CN1093640C - Integral compensation fibre-optic current sensor - Google Patents

Abstract

The invention relates to an optical fiber current sensor, which is composed of a light source, a wavelength division multiplexer, a sensing head, an input optical fiber, an output optical fiber, a light detector and the like. It adopts standard transmission optical fiber, and designs the polarization state control structure, so that the loss and polarization state disturbance caused by the optical fiber can be reduced. The sensor head structure is greatly simplified. The device of the invention is particularly suitable for high-voltage and high-current test and measurement applications in power systems.

Description

Integrated Compensation Fiber Optic Current Sensor

The invention relates to an optical fiber current sensor, which has the comprehensive compensation function of temperature and polarization state, and is especially suitable for the application of high-voltage and large-current test and measurement in electric power system.

At present, the all-fiber fiber optic current sensor developed at home and abroad needs to use special magneto-optic fiber and polarization maintaining transmission fiber, which is expensive; the fiber optic current sensor with block structure uses multimode fiber to avoid the disturbance of the polarization state of the transmitted light wave in the fiber, but the actual The multimode optical fiber still has random disturbance of polarization state comparable to the current sensing signal, and the multimode optical fiber is easily affected by the external environment to cause loss fluctuations, which makes the output optical signal unstable and causes detection errors. On the other hand, the Verdet constant of magneto-optical materials changes with temperature, and temperature compensation is required. In the existing temperature compensation technology, such as Taiwan's invention patent "Temperature Compensated Fiber Optic Current Sensor" (Notice No. 234742, Application No. 83102850, inventors Li Yanzheng and Li Guocheng), it is the combination of current sensing and temperature sensing optical path Separated, the structure of the resulting sensing head is relatively complex and susceptible to interference, resulting in inaccurate temperature measurement and affecting temperature compensation performance.

For the shortcoming that above-mentioned prior art exists, the object of the present invention is: (1) the device of the present invention has designed the optical fiber polarization state control structure, both can adopt multimode optical fiber and also can adopt single mode optical fiber, have the perturbation to optical fiber polarization state The function of automatic compensation; (2) The device of the present invention also has the function of temperature compensation, and the optical circuit of temperature sensing and current sensing is combined into one, which greatly simplifies the structure of the sensor head.

The optical fiber current sensor of the present invention is composed of a light source, a wavelength division multiplexer, a sensor head, an input optical fiber, an output optical fiber, and a photodetector. Two light sources 1 and 2 are used to generate light beams of two wavelengths λ ₁ and λ ₂ , and the light beams of two wavelengths are coupled into the input optical fiber 4 by a wavelength division multiplexer 3 and transmitted to the sensor head 5, the sensor head It is composed of a polarization beam splitter 6, a magneto-optical element 7, a temperature sensing element 8 and a polarization analyzer coupler 9 connected sequentially. The sensor head is connected with another wavelength division multiplexer 11 through an output optical fiber 10. The wavelength division multiplexer The optical signal of the two wavelengths transmitted in the output fiber is separated by a device and sent to two optical detectors 12 and 13, and the optical signal is converted into an electrical signal by the optical detector.

The temperature compensation of the present invention is realized by the following technology: in the sensing head 5, when the optical signals of the wavelengths λ ₁ and λ ₂ transmitted by the input optical fiber 4 pass through the temperature sensing element 8, a wavelength (λ ₁ ) light wave intensity changes with the temperature change to form a temperature measurement signal, while the light wave intensity of another wavelength (λ ₂ ) does not change with temperature to form a temperature measurement reference signal, which is sent to the wavelength division multiplexer 11 through the output optical fiber 10 The optical signals of the two wavelengths are separated and photoelectrically converted by the photodetectors 12 and 13, and then sent to the subsequent signal processing unit to output a temperature signal, which is used for temperature compensation by the current sensor.

The polarization state compensation of the present invention is realized by following technology: in sensor head 5, the arbitrary polarization state light signal that the wavelength that transmits by input optical fiber 4 is λ ₂ is divided into two bundles of polarization states perpendicular to each other by polarization beam splitter 6 Linearly polarized light, when they pass through the magneto-optical element 7, their polarization state changes with the current signal, and then the polarization state of the two beams of light waves is detected by the analyzer coupler 9, and the polarization state of the light wave changes with the current into light intensity With the change of the current, the two beams of light waves are coupled into the output optical fiber 10, demultiplexed by the wavelength division multiplexer 11 and photoelectrically converted by the photodetector 13, and then sent to the subsequent signal processing unit to output the current signal. Since the polarization state perturbation has opposite polarity on the influence of the two linearly polarized lights, they cancel each other out, so that the output current signal has nothing to do with the input polarization state of the light wave, that is, the control and compensation of the polarization state are realized.

Advantages of the present invention: (1) Standard transmission optical fiber can be used, which reduces device cost; (2) The polarization state automatic control and compensation structure of the optical fiber is designed, so that the polarization state and loss disturbance caused by the optical fiber can be reduced; (3) Combining the current sensing and temperature sensing optical paths into one greatly simplifies the structure of the sensing head. At the same time, dual-wavelength detection technology can be used to improve the stability and reliability of temperature detection and enhance the effect of temperature compensation.

The accompanying drawings are as follows:

Accompanying drawing 1, the schematic diagram of the structure of the comprehensive compensation fiber optic current sensor.

Claims (1)

1, a kind of optical fiber current sensor, is made up of light source, wavelength division multiplexer, sensing head, input optical fiber, output optical fiber and photodetector etc., it is characterized in that: Two light sources are used to generate light beams of two wavelengths λ ₁ and λ ₂ , and a wavelength division multiplexer is used to couple the light beams of two wavelengths into the input optical fiber and transmit them to the sensor head. The sensor head is composed of a polarization beam splitter, a magnetic The optical element, the temperature sensing element and the polarization analyzer coupler are connected in sequence, and the sensor head is connected with another wavelength division multiplexer through the output fiber, and the wavelength division multiplexer will output the two wavelengths transmitted in the fiber The light beam is split and sent to two photodetectors, which convert the optical signal into an electrical signal; The temperature and current sensing optical signals are input and output by the same optical fiber and pass through the magneto-optical element and the _temperature sensing element at the same _time . When heating the element, the light wave intensity of one wavelength λ ₁ changes with the temperature to form a temperature measurement signal, while the light wave intensity of the other wavelength λ ₂ does not change with the temperature, which constitutes a temperature measurement reference signal, which is passed through the wavelength division multiplexer and The light detector outputs a sensor temperature compensation signal; In the sensor head, the optical signal of arbitrary polarization state with a wavelength of _λ2 transmitted from the input optical fiber is divided into two beams of linearly polarized light whose polarization states are perpendicular to each other by the polarization beam splitter. When they pass through the magneto-optical element, their polarization states follow the The current signal changes, and then the polarization state of the two light waves is detected by the polarization analyzer coupler, and the change of the polarization state of the light wave with the current is converted into the change of the light intensity with the current, and the two light waves are coupled into the output fiber for multiplexing The detector and photodetector output a current signal independent of the polarization state of the input light wave.

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