JPH10332530A - Otdr device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To clearly display such failure as the level difference in a reception light waveform even in a small print space. SOLUTION: Data obtained in the order of sampling from an averaging processing circuit 23 are sent to a printer 28 via a data-processing circuit 26 and a printer control circuit 27. In the data-processing circuit 26 and the printer control circuit 27, first a specific number of data are taken out in the order of sampling at a time, a value that is obtained by adding a specific value to data that are sampled latest out of data being taken out is subtracted from each data, further a position where data after processing are in ordinate direction is converted to a position signal that indicates the position in the ordinate direction in terms of the order of sampling, and then is converted to a command for drawing a straight line for connecting the positions successively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an OTDR device for measuring light returning to an incident end side when an optical pulse is incident on one end of an optical fiber to be measured.

[0002]

2. Description of the Related Art OTDR (Optical Time)
Domain Reflectometer)
An optical pulse is incident on one end of an optical fiber to be measured and propagates through the optical fiber. Then, if there are break points or obstacles in the optical fiber, they cause Fresnel reflection,
Alternatively, when there is a non-uniform distribution of the refractive index of the core of the optical fiber, the propagating light is scattered, and a part of the light returns to the incident end side. Therefore, utilizing the fact that the time difference from the incident point of the light pulse to the arrival time of the returning light corresponds to the distance to the reflection point or the scattering point, the intensity of the returned light is determined for a certain period of time from the light pulse incidence. If sampling is performed every time, the light intensity data indicates the state of the measured optical fiber at a position corresponding to the sampling time,
It is possible to determine the position of the break point and to specify a defective portion having a large loss.

In a conventional OTDR device, all the received light intensity data (for example, data of 15000 points) obtained by one optical fiber under test are arranged in the sampling order as they are,
The information is displayed on an RT display device and output by a printer. That is, each data is plotted with the horizontal axis representing distance (sampling order) and the vertical axis representing received light intensity (dB), and a graph connecting them with a straight line is output.

[0004] Even if the optical fiber to be measured is normal, a certain amount of backscattered light is generated and it has a certain uniform transmission loss characteristic. Therefore, in a normal optical fiber without any abnormality, the received light intensity is time (distance). ), The light reception waveform graph becomes linear with a constant slope, and the slope indicates a loss per unit length. On the other hand, if there is a locally large loss portion in the optical fiber to be measured, a stair-like step or undulation is generated in the received light waveform graph correspondingly. Therefore, in manufacturing, laying, and maintaining the optical fiber, it is possible to find a defective portion or an abnormal portion of the optical fiber cable by observing a received light waveform graph displayed on a display screen or output to a printer. .

[0005]

However, the conventional OTDR apparatus has a problem in that it is difficult to identify a defective portion of the optical fiber to be measured. That is, the optical fiber to be measured often has a length of about 100 km, and a large amount of data (about 15,000 points) corresponding thereto is displayed on paper or a screen as it is. Since it is only minutely expressed, it is difficult to find a part where an abnormality has occurred or to specify the part. Further, the average loss value per km cannot be read at a glance from the slope of the received light waveform graph.

Of course, the distance scale on the horizontal axis is increased (the distance per scale is reduced) and the dB scale on the vertical axis is increased (d per scale).
If the B value is reduced), printing on very large paper will make the waveform steps and the like of abnormal portions appear large, which makes observation easier. However, a printer that can print on large paper and large paper is required. Problem arises.
Even in such a case, the average loss value per km cannot be read at a glance, and the calculation of the inclination by reading the vertical and horizontal scales of the graph one by one is not improved.

Further, an automatic judgment technique using a computer without relying on observation by human eyes has been considered. However, since noise and the like increase as the distance increases from the incident end, it is not always necessary to make an automatic judgment accurately. There is a side that cannot rely on human observation.

In view of the above, it is a first object of the present invention to provide an OTDR apparatus improved so that an abnormality such as a step in a received light waveform can be clearly displayed even in a small print space.

It is a second object of the present invention to provide an OTDR apparatus in which the average loss value per unit length can be determined at a glance from a received light waveform, and the quality can be easily determined.

[0010]

According to the first aspect of the present invention, there is provided an optical pulse input means for inputting an optical pulse to one end of an optical fiber to be measured. Light-receiving means to which the light returned to one end of the optical fiber and emitted therefrom is guided; data sampling means for sampling the output of the light-receiving means at regular intervals from the time of the light pulse incidence to obtain light-receiving intensity data; Means for extracting data by a predetermined number in the order of sampling, means for subtracting a value obtained by adding a predetermined value to the last sampled data from the extracted number of data from each data, and a value after the subtraction Represents the position on one coordinate axis, and the time to the sampling of each data represents the position on the other coordinate axis, and sequentially connects the positions determined by these. Means for converting the instruction to draw a line, that the print means to print on each data by a predetermined number described above can be provided is a feature in accordance with the drawing command.

A predetermined number of samples are extracted from all data in the order of sampling, and a value obtained by adding a predetermined value to the last sampled data of the extracted predetermined number of data is subtracted from each data. Prints the position on one coordinate axis and the time until the sampling of each data represents the position on the other coordinate axis, and converts it to a command to draw a straight line connecting the positions determined by these in order. So
By dividing in the distance direction, it is enlarged and printed in the distance direction, and also enlarged in the direction of the received light intensity so that only the portion where the waveform graph appears is enlarged. It is possible to easily determine the abnormal portion by printing.

In order to achieve the objects of the first and second aspects of the present invention, according to the second aspect of the present invention, an optical pulse inputting means for inputting an optical pulse to one end of an optical fiber to be measured; A light receiving means to which the light returned to one end and emitted is guided; a data sampling means for sampling the output of the light receiving means at regular intervals from the time of the light pulse incidence to obtain received light intensity data; Means for obtaining an average loss value per unit length of the measurement optical fiber, and means for correcting a loss value corresponding to the time at which the data was sampled from the average loss value obtained by adding the data to each data, The corrected value represents the position on one coordinate axis, and the time until the sampling of each data represents the position on the other coordinate axis. Means for converting the instruction to draw a straight line connecting the a printing means for printing that is provided has a feature in accordance with the drawing command.

According to the second aspect of the present invention, the portion having the average loss value of the graph of the waveform to be printed appears parallel to the distance direction, so that the print space can be further reduced. Further, if the waveform graph is shifted from the above parallel direction, it can be easily determined whether the loss is larger or smaller than the average loss value depending on which side the waveform graph is shifted. When the waveform graph deviates from the parallel direction, by reading the deviation amount per scale, it is immediately apparent how much the loss value is larger or smaller than the average loss value.

In order to achieve the objects of the first and second aspects of the present invention, the third aspect of the present invention is characterized in that a standard value relating to loss is used in place of the average loss value of the second aspect of the invention. It has become.

According to the third aspect of the present invention, the portion having the loss value as specified in the standard is represented by the waveform graph parallel to the distance direction, so that the print space can be further reduced. Also, if the waveform graph is shifted from the above parallel direction, it can be determined whether the loss is larger or smaller than the standard loss value depending on which side it is shifted, and according to the direction of inclination, it is equal to or higher than the standard. And a defective portion below the standard can be easily determined. When the waveform graph is displaced from the above parallel direction, by reading the amount of displacement per scale, it is immediately apparent how much the loss value is larger or smaller than the standard loss value.

[0016]

Next, embodiments of the present invention will be described in detail with reference to the drawings. In FIG. 1, a pulse signal generated from a pulse generator 11 is sent to a laser generator 12. The laser generator 12 is composed of, for example, a semiconductor laser and its driving circuit, generates a pulsed laser beam (for example, a wavelength of 1.55 μm) according to the input pulse signal, and converts this optical pulse into an optical fiber coupler or the like. Through the optical directional coupler 13 and the optical connector 14, and enters one end of the optical fiber 15 to be measured.

The optical pulse incident on one end of the optical fiber 15 to be measured propagates through the optical fiber 15 and causes scattering or reflection. The scattered light and reflected light return to the incident end side of the optical fiber 15 and exit. The emitted light is guided to the light receiver 21 via the optical connector 14 and the optical directional coupler 13. The light receiver 21 includes a light receiving element such as an avalanche photodiode, an amplifier circuit for amplifying the output of the light receiving element, and sends a light receiving signal to the A / D converter 22.

The A / D converter 22 operates in synchronization with the pulse signal sent from the pulse generator 11 described above. In other words, the operation of sampling the light receiving signal and converting it into digital data at a fixed cycle from the time when a certain time has elapsed from the pulse signal is started. In this way, data on the received light intensity is obtained for each delay time from the light pulse incidence. For example, if sampling is performed 15,000 times, data is obtained for each of the 15000 delay times. Since this delay time corresponds to the time that light travels back and forth from the incident end to the reflection point, light reception intensity data for each distance corresponding to the sampling period has been obtained. Here, the sampling period (distance resolution is about 6.67 m) is set so that 15,000 data points can be obtained for the measured optical fiber 15 having a length of 100 km.

This light pulse incident / light receiving intensity data collection is repeated many times, and the averaging circuit 23 calculates the average value of the data for each sampling (distance), thereby eliminating the influence of noise.

The data for each sampling obtained in this way is sent to a CRT display device 25 via a display circuit 24 and displayed. That is, for example, by plotting the data sampling order on the horizontal axis and the data value on the vertical axis as shown in FIG. 5, the horizontal axis is the length direction of the measured optical fiber 15, and the vertical axis is the received light intensity (dB). ) Is displayed.

In this graph, A represents the reflection at the optical connector 14 at the start terminal of the optical fiber 15 to be measured, and E represents the reflection at the end terminal. A straight line descending to the right generally occurs between the points A to E, and its slope corresponds to the average loss. If there is an abnormal portion such as a portion where the loss is locally increased, a step or undulation is generated accordingly, as in b, c, d.

Assuming that the length of the optical fiber 15 to be measured is, for example, 90 km, data for 90 km is arranged in the horizontal axis direction. (The original number of data is not displayed because all data are thinned or averaged.)
It becomes big.

Further, since all data for 90 km is displayed, the dB value of one scale of the received light intensity is as large as 5 dB. That is, in the example of FIG. 5, since the received light intensity difference from the start terminal A to the end terminal E of the optical fiber 15 to be measured is 18.6 dB, it is necessary to set 1 to display this.
It is necessary to increase the dB value of the scale.

For this reason, the distance direction on the horizontal axis and the received light intensity direction on the vertical axis are very finely displayed, so that the steps B, C, and D of the abnormal part can be found, and the positions of the steps B, C, and D can be found. It is very difficult to read (distance).

Therefore, here, when printing the received light waveform data, the difficulty of reading is eliminated in the following manner. That is, the data obtained from the averaging processing circuit 23 is sent to the data processing circuit 26, subjected to predetermined processing, sent to the printer control circuit 27, and converted into a print command to control the printer 28. In the data processing circuit 26 and the printer control circuit 27, processing as shown in the flowchart of FIG. 2 is performed.

First, in the first step 31, data output from the averaging circuit 23 is extracted by a predetermined number in the output order (sampling order). That is, assuming that the total number of data is n, (1 + 0.1) × (n / k) pieces are extracted in the sampling order. Here, k is the number of divisions. The reason why the amount is increased by 0.1 (10%) is to overlap and print so as not to lose the information on the ends of the divided graph. From number 1 (1 + 0.1)
The data up to x (n / k) is first extracted, and then {1 × (n / k) +1} to {(2 + 0.1) × (n
/ K) data up to the number #, and then {2 × (n
/ K) +1} to {(3 + 0.1) × (n / k)}.

In the next step 32, a predetermined value is uniformly subtracted from each of the extracted data. The value to be subtracted is a value obtained by adding a predetermined value to the latest sampled data among the extracted data. And
The data after this processing is converted into a position signal in step 33. That is, the sampling order is converted into a signal indicating the position in the horizontal axis direction, and the value of the processed data is converted into a signal indicating the position in the vertical axis direction. Then, step 3
In step 4, the command is converted into a command for drawing a straight line that sequentially connects the positions specified by the position signals.

As a result, (a), (b), and (b) of FIG.
As shown in (c), (d), and (e), it is possible to obtain a print result indicating each of the five divided graphs. That is, in this case, printing is performed by dividing into five (k = 5), and since the number of data is 15000, 3300 pieces are sequentially taken out. This means that 1 km to 23 km, 21 km to 43 km in the distance direction.
km, 41 km to 63 km, 61 km to 83 km, 81
It means that it is divided like km to 103 km.
The prints that overlap by 10% are
This is to prevent a step or the like at the time of division from being overlooked.
Therefore, in each divided print, one scale in the horizontal axis direction is set to 2k.
m and can be enlarged and displayed.

In each of the divided prints, the graph appears in the vertical axis direction without excess or deficiency (around the center without protruding). That is, a value obtained by adding a predetermined value to the value of the data in the latest order (which should be the smallest value) among the data extracted by a predetermined number is subtracted from each data. It is. The received light intensity (dB) in the vertical axis direction can also be enlarged and displayed as one scale 1 dB.

Therefore, the print is enlarged and enlarged in both the distance direction (horizontal axis direction) and the light receiving intensity direction (vertical axis direction) by such divided printing.
C and D are also shown in an enlarged manner, so that they can be easily found. Further, since the image is divided in the distance direction and the received light intensity direction and only the portion near the portion where the waveform appears is printed, there is no need to print on a large sheet of paper.

The data processing circuit 26 and the printer control circuit 27 may perform the processing shown in FIG. As shown in the flowchart of FIG. 3, first, in step 41, an average loss value per unit length (km) over the entire length is calculated from all data. This is equivalent to obtaining the average value of the slope of the graph. In the next step 42, each data is corrected using the average loss value per unit length so that the graph becomes horizontal. That is, when correcting certain data, a value obtained by multiplying the distance corresponding to the time at which the data was sampled by the average loss value is obtained, and this is used as a correction value, and this correction value is added to the data. Do this for all data.

Thereafter, at step 43, a predetermined value is subtracted from each data. Thereafter, at step 44, a predetermined number of pieces of data are extracted in the order of sampling. As described above, when the total number of data is n and the number of divisions is k,
(1 + 0.1) × (n / k) pieces. Then, in step 45, the sampling order is converted into a signal indicating the position in the horizontal axis direction, and the value of the processed data is converted into a signal indicating the position in the vertical axis direction.
In step 6, the command is converted into a command for drawing a straight line that sequentially connects the positions specified by the position signals.

When such a process is performed, 5
It is divided and printed, but FIG. 7 (a), (b),
As shown in (c), (d), and (e), printing is performed so that the slope corresponding to the average loss value is horizontal. Therefore, since the print is enlarged in both the distance direction and the light receiving intensity direction, the steps R to D can be easily identified, and the deviation from the average loss value can be easily recognized. In other words, if the graph is declining to the right, it is the part having a loss value per unit length larger than the average loss value, and if it is declining to the right, the loss value per unit length is smaller than the average loss value. It is easy to find out which part you have. In addition, by reading the vertical displacement per graduation on the horizontal axis, the inclination, that is, the loss value can be immediately recognized, and troublesome calculations and the like become unnecessary.

In this case, since the waveform graph is almost horizontal, the printing space does not need to be large in the vertical direction, so that more resources can be used, such as the use of narrow paper in the vertical direction. Waste prevention can be achieved. Further, if all the data is converted into position signals related to the same coordinates without dividing the data by omitting the above step 44, printing can be performed even with a pen recorder using long paper such as roll paper. It becomes possible.

Instead of using this average loss value, FIG.
If you process using standardized loss values like
It is easy to determine that the value is out of the standard loss value and how much the loss value is. In the flowchart of FIG. 4, in step 51, the standard loss value (for example, 0.2
5 dB / km), and for each data, a value obtained by multiplying a distance corresponding to the time at which the data was sampled by a loss value of the standard is obtained, and this is used as a correction value, and this correction value is added to the data. To correct.

Next, at step 52, a predetermined value is subtracted from each data. After that, at step 53, all the processed data are converted into position signals relating to the same coordinates. Convert to In this case, a pen recorder that uses long paper such as roll paper is used as the printer 28.

As a result, a waveform graph can be printed on a long sheet of paper as shown in FIG. If it has the specified loss value, it will be printed as a horizontal waveform.
Therefore, it is not necessary to increase the print space in the vertical axis direction. If the waveform graph rises to the right, the loss is lower than the standard value, and if it falls to the right, the loss is higher than the standard value. For example, in FIG. 8, the horizontal sections A and E have the loss value as specified, the sections B and D that rise to the right have slightly better loss characteristics, and the sections C that decrease to the right. It can be seen at a glance that the loss characteristics are worse than the standard values.

Therefore, it is easy to judge that the loss value per unit length is out of order and how much the loss value is, and the pass / fail judgment can be made easily. Therefore, it is particularly suitable for an inspection in which a non-defective part and a defective part at the time of manufacturing an optical fiber are identified and a part determined as a defective part is removed.

The above description relates to one embodiment, and it goes without saying that the present invention is not intended to be limited to these descriptions. For example, in the above description, the processing as shown in FIGS. 2 to 4 is performed by the data processing circuit 26 and the printer control circuit 27. However, instead of using such hardware, software using a general-purpose computer is used. It can also be processed. The processing flow at that time may be basically as shown in FIGS. 2 to 4, but the order of the processing and the like can be changed. In addition, the specific configuration and the like can be variously changed.

[0040]

As described above, the OTD of the present invention is
According to the R device, the abnormal portion of the waveform graph can be enlarged and displayed without requiring a large print space, and the abnormal portion can be easily found, and the loss value per unit length can be read. It is easy to determine that the loss value deviates from the standard value.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is an exemplary flowchart showing the flow of processing in the embodiment.

FIG. 3 is a flowchart showing the flow of another process.

FIG. 4 is a flowchart showing the flow of still another process.

FIG. 5 is a view showing a display example of a CRT display screen.

FIG. 6 is a view showing a print example by the processing of FIG. 2;

FIG. 7 is a view showing a print example by the processing of FIG. 3;

FIG. 8 is a view showing a print example by the processing of FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Pulse generator 12 Laser generator 13 Optical directional coupler 14 Optical connector 15 Optical fiber to be measured 21 Optical receiver 22 A / D converter 23 Averaging processing circuit 24 Display circuit 25 CRT display device 26 Data processing circuit 27 Printer control Circuit 28 printer

Claims (3)

[Claims] 1. An optical pulse inputting means for inputting an optical pulse to one end of an optical fiber to be measured, a light receiving means for guiding light emitted after returning to one end of the optical fiber, and an output of the light receiving means. A data sampling unit that obtains received light intensity data by sampling at regular time intervals from the time of incidence of the light pulse, a unit that extracts a predetermined number of the data in the order of sampling, and a data sampled last among the extracted predetermined number of data. The value obtained by adding the specified value to the
Means for subtracting from each data, and the value after the subtraction represents a position on one coordinate axis, and a time until sampling of each data represents a position on the other coordinate axis, respectively.
An OTDR apparatus comprising: means for converting into a command for drawing a straight line connecting the positions determined by these in order; and printing means for printing each of the predetermined number of data in accordance with the drawing command. 2. An optical pulse inputting means for inputting an optical pulse to one end of an optical fiber to be measured, a light receiving means for guiding light emitted after returning to one end of the optical fiber, and an output of the light receiving means. Data sampling means for sampling received light intensity data at regular intervals from the time of incidence of the light pulse, means for obtaining an average loss value per unit length of the measured optical fiber from the data, and data for each data. Means for obtaining a loss value corresponding to the time at which the data was sampled from the above average loss value, and adding the corrected value to the mean value. Means for converting the position on the coordinate axis into a command for drawing a straight line connecting the positions determined by the above in order, and printing in accordance with the drawing command. An OTDR device comprising: 3. The OT according to claim 2, wherein a standard value regarding loss is used instead of the average loss value.
DR device.