JPH0337535A - Multipoint-pressure measuring method - Google Patents

Abstract

PURPOSE:To make it possible to measure the pressures at many points in a short time by using optical fibers whose transmitting parameters are changed in response to the pressures as pressure sensors and transmitting paths. CONSTITUTION:Pressure detecting optical fibers S1 - Sn are optically linked with optical fiber 12, and a sensor part is constituted. An optical-pulse generating part 1 generates an optical pulse having a constant intensity and a constant pulse width in response to timing from a timing control part 9. The optical pulse passes through a half mirror 11 and enters into one end of the fiber 12. The returned light from the fiber 12 is reflected with the mirror 11 and guided into a light receiving part 2. The light receiving part 2 receives the returned light and generates the signal in response to the light intensity. An A/D converter 3 converts the signal into the digital code. The codes are sequentially written into a memory 4. A time counter 5 sequentially generates writing addresses for the memory. Thus, the returned intensity data train with the elapse of time from the emission of the optical pulse is obtained in the memory 4.

Description

DETAILED DESCRIPTION OF THE INVENTION 0) Summary of the Invention The multi-point pressure measurement method according to the present invention measures the pressure at many points, for example, when measuring the water pressure at multiple points on a fishing net to determine the spread of the fishing net. This is particularly effective when measuring substantially simultaneously.

(C) Conventional technology In general, as a method of objectively determining the spread of a fishing net such as a purse seine, water pressure gauges are attached to specific points on the fishing net in advance, and the condition of the fishing net is determined based on the measurement results of each water pressure gauge. has been devised.

For example, in the case of a purse net, as shown in FIG. 5, water pressure gauges P1 to P4 are attached at a plurality of places on the lower edge of the purse net. Each water pressure gauge is equipped with a transmission circuit that transmits measurement results to the host side using ultrasonic waves. In this way, on the host side, the water depth at the position where the water pressure gauge was attached to the purse seine was determined based on the measurement results of each water pressure gauge, and the extent of the overall spread of the purse seine was ascertained.

(d1 Problem to be Solved by the Invention) However, in such conventional methods, a water pressure gauge must be placed at each position where pressure is to be measured.In addition, it is necessary to host the measurement data of such multiple water pressure gauges. A special data transmission system must be constructed in order to selectively receive the data individually at the side, which makes it difficult to measure the pressure at too many measurement points at the same time.

An object of the present invention is to provide a multi-point pressure measurement method that can measure pressure at a large number of locations in an extremely short time without providing a special active circuit for each location where pressure is to be measured. A multipoint pressure measurement method according to claim (1) of the present invention includes the steps of: Injecting a light pulse from one end of an optical fiber whose transmission parameters change depending on the pressure; It is characterized by receiving the return light from the optical fiber, and determining the pressure at each position of the optical fiber based on changes in the return light due to changes in transmission parameters and the elapse of time from the input of the optical pulse to the reception of the return light. There is.

Further, in the multi-point pressure measurement method according to claim (2) of the present invention, a plurality of pressure detection optical fibers whose transmission parameters change depending on pressure are connected by using other optical fibers whose transmission parameters change little due to pressure. They are optically connected to form an optical transmission line, and a light pulse is input from one end of the optical transmission line, and the return light from the pressure detection optical fiber is received, and the return light is determined by changes in the transmission parameters. The present invention is characterized in that the pressure in each of the pressure detection optical fibers is determined based on the change and the elapse of time from the input of the optical pulse to the reception of the returned light.

(f1 action In the multi-point pressure measurement method according to claim (1), an optical fiber whose transmission parameters change depending on the pressure is used as a pressure sensor and as a transmission line. As scattering occurs in various parts,
Changes in pressure cause changes in, for example, the amount of light transmitted through the fiber. In accordance with this change, the amount of transmitted scattered light returning to the light incident side of the fiber changes. In this way, when the intensity of the returned light changes depending on the pressure, the pressure can be determined by measuring the intensity of the returned light. In addition, the distance from one end of the optical fiber to the point where scattering has occurred within the optical fiber can be determined by determining the time elapsed from the time when the optical pulse enters the optical fiber until the arrival of the returned light. The pressure at can be found.

Furthermore, in the multi-point pressure measurement method according to claim (2), an optical fiber whose transmission parameters change according to pressure is used as a pressure detection optical fiber, and this pressure detection optical fiber is used to measure pressure. For example, a single optical fiber transmission line is constructed by arranging the pressure detection optical fibers at different locations and optically connecting the pressure detection optical fibers with optical fibers whose transmission parameters change little due to pressure.

If the pressure detection optical fiber is one in which, for example, the amount of light transmitted changes due to pressure, a light pulse input from one end of the optical transmission line is scattered at various parts of the optical fiber transmission line, and The scattered light is attenuated in accordance with the pressure within the pressure detection optical fiber and returns to the light incident side of the transmission path. In this way, when the intensity of the returned light changes depending on the pressure, the pressure can be determined from the intensity of the returned light, and the returned light attenuates as the time elapses from the time the optical pulse enters the transmission line until it is received. The position of the detection optical fiber that caused the problem can be determined, and thereby the pressure at each measurement point can be determined.

The time required from the input of the optical pulse to the optical fiber or optical transmission line to the reception of all the returned light is extremely short, and furthermore, it is necessary to provide a device at each measurement point to transmit the measurement take. Instead, it becomes possible to instantaneously measure pressure at an extremely large number of points simply by placing optical fibers or optical transmission lines at pressure measurement locations.

+g) Example A block diagram of a multi-point pressure measuring device which is an example of the present invention is shown in FIG. This device consists of a sensor section placed at a location where pressure is to be measured, and a control section connected to this sensor section. In FIG. 1, Sl, 32. S3. S4. S5
．． ...Sn is an optical fiber for pressure detection whose transmission parameters change depending on the pressure, for example, the wavelength is 0.6.
It is possible to use a so-called pressure-sensitive rubber optical fiber in which a core with a high refractive index made of silicone rubber that transmits infrared light of 8 μm is provided in the clathode layer. The sensor section is constructed by optically connecting these pressure detection optical fibers in series through an optical fiber 12 whose transmission parameters change little due to pressure.

In the control section, the optical pulse generating section 1 is constituted by a pulse laser generating device or the like, and generates an optical pulse having a constant intensity and a constant pulse width in response to a timing signal (start pulse) from the Thai blowfish control section 9. The reference clock generation section 10 provides a reference cross signal to the blowfish control section 9. 1) is a half mirror, through which the optical pulse passes and enters from one end of the optical fiber 12. optical fiber 12
The returning light is reflected by the half mirror 1) and guided to the light receiving section 2. The light receiving section 2 receives the returned light and generates a signal corresponding to the intensity of the returned light. The AD converter 3 converts this into a digital code and sequentially writes it into the memory 4. The time counter 5 starts counting from the start pulse output from the timing control section 9, and sequentially generates memory write addresses. In this way, the intensity data string of the returned light over time from the emission of the light pulse is stored in the memory 4.
to ask.

Here, after a light pulse is input from one end of the optical fiber by the light pulse generator 1, the intensity of the returned light received by the light receiver 2, that is, the change in scattering intensity over time is expressed as follows.
The result is as shown in FIG.

Since Rayleigh scattering and the like occur in the optical fiber 12 that connects the pressure detection optical fibers, the amount of light received as a whole decreases over time. In each pressure detection optical fiber, the amount of attenuation of light is determined depending on the pressure it receives, and in the figure el, e2. e3...en are attenuations caused by the pressure detection optical fibers 81 to Sn shown in FIG.

Now, the calculation unit 6 shown in FIG. 1 reads out the data in the memory 4 based on the calculation start signal output from the timing control unit 9, and uses the change in the intensity of the amount of received light over time to determine the amount of light in each pressure detection optical fiber. The amount of attenuation of is determined, and from this, the pressure exerted by each pressure detection optical fiber is determined. In calculating the light attenuation rate in each pressure detection optical fiber, as can be understood from the characteristic curve shown in Fig. 2, it is determined depending on the distance from the optical pulse generating part.
Needless to say, attenuation correction by the optical fiber 12 is necessary. Such attenuation correction is similar to techniques used in fields such as radar and ultrasonic sonar.

Further, the calculation section 6 further converts the pressure of the pressure detection optical fiber into a predetermined unit and writes the data into the display memory in the display control section 7. The display control section 7 generates a display signal from the contents of the display memory, and displays the pressure in each pressure detection optical fiber on the display section 8.

FIG. 3 shows an example in which the multi-point pressure measuring device described above is applied to a purse net. In FIG. 3, reference numeral 13 denotes a pressure detection control section provided at one end of an optical transmission path consisting of pressure detection optical fibers 81 to Sn and optical fibers connecting these. A buoy 15 is connected to this pressure detection control section I3 via a cable 14. Pressure detection control section 13
The configuration is the same as that of the control section shown in FIG. 1 except that it includes a data transmission control section for the buoy 15. The buoy 15 wirelessly transmits the pressure data of each pressure detection optical fiber received via the cable 14 to the fishing boat using the antenna 16. This allows fishing boats to accurately grasp the spread of the purse seine. Note that the pressure data of each pressure detection optical fiber may be directly transmitted from the control unit 13 by ultrasonic waves or the like.

In the embodiments described above, an optical transmission path in which a plurality of pressure detection optical fibers are connected by ordinary optical fibers is used as the sensor section, but the entire sensor section may be constructed from pressure detection optical fibers. The main parts of an example of the configuration are shown in FIG. In FIG. 4, reference numeral 17 denotes a pressure detection optical fiber whose transmission parameters change depending on the pressure, and for example, the so-called pressure-sensitive optical fiber described above can be used. A control section that makes a light pulse enter such a single pressure detection optical fiber and receives the returned light can have the same configuration as the control section shown in FIG. 1. However, in this case, when calculating the pressure at each point of the optical fiber from the intensity data string of the return light over time from the emission of the optical pulse, the return light generated by Rayleigh scattering of the pressure detection optical fiber itself is Attenuation correction is performed according to the distance from the pulse generator.

fh) Effects of the Invention According to the present invention, a pressure detection optical fiber or an optical transmission line having a pressure detection optical fiber in the middle is arranged at a place where pressure is to be measured, and a light pulse is emitted and received at one end. By simply providing a control unit that performs control, it becomes possible to measure pressures at many locations in a short time. For example, if this is applied to measuring the pressure in each part of a fishing net, it becomes possible to accurately grasp the state of the fishing net in the sea.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a multi-point pressure measuring device according to an embodiment of the present invention. FIG. 2 is a diagram showing signal changes of the light receiving section in the same device. FIG. 3 is a diagram showing an example of application to a winding net. FIG. 4 is a diagram showing the main parts of a multipoint pressure measuring device according to another embodiment. FIG. 5 is a diagram showing a conventional multi-point pressure measurement method. 1) - Half mirror - 12 - Optical fiber, 31 - Sn. 7 Optical fiber for pressure detection.

Claims (2)

[Claims] (1) A light pulse is input from one end of an optical fiber whose transmission parameters change depending on the pressure, and the return light from the optical fiber is received, and the return light changes due to the change in the transmission parameter and the light pulse is input. A multi-point pressure measurement method characterized by determining the pressure at each position of an optical fiber based on the elapse of time from light to reception of returned light. (2) A plurality of pressure detection optical fibers whose transmission parameters change according to pressure are optically connected by other optical fibers whose transmission parameters change little due to pressure to form an optical transmission line, and this optical transmission A light pulse is input from one end of the path, and the return light from the pressure detection optical fiber is received, and the return light changes due to a change in the transmission parameter, and the time elapsed from the input of the light pulse to the reception of the return light. A multi-point pressure measurement method, characterized in that the pressure in each of the pressure detection optical fibers is determined by: