CN110608761B - Optical fiber interference device and method capable of eliminating associated amplitude modulation - Google Patents
Optical fiber interference device and method capable of eliminating associated amplitude modulation Download PDFInfo
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- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
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Abstract
The invention relates to an optical fiber interference device and a method capable of eliminating associated amplitude modulation, wherein the optical fiber interference device comprises an optical fiber interferometer, the optical fiber interferometer comprises a laser and a first coupler, the laser can transmit signals to the first coupler, the first coupler is connected with a probe part, the optical fiber interference device is characterized in that an output end of the probe part and the first coupler are respectively connected with a first mixer and a second mixer through a photoelectric detector, the first mixer and the second mixer are respectively connected with a third mixer and the laser, the laser can output signals to the first mixer and the second mixer, the first mixer and the second mixer can output the signals to the third mixer, the third mixer is connected with a controller, the photoelectric detector is also connected with the controller, and the optical signals output by the first coupler and the probe part can be converted into electric signals to be transmitted to the controller.
Description
Technical Field
The invention relates to the technical field of optical fiber interferometers, in particular to an optical fiber interference device and method capable of eliminating associated amplitude modulation.
Background
The interference type optical fiber sensor utilizes light to carry out light interference in an optical fiber, utilizes the light interference phenomenon to measure the phase change of interference light, indirectly measures physical quantity by measuring the phase change of the interference light, and comprises vibration, stress, displacement, speed and the like. Typical applications for such fiber optic sensors include fiber optic gyroscopes, fiber optic vibration detectors, fiber optic hydrophones, fiber optic level gauges, fiber optic seismometers, fiber optic strain gauges, and the like. The optical fiber gyroscope can be applied to monitoring rocket flight state, satellite running state and the like; the optical fiber vibration detector can be applied to perimeter security and the like, the optical fiber seismometer can monitor large-amplitude signals such as earthquake, nuclear explosion and the like, and Zumberge et al point out that the dynamic range of the optical fiber vibration detector is 180dB to 1kHz or so; the optical fiber hydrophone is mainly used for monitoring underwater invisible targets, blind areas which cannot be detected by a radar, and compared with the traditional hydrophone, the optical fiber hydrophone array has the characteristics of good directivity, large working bandwidth and the like; the optical fiber level meter is mainly applied to detecting the structural health of bridges, buildings and wind driven generators; the optical fiber strain gauge can measure ultra-low frequency physical processes, such as tides, and the working frequency band of the optical fiber strain gauge can reach 0.001Hz at the minimum. For the phase change in the optical path, a specific algorithm needs to be used for solving, and a common phase demodulation algorithm can be divided into: active detection, passive detection, heterodyne detection, homodyne detection, and the like. The phase generation carrier algorithm (PGC) in the active homodyne method has the characteristics of simple structure and high resolution, and is widely applied to sensors such as fiber seismometers, fiber hydrophone arrays and the like (CN 20081017296. X). But the fluctuation of light intensity caused by unstable power due to the fact that high-frequency carrier alternating current is injected into the laser in the internal modulation process is called as an associated amplitude modulation effect.
The inventor finds that in the practical application process, the acquisition positions of the two detection signals on the optical path may be separated by more than ten highways or hundreds of kilometers, and at this time, the conventional method of compensating the associated amplitude modulation effect can lead to the distortion of the suppression signal of the high-frequency direct current light intensity part, thereby causing the signal adjustment distortion.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, provides an optical fiber interference device capable of eliminating the associated amplitude modulation, solves the problem of signal distortion suppression of a high-frequency direct current light intensity part caused by different signal acquisition positions, and improves the stability and practicability of the optical fiber interference device.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
The utility model provides a can carry out optical fiber interference device that eliminates to accompanying amplitude modulation, including the optical fiber interferometer, the optical fiber interferometer includes laser instrument and first coupler, the laser instrument can be to first coupler transmission signal, first coupler is connected with probe portion, the output of probe portion and first coupler are connected with first mixer and second mixer through photoelectric detection spare respectively, first mixer and second mixer are connected with third mixer and laser instrument, the laser instrument can be to first mixer and second mixer output signal, first mixer and second mixer can be with signal output for third mixer, third mixer is connected with the controller, photoelectric detection spare still is connected with the controller, can be with the optical signal conversion of first coupler and probe portion output for the signal transmission to the controller.
Further, the controller is connected with the laser and can control the laser to send out a set signal.
Further, the probe part comprises a second coupler and a third coupler, the second coupler and the third coupler are connected with two ends of the first interference arm and two ends of the second interference arm, a filter element is arranged on the second interference arm, and the third coupler is connected with the photoelectric detection element.
Further, the probe portion is connected with the first coupler through the optical circulator, the optical circulator is connected with the second photoelectric detector, the probe portion comprises a fourth coupler connected with the optical circulator, the fourth coupler is connected with one ends of a third interference arm and a fourth interference arm, the other ends of the third interference arm and the fourth interference arm are respectively connected with a first reflecting mirror and a second reflecting mirror, a filtering piece is arranged on the fourth interference arm, the first reflecting mirror and the second reflecting mirror can transmit optical signals to the optical circulator in a reflecting mode, and the optical circulator is connected with the photoelectric detector and can transmit reflected optical signals to the photoelectric detector.
Further, the photoelectric detection piece comprises a first photoelectric detector and a second photoelectric detector, the input end of the first photoelectric detector is connected with the first coupler, the output end of the first photoelectric detector is connected with the first mixer and the controller, the input end of the second photoelectric detector is connected with the output end of the probe part, and the output end of the second photoelectric detector is connected with the second mixer and the controller.
Further, the filter element adopts a passive optical fiber filter or an active optical switch.
Further, the probe portion includes a fifth coupler and a sixth coupler, a fifth interference arm and a sixth interference arm are connected between the fifth coupler and the sixth coupler, and the sixth interference arm is provided with a seventh coupler.
Further, the photoelectric detection part comprises a third photoelectric detector, a fourth photoelectric detector and a fifth photoelectric detector, the input end of the third photoelectric detector is connected with the first coupler, the output end of the third photoelectric detector is connected with the laser and the first mixer, the input end of the fourth photoelectric detector is connected with the seventh coupler, the output end of the fourth photoelectric detector is connected with the second mixer, the input end of the fifth photoelectric detector is connected with the sixth coupler, and the output end of the fifth photoelectric detector is connected with the controller.
The invention also discloses a working method of the optical fiber interference device capable of eliminating the associated amplitude modulation, wherein the laser, the first coupler and the photoelectric detection piece form a first optical path, and the laser, the first coupler, the detection part and the photoelectric detection piece form a second optical path;
The laser sends out a ranging modulation signal, the ranging modulation signal enters a first mixer through a first optical path, the first mixer receives and mixes signals of the laser and the first optical path to obtain a first difference frequency signal, the second mixer receives and mixes signals of the laser and signals of a second optical path to obtain a second difference frequency signal, the first difference frequency signal and the second difference frequency signal are transmitted to a third mixer to be mixed to obtain a difference frequency signal of optical path difference delta L between the first optical path and the second optical path, the difference frequency signal is transmitted to a controller, and the controller obtains a phase difference when signals of the two optical paths reach a photoelectric detection part according to the difference frequency signal of the optical path difference
The laser emits light signals, the controller receives the output light signals of the first light path and the second light path through the photoelectric detection part, and the obtained phase difference is obtainedAnd dividing the optical signal data detected by the photoelectric detection part of the second optical path by the optical signal data with the phase difference output by the photoelectric detection part of the first optical path in the optical signals output by the photoelectric detection part with the first optical path to obtain the data of the interference optical signals.
Further, the phase difference calculating method comprises the following steps:
Wherein C n is the transmission speed of light in the optical fiber; v (t) is the optical frequency.
The invention has the beneficial effects that:
The optical fiber interference device capable of eliminating the associated amplitude modulation comprises a first mixer, a second mixer and a third mixer, wherein the optical path difference between a first optical path and a second optical path can be obtained by utilizing a modulation signal output by a laser, so that the phase difference of output signals of the two optical paths is obtained, when the laser emits an optical signal, the acquired phase difference is brought into the optical signal output by the first optical path, and then the output optical signal data of the second optical path is divided by the optical signal data after the first optical path is brought into the phase difference, so that interference data is obtained, the problem of signal distortion suppression of a high-frequency direct-current light intensity part caused by different signal acquisition positions is solved, the problem of the phase difference elimination of the associated amplitude modulation generated by the optical fiber interferometer in long-distance practical application is solved, the normal work of the optical fiber interferometer in long-distance application is realized by measuring the phase difference caused by different signal acquisition positions, and the stability and the practicability of the optical fiber interferometer are improved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application.
FIG. 1 is a schematic view of the overall structure of embodiment 1 of the present invention;
FIG. 2 is a schematic overall structure of embodiment 2 of the present invention;
FIG. 3 is a schematic overall structure of embodiment 3 of the present invention;
The laser device comprises a laser device 1, a first coupler 3, a second coupler 4, a third coupler 5, a first interference arm 6, a second interference arm 7, a first optical fiber filter 8, a first photoelectric detector 9, a second photoelectric detector 10, a first mixer 11, a second mixer 12, a third mixer 13, a controller 14, an optical circulator 15, a fourth coupler 16, a third interference arm 17, a fourth interference arm 18, a first reflector 19, a second reflector 20, a second optical fiber filter 21, a fifth coupler 22, a sixth coupler 23, a fifth interference arm 24, a sixth interference arm 25, a seventh coupler 26, a fourth photoelectric detector 27, a third photoelectric detector 28, and a fifth photoelectric detector.
Detailed Description
It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the application. 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 exemplary embodiments according to the present application. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.
For convenience of description, the words "upper", "lower", "left" and "right" in the present invention, if they mean only that the directions are consistent with the upper, lower, left, and right directions of the drawings per se, and do not limit the structure, only for convenience of description and simplification of the description, but do not indicate or imply that the apparatus or element to be referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.
As described in the background art, when the existing method for compensating the associated amplitude modulation effect is applied to the condition of long acquisition position distance, the problem of suppression signal distortion of a high-frequency direct current light intensity part is caused by direct current light intensity phase difference easily, and the application provides an optical fiber interference device capable of eliminating the associated amplitude modulation.
In an exemplary embodiment 1 of the present application, as shown in fig. 1, an optical fiber interference device capable of eliminating accompanying amplitude modulation includes an optical fiber interferometer, where the optical fiber interferometer adopts a mach-zehnder interferometer, the optical fiber interferometer includes a laser 1, the laser adopts a DFB laser, the DFB laser is connected to a first coupler 2 through an optical fiber, the first coupler is capable of splitting an optical signal output by the DFB laser, a 1X2 coupler of 99:1 is used as the first coupler, 99% of a light-passing port of the first coupler is connected to a probe portion, the probe portion includes a second coupler 3 and a third coupler 4, the second coupler is connected to 99% of a light-passing port of the first coupler, the second coupler adopts a 1X2 coupler of 50:50, two light-passing ports of the second coupler are respectively connected to one ends of a first interference arm 5 and a second interference arm 6, the other ends of the first arm and the second arm are connected to the third coupler, and the third coupler adopts a 50:50 interference coupler.
The second interference arm is connected with a filter element, the filter element adopts a passive first optical fiber filter 7, the optical fiber filter can prevent the linear frequency modulation signal from passing and can not prevent the optical signal for interference from passing, and the problem of distance measurement can not be solved if the interference signal exists during distance measurement, so that the optical fiber filter is arranged, and the interference of the signal during distance measurement is avoided.
The first coupler and the third coupler are both connected with the photoelectric detection part, the photoelectric detection part comprises a first photoelectric detector 8 and a second photoelectric detector 9, 1% of light passing ports of the first coupler are connected with the input end of the first photoelectric detector, and the third coupler is connected with the input end of the second photoelectric detector.
The first photoelectric detector can receive the signal transmitted by the first coupler, and the second photoelectric detector can receive the signal transmitted by the third coupler and convert the signal into an electric signal to be output.
The output end of the first photoelectric detector is connected with the first mixer 10, and can transmit electric signals to the first mixer, and the output end of the second photoelectric detector is connected with the second mixer 11, and can transmit electric signals to the second mixer.
The first mixer and the second mixer are both connected with the DFB laser and can receive the linear frequency modulation signals sent by the DFB laser.
The first mixer and the second mixer are both connected with a third mixer 12, which is connected with a controller 13 and is capable of sending a difference frequency signal to the controller.
The first photoelectric detector and the second photoelectric detector are both connected with the controller and can transmit electric signals to the controller.
The controller is connected with the DFB laser and can control the DFB laser to send out set linear frequency modulation signals or optical signals.
Example 2:
The embodiment discloses an optical fiber interference device capable of eliminating associated amplitude modulation, as shown in fig. 2, the optical fiber interferometer adopts a michelson interferometer, a probe portion of the michelson interferometer is connected with 99% of light-passing ports of a first coupler through an optical circulator 14, the probe portion comprises a fourth coupler 15, the fourth coupler adopts a 50:50 1X2 coupler, two light-passing ports of the fourth coupler are connected with one ends of a third interference arm 16 and a fourth interference arm 17, the other ends of the third interference arm and the fourth interference arm are respectively connected with a first reflecting mirror 18 and a second reflecting mirror 19, a passive second optical fiber filter 20 is arranged on the fourth interference arm, and the second optical fiber filter can prevent the passing of a linear frequency modulation signal but can not prevent the passing of an interference light signal.
The optical circulator has three ports, one of which is connected to 99% of the light-transmitting ports of the first coupler, the other of which is connected to the light-transmitting ports of the fourth coupler, and the third of which is used for receiving signals reflected by the first mirror and the second mirror and is connected to the second photodetector, and other structures are the same as those of embodiment 1 and will not be described in detail herein.
Example 3
The embodiment discloses an optical fiber interference device capable of eliminating associated amplitude modulation, as shown in fig. 3, the optical fiber interferometer adopts a mach-zehnder interferometer, the probe part comprises a fifth coupler 21 and a sixth coupler 22, the fifth coupler adopts a 1X2 coupler of 40:60, the sixth coupler adopts a 1X2 coupler of 50:50, a fifth interference arm 23 and a sixth interference arm 24 are connected between the fifth coupler and the sixth coupler, a seventh coupler 25 is arranged on the sixth interference arm, the seventh coupler and the sixth coupler are very close to each other on an optical path, a 40% light-passing port of the fifth coupler is connected with the fifth interference arm, a 60% light-passing port of the seventh coupler is connected with the sixth interference arm, a 30% light-passing port of the seventh coupler is connected with a fourth photoelectric detector 26, a 1% light-passing port of the first coupler connected with the probe part is connected with a third mixer, a third photoelectric detector 27, a fourth mixer is connected with a fourth mixer, a fourth mixer is connected with a third mixer, a fourth mixer is connected with a fourth mixer, a fifth mixer is connected with a third mixer is connected with a fifth mixer, and a fifth mixer is connected with a third mixer is connected with a fifth mixer.
Example 4
The embodiment discloses a working method of an optical fiber interference device capable of eliminating associated amplitude modulation, which comprises the following steps:
in the optical fiber interference device of embodiment 1, the laser, the first coupler, and the first photodetector form a first optical path, and the laser, the probe section, and the second photodetector form a second optical path.
Under the control of a controller, the DFB laser emits a ranging modulation signal, the ranging modulation signal is a set chirp signal, a person skilled in the art can select a proper chirp signal according to practical situations, the chirp signal passes through a first optical path (a first coupler-a first photoelectric detector), the first photoelectric detector outputs to the first mixer, the chirp signal is directly transmitted to the first mixer at the same time, the first mixer mixes the signals of the received laser and the first optical path to form a first difference frequency signal and outputs to a third mixer, the first optical fiber filter can prevent the passing of the chirp signal, the chirp signal passes through a second optical path (a first coupler-a second coupler-a first interference arm-a third coupler-a second photoelectric detector), the second photoelectric detector outputs to the second mixer, the chirp signal is directly transmitted to the second mixer, the second mixer mixes the signals of the received laser and the second optical path to form a second difference frequency signal and outputs to the third mixer, the first difference frequency signal and the second difference frequency signal arrive at the first optical path, the first difference frequency signal and the second optical path reach the third optical path, the difference frequency signal is calculated by the first optical fiber filter and the second optical detector, the difference frequency difference signal is calculated by the first difference frequency difference signal and the second optical detector, the difference signal is calculated by the first difference frequency difference signal and the second difference detector
The specific calculation method comprises the following steps:
Wherein C n is the transmission speed of light in the optical fiber; v (t) is the optical frequency.
The DFB laser emits an optical signal used for generating interference under the control of the controller, the optical signal is output by the first photoelectric detector after passing through the first optical path and is transmitted to the controller, the optical signal is transmitted in the first interference arm and the second interference arm of the probe part, the optical signal is transmitted to the controller by the third coupler after interference is generated and is transmitted to the controller through the second photoelectric detector, the controller brings the obtained phase difference into the optical signal output by the first photoelectric detector, and then the signal data output by the second photoelectric detector is divided by the signal data which is output by the first photoelectric detector and is brought into the phase difference, so that interference optical signal data is obtained.
The working method of the optical fiber interference device of embodiment 2 is as follows:
The first light path is: the laser, the first coupler, the first photoelectric detector and the second optical path are as follows: the DFB laser emits a linear frequency modulation signal, the linear frequency modulation signal is transmitted to a first mixer through a first coupler and a first photoelectric detector, meanwhile the linear frequency modulation signal is directly transmitted to the first mixer, the first mixer carries out frequency mixing to obtain a first difference frequency signal, a second optical fiber filter can prevent the linear frequency modulation signal from passing, therefore, the linear frequency modulation signal is transmitted to a second mixer through the optical circulator, a fourth coupler, a third interference arm, a first reflector, the optical circulator and a second photoelectric detector through the second photoelectric detector, the linear frequency modulation signal is directly transmitted to the second mixer, the second mixer carries out frequency mixing to form a second difference frequency signal, the first difference frequency signal and the second difference frequency signal are transmitted to a third mixer, the third mixer carries out frequency mixing on the first difference frequency signal and the second difference frequency signal, the obtained signal emitted by the DFB laser reaches the first photoelectric detector and the second photoelectric detector, the delta difference frequency signal is controlled by the optical path difference frequency controller, and the difference frequency controller is controlled by the second photoelectric detector, and the difference frequency controller is controlled by the first difference frequency controller and the second photoelectric detector, and the difference frequency controller is controlled by the second difference frequency controller
The specific calculation method comprises the following steps:
Wherein C n is the transmission speed of light in the optical fiber; v (t) is the optical frequency.
The DFB laser emits an optical signal used for generating interference under the control of the controller, the optical signal is transmitted to the controller after passing through the first coupler and the first photoelectric detector, the other path of optical signal output by the first coupler enters the third interference arm and the fourth interference arm through the optical circulator, interference is generated after being reflected by the first reflecting mirror and the second reflecting mirror, the interfered signal is transmitted to the second photoelectric detector through the optical circulator, the second photoelectric detector transmits the interfered optical signal to the controller, the controller brings the obtained phase difference into the optical signal output by the first photoelectric detector, and then the signal data output by the second photoelectric detector is divided by the signal data output by the first photoelectric detector after the phase difference is brought into, so that the interference optical signal data is obtained.
The working method of the optical fiber interference device of embodiment 3 is as follows:
the first light path is: the laser device, the first coupler and the third photoelectric detector, and the second light path is as follows: the second light path I and the second light path II form, and the second light path I is: the second light path II is a laser, a first coupler, a probe part and a fifth photoelectric detector, the DFB laser emits a linear frequency modulation signal, the linear frequency modulation signal is transmitted to a first mixer through the first coupler and a third photoelectric detector, the linear frequency modulation signal is directly transmitted to the first mixer at the same time, the first mixer carries out mixing to obtain a first difference frequency signal, the other linear frequency modulation signal output by the first coupler is input to the fourth photoelectric detector through the fifth coupler and the seventh coupler, the fourth photoelectric detector transmits the signal to a second mixer, the second mixer receives the linear frequency modulation signal emitted by the DFB laser, the second mixer carries out mixing to form a second difference frequency signal, the first difference frequency signal and the second difference frequency signal are transmitted to a third mixer to carry out mixing, the signal emitted by the DFB laser reaches a difference signal delta L at the third photoelectric detector and the fourth photoelectric detector, the difference frequency signal is transmitted to the fourth photoelectric detector, the fourth photoelectric detector is controlled to carry out operation on the difference frequency signal, and the fourth difference frequency signal is calculated to obtain the fourth difference frequency signal, and the fourth difference frequency signal is calculated by the fourth photoelectric detector
The specific calculation method comprises the following steps:
Wherein C n is the transmission speed of light in the optical fiber; v (t) is the optical frequency.
In this embodiment, since the optical paths of the seventh coupler and the sixth coupler are close, the optical path of the signal emitted from the laser to the fourth photodetector and the optical path to the fifth photodetector are approximately equal.
The DFB laser emits optical signals for interference, one path of the optical signals is transmitted to the controller through the first coupler and the third photoelectric detector, the other path of the optical signals are transmitted to the controller through the fifth photoelectric detector after interference is generated by the other path of the probe, the controller brings the obtained phase difference into the optical signals output by the third photoelectric detector, and then the signal data output by the fifth photoelectric detector is divided by the signal data which are output by the third photoelectric detector and are brought into the phase difference, so that interference optical signal data are obtained.
When two paths of detection signals are adopted to compensate the associated amplitude modulation effect, when the optical path problem of the two paths of detection signals is not considered, the expression of the light intensity I 1 (t) at the first photoelectric detector is
I 0 is the DC component of the light source; ΔI 0 is the variation amplitude of the light intensity along with the current; omega c is the angular velocity of the wavelength; time t; Is the initial phase of the light source.
When the optical path problem of the two detection signals is not considered, it is assumed that I 1 (t) is the emergent light I 0 (t) of the light source, and the expression of the light intensity I 2 (t) at the second photodetector is
A and B are fixed constants; v 0 is the DC optical frequency; deltav is the variation amplitude of the optical frequency; omega c is the angular velocity of the wavelength; Δl is the optical path difference of the two interference arms; c n is the transmission speed of light in the fiber.
As can be seen from equations 1-1 and 1-2, the conventional method for compensating the associated amplitude modulation effect is mainly based on dividing two paths of detection signals to overcome the influence of the change of the direct current light intensity I 0 (t) and inhibit the demodulation distortion of the signals.
However, when the distance between the two detection signals in the optical path is tens or hundreds of kilometers, the light intensity I 1 (t) detected at the first photodetector cannot be directly used as the outgoing light I 0 (t) of the light source, because the light intensity signal detected at the second photodetector has a phase difference with the outgoing light I 0 (t) of the light source, and the direct division can cause signal demodulation distortion.
When considering the optical path problem of the two detection signals, the phase difference between the upper measurement points must be considered. The light intensity I 1 (t) at the first photodetector is expressed as
I 0 is the DC component of the light source; ΔI 0 is the variation amplitude of the light intensity along with the current; omega c is the angular velocity of the wavelength; t is time; Is the initial phase of the light source; /(I) An increased amount of phase change for the light source to emit light to reach the first photodetector.
Wherein the method comprises the steps of
L 1 is the optical path from the light source to the first photodetector; c n is the transmission speed of light in the fiber; v (t) is the optical frequency.
When considering the optical path problem of the two detection signals. The light intensity I 2 (t) at the second photodetector is expressed as
A and B are fixed constants; i 0 (t) is the light intensity expression of the emergent light of the light source reaching the second photoelectric detector; omega c is the angular velocity of the wavelength; v 0 is the DC optical frequency; deltav is the variation amplitude of the optical frequency; Δl is the optical path difference of the two interference arms; c n is the transmission speed of light in the fiber.
Wherein the method comprises the steps of
I 0 is the DC component of the light source; ΔI 0 is the variation amplitude of the light intensity along with the current; omega c is the angular velocity of the wavelength; t is time; Is the initial phase of the light source; /(I) An increased amount of phase change for the light source to emit light to reach the second photodetector.
Wherein the method comprises the steps of
L 2 is the optical path from the light source to the second photodetector; c n is the transmission speed of light in the fiber; v (t) is the optical frequency.
As described above, if the optical path problem of the two paths of detection signals is considered, the light intensity I 1 (t) at the first photodetector is equal to the light intensity I 0 (t) at the first photodetector when the outgoing light of the light source reaches the first photodetector, according to formulas 1-3 and 1-6; let the phase difference of the light from the light source reaching the first and second photodetectors be
Is available in the form of
I 0 is the DC component of the light source; ΔI 0 is the variation amplitude of the light intensity along with the current; omega c is the angular velocity of the wavelength; t is time; Is the initial phase of the light source; /(I) Increasing the phase variation for the light source emergent light to reach the first photoelectric detector; /(I)Is the phase difference of the light at the first and second photodetectors that is the outgoing light of the light source.
That is, only the phase difference of the light from the light source reaching the first and second photodetectors is measuredThe effect of light intensity change in the accompanying amplitude modulation effect can be overcome by the division of the two paths of detection signals, and the purpose of signal demodulation is achieved.
Therefore, the device and the method of the embodiment solve the problem of signal distortion inhibition of a high-frequency direct current light intensity part caused by the phase difference of the direct current light intensity due to the difference of signal acquisition positions, and solve the problem of distortion elimination of associated amplitude modulation generated when the optical fiber interferometer is practically applied in a long distance.
While the foregoing description of the embodiments of the present invention has been presented in conjunction with the drawings, it should be understood that it is not intended to limit the scope of the invention, but rather, it is intended to cover all modifications or variations within the scope of the invention as defined by the claims of the present invention.
Claims (8)
1. The working method of the optical fiber interference device capable of eliminating the associated amplitude modulation is characterized in that the optical fiber interference device capable of eliminating the associated amplitude modulation comprises an optical fiber interferometer, the optical fiber interferometer comprises a laser and a first coupler, the laser can transmit signals to the first coupler, the first coupler is connected with a probe part, an output end of the probe part and the first coupler are respectively connected with a first mixer and a second mixer through a photoelectric detector, the first mixer and the second mixer are connected with a third mixer and the laser, the laser can output signals to the first mixer and the second mixer, the first mixer and the second mixer can output signals to the third mixer, the third mixer is connected with a controller, and the photoelectric detector is also connected with the controller and can convert optical signals output by the first coupler and the probe part into electric signals to be transmitted to the controller;
the working method comprises the following steps:
the laser, the first coupler, the probe part and the photoelectric detection part form a first light path, and the laser, the first coupler, the probe part and the photoelectric detection part form a second light path;
The laser sends out a ranging modulation signal, the ranging modulation signal enters a first mixer through a first optical path, the first mixer receives and mixes signals of the laser and the first optical path to obtain a first difference frequency signal, the second mixer receives and mixes signals of the laser and signals of a second optical path to obtain a second difference frequency signal, the first difference frequency signal and the second difference frequency signal are transmitted to a third mixer to mix, and the difference frequency signal of the optical path difference between the first optical path and the second optical path is obtained And transmitting the signals to a controller, wherein the controller obtains the phase difference when signals of the two light paths reach the photoelectric detection part according to the difference frequency signals of the optical path difference；
The laser emits light signals, the controller receives the output light signals of the first light path and the second light path through the photoelectric detection part, and the obtained phase difference is obtainedThe optical signal data obtained by detection of the photoelectric detection element of the second optical path is divided by the optical signal data with the phase difference output by the photoelectric detection element of the first optical path in the optical signals output by the photoelectric detection element of the first optical path, so that the data of interference optical signals are obtained;
the phase difference calculating method comprises the following steps:
Wherein, Is the transmission speed of light in the fiber; v (t) is the optical frequency.
2. The method of claim 1, wherein the controller is coupled to the laser and is configured to control the laser to emit the set signal.
3. The method of claim 1, wherein the probe portion includes a second coupler and a third coupler, the second coupler and the third coupler are connected to two ends of the first interference arm and the second interference arm, the second interference arm is provided with a filter, and the third coupler is connected to the photodetector.
4. The method of claim 1, wherein the probe portion is connected to a first coupler through an optical circulator, the optical circulator is connected to a second photodetector, the probe portion includes a fourth coupler connected to the optical circulator, the fourth coupler is connected to one ends of a third interference arm and a fourth interference arm, the other ends of the third interference arm and the fourth interference arm are respectively connected to a first mirror and a second mirror, a filter is disposed on the fourth interference arm, the first mirror and the second mirror are capable of transmitting optical signals to the optical circulator in a reflection manner, and the optical circulator is connected to the photodetector and is capable of transmitting reflected optical signals to the photodetector.
5. A method of operating an optical fiber interference device capable of canceling concomitant amplitude modulation as claimed in claim 3 or 4, wherein: the photoelectric detection part comprises a first photoelectric detector and a second photoelectric detector, the input end of the first photoelectric detector is connected with the first coupler, the output end of the first photoelectric detector is connected with the first mixer and the controller, the input end of the second photoelectric detector is connected with the output end of the probe part, and the output end of the second photoelectric detector is connected with the second mixer and the controller.
6. A method of operating an optical fiber interference device capable of canceling concomitant amplitude modulation as claimed in claim 3 or 4, wherein: the filter element adopts a passive optical fiber filter or an active optical switch.
7. A method of operating an optical fiber interference device capable of canceling concomitant amplitude modulation as claimed in claim 1, wherein: the probe part comprises a fifth coupler and a sixth coupler, a fifth interference arm and a sixth interference arm are connected between the fifth coupler and the sixth coupler, and a seventh coupler is arranged on the sixth interference arm.
8. The method of claim 7, wherein the photodetector comprises a third photodetector, a fourth photodetector and a fifth photodetector, the third photodetector has an input connected to the first coupler, an output connected to the laser and the first mixer, the fourth photodetector has an input connected to the seventh coupler, an output connected to the second mixer, and the fifth photodetector has an input connected to the sixth coupler, and an output connected to the controller.
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