JPS63163139A - Light pulse tester - Google Patents

Abstract

PURPOSE:To dispense with all-time monitoring of a screen while eliminating variations in the accuracy of the results of measurement, by calculating and displaying the frequency and the time length of averaging until a specified S/N ratio is reached to automatically stop the averaging upon the reaching of the ratio. CONSTITUTION:When operation is started, the waveform of a back scattered light is displayed on a CRT, and so a specific position is assigned on a screen by a marker specifying means 12. At this point, as the means 12 outputs a specification signal S1, a detection means 13 detects the current S/N ratio at the specific position according to the signal S1 to output a detection signal S2. A ocmparator 14B compares the signal S2 with a set signal S3 to determine a difference between S/N ratios given by both the signals and sends a comparison signal S4 to a calculating section 15B, which calculates the frequency or time length of averaging necessary until the current S/N ratio reaches a set value, referring an S/N improve characteristic storing section 15A and outputs a calculation signal S5 to a display means 16 and a stop means 17. The means 16 displays the contents the signal S5. On the other hand, when the set S/N ratio is reached, the means 17 stops the averaging automatically on the basis of the signal S5.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention sends out a predetermined light pulse from a light emitting source, and detects the characteristics of the measured object by stimulating backscattered light reflected from the measured object. Regarding optical pulse tester.

[Prior art] With the spread of optical fibers, it has become possible to accurately evaluate the splice loss at the connection point of the optical fiber, the transmission loss of the optical fiber, and the location when the optical fiber breaks or cracks midway. Measuring instruments have come to play a very important role.

An optical pulse tester is a type of measuring instrument that evaluates the characteristics of such optical fibers. It injects a light pulse into the optical fiber and measures the amount of light that is scattered due to the non-uniformity of the refractive index that inherently exists in the core of the optical fiber. The amount of transmission loss is measured by using the so-called backscattered light that returns, and the distance to the fault point is measured by determining the time difference between the incident pulse and the Fresnel reflection that occurs at the fault point.

The configuration of a conventional optical pulse tester and its operating principle will be explained below.

FIG. 3 is a configuration diagram of a conventional optical pulse tester. In the figure, 1 is a processing unit (called a CPU) that controls one part of the overall control, 2 is a timing generation unit that generates a predetermined timing signal according to the control of f and II of the CPUI, and 3 is a timing signal output from the timing generation unit 2. 4 is a directional optical coupler that changes the direction of the light depending on the direction in which the light passes; 5 is the object of measurement. An optical fiber as an object to be measured, 6 a light receiving section that captures the backscattered light reflected and returned from the optical fiber 5, 7 an amplifier that amplifies the small amount of backscattered light captured by the light receiving section 6, 8
9 is an A/D converter that samples the backscattered light amplified by the amplifier 7 and converts it into a digital signal;
This is a display device (referred to as a CRT) that processes the backscattered light converted into a digital signal by the D converter 8 using a cput and displays the result as a waveform.

Here, the CPUI has an averaging section 11 inside that performs S/N improvement by averaging in order to detect backscattered light buried in noise.

Next, the operation will be explained.

When a timing signal is output from the timing generating section 2, a light emitting section 3 consisting of a laser diode or the like outputs a light pulse based on the timing signal.

The output optical pulses are input to an optical fiber 5 as an object to be measured via a directional coupler 4.

The backscattered light reflected and returned from the optical fiber 5 is input to the light receiving section 6 via the directional coupler 4 again.

The backscattered light generated by the light receiving section 6 is amplified by the amplification 37 and then inputted to the A/D conversion section 8 .

This A/D converter 8 samples the backscattered light at the sampling timing generated by the timing generator 2.
After performing the /D conversion, the optical signal of the backscattered light converted into a digital signal is output to the CPUI.

The CPU processes the backscattered light manually input from the A/D converter 8 using an internal averaging unit 11, etc.
The processed results are displayed on the RT9 as a waveform.

Figures 4(a) and 4(b) are diagrams showing an example of the waveform displayed on the cRT9J:. Figure 4(a) is a diagram showing the waveform when the number of averaging is small; b) is a diagram showing a waveform when the number of times of averaging is large.

As shown in the figure, the greater the number of averaging, the S
/N ratio is improved, and it becomes possible to detect optical signals of backscattered light buried in noise.

[Problems to be Solved by the Invention] By the way, in averaging in conventional optical pulse testers, the operator predetermines the number of times of averaging, and the average is performed only by this predetermined number of times, or the average is displayed on the CRTQ. The method is to stop and correct the averaging at an appropriate point while checking the degree of convergence of the waveform.

Therefore, if the number and time of averaging differ depending on the measurer, the S/N ratio of the waveform will differ, and as a result, there is a problem that the granularity of the 411 results will vary depending on the measurer.

Also, if the time required for aheraging is unknown, the measurer must always use CR7 on the optical pulse tester until the aheraging is stopped.
The problem of having to monitor the screen is a fuss.

This invention was made to solve the above problems, and it notifies the measurer of the number of times and time of averaging until a predetermined S/N ratio is reached, and also automatically stops averaging. This allows the measurer to always check CR7.
The aim is to obtain an optical pulse tester that does not require monitoring the screen.

Another object of the present invention is to obtain a pulse tester in which the S/N ratio is always constant, that is, the Ma1 constant particle size is constant, regardless of who is performing the measurement.

[Means for Solving the Problems] Therefore, the pulse tester according to the first invention includes a marker specifying means for specifying a specific position on the display screen by moving a marker, and a position specified by the marker specifying means. a first stage of comparison for comparing a predetermined S/N ratio set at the tth time with the S/N ratio detected by the detection means; S/
The present invention is characterized by comprising a calculation means for calculating a predetermined number of averaging times and time from the N conversion curve, and a stop L-L stage for stopping averaging according to the result calculated by the calculation means, and a second The optical pulse tester according to the invention includes a marker specifying means for specifying a specific position on a display screen by moving a marker, a detecting means for detecting the S/N ratio of the position specified by the marker specifying means, and f.
a comparison means for comparing a predetermined S/N ratio set for the above-mentioned purpose with the S/N ratio detected by the detection means, and a predetermined averaging number/time from the S/N correction curve based on the comparison result. , a stopping means for stopping the averaging according to the result calculated by the calculating means, and a display means for displaying the averaging according to the result calculated by the direct calculation means. It is a feature.

[Operation] When a specific position on the display screen is designated by the marker designation means, the detection means detects the S/N at this designated position.
Detect the ratio.

Here, when the comparing means compares the predetermined S/N ratio set in advance and the detected S/N ratio, the calculating means calculates the S/N ratio.
Calculate the number and time of averaging from the revised N curve.

The stopping means automatically stops averaging after a predetermined number of averaging times or a predetermined period of time according to the calculated result.

[Example] Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. In the figure, 12 is a marker specifying means for specifying a specific position on the display screen by moving a marker, and 13 is a position specified by the marker specifying means 12. ; Detection means for detecting the S/N ratio of δ; 14 is a comparison means for comparing a predetermined S/N ratio set at -t and the S/N ratio detected by the detection means 13; 15 is a comparison means for this; Calculation means for calculating a predetermined number of averaging times and time from the S/N improvement curve based on the comparison means 14; 16, display means for displaying the result on the display screen according to the result calculated by the calculation means 15; 17, calculation means A stop F means stops the averaging according to the result calculated by the means 15.

Here, the comparison means 14 is configured with a memory or the like in which a predetermined S/N ratio is set.
and a comparator 14 that compares the predetermined S/N ratio set in this setting i14A with the S/N ratio detected by the detection means 13 and outputs the result of the comparison to the calculation means 15.
The calculation means 15 includes an S/N modified R curve storage section 15 consisting of a memory table, a calculation subroutine, etc.
A and S held in the S/N reoccupation curve storage section 15A.
The calculation section 15B calculates the number of times of averaging and the time based on the comparison result output from the comparator 14B while referring to the /N rewriting curve.

Here, the S/N improvement curve will be explained based on FIG. 2.

It is known that the power reduction rate NR due to i-times averaging can be expressed by the following formula: N: 5th-place integer I: number of averaging operations.

From this formula, the amount of improvement in exponential averaging (s/
N ) A is expressed as (S/N) A=10 log(NR).

To increase (S/N)A with N as a parameter, use N
Since it is better to have a larger value, the value of N is changed as follows depending on the number of times of averaging.

■Range i=5~64 N,=32■Range
1=65-4228 N2=1024 Range (1) 1=4229-cc+N3=8192 As a result, the S/N change curve becomes as shown in FIG.

If the current S/N ratio is known from the graph shown in FIG. 2, an answer can be obtained as to how many times the averaging is required to reach a predetermined S/N ratio.

Next, the operation will be explained.

First, prior to the measurement, a predetermined S/N ratio is set in the setter 14A, and the S/N improvement curve is stored in the S/N correction curve storage section 15A.

At this point, when the optical pulse tester is operated, the fourth
Since the waveform of the backscattered light as shown in Figure (a) is displayed, a specific position on the display screen is specified using the marker specifying means 12 by moving the marker.

At this time, the marker designation means 12 outputs a designation signal S1 to the detection means 13 indicating that a specific position has been designated.
The detection means 13 detects the current S/N ratio at a specific position according to the designated signal S1, and sends the detected signal S2 to the comparator 14.
Output to B.

The comparator 14B selects the predetermined S set in the setter 14A.
The setting No. 45 S3 representing the /N ratio is compared with the detection signal S2, and the difference between the current S/N ratio and the S/N ratio set in the setting device is calculated and sent to the calculation unit 15B as a comparison signal S4. hand over.

When the calculation unit 15B receives the comparison signal S4, the calculation unit 15B refers to the S/N improvement curve storage unit 15A until the current S/N ratio represented by the detection signal '+32 reaches the predetermined S/N ratio represented by the setting signal S3. , outputs a cue 2 calculation signal S5 to the display means 16 and the stop means 17, indicating how many times the averaging is required or how long the averaging takes.

Here, the display means 16 displays the input output from the calculation means 15 (No. 3 S5) on the display screen of the CRT (9).

The meanings here include the number of times of averaging, the time required for averaging, the time il+ when averaging ends,
This is the remaining time until averaging ends, etc.

On the other hand, when averaging is performed up to the number of times of averaging calculated by calculation means 15, stopping means 17 automatically stops averaging based on calculation signal S5.

In this example, the S/N is 6! The second one is in the curved storage part 15A.
Although an example is shown in which the graph of the S/N improvement curve shown in the figure is stored as a memory table, a configuration may also be adopted in which calculation formulas are stored and the number of averaging times and time are calculated using a calculation subroutine.

Furthermore, the S/N improvement curve herein refers not only to graphs and calculation formulas, but also to generically represents the correspondence between the comparison signal output by the comparison means and the number of times of averaging and time.

[Effects of the Invention] As explained below, according to the present invention, the number of times of averaging and the time required to reach a predetermined S/N ratio are calculated, the calculation results are displayed on the display screen, and the averaging times and time required to reach a predetermined S/N ratio are calculated. Since the configuration is configured to stop when the ratio is reached, the measurer can always
There is no need to monitor the RT screen, and the accuracy of measurement results does not vary depending on the measurer.

Furthermore, there is no need for the measurer to constantly monitor the CRT screen, and there is an effect that the aheracing is automatically stopped at the averaging number and time displayed on the display screen.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a configuration diagram showing an embodiment of the present invention, and Fig. 2 is an S
Figure 3 shows a graph of the /N corridor curve, Figure 3 and 1 shows the configuration of a conventional optical pulse tester, and Figure 4 shows the waveform of backscattered light projected on the CRT of the optical pulse tester. be. ! -CPU, 2.-timing generation section, 3.-light emitting section, 4.unidirectional coupler, 6.-light receiving section, 7.-amplifier,
8-A/D converter, 12--Marker specification 1 stage, 13
-...Detection means, 14--Comparison means, 15-...Calculation f
1st stage, 16--display means, 17--stop means. Figure 2 Averaging number of times (times)

Claims (2)

[Claims] (1) A predetermined light pulse is sent out from the light source, the backscattered light and Fresnel reflected light reflected from the object to be measured are sampled and converted into digital signals, and the characteristics of the object to be measured are displayed on the display screen. The optical pulse tester includes a marker specifying means for specifying a specific position on the display screen by moving a marker, a detecting means for detecting the S/N ratio of the position specified by the marker specifying means, and a preset and a comparison means for comparing a predetermined S/N ratio detected by the detection means with the S/N ratio detected by the detection means, and a predetermined averaging number of times and
An optical pulse tester comprising: a calculation means for calculating time; and a stop means for stopping averaging according to the result calculated by the calculation means. (2) Sends a predetermined light pulse from the light source, samples the backscattered light and Fresnel reflected light reflected from the object to be measured, converts them into digital signals, and displays the characteristics of the object to be measured on the display screen. The optical pulse tester includes a marker specifying means for specifying a specific position on the display screen by moving a marker, a detecting means for detecting the S/N ratio of the position specified by the marker specifying means, and a preset and a comparison means for comparing a predetermined S/N ratio detected by the detection means with the S/N ratio detected by the detection means, and a predetermined averaging number of times and
The present invention is characterized by comprising a calculation means for calculating the time, a stop means for stopping averaging according to the result calculated by the calculation means, and a display means for displaying the fact according to the result calculated by the calculation means. Optical pulse tester.