JPS6382320A - Optical fiber sensor apparatus - Google Patents

Abstract

PURPOSE:To detect the change in the physical state of a plurality of terminals by one optical main path by efficiently collecting sensor informations expanding in planar and linear state, by utilizing the wide-band property of an optical fiber and arranging a large number of sensor heads to one optical main path of a data highway. CONSTITUTION:The light pulse from a light transmitter 2 is transmitted by the optical main path due to one optical fiber of a system and branched to a receiving optical path 5 by the directional coupler 4 connected to the optical main path 3. The light pulse passing through the coupler 4 is transmitted to respective directional couplers 11a-11n by the optical main path 3 to be branched to respective branched optical paths 11a-11n. The branched light pulses are respectively supplied to optical sensors due to electro-optical crystals 13a-13n through the paths 11a-11n and directional couplers 12a-12n. Then, sensor informations expanding in planar and liner states are efficiently collected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention supplies optical pulses to a plurality of optical sensors attached to a device under test using optical fibers, receives sensor information, and performs various operations. The present invention relates to an optical fiber sensor device that obtains measurement results.

[Conventional technology]

Optical fiber sensors have many features such as low loss, broadband, non-induction, and insulation properties, so their future potential is attracting attention. One type of optical fiber sensor is one in which the amount of optical power transmitted changes depending on physical stimuli such as electric field, magnetic field, pressure, temperature, etc. For example, photovoltage and ammeters using the Pockels effect and Faraday effect are of this type (see, for example, Japanese Patent Publication No. 60-51689 and Japanese Patent Publication No. 60-51690).

Conventionally, when measuring information from multiple sensors using optical fibers, in order to obtain information from optical sensors located at different distances, it is necessary to use optical fibers such as laser diodes to connect the optical sensors attached to each device under test. The optical power transmitted from the transmitter is sent to the optical sensor through the transmission line,
A measurement signal from the optical sensor is received by an optical receiver through a reception line to obtain information about the optical sensor.

[Problem that the invention seeks to solve]

However, since a transmission line and a reception line are connected to each of the plurality of optical sensors, and an optical transmitter or optical receiver is individually provided to each of these lines, When connecting a transmitting line or a receiving line, it was difficult to identify which device was connected, and the devices were congested.

SUMMARY OF THE INVENTION An object of the present invention is to solve these conventional problems and to transmit and receive information from a plurality of optical sensors located at remote locations using two optical fiber transmission lines.

[Means for solving problems]

In order to achieve this object, the optical fiber sensor device of the present invention includes an optical frame line consisting of one optical fiber that transmits optical pulses output from an optical transmitter, and at least one optical frame line branched from the optical frame line. A directional coupler is connected to the optical branch line, and optical fibers of different lengths are connected to the input side and the output side of the directional coupler, respectively. It is characterized in that its ends are optically connected to both ends of an optical sensor whose transmitted amount of optical power changes in response to external physical or electromagnetic stimulation.

[Effect]

The optical fiber sensor device of the present invention makes good use of the broadband properties of optical fibers, and has many sensor heads arranged on a single optical frame line called a data highway, so that sensor information can be distributed both in-plane and across the contract. This is a system that efficiently collects information.

As the multiplexing method by multiplexing optical pulses, single-line and two-wire systems using a transmission type sensor, and one-line type using a reflection type sensor have been proposed.

In the present invention, optical pulses transmitted from an optical transmitter are branched and transmitted to respective optical sensors attached at different distances, and a measurement signal from each optical sensor is transmitted. is transmitted to the optical frame line, and the position of the optical sensor is specified based on the time difference in arrival of the optical halus received from the optical frame line to the optical receiver, and a measurement signal is obtained from the waveform of the optical pulse.

〔Example〕

Hereinafter, the present invention will be specifically described based on embodiments shown in the drawings.

FIG. 1 shows an embodiment of the present invention. In FIG. 0, 1 is an electric pulse generator, 2 is an optical transmitter such as a laser diode that converts electric pulses into optical pulses and sends them out, and 3 is an optical fiber. This is a light frame line using. Reference numeral 4 denotes a directional coupler connected to the optical frame line 3, which branches the received optical pulse passing through the optical frame line 3 to the receiving optical line 5.

6 is an optical receiver, 7 is an amplifier, 8 is a signal processing device, 9 is a display device, 10a, 10b, . . . Ion is an optical frame line 3
Directional coupler connected to lla, llb,...
lln is a branch optical line made of optical fiber, 12a, 12
b,...12n are directional couplers, 13a, 13b
, . . . 13n is an optical sensor such as an unbalanced chef-diode. These optical sensors include, for example, polarizers 13az, 13as, 13bz, on both end faces of electro-optic crystals 13a+, L3b+, . . . 13n1.
13bz.

...13nz and 13ns are provided, and are attached to a device under test (not shown) to detect the state of voltage, current, magnetic field, etc. in the device under test. Further, the optical sensor is connected to one end of the directional couplers 12a, 12b, . . . 12n via optical paths 14a, 14b, . is connected to the optical line 14a using an optical fiber at the other end.
, 14b,...14n length 12 is Δl longer than 11
Optical lines 15a, 15b, . . . 15n are connected.

Electric pulses generated by the pulse generator 1 are converted into optical pulses by the optical transmitter 2 and sent to the optical frame line 3.

This optical pulse is transmitted to each directional coupler 10a, 10
b, . . . branched at 10n to form branch optical lines 11a, ll
b, ...lln, and the directional couplers 12a, 12
b.

...Sent to 12n.

Now, the optical pulse received by the directional coupler 12a is branched into two by the directional coupler 12a, and transmitted to the respective optical lines 14a and 15a. When the optical pulse passing through the optical path 14a reaches the optical sensor 13a, a part of the optical pulse hits the optical sensor and is reflected, and is transmitted to the optical path 14a as a reflected light optical pulse, and the remaining part passes through the optical sensor. The transmitted light becomes a light pulse and is transmitted to the optical path 15a.

Since the optical path 15a is longer than the optical path 14a by Δl, the optical pulse of the reflected light that passes through the optical path 14a is delivered to the directional coupler t time earlier than the optical pulse of the transmitted light that passes through the optical path 15a. 12a, branch optical line 11
a, the signal passes through the directional coupler 10a, the optical frame line 3, is branched at the directional coupler 4, and is sent from the receiving optical line 5 to the optical receiver 6.

On the other hand, the optical pulse passing through the optical path 15a is transmitted to the optical sensor 13.
When reaching point a, a part of the optical pulse hits the optical sensor and is reflected as before, and is transmitted to the optical path 15a as an optical pulse of reflected light, and the rest is an optical pulse of transmitted light that passes through the optical sensor. and is transmitted to the optical path 14a. The optical pulse of the transmitted light passing through the optical path 14a passes through the directional coupler 12a t time earlier than the optical pulse of the reflected light passing through the optical path 15a, and the branched optical path 11a and the directional coupler 10a
, light frame line 3. Passing through the directional coupler 4, the receiving optical line 5
from there to the optical receiver 6.

FIG. 2 is a characteristic diagram of each optical pulse received by the optical receiver 6, with time on the horizontal axis and pulse height on the vertical axis. A shows an optical pulse branched into two by the directional coupler 12a and transmitted to the optical path 14a, and B shows an optical pulse split into two by the directional coupler 12a and transmitted to the optical path 15.
This is an optical pulse that is split into two at point a and passes through the optical path 14a. a is the optical pulse passing through the optical path 14a, b is the optical pulse passing through the optical path 1
A light pulse passing through 5a. The optical pulse received by the optical receiver 6 is amplified by an amplifier 7, processed by a signal processing device 8, and output to a display device 9.

A light pulse of A-b and a light pulse of B-a, that is, a light pulse of transmitted light that is split into two by the directional coupler 12a and sent to the optical path 14a, and among the light pulses, passes through the optical sensor 13a; Among the optical pulses sent to the optical path 15a, the optical pulses of the transmitted light that pass through the optical sensor 13a are superimposed, and as shown in FIG. Each light pulse of light is displayed. When this optical sensor is attached to a device under test and the magnetic field of the device under test is to be measured, if a magnetic field is generated in the device under test, the optical sensor 13a detects the magnetic field and emits light as shown in Fig. 3. A light pulse of the light transmitted through the sensor is output, and is no longer output when the magnetic field is removed. Furthermore, when the magnetic field changes, the height of the pulse in the center of FIG. 3 rises and falls, indicating that there is a change in the magnitude of the magnetic field.

FIG. 4 is a power waveform diagram of the optical information received by the optical receiver 6, and it can be seen that the peak value is logarithmically attenuated, shifted by a time corresponding to the distance between each terminal.

〔Effect of the invention〕

As explained above, in the present invention, two optical fibers of different lengths are connected on both sides of an optical sensor, and the other end is connected to a directional coupler to respond to optical pulses transmitted from the input side. The signal is sent back to the receiving side. In an optical sensor, the transmission conditions of light passing through the optical sensor change due to physical change or electromagnetic influence, and the central peak value of the superimposed optical pulse changes due to the delay effect of light. As a result, changes in the physical conditions of a plurality of terminals can be detected using - optical frame lines.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing the configuration of the present invention, Fig. 2 is an optical pulse waveform diagram showing the delay state of optical pulses, Fig. 3 is a waveform diagram of superimposed transmitted light, and Fig. 4 is a received waveform diagram. FIG. 3 is an optical power diagram of an optical signal. 1: Electric pulse generator 2: Optical transmitter 3: Optical frame line 4: Directional coupler 5: Receiving optical line 6: Optical receiver 7: Amplifier 8: Signal processing device 9: Display device

Claims (1)

[Claims] 1.Equipped with an optical trunk line consisting of a single optical fiber that transmits optical pulses output from an optical transmitter, and at least one optical branch line branched from the optical trunk line, and with a direction to the optical branch line. At the same time, optical fibers of different lengths are connected to the input and output sides of the directional coupler, and the other ends of both optical fibers are stimulated by external physical and electromagnetic stimulation. An optical fiber sensor device characterized by optically connecting both ends of an optical sensor whose transmission amount changes.