiber. Typical examples include the sweep method, which evaluates in the frequency domain, and the pulse method, which evaluates in the time domain. In either case, for measurement, it is necessary to connect the end of the optical fiber to be measured to an output port for transmitting light from a light source on the measuring instrument side and an input port for transmitting light to a photodetector.

FIG. 2 is a schematic configuration diagram illustrating the configuration of a conventional optical fiber characteristic measuring device using a transmission method.

In FIG. 2, alignment blocks 1A to 1C and 2A
~2C are both ends 3, 4 of the optical fiber to be measured
holding both ends of the optical fibers 5A to 5C and 6A to 6C on the measuring instrument side,
And align yourself. Those measuring instrument side optical fibers 5A~
One end of 5C and 6A to 6C is connected to holder 7A.
~7C and 8A~8C, and the other ends of the measuring instrument side optical fibers 5A~5C are connected to the photodetectors 7'A~7'C, and the measuring instrument side optical fibers 6A~6C are connected to the photodetectors 7'A~7'C. The other end is connected to light sources 8'A to 8'C. These are usually assembled into a surface plate (not shown) to form a unit. Note that reference number 9 indicates a bobbin around which the optical fiber to be measured is wound.

The conventional device described above is used to perform measurements as follows.

That is, first, after processing both ends of the optical fiber to be measured (removal of coating and cutting of the fiber), it is set on the alignment tables 1A and 2A. Next, the end faces of both ends 3 and 4 of the optical fiber to be measured are placed in the holder 7A.
and measurement side optical fiber 5 set to 8A.
Align it with the end faces of A and 6A and adjust the axis. This adjustment is performed by slightly displacing the optical fiber under test in its axial direction, that is, in the Z direction, by means of an alignment device (not shown) provided in the alignment tables 1A and 2A, and also moving the optical fiber under test into its position. This adjustment, which is performed by making minute displacements in two mutually orthogonal directions perpendicular to the axial direction, ie, the XY directions, may be performed, for example, with a commercially available XYZ three-direction fine movement table, or it may be performed automatically. When the adjustment is completed, the light from the light source 8'A is input to the optical fiber to be measured, and the light propagated through the optical fiber to be measured is measured by the photodetector 7'A.
In this way, one measurement item, for example, transmission loss, is measured at the station, and then the operator manually transfers the bobbin 9 and performs the same operation at the station to sequentially measure other items. .

In the conventional apparatus described above, the optical fiber to be measured must be replaced and reconnected each time one measurement of one item is completed, and the connection between the optical fibers must be highly accurate. The problem was that it was very labor intensive.

In addition, the geometric structure is usually measured by observation using a measuring television.
It is necessary to position the fiber to be measured with high precision with respect to the optical system of the television. Optical fiber diameter
The fiber is very thin, around 100 μm, and in order to accurately measure this geometric structure, it is necessary to use high magnification. Must be positioned within field of view.

Therefore, there is a problem in that measurement of transmission characteristics requires as much effort as or more effort than connecting fibers.

Therefore, the applicant of the present invention proposed a continuous optical fiber characteristic measuring device that eliminates the need for positioning the optical fiber at each station in Japanese Patent Application Laid-Open No. 60-225044.

What is particularly difficult in such an apparatus for measuring optical fiber properties is the positioning of the fiber end in the axial direction of the fiber at a so-called setting station. Regarding fixation on the carrier in the direction perpendicular to the fiber axis, for example, a method of fixing the vicinity of the fiber end onto a V-groove is already known, and is currently widely used because positioning can be done relatively reliably.

Furthermore, when it comes to precise positioning, the light enters the fiber to be measured from one end, and while monitoring the optical power output from the other end, the fiber end and the optical measurement system There is a method of performing accurate positioning by relatively finely adjusting the positional relationship between the mouth and the fiber axis in the direction perpendicular to the fiber axis. This is because the optical power takes a maximum value when the input/output port and the fiber to be measured are in a state where their axes are aligned most optimally for measurement.

Regarding fixation on the carrier in the fiber axial direction, since the fiber end face is the light entrance/exit opening, applying direct mechanical restraint to it cannot block the light opening. Also, the method of determining the position by hitting a stopper or the like is not appropriate.

One of the reasons for this is that when positioning using a stopper, positioning errors become large due to backlash in the stopper, backlash and elastic deformation of the fiber itself and the parts that support the fiber, and secondly, the positioning error of the stopper becomes large due to backlash and elastic deformation of the fiber itself and the parts that support the fiber. One problem is that it is not possible to obtain a fiber end face that is clean enough to be used for measurement. This is because there is a high possibility that dust will adhere to the end face of the fiber due to contact with the stopper, and the end face of the fiber will be damaged due to contact.

Regarding precise positioning in the fiber axial direction, if the relative distance of the fiber end face to the input/output end of the optical system is increased or decreased, the power of the light passing through the fiber will increase or decrease; Since the optical power is at its maximum when it comes into contact with the exit port, it can be said that it is impossible to actually monitor the optical power and perform positioning.

To solve this problem, we used an optical sensor that accurately detects the position of the fiber end while keeping it clean using a non-contact method. Methods have been devised to detect and perform measurements using the detected signals.

These sensors use a lens system to form an image of the fiber to be measured on an image sensor and detect the end face image of the fiber under test, or a so-called TV camera type sensor that focuses the light beam of a transmissive photoelectric switch into a thin beam. These include devices that detect the presence of fibers.

Generally, in order to accurately detect the fiber position, it is necessary to increase the resolution of the sensor or the detection system including the sensor, and the field of view becomes narrower accordingly, making it difficult to locate and detect the fiber end position from a wide range. Incidentally, in a sensor using an optical lens system and an image sensor, a sensor with a resolution of about 0.5 μm usually has a field of view of only about 200 μm.

In the method using the photoelectric switch,
In order to detect the position of the fiber end with an accuracy of about 1 μm, the position of the sensor and the fiber end is slowly moved relative to each other with a resolution of about 0.5 μm. In order to perform good detection from the viewpoint of time constraints and maintaining the mechanical accuracy of relative movement, it is desirable that the positional deviation between the center of the sensor's field of view and the fiber end be about 200 μm or less.

To achieve this level of accuracy, the fiber end must be carefully set in line with the markings that indicate the set position at the set station, or a sensor equivalent to the one described above for detecting the fiber end position must be installed. At the station, there is no choice but to install the fibers redundantly and set the fiber ends while detecting the fiber end positions, which requires a great deal of labor and time.

Problems to be Solved by the Invention As described above, in the conventional optical fiber characteristic measuring device, the optical fiber to be measured is fixed at a predetermined position on the measuring device, and this is connected to the entrance of the optical measurement system. It took a lot of effort and time to do so.

In general, the measurement items required for inspection of optical fibers include the fiber's outer diameter, core diameter, and its noncircularity.
There are geometric structures such as eccentricity and mode field diameter, fiber parameters such as refractive index distribution, and transmission characteristics such as optical loss and transmission band.

In a characteristic measuring device that sequentially measures optical fiber characteristics over many items, if the optical fiber position accuracy at the set station is insufficient, the position of the optical fiber under test must be repeated at each measurement station. However, the labor and time involved further increased, and it was not possible to fully meet the demands for higher precision and higher efficiency of inspection.

SUMMARY OF THE INVENTION Therefore, the present invention provides an optical fiber characteristic measuring device that sequentially measures the above-mentioned characteristics of an optical fiber in a highly accurate and efficient manner by simply setting the optical fiber to be measured on the measuring device once. This is what I am trying to do.

Means for Solving the Problems According to the present invention, as shown in FIG.
Set station A for setting 14 and 16
and measurement stations B and C, which have optical measurement system input and output ends 30A and 32A and measure the characteristics of the optical fiber to be measured on the carrier, are sequentially provided along the carrier movement direction 28. ,
The optical fiber to be measured set on the carrier is sequentially moved along with the carrier to each measurement station, and at each measurement station, the end of the optical fiber to be measured is positioned with respect to the input/output end of the optical measurement system to obtain a predetermined characteristic. In the optical fiber characteristic measuring device that performs measurements, the set station A includes a monitoring device 8 with a shallow depth of focus that monitors the cut end face of the optical fiber to be measured.
There is provided an optical fiber characteristic measuring device characterized in that the optical fiber has an optical fiber characteristic of 0.0.81.

Operation The apparatus for measuring optical fiber characteristics according to the present invention as described above includes a set station A as a basic component, as shown in FIG.

Both ends 14 and 16 of the optical fiber to be measured are held in predetermined positions on the carrier 18 by holders 20 and 22. The set station A is equipped with monitoring devices 80 and 81 having a shallow depth of focus for monitoring the end face of the optical fiber to be measured. monitoring device 80,
81, both ends 14 and 16 of the fiber to be measured are set at predetermined positions in a plane perpendicular to the fiber axis.

The optical fiber to be measured, which has been set as described above, is moved to each measurement station (not shown) while being held in position on the carrier 18 by the holders 20 and 22, and measurements are performed at each measurement station.

As described above, in the optical fiber characteristic measuring device according to the present invention, the optical fiber end is exposed to the monitoring device while observing the end of the optical fiber to be measured by the monitoring device having a shallow depth of focus at the set station A. Move the fiber in the axial direction. the result,
When the end of the optical fiber is in focus and can be clearly observed, it means that the end of the optical fiber is located within a shallow depth of focus range, and as a result, positioning in the axial direction can be performed. In this way, once the optical fiber to be measured is set on the carrier at the set station A, all that is required is to send the carrier along with the axial position information of the end of the optical fiber to be measured to each measuring station in sequence, and the optical fiber for many items can be measured. Measurements of fiber properties will be made.

Embodiments Hereinafter, embodiments of the optical fiber characteristic measuring device according to the present invention will be described with reference to the accompanying drawings.

FIG. 3 is a diagram showing the configuration of one embodiment of an optical fiber characteristic measuring apparatus according to the present invention. The characteristic measuring apparatus is composed of a set station A, a fiber axial position detection station A', and, for example, four measurement stations B to E. The optical fiber to be measured is set on a movable table 10 at the set station A.

At the rear of the moving table 10, a bobbin 12 of the optical fiber to be measured is loaded onto a cart by a method not shown. and is held in holders 20 and 22 provided on the carrier 18. The above-mentioned attachment to the holder is performed when the movable table is at the set station A.

Set station A includes monitoring devices 80 and 8 that monitor the end face of the fiber to be measured, which is the light input and output end.
1 at the front end of the fiber in the axial direction. The monitoring devices 80 and 81 each include, for example, an imaging optical system with an extremely shallow depth of focus, an imaging device, and an electrical system that processes signals from the imaging device. In this case, it is preferable to attach a monitor display to the monitoring device.

The fiber axial position detection station A' has almost the same configuration as the set station A, but instead of the monitoring devices 80 and 81, it is equipped with non-contact sensors 24 and 26 which have a narrow measurement range but high resolution.

A light source 30 and a photodetector 32 are arranged in each measurement station B to E, and optical fibers 30A and 32A extending from the light source 30 and the photodetector 32 are
It is held by holders 30B and 32B. Holders 30B and 32B hold optical fibers 30A and 32
A distance between the holders 20 and 22 of the carrier 18
Both ends 14 of the optical fiber to be measured are held in
and 16, and the end faces of the optical fibers 30A and 32A are positioned in the same plane.

The optical fiber characteristic measuring device configured as described above operates as follows.

First, both ends 14 and 16 of the optical fiber to be measured are
is held by holders 20 and 22 on carrier 18. Monitoring devices 80 and 81 monitor the optical fiber end from the front in the axial direction, and check the cleanliness such as the cutting angle, the state of chipping, and the presence or absence of dust. The end face condition is checked, and position information of the optical fiber end in the direction perpendicular to the fiber axis is obtained.
It is confirmed whether it is set at a predetermined position on the holders 20, 22. At that time, when the optical fiber end is not in focus, the optical fiber end is displaced in the axial direction on the holder, and when the optical fiber end is in focus, it is held still and fixed with the holder. Such out-of-focus and out-of-focus can be fully visually observed on a monitor display.

The optical fiber to be measured set as described above is moved to the next fiber axial position detection station A' while its position on the carrier 18 is maintained by the holders 20 and 22. The carrier 18 is positioned at a predetermined position, and the axial position of the fiber end is read by non-contact sensors 24 and 26, which have a narrow measurement range but high resolution. For example, the measurement range is □
A measurement television with a size of 200 μm×200 μm and a resolution of 02 μm can be used as the position sensor.

The optical fiber to be measured, whose position has been measured, moves in the direction of arrow 28 while being held in position on carrier 18 by holders 20 and 22, and stops at each of measurement stations B to E.

In each measurement stage B to E, each movable stage 10, that is, each carrier 18, is positioned at a fixed position, and rough axis alignment between the ends 14 and 16 of the optical fiber to be measured and the measuring instrument side optical fibers 30A and 32A is performed. Next, the fiber axial position detection station
Based on the position information read at A', the measuring instrument side optical fiber holders 30B and 32B are moved in the optical fiber axial direction to position the fiber ends 14 and 16 at the positions required for measurement.

Next, the optical fiber holders 30B and 3 on the measuring instrument side are set so that the amount of light received by the photodetector 32 from the light source 30 via the optical fiber to be measured is maximized.
2B is aligned by slightly moving it in two mutually perpendicular directions located in a plane perpendicular to the axis of the optical fiber. Note that at this time, the holders 20 and 22 may be moved.

When alignment is completed, each measurement station measures the characteristic assigned to that measurement station, and when the measurement of that characteristic is completed, the measurement is sequentially sent to the next measurement station. In this way, when all measurements are completed, the optical fiber to be measured is removed from the moving table 10, and the optical fiber to be measured is removed from the moving table 10.
0 is returned to set station A, and the next optical fiber to be measured is set.

Since the above-mentioned monitoring device has a shallow depth of focus, when monitoring the above-mentioned end face condition and setting condition using signals from the monitoring device, it is necessary to perform the setting operation so that the end of the optical fiber can be seen most clearly. , the fiber end can be set within a sufficiently narrow range for the monitoring device.

Depth of focus refers to the positional range in the direction perpendicular to the optical axis in which the object to be monitored is in focus, and when it comes to lens systems, it generally depends on various factors including human image recognition ability, etc. It is determined mainly by parameters such as the numerical aperture and magnification of the lens. Therefore,
By appropriately selecting the above parameters of the lens, the depth of focus required for positioning the end of the optical fiber can be selected.

It can be said that reducing the depth of focus in the monitoring system is operationally reasonable considering the monitoring work performed.

Therefore, if each carrier 18 is positioned at a fixed position with respect to the monitoring devices 80 and 81 at the set station A, the position of the fiber end on each carrier 18 is determined for each carrier 18 in the range of its focal depth. can be kept constant.

In this example, after the end of the optical fiber to be measured is positioned at a fixed position on the holder at the set station A, the end of the optical fiber to be measured is positioned again at the measurement station based on the position information of the end of the optical fiber to be measured detected by the fiber axial position detection station A'. Although we have shown an example in which this is done, this can be omitted if the depth of focus of the monitoring device is made very shallow. For example, the fiber to be measured and the fiber on the measuring instrument side have a core diameter of 50 μm.
When measuring transmission characteristics, if the overall depth of focus of the monitoring device is 20 μm or less and the carrier positioning accuracy is extremely high, the fiber axial position detection station A' and measurement stations B to E Even if re-detection and re-positioning were omitted, measurement results with sufficient accuracy were obtained.

Further, in this embodiment, the setting work is expressed as being performed by a human, but the same effect can be obtained by using a machine such as a robot. in this case,
In the same way as humans do, positioning using the depth of focus of the optical system is performed by image recognition, such as the sharpness of the fiber end image, using image recognition methods used in general autofocus devices. Just go.

Further, in this embodiment, the explanation has been limited to four measurement stations B to E, but the number of measurement stations can be arbitrarily set in accordance with the number of inspection items.

Effects of the Invention As is clear from the above description, the optical fiber characteristic measuring device according to the present invention can sequentially measure various characteristics of an optical fiber by simply setting the optical fiber to be measured on the measuring device once. Execute with high precision and efficiency. The device for measuring optical fiber properties according to the invention can therefore be used over a wide range of applications.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the basic configuration of an optical fiber characteristic measuring device according to the present invention. Figure 2 shows
1 is a schematic configuration diagram illustrating the configuration of an optical fiber characteristic measuring device using a conventional transmission method. FIG. 3 is a schematic diagram showing the configuration of an optical fiber characteristic measuring device implementing the present invention. Main reference number: A...Set station;
A′...Fiber axial position detection station,
B, C, D, E...Measurement station, 1A~1
C, 2A to 2C... Optical fiber holder to be measured,
3, 4... end of optical fiber to be measured, 7A~7
C, 8A to 8C...Measuring instrument side fiber holder,
7'A to 7'C...Photodetector, 8'A to 8'C...Light source, 9...Optical fiber bobbin to be measured, 10...Moving table, 12...Bobbin, 14, 16...To be measured Optical fiber, 18...Carrier, 20, 22, 30
B, 32B...Holder, 24, 26...Non-contact sensor, 30...Light source, 32...Photodetector, 8
0,81...Monitoring device.

Claims (1)

[Scope of Claims] 1. A setting station for setting an optical fiber to be measured on a carrier, and a measuring station for measuring the characteristics of the optical fiber to be measured on the carrier, having an input/output end of an optical measurement system, The optical fibers to be measured are sequentially provided along the moving direction of the carriers, and the optical fibers to be measured set on the carriers are sequentially moved together with the carriers to the respective measurement stations, and are connected to the input/output ends of the optical measurement system at each measurement station. On the other hand, in an optical fiber characteristic measuring apparatus for positioning the end of an optical fiber to be measured and performing predetermined characteristic measurements, the set station is equipped with a monitoring device having a shallow depth of focus for monitoring the cut end face of the optical fiber to be measured. A device for measuring optical fiber characteristics. 2 The depth of focus of the optical system of the monitoring device is 20 μm.
Claim 1 characterized in that:
An apparatus for measuring optical fiber characteristics as described in .