CN211926897U - Feed-forward structure for improving noise of light source and optical fiber vibration measuring device - Google Patents
Feed-forward structure for improving noise of light source and optical fiber vibration measuring device Download PDFInfo
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Abstract
The invention provides a light source noise improvement feedforward structure and an optical fiber vibration measuring device, and relates to the field of optical fiber distributed vibration measurement, wherein in a feedforward loop of the light source noise improvement feedforward structure, two mutually orthogonal interference optical signals are obtained based on an optical fiber interferometer and a 90-degree optical mixer, are respectively output to a photoelectric balance detector 1 and a photoelectric balance detector 2, are converted into two interference electrical signals, and are output to a tracker; the method uses light source noise to improve a feedforward structure, performs phase noise suppression on continuous light output by a laser, and adds the phase noise suppression to the classical light
In the measuring device, the phase noise of the laser is reduced, and the measuring precision of the external vibration signal is further improved.
Description
Technical Field
The disclosure relates to the field of optical fiber distributed vibration measurement, in particular to a feed-forward structure for improving light source noise and an optical fiber vibration measurement device.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
The optical time domain reflection measurement technology is an essential technology in optical cable construction, maintenance and monitoring, and is based on the principle of backward scattering and Fresnel reverse of light, and utilizes the backward scattering light wave generated when pulse light wave propagates in an optical fiber to obtain the information of energy (amplitude) attenuation, so that the optical time domain reflection measurement technology can be used for measuring the optical fiber attenuation, joint loss, optical fiber fault point positioning, knowing the loss distribution condition of the optical fiber along the length and the like.
With the continuous improvement of measurement techniques, phase-sensitive optical time-domain reflectometry, for example, has emerged
The technology,
Vibration measurement technique and based on quadratic differenceIs/are as follows
A method of measurement;
the inventors have found that for the difference based on two
According to the measuring method, when the measured environment vibrates, due to the influence of a vibration event, the sensing optical fibers behind the vibration point carry vibration information, and the sensing optical fibers in front of the vibration point do not carry vibration information. Thus, the distance D can be selectedABThe point A and the point B preliminarily eliminate the adverse effect on the measurement caused by the phase noise of the laser through phase difference, wherein the point A carries vibration information after the vibration point, and the point B does not carry vibration information before the vibration point. Further, the distance between the vibration points is selected to be DCDThe phase difference is made between the points C and D to obtain C, D phase change information between the two points. By calculating the distance DABAnd DCDThe proportional relation can eliminate the performance influence of the laser phase noise on the sensing system, compensate the measurement phase drift caused by the frequency drift in real time and improve the measurement precision of the external vibration signal, but the method is a digital signal processing method, does not reduce the laser phase noise at all and is difficult to further improve the measurement precision of the external vibration signal.
SUMMERY OF THE UTILITY MODEL
The disclosure aims to provide a feed-forward structure for improving light source noise and an optical fiber vibration measurement device, aiming at the defects in the prior art, and the feed-forward structure is added in the traditional phase sensitive optical time domain reflection measurement device, so that the phase noise of emergent laser is reduced, and the measurement precision of an external vibration signal is further improved.
The first purpose of this disclosure is to provide a light source noise improves feedforward structure, adopts the following technical scheme:
the system comprises a laser, a first coupler, a single-sideband modulator, an interferometer, a photoelectric balance detector, a tracker, a preamplifier and a voltage-controlled oscillator, wherein the interferometer, the photoelectric balance detector, the tracker, the preamplifier and the voltage-controlled oscillator are sequentially connected in an electric manner; the laser and the first coupler, the first coupler and the interferometer, the first coupler and the single-sideband modulator, and the voltage-controlled oscillator and the single-sideband modulator are connected through optical fibers.
Furthermore, the input end of the first coupler is connected with the laser, and the two output ends of the first coupler are respectively connected with the single-sideband modulator and the interferometer through optical fibers.
Further, a first delay optical fiber is connected in series between the first coupler and the single-sideband modulator.
Furthermore, the interferometer comprises a second coupler and an optical mixer, and the second coupler is connected with the optical mixer through two paths of optical fibers.
Furthermore, the photoelectric balance detector comprises a first photoelectric balance detector and a second photoelectric balance detector which are respectively connected with the optical mixer and the tracker.
Furthermore, the input end of the second coupler is connected with the output end of the first coupler, one output end of the second coupler is sequentially connected with the optical mixer, the first photoelectric balance detector, the tracker and the preamplifier, and the other output end of the second coupler is sequentially connected with the optical mixer, the second photoelectric balance detector, the tracker and the preamplifier.
Furthermore, a second delay optical fiber is connected in series to one optical fiber between the second coupler and the optical mixer.
Further, the optical mixer is a 90-degree optical mixer, and the second coupler is configured to input two orthogonal optical signals to the optical mixer.
Furthermore, two input ends of the single-sideband modulator are respectively connected with the first coupler and the voltage-controlled oscillator and are used for carrying out frequency synthesis to output continuous light with improved fragrance and noise of the light source.
The second purpose of the present disclosure is to provide an optical fiber vibration measurement apparatus, which adopts the following technical solutions:
comprises that
Measuring deviceLight source noise improving feedforward architecture, single sideband modulator and method
The measuring device is connected.
Compared with the prior art, the utility model has the advantages and positive effects that:
(1) the method uses light source noise to improve a feedforward structure, performs phase noise suppression on continuous light output by a laser, and adds the phase noise suppression to the classical light
In the measuring device, the phase noise of the laser is reduced, and the measuring precision of an external vibration signal is further improved;
(2) in a feedforward loop of a feedforward structure for improving the noise of a light source, two mutually orthogonal interference optical signals are obtained based on an optical fiber interferometer and a 90-degree optical mixer and are respectively output to a photoelectric balance detector 1 and a photoelectric balance detector 2, converted into two interference electrical signals and output to a tracker. The method avoids the frequency drift problem existing when single-path interference optical signals are adopted to carry out first-order differential light source phase noise estimation, and improves the measurement precision of the first-order differential light source phase noise, thereby being beneficial to inhibiting the light source phase noise and improving the measurement precision of external vibration signals.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and are not to limit the disclosure.
Fig. 1 is a schematic structural and flow diagram of optical fiber vibration measurement in embodiments 1, 2, and 3 of the present disclosure;
fig. 2 is a structural diagram of a tracker in embodiments 1, 2, and 3 of the present disclosure.
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 disclosure 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 disclosure. As used herein, the singular forms "a", "an", and/or "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;
for convenience of description, the words "up", "down", "left" and "right" in this disclosure, if any, merely indicate that the directions of movement are consistent with those of the figures themselves, and are not limiting in 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 present disclosure.
As described in the background, the prior art is twice differenced
The measuring method is a digital signal processing method, the phase noise of the laser is not reduced fundamentally, and the measuring precision of the external vibration signal is difficult to further improve; in order to solve the problems, the present disclosure provides a feed-forward structure for improving noise of a light source and an optical fiber vibration measuring apparatus.
Light source noise: the linewidth of the laser cannot be infinitely narrow and there is always some phase noise (otherwise known as "frequency drift"). When pulsed light is transmitted in an optical fiber, the intensity of a backward Rayleigh scattering signal is affected by phase noise of the detected light to generate jitter, so that the signal-to-noise ratio of a measurement signal is reduced, and positioning and measurement errors of a measured vibration signal even fail.
To pair
System-wise, phase noise of laserThe sound can reduce the measurement accuracy of the system and reduce the spatial resolution of the system. Therefore, it is important to improve the phase noise of the optical wave. On one hand, the stability of the optical wave frequency can be improved and the phase noise can be reduced by improving the laser material, keeping the environmental temperature and humidity and the atmospheric pressure stable and the like; on the other hand, the adverse effects of the optical wave phase noise on the vibration measurement precision and the space positioning can be inhibited by designing a new optical path structure and a new data processing method.
For the former, on the basis of the existing laser manufacturing process and constant temperature, humidity and pressure treatment technology, the technology is not a technical method which is easy to realize in a short period; for the latter, a more general method is to use a quadratic difference method, which is an improved method of pure digital signal processing.
Based on quadratic difference
The detailed working principle of the measuring method is as follows:
in the classic
On the basis of the system structure, continuous light emitted by a narrow linewidth laser is divided into two paths through a coupler with a specific power ratio, wherein one path of continuous light is converted into pulse light with a specific width and period through an acousto-Optic Modulator (AOM) with a frequency shift function, the pulse light enters a port of a circulator 1 after being subjected to power compensation through an Optical Amplifier (generally, an Erbium Doped Fiber Amplifier (EDFA)), and then enters a sensing Optical Fiber through the port of the circulator 3 to obtain vibration measurement information along the Optical Fiber, and backward scattered light which carries environmental vibration information and is generated in the sensing Optical Fiber passes through the port of the circulator 3 again and then exits from the port of the circulator 2.
The other path of continuous light which is branched after the continuous light emitted by the light source passes through the coupler with the specific power ratio is used as local reference light. The local reference light and the backward Rayleigh scattered light emitted from the port 2 of the circulator generate coherent signals through a coupler with the ratio of 50:50, the coherent signals are converted into electric signals through a photoelectric detector and enter a data acquisition card, digital signals are obtained, data processing is carried out on the electric signals, and environmental vibration information along the optical fiber is obtained.
However, based on quadratic differences
The measuring method is a digital signal processing method, does not reduce the phase noise of the laser at all, and does not consider the feasible scheme of improving and suppressing the phase noise of the measurement by the optical path structure.
Example 1
In an exemplary embodiment of the present disclosure, a light source noise improvement feed-forward architecture is presented, as shown in fig. 1-2.
The light source noise improving feedforward configuration includes: coupler 1, delay fiber 1, feed forward loop, single sideband modulator.
The laser emits narrow-linewidth continuous light, the narrow-linewidth continuous light is divided into two paths through a 50:50 coupler 1, the path 1 directly enters a single-side band modulator through a delay optical fiber 1, and the path 2 enters the single-side band modulator through a feedforward loop. The delay optical fiber 1 realizes propagation delay control of the 1 st path of continuous light, and ensures that two paths of continuous light from the coupler 1 to the single side band modulator have the same delay time.
The feed forward loop comprises: the device comprises a coupler 2, a delay optical fiber 2, a 90-degree optical mixer, a photoelectric balance detector 1, a photoelectric balance detector 2, a tracker, a preamplifier and a voltage-controlled oscillator.
The 2 nd path of continuous light output by the coupler 1 is divided into two paths through the coupler 2 with the ratio of 50:50, wherein one path of continuous light directly enters the 90-degree optical mixer, and the other path of continuous light enters the 90-degree optical mixer through the delay optical fiber 2. The coupler 2, the transmission fiber without the delay fiber, the transmission fiber with the delay fiber 2, and the 90-degree optical mixer constitute a classical mach-zehnder fiber interferometer, the difference in the length of the interference arms being determined by the delay fiber 2. Based on the Mach-Zehnder optical fiber interferometer, the 90-degree optical mixer obtains two mutually orthogonal interference optical signals, respectively outputs the two interference optical signals to the photoelectric balance detector 1 and the photoelectric balance detector 2, converts the two interference optical signals into two interference electric signals and outputs the two interference electric signals to the tracker. The tracker obtains the light source phase noise of the primary difference, and transmits the light source phase noise to the preamplifier, and the time difference of the primary difference is determined by the delay optical fiber 2. The preamplifier amplifies the light source phase noise of the primary difference, drives the voltage-controlled oscillator, generates continuous optical signals and outputs the continuous optical signals to the single-sideband modulator.
The single sideband modulator receives the continuous light passing through the delay optical fiber 1 and the continuous light of the feedforward loop for frequency synthesis, and the continuous light with the output light source phase noise improved enters the coupler 3.
Based on the Mach-Zehnder optical fiber interferometer, the 90-degree optical mixer obtains two mutually orthogonal interference optical signals, respectively outputs the two interference optical signals to the photoelectric balance detector 1 and the photoelectric balance detector 2, converts the two interference optical signals into two interference electric signals and outputs the two interference electric signals to the tracker. The method avoids the frequency drift problem existing when single-path interference optical signals are adopted to carry out first-order differential light source phase noise estimation, and improves the measurement precision of the first-order differential light source phase noise, thereby being beneficial to inhibiting the light source phase noise and improving the measurement precision of external vibration signals.
The 90-degree optical mixer outputs two paths of orthogonal (I path and Q path) interference electric signals to the tracker.
Among them, for the selection of each element, a set of examples is given in the present embodiment:
a laser: a Distributed Feedback (DFB) laser (model: DFB-1550-DM-4);
the coupler 1: a standard single mode fiber coupler with a splitting ratio of 50: 50;
the coupler 2: a standard single mode fiber coupler with a splitting ratio of 50: 50;
delay optical fiber 1: the method is manufactured by using a Corning SMF-28 single-mode fiber;
delay fiber 2: the method is manufactured by using a Corning SMF-28 single-mode fiber;
90-degree optical mixer: a single-stage polarization 90-degree optical mixer (model COH 24X);
photoelectric balance detector 1: a photoelectric balance detector (model TL-BPD 100);
photoelectric balance detector 2: a photoelectric balance detector (model TL-BPD 100);
a preamplifier: constructed using operational amplifier ADA 4895;
a voltage-controlled oscillator: a voltage controlled oscillator (model ADF4372) integrated with a phase locked loop;
single sideband modulator: single sideband modulator (model IRM5 XMS-1).
For the tracker, in this embodiment, it includes: averager 1, averager 2, multiplier 1, inverter, multiplier 2 and adder. The I path interference electric signal passes through the averager 1, calculates the signal average value in the time T and transmits the signal average value to the multiplier 1. The multiplier 1 multiplies the signal average value output from the averager 1 by the Q-path signal and outputs the result to the adder. The Q path interference electric signal passes through the averager 2 to obtain the signal average value in the time T, and the Q path interference electric signal is inverted by the phase inverter and then transmitted to the multiplier 2. The multiplier 2 multiplies the average value of the signal output from the averager 2 by the I-path signal and outputs the result to the adder. The adder adds the two paths of input signals to obtain primary differential light source phase noise and transmits the primary differential light source phase noise to the preamplifier;
for the structure of the elements within the tracker:
averager 1: an operational amplifier AD8065 is used for building an integrating circuit;
an averager 2: an operational amplifier AD8065 is used for building an integrating circuit;
a multiplier 1: building based on an analog multiplier chip AD 835;
and a multiplier 2: building based on an analog multiplier chip AD 835;
an inverter: an inverting unity gain circuit is built by using an operational amplifier AD 8065;
an adder: the adder circuit was built using 3 operational amplifiers AD 8065.
Example 2
In another exemplary embodiment of the present disclosure, as shown in fig. 1 and 2, an optical fiber vibration measuring device is provided.
The method mainly comprises the following steps: a laser, a light source noise improvement feed forward structure as in example 1, a coupler 3, an acousto-optic modulator, an erbium doped fiber amplifier, a circulator, a sensing fiber, a coupler 4, a photodetector, a data acquisition card, a signal generator and a processor.
The narrow linewidth continuous light is emitted by the laser, after the feedforward structure is improved by light source noise, the narrow linewidth continuous light enters the coupler 3 with a specific power ratio and is divided into two paths, one path of continuous light is subjected to acousto-optic modulation with a frequency shift function and is converted into pulse light with a specific width and a specific period, the pulse light enters the port 1 of the circulator after being subjected to power compensation by the optical amplifier, the pulse light is emitted through the port 3 of the circulator and enters the sensing optical fiber, vibration measurement information along the optical fiber is obtained, backward Rayleigh scattering light which carries environmental vibration information and is generated in the sensing optical fiber passes through the port 3 of the circulator again and is emitted from the port 2 of the circulator.
The other continuous light which is divided after the continuous light emitted by the light source passes through the coupler 3 with the specific power ratio is used as the local reference light. The local reference light and the backward Rayleigh scattered light emitted from the port of the circulator 2 generate coherent signals through the coupler 4 in a ratio of 50:50, the coherent signals are converted into electric signals through the photoelectric detector and enter the data acquisition card, the digital signals are obtained and are subjected to data processing in the processor, and the environmental vibration information along the optical fiber is obtained.
The method uses light source noise to improve a feedforward structure, performs phase noise suppression on continuous light output by a laser, and adds the phase noise suppression to the classical light
In the measuring device, the phase noise of the laser is reduced, and the measuring precision of the external vibration signal is further improved.
In the present embodiment, a set of examples of the selection of the elements is given:
the coupler 3: a standard single-mode fiber coupler with adjustable splitting ratio;
an acousto-optic modulator: an acousto-optic modulator (model M080-1 x-GHx);
an optical amplifier: an erbium doped fiber amplifier (model AMP-PM 15M);
a circulator: a 3-port fiber optic circulator (model MCCIR-1550);
the coupler 4: a standard single mode fiber coupler with a splitting ratio of 50: 50;
a photoelectric detector: FC/APC PIN photodetectors;
a data acquisition card: high speed data acquisition card (model PCI 9812);
a processor: a core board based on EP4CE30F FPGA;
a signal generator: signal generator module based on AD9559 chip.
It is understood that the above-mentioned selection can be adjusted according to actual requirements.
Example 3
In another exemplary embodiment of the present disclosure, as shown in fig. 1-2, a method of operating an optical fiber vibration measurement device is provided.
wherein A represents the amplitude of light waves, v0Representing the frequency of the optical wave, with a constant 193.5THz (corresponding to a wavelength of 1550 nm) or 229.0THz (corresponding to a wavelength of 1310 nm), θ (t) representing the phase noise of the light source, and t representing time.
And 2, dividing the continuous light of the laser into two paths, wherein 1 path obtains two paths (an I path and a Q path) of orthogonal interference signals by using a classical Mach-Zehnder interferometer:
I(t)＝B cos(2πν0τ+Δθ(t)) (2)
Q(t)＝B sin(2πν0τ+Δθ(t)) (3)
Δθ(t)＝θ(t)-θ(t-τ) (4)
where B represents the interference signal amplitude, Δ θ (t) represents the first-order differential light source phase noise, and τ represents the time delay caused by the mach-zehnder interferometer interferometric arm length. And τ is selected to be short in time so that Δ θ (t) satisfies:
Δθ(t)＜＜1 (5)
and 3, multiplying the I path interference signal by the Q path signal after time averaging, multiplying the Q path interference signal by the I path signal after time averaging and negation, and obtaining:
where T represents the length of time for averaging. Since laser phase noise is a bounded zero-mean random process, taking the time average to be zero, we get:
and 4, adding the two paths of signals obtained in the previous step to obtain:
the amplitude normalization processing is performed on the above formula, and since τ is selected to be shorter time, according to formula (5), the estimated value of the first-order difference light source phase noise can be obtained:
and 5, amplifying the extracted first-order differential light source phase noise, and driving a voltage-controlled oscillator to output an oscillation signal:
wherein, v1Indicating the natural frequency of oscillation, k, of the voltage-controlled oscillatorVCOIndicating the sensitivity, k, of the voltage-controlled oscillatorAMPShowing the magnification.
And 6, enabling continuous light output by the voltage-controlled oscillator to enter a single-side band modulator, enabling the other path of the continuous light of the laser to enter the single-side band modulator through a delay optical fiber, and ensuring that the time delay of the two paths of continuous light is equal through the delay optical fiber. The single-sideband modulator modulates the continuous light of the laser by using the oscillation signal output by the voltage-controlled oscillator to obtain:
by adjusting the parameter kVCOAnd kAMPSo that 2 π kVCOkAMPτ is 1, the light source phase noise θ (t) can be suppressed significantly.
And 7, after passing through a feed-forward structure of light source noise suppression, the light source continuous light enters a coupler 3 with a specific power ratio and is divided into two paths, wherein one path of continuous light is subjected to acousto-optic modulation with a frequency shift function and is converted into pulse light with a specific width and a specific period, the pulse light enters a port of a circulator 1 after being subjected to power compensation through an optical amplifier, and then the pulse light is emitted through a port 3 of the circulator and enters a sensing optical fiber to obtain vibration measurement information along the optical fiber, and backward Rayleigh scattering light which carries environmental vibration information and is generated in the sensing optical fiber passes through the port 3 of the circulator again and is emitted from a port 2 of the circulator.
The other continuous light which is divided after the continuous light emitted by the light source passes through the coupler 3 with the specific power ratio is used as the local reference light. The local reference light and the backward Rayleigh scattered light emitted from the port of the circulator 2 generate coherent signals through the coupler 4 in a ratio of 50:50, the coherent signals are converted into electric signals through the photoelectric detector and enter the data acquisition card, the digital signals are obtained and are subjected to data processing in the processor, and the environmental vibration information along the optical fiber is obtained.
When the vibration of the detected environment occurs, the sensing optical fibers behind the vibration point carry vibration information due to the influence of the vibration event, and the sensing optical fibers in front of the vibration point do not carry vibration information;
thus, the distance D can be selectedABThe point A and the point B preliminarily eliminate the adverse effect on the measurement caused by the phase noise of the laser through phase difference, wherein the point A carries vibration information after the vibration point, and the point B does not carry vibration information before the vibration point.
Further, the distance between the vibration points is selected to beDCDThe phase difference is made between the points C and D to obtain C, D phase change information between the two points. By calculating the distance DABAnd DCDThe proportional relation of the frequency offset and the phase offset can further eliminate the influence of residual laser phase noise on the performance of a sensing system, compensate the measurement phase drift caused by the frequency drift in real time and further improve the measurement precision of external vibration signals.
Wherein,
indicating the external vibration that needs to be measured,
the phase difference between the points a and B is shown,
the phase difference between the points C and D is shown.
It is to be noted that, if the distance is DCDThe point C and the point D are behind the vibration point, the phase information of the point C and the point D is added with the phase information caused by the external vibration detected by the sensing optical fiber, and the same signals as the point C and the point D before the vibration point can be obtained after the phase difference is made
Therefore, the C point and the D point can compensate the measurement phase drift caused by the residual phase noise of the laser in real time whether the C point and the D point are selected to be before or after the vibration point.
The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure, and various modifications and changes may be made to the present disclosure by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.
Claims (10)
1. A feedforward structure for improving light source noise is characterized by comprising a laser, a first coupler, a single-sideband modulator, an interferometer, a photoelectric balance detector, a tracker, a preamplifier and a voltage-controlled oscillator which are electrically connected in sequence; the laser and the first coupler, the first coupler and the interferometer, the first coupler and the single-sideband modulator, and the voltage-controlled oscillator and the single-sideband modulator are connected through optical fibers.
2. The optical source noise-improving feedforward arrangement of claim 1, wherein the input end of the first coupler is connected to a laser, and the two output ends of the first coupler are connected to the single-sideband modulator and the interferometer through optical fibers, respectively.
3. The optical source noise-improving feedforward arrangement of claim 2, wherein a first delay fiber is connected in series between the first coupler and the single-sideband modulator.
4. The optical source noise-improving feedforward arrangement of claim 1, wherein the interferometer includes a second coupler and an optical mixer, the second coupler being connected to the optical mixer by a two-way optical fiber.
5. The optical source noise-improving feedforward architecture of claim 4, wherein the photo-balance detector includes a first photo-balance detector and a second photo-balance detector, each connected to the optical mixer and the tracker, respectively.
6. The optical source noise-improving feedforward architecture of claim 5, wherein the input of the second coupler is connected to the output of the first coupler, one output of the second coupler is connected to the optical mixer, the first photo-balance detector, the tracker, and the preamplifier in sequence, and the other output is connected to the optical mixer, the second photo-balance detector, the tracker, and the preamplifier in sequence.
7. The feed-forward structure for improving noise of optical source according to claim 6, wherein a second delay fiber is connected in series to a path of optical fiber between the second coupler and the optical mixer.
8. The feed-forward architecture for improving noise in an optical source of claim 7, wherein the optical mixer is a 90-degree optical mixer, and the second coupler is configured to input two orthogonal optical signals to the optical mixer.
9. The light source noise-improving feedforward architecture of claim 1, wherein the two inputs of the single-sideband modulator are connected to the first coupler and the voltage controlled oscillator, respectively, for frequency synthesizing the output light source fragrance noise-improved continuous light.
10. An optical fiber vibration measuring device is characterized by comprising
Measuring device and light source noise-improving feedforward arrangement as claimed in any of claims 1 to 9, single-sideband modulator and
the measuring device is connected.
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| CN115277345A (en) * | 2022-07-20 | 2022-11-01 | 公诚管理咨询有限公司 | Carrier phase recovery method in coherent optical communication system based on COSTAS |
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