阅读说明：本技术 一种光纤干涉装置及方法 (Optical fiber interference device and method ) 是由 于淼 何禹潼 *** 罗政纯 杨悦 张耀鲁 于 2019-10-30 设计创作，主要内容包括：本发明涉及一种光纤干涉装置及方法,包括调制器,调制器与激光器连接,激光器通过第一耦合器与传感臂及参考臂的一端连接,传感臂和参考臂的另一端通过第二耦合器与探测器连接,所述传感臂连接有探头,探测器与信号调理模块连接,信号调理模块与相位解调模块连接,相位解调模块包括处理模块,所述处理模块分别与第一存储器、第二存储器及第三存储器连接,第所述第三存储器与相位解缠模块连接,相位解缠模块与处理模块连接,相位解缠模块用于对第三存储器内的信号相位数据进行相位解缠,并将相位解缠后的数据传输给处理模块,本发明的光纤干涉装置测量稳定性好,测量精度高。(The invention relates to an optical fiber interference device and a method, which comprises a modulator, wherein the modulator is connected with a laser, the laser is connected with one ends of a sensing arm and a reference arm through a first coupler, the other ends of the sensing arm and the reference arm are connected with a detector through a second coupler, the sensing arm is connected with a probe, the detector is connected with a signal conditioning module, the signal conditioning module is connected with a phase demodulation module, the phase demodulation module comprises a processing module, the processing module is respectively connected with a first memory, a second memory and a third memory, the third memory is connected with a phase unwrapping module, the phase unwrapping module is connected with the processing module, the phase unwrapping module is used for phase unwrapping signal phase data in the third memory and transmitting the phase unwrapped data to the processing module, and the optical fiber interference device has good measurement stability, the measurement precision is high.)

1. An optical fiber interference device is characterized by comprising a modulator, wherein the modulator is connected with a laser, the laser is connected with one ends of a sensing arm and a reference arm through a first coupler, the other ends of the sensing arm and the reference arm are connected with a detector through a second coupler, the sensing arm is connected with a probe, the detector is connected with a signal conditioning module, the signal conditioning module is connected with a phase demodulation module, the phase demodulation module comprises a processing module, the processing module is respectively connected with a first memory, a second memory and a third memory, the first memory is used for storing signal phase data output by the processing module, the second memory is used for storing characteristic value information for signal grouping calculated by the processing module, the third memory is used for storing grouped signal phase data, and the third memory is connected with a phase unwrapping module, the phase unwrapping module is connected with the processing module and is used for performing phase unwrapping on the signal phase data in the third memory and transmitting the phase unwrapped data to the processing module.

2. The optical fiber interference device as claimed in claim 1, wherein the probe comprises a base, the base is fixedly connected to the bottom ends of a plurality of supporting columns, a mounting plate is fixed to the top ends of the supporting columns, an inductive diaphragm is connected to the mounting plate, and the inductive diaphragm is fixedly connected to the sensing arm.

3. The fiber optic interference device of claim 1 wherein the signal conditioning module comprises two mixers coupled to a detector capable of converting the optical signal to an electrical signal for transmission to the detector, the detector coupled to a processing module capable of transmitting the converted electrical signal to the processing module, both mixers coupled to a modulator capable of outputting a frequency 1 multiplied signal and a frequency 2 multiplied signal to both mixers, respectively.

4. The fiber optic interference device of claim 3 wherein a low pass filter is disposed between each of the two mixers and the processing module.

5. A method of operating an optical fiber interference device according to any one of claims 1 to 4, characterized by: the method comprises the following steps:

step 1: performing arc tangent processing on interference signals entering a phase demodulation module to obtain data sequences P1, P2, P3 … … Pi … … PN-2, PN-1 and PN of an original phase, wherein N is the number of data sequence points, and Pi represents the phase value of ith data;

step 2: taking (2m +1) sequentially adjacent data as a group, dividing the original phase data sequence into (N-2m) groups of data, calculating the root mean square value Ti of each group of data, and obtaining a plurality of groups of root mean square values which are sequentially marked as T1+ m, T2+ m … … Ti-1, Ti +1 … … TN-m-1 and TN-m;

and step 3: calculating the gradient value Di of two adjacent root mean square values: obtaining a gradient value sequence D1+ m, D2+ m … … Di-1, Di +1 … … DN-m-2 and DN-m-1;

and 4, step 4: sequentially grouping data sequences P1+ m, P2+ m … … Pi-1, Pi +1 … … PN-m-1 and PN-m of original phases, wherein if Di +1 and Di corresponding to Pi +1 and Pi simultaneously fall into a first setting range or a second setting range, Pi +1 and Pi are grouped into the same group, and if Di +1 and Di corresponding to Pi +1 and Pi respectively fall into the first setting range and the second setting range, Pi +1 and Pi are grouped into different groups;

and 5: according to the plurality of data groups obtained in the step 4, sequentially performing phase unwrapping on each data group according to the sequence of at least more data groups;

step 6: and performing interclass cyclic phase unwrapping, selecting the data group with the most data as a first reference data group, performing interclass phase unwrapping on the first reference data group and the data group with more data in two adjacent data groups to form a second reference data group, and sequentially performing interclass phase unwrapping by adopting the same method until all phase data complete phase unwrapping.

6. The operating method according to claim 5, wherein in step 2, the root mean square value Ti is calculated by:

where Pr represents the data value of the r-th original phase.

7. The method of claim 5, wherein in step 1, the arc tangent process is a four quadrant arc tangent process.

8. The operating method according to claim 7, characterized in that in step 4, the first set range is between-180 ° and 180 °, and the second set range is less than-180 ° and greater than 180 °.

Technical Field

The invention relates to the technical field of interference optical fiber sensors, in particular to an optical fiber interference device and method.

Background

The environmental physical quantity acts on the sensing optical fiber of the optical fiber interference sensor, and the phase change of an interference signal is caused. By detecting the intensity change caused by the phase change of the optical signal, the related information of the measured physical quantity can be obtained. The optical fiber interference sensor is used as an important high-sensitivity and high-precision measuring sensor, and the application range is wider and wider.

In order to avoid the influence of low-frequency noise of the light source and the detector on the optical fiber interference signal, a modulation technique is generally used to modulate the measured physical quantity to a high-frequency sideband, and then a demodulation technique is used to demodulate the measured phase information from the interference signal. The arctan demodulation method is a classical demodulation method and is very commonly applied to the optical fiber interference sensor.

The arctangent classical demodulation method comprises 4 steps of mixing, low-pass filtering and arctangent and boundary unwrapping. Firstly, respectively mixing the interference signal with the fundamental frequency and 2 frequency multiplication signals of the modulation signal to obtain G-path and H-path mixing output signals; secondly, the G path and the H path of mixed frequency output signals pass through a low-pass filter with cut-off frequency far lower than that of the modulation signals, high-frequency noise is filtered, and an LG path and an LH path which are output by the low-pass filter are respectively obtained; thirdly, dividing the LG path signal by the LH path signal, and calculating an arc tangent angle to obtain phase data from-180 degrees to +180 degrees; and fourthly, performing phase plus 360 degrees or minus 360 degrees operation on the original phase data at each phase jump edge according to the sequence order to realize phase unwrapping and obtain real phase information capable of reflecting the measured physical quantity.

The existing arc tangent phase unwrapping optical fiber interference device and method sequentially retrieve edge jump according to the sequence of an original data sequence to perform unwrapping operation, have the defects of difficult threshold selection, poor noise interference resistance and the like, and reduce the measurement precision of the optical fiber interference sensor.

The inventor finds that the most significant advantage of the fiber optic interferometric sensor is the high sensitivity, which inevitably brings about the disadvantage of being susceptible to environmental noise. When measuring physical quantities such as environmental vibration, temperature, pressure, current, magnetic field, liquid components and the like, the optical fiber interference phase information not only reflects the change of the measured physical quantities, but also is influenced by environmental noise, and the problem of large phase noise fluctuation exists. Phase fluctuation caused by noise randomly occurs at an arbitrary phase point, and phase oscillation occurs when the fluctuation point is located at a phase edge of-180 ° or +180 ° or the like. The selection of the threshold for phase unwrapping is a difficulty when using the classical arctan demodulation method. The threshold is too small to inhibit the influence of noise caused by the jump of the phase edge, so that the influence of noise on the phase information after unwrapping is more obvious; the threshold value is selected too much, redundant phase unwrapping operation can be brought, the change of measured data compared with measured physical quantity is flatter, a low-pass filter is equivalently additionally introduced, and the measurement bandwidth is reduced. The phase noise problem, which is an inherent problem of the optical fiber interference sensor, has not been solved well, and particularly in the optical fiber interference sensor of arctangent phase demodulation, the negative effect is more obvious.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide an optical fiber interference device which is high in measurement stability and measurement precision.

In order to achieve the purpose, the invention adopts the following technical scheme:

an optical fiber interference device comprises a modulator, wherein the modulator is connected with a laser, the laser is connected with one end of a sensing arm and one end of a reference arm through a first coupler, the other end of the sensing arm and the other end of the reference arm are connected with a detector through a second coupler, the sensing arm is connected with a probe, the detector is connected with a signal conditioning module, the signal conditioning module is connected with a phase demodulation module, the phase demodulation module comprises a processing module, the processing module is respectively connected with a first memory, a second memory and a third memory, the first memory is used for storing signal phase data output by the processing module, the second memory is used for storing characteristic value information for signal grouping calculated by the processing module, the third memory is used for storing grouped signal phase data, the third memory is connected with a phase unwrapping module, and the phase unwrapping module is connected with the processing module, the phase unwrapping module is used for performing phase unwrapping on the signal phase data in the third memory and transmitting the phase unwrapped data to the processing module.

Further, the probe comprises a base, the base is fixedly connected with the bottom ends of the support columns, a mounting plate is fixed to the top ends of the support columns, a sensing membrane is connected to the mounting plate, and the sensing membrane is fixedly connected with the sensing arm.

Furthermore, the signal conditioning module comprises two mixers, the two mixers are connected with the detector, the detector can convert optical signals into electric signals and transmit the electric signals to the detector, the detector is connected with the processing module and can transmit the converted electric signals to the processing module, the two mixers are connected with the modulator, and the modulator can output 1 frequency doubling signals and 2 frequency doubling signals to the two mixers respectively.

Furthermore, low-pass filters are arranged between the two mixers and the processing module.

The invention also discloses a working method of the optical fiber interference device, which comprises the following steps:

step 1: the interference signal entering the phase demodulation module is subjected to arc tangent processing to obtain data sequences P1, P2, P3 … … Pi … … PN-2, PN-1 and PN of an original phase, wherein N is the number of data sequence points, and Pi represents the phase value of the ith data.

Step 2: taking (2m +1) sequentially adjacent data as a group, dividing the original phase data sequence into (N-2m) groups of data, calculating the root mean square value Ti of each group of data, and obtaining a plurality of groups of root mean square values which are sequentially marked as T1+ m, T2+ m … … Ti-1, Ti +1 … … TN-m-1 and TN-m.

And step 3: calculating the gradient value Di of two adjacent root mean square values: di is Ti-Ti +1, and gradient value sequences D1+ m, D2+ m … … Di-1, Di +1 … … DN-m-2 and DN-m-1 are obtained.

And 4, step 4: the data sequences P1+ m, P2+ m … … Pi-1, Pi +1 … … PN-m-1 and PN-m of the original phases are grouped in sequence, if Di +1 and Di corresponding to Pi +1 and Pi simultaneously fall into a first setting range or a second setting range, the Pi +1 and the Pi are grouped into the same group, and if Di +1 and Di corresponding to Pi +1 and Pi respectively fall into the first setting range and the second setting range, the Pi +1 and the Pi are grouped into different groups.

And 5: and (4) according to the plurality of data groups obtained in the step (4), sequentially performing phase unwrapping on each data group according to the sequence of at least more data group data.

Step 6: and performing interclass cyclic phase unwrapping, selecting the data group with the most data as a first reference data group, performing interclass phase unwrapping on the first reference data group and the data group with more data in two adjacent data groups to form a second reference data group, and sequentially performing interclass phase unwrapping by adopting the same method until all phase data complete phase unwrapping.

Further, in step 2, the method for calculating the root mean square value Ti is as follows:

where Pr represents the data value of the r-th original phase.

Further, in the step 1, the arc tangent processing adopts four-quadrant arc tangent processing.

Further, in the step 4, the first setting range is between-180 ° and 180 °, and the second setting range is less than-180 ° and greater than 180 °.

The invention has the beneficial effects that:

1. according to the optical fiber interference device, the phase demodulation module processing module is connected with the phase unwrapping module through the first memory, the second memory and the third memory, the phase unwrapping module can perform phase unwrapping on the phase data grouped in the third memory instead of directly performing phase unwrapping on the phase data in the processing module, the defects that the traditional optical fiber interference device is difficult to select threshold values and poor in anti-noise interference capability are overcome, and the measurement accuracy of the optical fiber interference sensor is improved.

2. The optical fiber interference device of the invention utilizes the gradient value of the original data as the grouping basis, does not change the original data, avoids the distortion of the original data caused by the traditional filtering method and improves the measurement precision.

3. According to the optical fiber interference device, according to the data group quantity, the phase unwrapping is sequentially carried out on each data group from at least a few sequence, the data group with the most data is selected as a first reference data group, the inter-group phase unwrapping is carried out on the first reference data group and the data group with more data in two adjacent data groups to form a second reference data group, the inter-group phase unwrapping is sequentially carried out by adopting the same method until all phase data are phase unwrapped, the phase unwrapping is carried out on the sequence data without phase edge jump, the influence of a smooth data sequence on an unwrapping result is enhanced, the importance of threshold selection is weakened, the negative effect of oscillation caused by phase noise on a final measuring result is restrained, and the measuring stability is improved.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.

FIG. 1 is a schematic view of the overall structure of embodiment 1 of the present invention;

fig. 2 is a schematic diagram of a phase demodulation module according to embodiment 1 of the present invention;

FIG. 3 is a schematic structural view of a probe in accordance with embodiment 1 of the present invention;

FIG. 4 is a schematic diagram of the working principle of embodiment 2 of the present invention;

the phase demodulation module comprises a modulator 1, a laser 2, a first coupler 3, a first coupler 4, a sensing arm 5, a reference arm 6, a second coupler 7, a detector 8, a first mixer 9, a second mixer 10, a first low-pass filter 11, a second low-pass filter 12, a phase demodulation module 12-1, a processing module 12-2, a first storage 12-3, a second storage 12-4, a third storage 12-5, a phase unwrapping module 13, a base 14, a support column, a mounting plate 15 and a sensing diaphragm 16.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

For convenience of description, the words "up", "down", "left" and "right" in the present invention, if any, merely indicate correspondence with up, down, left and right directions of the drawings themselves, and do not limit the structure, but merely facilitate the description of the invention and simplify the description, rather than indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the invention.

As described in the background, the present application provides an optical fiber interference device for solving the problem of phase noise, which is significant in the conventional arctangent optical fiber interference sensor.

In an exemplary embodiment of the present application, as shown in fig. 1 to 3, an optical fiber interference device includes a modulator 1, the modulator is connected to a laser, and is capable of sending a modulation signal to a laser 2 to control the laser to generate a modulated lightwave signal, the laser is connected to a first coupler 3, the first coupler is connected to one ends of a sensing arm 4 and a reference arm 5, the other ends of the sensing arm and the reference arm are connected to a second coupler 6, the lightwave signal output by the laser is divided into two paths after passing through the first coupler, and is transmitted through the sensing arm and the reference arm respectively, the sensing arm is a sensing optical fiber, and is fixedly connected to a probe, and is capable of sensing a change of a measured physical quantity through the probe, and generating a change of a length or a refractive index, the optical fiber of the reference arm does not sense a change of the measured physical quantity, and the length and the refractive index thereof remain unchanged, the probe comprises a base 13, the base is used for fixing the probe, the base is fixedly connected with the bottom ends of a plurality of supporting columns 14, a mounting plate 15 is fixed to the top ends of the supporting columns, a sensing membrane 16 is fixed to the mounting plate, and the sensing membrane is fixed to a sensing arm and can sense the change of a measured object physical quantity.

The second coupler is connected with the detector 7, receives the light wave signals of the sensing arm and the reference arm, generates the interference phenomenon of the light wave, and outputs interference signals to the detector, and the detector is connected with the signal conditioning module, converts the interference signals into electric signals and outputs the electric signals to the signal conditioning module.

The signal conditioning module comprises a first mixer 8 and a second mixer 9 connected with the detector, the first mixer is connected with the phase demodulation module through a first low-pass filter 10, and the second mixer is connected with the phase demodulation module 12 through a second low-pass filter 11.

The first mixer and the second mixer are both connected with a modulator, and the modulator can output a frequency-1 multiplied signal for phase demodulation to the first mixer and output a frequency-2 multiplied signal for phase demodulation to the second mixer.

In this embodiment, the frequency of the signal output by the modulator to the laser is f1, the frequency of the output 1-time-multiplied signal is f2, f2 is equal to f1, the frequency of the 2-time-multiplied signal is f3, and f3 is equal to 2 times of f 2.

The second coupler outputs the interference light signal to the detector. The detector converts the optical fiber interference signal into an electric signal and outputs the electric signal to the signal conditioning module. The signal conditioning module processes the interference electric signal and outputs 2 paths of signals to the phase demodulation module. The phase demodulation module obtains real phase information capable of reflecting the measured physical quantity by using an arc tangent phase unwrapping method for feature extraction.

The phase demodulation module comprises a processing module 12-1, the processing module is an existing processor, the processing module is connected with a first low-pass filter and a second low-pass filter, and can receive electric signals of two paths of light waves and perform arc tangent processing to obtain an original phase sequence of interference light signals and calculate a characteristic value of original phase sequence data, the processing module is respectively connected with a first memory 12-2, a second memory 12-3 and a third memory 12-4, the processing module can store the calculated original phase sequence data in the first memory and store the calculated characteristic value of the original phase sequence data in the second memory, the processing module can group the original phase sequence data by using the characteristic value and store the original phase sequence data in the third memory, and the third memory is connected with the phase unwrapping module 12-5, the phase unwrapping module can perform phase unwrapping on the data grouped in the third memory, is connected with the processing module, and can transmit the unwrapped data to the processing module. The first memory, the second memory and the third memory can be the existing memories, and the phase unwrapping module can be the existing adder or multiplier.