EP0053790A1 - Sensorsystem für Lichtleitfasern, vorzugsweise zum Messen physikalischer Parameter - Google Patents

Sensorsystem für Lichtleitfasern, vorzugsweise zum Messen physikalischer Parameter Download PDF

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Publication number
EP0053790A1
EP0053790A1 EP81110054A EP81110054A EP0053790A1 EP 0053790 A1 EP0053790 A1 EP 0053790A1 EP 81110054 A EP81110054 A EP 81110054A EP 81110054 A EP81110054 A EP 81110054A EP 0053790 A1 EP0053790 A1 EP 0053790A1
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EP
European Patent Office
Prior art keywords
fiber optical
sensor system
optical sensor
light
light source
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP81110054A
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English (en)
French (fr)
Inventor
Georg H. Dr. Sichling
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Siemens AG
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Siemens AG
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B14/00—Transmission systems not characterised by the medium used for transmission
    • H04B14/02—Transmission systems not characterised by the medium used for transmission characterised by the use of pulse modulation
    • H04B14/026—Transmission systems not characterised by the medium used for transmission characterised by the use of pulse modulation using pulse time characteristics modulation, e.g. width, position, interval
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/80—Optical aspects relating to the use of optical transmission for specific applications, not provided for in groups H04B10/03 - H04B10/70, e.g. optical power feeding or optical transmission through water
    • H04B10/806—Arrangements for feeding power
    • H04B10/807—Optical power feeding, i.e. transmitting power using an optical signal
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R16/00—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for
    • B60R16/02—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements
    • B60R16/03—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements for supply of electrical power to vehicle subsystems or for
    • B60R16/0315—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements for supply of electrical power to vehicle subsystems or for using multiplexing techniques

Definitions

  • This invention in general relates to a fiber optical system for transmission of information from one location to another.
  • this invention relates to a system for measuring one or more physical parameters or data and transmission thereof to evaluation circuitry, which circuitry is located remote from the location of the measurement.
  • this invention relates to an optical sensor system using at least one transducer for measuring a physical parameter, preferably a multitude of transducers for measuring various physical parameters, . and fiber optical means for optical transmission of the . sensed parameters to an evaluation circuitry.
  • Such optical sensor system may be applied, for instance, in industrial facilities such as power plants or chemical plants, or in automobiles for the measurement and/or control of various functions.
  • fiber optical sensors and transducers for measurement of physical parameters are disclosed. These transducers generate digital signals in accordance with the physical parameter being measured without using analog to digital (A/D) converters.
  • the transducers reguire only light in order to become energized.
  • the aforementioned sensors may be applied for measuring temperature, pressure, flow rate, and similar physical parameters. They are included in fiber optical transmission systems.
  • the transmission schemes can be digital intensity modulation (binary, pulse width, frequency, etc.), wave length or color modulation, and color multiplexing.
  • the transducer In the measurement of physical parameters, it is generally desirable that the transducer directly produce digital signals, rather than require an electric A/D converter. Further, the transducer should require power only in the form of optical power. In addition, the design of the transducer and the optical transmission line should be such that the system can withstand hostile environments, including electromagnetic interference.
  • a fiber optical sensor system which works as a luminescent temperature transducer.
  • the system includes a pulsed light source which emits light pulses into the first end of a fiber optical cable.
  • the remote sensor is simply the expanded second end of the fiber optical cable, which end is coated with or is embedded in a phosphorescent material. Phosphorescence of this material occurs after each light pulse which has been received from the light source.
  • a response or return light signal is .emitted from the phosphorescent material in backward direction through the fiber optical cable.
  • the response signal is coupled to a photodetector.
  • the electric output signal of the photodetector that is the post-excitation return signal
  • a sample-hold or time-constant measurement device Here, the decay time constant of the phosphorescent process is measured.
  • the temperature sensor system provides a pulse width which is proportional to the decay time constant, and therefore, proportional to the temperature to which the phosphores- .cent material is exposed. --This fiber optical sensor system is based on the measurement of a decreasing analog signal and therefore subject to disturbing influences. In addition, the costs for such a system may be high.
  • a fiber optical sensor system which is not only precise and reliable, but which is also inexpensive to manufacture.
  • Such a system should have some sort of energy source on the measurement side so that active electric devices, such as transistors, may be energized.
  • the system should derive the required power from optical signals transmitted through a fiber optical transmission line, and it should not require any additional sources of electric power at the location(s) of measurement.
  • a fiber optical sensor system of the kind just described appears to be particularly suited for use in automobiles. In conventional automotive applications, more than a dozen parameters are sensed at the automobile engine alone, and more than a dozen other parameters are measured at other locations of the automobile.
  • a sensor system applied in a car should require only a minimum of cabling, should be extremely reliable, even under extreme environmental conditions like heat, cold, humidity, vibration, chemical and mechanical stress, and also under the usual wear and tear to which an automobile is subjected.
  • a fiber optical transmission cable by nature would be little effected by all these factors and would exhibit the additional advantage that it is not subject to electromagnetic interference, which may be generated by the ignition system of the car and by other devices.
  • an electro-optical sensor system may be used widely, if such a system could be manufactured inexpensively and if the accuracy required for the sensors can be obtained. This is not only true for automobile applications, but also for other applications with similar requirements, such as industrial applications.
  • an independent power source such as a battery, a power line or an electric outlet
  • external disturbances such as electromagnetic interference (emi)
  • a fiber optical sensor system for transmission of information from one location to another contains a fiber optical transmission line or cable.
  • This transmission line has a first end and a second end for transmitting light therebetween.
  • the system also contains a first light source for emitting a first light beam into the first end of the transmission line.
  • At the second end of the transmission.3.ine is arranged at least one first.receiver element which is sensitive to the light of the first light source.
  • This first receiver element is provided for receiving light of the first light source . from the second end of the transmission line and for oen- erating a first electric output signal in accordance with the light received.
  • An electrical energy storage device is connected to the first receiver element. It will receive the first electric output signal.
  • This device will store energy in accordance with the optical energy transmitted through the transmission line.
  • a second light source At the second end . of the transmission line is also arranged a second light source.
  • This second light source is provided for emitting a second light beam into the second end of the transmission line.
  • the second light source is energized from the electrical energy storage device, and it is controlled according to the information to be transmitted.
  • a second receiver element sensitive to the light of the second light source.
  • the second receiver element will receive light of the .second light source from the transmission line.
  • This second receiver element is provided for generating a second electric output signal in accordance with the light received. This signal is in accordance with the transmitted information.
  • the energy storage device preferably may comprise a storage capacitor which is connected to the first receiver element.
  • the capacitor will derive an electrical charge from the receiver element when the first light source emits the first light beam.
  • the capacitor is the energy source used for energizing the second light sburce.
  • the system is applicable for transmission of various physical parameters. These parameters may be sensed by any kind of sensor, such as an electromechanical or photoelectric sensor.
  • the fiber optical sensor system may be designed such that besides the second light source, further electronic components are connected to be energized from the energy storage device.
  • a preferred embodiment of the fiber optical sensor system for measuring at least one physical parameter may comprise:
  • information is intended to be applied in its most general form and comprises all sort of information, such as data, signals, physical parameters, measurement results, communication signals and code words.
  • Fig. 1 a fiber optical sensor system for transmission of physical parameters pl, p2, p3,p4... from a location of measurement or measuring side 2 to a remote location of application or control and evaluation side 4 is illustrated.
  • the sensor system is preferably applicable in the control and/or testing of automobiles. This design does not depend on the amplitude of an optical beam and does not exhibit any specific problems of accuracy.
  • the system includes a fiber optical transmission line or transmission cable 6 for transmission of light in either direction.
  • the transmission line 6 is operatively connected to an emitter and receiver device 8.
  • the device 8 includes a first light source 10 for emitting a first light beam through a beam splitter 12 into the left end of the fiber optical transmission line 6.
  • the light source 10 may be a light emitting diode (LED), a laser or a GaAs light emitter.
  • the transmission line 6 leads to the measuring side 2.
  • the fiber optical transmission line 6 passes various coupling elements 14, 16, 18 and 20, four of which are illustrated. There may be provided more than four coupling elements 14, 15, 18 and 20.
  • the coupling element 14-20 may be, for instance, T-couplers or branching elements, such as disclosed in "Applied Optics", Vol. 16, No. 8, August 1977, pages 2195-2197.
  • the four coupling elements 14-20 serve to distribute the first light beam among four fiber optical branches 24, 26, 28'and 30, respectively.
  • the parameters pl-p4 may be, for instance, pressure, temperature, gas flow and speed.
  • the measuring elements 3 4 -40 each contain a-first receiver element which is sensitive to the light of the first light source 10.
  • the first receiver elements generate first electric output signals in accordance with the light which they receive.
  • the measuring elements 34-40 each also contain an electrical energy storage device which is supplied by the first electric output signal and which will store the energy contained in such signal.
  • Each of the measuring elements 34-40 further contains a second.light source for emitting a second light beam back into the branches 24-30, respectively. From here, the second light bean passes through the respective coupling elements 14-20 into the left end of the fiber optical transmission line 6 on the control and evaluation .side 4. From this end, the second light beam is transmitted into the device 8.
  • Each of the second light sources within the individual measuring elements 34-40 is energized from the associated electrical energy storage device.
  • the evaluation circuitry 42 contains a second receiver element which is sensitive to the light of all second light sources. It generates a second electrical output signal in accordance with the light received and thereby in accordance with the physical parameter pl, p2, p3 or p4 transmitted.
  • Fig. 1 the light paths from the emitter and receiver device 8 to the individual measuring elements 34-40 are indicated by straight arrows, whereas the light paths from the measuring elements 34-40 back to the device B are indicated by broken arrows.
  • an address line 49 which leads from the light control circuitry for the light source 10 to the evaluation circuitry 42.
  • this address line 44 information is transmitted indicating the measuring element 34, 36, 38 or 40 which is being addressed by the control circuitry: Therefore, in the circuitry 42 the received signal can.be assigned to the measuring element 34-40 which has responded.
  • the coupling element 14 is here designed as a well-known branching element.
  • a small fiber line 24a branches off the main fiber optical transmission line 6.
  • the coupling elements 16-20 may be designed in a similar way.
  • FIG. 3 an embodiment of one of the measuring elements 34-40 is illustrated. This embodiment may be, for instance, the measuring element 34.
  • first receiver element 46 the end of the fiber optical branch 24 which emits the first light beam 45 is arranged close to a first receiver element 46.
  • This first receiver element 46 may be a small photo diode or an arrangement of various photo diodes.
  • the element 46 receives the first light beam 45 from the branch 24 and generates an output volt- ace in accordance with the light received.
  • optical means for concentrating the radiation on the light sensitive area of the element 46.
  • the first receiver element 46 is connected in series with a diode 48 for generating a supply voltage between a supply voltage bus 50 and ground 52.
  • the connection point between the element 46 and the diode 48 is designated as 54.
  • the series connection 46, 48 is coupled to an energy storage device 56.
  • the storage device 56 is designed as a storage capacitor.
  • a Zener diode 58 is connected parallel to the storage capacitor 56. This Zener diode 58 serves to keep the voltage of the storage capacitor 56 constant.
  • the storage capacitor 56 derives electrical charges from the first receiving element 46 when the first light source 10 emits the first light beam 45. It stores these charges and energizes various electronic components in the measuring element.34, as will be discussed below.
  • the measuring element 34 further contains a transducer unit 60 for transforming the physical parameter pl to be measured into a corresponding electrical quantity and subsequently into an optical signal
  • the transducer unit 60 contains an RC combination formed by a resistor 62 and a capacitor 64 which are connected in series.
  • the components forming the RC combination 62, 64 are selected such that the time constant of the RC combination 62, 64 is dependent on the physical parameter pl to be measured.
  • the resistor 62 is exposed to the parameter pl, and the resistance of the resistor 62 is directly dependent on the parameter pl, whereas the capacitance of the capacitor 64 remains constant.
  • the resistance may vary, for instance, in accordance with temperature or pressure.
  • the resistor 62 may be considered as the sensor proper of the measuring element 34 of the fiber optical sensor system.
  • the transducer unit 60 contains a voltage divider formed by the series connection of a first resistor 66 and a second resistor 68. This voltage divider 66, 68 is connected between the supply voltage bus 50 and ground 52.
  • the first resistor 66 represents a first voltage source of a fairly constant first supply voltage
  • the second resistor may be considered as a second voltage source of a second supply voltage that is also fairly constant.
  • the series connection consisting of the sensor resistor 62 and the capacitor 64 is coupled through a first switching element 70 to a supply voltage source.
  • This supply voltage source is the first voltage source represented by the first resistor 66.
  • the first switching element 70 preferably is an electronic switch, such as a FET. It is controlled by an initiation signal which is derived from a control device, specifically from an address decoder 72.
  • the address decoder 72 which is energized from the supply voltage bus 50, decodes an input signal arriving on its input line 73.
  • the input line- 73 is connected to the connection point 54.
  • an output pulse is issued as an initiating signal i.
  • the instant when this pulse appears at the output of the address decoder 72 will be termed the first point of time.
  • the control line between the address decoder 72 and the first switching element 70 is shown in Fig. 3 as a broken line.
  • the first switching, element. 70 in combination with the first voltage source (resistor 66) may be considered as a device for changing the charge of the capacitor 64 in accordance with the time constant of the RC combination 62, 64.
  • the first voltage source (resistor 66) is determined to charge the capacitor 64 through the resistor 62. Therefore, the initiation signal i issued to close the first switching element 70, may be considered as a "start charge” signal.
  • the capacitor 64 will be charged to obtain a voltage U c of the polarity indicated in Fig. 3.
  • the transducer unit 60 also includes a device for discharging the capacitor 64 after it has been charged.
  • This device basically includes the second voltage source as represented by the second resistor 68, a second switching element 74, and a delay circuit 76.
  • the second switching element 74 which may be a transistor such as a FET, is connected parallel to the series connection of the capacitor 64 and the second resistor 68. It is actuated by the delay circuit 76, which in turn is supplied with the initiation signal i from the address decoder 72.
  • the delay circuit 76 has a delay time To which is fixed.
  • the delay circuit 76 may be designed, for instance, as a counter which issues an output pulse after the initiation signal has been received.
  • the output pulse is delayed by the delay time To with respect to the initiation signal i.
  • the second voltage source (resistor 68) has a reverse polarity with respect to the charged capacitor 64. As soon as the second switching element 74 is closed (ON position), the voltage of the second voltage source (resistor 68) counteracts the capacitor voltage U c , so that the capacitor 64 is discharged.
  • the transducer unit 60 also contains a device 78 for sensing the voltage of the capacitor 64 and for determining a second point of time, which is precisely the instant when the capacitor voltage U c has reached a predetermined value.
  • this predetermined value may be zero volts.
  • the voltage sensing device 7B may be formed by a comparator such as a flip-flop.
  • the voltage sensing device 78 is a control unit. It is part of an electro-optical device for emitting a second light beam which is directed into the face end of the fiber optical branch 24: In particular, the device 78 generates a return or response light pulse 80. Part of the electro-optical emitting device is also a second light source 82.
  • This light source 82 may be a light emitting diode (LED) or a laser, preferably a GaAs light emitter. It should be mentioned that-the wavelength characteristics of the second light source 82 may be different from the wavelength characteristics of the first light source 10 (shown in Figs. 1 and 5).
  • the second light source 82 is connected in series with a third switching element 84 between the supply voltage bus 50 and ground 52.
  • the third switching element 84 may be a transistor such as a FET. It is actuated by the output of the voltage sensing device 78, as indicated by a broken control line. When the third. switching element 84 is brought into its closed position (ON position), the energy storage capacitor 56 will supply the second light source 82 with electric energy for emission of the return pulse 80.
  • the second light source 82 will emit the return pulse 80 when the voltage of the capacitor 64 has reached the predetermined voltage value at the second point of time. Since the time difference between the second and the first point of time is an indication of the value of the parameter pl, the occurence of the return pulse 80 with respect to the first point of time will be determined on the control and evaluation side 4. Therefore, the return pulse 80 is transmitted from the second light source 82 through the branch 24 to the left end of the fiber optical transmission line 6 (Fig. 1) and from there to the evaluation circuitry (Fig. 1). During the emission of the return pulse 80, the storage capacitor 56 will be discharged. Since this measuring method is based on the measurement of pulses, it can be termed pulse code modulation..
  • the storage capacitor 56 energizes the address decoder 72 and the voltage sensing device 78. It also serves as an energy source for charging and discharging the capacitor 64 and for activation of the second light source 82 which sends out the response pulse 80.
  • Fig. 4 is illustrated another embodiment of the measuring element 34, whereby only a section of the electric circuit is shown. Further components and connections may be chosen as in Fig.. 3.
  • the capacitance of the capacitor 64 may vary in accordance with the physical parameter pl, whereas the resistance of the resistor 62 is constant. Since the charging time and the iischarging time of the capacitor 64 is dependent on the capacitance, the time difference between the second and the first point of time is again a function of the physical parameter pl.
  • the first light source 10 is controlled by a control unit 86.
  • This control unit 86 provides for the emission of charge light pulses which are used for energizing the measuring elements 34-40.
  • the first light source 10 is not only a source for transmitting energy on the measuring side 2. It is also used as a signal source.
  • an encoder 88 is provided.
  • the encoder 88 controls the first light source 10 as to emit a series v of coded light pulse patterns. Each of these coded light pulse patterns addresses a particular address decoder.72 in one of the measuring elements 34-40. With each individual address decoder 72 a predetermined and individualized pulse pattern is associated.
  • Each of the decoders 72 on the measuring side 2 issues an initiation signal i when the transmitted coded light pulse pattern corresponds to the predetermined pulse pattern contained or stored therein.
  • the evaluation circuitry comprises a second receiver element 90 which is sensitive to the light of any of the second light sources 82 on the measuring side 2.
  • This second receiver element 90 preferably may be a photo diode. It is connected in series with a resistor 92 to a voltage source.
  • the second light source 90 receives the return light pulse r from the transmission line 6 and generates a second electric signal in accordance with the light received. In other words, whenever one of the second light sources 82 of the measuring elements 34-40 emits a return light.pulse 80,.an electric pulse is generated by the element 90. This pulse is conducted to a time measuring stage 94.
  • the stage 94 measures the difference between the second and the first point of time, whereby this time difference is a function of the physical parameter to be measured, and issues an output signal a accordingly.
  • the stage 94 may be a counter which is started from the control unit 86 by a start signal that coincides with the initiation signal used on the measuring side 2. The counter is stopped by the pulse from the light sensitive element 90. The time lapse between "start” and “stop” is a function of the physical parameter to be measured.
  • FIGs. 6 through 8 diagrams referring to the operation of the fiber optical sensor system are illustrated.
  • a primary optical pulse or charge pulse no. 1 is generated by the first light source 10.
  • This charge pulse no. 1 passes the beam splitter 12 and enters the optical fiber cable 6.
  • Light which passes the coupling elements 14-20 and exits from the branches 24-30 hits the photo diode 46 in each of the measuring elements 34-40, respectively.
  • the photo diode 46 converts the light into an electric voltage which charges the storage capacitor 56.
  • the capacitor 56 feeds the transducer unit 60, the address decoder 72 and the comparator 78 through the supply voltage bus 50.
  • the charge pulse no. 1 serves to charge all capacitors 56 of the measuring elements 34-40, From the trailing edge of the charge pulse no.
  • the decoder 72 determines that the charge pulse no. 1 is terminated. For instance, a flip-flop may be activated by the trailing edge. However, it is also possible to start a counter with the leading edge which delivers a termination pulse after a given period of time.
  • first address code pulses are generated. These pulses may be of smaller amplitude than the charge pulse no. 1. These first address code pulses are assigned to the first measuring element to be addressed, for instance the measuring element 34. Corresponding electrical pulses are generated and fed to the address decoder 72 for address recognition and decoding.
  • a start pulse pl is generated by the light source 10.
  • This pulse pl may have a higher amplitude than the first address code pulses.
  • the recognition of the address code in the first measuring element 34 causes the generation of the initiation signal i which initiates charging and discharging of the capacitor 64.
  • the electrical pulse corresponding to the start pulse pl is simply passed through the decoder 72 onto the first switch 70. After the fixed delay time To , this pulse will also actuate the second switch 74.
  • the trailing edge of the start pulse pl determines the first point of time tll, that is the instant when the first switch 70 is closed. At the point of time (tll + T o ), the second switch 74 is closed, whereas the first switch 70 may be opened.
  • the capacitor voltage U c will rise from the first point of time tll on and decrease after the delay time To has elapsed.
  • the capacitor voltage D c will have arrived at the predetermined value of zero volts.
  • this second point of time t12 is shifted on the time axis t when the value of the parameter pl is changed.
  • a voltage curve corresponding to a second value of the parameter pl is shown in broken lines.
  • the output signal of the comparator 78 is generated at the second po.int of time tl2. This output pulse closes the third switching element B4 which thereupon discharges the load of the storage capacitor 56 across the second light emitting element 82.
  • the stored energy is converted into a return light pulse 80 which is transmitted back into the fiber optical cable 6.
  • Fig. 8 is shown the return light pulse r which is emitted toward the evaluation circuitry 42 at the second point of time t12.
  • Fig. 8 is also shown in broken lines a return pulse r which would be created if the capacitor 64 would be charged and discharged accordingto a capacitor voltage U c following the broken lines in Fig. 7.
  • the time interval between the return pulse (time t12) and the start signal (time tll) is a measure of the value of the time constant of the RC element 62, 64 which in turn is a measure of the physical parameter pl to be measured.
  • This time interval (t12-tll) is measured by the counter 94 (see Fig. 5). In other words, the measurement of the parameter pl is performed as a measurement of a time interval.
  • the next measuring element 36 is addressed by second address code pulses at a point of time t2 (see Fig. 6).
  • the second address code is different from the first address code. Therefore, only address decoder 72 of the second measuring element 36 will now be activated to pass along the following start pulse p2.
  • the measuring element 36 sends back a return light pulse r which can be seen in Fig. 8.
  • the time difference (t22-t21) between the return pulse (see Fig. 8) and the start pulse (see Fig. 6.) is again a measure of the physical parameter p2 to which the transducer unit 60 in the second measuring element 36 is exposed.
  • the measurement of the parameters p3 and p4 is performed in the same way. After this has been accomplished, a new measurement cycle is started by emitting a charge pulse no. 2 determined to energize the measuring elements 34-40 again. Subsequently, the first pulse pattern is emitted again. This first pattern is again addressed to the first measuring element 34 which in turn will send out again a return pulse 80. Thus, a chan q e of the parameter pl between this and the preceding measurement cycle can be determined.
  • Fig. 9 is illustrated the mechanical design of a measuring element 34 which is connected through a fiber optical cable 24 and a fiber optical branching element 14 to the main fiber optical cable 6.
  • This measuring element 34 is part of a fiber optical sensor system which may have various applications. For instance, it may be applied in an automobile control device or in a process or industrial control device. Such a system can also be used for data transmission, for supervision and control in power plants, for instance in nuclear plants, and for tests in aerospace.
  • the measuring element 34 contains a housing which is formed by a container 100 and a cap 102.
  • the container 100 basically has the shape of a cylindrical pot. It is made of a metal.
  • the cap 102 forms the top of the housing. It is also made of a metal and has the shape of a cone.
  • the cap 102 contains a central cavity or light channel 104.
  • the fiber optical cable 24 merges into the top of this light channel 104.
  • the cap 102 is attached to the inner walls of the container by means of a lead screw 106 in the upper part thereof.
  • the interior of the housing is shielded against electromagnetic interference since the container 100 and the cap 102 are made of metal.
  • the interior of the housing contains a supporting plate .or board 108 which has the shape of a disc.
  • This plate or board 108 may be a circuit board carrying various electronic components.
  • it ' is a silicon chip which contains or incorporates a'plurality of components and integrated circuits that form receiver and emitter circuits.
  • the integrated circuits may be so-called large scale IC.
  • the supporting plate 10,8 is attached to the inner walls of the container by a ring (not shown) or by any other suitable means. ' , '
  • the supporting board 108 supports the first light receiving element 46.
  • This element may be a light sensitive diode, for instance, working on a silicon basis.
  • the light receiving element 46 has the shape of a disc. It is centered on the supporting plate 108 opposite the end of the fiber optical cable 24. Its diameter approximately corresponds to the width of the light channel 104.
  • This second light source 82 may be a light emitting diode (LED) or a laser, in-particular a GaAs light emitter.
  • the second light source 82 is the return signal generator, which - emits the return pulse 80. It is arranged on the central axis of the container so that it is positioned just opposite to the face end of the fiber optical cable 24.
  • the upper end face of the supporting plate 108 may also support electrical components which are designated as 110. These components may form the address decoder 72 and other circuits.
  • the lower end face of the supporting plate carries an energy storage device such as a supply or storage capacitor 56.
  • the side wall of the container contains a hole. Through this hole a lever 112 extends into the interior of the housing.
  • the lever 112 is pivotly attached to the housing by means of a pivot 114 which is located in the hole itself or close thereto.
  • the inner portion of the lever 112 has a protrusion 116 on its upper side. This protrusion 116 engages a sensor capacitor 64, the capacitance of which is variable in accordance with Fig. 4.
  • the sensor- capacitor 64 is firmly attached to the lower end face of the supporting plate 108.
  • the capacitor 64 is made of two plates between which an electrolytical fluid is arranged.
  • the sensor capacitor 64 shown in Fig. 9 is sensitive to the force exerted by the protrusion 116 of the lever 112.
  • the sensing element 34 is a force or pressure sensitive element.
  • the capacitance and consequently the voltage of the capacitor 64 vary in accordance with the parameter pl.
  • a change of this parameter pl may be, for instance, caused by a change of temperature, pressure, or flow.
  • various other sensors may be applied. For instance, there may be applied an element which changes the distance in dependence on the temperature, or which changes the dielectric constant in dependence on the temperature.
  • a housing 120 which contains a cavity 122 in the form of an ellipsoid.
  • This cavity 122 is provided with reflecting walls. That is, the walls reflect very well the wavelength of the light which is transmitted into the cavity.
  • the walls may be coated with silver.
  • the cavity 122 is sealed from the outside to preserve good optical properties.
  • the ellipsoidal cavity 122 is characterized by its focal points F 1 and F 2 .
  • a second light source 82 is located in the first focal point F 1 .
  • This light source 82 is supplied with power from the exterior
  • this light source 82 may be a GaAs laser.
  • the light emitted from the second light source 82 will be collected in the second focal point F 2 .
  • this focal point F 2 there is arranged the end face of a fiber optical cable 24 which leads out of the cavity 122.
  • Light emitted from the first light source will enter the cavity through the end face of the fiber optical cable 24. This light will be collected by the first optical receiver or photo diode 46 which is arranged around the first focal point F 1 .
  • the reflection on the ellipsoidal side walls provides for a high power coupling.
  • Fi g . 11 is illustrated the basic design of another embodiment of the measuring element 34.
  • the transmission of information according to Fig. 3 is pulse code modulated (PCM).
  • the transmission according to Fig. 11 is pulse width modulated (PWM).
  • the energy transmission and storage device may be the same as in Fig. 3.
  • the transducer 60 is energized again from the main supply voltage bus 50.
  • This transducer 60 contains a sensor 130.
  • the sensor 130 is exposed to a change of a physical parameter p, for instance, a change of a distance or temperature, and it delivers at its electrical output a control signal c.
  • This control signal c is supplied to a pulse width modulator 132 which issues pulses the length of which corresponds to the control signal c.
  • the output signal of the modulator 132 is used for activating the third switching element 84, which in turn causes the second light source 82 to emit a return light pulse 80.
  • the duration of the light pulse 80 is a function of the physical parameter p.
  • the light pulse 80 is directed to the end face of the fiber optical-cable 24 and forwarded to the evaluation circuitry 42.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Arrangements For Transmission Of Measured Signals (AREA)
  • Optical Transform (AREA)
  • Optical Communication System (AREA)
EP81110054A 1980-12-01 1981-12-01 Sensorsystem für Lichtleitfasern, vorzugsweise zum Messen physikalischer Parameter Withdrawn EP0053790A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US211681 1980-12-01
US06/211,681 US4346478A (en) 1980-12-01 1980-12-01 Fiber optical sensor system, preferably for measuring physical parameters

Publications (1)

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EP0053790A1 true EP0053790A1 (de) 1982-06-16

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US (1) US4346478A (de)
EP (1) EP0053790A1 (de)
JP (1) JPS57121794A (de)

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GB2177869A (en) * 1985-06-20 1987-01-28 Pirelli Cavi Spa Remote power transmission equipment
GB2189361A (en) * 1986-04-18 1987-10-21 Gen Electric Co Plc Optical sensor system
GB2196202A (en) * 1987-09-22 1988-04-20 Panbourne Ltd A monitoring device
FR2610126A1 (fr) * 1987-01-28 1988-07-29 Onera (Off Nat Aerospatiale) Systeme pour la commande a distance d'un dispositif electrique par voie optique
EP0307749A1 (de) * 1987-09-14 1989-03-22 Siemens Aktiengesellschaft Verfahren zur optischen Datenübertragung zwischen zwei galvanisch getrennten Sende-Empfangs-Einheiten
DE3820912A1 (de) * 1988-06-21 1989-12-28 Bayerische Motoren Werke Ag Fiberoptisches sensorsystem
US5220448A (en) * 1990-04-09 1993-06-15 Ascom Tech Ag Bit and frame synchronization unit for an access node of optical transmission equipment
US5333088A (en) * 1990-12-12 1994-07-26 British Gas Plc Data transmission system
CN101044530B (zh) * 2004-07-02 2010-05-05 古河电气工业株式会社 光供电型传感系统
EP2467881A2 (de) * 2009-08-21 2012-06-27 California Institute of Technology Systeme und verfahren zum optischen antreiben von wandlern und entsprechende wandler
US9070733B2 (en) 2012-07-25 2015-06-30 California Institute Of Technology Nanopillar field-effect and junction transistors with functionalized gate and base electrodes
US9407055B2 (en) 2012-03-01 2016-08-02 California Institute Of Technology Methods of modulating microlasers at ultralow power levels, and systems thereof

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Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2147757A (en) * 1983-10-07 1985-05-15 Gen Electric Plc Apparatus for sensing a physical property
EP0149286A1 (de) * 1984-01-06 1985-07-24 Jerome Hal Lemelson Verfahren und System zur Übertragung
GB2177869A (en) * 1985-06-20 1987-01-28 Pirelli Cavi Spa Remote power transmission equipment
GB2189361A (en) * 1986-04-18 1987-10-21 Gen Electric Co Plc Optical sensor system
GB2189361B (en) * 1986-04-18 1990-06-13 Gen Electric Plc A sensor system
US4905309A (en) * 1987-01-28 1990-02-27 Aerospatiale Societe Nationale Industrielle Optical remote control system
WO1988005980A1 (fr) * 1987-01-28 1988-08-11 Office National D'etudes Et De Recherches Aerospat Systeme pour la commande a distance d'un dispositif electrique par voie optique
EP0278835A1 (de) * 1987-01-28 1988-08-17 AEROSPATIALE Société Nationale Industrielle System zur optischen Abstandsteuerung einer elektrischen Vorrichtung
FR2610126A1 (fr) * 1987-01-28 1988-07-29 Onera (Off Nat Aerospatiale) Systeme pour la commande a distance d'un dispositif electrique par voie optique
EP0307749A1 (de) * 1987-09-14 1989-03-22 Siemens Aktiengesellschaft Verfahren zur optischen Datenübertragung zwischen zwei galvanisch getrennten Sende-Empfangs-Einheiten
GB2196202A (en) * 1987-09-22 1988-04-20 Panbourne Ltd A monitoring device
DE3820912A1 (de) * 1988-06-21 1989-12-28 Bayerische Motoren Werke Ag Fiberoptisches sensorsystem
US5220448A (en) * 1990-04-09 1993-06-15 Ascom Tech Ag Bit and frame synchronization unit for an access node of optical transmission equipment
US5333088A (en) * 1990-12-12 1994-07-26 British Gas Plc Data transmission system
CN101044530B (zh) * 2004-07-02 2010-05-05 古河电气工业株式会社 光供电型传感系统
EP2467881A2 (de) * 2009-08-21 2012-06-27 California Institute of Technology Systeme und verfahren zum optischen antreiben von wandlern und entsprechende wandler
EP2467881A4 (de) * 2009-08-21 2014-12-24 California Inst Of Techn Systeme und verfahren zum optischen antreiben von wandlern und entsprechende wandler
US9154235B2 (en) 2009-08-21 2015-10-06 California Institute Of Technology Systems and methods for optically powering transducers and related transducers
US9407055B2 (en) 2012-03-01 2016-08-02 California Institute Of Technology Methods of modulating microlasers at ultralow power levels, and systems thereof
US9070733B2 (en) 2012-07-25 2015-06-30 California Institute Of Technology Nanopillar field-effect and junction transistors with functionalized gate and base electrodes

Also Published As

Publication number Publication date
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US4346478A (en) 1982-08-24

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