CN117233448A - Optical fiber current transformer with controllable delay time - Google Patents
Optical fiber current transformer with controllable delay time Download PDFInfo
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- CN117233448A CN117233448A CN202210646088.9A CN202210646088A CN117233448A CN 117233448 A CN117233448 A CN 117233448A CN 202210646088 A CN202210646088 A CN 202210646088A CN 117233448 A CN117233448 A CN 117233448A
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- 239000013307 optical fiber Substances 0.000 title claims abstract description 70
- 238000009825 accumulation Methods 0.000 claims abstract description 25
- 238000006243 chemical reaction Methods 0.000 claims abstract description 20
- 239000000835 fiber Substances 0.000 claims description 13
- 230000000737 periodic effect Effects 0.000 claims description 7
- 230000010354 integration Effects 0.000 claims description 5
- 230000003287 optical effect Effects 0.000 claims description 5
- 239000000919 ceramic Substances 0.000 claims description 3
- 230000001105 regulatory effect Effects 0.000 abstract description 3
- 239000013078 crystal Substances 0.000 description 5
- 238000010586 diagram Methods 0.000 description 5
- 238000000034 method Methods 0.000 description 4
- 239000004020 conductor Substances 0.000 description 3
- 238000001514 detection method Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000008602 contraction Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000011410 subtraction method Methods 0.000 description 1
Abstract
The invention discloses an optical fiber current transformer with controllable delay time, which is characterized in that a photoelectric conversion unit, an error accumulation unit, a delay control unit and a variable delay unit are added in a traditional optical fiber interferometer, and the intrinsic period of the optical fiber interferometer is regulated in real time to be always and accurately equal to the half period of a modulation square wave, so that an additional pulse signal introduced by period mismatch is eliminated, and zero bias current error of the optical fiber current transformer is eliminated, and the intrinsic period of the optical fiber interferometer is dynamically regulated and is matched with the modulation square wave period in real time.
Description
Technical Field
The invention relates to the technical field of optical fiber sensing, in particular to an optical fiber current transformer with controllable delay time.
Background
The existing closed-loop detection type optical fiber current transformer adopts a reflection type optical fiber interferometer, and realizes closed-loop tracking detection of current by applying square wave and step wave signals to an electro-optic phase modulator. Ideally, the intrinsic period of the fiber interferometer is half of the modulated square wave, but the square wave is usually generated by an FPGA or other digital circuits, the period of the square wave is determined by the crystal oscillator frequency, and continuous adjustment is difficult, so that period misalignment is caused. In practice, the square wave period can only be approximately adjusted to the required size by software setting, but a small amount of misalignment cannot be completely avoided. The square wave period is misaligned to cause the interference light intensity to generate a positive pulse signal at the head or tail of the half period of the square wave, which causes an additional zero bias current error in the output signal of the optical fiber current transformer to influence the measurement accuracy.
The existing solution is to subtract the zero offset error in software, but the zero offset error changes along with the temperature due to the influence of factors such as thermal expansion, cold contraction and the like, so that the error subtraction method is disabled. There are also voltage-controlled crystal oscillators used instead of fixed frequency crystal oscillators, and the problem of cycle misalignment is eliminated by adjusting the crystal oscillator frequency by voltage, but the voltage-controlled crystal oscillator is generally limited in the frequency range that can be changed, and the frequency cannot be continuously adjusted, so that there is inevitably residual misalignment, and the problem cannot be fundamentally solved.
Disclosure of Invention
Therefore, in order to solve the problem of misalignment of the intrinsic period and the half period of the modulated square wave of the conventional interferometer, the invention provides the optical fiber current transformer with controllable delay time, so as to realize the dynamic adjustment of the intrinsic period of the optical fiber interferometer and the real-time matching of the intrinsic period and the modulated square wave period.
In order to achieve the above purpose, the present invention provides the following technical solutions:
the invention provides an optical fiber current transformer with controllable delay time, which comprises the following components: photoelectric conversion unit, error accumulation unit, delay control unit, variable delay unit and optical fiber interferometer, wherein the optical fiber interferometer includes: the photoelectric detector is connected with the optical fiber measuring coil through the optical fiber;
the photoelectric conversion unit is used for converting the light intensity signal received by the photoelectric detector into a voltage signal with equal proportion;
the error accumulation unit is used for performing characteristic analysis on the voltage signal output by the photoelectric conversion unit to obtain a periodic misalignment error signal;
the delay control unit controls the variable delay unit according to the periodic misalignment error signal, and the variable delay unit changes the light wave delay time through voltage control, wherein the magnitude of the light wave delay time and the control voltage amplitude form a positive correlation;
the fixed delay optical fiber is positioned between the electro-optic phase modulator and the optical fiber measuring coil, and the variable delay unit is positioned between the electro-optic phase modulator and the fixed delay optical fiber or between the fixed delay optical fiber and the optical fiber measuring coil.
In one embodiment, the duty cycle of the modulated square wave signal applied to the electro-optic phase modulator is 50%.
In an embodiment, the error accumulation unit includes: the optical fiber interferometer comprises an demodulation multiplication circuit, an integration circuit and an addition circuit, wherein the demodulation multiplication circuit adopts two different demodulation square waves, when the intrinsic period of the optical fiber interferometer is smaller than half of the period of a modulation square wave, positive pulses exist at the head part of the half period of the square wave, and the demodulation multiplication circuit is used for performing demodulation on the positive pulses and then integrating and accumulating the positive pulses through the integration circuit to obtain a positive error signal; when the intrinsic period of the optical fiber interferometer is greater than half of the period of the modulated square wave, positive pulses exist at the tail part of the half period of the square wave; the positive pulse is subjected to phase discrimination by a phase discrimination circuit and then is integrated and accumulated by an integrating circuit to obtain a negative error signal; the adding circuit adds up all the positive and negative error signals to obtain an output signal of the error accumulating unit.
In one embodiment, the delay control unit inverts the output signal of the error accumulation unit, performs PID processing, and outputs the inverted output signal to the variable delay unit; or the output signal of the error accumulation unit is processed by PID and then is reversely output to the variable delay unit.
In one embodiment, the variable delay unit is an electronically controlled optical delay line.
In one embodiment, the variable delay unit is a cylindrical piezoelectric ceramic tightly wound around an optical fiber.
In one embodiment, the delay control unit is an analog PID circuit.
In one embodiment, the delay control unit includes an analog-to-digital conversion circuit, a digital PID circuit, and a digital-to-analog conversion circuit.
The technical scheme of the invention has the following advantages:
1. the optical fiber current transformer with controllable delay time provided by the invention has the advantages that the intrinsic period of the optical fiber interferometer is regulated in real time to be always and accurately equal to the half period of the modulated square wave, so that the additional pulse signal introduced by period mismatch is eliminated, and the zero bias current error of the optical fiber current transformer is further eliminated.
2. The optical fiber current transformer with controllable delay time comprises an error accumulation unit multiplication identifying method circuit, an addition circuit and an integration circuit, wherein the phase relation between phase identifying square waves and modulation square waves is clear and simple, and the phase identifying square waves and the modulation square waves are easy to generate.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is an equivalent optical path diagram of an example of a fiber optic current transformer with controllable delay time provided in an embodiment of the present invention;
FIG. 2 is a schematic diagram of a timing relationship of an additional pulse signal in interference light intensity under the condition of misalignment between an intrinsic period of an optical fiber interferometer and a half period of a modulated square wave, and a schematic diagram of matching the intrinsic period of the optical fiber interferometer with the period of the modulated square wave after dynamic adjustment;
FIG. 3 is a schematic diagram of two phase discrimination square waves used by the error accumulation unit according to the embodiment of the present invention;
fig. 4 is a schematic circuit diagram of an embodiment of an error accumulation unit according to the present invention.
Reference numerals:
1-a light source; 2-a photodetector; a 3-coupler; 4-polarizer; a 5-electro-optic phase modulator; 6-a fixed delay fiber; 7-an optical fiber measuring coil; 8-through-current conductors.
Detailed Description
The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In addition, the technical features of the different embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
Examples
The invention provides an optical fiber current transformer with controllable delay time, which is characterized in that a photoelectric conversion unit, an error accumulation unit, a delay control unit and a variable delay unit are added in a traditional optical fiber interferometer, wherein the optical fiber interferometer comprises: the device comprises a light source, a photoelectric detector, a coupler, a polarizer, an electro-optic phase modulator, a fixed delay optical fiber and an optical fiber measuring coil. Fig. 1 shows an optical connection relationship between a light source 1, a photodetector 2, a coupler 3, a polarizer 4, an electro-optical phase modulator 5, a variable delay unit, a fixed delay optical fiber 6, an optical fiber measuring coil 7, a through-flow conductor 8 (it should be noted that the through-flow conductor is not a part of an optical fiber interferometer, and is marked for showing a manner of use of an optical fiber current transformer), and a circuit connection relationship between the photodetector 2 and a photoelectric conversion unit, an error accumulation unit, a delay control unit, and a variable delay unit.
It should be noted that in the embodiment of fig. 1, the variable delay unit is located between the electro-optic phase modulator 5 and the fixed delay fiber 6, and in other implementations, the variable delay unit may be located between the fixed delay fiber 6 and the fiber measuring coil 7.
In the embodiment of the invention, the photoelectric conversion unit is used for converting the light intensity signal received by the photoelectric detector into a voltage signal with equal proportion; the error accumulation unit is used for performing characteristic analysis on the voltage signal output by the photoelectric conversion unit to obtain a periodic misalignment error signal; the delay control unit controls the variable delay unit according to the periodic misalignment error signal, and the variable delay unit changes the light wave delay time through voltage control, wherein the magnitude of the light wave delay time and the control voltage amplitude form positive correlation, and the variable delay unit is a cylindrical piezoelectric ceramic or an electric control optical delay line tightly wound with an optical fiber.
In the embodiment of the invention, as shown in fig. 2, the duty ratio of the modulated square wave signal applied to the electro-optic phase modulation is 50%, the intrinsic period of the optical fiber interferometer is exactly equal to half of the period of the modulated square wave by adjusting the intrinsic period of the optical fiber interferometer, and the output voltage of the photoelectric conversion unit is a straight line, so that the additional pulse signal introduced by period mismatch is eliminated, and the zero bias current error of the optical fiber current transformer is further eliminated.
An error accumulation unit in an embodiment of the present invention includes: the demodulation circuit, the adder circuit and the integrator circuit are shown in fig. 4, and the demodulation circuit may be a multiplier, and the adder circuit may be an adder. The specific implementation process of the error accumulation unit is as follows:
(1) When the intrinsic period of the optical fiber interferometer is less than half of the modulating square wave period, positive pulses exist at the head part of the square wave half period (as shown in figure 2), and after phase discrimination is carried out on the positive pulses through a multiplier, the positive pulses are integrated and accumulated through an integrating circuit to obtain a positive error signal;
(2) When the intrinsic period of the optical fiber interferometer is greater than half of the period of the modulated square wave, as shown in fig. 2, positive pulses exist at the tail part of the half period of the square wave (as shown in fig. 2), and the positive pulses are integrated and accumulated through an integrating circuit after phase discrimination to obtain a negative error signal;
(3) The adding circuit adds up all the positive and negative error signals to obtain an output signal of the error accumulating unit.
In the embodiment of the invention, the delay control unit can be an analog PID circuit, and firstly, the output signal of the error accumulation unit is inverted, and then PID processing is carried out and then the output signal is output to the variable delay unit; or the analog-digital conversion, digital PID circuit and digital-analog conversion circuit are used for carrying out the analog-digital conversion, digital signal processing and digital-analog conversion, and the output signal of the error accumulation unit is firstly subjected to PID processing and then is inverted. The control objective of the delay control unit is to make the output of the error accumulation unit zero, which makes the intrinsic period of the optical fiber interferometer equal to the half period of the modulated square wave, and no additional pulse signal exists in the interference light intensity.
The optical fiber current transformer with controllable delay time provided by the embodiment is implemented in the actual modulation process by the following steps:
(1) Acquiring an error signal caused by misalignment of an intrinsic period of the optical fiber interferometer and a half period of the modulation square wave, referring to fig. 2;
(2) Integrating and accumulating the periodic misalignment error signal through an error accumulation unit, wherein the specific embodiment of the error accumulation unit refers to fig. 4, and two phase discrimination square waves and the phase relation between the two phase discrimination square waves and the modulation square wave adopted in fig. 4 refer to fig. 3;
(3) The output of the error accumulation unit is sent to a delay control unit, the delay control unit adopts a PID negative feedback adjustment method, and the output of the delay control unit acts on a variable delay unit;
(4) The variable delay unit is the last execution unit, and the output signal of the delay control unit is used for changing the intrinsic period of the optical fiber interferometer to be exactly equal to the half period of the modulated square wave.
According to the embodiment, the intrinsic period of the optical fiber interferometer is adjusted in real time to be always and accurately equal to the half period of the modulated square wave, so that an additional pulse signal introduced by period mismatch is eliminated, and zero bias current error of the optical fiber current transformer is further eliminated.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.
Claims (8)
1. A fiber optic current transformer with controllable delay time, comprising: photoelectric conversion unit, error accumulation unit, delay control unit, variable delay unit and optical fiber interferometer, wherein the optical fiber interferometer includes: the photoelectric detector is connected with the optical fiber measuring coil through the optical fiber;
the photoelectric conversion unit is used for converting the light intensity signal received by the photoelectric detector into a voltage signal with equal proportion;
the error accumulation unit is used for performing characteristic analysis on the voltage signal output by the photoelectric conversion unit to obtain a periodic misalignment error signal;
the delay control unit controls the variable delay unit according to the periodic misalignment error signal, and the variable delay unit changes the light wave delay time through voltage control, wherein the magnitude of the light wave delay time and the control voltage amplitude form a positive correlation;
the fixed delay optical fiber is positioned between the electro-optic phase modulator and the optical fiber measuring coil, and the variable delay unit is positioned between the electro-optic phase modulator and the fixed delay optical fiber or between the fixed delay optical fiber and the optical fiber measuring coil.
2. The controllable-delay-time fiber optic current transformer of claim 1, wherein the duty cycle of the modulated square wave signal applied to the electro-optic phase modulator is 50%.
3. The delay time controllable fiber optic current transformer of claim 2, wherein the error accumulation unit comprises: the optical fiber interferometer comprises an demodulation multiplication circuit, an integration circuit and an addition circuit, wherein the demodulation multiplication circuit adopts two different demodulation square waves, when the intrinsic period of the optical fiber interferometer is smaller than half of the period of a modulation square wave, positive pulses exist at the head part of the half period of the square wave, and the demodulation multiplication circuit is used for performing demodulation on the positive pulses and then integrating and accumulating the positive pulses through the integration circuit to obtain a positive error signal; when the intrinsic period of the optical fiber interferometer is greater than half of the period of the modulated square wave, positive pulses exist at the tail part of the half period of the square wave; the positive pulse is subjected to phase discrimination by a phase discrimination circuit and then is integrated and accumulated by an integrating circuit to obtain a negative error signal; the adding circuit adds up all the positive and negative error signals to obtain an output signal of the error accumulating unit.
4. The optical fiber current transformer with controllable delay time according to claim 1 or 3, wherein the delay control unit inverts the output signal of the error accumulation unit, performs PID processing, and outputs the inverted output signal to the variable delay unit; or the output signal of the error accumulation unit is processed by PID and then is reversely output to the variable delay unit.
5. The controllable-delay-time fiber optic current transformer of claim 1, wherein the variable delay unit is an electronically controlled optical delay line.
6. The controllable-delay-time fiber optic current transformer of claim 1, wherein the variable delay element is a cylindrical piezoelectric ceramic tightly wrapped around the optical fiber.
7. The fiber optic current transformer of claim 1, wherein the delay control unit is an analog PID circuit.
8. The controllable-delay-time fiber optic current transformer of claim 1, wherein the delay control unit comprises an analog-to-digital conversion circuit, a digital PID circuit, and a digital-to-analog conversion circuit.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210646088.9A CN117233448A (en) | 2022-06-08 | 2022-06-08 | Optical fiber current transformer with controllable delay time |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210646088.9A CN117233448A (en) | 2022-06-08 | 2022-06-08 | Optical fiber current transformer with controllable delay time |
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| CN117233448A true CN117233448A (en) | 2023-12-15 |
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| CN202210646088.9A Pending CN117233448A (en) | 2022-06-08 | 2022-06-08 | Optical fiber current transformer with controllable delay time |
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- 2022-06-08 CN CN202210646088.9A patent/CN117233448A/en active Pending
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