JP3295595B2 - Optical fiber type physical quantity measurement system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber type physical quantity measuring system, and more particularly, to a transmission type time division multiplexing type optical fiber type multi-point optical fiber using an optical fiber suitable for collectively measuring physical quantities at multiple points. The present invention relates to a physical quantity measurement system.

[0002]

2. Description of the Related Art Conventionally, as an optical fiber type multi-point physical quantity measuring system for detecting physical quantities such as temperature, humidity, liquid leakage, etc., a configuration as shown in FIG. ).

The optical fiber type multi-point physical quantity measuring system shown in FIG. 10 comprises a sensor section A for obtaining optical data necessary for detecting a physical quantity, and a measurement section for measuring a predetermined physical quantity from the optical data of the sensor section A. And part B.

The sensor section A includes a transmitting optical fiber 1a and a receiving optical fiber 1b arranged in parallel, a plurality of optical splitters 3 arranged at respective positions corresponding to the two optical fibers 1a and 1b, An optical physical quantity sensor 2 connected between these optical splitters 3 and whose optical loss changes due to a change in physical quantity. However, an optical attenuator 8 is connected between the optical splitters 3 located closest to the transmitting and receiving ends of the two optical fibers 1a and 1b without passing through the optical physical quantity sensor 2.

The measuring section B includes an optical pulse generator 4 for inputting an optical pulse to the transmitting optical fiber 1a of the sensor section A, and a light receiving section for receiving the optical pulse from the receiving optical fiber 1b of the sensor section A and performing photoelectric conversion. It comprises a device 5 and a signal processing device 6 for measuring a predetermined physical quantity in the optical physical quantity sensor 2 based on a change in the light intensity of the received light pulse of the light receiver 5. When an optical pulse enters the transmission optical fiber 1 a from the optical pulse generator 4, a part of the incident optical pulse is supplied to each optical physical quantity sensor 2 via each optical splitter 3. The intensity of the light pulse supplied to the optical physical quantity sensor 2 changes according to the physical quantity of each sensor, and is received by the light receiver 5 via each optical splitter 3 and the receiving optical fiber 1b. After the light pulse received by the light receiver 5 is converted into an electric signal,
The signal is supplied to the signal processing device 6. And the signal processing device 6
Then, the physical quantity in each optical physical quantity sensor 2 is calculated based on the change in the light intensity of the received signal.

In this manner, as shown in FIG. 11, the distribution of signals supplied from the light receiver 5 to the signal processing device 6 includes:
The light receiving pulse 10 is detected for each delay time corresponding to the distance from the measurement unit B of each optical physical quantity sensor 2. Reference numeral 9 denotes a light-receiving pulse that has returned after passing through the optical attenuator 8;
1 is a background noise. The light receiving pulse includes effects of light loss in the reciprocating optical fibers 1a and 1b or by the optical splitter 3, and these are constant values irrespective of the physical quantity of the sensor unit.

Therefore, when the signal processing device 6 performs a correction for obtaining a difference between the light receiving pulse 10 and the light pulse 9 obtained by passing through the optical attenuator 8 without passing through the sensor 2, as shown in FIG. Light pulses are obtained as a time-series pulse train. A physical quantity can be obtained from the magnitude of each light pulse.

Here, the optical physical quantity sensor detects a change in physical quantity as a digital change in light loss. When the sensor detection amount is a certain value or less, the optical loss is almost zero. Although the change in the amount of light transmitted through the sensor is small, it is assumed that when the detected amount of the sensor exceeds a certain value, the optical loss becomes maximum and the amount of transmitted light becomes zero. The operation of such a sensor means that the optical loss is maximized and the optical pulse is interrupted.

[0009]

The conventional optical fiber type multipoint physical quantity measuring system described above has the following problems.

(1) The optical pulse is cut off both when the sensor operates and the optical loss becomes maximum, and when a cutting failure occurs in the optical fiber, but the soundness of the optical fiber line is determined. If a transmission failure occurs in the transmission optical fiber or the reception optical fiber, the optical pulse farther from the failure point is interrupted, so it is erroneously determined that the sensor connected farther from the failure point has operated. I will.

(2) Since the soundness of the light source is not determined, if the light source fails, all the light pulses are cut off, so that it is erroneously determined that all the sensors have operated.

(3) In order to increase the number of sensors per system, since only one sensor is mounted between the optical splitters, the number of optical splitters arranged on the transmitting optical fiber and the receiving optical fiber is increased. Although it is necessary to increase the number, a branch loss due to the optical branching device increases and attenuation of the optical pulse increases, so that a low-loss system cannot be realized.

(4) To extend the measurement distance by increasing the number of sensors, it is necessary to add optical splitters to the transmitting optical fiber and the receiving optical fiber in the longitudinal direction of the sensor. Since the branch loss due to the optical branching device increases and the attenuation of the optical pulse increases, the measurable distance cannot be extended too long.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to make it possible to judge the soundness of the optical fiber line and the light source so that even if the optical fiber line breaks or the light source breaks down. Another object of the present invention is to provide an optical fiber type physical quantity measurement system capable of eliminating erroneous determination.

Another object of the present invention is to provide an optical fiber type physical quantity measuring system which has a small sensitivity and a high sensitivity by increasing the number of sensors by connecting a plurality of sensors in series.

It is another object of the present invention to provide an optical fiber type physical quantity measuring system which can greatly extend a measurable distance by blocking a sensor unit.

[0017]

According to a first aspect of the present invention, there is provided a sensor unit comprising a sensor connected between a transmission optical fiber and a reception optical fiber, the optical loss of which changes according to a change in a predetermined physical quantity. If, taken through the optical pulse generator for supplying an optical pulse to the transmitting optical fiber of the sensor unit, the reception optical fiber passes through the sensor via the transmitting optical fiber of the sensor unit from the optical pulse generator The receiver receives the received optical pulse and the optical pulse received by the
Data, extract arbitrary waveform data, and
Subtract background noise level from shape data
A signal processing device for determining strength and physical quantity, a failure detection optical fiber connected without passing through a sensor between the transmission optical fiber and the reception optical fiber of the sensor unit,
A signal processor for judging the soundness of the optical fiber or the failure of the optical pulse generator based on the presence or absence of the optical pulse received by the light receiver after passing through the failure detection optical fiber. It is.

According to a second aspect of the present invention, there is provided a sensor unit formed by connecting a plurality of sensors, whose optical losses change according to a change in a predetermined physical quantity, between a transmission optical fiber and a reception optical fiber in a ladder shape. and 1 block, a plurality of blocks arranged it in parallel, the optical pulse generator for supplying an optical pulse in blocks to the transmission optical fiber of each block, the transmitting optical fiber of each block from the optical pulse generator a photodetector receiving the light pulse in blocks through each sensor is taken out through the reception optical fiber of each block through the waveform data of the light pulses received by the said photodetector in the storage unit
Data, extract arbitrary waveform data, and
Subtract background noise level from data and calculate relative
And a signal processing device for obtaining intensity and physical quantity .

According to a second aspect of the present invention, there is further provided a fault detecting optical fiber connected between the transmitting optical fiber and the receiving optical fiber of each block without passing through a sensor, and passing through the fault detecting optical fiber. And a signal processing device for judging the soundness of the optical fiber or the failure of the optical pulse generator based on the presence or absence of the optical pulse received by the photodetector.

According to a third aspect of the present invention, in order to reduce optical loss,
A light receiver for receiving each light pulse from the receiving optical fiber of each block is separately provided.

[0021]

[0022]

[0023]

In a fourth aspect based on the first to third aspects, a plurality of sensors connected between a transmission optical fiber and a reception optical fiber are connected in series to facilitate monitoring of the sensors. It is something to do.

According to a fifth aspect of the present invention, the distance from the optical pulse generator to the end of the receiving optical fiber is set to L, the speed of light is set to C, and the refractive index of the optical fiber is set to n in order to effectively receive the light pulse. Sometimes, the interval between light pulses from the light pulse generator is 2 ·
The data is transmitted at a distance of L · n / C or more.

According to a sixth aspect of the present invention, in order to effectively receive light pulses, a pulse train length, L.n / C
A pulse specified in the pseudo random pulse train having the above is transmitted.

[0027]

In the first aspect of the invention, when a sensor is connected between the transmission optical fiber and the reception optical fiber, the light pulse passing through the sensor is affected by the sensor, and the sensor operates to minimize the optical loss. , The amount of light received by the light receiver that receives the light pulse becomes zero, and no light pulse is detected. The light passing through the sensor is also affected by the state of the optical fiber and the optical pulse generator itself . Even when the optical fiber is disconnected or the optical pulse generator is disconnected, no optical pulse is detected. Therefore, if the presence or absence of a light pulse passing through the sensor was detected, the sensor might have operated,
It cannot be determined whether the optical fiber has been disconnected or the optical pulse generator has been disconnected. However, if a failure detection optical fiber that does not pass through the sensor is connected between the transmission optical fiber and the reception optical fiber, the optical pulse passing through the failure detection optical fiber is not affected by the sensor and the optical fiber state Or only the state of the light pulse generator. Therefore, when the presence or absence of an optical pulse passing through the failure detection optical fiber is detected by the system soundness determination signal processing device, the system soundness determination signal processing device, when an optical pulse is detected, It is determined that the system is sound without an optical fiber disconnection failure or an optical pulse generator failure. Conversely, if no light pulse is detected, it is not caused by the operation of the sensor,
It is determined that either the optical fiber disconnection failure or the optical pulse generator failure has occurred and the soundness of the system has been impaired. As a result, when an optical pulse passing through the sensor is not detected because the soundness of the system is impaired, it is not erroneously determined that the optical pulse has operated. In addition, a failure detection optical fiber is
Be located at both the furthest and nearest positions
The soundness of the optical fiber and the sound pulse generator
Can be determined.

As in the second invention, a plurality of blocks each having a sensor connected between a transmitting optical fiber and a receiving optical fiber are arranged in parallel, and a transmitting optical fiber of each block is supplied from an optical pulse generator. If the optical pulses are supplied in units of blocks, and the optical pulses taken out via the receiving optical fiber of each block are received by the photodetector in units of blocks, the signals are transmitted as if the blocks were connected in series. Unlike the case where the number of sensor connection points connected to the trust optical fiber and the reception optical fiber increases by the unit of the block and the connection loss increases, if the number of sensor connection points per block is the same, Even if the number of blocks is increased, the number of sensor connection points on the transmitting optical fiber and receiving optical fiber viewed from the optical pulse generator does not increase, so that an increase in optical loss can be suppressed. . Therefore, if the blocks are connected in parallel, the number of installed sensors can be increased with low loss, and the sensors can be installed farther away.
Also, the position of the optical fiber for failure detection is farthest from the transmitting / receiving end.
And the closest position,
Determine both the integrity of the fiber and the integrity of the optical pulse generator.
Can be specified.

As in the second aspect of the present invention, if the system further includes the same failure detecting optical fiber and the system integrity signal processing device as in the first aspect, the system integrity can be determined. When an optical pulse passing through the sensor is not detected due to the unhealthyness of the sensor, it is not erroneously determined that the optical pulse has operated. Also, the failure detection optical fiber is farthest from the transmitting / receiving end.
By being placed at both the location and the closest location,
Both optical fiber health and optical pulse generator health
Can be determined.

As in the third invention, when light pulses from the receiving optical fiber of each block are received by the light receiver provided for each block, optical coupling is performed as in the case of receiving light by one light receiver. No means such as a vessel is required, and light loss due to those means can be suppressed.

[0031]

[0032]

[0033]

As in the fourth invention, when a plurality of sensors connected between a transmitting optical fiber and a receiving optical fiber are arranged in series and these sensor groups are treated as one group, When any of the sensors in the group operates, the operation can be determined by interrupting the light pulse passing through the group, so that sensor monitoring can be performed for each group. Further, since the number of sensors can be increased without increasing the number of sensor branch connections to the transmission optical fiber and the reception optical fiber, a system with high sensitivity and low loss can be configured.

As in the fifth invention, the light pulse from the light source is transmitted at an interval of 2 · L · n / C or more, or the pulse train length from the light source is 2 · L · n / C as in the sixth invention. By transmitting a pulse specified in a pseudo random pulse train having C or more, all light pulses can be effectively received.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a configuration diagram of an optical fiber type multipoint physical quantity measuring system of a transmission type time division system showing an embodiment of the present invention. This optical fiber type multi-point physical quantity measurement system
It comprises a sensor section A for obtaining optical data necessary for detecting a physical quantity, and a measuring section B for measuring a predetermined physical quantity from the optical data of the sensor section A and determining the soundness of the system.

The sensor section A includes a transmitting optical fiber 1a and a receiving optical fiber 1b arranged in parallel, and a plurality of optical splitters 3 provided at predetermined intervals in the middle of the two optical fibers 1a and 1b. , An optical physical quantity sensor 2 connected between a pair of optical splitters 3 arranged at respective positions of both optical fibers 1a and 1b. Optical physical quantity sensor 2
Are connected in series between the optical splitters 3, a plurality of series circuits connected in series form one group, and M groups are provided in the longitudinal direction of both optical fibers 1a and 1b. .

The optical pulse between the optical splitters 3 does not pass through the optical physical quantity sensor 2 between the optical splitters 3 closest to the transmitting / receiving ends of the two optical fibers 1a and 1b and the farthest positions. They are directly connected by a generator failure detection optical fiber 12a and an optical fiber failure detection optical fiber 12b.

The optical loss of the optical physical quantity sensor 2 changes digitally in response to changes in physical quantities such as temperature, humidity, and liquid leakage.

The measuring section B includes an optical pulse generator 4 for supplying an optical pulse to the transmitting optical fiber 1a of the sensor section A, and a light receiving section for receiving the optical pulse from the receiving optical fiber 1b of the sensor section A and performing photoelectric conversion. Device 5, a signal processing device 6 for measuring a predetermined physical quantity in the optical physical quantity sensor 2 based on a change in the light intensity of the light receiving pulse of the light receiving device 5, and an optical pulse generator failure obtained through the signal processing device 6. Optical fiber for detection 1
2a and a signal processor 13 for judging the soundness of the system based on the presence / absence of a received light pulse having passed through the optical fiber 12b for detecting an optical fiber failure. The optical fiber 12a for detecting a failure of the optical pulse generator connected to the position closest to the transmitting / receiving ends of the optical fibers 1a and 1b is built in the measuring unit B in order to increase the accuracy of determination.

The light pulse generated by the light pulse generator 4 is
An optical pulse component that enters the transmission optical fiber 1a, is branched by the optical splitter 3 provided on the way, and propagates as it is in the longitudinal direction of the transmission optical fiber 1a,
It is divided into an optical pulse component that branches and propagates to the b side.

The optical pulse branched and propagated to the receiving optical fiber 1b side passes through the optical physical quantity sensor 2 installed in this portion, passes through the optical splitter 3 and the receiving optical fiber 1b. The light is guided to the light receiver 5. The signal obtained after the photoelectric conversion by the light receiver 5 is a time-series signal of an optical pulse delayed in the order of increasing distance from the sensor near the transmitting / receiving end based on the delay time corresponding to the position of each optical splitter 3. Becomes This is shown in FIG. The first light receiving pulse i = 1 is a pulse that has returned after passing through the optical fiber 12a for detecting a failure of the optical pulse generator, and the last light receiving pulse i
= N is a pulse returned after passing through the optical fiber failure detecting optical fiber 12b. Each light receiving pulse level is detected at a level sufficiently higher than the background noise level.

The light pulse thus obtained by the light receiver 5 is supplied to the signal processing device 6. In the signal processing device 6, as shown in FIG. 3, the light pulse received by the light receiver 5 is stored in the storage unit as waveform data (step 21).
The second optical pulse waveform data can be arbitrarily extracted (step 22). The background noise level is subtracted from the extracted i-th optical pulse waveform data to determine the relative intensity and physical quantity (step 23). Then, as shown in FIG. 4, the optical physical quantity sensor levels of the groups 1 to M are displayed (step 24).

At this time, the signal processing device 13 for soundness determination
Then, i = i = 1 = i = i = i = i = i
The first and i = n-th optical pulse waveform data are fetched, and the soundness of the optical pulse generator 4 is evaluated based on the presence / absence of the i = 1st optical pulse (step 26). If the waveform is not detected and the soundness of the optical pulse generator 4 cannot be evaluated, it is determined that the optical pulse generator 4 is broken, and the alarm output of the signal processing device 6 is activated (step 2).
5).

If the light pulse is detected and the soundness of the light source can be evaluated, the i = n-th light pulse waveform data of the i = n-th light pulse data that has passed through the optical fiber The soundness of the transmission optical fiber and the reception optical fiber is evaluated based on the presence / absence (step 2).
7). Here, if the waveform is not detected and the soundness of the light source cannot be evaluated, it is determined that the transmission optical fiber 1a or the reception optical fiber 1b is disconnected in the middle, and the alarm output of the signal processing device 6 is activated. (Step 25). If the waveform data is detected and the soundness of the optical fiber can be evaluated, the process proceeds to step 23 for calculating the physical quantity described above.

For example, FIG. 5 shows the relative intensities of the light pulses obtained when any of the sensors in group 3 operates. In this case, the soundness of the system is determined by the signal processing device for soundness determination 13 because the i = 1st and i = nth light pulses are emitted. Based on this determination, the light pulse does not return from the known position of group 3, so that the sensor operation of group 3, that is, the sensor detection amount exceeds a certain value due to a change in the physical amount, the light loss becomes maximum, and the light It can be confirmed that the pulse has been interrupted.

FIG. 6 shows the relative strength obtained when an optical fiber line failure occurs between group 2 and group 3. Since the i = 1st optical pulse is emitted, the soundness of the optical pulse generator 4 is determined by the soundness determination signal processing device 13. However, since the i = n-th pulse does not return, the soundness determination signal processing device 13 determines the occurrence of an optical fiber failure. Therefore, it is possible to avoid erroneous determination that all the sensors of the group 3 and thereafter have operated.

As described above, the optical fiber generator 12a and the optical fiber failure detecting optical fiber 12a are located at the nearest and farthest positions of the transmitting and receiving ends of the transmitting optical fiber 1a and the receiving optical fiber 1b, respectively. 12b to detect the presence or absence of an optical pulse passing through each of the optical fibers 12a and 12b, and immediately determine the soundness of the optical pulse generator 4, the transmitting optical fiber 1a and the receiving optical fiber 1b. Therefore, when a predetermined light pulse is not detected, it is possible to configure a highly reliable system without erroneously determining that a predetermined light pulse has been operated.

In this embodiment, the transmission optical fiber 1
a and a plurality of sensors 2 connected in series between the receiving optical fiber 1b and the receiving optical fiber 1b. For example, in a configuration having n sets of branches, in a form in which one sensor is attached between one set of branches, n pieces of sensor information can be managed.
However, if m sensors are arranged in series per branch,
Although the management number of the sensor information is the same as n, the sensor information is viewed from a maximum of n × m. Therefore, the effect of arranging a plurality of sensors in series is that the number of attached sensors per system can be increased and physical quantities can be detected with high sensitivity. A specific example that can exhibit this effect is a plurality of plant managements. Each plant is provided with an optical physical quantity sensor, which monitors the state of the plant. When trying to manage n plants with a system having n sets of branches, in a configuration in which one sensor is attached per branch, each plant can monitor only one sensor. On the other hand, in a configuration in which m sensors are attached in series, it is not possible to determine which of the m sensors has operated, but monitoring by m sensors per plant is possible.

Next, FIG. 7 shows another embodiment in which the number of sensors is similarly increased, but the sensors are not grouped and arranged with high sensitivity, but are arranged in blocks so that they can be arranged remotely. Will be explained.

A sensor section A constituted by connecting the sensor 2 between the transmitting optical fiber 1a and the receiving optical fiber 1b is formed as one block, and n blocks are arranged in parallel in the longitudinal direction of the optical fiber. Correspondingly, a 1: n optical branching unit is connected to the optical pulse generator 4 of the measuring unit B, and the optical pulse generated from the optical pulse generator 4 is branched into 1: n, and is branched into n. The supplied light is supplied to the transmission optical fibers 1a of the n blocks arranged in parallel. Also, the light receiver 5 includes
1: n optical couplers are connected, and optical pulses in block units from the transmission optical fiber 1b of each block returned through each physical quantity sensor 2 are coupled into n: 1, and this is coupled to the optical receiver 5. Receive light. Note that the optical splitter 14 may be an optical switch, and the optical pulse may be distributed to the transmission optical fiber 1a of each block by n and supplied by switching. Alternatively, the optical coupler 15 may be an optical switch, and one group of optical pulses may be selected from the n groups by switching, and may be received by the optical receiver 5.

As described above, by blocking the sensor section A,
If a parallel block system in which a plurality of the sensors are arranged in parallel and connected to the measuring unit B is adopted, it is possible to install a sensor to a distant place and perform high-sensitivity measurement. That is, the increase in the loss to a distant sensor has two meanings. One is simply an increase in transmission loss due to the length of the fiber transmission line itself, and the other is an increase in loss due to an increase in the number of optical splitters on the way. According to the embodiment of FIG. 7 as well, the number of installed sensors is limited by the increase in transmission loss of the fiber transmission line due to the lengthening. However, if a 1: n splitter and a 1: n coupler are provided, even if the number of blocks is increased, Since the number of optical splitters does not increase, the number of sensors that can be installed can be greatly increased and sensors can be installed far away compared to the case of a series system in which blocks are simply connected in series and therefore the number of optical branches increases. Becomes

In FIG. 7, a plurality of sensors connected between the transmitting optical fiber and the receiving optical fiber may be connected in series to form a group. The optical fiber for optical pulse generator failure detection and the optical fiber for optical fiber failure detection described above may be connected, and the measurement unit B may be provided with a signal processing device for system soundness determination.

FIG. 8 shows the configuration of FIG. 7 in which the sensors are arranged at regular intervals at a wavelength of 1.5 μm of the light pulse generated from the light-emission pulse generator and at a distance of 0.1 km between the sensors. At 70 dB, the total detectable distance when the number of blocks is increased (= the total number of sensors × 0.1 k)
m) shows that as the number of blocks increases, the total detectable distance also increases.

In the above embodiment, the optical fiber for detecting an optical fiber failure is attached to the last stage.
A similar optical fiber failure detecting optical fiber may be connected at a predetermined interval in the middle stage. This makes it possible to determine in which section the optical fiber disconnection occurs.

FIG. 9 shows a modified example of the system shown in FIG. The optical pulse generator side has the same configuration,
The optical receiver side does not use an optical coupler that couples optical pulses into 1: n or an optical switch that selects one out of n by switching. Instead, n optical receivers with the same number of blocks are prepared. , N-blocks are received by the respective light receivers 5-1, 5-2,..., 5-n. As a result, it is possible to suppress branch loss when using an optical coupler on the optical receiver side or coupling loss when using an optical switch, and to achieve higher sensitivity measurement or extend the total detectable distance. it can.

Further, the pulse train generated from the optical pulse generator may be of a single pulse type or a pseudo random type. In other words, in order to enable the optical pulse at intervals so that the transmitted optical pulse and the received optical pulse do not overlap, in the single pulse system, the branch and the optical pulse generator located farthest from the light source are used. Is the distance of L,
When the high speed is C and the refractive index of the optical fiber is n, the light pulse from the optical pulse generator is transmitted at an interval of 2 · L · n / C or more. In the pseudo-random method, a pulse specified in a pseudo-random pulse train having a pulse train length of 2 · L · n / C or more is transmitted. When the pseudo-random method is used, it is necessary to add a function of demodulating a pseudo-random signal as a function of the signal processing device.

[0058]

According to the first aspect of the present invention, it is possible to determine whether an optical fiber failure or an optical pulse generator failure has occurred by providing a failure determination optical fiber and a system soundness determination signal processing. As a result, a highly reliable system can be constructed. Also, the optical fiber for failure detection
Transmission and reception between the transmitting optical fiber and the receiving optical fiber
Since it is located closest to the edge, the state of the optical pulse generator
Optical pulse generator failed because the soundness of
Erroneously determines that all sensors have operated.
Disappears. According to the second aspect of the present invention, a plurality of blocks each configured by connecting a sensor between a transmission optical fiber and a reception optical fiber are arranged in parallel, and an optical pulse is transmitted to the transmission optical fiber of each block. Is supplied in block units, and light pulses taken out from the receiving optical fiber of each block are received in block units, so that each block is connected in series to supply light pulses to a series,
Alternatively, unlike the series, the number of sensor connections on the transmitting optical fiber or receiving optical fiber does not increase even if the number of blocks is increased, so the number of installed sensors can be increased without increasing optical loss. The measurable distance can be extended.

According to the second aspect of the present invention, the system in which the sensor units are block-connected and arranged in parallel is also provided with the optical fiber for failure detection and the signal processing device for system soundness judgment, and is provided with an optical fiber failure or an optical fiber failure. Since it is possible to determine whether or not a pulse generator failure has occurred, a highly reliable system can be constructed. Also, the optical fiber for failure detection
Transmission and reception between the transmitting optical fiber and the receiving optical fiber
Since it is located closest to the edge, the state of the optical pulse generator
Optical pulse generator failed because the soundness of
Erroneously determines that all sensors have operated.
Disappears.

According to the third aspect of the present invention, the light pulse from the receiving optical fiber of each block is received by the light receiver provided for each block. As described above, a unit such as an optical branching coupler is not required, and light loss due to those units can be suppressed, so that the measurable distance can be further extended.

[0061]

[0062]

[0063]

According to the fourth aspect of the present invention, since a plurality of sensors connected between the transmission optical fiber and the reception optical fiber are arranged in series, the transmission optical fiber or the reception optical fiber is arranged. Since the number of sensors can be increased without increasing the number of connections to fibers, a low-loss, high-sensitivity system can be configured.

According to the fifth aspect of the present invention, since the light pulses are transmitted at a distance of 2 · L · n / C or more from the light source, all the light pulses can be received effectively.

According to the sixth aspect of the present invention, the pulse specified by the pseudo random pulse train having a pulse train length of 2 · L · n / C or more is transmitted from the light source.
All light pulses can be received effectively.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of an optical fiber type multipoint physical quantity measurement system of the present invention.

FIG. 2 is an explanatory diagram of a received pulse waveform measured by the optical fiber type multipoint physical quantity measuring system of the present invention.

FIG. 3 is a conceptual flowchart illustrating functions of a signal processing device and a soundness determination processing device according to the present embodiment.

FIG. 4 is an explanatory diagram of a received pulse waveform after calculation obtained by the signal processing device of the optical fiber type multipoint physical quantity measurement system according to the present embodiment.

FIG. 5 is an explanatory diagram of a received pulse waveform after calculation obtained by the signal processing device of the optical fiber type multipoint physical quantity measuring system according to the present embodiment, and is a diagram when a sensor of group 3 operates. .

FIG. 6 is an explanatory diagram of a calculated received pulse waveform obtained by the signal processing device of the optical fiber type multipoint physical quantity measurement system according to the present embodiment, wherein a failure occurs in a line between group 2 and group 3; It is a diagram when it occurs.

FIG. 7 is a configuration diagram showing another embodiment of the optical fiber type multipoint physical quantity measurement system of the present invention.

FIG. 8 is an explanatory diagram showing the relationship between the number of blocks obtained by another embodiment shown in FIG. 7 and the total detectable distance.

FIG. 9 is a configuration diagram showing a modification of the other embodiment of FIG. 7;

FIG. 10 is a configuration diagram of a conventional optical fiber type multipoint physical quantity measurement system.

FIG. 11 is an explanatory diagram of a received pulse waveform measured by a conventional optical fiber type multipoint physical quantity measuring system.

FIG. 12 is a reception pulse waveform after calculation obtained by a conventional signal processing device.

[Explanation of symbols]

 A Sensor section B Measurement section 1a Optical fiber 1b Optical fiber 2 Optical physical quantity sensor 2a Optical physical quantity sensor 2b Optical physical quantity sensor 3 Optical splitter 4 Optical pulse generator 5 Optical receiver 5-1 Optical receiver 5-2 Optical receiver 5 -N Optical receiver 6 Signal processing device 12a Optical fiber for failure detection of optical pulse generator 12b Optical fiber for failure detection of optical fiber 13 Signal processing device for system soundness determination 14 1: n branching device 15 1: n coupler

──────────────────────────────────────────────────続 き Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI G08C 25/00 G08C 25/00 K Examiner Nobuhiro Higuchi (56) References JP-A-4-313026 (JP, A) JP-A Heisei 8-101992 (JP, A) JP-A-5-336042 (JP, A) JP-A-3-9625 (JP, A) JP-A-3-4147 (JP, A) JP-A-5-45250 (JP, A A) JP-A-57-127294 (JP, A) JP-A-62-57096 (JP, A) JP-A-56-58627 (JP, A) JP-A-63-113323 (JP, A) −117929 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01D 21/00 G02B 6/00 G08C 25/00

Claims (6)

(57) [Claims] 1. A sensor unit comprising a sensor connected between a transmission optical fiber and a reception optical fiber, the optical loss of which changes according to a change in a predetermined physical quantity, and a transmission optical fiber of the sensor unit. receiving the optical pulse generator for supplying optical pulses, the optical pulses to be extracted via the reception optical fiber passes through the sensor via the transmitting optical fiber of the sensor unit from the <br/> optical pulse generator light and light receiver, received by the said photodetector
The pulse is stored in the storage unit as waveform data, and any waveform
Data is extracted and background noise is extracted from the waveform data.
A signal processing device for determining the relative strength and physical quantity by subtracting the Izureberu, when connected Ru without going through the sensor between the reception optical fiber and transmitting optical fiber of the sensor portion
Both transmitting and receiving ends of the transmitting optical fiber and the receiving optical fiber
Located farthest from
Is a fault detection optical fiber, a fault or determining system integrity determine the presence or absence of failure in the optical pulse generator of the optical fiber from the presence of optical pulses through the fault detection optical fiber is received by the light receiver Fiber type physical quantity measurement system provided with a signal processing device for use. 2. A plurality of light loss changes according to a change of a predetermined physical quantity between the transmission optical fiber and the receiving optical fiber
A plurality of blocks in which a sensor unit configured by connecting the sensors in a ladder shape is configured as one block,
And optical pulse generator for supplying an optical pulse in blocks to the transmission optical fiber of each block passing through each sensor via a transmitting optical fiber of each block from the optical pulse generator receiving optical fiber for each block a light receiver for receiving in blocks light pulses taken out through the storage of light pulses received by the said photodetector as the waveform data in the storage unit
And extract arbitrary waveform data, and
The relative noise and physical
A signal processing device for determining the amount, and for transmitting each block
Via a sensor between the optical fiber and the receiving optical fiber.
Connected without transmitting and receiving optical fiber.
The farthest position from the transmitting / receiving end to the fiber and the closest position
And a failure detection optical fiber respectively arranged at
Light received by the above receiver after passing through the optical fiber for fault detection
Failure or light pulse onset production of optical fiber from the presence or absence of a pulse
Signal processing for system soundness determination to determine the presence or absence of a failure
Fiber-optic physical quantity measurement system equipped with a physical device . 3. An optical fiber type object according to claim 1 or 2.
In the physical measurement system, the above-mentioned light receiver is
The installed optical fiber type physical quantity measurement system. 4. The transmission optical fiber and the reception optical fiber.
Multiple sensors connected in series
The optical fiber type physical quantity measurement system according to claim 1, wherein: 5. An optical fiber for receiving from the optical pulse generator.
Is the distance to the terminal, L is the speed of light, C is the refractive index of the optical fiber
Where n is the distance between light pulses from the light pulse generator
Are transmitted at a distance of 2 · L · n / C or more.
The optical fiber type physical quantity measurement system according to claim 1 . 6. An optical fiber for receiving from the optical pulse generator.
Is the distance to the terminal, L is the speed of light, C is the refractive index of the optical fiber
Where n is the pulse train length from the optical pulse generator 2
.Specified as a pseudo-random pulse train having L.n / C or more
2. A pulse according to claim 1, wherein
5. The optical fiber type physical quantity measurement system according to any one of 4 .