JPS6139642A - Light transmitting device - Google Patents

Abstract

PURPOSE:To make a power line unnecessary by connecting a light transmitting device including a signal generating section, a light transmitter/etc. and a central controlling section only by fibers and using a solar battery as a power source of the light transmitting device. CONSTITUTION:The light transmittter 3 of the light transmitting device amplifies digital signals, modulates a light emission element in terms of strength and sends to the central controlling section 10 through optical fibers 9. On the other hand, a switch for supplying power intermittently from a solar battery 4 and a battery 5 to a signal generating section 1, an interface 2 and the light emitter 3 and a clock that determines timing of opening and closing the switch are incorporated in the power source controlling section 6 of the light transmitting device. The period T0 of transmission is determined by the clock, and power is supplied for a time TS to send signals, and power supply is not made during T0-TS. and transmission is stopped. Though the clock is driven at all times, power consumption is very small.

Description

DETAILED DESCRIPTION OF THE INVENTION C7) Technical Field The present invention relates to an optical transmitter used for signal transmission in a vast plant or the like.

In a plant, there are various facilities spread out over a vast outside area, and signals regarding various state quantities are emitted from these facilities. These can be called signal sources in the sense of signal generation sources.

There are control signals such as opening and closing of switches, and there are also measurement value signals related to physical quantities such as temperature, pressure, and flow rate of liquids and gases. There are also signals that indicate whether a certain liquid, gas, etc. is present or absent.

Opening and closing of switches are digital signals. The measured value signal from the sensor may be a digital signal, but is often analog information. A/D even if it is an analog quantity
It can be converted and sent.

As described above, there are many signal sources in a plant that emit a wide variety of signals. The operation of each plant equipment must be controlled by a central control unit. Therefore, it is necessary to collect the signals from each signal source to a central control unit.

Conventionally, electric wires connected the signal source and the central control unit over several hundred meters to several thousand meters.

(b) Conventional technology Two types of electric wires are used: a power line and a signal line.

Although the power line is sufficient for low power, it provides power from the central control unit to each signal source. Sometimes it's alternating current, but sometimes it's direct current. Since the distance is short, low voltage direct current may be sent.

The signal line is used to send signals, and may be a twisted pair wire, a shielded wire, or the like. The signal line sends the signal from the signal source to the central control unit.

However, those that use electric wires have the disadvantage that the signal line is susceptible to noise (such as lightning surges).

Weak against electromagnetic noise.

Power lines can cause fires due to short circuits and other accidents. Especially in oil plants, etc., explosion-proof measures are necessary.

Also, a thick cable is required as a whole.

The cost of the cable itself is high, and the cost of laying the cable is also high.

On the other hand, there are devices in which only the signal line is replaced with an optical fiber. A signal is sent in the form of an optical signal through an optical fiber. In this way, it will not be affected by electromagnetic noise at all, and the signal line itself will be lightweight. However, power lines are still needed. In the signal source, the power line serves as a power source for a sensor, etc., and supplies power as necessary for an amplifier circuit, an A/D conversion circuit, and an F:10 conversion circuit.

Since the power line is a relatively thick copper wire, the cost is still high. The fact remains that explosion-proof measures are necessary.

(1) The equipment and devices that serve as component signal sources require a power source to drive the sensors and transmitters. For this reason, conventionally, even if signal lines are replaced by optical communication, power lines are not replaced by other means. This point must be resolved.

Sensors measure various physical and chemical quantities, but this requires only a small amount of power, including the sensor drive circuit.

An optical transmitter consists of a signal amplification circuit, a binarization circuit, and an A/
A D conversion circuit may be necessary. However, these power consumptions are still very small. Driving the light emitting element requires the greatest amount of power.

As the light emitting element, a light emitting diode LED or a laser diode LD is used. These semiconductor elements can be driven with a low voltage, but with a large current. Several hundred mA flows. Therefore, the power consumption is several hundred mW.

Conventionally, power lines were required to drive the light emitting elements.

However, the sensor signal changes less frequently. Temperature, pressure, flow rate, storage volume, gas partial pressure, and other physical and chemical variables do not change suddenly. If this is the case, when the minimum time at which a change occurs is Tm, sampling may be performed at a somewhat shorter cycle To, and the sensor signal may be transmitted to the central control unit every TO. It is not necessary to constantly send sensor signals to the central control unit. If the time required to send a sensor signal is Ts, then Ts/T o
can be made much smaller than 1. The transmission period To is assumed to be several seconds, for example. When a change occurs, the maximum time delay before this is sent to the central control is TO. In many cases, a delay of a few seconds does not cause any difference.

Ts is the time required to send one signal. The TsO value varies depending on the complexity of the signal.

However, it is easy to reduce Ts/To from 1/several tenths to 1/several hundreds of valves.

TS/″r compared to the case where the light emitting element is continuously driven.

If the light emitting element is driven by Ts, the power consumption is Ts
/To.

The various facilities, equipment, and devices that make up a plant are often installed outdoors. Since it is outdoors, solar cells can be installed.

Solar cells using amorphous silicon semiconductors are being manufactured and used at low cost. Unlike crystalline silicon, large-area solar cells can be manufactured in a short time at low temperatures on a substrate of any material by plasma CVD or the like.

The conversion efficiency of solar cells is still low, and both voltage and current are small, but if the area is large, the current can be increased.

As mentioned earlier, among the signal source circuits, the one that requires the most power is the light emitting element. If we decide to drive the light emitting element intermittently (Ts/To),
Effectively, a power of several tens of mW to several mW is sufficient.

Therefore, in the present invention, a solar cell is used as a power source, thereby eliminating the need for power lines that have been considered indispensable in the past. Therefore, only the signal line connects the signal source and the central control unit. Since it is an optical fiber, it is cheap, lightweight, and unaffected by noise.

FIG. 1 is a configuration diagram of an optical transmitter according to the present invention.

The signal generating section 1 is a section that generates various digital and analog signals. This may be a digital control signal, such as opening or closing a switch. It may also be a measurement value signal obtained by measuring a physical quantity as an analog quantity using a sensor. In addition to the sensor, it also includes a circuit that amplifies the current and voltage of the sensor. Electric power is required for these parts to function.

The ink face 2 converts the signal generated by the signal generator 1 into
Convert to digital signal with appropriate voltage and repetition period. If the original signal is an analog quantity, it is A/D converted.

If the digital signal is one bit, there is not much problem, but if it is several bits, a parallel/serial conversion circuit is also required.

An optical transmitter amplifies a digital signal and modulates the intensity of a light emitting element using the digital signal. The optical transmitter 3 is the part that consumes the most power.

The signal generator 1, interface 2, and optical transmitter 3 are connected by a signal line 7 (electric wire). Since it is a signal line within one piece of equipment, a short wire is sufficient.

The above configuration is similar to that of a conventional transmitting device. In the present invention, the solar cell 4 supplies the power necessary to drive these devices.

The battery 5 works complementarily with the solar cell 4 to power the device.

The battery 5 is a rechargeable and dischargeable battery. at night or in the rain,
When the weather is cloudy, the power of the solar cell 4 is insufficient, so the battery 5 mainly supplies power.

The power supply control unit 6 controls the power of the solar cell 4 and the battery 5.
The signal is intermittently supplied to the signal generator 1, interface 2, and optical transmitter 3.

This point is the most distinctive part of the present invention.

The power supply control unit 6 intermittently receives signals from the solar cell 4 and the battery 5, the signal generation unit 1, the ink face 2, and the optical transmitter 3.
It has a built-in switch that supplies power to the device, and a clock that determines when to open and close the switch. The clock defines the transmission period TO, during which Ts
The signal is transmitted by supplying power for the period (To-Ts), and transmission is stopped without supplying power during (To-Ts). The clock is always running.

If CMOS is used as the clock, the power consumption may be approximately several tens of microwatts at most.

Therefore, even if the clock is constantly driven, the power consumption due to this is extremely small, and it is the same as that almost no power is consumed.

Of the transmission period TO, Ts is transmitter 3, ink face 2
, power is supplied to the signal generator 1 from a solar cell 4 and a battery 5. The power at this time is several hundred mW. Mainly, the battery 5 provides power.

During the remaining period (To-Ts) of the transmission period TO, the switch of the power supply control section 6 is open, and power is not supplied to the signal generation section 1, ink face 2, and optical transmitter 3. Therefore, no current flows through the light emitting element and no light is emitted. The power consumption at this time is only several tens of microwatts of clock power. Electric power generated by the solar cell 4 is stored in a battery 5. T
Since s/To is a sufficiently small value, the electromotive force of the solar cell 4 does not need to be very large.

Let me give an example. If you communicate once per second, it will slow down.

To = 1 see. Transmission data is often very small, such as one on/off point, and the data format is only about 10 bits. IMBit this
/sec, the time required for transmission is 1
It is only 0 μsec. In other words, Ts = 10μsec
It is. The operating ratio Ts/To is 10. Even if the light emitting element power is required to be 1000 mW, the average power that can be generated by the solar cell only needs to be 10 IIW or more.

The optical pulse signal converted into E10 by the light emitting element is transmitted through the optical fiber 9 and collected in the central control unit 10.

A power line 8 connects the power supply control section 6, the signal generation section 1, the interface 2, and the optical transmitter 3, but this can be made sufficiently short and the whole can be housed in a sealed container. Therefore, it is possible to meet the requirements for explosion protection.

(2) Effects (1) Since power lines are not required, cable costs are reduced. It is necessary to use multicore cables that include electrical wires and optical fibers. An optical fiber core cable is fine.

(2) Installation work is easy and low cost. This is because the cable is thin and light.

(3) The transmission line is explosion-proof. This is because it does not use electric wires.

(4) It can be constructed with a small solar cell and a small battery. This is because communication is done intermittently.

(5) Signal transmission that is resistant to noise becomes possible. This is because only optical fibers are used.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an optical transmitter according to the present invention. 1...Signal generator 2...Interface 3...Optical transmitter 4...Solar cell 5... ···· Battery
-6......Power control unit 7...Signal line 8...Power line 9...Optical fiber 10 ...Central control unit inventor: Tetsuo Sugimoto Patent applicant: Sumitomo Electric Industries, Ltd.■

Claims (1)

[Claims] A signal generator 1, an interface 2 that converts the signal generated by the signal generator 1 into a transmittable digital signal, an optical transmitter 3 that includes a light emitting element and converts an electrical signal from the interface 2 into an optical signal, and a solar It has a built-in battery 4, a rechargeable battery 5 connected to the solar battery 4, and a clock that is constantly driven, and generates a signal for the power of the solar battery 4 and battery 5 only during the short transmission time Ts of the transmission cycle To. Part 1
, an interface 2, and an optical transmitter 3 to intermittently transmit optical signals.