CN107860405B - A kind of spectrum demodulation method and its demodulating equipment based on cursor effect - Google Patents
A kind of spectrum demodulation method and its demodulating equipment based on cursor effect Download PDFInfo
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- G01D5/26—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
- G01D5/266—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 by interferometric means
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- G01D5/268—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 using optical fibres
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Abstract
The invention discloses a kind of spectrum demodulation method and its demodulating equipment based on cursor effect, the demodulation method includes the following steps: the cursor effect spectrum for measuring cascade structure, Fast Fourier Transform (FFT) is carried out to spectrum, obtained frequency spectrum has 3 cluster frequency contents, choose the wherein the smallest spatial frequency composition of frequency values, this spatial frequency is extracted by Gaussian filter, carrying out Fast Fourier Transform Inverse to the spatial frequency extracted can be obtained the envelope of cascade vernier spectrum.Cursor effect is formed with reference to In-line MZI by cascade and extracts the envelope of vernier spectrum, and under the same terms, the drift value of cascade vernier spectral envelope is about sensing In-line MZI spectral drift amountTimes, to realize the amplification of sensitivity.
Description
Technical field
The invention belongs to sensory field of optic fibre, specifically, be related to a kind of spectrum demodulation method based on cursor effect and its
Demodulating equipment.
Background technique
Compared to conventional electrical sensing technology, optical fiber sensing technology has small in size, light weight, high sensitivity, anti-electromagnetism
Interference is suitble to work under adverse circumstances, is easy to the advantages that being multiplexed networking, and optical fiber sensing technology has been widely used in people at present
Production and living every field.The online Mach Zehnder of optical fiber interferes (In-line in various types of fibre optical sensors
Mach-Zehnder Interferometer, In-line MZI) type sensor be people's research an emphasis, and it is traditional
Mach Zehnder interferometer is compared, and In-line MZI is a kind of all optical fibre structure, and structure is more compact, has high sensitivity, stabilization
The advantages that property is good, low in cost.
The interference spectrum of In-line MZI has usually by interfering generation between core mode and cladding mode
Multiple modes participate in interference, it is contemplated that mode effective refractive index difference is smaller between core mode and cladding mode, and cladding mode has very
Big loss, therefore, the interference spectrum of In-line MZI usually has biggish FSR and interference spectrum is multiple-mode interfence, interference
Spectrum shows typical nonperiodic phenomenon, and big FSR and multiple-mode interfence are the main feature of In-line MZI interference spectrum.
Cursor effect is applied in vernier caliper and barometer earliest, for improving the accuracy of measurement, is based on class recently
It is applied to be used to realize the amplification of spectral drift in interferometric optical fiber sensor like the optical vernier effect of principle.With vernier calliper
Ruler is similar, and traditional cursor effect requires two interferometers to have stringent periodical sine and cosine interference spectrum, and two interference spectrums are interfered
Want approximately equal in interval between striped.The demodulation method of traditional cursor effect is mainly based upon the spectrum demodulation of data envelopment fitting,
Putting for sensitivity may be implemented in the envelope that cascade vernier spectrum is obtained using the method for curve matching, the drift by measuring envelope
Greatly, amplification coefficient maximum can achieve an order of magnitude.
Spectrum is cascaded after two In-line MZI series connection in view of the spectral signature of In-line MZI described above
It is very mixed and disorderly, it can not observe apparent envelope characteristic, cannot be realized and be demodulated by the method for traditional data envelopment fitting, therefore mesh
Preceding cursor effect not yet is applied to the relevant report that In-line MZI realizes sensitivity amplification.
Summary of the invention
In view of the drawbacks of the prior art, the purpose of the present invention is to provide a kind of spectrum demodulation method based on cursor effect
And its demodulating equipment, it is intended to which the cascade spectral envelope precision for solving existing spectrum simulation technology acquisition cascaded optical fiber interferometer is low
The technical issues of.
A kind of spectrum demodulation method based on cursor effect provided by the invention, cascade vernier spectrum are concatenated by two
Fibre optic interferometer exports after incident wide range laser, and one of fibre optic interferometer acquires extraneous measured signal；This method includes
Following steps:
The conversion of spectrum frequency spectrum is carried out to cascade vernier spectrum and obtains spatial frequency frequency spectrum；
Basic frequency obtains cascade vernier spectral envelope institute in the smallest cluster frequency of frequency values in extraction spatial frequency frequency spectrum
Corresponding frequency content；Wherein, basic frequency is the frequency of amplitude maximum in the smallest cluster frequency of frequency values in spatial frequency frequency spectrum
Rate；
Frequency spectrum spectrum conversion cascade vernier spectral envelope is carried out to frequency content corresponding to cascade vernier spectral envelope；
The drift for extracting the peak wavelength or valley wavelength of cascade vernier spectral envelope, can be with by the drift value of spectrum
Obtain the variable quantity of extraneous parameter.
Preferably, fibre optic interferometer is the online Mach Zehnder interferometer of optical fiber or double beam interferometer.
Preferably, the frequency for extracting amplitude maximum in the smallest cluster frequency of frequency values in spatial frequency frequency spectrum passes through single order
Gaussian filter extracts, and the centre frequency of single order Gaussian filter is identical with basic frequency.
Preferably, spectrum frequency spectrum is converted to Fourier transformation or Fast Fourier Transform (FFT), and frequency spectrum spectrum is converted to inverse Fu
In leaf transformation or inverse fast fourier transform.
As another aspect of the present invention, the present invention provides a kind of demodulating equipment based on cursor effect, comprising:
Spectrum acquiring unit, input terminal with cascade structure one end for connecting, for obtaining and by cascade structure in width
Compose the spectrum of the output optical signal under light source is injected and as cascade vernier spectrum output, wherein cascade structure is concatenated biography
Feel fibre optic interferometer and reference optical fiber interferometer；Sensor fibre interferometer can measure measured signal；
Spectrum frequency spectrum conversion unit, input terminal are connect with the output end of spectrum acquiring unit, for cascade vernier light
Spectrum carries out Fourier transformation and exports spatial frequency frequency spectrum；
Frequency spectrum extraction unit, input terminal are connect with the output end of spectrum frequency spectrum conversion unit, for extracting and by space
In frequency spectrum in the smallest cluster frequency of frequency values basic frequency and as cascade vernier spectral envelope corresponding to frequency content
Output；
Frequency spectrum spectral translation unit, input terminal are connect with the output end of frequency spectrum extraction unit, for cascade vernier light
Frequency content corresponding to spectrum envelope carries out inverse Fourier transform output cascade vernier spectral envelope；
Drift value acquiring unit, input terminal are connect with the output end of frequency spectrum spectral translation unit, for extracting and exporting
Cascade the wavelength of vernier spectral envelope or the drift value of trough.
Preferably, demodulating equipment further includes that the wideband light source being sequentially connected in series, sensor fibre interferometer and reference optical fiber are dry
Interferometer；
Wideband light source is for exporting broad band laser；Sensor fibre interferometer is used to change fibre optic interferometer by measured signal
Effective length makes output sensing interference optical signal after being modulated processing to broad band laser drift about；Reference optical fiber interferometer is used
Output cascade vernier spectrum is handled in being modulated to the sensing interference optical signal to drift about.
Preferably, demodulating equipment further includes that the wideband light source being sequentially connected in series, reference optical fiber interferometer and sensor fibre are dry
Interferometer；
Wideband light source is for exporting broad band laser；Reference optical fiber interferometer be used for broad band laser be modulated processing after it is defeated
Interference light signal is referred to out；Sensor fibre interferometer, which is used to change fibre optic interferometer effective length by measured signal, to be made to reference
Interference light signal is modulated processing output cascade interference signal and drifts about, output cascade vernier spectrum.
Preferably, demodulating equipment further includes tunable filter, between wide spectrum light source and cascade structure, spectrum acquiring unit
It is adopted by allowing the wavelength of tunable filter in the interior scanning of wide range laser wavelength range by photodetector for photodetector
Collect each time cascade structure output optical signal and realizes the spectrum for obtaining cascade structure output optical signal and as cascade vernier light
Spectrum output.
Preferably, fibre optic interferometer is the online Mach Zehnder interferometer of optical fiber or double beam interferometer.
Preferably, need to control the adjacent resonant wavelength separation and sensing In- of the interference spectrum with reference to In-line MZI
The difference of the adjacent resonant wavelength separation of the interference spectrum of line MZI, so that cascading vernier spectrum under broad band laser input condition
Envelope at least one complete cycle.
Preferably, In-line MZI is dislocation welding structure, raised wimble structure, abrupt change wimble structure, fiber optic microbend knot
Structure, spherical structure or photonic crystal fiber airport collapsed configuration.
In general, through the invention it is contemplated above technical scheme is compared with the prior art, can obtain down and show
Beneficial effect:
(1) the spectrum demodulation method provided by the invention based on cursor effect is converted by spectrum frequency spectrum and obtains space frequency
Rate frequency spectrum, and frequency content corresponding to spatial frequency frequency spectrum cascade vernier spectral envelope is extracted, and vernier spectrum will be cascaded
Frequency content corresponding to envelope carries out frequency spectrum conversion, obtains cascade vernier spectral envelope, compared to existing using bent
It is higher to obtain cascade vernier spectral envelope precision for the method for line fitting.
(2) traditional optical vernier effect obtains the envelope of cascade vernier spectrum using the method for curve matching, it is desirable that passes
Sense and reference interferometer have stringent periodical sine and cosine interference spectrum, since the interference spectrum of In-line MZI has phase
Adjacent resonant wavelength separation (FSR, Free Spectral Range) greatly, periodical poor feature, therefore traditional cursor effect is not
In-line MZI can be applied.Cursor effect provided by the invention, to sensing and with reference to the cascade of In-line MZI on frequency spectrum
Vernier spectrum is analyzed, and the corresponding frequency content of envelope is then extracted, can be from mixed and disorderly cascade vernier light by IFFT
Its envelope is extracted in spectrum, is divided between envelopeRelative to sensing In-line MZI interference spectrum
Drift be exaggeratedTimes.
(3) the invention proposes cursor effect photosensitivity-enhancing methods, can be realized optical fiber In-line MZI type transducer sensitivity
Amplification, comprehensively consider the spectrum width of light source and the FSR size of In-line MZI, may be implemented maximum to be more than an order of magnitude
Sensitivity enlargement ratio.
(4) present invention can be adapted for most of In-line MZI to the cursor effect spectrum demodulation method of proposition
The sensitivity enhanced sensitivity of type fibre optical sensor.This method also can be applied to traditional optical fiber based on two-beam interference structure simultaneously
The enhanced sensitivity of sensor, compared to traditional method for obtaining envelope by curve matching, this method has higher accuracy.
Detailed description of the invention
Fig. 1 is a kind of flow chart of the spectrum demodulation method based on cursor effect provided in an embodiment of the present invention；
Fig. 2 is the structure chart of the first embodiment of the spectrum demodulating equipment provided by the invention based on cursor effect；
Fig. 3 is the structure chart of the second embodiment of the spectrum demodulating equipment provided by the invention based on cursor effect；
In all the appended drawings, identical appended drawing reference is used to denote the same element or structure, wherein 1 for wideband light source,
2 be sensing In-line MZI, 3 be with reference to In-line MZI, 4 spectroanalysis instruments, 5 signal processing unit, 501 be spectrum frequency
Spectrum conversion unit, 502 be frequency spectrum extraction unit, 503 be frequency spectrum spectral translation unit, 504 be drift value acquiring unit.
Specific embodiment
In order to make the objectives, technical solutions, and advantages of the present invention clearer, with reference to the accompanying drawings and embodiments, right
The present invention is further elaborated.It should be appreciated that the specific embodiments described herein are merely illustrative of the present invention, and
It is not used in the restriction present invention.
For the defect and demand of existing demodulation techniques, the present invention proposes the spectrum demodulation method based on cursor effect, this
Method can be suitable for most optical fiber In-line MZI type sensors, improve the precision for obtaining cascade spectral envelope, simultaneously
Realize the amplification of spectral drift amount, the drawbacks of overcoming traditional vernier benefit spectrum simulation method, the extraction of envelope is very accurate, energy
It is enough that an order of magnitude is amplified to the drift value of spectrum.This method can be applied not only to traditional dual-beam fibre optic interferometer, more
It can be applied to most optical fiber In-line MZI type sensors.
Traditional dual-beam fibre optic interferometer includes optical branching structure, pickup arm, reference arm and combiner structure, light warp
It crosses after optical branching structure and is divided into two-way and respectively enters pickup arm and reference arm, pickup arm and reference arm have certain optical path difference,
Last light is by combiner structure Coupling and interferes, therefore only two-beam participates in interference, and interference spectrum is periodic sinusoidal
Structure, and only include a frequency content, only one frequency content f is distinguished with reference to the interference spectrum with sensing interferometerSAnd fR。
Therefore for traditional cascade spectrum based on two-beam interference structure, frequency spectrum contains 4 frequency contents | fS-fR
|、|fS+fR|、fSAnd fS.According to its frequency values it is found that | fS-fR| for frequency content corresponding to cascade vernier spectral envelope.
For there are two the cascade structures of frequency content, analyzed as an example with In-line MZI.
Wherein, the interference spectrum of In-line MZI is interfered with core mode by the cladding mode in optical fiber and is generated, if only
Consider that two modes interfere, then the interference spectrum for sensing In-line MZI can be with approximate representation
A in expression formulaSFor the DC component of interference signal, power, system loss and the increasing of photoelectric probe with light source
Benefit etc. is related, BSIndicate the visibility of striped；ΔnSIt is poor for effective refractive index, Δ nS=(neff co-neff cl), wherein neff coFor fibre
The effective refractive index of core model, neff clFor the effective refractive index of cladding mode；λ is operation wavelength,For initial phase, LSFor In-
The effective length of line MZI structure.
When operation wavelength meets λm=2 (neff co-neff cl)LSWhen/(2m+1) (m is integer), there is valley in interference spectrum.
When extraneous parameter (temperature, refractive index, strain, curvature) changes, effective length LSAnd effective refractive index
Difference can change, therefore valley wavelength can change, i.e., spectrum generates drift, in a certain range, the drift of spectrum
Linear relationship is presented in amount and the variable quantity of extraneous parameter.With reference to the interference spectrum I of In-line MZIRSimilar table can also be used
It is indicated up to formula.
Wherein, the In-line MZI reported at present generally has 2 cladding modes to interfere with core mode, one of them
The energy of cladding mode is much larger than another, leading role is accounted in interference, therefore actually sense In-line MZI and reference
The interference spectrum of In-line MZI contains two spaces frequency: f respectivelyS1、fS2And fR1、fR2, wherein fS1And fR1For dominant frequency at
Point, the amplitude of respective frequencies ingredient is much larger than another frequency content, and fS1With fR1It is approximately equal.When two interferometer strings
After connection, the product of both cascade spectrum can be expressed as respective interference spectrum, i.e. IC=ISIR。
Likewise, for In-line MZI structure, interference spectrum contains two spaces frequency content.As sensing In-line
After MZI connects with reference In-line MZI, cascade spectrum contains 12 frequency contents, can be divided into 3 clusters, be expressed as,
First cluster: | fS1-fR1|、|fS1-fR2|、|fS2-fR1|、|fS2-fR2|；Second cluster: fS1、fS2、fR1And fR2；And third cluster: fS1+
fR1、fS1+fR2、fS2+fR1、fS2+fR2.It is similar with traditional structure, in the first cluster | fS1-fR1| for the frequency of cascade spectral envelope
Rate ingredient.
Wherein, | fS1-fR1| with | fS1-fR2| and | fS2-fR1| value there are notable differences, but with | fS2-fR2| value connect
Closely, however further analysis shows that | fS1-fR1| the amplitude of respective frequencies ingredient is much larger than | fS2-fR2| amplitude, therefore can be with
Easily extracted on frequency spectrum | fS1-fR1| frequency content.
Spectrum demodulation method provided by the invention based on cursor effect includes the following steps:
(1) it connects sensing In-line MZI and reference In-line MZI that FSR is close to form cursor effect, obtain
The cascade vernier spectrum of cascaded structure；
(2) frequency spectrum that FFT obtains cascade structure spatial frequency is carried out to cascade vernier spectrum；
(3) frequency spectrum of cascaded structure is analyzed, in frequency contain 3 cluster frequency contents, wherein frequency values it is the smallest that
Major frequency components in cluster are frequency content corresponding to cascade vernier spectral envelope, extract the frequency using Gaussian filter
Ingredient；
(4) carrying out IFFT to the frequency content extracted can be obtained the envelope of cascade vernier spectrum.
(5) drift of the peak wavelength or valley wavelength of measurement cascade vernier spectral envelope, passes through the drift value of spectrum
The variable quantity of available external world's parameter.The drift of vernier spectral envelope is cascaded relative to sensing In-line MZI interference spectrum
Drift is exaggerated FSRS/(|FSRS-FSRR|) times.
The method for extracting frequency content corresponding to cascade vernier spectral envelope can be specifically described as follows:
Firstly, analyzing cascaded structure frequency spectrum, envelope frequency is found on frequency spectrum | fS1-fR1| corresponding space
Frequency peak measures the head room frequency and three dB bandwidth at its corresponding frequencies peak；Then, using with identical peak value and 3dB band
Width carries out bandpass filtering to cascaded structure frequency spectrum slightly larger than the single order Gaussian filter of frequency peak three dB bandwidth, so that it may extract
The corresponding frequency content of envelope.
In spectrum demodulation method embodiment provided by the invention, vernier spectrum can also will be cascaded using Fourier transformation
It is converted into the frequency spectrum of cascade structure spatial frequency.Using inverse Fourier transform will cascade vernier spectral envelope corresponding to frequency at
Divide and is converted into cascade vernier spectral envelope.
In embodiments of the present invention, the spectrum demodulation method of cursor effect proposed by the present invention, using the side of spectrum analysis
Method extracts the corresponding frequency content of envelope, and the envelope of cascade vernier spectrum is accurately obtained by IFFT.Compared to tradition
Cursor effect in the curve matching method that obtains cascade vernier spectral envelope, this method is more accurate to the extraction of envelope, fast
Speed, and overcome the shortcomings that conventional method may not apply to In-line MZI.
Fig. 2 is the structure chart of the first embodiment of the spectrum demodulating equipment provided by the invention based on cursor effect, the light
Spectrum demodulating equipment includes the spectrum acquiring unit 4 being sequentially connected in series, spectrum frequency spectrum conversion unit 501, frequency spectrum extraction unit 502, frequency
Compose spectral translation unit 503 and drift value acquiring unit 504.
Spectrum acquiring unit input terminal with cascade structure one end for connecting.Cascade structure is the interference of concatenated sensor fibre
Instrument and reference optical fiber interferometer, for sensor fibre interferometer for measuring measured signal, cascade structure is defeated under the injection of wide range laser
Interference light signal out.Spectrum acquiring unit is used to extract the spectral signal of interference light signal as cascade vernier spectrum output.Light
Frequency spectrum conversion unit is composed to be used to carry out Fourier transformation to cascade vernier spectrum to export spatial frequency frequency spectrum；Frequency spectrum extraction unit is used
In extraction and by basic frequency in the smallest cluster frequency of frequency values in spatial frequency frequency spectrum and as cascade vernier spectral envelope institute
Corresponding frequency content output；Frequency spectrum spectral translation unit is used to carry out frequency content corresponding to cascade vernier spectral envelope
Inverse Fourier transform output cascade vernier spectral envelope；Drift value acquiring unit is for extracting simultaneously output cascade vernier spectral envelope
Wavelength or the drift value of trough obtain cascade vernier spectral envelope essence compared to the existing method using curve matching
Du Genggao.
Fig. 3 is the structure chart of the second embodiment of the spectrum demodulating equipment provided by the invention based on cursor effect, the light
Composing demodulating equipment includes wideband light source 1, sensor fibre interferometer 2, reference optical fiber interferometer 3, spectroanalysis instrument 4 and signal processing
Unit 5.Wherein, signal processing unit includes the spectrum frequency spectrum conversion unit 501 being sequentially connected in series, frequency spectrum extraction unit 502, frequency spectrum
Spectral translation unit 503 and drift value acquiring unit 504.The broadband light that wideband light source 1 exports is input to sensor fibre interference
Instrument 2 commonly uses wideband light source, and such as ASE light source, SLED etc., bandwidth is usually 100nm or so, and sensor fibre interferometer is used to survey
The variation of extraneous parameter is measured, the variation of extraneous parameter (such as temperature, refractive index, strain, curvature) is loaded into sensor fibre interferometer
On.The dry spectrum of sensor fibre interferometer can occur to drift about accordingly with the variation of extraneous parameter, in a certain range,
Good linear relationship is presented in the variable quantity of the drift value of spectrum and extraneous parameter.Letter is tested in the light load transmitted in optical fiber
Reference optical fiber interferometer 3 is input to after number, reference optical fiber interferometer is kept constant as reference section working environment, is joined with the external world
The variation of amount is kept apart, it is believed that the interference spectrum approximate constant of reference optical fiber interferometer.Last entire tandem junction
The cascade vernier spectrum of structure is input to spectroanalysis instrument 4, and the spectral information of spectroanalysis instrument is output to the progress of signal processing unit 5
Relevant operation, extracts the envelope of cascade vernier spectrum, and calculates the drift of spectral envelope.
Further, sensor fibre interferometer and reference optical fiber interferometer are to be connected in series, the order of connection pair of the two
Experimental result does not influence.When fibre optic interferometer is in-line MZI, according to the difference of in-line MZI composed structure, input
Optical signal can be using transmission-type or using reflective.
In embodiment provided by the invention, fibre optic interferometer selects In-line MZI, in order to generate cursor effect, sensing
Effective active length of In-line MZI is close with effective active length with reference to In-line MZI, so that the two is dry
The FSR for relating to spectrum is close, the sizes of the major frequency components of interference spectrum also close to.By the working principle of In-line MZI it is found that sensing
The interference spectrum of In-line MZI and reference In-line MZI usually have biggish FSR, vernier interference spectrum packet after cascade
The FSR of network can be expressed as FSRC=FSRR FSRS/(|FSRS-FSRR|), in order to accurately observe the drift of vernier spectral envelope
It moves, needs at least to observe a complete cycle of vernier interference spectrum envelope in the limited spectral region of wideband light source, because
This needs comprehensively considers sensing In-line MZI and the FSR with reference to In-line MZI, controls the difference between them and to swim
The FSR of interference spectrum envelope is marked within acceptable range.
It in embodiments of the present invention, can be using another scheme for cascading the acquisition of vernier spectrum.Wideband light source is defeated
Light out forms monochromatic light after automatically controlled high speed tunable filter, and monochromatic light is incident on photodetection after cascaded structure
Device, photodetector convert optical signals to electric signal, and electric signal is input to data acquisition unit, adjust the adjustable filter of automatically controlled high speed
Wave device realizes scanning in certain wave-length coverage in a relatively short period of time, and so in different times, data acquisition unit will
The strength information of different wave length is collected to obtain the spectrum of cascaded structure, the collected spectroscopic data of data acquisition unit is defeated
Enter to signal processing unit and handled, extract the envelope of cascade vernier spectrum and obtains the drift of envelope.
In embodiments of the present invention, the amplification of spectral drift may be implemented in the spectrum demodulating equipment of the cursor effect of proposition,
To effectively improve the sensitivity of cascade structure.This method can either be applied to traditional based on two-beam interference type interferometer stage
The structure of connection also can be applied to most based on the cascade structure of In-line MZI.The composition of In-line MZI can be with
For dislocation welding structure, raised wimble structure, abrupt change wimble structure, fiber optic microbend structure, spherical structure, photonic crystal fiber air
Hole collapsed configuration etc..
In embodiments of the present invention, it senses In-line MZI and is produced with reference to In-line MZI by single mode optical fiber dislocation welding
Raw, the fiber lengths of dislocation welding are respectively 4.5cm and 5cm.Complete the measurement of temperature and curvature, temperature and curvature it is sensitive
Degree is exaggerated 8.9 times and 8.1 times respectively.
In embodiments of the present invention, the drift of vernier spectral envelope is cascaded relative to sensing In-line MZI interference spectrum
Drift is exaggerated M=FSRS/(|FSRS-FSRR|) times.The FSR of vernier interference spectrum envelope can be expressed as FSR after cascadeC=
FSRR FSRS/(|FSRS-FSRR|).Due to the limited spectrum of wideband light source and the FSR of In-line MZI structure is usually larger,
In order at least observe a complete cycle of vernier interference spectrum envelope in the spectral region of wideband light source, therefore | FSRS-
FSRR| difference cannot be too small, enlargement ratio M is usually 10 or so.
As it will be easily appreciated by one skilled in the art that the foregoing is merely illustrative of the preferred embodiments of the present invention, not to
The limitation present invention, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should all include
Within protection scope of the present invention.
Claims (10)
1. a kind of spectrum demodulation method based on cursor effect, cascade vernier spectrum is to be entered by two concatenated fibre optic interferometers
It is exported after penetrating wide range laser, one of fibre optic interferometer acquires extraneous measured signal, which is characterized in that this method includes as follows
Step:
The conversion of spectrum frequency spectrum is carried out to cascade vernier spectrum and obtains spatial frequency frequency spectrum；
Basic frequency obtains corresponding to cascade vernier spectral envelope in the smallest cluster frequency of frequency values in extraction spatial frequency frequency spectrum
Frequency content；Wherein, basic frequency is the frequency of amplitude maximum in the smallest cluster frequency of frequency values in spatial frequency frequency spectrum；
Frequency spectrum spectrum conversion cascade vernier spectral envelope is carried out to frequency content corresponding to cascade vernier spectral envelope；
The drift of the peak wavelength or valley wavelength of cascade vernier spectral envelope is extracted, it is available by the drift value of spectrum
The variable quantity of extraneous parameter.
2. the spectrum demodulation method based on cursor effect as described in claim 1, which is characterized in that the fibre optic interferometer is light
Fine online Mach Zehnder interferometer or double beam interferometer.
3. the spectrum demodulation method based on cursor effect as claimed in claim 1 or 2, which is characterized in that extract spatial frequency frequency
The frequency of amplitude maximum is extracted by single order Gaussian filter in the smallest cluster frequency of frequency values in spectrum, single order Gaussian filter
Centre frequency it is identical with basic frequency.
4. the spectrum demodulation method based on cursor effect as claimed in claim 1 or 2, which is characterized in that spectrum frequency spectrum is converted to
Perhaps Fast Fourier Transform (FFT) frequency spectrum spectrum is converted to inverse Fourier transform or inverse fast fourier transform to Fourier transformation.
5. a kind of spectrum demodulating equipment based on demodulation method described in claim 1 characterized by comprising
Spectrum acquiring unit, input terminal with cascade structure one end for connecting, for obtaining and by cascade structure in wide spectrum optical
The spectrum of output optical signal under the injection of source is simultaneously exported as cascade vernier spectrum, wherein cascade structure is concatenated sense light
Fine interferometer and reference optical fiber interferometer；Sensor fibre interferometer can measure measured signal；
Spectrum frequency spectrum conversion unit, input terminal are connect with the output end of spectrum acquiring unit, for cascade vernier spectrum into
Row Fourier transformation exports spatial frequency frequency spectrum；
Frequency spectrum extraction unit, input terminal are connect with the output end of spectrum frequency spectrum conversion unit, for extracting and by spatial frequency
In frequency spectrum in the smallest cluster frequency of frequency values basic frequency and as cascade vernier spectral envelope corresponding to frequency content output；
Frequency spectrum spectral translation unit, input terminal are connect with the output end of frequency spectrum extraction unit, for cascade vernier spectrum packet
Frequency content corresponding to network carries out inverse Fourier transform output cascade vernier spectral envelope；
Drift value acquiring unit, input terminal are connect with the output end of frequency spectrum spectral translation unit, for extracting simultaneously output cascade
The wavelength of vernier spectral envelope or the drift value of trough.
6. spectrum demodulating equipment as claimed in claim 5, which is characterized in that demodulating equipment further includes the broadband light being sequentially connected in series
Source, sensor fibre interferometer and reference optical fiber interferometer；
Wideband light source is for exporting broad band laser；Sensor fibre interferometer is used to change fibre optic interferometer by measured signal effective
Length makes output sensing interference optical signal after being modulated processing to broad band laser drift about；Reference optical fiber interferometer for pair
The sensing interference optical signal to drift about is modulated processing output cascade vernier spectrum.
7. spectrum demodulating equipment as claimed in claim 5, which is characterized in that demodulating equipment further includes the broadband light being sequentially connected in series
Source, reference optical fiber interferometer and sensor fibre interferometer；
Wideband light source is for exporting broad band laser；Reference optical fiber interferometer is used to export ginseng after being modulated broad band laser processing
Examine interference light signal；Sensor fibre interferometer, which is used to change fibre optic interferometer effective length by measured signal, to be made to interfere reference
Optical signal is modulated processing output cascade interference signal and drifts about, output cascade vernier spectrum.
8. such as the described in any item spectrum demodulating equipments of claim 5 to 7, which is characterized in that fibre optic interferometer is that optical fiber is online
Mach Zehnder interferometer or double beam interferometer.
9. such as the described in any item spectrum demodulating equipments of claim 5 to 7, which is characterized in that the control online Mach of reference optical fiber
The adjacent resonant wavelength separation of the interference spectrum of Zehnder interferometer and the interference spectrum of the online Mach Zehnder interferometer of sensor fibre
Adjacent resonant wavelength separation difference so that cascading the envelope of vernier spectrum under broad band laser input condition, at least one is complete
Complete cycle.
10. such as the described in any item spectrum demodulating equipments of claim 5 to 7, which is characterized in that the online Mach Zehnder interference of optical fiber
Instrument is dislocation welding structure, raised wimble structure, abrupt change wimble structure, fiber optic microbend structure, spherical structure or photonic crystal fiber
Airport collapsed configuration.
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| CN111313983B (en) * | 2020-02-17 | 2021-10-26 | 湖南工学院 | Microwave instantaneous frequency extraction and amplification method and instantaneous frequency measurement method and system |
| CN113155164B (en) * | 2021-03-29 | 2022-12-20 | 广州大学 | Sensitivity amplification method, device, equipment and medium based on virtual reference interference |
| CN113358037B (en) * | 2021-08-10 | 2021-11-09 | 中国计量科学研究院 | Laser displacement measuring device and method |
| CN113805125B (en) * | 2021-09-30 | 2022-09-13 | 重庆大学 | High-sensitivity optical fiber magnetic field sensor based on optical vernier effect |
| CN114279605A (en) * | 2021-12-15 | 2022-04-05 | 南京信息工程大学 | Stress optical fiber sensor with high-sensitivity refractive index based on vernier effect enhancement |
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