JPH0248959B2 - KOGAKUDENSOSHISUTEMU - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical transmission system that transmits temperature, displacement, and other physical quantities using optical signals.

An object of the present invention is to realize an optical transmission system that consumes very little power on the transmission end side and that operates stably as a whole. Another object of the present invention is to realize a system of this type that is not affected by changes in characteristics of optical transmission lines or optical elements.

The device according to the present invention is characterized in that when the measured physical quantity fluctuates by more than a predetermined amount or when the amount of change is large, the measured physical quantity is converted into an optical signal and transmitted to the receiving end side. .

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1 is a transmission end, 2 is a reception end, 3 is a transmission path connecting transmission end 1 and reception end 2,
Here, it is composed of two optical fibers 31 and 32.

At the transmission end 1, a sensor 11 is given a measured physical quantity and converts it into an electrical signal, from which an analog electrical signal e _i corresponding to, for example, the measured temperature is obtained. 12 is this analog signal e _i
13 is a comparator that compares the output signal with the delay circuit 12 and the signal from the sensor 11. 14 is a circuit that drives a switch SW according to the output of the comparator 13. This is a switch drive circuit.

BT is a photoelectric conversion means that receives light supplied from the optical fiber 31 and converts the light energy into electrical energy, and uses, for example, a photovoltaic cell, a solar cell, or the like. C ₁ , C ₂ and R ₁ are capacitors and resistors,
RE is a regulator that smoothes the electrical energy from the photoelectric conversion means BT and makes it a constant voltage.
A power supply circuit 10 that stores this is configured.

15 is a pulse width conversion circuit that inputs the signal from the sensor 11 and converts it into a pulse width signal; 16;
17 is a transistor for driving an optical element 18 which inputs the pulse width signal from the pulse width conversion circuit 15 and outputs a narrow pulse signal at rising and falling edges. The optical element 18 is, for example, a light emitting diode or a laser diode, and is driven by a narrow pulse signal from the drive circuit 16 via a transistor 17 to output a narrow optical pulse. This optical signal is transmitted to the receiving end via the optical fiber 32.

The sensor 11 and the comparison circuit 13 are both operated by being supplied with power from the power supply circuit 10, and the pulse width conversion circuit 15, the optical element drive circuit 16, and the light emitting element 18 operate when the switch SW is driven. It operates by being supplied with power from the power supply circuit 10 via the switch SW.

At the receiving end 2, 21 is a light source, for example
An LED or LD is used, and light from this is transmitted to the receiving end 1 side via an optical fiber 31. 22 is a drive circuit for the light source 21. Reference numeral 23 denotes a light receiving element, which is optically coupled to one end of the optical fiber 32 and receives the optical signal transmitted via the optical fiber 32. 24 is an amplifier that amplifies the signal from the light receiving element 23, 25 is a signal processing circuit that processes the signal from the amplifier 24, and 26 is an indicator.

The operation of the apparatus configured as described above will be explained below with reference to the waveform diagram of FIG. 2. At the receiving end 2, a drive circuit 22 drives a light source 21. For example, continuous light is emitted from the light source 21, and the light energy is supplied to the transmission end 1 side via the optical fiber 31.

At the transmission end 1, the photoelectric conversion means BT receives optical energy emitted from one end of the optical fiber 31 and converts it into electrical energy. This electrical energy is stored in the capacitors C ₁ and C ₂ and is supplied to the sensor 11 and comparator 13 as respective power supplies.

The sensor 11 converts a measured physical quantity into an electrical signal, and sends the output signal e _i to a delay circuit 12 and a comparator 13.
and is applied to the pulse width conversion circuit 15. The delay circuit 12 delays the input signal e _i by a predetermined time τ, and the comparator 13 delays the input signal e i by a predetermined time τ.
Compare e _i with the signal e _i1 from the delay circuit 12 which changes with a delay of τ. With this, sensor 1
The amount of change in the output signal of No. 1 is detected.

Now, as shown by the solid line in Fig. 2A, the sensor 11
If the signal e _i from the delay circuit 12 changes, the signal e _i1 from the delay circuit 12 changes as shown by the broken line.

The comparator 13 compares the applied signals e _i and e _i1 , and if the difference Δe between the two signals changes by a predetermined value or more, the comparator 13 drives the switch via the switch drive circuit 14.
SW is driven, and even after Δe becomes zero, it continues to be driven for a fixed time T as shown in FIG. 2B. When the switch SW is driven, the pulse width conversion circuit 15, the optical element drive circuit 16, and the optical element 1
8 is first supplied with power from the power supply circuit 10 side via the switch SW, and enters the operating state.

When the pulse width conversion circuit 15 is activated, it converts the output signal e _i from the sensor 11 into a pulse width signal corresponding to e _i as shown in FIG. A narrow pulse signal as shown in FIG. 2D is output at the rising and falling edges. The light emitting element 18 is driven by this narrow pulse signal via the transistor 17 to emit light, and the optical pulse signal from this element is transmitted to the receiving end 2 side via the optical fiber 32. Here, when using an LED as the light emitting element 18,
To get a sufficient light signal from this LED, approximately
A drive current of 50 mA is required, but here the signal related to the measured physical quantity is transmitted as a narrow optical pulse signal for a certain period of time only when the measured physical quantity changes. It is possible to lower the average current and minimize power consumption at the transmission end.

At the receiving end 2, the light receiving element 23 receives the optical pulse signal transmitted via the optical fiber 32,
The signal is sent to the signal processing circuit 25 via the amplifier 24. The signal processing circuit 25 measures the pulse intervals t ₁ and t ₂ and processes them to obtain an electrical signal related to the measured physical quantity, which is displayed on the indicator 26 .

According to the device configured in this way, on the transmission end side, the circuit means (driving circuit 16, optical element 18, etc.) for transmitting the optical signal starts from the time when the amount of change in the measured physical quantity changes from a predetermined value. Since it operates for a certain period of time and transmits a narrow pulse signal from the transmission end, the power consumed at the transmission end can be minimized overall.
It is possible to realize an optical transmission system that operates stably with the power from the photoelectric conversion means BT that receives the supplied light.

FIGS. 3 and 4 are block diagrams showing other embodiments of the present invention, in which only the transmission end side is shown.

In the embodiment shown in FIG. 3, the output signal e _i from the sensor 11 is compared with a predetermined value E _S in the comparator 13, and e _i
When becomes larger or smaller than this predetermined value, the switch SW is driven via the switch drive circuit 14, and the measurement signal is transmitted as an optical signal to the light receiving end side. In addition, here, a clock circuit CLK operated by power from the power supply circuit 10 is provided on the transmission end side, and the output signal from the clock circuit CLK determines whether e _i is large or small.
The switch SW is driven at regular intervals via the switch drive circuit 14, and the output signal e _i from the sensor 11 is transmitted as an optical signal.

Note that in this system, the photoelectric conversion means
The power supply circuit including BT may use a battery. In this case, one optical fiber 31 can be omitted.

In the embodiment shown in FIG. 4, an optical element whose light transmittance changes depending on the output of the drive circuit 16 (for example, a combination element of PLZT and a polarizing plate) is used as the optical element 18, and the light supplied from the optical fiber 31 is used as the optical element 18. A portion of the optical fiber 32 is applied to one end of the optical fiber 32 via the optical element 18. In addition, the optical fiber 31
A trigger pulse Tp that commands signal transmission is included in the optical signal supplied from the switch, and this trigger pulse Tp is applied to the switch drive circuit via the capacitor _C2 to drive the switch SW. It is.

According to this system, even if the measured physical quantity does not change, by sending a trigger pulse from the receiving end, an optical signal related to the measured physical quantity can be transmitted from the transmission end whenever desired.

In each of the above embodiments, the transmission end and the reception end are connected by an optical fiber, but this may be omitted and the optical signal may be propagated through space. Furthermore, an optical pulse signal having a frequency related to the measured physical quantity may be transmitted from the transmission end side.

As described above, according to the present invention, it is possible to realize an optical transmission system in which the power consumed on the transmission end side is minute and the entire system operates stably. Furthermore, since the signal related to the measured physical quantity is transmitted as a narrow optical pulse signal, an optical transmission system that is not affected by changes in the characteristics of the optical transmission line or optical element can be realized.

[Brief explanation of drawings]

Fig. 1 is a configuration block diagram showing one embodiment of the present invention, Fig. 2 is an operational waveform diagram of the system shown in Fig. 1, and Fig. 3 is a block diagram showing an embodiment of the present invention.
4 and 4 are block diagrams showing other embodiments of the present invention. 1...Transmission end, 2...Reception end, 3...Optical transmission line, BT
... photoelectric conversion means, 10 ... power supply means, 11 ... sensor, 15 ... drive circuit, 18 ... optical element, 21 ... light source, 23 ... light receiving element.

Claims (1)

[Scope of Claims] 1. A system for transmitting an optical signal related to a measured physical quantity from a transmission end side to a receiving end side, the transmission end side comprising: a sensor unit that detects a measured physical quantity and converts it into an electrical signal; an optical element that outputs an optical signal, a drive circuit that drives the optical element in relation to a signal from the sensor section, a power supply means, and an optical element that outputs an optical signal; an optical transmission system comprising: circuit means for supplying power from the power supply means to the drive circuit when the power exceeds a certain value. 2. The power supply means is configured to include a photoelectric conversion means, and converts an optical signal supplied from a receiving end into electrical energy to supply electric power, as set forth in claim 1. optical transmission system. 3. A clock circuit that operates by being supplied with power from the power supply means is provided on the transmission end side, and the power from the power supply means is applied to the drive circuit in response to a signal from the clock circuit. optical transmission system. 4. The optical transmission system according to claim 1, wherein power from the power supply means is supplied to the drive circuit by a trigger pulse signal supplied from the receiving end side.