JPH07198471A - Vibration source position detector - Google Patents

Abstract

PURPOSE:To obtain a vibration source position detector mainly for detecting a frequency by determining correlation in signal between a transmission pulse of a light signal and a return light. CONSTITUTION:Light from a laser diode which is driven in emission with a vibration source 2 of a pulse generator or the like is admitted into an optical fiber 8 through a directive coupler 3 and a connector 20. The reflected light from the optical fiber 8 returns to the coupler 3 to be detected with a return light detector 4 and then, amplified with an amplifier 5 to perform a signal processing by a sampling and A/D conversion means 11 and a mean calculating means 15a. Then, a desired measuring position is specified from a loss vs distance characteristic displayed and vibration is detected at the specified position. In other words, correlation in signal is determined between a transmission pulse of a light signal and the return light to detect the frequency of the vibration. This enables the detection of the position of the vibration of the optical fiber 8 itself, the positions of other vibration sources close to the optical fiber 8, the vibration amplitude and vibration frequency of the vibration sources.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration source position detecting device of a type in which the vibration of the optical fiber itself or the vibration obtained by a vibration sensor is transmitted as an optical signal and detected by the optical fiber. The detection of the vibration source by the optical fiber of the present application includes the detection of the signal converted into the optical signal by the vibration sensor. The fields of application are: (a) Abnormality for detecting abnormal vibration of facilities such as buildings in advance, which is composed of a vibration source position detector and optical fibers installed in a linear, planar or three-dimensional structure. Use as a vibration detection position and its frequency detector. (B) As a system for monitoring abnormal conditions in the premises (always monitoring), or for monitoring abnormal vibration of the communication line itself or its surroundings via a communication line using a combination of a normal optical fiber communication facility and the above vibration source position detector There are uses. (C) By installing optical fibers in a wide area, it can be applied as a monitoring device for earthquake prediction.

[0002]

2. Description of the Related Art A drawback of the conventional electric signal transmission type device is that, in order to detect vibrations at a plurality of points, FIG.
2 x N for N vibration source detection points
A signal line for detecting (location) was required. or,
In this case, the variation of each vibration sensor may be a problem. In addition, if the number is increased or a vibration sensor is added, incorrect wiring may occur, and the wiring becomes complicated and enormous as the number of vibration detection locations increases. Furthermore, even if a conventional optical fiber fault point position detector (hereinafter referred to as an optical pulse tester) for detecting a fault point or the like is used, it must have a means for dynamic fluctuation analysis for a predetermined point. No, the vibration could not be detected immediately. Conventionally, the vibration signal in the optical pulse tester (OTDR) is regarded as noise in the case of measurement, and the idea of detecting the vibration specifically for the measurement is considered as an optical pulse even though efforts are made to remove it. It was not in the technical field of test equipment.

[0003]

SUMMARY OF THE INVENTION In view of the above, the present invention further develops the function of the conventional optical pulse tester to detect the vibration at a predetermined position of the optical fiber so that the vibration at the predetermined position can also be detected. It was done. For this reason,
The frequency is mainly detected by detecting and analyzing the change over time in the loss of the optical fiber caused by bending, etc., that is, by correlating the signal of the optical signal used for measurement with the return pulse. It is an object to provide a vibration source position detecting device.

[0004]

[Means for Solving the Problems]

(Corresponding to claim 1) In order to achieve the above object, a vibration source position detecting device of the present invention comprises an optical fiber and a vibration source position detector, and this vibration source position detector sequentially outputs a plurality of pulse signals. After the pulse output means 2 having a means for transmitting, the optical signal transmitting / receiving means 3 including the optical directional coupler 3b, the O / E converter 4, and the plurality of pulse signals being transmitted from the optical pulse output means, Means (11, 12, 21a) for obtaining and storing each loss amount from the return light (at the same position of the optical fiber) of each pulse signal after a predetermined time, and the loss amount of each return light with respect to time. It is characterized in that it comprises a filter means 15e for detecting a frequency component from such a change and a display means 7 for displaying the result, and detects the vibration of the optical fiber itself at a desired position of the optical fiber.

(Corresponding to claim 2) Further, after the plurality of pulse signals are transmitted from the optical pulse output means, each pulse signal is returned from the return light (at the same position of the optical fiber) after a predetermined time. Means for finding and storing loss amount (6, 1
2, 21a), a pulse signal generating means 2 including a pulse sending interval control means 2a for controlling the sending interval of the pulse signal, a change value of the loss amount of each return light having a different interval, and the pulse sending interval. And a means 15 for outputting the frequency data from the calculation result, and the frequency and the vibration amplitude of the optical fiber at the desired position are obtained from the weak return light signal.

(Corresponding to claim 3) A vibration source position detector for injecting an optical pulse into an optical fiber to receive Fresnel reflected light or backscattered light from the optical fiber to be measured and to analyze the received optical signal. A pulse output means 2 for sequentially transmitting a pseudo-random signal, an optical signal transmission / reception means 3 for converting an output of the pulse output means into an optical signal and transmitting the optical signal to the optical fiber, and receiving a return light from the optical fiber, and an optical signal. O / which receives the return light from the signal transmitting / receiving means and converts it into an electric signal
Generates a pseudo random signal with the E converter 4, and
The signal is sent to the pulse output means, a delay signal identical to the pseudo random signal is generated after a predetermined delay time, and the pulse signal is sent to the optical fiber,
Output from the means 12 for calculating the desired position of the optical fiber from the time until it is received as return light, the display means (7) for displaying the measurement result, the pseudo random signal of the return light and the control means. Means (16, 21a) for obtaining a correlation with the delayed pseudo random signal to output and storing the correlation signal, and for reading out the change in the loss amount of each return light of the pseudo random signal from the means. A means 15j for displaying a value corresponding to the temporal change on the display means is provided, and the vibration of the optical fiber at a desired position is obtained from a weak return light signal.

(Corresponding to claim 4) A vibration source position detector for injecting an optical pulse into an optical fiber to receive Fresnel reflected light or backscattered light from the optical fiber to be measured and to analyze the received return light. A pulse output means 2 for sequentially transmitting a plurality of pulse signals, an optical signal transmission / reception means 3 for converting the output of the pulse output means into an optical signal and transmitting the optical signal to the optical fiber and receiving return light from the optical fiber. O / which receives the return light from the optical signal transmitting / receiving means and converts it into an electric signal
E converter 4 and means (11, 21a) for obtaining and storing the time until the return light is received and the level of the return light
And a display means 7 for displaying the output result, calculating a predetermined position of the optical fiber from the time from when the pulse signal is sent to the optical fiber until it is received as return light, and A plurality of modulated burst signal B transmission periods T1 and a plurality of burst signal B pause periods T2 are alternately arranged to form one set of one cycle T (T1 + T).
2) Repeatedly, and the above O / E
Control the converter 4 to open the receiving gate after the optical pulse signal is transmitted and at a time T4 during which the predetermined first and last pulses of the burst signal are returned. And a control means 12 for controlling.

(Corresponding to Claim 5) Burst-modulated coherent light is incident on the optical fiber to be measured, and the return light from the optical fiber to be measured is subjected to optical homodyne detection to detect vibration of the optical fiber to be measured. In the position detector position,
Means 2g for generating a first modulated light, which is a coherent light modulated in a burst form, and a second modulated light (local light), which is the same as the modulated signal and delayed by a command from the control means And an optical signal transmission / reception means 3 which is a four-terminal optical coupling means for emitting the first modulated light to the optical fiber to be measured and coupling the return light from the optical fiber to be measured with the second modulated light, An O / E converter 4 that receives the combined light and an optical variable signal that changes the second modulated light that is incident on the combining means are generated, and the modulated signal is sent to the pulse output means, and a predetermined signal is generated. Means 12a for generating a modulated delayed signal identical to the modulated signal after a delay time, and from the time after the modulated signal is sent to the optical fiber until it is received as return light, Calculate the desired position of the optical fiber Control means 12 for obtaining the correlation between the modulated signal of the return light and the delayed modulated signal output from the control means, and outputting and storing the correlation signal, and the modulated signal of the modulated signal. Means 1 for reading the loss amount data of each return light from the means and displaying a value corresponding to the temporal change on the display means.
5j and is characterized in that the vibration of the optical fiber at a desired position is obtained from a weak return light signal.

(Corresponding to claim 6) Next, an optical fiber (8) and a vibration sensor 9 coupled to the optical fiber,
A vibration source position detecting device comprising a vibration source position detector 1, wherein the vibration sensor 9 is a vibration sensor 30 or an optical fiber which is detachably mounted on the optical fiber after the optical fiber is installed. The vibration sensor 40 is connected to a connector.

[0010]

[Operation] Upon receiving the return light from the optical fiber (8),
The vibration frequency of the vibration source is determined by detecting the change over time in the vent loss of the optical fiber.
The loss of the optical fiber 8 changes due to bending, and the periodic component of the change in bending loss due to vibration is included in the return light signal as a change in loss amount (vibration frequency component) corresponding to the vibration. The vibration amplitude is also included as a level change of the loss amount. Therefore, by amplifying and extracting this signal component (frequency component, vibration amplitude component), it is possible to detect the position of the vibration source at a remote place and to detect its frequency and amplitude. For minute changes, the periodicity of the periodic optical pulse signal sent from the device with variable pulse sending intervals and the return light reflected from the bending position is taken with good timing. It enables more reliable and speedy detection.

Regarding the relationship between the vibration characteristics and the data from the optical fiber to be measured, some of the optical fiber losses are those caused by slight deviation (or microbending) of the optical fiber axis from the longitudinal direction, Rayleigh scattering, etc. There is. However, it is difficult to detect these loss amounts clearly due to various noise components, and therefore the average of many sampling values is calculated. For this reason, when determining both the loss characteristic and the vibration characteristic for the entire distance of the optical fiber, the average value of many data values is used. Moreover, unlike the static defect detection of a damaged portion, in the case of vibration, it is necessary to collect a large amount of data in a short time, and an improved technique is used for the conventional optical pulse tester described below.

Generally, the distance-to-level characteristic is obtained from the average value output of a large number of points which is the output of the averager 15a. The measurement data is input to the CRT device 7 and displayed on the screen as shown in FIG. This C
The RT device 7 constitutes a display unit of the vibration source position detector 1. In this way, the distance-to-level characteristic obtains the loss amount from the average value of many data by the averager, but the vibration data, as shown in FIG. 5, has the temporal level (loss data) at one desired point (distance). ).
Moreover, it is necessary to collect a lot of data within a short time.
Therefore, bend the optical fiber close to the critical angle, measure the fluctuations of the loss at the desired position so that the loss can be clearly seen as vibrations, and measure the feed pulse according to the frequency of the gauge. This is dealt with by increasing the number of signals by a factor of 1000 to 10000 or more in some cases, as compared with the conventional stationary gauge mark. As described above, the hardware difference from the conventional optical pulse tester (OTDR) is that it is intended for those having a temporal change, and various devices described in the embodiments of the present application will be described below. It is adopted.

[0013]

EXAMPLES Examples 1 and 2 correspond to low-frequency vibrations, and Examples 2 to 4 correspond to high-frequency vibrations. (Embodiment 1) This will be described with reference to FIGS. This vibration source position detector 1 uses the optical directional coupler (or AO switch) shown in FIG. , EO switch, or dichroic mirror, half mirror, polarizing prism, etc.) 3b and a connecting portion (connector) 20 to enter the optical fiber 8 of a predetermined length. The reflected light from the optical fiber 8 returns to the optical directional coupler 3b, is detected by the photodetector 4, is amplified by the amplifier 5, and is sampling and A / D converting means 11 and average value calculating means (averager) 15a. The signal processing is performed by the above, and the above-mentioned portion has the same configuration as a general optical pulse tester. (See FIG. 2) Then, the desired measurement position is specified from the displayed loss-distance characteristic (the same as in the conventional technique), and then the vibration at the specified position is detected.

The structure of the present invention therefore has a control means 12 and A / for sampling a signal after a predetermined time after sending a pulse signal to arbitrarily specify a predetermined distance.
A D converter 11 is provided, and after the pulse signal is sent from the pulse signal generating means, a return light after a desired time is sequentially received to store each loss amount 21a and the memory 21a. It has vibration processing means 15j for converting the content into a signal whose horizontal axis is time and whose vertical axis is an optical signal level. As a result, the state in which the vibration signal from the vibration source at the desired position changes with time is visually displayed on the display means 7, and the time P between the peak value and the peak value is displayed.
1, and the frequency and amplitude values are visually determined on the display screen from the level difference value P2 between the peak value and the peak value. Specifically, due to the vibration of the level of the returning light,
It is assumed that the wave shape changes with time.
Then, the maximum and minimum peaks in the wave are compared and obtained, and if they are A1 and A2, respectively, the following equation (1) is obtained.

[0015]

[Equation 1]

Here, n is the number of data. By multiplying this by the conversion constant stored in the storage means 21c, the intensity of vibration can be obtained.

A level A vs. frequency characteristic curve at the same distance point is shown in FIG. (Embodiment 2) FIG. 2A is a block diagram showing a second embodiment of the vibration source position detecting device according to the present invention. The configuration of the present embodiment has a control means 12 and a data sampling and A / D conversion means for sending a plurality of pulse signals (to specify an arbitrary predetermined distance) and then sampling the signals after the same predetermined time. 11a, and 21a for storing the respective loss amounts and filtering means for processing the respective data by receiving the return light after the predetermined time after the pulse signal is transmitted from the pulse signal generating means. 15e. The vibration source position detector of the first embodiment has a configuration in which pulse transmission interval control means 2a, filtering means 15e, peak detection means 15c and peak calculation means 15d are added.

The operation is based on the pulse transmission interval control means 2a.
To transmit optical pulse signals having different pulse transmission intervals to the optical fiber (further, the pulse phase varying means 2b changes the phase within the range of about π / 2 with the same pulse transmission interval). , The peak point of the level depending on the frequency f2 of the returning light is calculated. That is, the correlation between the vibration in the vibration source and this pulse transmission interval (or the change in the phase by the phase changing means) is calculated,
As a result, the peak value of the level of return light after filtering is obtained. The frequency f is calculated from the cycle of this peak value.
And means 15 for calculating A so-called sweeping effect that sequentially changes the pulse interval is used. Although the signal to be obtained is obtained from the signals including the harmonics, the method of processing the vibration frequency of interest is divided into two before the details of the calculation are described.

That is, in the case of vibration having a frequency corresponding to a period of d which is about 10 to 100 times the interval d of the feed pulse signal. The processing method is divided into the case of the frequency corresponding to the period d of 1 to 1/10 or less with respect to the interval d of the sending pulse signal. First, in the case of low-frequency oscillation with respect to the sending pulse (the former), it is easily obtained from the output (for example, 100 hearts) by filtering the temporal change in the level of the returning light. next,
In case of high frequency vibration (latter), it is based on "heterodyne method". It is determined from the frequency f of the beat signal (for example, with a vibration of 10 kilo-Harts, a pulse of 1
In the case of about 0.5 kilo hearts, a beat signal of 500 hearts). That is, the frequency f = | f1−f2 | of the difference between the frequencies of the beat components of the two frequencies of the feed and the reception is obtained by the low pass filter. This frequency f2 and the sending frequency f1 (the reciprocal of the period of the optical pulse sending interval is f1
And ) And the absolute value f1 -f2 is calculated. After that, when f1 is increased or decreased, it is determined which of the signs is based on the change in the value of the frequency f, and the frequency f2 of the vibration source is determined.

[0020] It is the smaller the frequency f when increasing the frequency f _1, the frequency f is f = f2 -f1 next seeking also, the greater the frequency f is when increasing the frequency f _1, the frequency f to determine the It is determined that f = f1 -f2 and output.

Further, the amplitude value A is calculated and output from the signal (level) between the peak values after filtering.
(By the peak detecting means 15c at the level.) The actual amplitude is determined by the output of the filter means and the contrast data stored in advance in the memory (21a) and the physical vibration amplitude control data. Convert the amplitude of vibration from
Obtained (by the peak calculating means 15d). As an example of the filtering means, in addition to a normal LC low-pass filter, the output of the A / D converter 11 may be received and digitally calculated (digital filter means or calculation means by Fourier transform).

(Embodiment 3) A third embodiment will be described with reference to FIGS.
In particular, by applying the pseudo-random signal and correlation technology, in order to obtain a large amount of data corresponding to a high frequency, the signal level of the weak measured signal component that returns in response to the continuously output pseudo-random signal. Similarly, the weak correlated signal component to be measured is extracted by utilizing the correlation output with the delayed pseudo-random signal output from the control means 12. An optical fiber fault point search method for measuring the transmission characteristics of an optical fiber by applying a pseudo-random signal and a correlation technique to the one similar to this technique is, for example, the 1987 IEICE General National Convention magazine 8-278. There are technologies introduced on the page and the technology disclosed in JP-A-64-059031. 3 and 4 show an embodiment of a vibration detecting positioner using a pseudo random signal according to the present invention.

Here, the pseudo random signal generating means 12
a is provided in the control means and generates the pseudo-random signal, and the signal is sent to the pulse output means and, after a predetermined delay time, the same code-modulated delay signal as the pseudo-random signal. Similarly, the control means 12 is generated. Then, the desired position of the optical fiber is calculated from the time from when the pulse signal is sent to the optical fiber until it is received as return light. A means (16, 21a) for obtaining the correlation between the pseudo random signal of the return light and the delayed pseudo random signal output from the control means 12, outputting and storing the correlation signal, and each of the pseudo random signals. A means 15j for reading the change in the loss amount of the return light from the means and displaying the change on the display means in response to the change, the vibration of the optical fiber at a desired position from a weak return light signal. I tried to find the number.

In this way, the correlation for detecting only the signal synchronized with the delayed pseudo-random signal output from the control means 12 with respect to the measured signal component returning to the input end side as the backscattered light. By using the means, weak return light can be detected. This Example and the Next Example 4
By combining and, it is possible to perform signal processing with better S / N. As the type of the continuous signal, in addition to the pseudo random signal, a coded random signal (binary signal of zero and one) used in the following fourth embodiment, a phase modulation signal having a change in pulse interval, or the like may be used. good.

(Embodiment 4) In the vibration source position detector,
The optical pulse output means alternately repeats a set of a plurality of modulated burst signal B transmission periods T1 and a burst signal B pause period T2 as one cycle T (T1 + T2), and the E / O By allowing the converter 3 to open the receiving gate after the transmission of the optical pulse signal and in the time zone T4 between the return of the predetermined first and last pulses of the burst signal, A vibration source position detector characterized in that after transmitting an optical pulse, the reception is cut off in an excessive return light reception band T3 to prevent saturation of the O / E converter (4). This and Example 3 or Example 5
Can be used together. In this case, by sending a pulse every about 10 nS, 1 mS which is one normal period
About 100,000 pulse outputs and light receptions are possible.

T3 and T4 in FIG. 8 indicate the time zones of the sending pulse signal and the strong light receiving signal which is the returning light thereof, respectively.
Although the time zone T3 of this strong received light signal depends on the state of the optical fiber, it generally appears at the entrance of the optical fiber as in the example of FIG. In this case, within the pulse rest period T2, the time zone T4 in which the signal of the reference point returns after α hours from the end of the time zone T3 of the strong light receiving signal is set. In order to process as many pulse signals as possible within a short time, it is preferable to set a new time zone for T1 immediately after the end of T4.

As described above, T1 and T2 are repeated within a short time in the case of a relatively short distance control point, and in the case of a long distance, pulses are continuously transmitted within the T1 time zone. By receiving the returning light continuously, it is possible to transmit and receive a large amount of data regardless of the distance between the reference points.

(Embodiment 5) An explanation will be given based on FIG. As a technique related to this embodiment, there is a technique described in JP-A-62-217135. Burst coherent light is incident on the optical fiber to be measured, optical homodyne detection is performed on the return light from the optical fiber to be measured, and burst coherent light is detected on the vibration source position detector that detects the vibration of the optical fiber to be measured. In the vibration source position detector unit that detects the vibration of the measured optical fiber by performing optical homodyne detection of the return light from the measured optical fiber that is incident on the measured optical fiber, the optical switch 2e generates unmodulated coherent light in the steady state. Then
Phase modulation means 2g that emits first modulated light that is coherent light modulated in bursts during modulation, and generates delayed second modulated light (local light) that is the same as the above-mentioned modulation signal during demodulation. An optical signal transmission / reception means 3a comprising a four-terminal optical coupling means for emitting the first modulated light to the optical fiber to be measured and coupling the return light from the optical fiber to be measured with the second modulated light; O / E that receives the combined light
A signal for controlling the converter 4 and the second modulated light incident on the coupling means is generated, and the modulated signal is sent to the pulse output means and delayed by the same delay as the modulated signal after a predetermined delay time. A means 12a for generating a modulation signal is provided inside, and means 12 for calculating a desired position of the optical fiber from the time from when the modulation signal is sent to the optical fiber until it is received as return light. And a means (16,
21a) and means 15j for reading from the means a change in the amount of loss of the return light of each of the modulated signals and displaying a value corresponding to the temporal change on the display means. The frequency of the optical fiber at the desired position is calculated from the weak return light signal.

This frequency is automatically calculated by the frequency detecting means 15g from the value between the peaks. Here, the coherent light emitted from the coherent light generating means 2f is sent to the optical signal transmitting / receiving means 3a via the optical switch 2e or the phase modulating means 2g. Here, as the optical switch 2e and the phase modulation means 2g, for example, a switch that controls the connection and disconnection and the phase by applying an electric field to the optical switch using the electro-optical effect is used. As described above, in this embodiment, since the switch can perform high-speed modulation or switching, more data can be obtained in a shorter time.

More specifically, burst coherent light is incident on the optical fiber to be measured, the return light from the optical fiber to be measured is detected by optical homodyne detection, and the change in vent loss at the desired position of the optical fiber to be measured is detected. It is an example of a homodyne detection system that detects as vibration. Figure 4
FIG. 4A and FIG. 4B are configuration diagrams of the present embodiment, in which a coherent light source and a modulation light (phase modulation or frequency modulation light) of a coherent light beam modulated in a burst form are emitted, Means 2g for generating the same delayed local light as the modulated signal, the modulated light is emitted to the optical fiber to be measured, and the return light from the optical fiber is combined with the modulated light which is the local light. An optical signal transmission / reception means 3a comprising a 4-terminal optical coupling means,

O / E converter 4 for receiving the combined light
And an optical variable signal for changing the second modulated light incident on the coupling means is generated, the modulated signal is sent to the pulse output means, and after the predetermined delay time, the same modulated delay as the modulated signal. Means 12a for generating a signal, and means 12 for calculating a desired position of the optical fiber from the time from when the modulated signal is sent to the optical fiber until it is received as return light, Means (16a, 2) for correlating the modulated signal of the return light and the delayed modulated signal output from the control means, and outputting and storing the correlation signal.
1a) and means 15j for reading the change of the loss amount of the return light of each of the modulated signals from the means and displaying the change on the display means in response to the change, and the frequency corresponding to the change. It was equipped with 15 g of means for obtaining. The modulation signal may be either the phase modulation of the coherent light or the frequency modulation of the coherent light. In the case of this frequency modulation, the same modulated light as that used for modulation is used as reference light during demodulation.

(Embodiment 6) Next, an embodiment of a vibration source position detecting device and a vibration sensor using a vibration sensor connected to an optical fiber will be described with reference to FIGS. 1, 7 and 11-16. To do. In this embodiment, an optical fiber 8, a vibration sensor 9 coupled to the optical fiber, and a vibration source position detector 1 are provided. The vibration sensor 9 may be either a vibration sensor 30 which is detachably mounted on the optical fiber after the optical fiber is installed or a vibration sensor 40 which is connected to the optical fiber by a connector.

In an optical fiber used in a communication path or the like in which bend loss is suppressed as much as possible, it may be difficult to measure loss and change in loss due to vibration with high sensitivity. Therefore, this can be reduced by connecting an optical fiber for a sensor (for example, a step index fiber) that is sensitive to this bending (the change in loss is large with respect to the bending) in series with an optical fiber for transmission to form a vibration sensor. A large angle loss can be obtained by the bending angle, and the vibration can be detected as the variation. As the other vibration sensor, the other vibration sensor described above is used.

[Vibration sensor 30 used in the fifth embodiment,
Description of 40 ”Referring to FIGS. 11 and 12, the vibration sensor 30 provided afterwards includes means 32 for transmitting mechanical vibration from the outside to the optical fiber, and a holder 31 for holding the optical fiber in bending at a critical angle. Is provided. Also,
In FIG. 15, the connector-connected vibration sensor 40 is provided with means 41 which is connected to an optical fiber by a connector 48 and receives light from the optical fiber and returns it to the optical fiber as a reflected signal which is intermittent. And (FIG. 15) Specific examples of the vibration sensor 30 are shown in FIGS.
This is shown in FIGS.

11 (a) and 11 (b) are examples of a vibration sensor that converts the number of revolutions (wind speed, etc.) into the number of vibrations and transmits it to the optical fiber. If this sensor is configured as a tuning fork as shown in FIG. 16, a natural phenomenon such as temperature can be converted into vibration and detected with high accuracy. If a material that deforms due to humidity is used, it can be used for humidity detection. FIG. 11 (c)
Shows an example of a vibration sensor 30 which is a plastic integral type pressure-bonding type and is attached later.

12 (a) and 12 (b) are views showing a vibration sensor 30 to be attached later. By attaching this vibration sensor to a desired place after installing the optical fiber, the vibration of the holder due to the vibration and the change of the bending loss due to the vibration of the optical fiber can be detected as the vibration signal by the vibration source position detector. FIG. 12 shows a vibration sensor 3 which is attached later.
It is 0, and since it is slotted, it is a figure which shows the structure which an optical fiber can be similarly retrofitted from the clearance. FIG. 13 is a view showing an example of a connector connection type vibration sensor which is a sensor for detecting weak vibrations and is similar to the above.

Here, the vibration sensor is of a type in which a spring-supported mirror which is easily vibrated is returned to the optical fiber via the tip lens. It becomes a vibration sensor that captures various vibrations. If you bundle multiple optical fibers and cut them in the middle so that the number becomes smaller toward the tip, attach a vibration sensor to the tip and detect both the vibration and distance from the vibration source position. It can be detected by a vessel.

FIG. 15 is a diagram showing an example of a vibration sensor of the connector connection type. Here, in FIG.
It is a figure which shows the structure of the system which shields the same optical path as shown in (c) periodically with the reflector attached to the front-end | tip of a tuning fork. FIG. 14B shows a vibration sensor 30 attached later, which is also a diagram showing an example of a vibration sensor of a connection type,
The bending loss is changed by directly vibrating the optical fiber bent near the predetermined radius of curvature at the tip of the tuning fork.

FIG. 16 shows a sixth embodiment of the vibration sensor 30. The shape memory alloy causes the center weight point of the tuning fork to fluctuate, resulting in a change in the frequency of the tuning fork. A slight change in temperature for this purpose can be captured as a change in the frequency of the tuning fork. Since the amount of change in amplitude (change in temperature) is transmitted as a frequency change, it is possible to accurately obtain even a slight change around the reference frequency. Or, by combining multiple bimetals that change greatly with temperature,
Configure. (Vents are given to the optical fiber by the bimetal.) The change in frequency (relationship between shape and change) can be detected in fine steps depending on the temperature.

FIG. 9B shows the display waveform when the pulse interval (phase) is changed. The frequency and feed pulse interval are synchronized, and high level A1 at the peak point of reflection and A3 at low level peak are reflected.
It is a figure which shows that it is different from the case of. FIG. 9 (c)
At this time, although the harmonic component may be measured at this time, the figure showing the state of the level in the case of selecting it, removing the harmonic component, and detecting the frequency. Where A1
, A3 are high and low level reflections as described above, and A2 is the reflection level at other points. As described above, in the measurement of the unknown frequency, first, the approximate frequency fk is obtained, and then the next frequency fk is aimed and measured to efficiently perform signal processing. Can be done. Also in the case of the change of the sending pulse interval in the second and fourth embodiments, it is possible to approach the frequency fk of the reference point in a shorter time by performing the frequency sweep method by the change of the pulse phase.

FIGS. 15A and 15B show a connector-connection type vibration sensor 40. FIG. 15A shows a vibration sensor configured to reflect a sinusoidal signal as a periodic signal.
The periodic reflection signal is connected to the anemometer and can be used as a sensor for detecting its rotation speed. FIG.15 (b) shows the side view. Here, the optical pulse signal sent from the optical fiber passes through the tip lens and is further transmitted to the optical fiber when there is no reflector 41, but when reflected by the reflector 41, it corresponds to the cycle. It is sent to the vibration source position detector side as return light of an on / off signal. in this case,
In the vibration sensor, the light is branched into two by the two-branch connector and a part of the optical signal is transmitted as it is in the optical fiber, so that it is possible to detect a plurality of subsequent vibration source positions. A plurality of optical fibers are installed, the number of optical fibers becomes smaller toward the front, and a vibration sensor 40 is provided at the tip of each optical fiber. It is also possible to centrally monitor the returned light with. This has the advantage that no expensive connector is required.

As an application thereof, FIG. 15 illustrates that a complex signal can be similarly transmitted as a periodic signal. That is, when the periodic signal of 11011010 is used as the reflection signal, the reflection portion 4 of the rotating plate 41 of FIG.
3 is a specific shape.

The vibration amplitude A at the vibration frequency f is obtained as an analog quantity. By using a V-to-F converter that converts this vibration amplitude level into a frequency, the vibration amplitude A can be more accurately measured as with the above frequency. Can be detected. Similarly, for a long-period vibration (sway) such as an earthquake (foreshadowing), the frequency can be converted to an appropriate (high) frequency and detected more accurately. Alternatively, low vibration and high vibration can be measured in parallel.

(Embodiment 7) Next, FIG. 17 shows an embodiment of installation of an optical fiber, which is carried out using a bidirectional vibration source position detector with reference to FIGS. Here is an example: FIG. 19 shows an installation method capable of double-checking the position and a bidirectional vibration source position detector for efficiently performing the installation method. As a result, a distant weak signal can be obtained as a strong signal by reversing the sending end. In this case, a plurality of vibration source positions are displayed on the display screen of the display means 7 while being contrasted with each other in the forward and reverse directions, so that a weak signal can be visually calibrated and confirmed. The optical signal transmission / reception means 3b is a 4-terminal AO switch, and the direction of the transmission / reception pulse is controlled by a control signal from the electrode.

(Application) According to the vibration source position detecting apparatus according to the present embodiment, the physical vibration of the optical fiber itself is detected, and the signal from the vibration sensor in the vicinity of the optical fiber is transmitted to the optical fiber to detect the signal. In addition to detection, the following applications are possible. That is, the reflected signal corresponding to the physical change of the distant optical fiber can be received and analyzed as the periodic reflected signal. Also in this case, when the reflected light amount changes in a predetermined cycle (analog or digital),
Since the detection is performed in synchronization with the method according to the second embodiment, it is possible to accurately detect even a weak reflected signal from a distance from the device side.

FIGS. 15A and 15B show a dedicated vibration sensor for generating a special reflection signal which is a periodic reflection signal but is close to the code signal. Note that FIG.
5 (b) is a diagram showing an enlarged view of the side surface thereof. FIG. 10 shows a method of installing a cylindrical optical fiber when it is used for a characteristic experiment of a large rotary drive (or a large oil tank). Here, a vibration sensor is attached at a desired position to enable monitoring of abnormal vibrations. In this case, it is possible to artificially repeat driving and stopping to check the presence or absence of vibration and to calibrate and measure initial values such as amplitude values.

(A) Specific application example Detection of abnormal vibration of facilities / equipment inside or outside the premises or cables. It converts natural phenomena (temperature, pressure, wind speed) into changes in frequency and transmits them to the optical fiber. It is possible to detect the position of a vibration source at a remote location and to detect its amplitude and frequency. Practical examples are large bridges, tunnels, facilities in factories, railways, inside vehicles, etc. (B) For weak vibrations over a long distance, the feed pulse interval is changed (second to sixth embodiments). Alternatively, it is detected by a method using a dedicated vibration sensor (sixth embodiment). (Effect of Embodiment 3) A relatively large amount of data can be obtained in a short time, and since the correlation detection method is used, a vibration signal can be obtained with a good S / N.

(Effect of Embodiment 4) A relatively large amount of data can be obtained with good S / N in a short time. Further, it is possible to avoid excessive reflected light at the entrance of the optical fiber and receive only weak return light for signal processing. Therefore, it is possible to grasp a time-varying state such as vibration by receiving a lot of data. (Effect of Example 5) Referring to FIG. Since it can be modulated or switched at high speed, more data can be obtained in a shorter time than in the other embodiments. Further, since the heterodyne detection is performed by using the local light, a weak gauge point signal can be amplified and obtained. Moreover, since the local light is a known signal, increase the local light to
There is an advantage that the S / N is improved by the amount of the amplification.

[0049]

According to the vibration source position detecting device of the present invention,
It is possible to detect the vibration position of the optical fiber itself, the position of another vibration source near the optical fiber, and the vibration amplitude and vibration frequency thereof. Moreover, it is possible to detect the vibration original positions at a plurality of locations at the same time with one optical fiber. Therefore, the vibration source position, the vibration amplitude, and the vibration frequency can be accurately obtained for a planar or three-dimensional object over a wide range of applications and over a long distance. As an applied effect, for example, an effect that a physical quantity such as a pressure at a remote place is converted into a frequency according to the level and detected, or a local abnormal vibration monitoring device for a large rotating body can be realized There is. However, the details of the effect of the vibration source position monitoring device of the present application are as described in the following itemization.

It is possible to continuously monitor the position of the vibration source and the change in the frequency in a linear, planar or three-dimensional range. There is an effect that an optical fiber can be prepared after the facility by crimping or sandwiching it so that a predetermined vibration is transmitted to a desired position without using an expensive connector to connect the vibration sensor. In particular, it corresponds to the embodiment and claim (6). Regular inspection (constant monitoring) is possible. Can be used repeatedly. Little change over time.

The change point of the amplitude and frequency of periodic vibration can be monitored from a long distance. (A total length of 20 km or more is also possible).
In the case of the embodiment in which the optical fiber itself also serves as the vibration source sensor, the signal converter is not required, and the equipment can be simplified. Also, by using the vibration sensor shown,
It does not require an electrical sensor circuit that enables more accurate vibration monitoring, and can be applied as an abnormal vibration monitoring system for facilities such as optical fiber communication lines and surrounding structures. Any type of optical fiber can be used. In addition, once the optical fiber is installed, maintenance is inexpensive. ─
─ Excluding the case of the embodiment and claim (5). Use of one optical fiber enables simultaneous monitoring from one point or at multiple points.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a vibration source position detecting device of the present invention.

FIG. 2 is a block diagram showing first and second embodiments of the vibration source position detector.

FIG. 3 is a partial detailed view of the first embodiment of the vibration source position detector of the present invention.

FIG. 4 is a detailed view of third to fifth embodiments of the vibration source position detector of the present invention. FIG. 6A is a detailed view of the third to fifth embodiments of the vibration source position detector of the present invention. (B) is a partial detailed view of the fifth embodiment.

FIG. 5 is a diagram showing an example in which the output of this device is displayed on a display means (CRT device), and an example in which the vibration source position and frequency are shown at the same time.

FIG. 6A is a diagram showing the positions of the feed pulse and the feed pulse displayed on the display screen. (B) is a figure which shows the signal example of the return light on the same display screen.

FIG. 7 is a diagram of a clad, a core, and a radius of curvature of an optical fiber, showing that the loss sharply increases when the angle α is less than a specified value.

FIG. 8 is a diagram showing an operation time chart of the fourth embodiment of the vibration source position detecting device of the invention.

FIG. 9 is a diagram showing an example in which the output of this device is displayed on a display means (CRT device). (A) shows the case where there are a plurality of vibration source positions. (B) is a display example of the vibration at the above-mentioned one point. (C) is a display example of a harmonic signal.

FIG. 10 is a diagram showing an application example of the vibration source position detecting device of the present invention (installation example of an optical fiber).

FIG. 11 is a diagram showing an outline of first and second embodiments of the vibration sensor 30 of the vibration source position detecting device of the present invention. (A) is
The figure which shows the structure of the vibration sensor which can be attached or detached easily. (B)
The figure which shows the state after the said restoration. FIG. 6C is a diagram showing a sensor that can be changed to a sensor with one touch and a sensor that returns to its original state as a transmission path after restoration (a vibration sensor that can be retrofitted and is integrally molded with plastic).

FIG. 12 is a diagram showing a third and a fourth embodiment of the vibration sensor 30 (both of which can be retrofitted). (A) is a third embodiment and (b) is a fourth embodiment, both of which are made of a grooved vibration sensor (bending angle is set to a critical angle) and plastch. It is a figure which shows the holder of the vibration sensor with a spiral type optical fiber insertion groove.

FIG. 13 is a first example of the vibration sensor 40 (for detecting weak vibration).

FIG. 14 is a tuning fork type vibration sensor 3 that can be retrofitted.
The figure which shows the 0th 5th Example.

FIG. 15 is a view showing a second embodiment of the vibration sensor 40 connected to the connector. (A) is a third embodiment of the vibration sensor 40, which is a vibration sensor having a periodic reflection signal generating means (including information in the rotation signal). FIG. 6B is a diagram showing a side view of the vibration sensor 40.

FIG. 16 is a sixth embodiment of the vibration sensor 30 for detecting temperature and humidity.

FIG. 17 is a diagram showing an example of installation of an optical fiber.

FIG. 18 is a diagram showing an embodiment when a bidirectional vibration source position detector is used.

FIG. 19 is a diagram showing an example of installation of an optical fiber when a bidirectional vibration source position detector is used.

FIG. 20 is a view showing a conventional example.

[Explanation of symbols]

1 ... Vibration source position detector 2 ... Pulse output means 2a ... Pulse transmission interval control and phase varying means 2c ... Code pulse signal generating means 2d ... Reference pulse generating means 3 ... Optical Signal transmitting / receiving means 3a ... E / O converter (LD) 3b ... Optical directional coupler (optical switch) 4 ... O / E converter (ADP) 5 ... Amplifier 7 ... Display Means (CRT device) 8 ... Optical fiber 9 ... Vibration sensor 9a ... Vibration source 10 ... Display control means 11 ... A / D converter (data sampling and A /
D conversion means) 12 ... control means 13 ... switch means 15 ... correlation calculation means (15c, 15d, 15e) 15a ... average value calculation means 15b ... vibration processing means (horizontal axis represents time) With respect to the vertical axis for processing to display output) 15c ... Peak detecting means (amplitude) 15d ... Peak calculating means (frequency vs. level) 15e ... Filtering means 15g ... Frequency detecting means 15f ... Correlation calculation means 15h ... Changeover switch 15j ... Distance body level correspondence processing means 16, 16a ... Correlation means 20 ... Connector 21a ... Memory a (loss amount vs. distance and time Related data) 21b ... Memory b (harmonic signal data table) 21c ... Memory c (relationship data of loss amount to amplitude amount) 30 ... Vibration sensor that can be retrofitted FIG. 40 shows an example of a vibration sensor connected to a connector, FIG. 50 shows an example of a vibration sensor connected to a connector 50, 50a ... Data processing means p ... Pulse control signal q ... Optical pulse signal r ... Return light s ... Sliwari

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] March 23, 1995

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Vibration source position detector and vibration source position detecting device

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration source position detecting device of a type in which the vibration of the optical fiber itself or the vibration obtained by a vibration sensor is transmitted as an optical signal and detected by the optical fiber. The detection of the vibration source by the optical fiber of the present application includes the detection of the signal converted into the optical signal by the vibration sensor. The fields of application are: (a) Abnormality for detecting abnormal vibration of facilities such as buildings in advance, which is composed of a vibration source position detector and optical fibers installed in a linear, planar or three-dimensional structure. Use as a vibration detection position and its frequency detector. (B) As a system for monitoring abnormal conditions in the premises (always monitoring), or for monitoring abnormal vibration of the communication line itself or its surroundings via a communication line using a combination of a normal optical fiber communication facility and the above vibration source position detector There are uses. (C) By installing optical fibers in a wide area, it can be applied as a monitoring device for earthquake prediction.

[0002]

2. Description of the Related Art A drawback of the conventional electric signal transmission type device is that, in order to detect vibrations at a plurality of points, FIG.
2 x N for N vibration source detection points
A signal line for detecting (location) was required. or,
In this case, the variation of each vibration sensor may be a problem. In addition, if the number is increased or a vibration sensor is added, incorrect wiring may occur, and the wiring becomes complicated and enormous as the number of vibration detection locations increases. Furthermore, even if a conventional optical fiber fault point position detector (hereinafter referred to as an optical pulse tester) for detecting a fault point or the like is used, it must have a means for dynamic fluctuation analysis for a predetermined point. No, the vibration could not be detected immediately. Conventionally, the vibration signal in the optical pulse tester (OTDR) is regarded as noise in the case of measurement, and the idea of detecting the vibration specifically for the measurement is considered as an optical pulse even though efforts are made to remove it. It was not in the technical field of test equipment.

[0003]

SUMMARY OF THE INVENTION In view of the above, the present invention further develops the function of the conventional optical pulse tester to detect the vibration at a predetermined position of the optical fiber so that the vibration at the predetermined position can also be detected. It was done. For this reason,
The frequency is mainly detected by detecting and analyzing the change over time in the loss of the optical fiber caused by bending, etc., that is, by correlating the signal of the optical signal used for measurement with the return pulse. It is an object to provide a vibration source position detecting device.

[0004]

Means for Solving the Problems (corresponding to claim 1) To achieve the above object, a vibration source position detecting device of the present invention includes an optical fiber and a vibration source position detector, and detects the vibration source position. A pulse output unit 2 having a unit for sequentially transmitting a plurality of pulse signals, an optical signal transmission / reception unit 3 including an optical directional coupler 3b, an O / E converter 4, and the optical pulse output unit from the plurality of units. Means (11, 12, 21a) for determining and storing the respective loss amounts from the return light (at the same position of the optical fiber) of each pulse signal after a predetermined time after the pulse signals of A filter means 15e for detecting a frequency component from the temporal change of the loss amount of the return light, and a display means 7 for displaying the result, and detecting the vibration of the optical fiber itself at a desired position of the optical fiber. Characterized by .

(Corresponding to claim 2) Further, after the plurality of pulse signals are transmitted from the optical pulse output means, each pulse signal is returned from the return light (at the same position of the optical fiber) after a predetermined time. Means for finding and storing loss amount (6, 1
2, 21a), a pulse signal generating means 2 including a pulse sending interval control means 2a for controlling the sending interval of the pulse signal, a change value of the loss amount of each return light having a different interval, and the pulse sending interval. And a means 15 for outputting the frequency data from the calculation result, and the frequency and the vibration amplitude of the optical fiber at the desired position are obtained from the weak return light signal.

(Corresponding to claim 3) A vibration source position detector for injecting an optical pulse into an optical fiber to receive Fresnel reflected light or backscattered light from the optical fiber to be measured and to analyze the received optical signal. A pulse output means 2 for sequentially transmitting a pseudo-random signal, an optical signal transmission / reception means 3 for converting an output of the pulse output means into an optical signal and transmitting the optical signal to the optical fiber, and receiving a return light from the optical fiber, and an optical signal. O / which receives the return light from the signal transmitting / receiving means and converts it into an electric signal
Generates a pseudo random signal with the E converter 4, and
The signal is sent to the pulse output means, a delay signal identical to the pseudo random signal is generated after a predetermined delay time, and the pulse signal is sent to the optical fiber,
Output from the means 12 for calculating the desired position of the optical fiber from the time until it is received as return light, the display means (7) for displaying the measurement result, the pseudo random signal of the return light and the control means. Means (16, 21a) for obtaining a correlation with the delayed pseudo random signal to output and storing the correlation signal, and for reading out the change in the loss amount of each return light of the pseudo random signal from the means. A means 15j for displaying a value corresponding to the temporal change on the display means is provided, and the vibration of the optical fiber at a desired position is obtained from a weak return light signal.

(Corresponding to claim 4) A vibration source position detector for injecting an optical pulse into an optical fiber to receive Fresnel reflected light or backscattered light from the optical fiber to be measured and to analyze the received return light. A pulse output means 2 for sequentially transmitting a plurality of pulse signals, an optical signal transmission / reception means 3 for converting the output of the pulse output means into an optical signal and transmitting the optical signal to the optical fiber and receiving return light from the optical fiber. O / which receives the return light from the optical signal transmitting / receiving means and converts it into an electric signal
E converter 4 and means (11, 21a) for obtaining and storing the time until the return light is received and the level of the return light
And a display means 7 for displaying the output result, calculating a predetermined position of the optical fiber from the time from when the pulse signal is sent to the optical fiber until it is received as return light, and A plurality of modulated burst signal B transmission periods T1 and a plurality of burst signal B pause periods T2 are alternately arranged to form one set of one cycle T (T1 + T).
2) Repeatedly, and the above O / E
Control the converter 4 to open the receiving gate after the optical pulse signal is transmitted and at a time T4 during which the predetermined first and last pulses of the burst signal are returned. And a control means 12 for controlling.

(Corresponding to claim 5) A coherent light beam modulated in a burst form is incident on an optical fiber to be measured, a return light from the optical fiber to be measured is subjected to optical homodyne detection, and a vibration source for detecting vibration of the optical fiber to be measured. In the position detector, the coherent light emits the first modulated light that is modulated in a burst shape, and the second modulated light (local light) that is delayed by the same command as the above-mentioned modulated signal is issued by a command from the control means 12. And an optical signal including a means 2g for generating the first modulated light and a four-terminal optical coupling means for coupling the first modulated light to the measured optical fiber and coupling the return light from the measured optical fiber with the second modulated light. The transmitting / receiving means 3, the O / E converter 4 for receiving the combined light, and the optical variable signal for changing the second modulated light incident on the combining means are generated, and the modulated signal is generated by the pulse output means. Smell, A time period from the sending of the modulated signal to the optical fiber to the receipt of the returning light, which has means 12a for generating the same modulated delayed signal as the modulated signal after a fixed delay time. From the control means 12 for calculating the desired position of the optical fiber, the means for calculating the correlation between the modulated signal of the return light and the delayed modulated signal output from the control means, and outputting and storing the correlation signal (16) , 21a) and the loss amount data of the return light of each of the modulated signals from the means, and means 15 for displaying a value corresponding to the temporal change on the display means.
j, and is characterized in that the vibration of the optical fiber at a desired position is obtained from a weak return light signal.

(Corresponding to claim 6) Next, an optical fiber (8) and a vibration sensor 9 coupled to the optical fiber,
A vibration source position detecting device comprising a vibration source position detector 1, wherein the vibration sensor 9 is a vibration sensor 30 or an optical fiber which is detachably mounted on the optical fiber after the optical fiber is installed. The vibration sensor 40 is connected to a connector.

[0010]

[Operation] Upon receiving the return light from the optical fiber (8),
The vibration frequency of the vibration source is determined by detecting the change over time in the vent loss of the optical fiber.
The loss of the optical fiber 8 changes due to bending, and the periodic component of the change in bending loss due to vibration is included in the return light signal as a change in loss amount (vibration frequency component) corresponding to the vibration. The vibration amplitude is also included as a level change of the loss amount. Therefore, by amplifying and extracting this signal component (frequency component, vibration amplitude component), it is possible to detect the position of the vibration source at a remote place and to detect its frequency and amplitude. For minute changes, the periodicity of the periodic optical pulse signal sent from the device with variable pulse sending intervals and the return light reflected from the bending position is taken with good timing. It enables more reliable and speedy detection.

Regarding the relationship between the vibration characteristics and the data from the optical fiber to be measured, some of the optical fiber losses are those caused by slight deviation (or microbending) of the optical fiber axis from the longitudinal direction, Rayleigh scattering, etc. There is. However, it is difficult to detect these loss amounts clearly due to various noise components, and therefore the average of many sampling values is calculated. For this reason, when determining both the loss characteristic and the vibration characteristic for the entire distance of the optical fiber, the average value of many data values is used. Moreover, unlike the static defect detection of a damaged portion, in the case of vibration, it is necessary to collect a large amount of data in a short time, and an improved technique is used for the conventional optical pulse tester described below.

Generally, the distance-to-level characteristic is obtained from the average value output of a large number of points which is the output of the averager 15a. The measurement data is input to the CRT device 7 and displayed on the screen as shown in FIG. This C
The RT device 7 constitutes a display unit of the vibration source position detector 1. In this way, the distance-to-level characteristic obtains the loss amount from the average value of many data by the averager, but the vibration data, as shown in FIG. 5, has the temporal level (loss data) at one desired point (distance). ).
Moreover, it is necessary to collect a lot of data within a short time.
Therefore, bend the optical fiber close to the critical angle, measure the fluctuations of the loss at the desired position so that the loss can be clearly seen as vibrations, and measure the feed pulse according to the frequency of the gauge. This is dealt with by increasing the number of signals by a factor of 1000 to 10000 or more in some cases, as compared with the conventional stationary gauge mark. As described above, the hardware difference from the conventional optical pulse tester (OTDR) is that it is intended for those having a temporal change, and various devices described in the embodiments of the present application will be described below. It is adopted.

[0013]

EXAMPLES Examples 1 and 2 correspond to low-frequency vibrations, and Examples 2 to 4 correspond to high-frequency vibrations. (Embodiment 1) This will be described with reference to FIGS. This vibration source position detector 1 uses the optical directional coupler (or AO switch) shown in FIG. , EO switch, or dichroic mirror, half mirror, polarizing prism, etc.) 3b and a connecting portion (connector) 20 to enter the optical fiber 8 of a predetermined length. The reflected light from the optical fiber 8 returns to the optical directional coupler 3b, is detected by the photodetector 4, is amplified by the amplifier 5, and is sampling and A / D converting means 11 and average value calculating means (averager) 15a. The signal processing is performed by the above, and the above-mentioned portion has the same configuration as a general optical pulse tester. (See FIG. 2) Then, the desired measurement position is specified from the displayed loss-distance characteristic (the same as in the conventional technique), and then the vibration at the specified position is detected.

The structure of the present invention therefore has a control means 12 and A / for sampling a signal after a predetermined time after sending a pulse signal to arbitrarily specify a predetermined distance.
A D converter 11 is provided, and after the pulse signal is sent from the pulse signal generating means, a return light after a desired time is sequentially received to store each loss amount 21a and the memory 21a. It has vibration processing means 15j for converting the content into a signal whose horizontal axis is time and whose vertical axis is an optical signal level. As a result, the state in which the vibration signal from the vibration source at the desired position changes with time is visually displayed on the display means 7, and the time P between the peak value and the peak value is displayed.
1, and the frequency and amplitude values are visually determined on the display screen from the level difference value P2 between the peak value and the peak value. Specifically, due to the vibration of the level of the returning light,
It is assumed that the wave shape changes with time.
Then, the maximum and minimum peaks in the wave are compared and obtained, and if they are A1 and A2, respectively, the following equation (1) is obtained.

[0015]

[Equation 1]

Here, n is the number of data. By multiplying this by the conversion constant stored in the storage means 21c, the intensity of vibration can be obtained.

A level A vs. frequency characteristic curve at the same distance point is shown in FIG. (Embodiment 2) FIG. 2A is a block diagram showing a second embodiment of the vibration source position detecting device according to the present invention. The configuration of the present embodiment has a control means 12 and a data sampling and A / D conversion means for sending a plurality of pulse signals (to specify an arbitrary predetermined distance) and then sampling the signals after the same predetermined time. 11a, and 21a for storing the respective loss amounts and filtering means for processing the respective data by receiving the return light after the predetermined time after the pulse signal is transmitted from the pulse signal generating means. 15e. The vibration source position detector of the first embodiment has a configuration in which pulse transmission interval control means 2a, filtering means 15e, peak detection means 15c and peak calculation means 15d are added.

The operation is based on the pulse transmission interval control means 2a.
To send optical pulse signals with different pulse sending intervals to the optical fiber (in addition, by the function of varying the pulse phase, the same pulse sending intervals can be used and the phase can be changed within a range of about π / 2). , The frequency f of the return light
Calculate the peak point of the level depending on 2. That is,
The correlation between the vibration in the vibration source and this pulse transmission interval (or the change in the phase by the phase changing means) is calculated, and as a result, the peak value of the level of the returning light after filtering is obtained. Further, it is provided with a means 15 for calculating the frequency f from the cycle of this peak value. A so-called sweeping effect that sequentially changes the pulse interval is used. Although the signal to be obtained is obtained from the signals including the harmonics, the method of processing the vibration frequency of interest is divided into two before the details of the calculation are described.

That is, in the case of vibration having a frequency corresponding to a period of d which is about 10 to 100 times the interval d of the feed pulse signal. The processing method is divided into the case of the frequency corresponding to the period d of 1 to 1/10 or less with respect to the interval d of the sending pulse signal. First, in the case of low-frequency oscillation with respect to the sending pulse (the former), it is easily obtained from the output (for example, 100 hearts) by filtering the temporal change in the level of the returning light. next,
In case of high frequency vibration (latter), it is based on "heterodyne method". It is determined from the frequency f of the beat signal (for example, with a vibration of 10 kilo-Harts, a pulse of 1
In the case of about 0.5 kilo hearts, a beat signal of 500 hearts). That is, the frequency f = | f1−f2 | of the difference between the frequencies of the beat components of the two frequencies of the feed and the reception is obtained by the low pass filter. This frequency f2 and the sending frequency f1 (the reciprocal of the period of the optical pulse sending interval is f1
And ) And the absolute value f1 -f2 is calculated. After that, when f1 is increased or decreased, it is determined which of the signs is based on the change in the value of the frequency f, and the frequency f2 of the vibration source is determined.

[0020] It is the smaller the frequency f when increasing the frequency f _1, the frequency f is f = f2 -f1 next seeking also, the greater the frequency f is when increasing the frequency f _1, the frequency f to determine the It is determined that f = f1 -f2 and output.

Further, the amplitude value A is calculated and output from the signal (level) between the peak values after filtering.
(By the peak detecting means 15c at the level.) The actual amplitude is determined by the output of the filter means and the contrast data stored in advance in the memory (21a) and the physical vibration amplitude control data. Convert the amplitude of vibration from
Obtained (by the peak calculating means 15d). As an example of the filtering means, in addition to a normal LC low-pass filter, the output of the A / D converter 11 may be received and digitally calculated (digital filter means or calculation means by Fourier transform).

(Embodiment 3) A third embodiment will be described with reference to FIGS.
In particular, by applying the pseudo-random signal and correlation technology, in order to obtain a large amount of data corresponding to a high frequency, the signal level of the weak measured signal component that returns in response to the continuously output pseudo-random signal. Similarly, the weak correlated signal component to be measured is extracted by utilizing the correlation output with the delayed pseudo-random signal output from the control means 12. An optical fiber fault point search method for measuring the transmission characteristics of an optical fiber by applying a pseudo-random signal and a correlation technique to the one similar to this technique is, for example, the 1987 IEICE General National Convention magazine 8-278. There are technologies introduced on the page and the technology disclosed in JP-A-64-059031. 3 and 4 show an embodiment of a vibration detecting positioner using a pseudo random signal according to the present invention.

Here, the pseudo random signal generating means 12
a is provided in the control means and generates the pseudo-random signal, and the signal is sent to the pulse output means and, after a predetermined delay time, the same code-modulated delay signal as the pseudo-random signal. Similarly, the control means 12 is generated. Then, the desired position of the optical fiber is calculated from the time from when the pulse signal is sent to the optical fiber until it is received as return light. A means (16, 21a) for obtaining the correlation between the pseudo random signal of the return light and the delayed pseudo random signal output from the control means 12, outputting and storing the correlation signal, and each of the pseudo random signals. A means 15j for reading the change in the loss amount of the return light from the means and displaying the change on the display means in response to the change, the vibration of the optical fiber at a desired position from a weak return light signal. I tried to find the number.

In this way, the correlation for detecting only the signal synchronized with the delayed pseudo-random signal output from the control means 12 with respect to the measured signal component returning to the input end side as the backscattered light. By using the means, weak return light can be detected. This Example and the Next Example 4
By combining and, it is possible to perform signal processing with better S / N. As the type of the continuous signal, in addition to the pseudo random signal, a coded random signal (binary signal of zero and one) used in the following fourth embodiment, a phase modulation signal having a change in pulse interval, or the like may be used. good.

(Embodiment 4) In the vibration source position detector,
The optical pulse output means alternately repeats a set of a plurality of modulated burst signal B transmission periods T1 and a burst signal B pause period T2 as one cycle T (T1 + T2), and the E / O By allowing the converter 3 to open the receiving gate after the transmission of the optical pulse signal and in the time zone T4 between the return of the predetermined first and last pulses of the burst signal, A vibration source position detector characterized in that after transmitting an optical pulse, the reception is cut off in an excessive return light reception band T3 to prevent saturation of the O / E converter (4). This and Example 3 or Example 5
Can be used together. In this case, by sending a pulse every about 10 nS, 1 mS which is one normal period
About 100,000 pulse outputs and light receptions are possible.

T3 and T4 in FIG. 8 indicate the time zones of the sending pulse signal and the strong light receiving signal which is the returning light thereof, respectively.
Although the time zone T3 of this strong received light signal depends on the state of the optical fiber, it generally appears at the entrance of the optical fiber as in the example of FIG. In this case, within the pulse rest period T2, the time zone T4 in which the signal of the reference point returns after α hours from the end of the time zone T3 of the strong light receiving signal is set. In order to process as many pulse signals as possible within a short time, it is preferable to set a new time zone for T1 immediately after the end of T4.

As described above, T1 and T2 are repeated within a short time in the case of a relatively short distance control point, and in the case of a long distance, pulses are continuously transmitted within the T1 time zone. By receiving the returning light continuously, it is possible to transmit and receive a large amount of data regardless of the distance between the reference points.

(Embodiment 5) An explanation will be given based on FIG. As a technique related to this embodiment, there is a technique described in JP-A-62-217135. Burst coherent light is made incident on the optical fiber to be measured, optical homodyne detection is performed on the return light from the optical fiber to be measured, and in the vibration source position detector unit that detects the vibration of the optical fiber to be measured Unmodulated coherent light is generated, and when modulated, the coherent light emits a first modulated light that is modulated in bursts, and when demodulated, a delayed second modulated light (local light) that is the same as the modulated signal. From the four-terminal optical coupling means for emitting the first modulated light to the optical fiber to be measured and for coupling the return light from the optical fiber with the second modulated light. And an O / E converter 4 for receiving the combined light.
And a signal for controlling the second modulated light incident on the coupling means is generated, the modulated signal is sent to the pulse output means, and after a predetermined delay time, a delayed modulated signal that is the same as the modulated signal is generated. A means 12 for generating the desired position of the optical fiber from the time from the time the modulated signal is sent out to the optical fiber until it is received as return light, the means 12 having the means 12a for generating the inside; Means (16, 21) for correlating the modulated signal of the return light and the delayed modulated signal output from the control means, and storing the correlation signal.
a) and means 15j for reading the change of the loss amount of each return light of the modulated signal from the means and displaying a value corresponding to the time change on the display means. The frequency of the optical fiber at the desired position is calculated from the weak return light signal.

This frequency is automatically calculated by the frequency detecting means 15g from the value between the peaks. Here, the coherent light emitted from the coherent light generating means 2f is sent to the optical signal transmitting / receiving means 3a via the optical switch 2e or the phase modulating means 2g. Here, as the optical switch 2e and the phase modulation means 2g, for example, a switch that controls the connection and disconnection and the phase by applying an electric field to the optical switch using the electro-optical effect is used. As described above, in this embodiment, since the switch can perform high-speed modulation or switching, more data can be obtained in a shorter time.

More specifically, burst coherent light is incident on the optical fiber to be measured, the return light from the optical fiber to be measured is detected by optical homodyne detection, and the change in vent loss at the desired position of the optical fiber to be measured is detected. It is an example of a homodyne detection system that detects as vibration. Figure 4
FIG. 4A and FIG. 4B are configuration diagrams of the present embodiment, in which a coherent light source and a modulation light (phase modulation or frequency modulation light) of a coherent light beam modulated in a burst form are emitted, Means 2g for generating the same delayed local light as the modulated signal, the modulated light is emitted to the optical fiber to be measured, and the return light from the optical fiber is combined with the modulated light which is the local light. An optical signal transmission / reception means 3a comprising a 4-terminal optical coupling means,

O / E converter 4 for receiving the combined light
And an optical variable signal for changing the second modulated light incident on the coupling means is generated, the modulated signal is sent to the pulse output means, and after the predetermined delay time, the same modulated delay as the modulated signal. Means 12a for generating a signal, and means 12 for calculating a desired position of the optical fiber from the time from when the modulated signal is sent to the optical fiber until it is received as return light, Means (16, 21) for correlating the modulated signal of the return light and the delayed modulated signal output from the control means, and outputting and storing the correlation signal.
a) and means 15j for reading the change of the loss amount of each return light of the modulated signal from the means and displaying the change on the display means in response to the change, and the frequency corresponding to the change. It was equipped with 15 g of means for obtaining. In addition,
The modulation signal may be either phase modulation of the coherent light or frequency modulation of the coherent light.
In the case of this frequency modulation, the same modulated light as that used for modulation is used as reference light during demodulation.

(Embodiment 6) Next, an embodiment of a vibration source position detecting device and a vibration sensor using a vibration sensor connected to an optical fiber will be described with reference to FIGS. 1, 7 and 11-16. To do. In this embodiment, an optical fiber 8, a vibration sensor 9 coupled to the optical fiber, and a vibration source position detector 1 are provided. The vibration sensor 9 may be either a vibration sensor 30 which is detachably mounted on the optical fiber after the optical fiber is installed or a vibration sensor 40 which is connected to the optical fiber by a connector.

In an optical fiber used in a communication path or the like in which bend loss is suppressed as much as possible, it may be difficult to measure loss and change in loss due to vibration with high sensitivity. Therefore, this can be reduced by connecting an optical fiber for a sensor (for example, a step index fiber) that is sensitive to this bending (the change in loss is large with respect to the bending) in series with an optical fiber for transmission to form a vibration sensor. A large angle loss can be obtained by the bending angle, and the vibration can be detected as the variation. As the other vibration sensor, the other vibration sensor described above is used.

[Vibration sensor 30 used in the sixth embodiment,
Description of 40 ”Referring to FIGS. 11 and 12, the vibration sensor 30 provided afterwards includes means 32 for transmitting mechanical vibration from the outside to the optical fiber, and a holder 31 for holding the optical fiber in bending at a critical angle. Is provided. Also,
In FIG. 15, the connector-connected vibration sensor 40 is provided with means 41 which is connected to an optical fiber by a connector 48 and receives light from the optical fiber and returns it to the optical fiber as a reflected signal which is intermittent. And (FIG. 15) Specific examples of the vibration sensor 30 are shown in FIGS.
This is shown in FIGS. 14 and 16.

11 (a) and 11 (b) are examples of a vibration sensor that converts the number of revolutions (wind speed, etc.) into the number of vibrations and transmits it to the optical fiber. If this sensor is configured as a tuning fork as shown in FIG. 16, a natural phenomenon such as temperature can be converted into vibration and detected with high accuracy. If a material that deforms due to humidity is used, it can be used for humidity detection. FIG. 11 (c)
Shows an example of a vibration sensor 30 which is a plastic integral type pressure-bonding type and is attached later.

12 (a) and 12 (b) are views showing a vibration sensor 30 to be attached later. By attaching this vibration sensor to a desired place after installing the optical fiber, the vibration of the holder due to the vibration and the change of the bending loss due to the vibration of the optical fiber can be detected as the vibration signal by the vibration source position detector. FIG. 12 shows a vibration sensor 3 which is attached later.
It is 0, and since it is slotted, it is a figure which shows the structure which an optical fiber can be similarly retrofitted from the clearance. FIG. 13 is a view showing an example of a connector connection type vibration sensor which is a sensor for detecting weak vibrations and is similar to the above.

Here, the vibration sensor is of a type in which a spring-supported mirror which is easily vibrated is returned to the optical fiber via the tip lens. It becomes a vibration sensor that captures various vibrations. If you bundle multiple optical fibers and cut them in the middle so that the number becomes smaller toward the tip, attach a vibration sensor to the tip and detect both the vibration and distance from the vibration source position. It can be detected by a vessel.

FIG. 15 is a diagram showing an example of a vibration sensor of the connector connection type. Here, it is possible to adopt a configuration in which the light is periodically shielded by a reflector attached to the tip of the tuning fork. FIG. 14B shows a vibration sensor 30 which is attached later.
FIG. 3 is a diagram showing an example of (3), in which the optical fiber bent near the predetermined radius of curvature at the tip of the tuning fork is directly vibrated to change the bending loss.

FIG. 16 shows a sixth embodiment of the vibration sensor 30. The shape memory alloy causes the center weight point of the tuning fork to fluctuate, resulting in a change in the frequency of the tuning fork. A slight change in temperature for this purpose can be captured as a change in the frequency of the tuning fork. Since the amount of change in amplitude (change in temperature) is transmitted as a frequency change, it is possible to accurately obtain even a slight change around the reference frequency. Or, by combining multiple bimetals that change greatly with temperature,
Configure. (Vents are given to the optical fiber by the bimetal.) The change in frequency (relationship between shape and change) can be detected in fine steps depending on the temperature.

FIG. 9B shows the display waveform when the pulse interval (phase) is changed. The frequency and feed pulse interval are synchronized, and high level A1 at the peak point of reflection and A3 at low level peak are reflected.
It is a figure which shows that it is different from the case of. FIG. 9 (c)
At this time, although the harmonic component may be measured at this time, the figure showing the state of the level in the case of selecting it, removing the harmonic component, and detecting the frequency. Where A1
, A3 are high and low level reflections as described above, and A2 is the reflection level at other points. As described above, in the measurement of the unknown frequency, first, the approximate frequency fk is obtained, and then the next frequency fk is aimed and measured to efficiently perform signal processing. Can be done. Also in the case of the change of the sending pulse interval in the second and fourth embodiments, it is possible to approach the frequency fk of the reference point in a shorter time by performing the frequency sweep method by the change of the pulse phase.

FIGS. 15A and 15B show a connector-connection type vibration sensor 40. FIG. 15A shows a vibration sensor configured to reflect a sinusoidal signal as a periodic signal.
The periodic reflection signal is connected to the anemometer and can be used as a sensor for detecting its rotation speed. FIG.15 (b) shows the side view. Here, the optical pulse signal sent from the optical fiber passes through the tip lens and is further transmitted to the optical fiber when there is no reflector 41, but when reflected by the reflector 41, it corresponds to the cycle. It is sent to the vibration source position detector side as return light of an on / off signal. in this case,
In the vibration sensor, the light is branched into two by the two-branch connector and a part of the optical signal is transmitted as it is in the optical fiber, so that it is possible to detect a plurality of subsequent vibration source positions. A plurality of optical fibers are installed, the number of optical fibers becomes smaller toward the front, and a vibration sensor 40 is provided at the tip of each optical fiber. It is also possible to centrally monitor the returned light with. This has the advantage that no expensive connector is required.

As an application thereof, FIG. 15 illustrates that a complex signal can be similarly transmitted as a periodic signal. That is, when the periodic signal of 11011010 is used as the reflection signal, the reflection portion 4 of the rotating plate 41 of FIG.
3 is a specific shape.

The vibration amplitude A at the vibration frequency f is obtained as an analog quantity. By using a V-to-F converter that converts this vibration amplitude level into a frequency, the vibration amplitude A can be more accurately measured as with the above frequency. Can be detected. Similarly, for a long-period vibration (sway) such as an earthquake (foreshadowing), the frequency can be converted to an appropriate (high) frequency and detected more accurately. Alternatively, low vibration and high vibration can be measured in parallel.

(Embodiment 7) Next, FIG. 17 shows an embodiment of installation of an optical fiber, which is carried out using a bidirectional vibration source position detector with reference to FIGS. Here is an example: FIG. 19 shows an installation method capable of double-checking the position and a bidirectional vibration source position detector for efficiently performing the installation method. As a result, a distant weak signal can be obtained as a strong signal by reversing the sending end. In this case, a plurality of vibration source positions are displayed on the display screen of the display means 7 while being contrasted with each other in the forward and reverse directions, so that a weak signal can be visually calibrated and confirmed. The optical signal transmission / reception means 3b is a 4-terminal AO switch, and the direction of the transmission / reception pulse is controlled by a control signal from the electrode.

(Application) According to the vibration source position detecting apparatus according to the present embodiment, the physical vibration of the optical fiber itself is detected, and the signal from the vibration sensor in the vicinity of the optical fiber is transmitted to the optical fiber to detect the signal. In addition to detection, the following applications are possible. That is, the reflected signal corresponding to the physical change of the distant optical fiber can be received and analyzed as the periodic reflected signal. Also in this case, when the reflected light amount changes in a predetermined cycle (analog or digital),
Since the detection is performed in synchronization with the method according to the second embodiment, it is possible to accurately detect even a weak reflected signal from a distance from the device side.

FIGS. 15A and 15B show a dedicated vibration sensor for generating a special reflection signal which is a periodic reflection signal but is close to the code signal. Note that FIG.
5 (b) is a diagram showing an enlarged view of the side surface thereof. FIG. 10 shows a method of installing a cylindrical optical fiber when it is used for a characteristic experiment of a large rotary drive (or a large oil tank). Here, a vibration sensor is attached at a desired position to enable monitoring of abnormal vibrations. In this case, it is possible to artificially repeat driving and stopping to check the presence or absence of vibration and to calibrate and measure initial values such as amplitude values.

(A) Specific application example Detection of abnormal vibration of facilities / equipment inside or outside the premises or cables. It converts natural phenomena (temperature, pressure, wind speed) into changes in frequency and transmits them to the optical fiber. It is possible to detect the position of a vibration source at a remote location and to detect its amplitude and frequency. Practical examples are large bridges, tunnels, facilities in factories, railways, inside vehicles, etc. (B) For weak vibrations over a long distance, the feed pulse interval is changed (second to sixth embodiments). Alternatively, it is detected by a method using a dedicated vibration sensor (sixth embodiment). (Effect of Embodiment 3) A relatively large amount of data can be obtained in a short time, and since the correlation detection method is used, a vibration signal can be obtained with a good S / N.

(Effect of Embodiment 4) A relatively large amount of data can be obtained with good S / N in a short time. Further, it is possible to avoid excessive reflected light at the entrance of the optical fiber and receive only weak return light for signal processing. Therefore, it is possible to grasp a time-varying state such as vibration by receiving a lot of data. (Effect of Example 5) Referring to FIG. Since it can be modulated or switched at high speed, more data can be obtained in a shorter time than in the other embodiments. Further, since the heterodyne detection is performed by using the local light, a weak gauge point signal can be amplified and obtained. Moreover, since the local light is a known signal, increase the local light to
There is an advantage that the S / N is improved by the amount of the amplification.

[0049]

According to the vibration source position detecting device of the present invention,
It is possible to detect the vibration position of the optical fiber itself, the position of another vibration source near the optical fiber, and the vibration amplitude and vibration frequency thereof. Moreover, it is possible to detect the vibration original positions at a plurality of locations at the same time with one optical fiber. Therefore, the vibration source position, the vibration amplitude, and the vibration frequency can be accurately obtained for a planar or three-dimensional object over a wide range of applications and over a long distance. As an applied effect, for example, an effect that a physical quantity such as a pressure at a remote place is converted into a frequency according to the level and detected, or a local abnormal vibration monitoring device for a large rotating body can be realized There is. However, the details of the effect of the vibration source position monitoring device of the present application are as described in the following itemization.

It is possible to continuously monitor the position of the vibration source and the change in the frequency in a linear, planar or three-dimensional range. There is an effect that an optical fiber can be prepared after the facility by crimping or sandwiching it so that a predetermined vibration is transmitted to a desired position without using an expensive connector to connect the vibration sensor. In particular, it corresponds to the embodiment and claim (6). Regular inspection (constant monitoring) is possible. Can be used repeatedly. Little change over time.

The change point of the amplitude and frequency of periodic vibration can be monitored from a long distance. (A total length of 20 km or more is also possible).
In the case of the embodiment in which the optical fiber itself also serves as the vibration source sensor, the signal converter is not required, and the equipment can be simplified. Also, by using the vibration sensor shown,
It does not require an electrical sensor circuit that enables more accurate vibration monitoring, and can be applied as an abnormal vibration monitoring system for facilities such as optical fiber communication lines and surrounding structures. Any type of optical fiber can be used. In addition, once the optical fiber is installed, maintenance is inexpensive. ─
─ Excluding the case of the embodiment and claim (5). Use of one optical fiber enables simultaneous monitoring from one point or at multiple points.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a vibration source position detecting device of the present invention.

FIG. 2 is a block diagram showing first and second embodiments of the vibration source position detector.

FIG. 3 is a partial detailed view of the first embodiment of the vibration source position detector of the present invention.

FIG. 4 is a detailed view of third to fifth embodiments of the vibration source position detector of the present invention. FIG. 6A is a detailed view of the third to fifth embodiments of the vibration source position detector of the present invention. (B) is a partial detailed view of the fifth embodiment.

FIG. 5 is a diagram showing an example in which the output of this device is displayed on a display means (CRT device), and an example in which the vibration source position and frequency are shown at the same time.

FIG. 6 is a diagram showing a signal of return light displayed on a display screen corresponding to the position of a feed pulse.

FIG. 7 is a diagram of a clad, a core, and a radius of curvature of an optical fiber, showing that the loss sharply increases when the angle α is less than a specified value.

FIG. 8 is a diagram showing an operation time chart of the fourth embodiment of the vibration source position detecting device of the invention.

FIG. 9 is a diagram showing an example in which the output of this device is displayed on a display means (CRT device). (A) shows the case where there are a plurality of vibration source positions. (B) is a display example of the vibration at the above-mentioned one point. (C) is a display example of a harmonic signal.

FIG. 10 is a diagram showing an application example of the vibration source position detecting device of the present invention (installation example of an optical fiber).

FIG. 11 is a diagram showing an outline of first and second embodiments of the vibration sensor 30 of the vibration source position detecting device of the present invention. (A) is
The figure which shows the structure of the vibration sensor which can be attached or detached easily. (B)
The figure which shows the state after the said restoration. FIG. 6C is a diagram showing a sensor that can be changed to a sensor with one touch and a sensor that returns to its original state as a transmission path after restoration (a vibration sensor that can be retrofitted and is integrally molded with plastic).

FIG. 12 is a diagram showing a third and a fourth embodiment of the vibration sensor 30 (both of which can be retrofitted). (A) is a third embodiment and (b) is a fourth embodiment, both of which are made of a grooved vibration sensor (bending angle is set to a critical angle) and plastch. It is a figure which shows the holder of the vibration sensor with a spiral type optical fiber insertion groove.

FIG. 13 is a first example of the vibration sensor 40 (for detecting weak vibration).

FIG. 14 is a tuning fork type vibration sensor 3 that can be retrofitted.
The figure which shows the 0th 5th Example.

FIG. 15 is a view showing a second embodiment of the vibration sensor 40 connected to the connector. (A) is a third embodiment of the vibration sensor 40, which is a vibration sensor having a periodic reflection signal generating means (including information in the rotation signal). FIG. 6B is a diagram showing a side view of the vibration sensor 40.

FIG. 16 is a sixth embodiment of the vibration sensor 30 for detecting temperature and humidity.

FIG. 17 is a diagram showing an example of installation of an optical fiber.

FIG. 18 is a diagram showing an embodiment when a bidirectional vibration source position detector is used.

FIG. 19 is a diagram showing an example of installation of an optical fiber when a bidirectional vibration source position detector is used.

FIG. 20 is a view showing a conventional example.

[Description of Codes] 1 ... Vibration source position detector 2 ... Pulse output means 2a ... Pulse transmission interval control and phase varying means 2c ... Code pulse signal generating means 2d ... Reference pulse Generating means 3 ... Optical signal transmitting / receiving means 3a ... E / O converter (LD) 3b ... Optical directional coupler (optical switch) 4 ... O / E converter (ADP) 5・ ・ ・ Amplifier 7 ・ ・ ・ ・ Display means (CRT device) 8 ・ ・ ・ ・ Optical fiber 9 ・ ・ ・ ・ Vibration sensor 9 a ・ ・ ・ Vibration source 10 ・ ・ ・ Display control means 11 ・ ・ ・ A / D Converter (data sampling and A /
D conversion means) 12 ... control means 13 ... switch means 15 ... correlation calculation means (15c, 15d, 15e) 15a ... average value calculation means 15b ... distance body level correspondence processing means 15c. ..Peak detection means (amplitude) 15d ... Peak calculation means (frequency vs. level) 15e ... Filtering means 15g ... Frequency detection means 15f ... Correlation calculation means 15h ... Changeover switch 15j ...・ Vibration processing means (means for processing the display output in which the horizontal axis is for time versus the vertical axis is for level) 16 ... Correlation means 20 ... Connector 21a ... Memory a (loss amount vs. distance and time relationship data) 21b ... Memory b (harmonic signal data table) 21c ... Memory c (relationship data of loss amount vs. amplitude amount) 30 ... Implementation of a vibration sensor that can be retrofit Fig. 40 shows the embodiment of the vibration sensor with connector connection 50, 50a ... Data processing means p ... Pulse control signal q ... Optical pulse signal r ... Return light s ...・ Slurry

[Procedure 3]

[Document name to be corrected] Drawing

[Correction target item name] Figure 8

[Correction method] Change

[Correction content]

[Figure 8]

Claims (6)

[Claims] 1. A vibration source position detector that receives an optical pulse to an optical fiber, receives the return light of Fresnel reflected light or backscattered light from the optical fiber, and analyzes the returned light.
Pulse output means (2) for sequentially transmitting a plurality of pulse signals
An optical signal transmission / reception means (3) for converting the output of the pulse output means into an optical signal, transmitting the optical signal to the optical fiber and receiving return light from the optical fiber, and receiving the return light from the optical signal transmission / reception means. An O / E converter (4) for converting into an electric signal, means (11, 21a) for obtaining and storing the time until the return light is received and the level of the return light, and after the pulse signal is transmitted, Control means (12) for calculating and outputting a predetermined position of the optical fiber from the time until it is received as return light, and a plurality of return lights respectively received after a predetermined time after transmitting a plurality of pulse signals. Is provided with a filter means (15e) for detecting and outputting the frequency component of the return light from the temporal change of the level of the output light, and a display means (7) for displaying the output result, and detecting the vibration at the desired position of the optical fiber. Possible Vibration source position detector characterized in that the. 2. An optical fiber (8) and a vibration source position detector (6) for receiving an optical pulse into the optical fiber to receive Fresnel reflected light or backscattered light from the optical fiber and analyzing the received optical signal ( 1) and a vibration source position detector, wherein the vibration source position detector (1) is a pulse output means (2) for sequentially sending a plurality of pulse signals.
An optical signal transmission / reception means (3) for converting the output of the pulse output means into an optical signal, transmitting the optical signal to the optical fiber and receiving return light from the optical fiber, and receiving the return light from the optical signal transmission / reception means. An O / E converter (4) for converting into an electric signal, a means (11, 21a) for obtaining and storing the time until the return light is received and the level of the return light, and a sending interval of the pulse signal are arbitrary. And a pulse transmission interval control means (2a) for controlling the pulse transmission interval, a means (12) for calculating a predetermined position of the optical fiber from the time until the pulse signal is received as return light after being transmitted, A display means (7) for displaying a result and a correlation calculation of the change value of the loss amount of the respective return lights having different intervals and the pulse transmission interval are performed, and the frequency and amplitude value data are output from the calculation result. Correlation calculator With a step (15),
A vibration source position detecting device, wherein a vibration frequency and a vibration amplitude of an optical fiber at a desired position are obtained from a weak return light signal. 3. A vibration source position detector which receives an optical pulse to an optical fiber, receives Fresnel reflected light or backscattered light from the optical fiber to be measured, and analyzes the received optical signal, which is a pseudo random signal. Pulse output means (2) for sequentially transmitting
An optical signal transmission / reception means (3) for converting the output of the pulse output means into an optical signal, transmitting the optical signal to the optical fiber and receiving return light from the optical fiber, and receiving the return light from the optical signal transmission / reception means. An O / E converter (4) for converting into an electric signal and a pseudo random signal are generated, and the signal is sent to the pulse output means to generate the same delay signal as the pseudo random signal after a predetermined delay time. Also, means (12) for calculating the desired position of the optical fiber from the time after the pulse signal is sent to the optical fiber until it is received as return light, and a display means () for displaying the measurement result. 7), a means (16, 21a) for obtaining a correlation between the pseudo random signal of the return light and the delayed pseudo random signal output from the control means, and outputting and storing the correlation signal; A means (15j) for reading the change of the loss amount of each returning light of the similar random signal from the means and displaying a value corresponding to the time change on the display means, the weak return. A vibration source position detector characterized in that the vibration of an optical fiber at a desired position is obtained from a light signal. 4. A vibration source position detector which receives an optical pulse to an optical fiber, receives Fresnel reflected light or backscattered light from the optical fiber to be measured, and analyzes the received return light. Pulse output means for sequentially transmitting signals (2)
An optical signal transmission / reception means (3) for converting the output of the pulse output means into an optical signal, transmitting the optical signal to the optical fiber and receiving return light from the optical fiber, and receiving the return light from the optical signal transmission / reception means. An O / E converter (4) for converting into an electric signal, means (11, 21a) for obtaining and storing the time until the return light is received and the level of the return light, and a display means for displaying the output result (7) is provided, and a predetermined position of the optical fiber is calculated from a time from when the pulse signal is sent to the optical fiber until it is received as return light, and the optical pulse output means is used to make a plurality of The modulated burst signal B transmission period T1 and the burst signal B pause period T2 are alternately set to one cycle T (T1
+ T2) and repeat the above O
After the optical pulse signal is transmitted by the A / E converter 4, the reception gate is opened in the time zone T4 during which the predetermined first and last pulses of the burst signal are returned. To prevent saturation of the O / E converter (4) by interrupting the reception at least in the reception band T3 of the excessive returned light after transmitting the optical pulse. Vibration source position detector characterized by. 5. A vibration source position detector for detecting coherent light, which is modulated in a burst form, into an optical fiber to be measured, performs optical homodyne detection on return light from the optical fiber to be measured, and detects vibration of the optical fiber to be measured. The coherent light emits a first modulated light that is modulated in a burst form, and a second modulated light (local light) that is the same as the modulated signal and delayed is generated by a command from the control means (12). Means (2g) for outputting the first modulated light to the optical fiber to be measured, and a return light from the optical fiber to be coupled with the second modulated light, an optical signal composed of four-terminal optical coupling means. Transmitting / receiving means (3), an O / E converter (4) for receiving the combined light, and an optical variable signal for changing the second modulated light incident on the combining means are generated, and the modulated signal is generated. The pulse output means Having means (12a) for generating the same modulated delayed signal as the modulated signal after a predetermined delay time, and after the modulated signal is sent to the optical fiber until it is received as return light The control means (12) for calculating the desired position of the optical fiber from the time, and the modulated signal of the return light and the delayed modulated signal output from the control means are correlated, and the correlation signal is output and stored. Means (16a, 21a), and means (15j) for reading the loss amount data of the return light of each of the modulated signals from the means and displaying a value corresponding to the temporal change on the display means. And a vibration source position detector characterized in that the vibration of an optical fiber at a desired position is obtained from a weak return light signal. 6. An optical fiber (8), a vibration sensor (9) coupled to the optical fiber, an optical pulse incident on the optical fiber, and Fresnel reflected light or backscattered light from the measured optical fiber. A vibration source position detector comprising the vibration source position detector (1) according to any one of claims 1 to 5, which receives the light and analyzes the received optical signal.