CN100478658C - Double edge filter wave length demodulator and its demodulating method - Google Patents
Double edge filter wave length demodulator and its demodulating method Download PDFInfo
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- CN100478658C CN100478658C CNB2004100608831A CN200410060883A CN100478658C CN 100478658 C CN100478658 C CN 100478658C CN B2004100608831 A CNB2004100608831 A CN B2004100608831A CN 200410060883 A CN200410060883 A CN 200410060883A CN 100478658 C CN100478658 C CN 100478658C
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Abstract
The double edge filter wavelength demodulator and demodulation method is mainly used in the measurement of narrow band light wavelength in Bragg fiber grating reflection. The demodulator includes light source, two light splitters, two light filters, two photoelectronic conversion modules, double path A/D converter module and microprocessor. The demodulation method includes connecting two light filters in two light paths of the same light splitter with overlapped spectral characteristics, making reflected light carrying sensing information pass through the two overlapped light paths to output different spectrums corresponding to the spectral characteristics, and measuring the wavelength indirectly with the logarithm value of the output light strength ratio of these two filters. The said method can solve the problem of unstable linearity of optical devices and unstable light strength and has higher measurement speed, stability and precision compared with scanning method.
Description
One, technical field
The present invention is a kind of dual edge filter wavelength detuner and demodulation method thereof, is mainly used in the measurement of the narrow band light wavelength of Fiber Bragg Grating FBG reflection, belongs to field of sensing technologies.
Two, background technology
Existing Wavelength demodulation technology substantially can be divided three classes according to demodulation principle, laser of narrowband light source scanning method, wideband light source narrow-band filtering scanning method, also has the demodulation method that wavelength is converted into other parameter.The demodulation method of length scanning is a demodulation method commonly used now, but be that the modulated light source scanning or the method for filter scan all inevitably will be introduced mechanical movable part in demodulating equipment, this part has independent circuit control again, the more complicated that causes device, secondly its sweep velocity has also limited the speed of demodulation.
Edge filter is a kind of existing Wavelength demodulation technology, belong to the method that wavelength is converted into light intensity, its the texture ratio now demodulation mode of length scanning commonly used is simple, comprises that wideband light source, sensing grade with Fiber Bragg Grating FBG, wave filter, photoelectric conversion unit and amplification, display part.Its principle mainly is to export the principle of certain strength light when utilizing the grating reflection spectrum by wave filter, when the wavelength shift of reflectance spectrum, the light intensity of output also can correspondingly change, intensity becomes certain proportionate relationship with wavelength value, but because its following shortcoming, generally be not employed now: (i) light intensity instability, be subjected to many-sided influences such as light source, transmission range, fibre-optical splice decay, measured wavelength value accuracy is not high; (ii) too high to the requirement of filtering device, require the spectral distribution of wave filter that the linear characteristic of 1-2nm is arranged, this is unlikely for general optical device.
Three, summary of the invention
The method of the present invention and traditional edge filter detuner and demodulation relatively, it was former to the demanding problem of device spectrum linear characteristic to adopt general optical filter spare just can solve, and was not imported the influence of light intensity.Compare with the method for the scanning demodulation of using always now, so owing to do not exist mechanical movable part operation more stable, demodulation speed is faster.
The present invention is a kind of dual edge filter wavelength detuner and demodulation method thereof, wavelengt demodulator is mainly simulated a digital signal modular converter, microprocessor and display part and is formed by device 3, first optical branching device 1, second optical branching device 2, first optical filter, second optical filter, first photoelectric conversion module, second photoelectric conversion module, the two-way of light source, selection specific wavelength, its syndeton is: the terminal of closing of first optical branching device 1 connects the terminal of closing that 3, two branch terminals of device of selecting specific wavelength connect the light source and second optical branching device 2 respectively; Two branch terminals of second optical branching device 2 are connected with second optical filter with first optical filter respectively; First optical filter, the second optical filter light path output terminal connect first photoelectric conversion module, second photoelectric conversion module respectively, detect the light intensity of optical filter output; First photoelectric conversion module, second photoelectric conversion module connect two-way and simulate a digital signal modular converter, and the digital signal of output enters microprocessor, carries out the data processing of division and logarithm operation and exports shows signal.
Foregoing light source is a wideband light source, is connected a branch terminal of first optical branching device 1, and for the light path part of this device provides light source, its effective wavelength range is greater than the wavelength measurement scope of this demodulating equipment.
The device 3 optional Fiber Bragg Grating FBGs of using of foregoing selection specific wavelength are connected the terminal of closing of first optical branching device 1.
Foregoing first optical filter and second optical filter are connected in two shunt of second optical branching device 2, they are the approximate optical device that meet Gaussian of spectral characteristic, can select for use as broadband grating etc.
The principle of work of dual edge demodulation by filter method and data processing is: the broadband light of light source output is imported a shunt of first optical branching device 1, through selecting the device 3 of specific wavelength, returns the narrow band light of a specific wavelength.This narrow band light turns back to the terminal of closing that another minute terminal of first optical branching device 1 enters second optical branching device 2, and this narrow band light is on average assigned in first optical filter and second optical filter by second optical branching device 2.The spectral characteristic of first optical filter and second optical filter overlaps, and as shown in Figure 2, crossover partly is the effective range of wavelength measurement.The tested narrow band light while one is input to first photoelectric conversion module, second photoelectric conversion module respectively by first optical filter 1 and second optical filter, detects the light intensity of optical filter output, exports two analog electrical signals.This simulating signal enters two-way and simulates a digital signal modular converter, and the digital signal of output enters microprocessor, carries out the data processing of division and logarithm operation and exports shows signal.
The data processing that foregoing microprocessor carries out is that the electric signal from two photoelectric conversion modules is carried out division arithmetic, then total is done logarithm operation and is obtained ρ (x).Linear according to Theoretical Calculation and experimental result sensing with the wavelength x and the ρ (x) of Fiber Bragg Grating FBG, thus the x value can be obtained by the value of measuring ρ (x), the principle of wavelength detection of the present invention that Here it is.
Foregoing microprocessor can replace with divider and logarithm device, is connected the digital signal output end that two-way is simulated a digital signal modular converter, realizes data processing with hardware.
Can seeing the spectral characteristic of this linear relationship of x and ρ (x) and wave filter, whether linear it doesn't matter, so avoided in traditional edge filter demodulation method the high request to wave filter.The sensitivity of wavelength measurement, promptly the slope of wavelength x and ρ (x) relation is to determine it and D=[(Δ λ by the bandwidth of sensing with Fiber Bragg Grating FBG and wave filter
F2+ Δ λ
F1)/2]
2+ Δ λ
b 2The relation of being inversely proportional to, promptly sensing is also big more with the big more then D of bandwidth of Fiber Bragg Grating FBG and wave filter.The variation of light intensity is very little to the influence of measured value ρ (x) as can be known by Theoretical Calculation.
There is not any mechanical movable part from this system of structure separating timing, faster than the demodulation method measuring speed of scan-type, more stable more accurate during operation.
Description of drawings
Fig. 1, dual edge filter wavelength demodulator structure synoptic diagram
The spectrum character diagram of Fig. 2, optical filter and tested narrow band light
Fig. 3, realize the dual edge filter wavelength demodulator structure synoptic diagram of data processing with hardware
Fig. 4, experimental data figure
Embodiment
Scheme one:
Dual edge filter wavelength demodulating system comprises by wideband light source, sensing and simulates a digital signal modular converter, microprocessor and display part with Fiber Bragg Grating FBG, first optical branching device 1, second optical branching device 2, first optical filter, second optical filter, first photoelectric conversion module 1, second photoelectric conversion module, two-way as shown in Figure 1.The principle of work of its demodulation and data processing is the branch terminal input light path of the broadband light of wideband light source output through first optical branching device 1, through sensing Fiber Bragg Grating FBG, the narrow band light of a specific wavelength of reflected back.The terminal of closing that another minute terminal of this first optical branching device 1 of narrow band light process enters second optical branching device 2, this transducing signal is assigned in two wave filters with 50: 50 ratio by second optical branching device.The spectral characteristic of two wave filters overlaps, and crossover is the effective range for measuring partly, and promptly tested wavelength is in the crossover part of two wave filter transmission spectrums, and tested like this wavelength can be distinguished simultaneously by two wave filters.First photoelectric conversion module, second photoelectric conversion module are connected with first optical filter, the second optical filter light path output terminal respectively, detect the light intensity of optical filter output: two-way is simulated a digital signal modular converter and is connected with first photoelectric conversion module, the second photoelectric conversion module electrical signal simultaneously; The digital signal of output enters microprocessor, carries out the data processing of division and logarithm operation and exports shows signal.
Foregoing first optical filter and second optical filter are connected in two shunt of same optical branching device, their spectral characteristic is to overlap as shown in Figure 2, and the approximate optical device that meets Gaussian, the homemade broadband grating selected for use of optical filter in an embodiment, centre wavelength is respectively 1301nm and 1302nm, bandwidth 1nm, spectrum crossover part is greater than 700pm.The foregoing Fiber Bragg Grating FBG that is used for sensing, the centre wavelength of grating are 1301.400nm.
Foregoing dual edge filter wavelength detuner and demodulation method thereof, wherein first photoelectric conversion module, second photoelectric conversion module are connected with first optical filter, second optical filter respectively, detect the light intensity of optical filter output, photoelectric conversion module selects for use photoelectric diode (GD3553Y) and amplifier (CA3 140) to form.
The data processing that foregoing microprocessor carries out is that the electric signal from two photoelectric conversion modules is carried out division arithmetic, then total is done logarithm operation and is obtained ρ (x).Linear according to Theoretical Calculation and experimental result sensing with the wavelength x and the ρ (x) of Fiber Bragg Grating FBG, can obtain the principle of wavelength detection of the present invention that Here it is by the value of measuring ρ (x) from the x value.
In order to verify the performance of this demodulating system, used SYG one WK fiber grating experiment temperature controller (science and engineering Lightology LLC) among the embodiment, by regulating the centre wavelength of temperature control sensing with grating; Also have a spectroanalysis instrument, be used to measure sensing under this temperature and compare with the centre wavelength of grating measured value as actual value and this device.Be experimental data figure as shown in Figure 4, the wavelength value that measured value ρ as can be seen from the figure of the present invention (x)=log (V1/V2) and spectroanalysis instrument are measured is linear substantially, satisfies relational expression y=0.187lx+1301.5136.
Scheme two:
As Fig. 3. shown in dual edge filter wavelength demodulating equipment, comprise by wideband light source, sensing and simulate a digital signal modular converter, divider, logarithm device and display part with Fiber Bragg Grating FBG, first optical branching device 1, second optical branching device, first optical filter, second optical filter, first photoelectric conversion module, second photoelectric conversion module, two-way.The principle of work of its demodulation and data processing is the branch terminal input light path of the broadband light of wideband light source output through first optical branching device 1, through sensing Fiber Bragg Grating FBG, the narrow band light of a specific wavelength of reflected back.The terminal of closing that another minute terminal of this first optical branching device 1 of narrow band light process enters second optical branching device 2, this transducing signal is assigned in two wave filters with 50: 50 ratio by second optical branching device.The spectral characteristic of two wave filters overlaps, and crossover is the effective range for measuring partly, and promptly tested wavelength is in the crossover part of two wave filter transmission spectrums, and tested like this wavelength can be distinguished simultaneously by two wave filters.First photoelectric conversion module, second photoelectric conversion module are connected with first optical filter, the second optical filter light path output terminal respectively, detect the light intensity of optical filter output; Two-way is simulated a digital signal modular converter and is connected with first photoelectric conversion module, the second photoelectric conversion module electrical signal simultaneously; The digital signal of output enters divider and carries out division arithmetic, and the result sends into the logarithm device and carries out logarithm operation, and operation result send demonstration.
Foregoing first optical filter and second optical filter are connected in two shunt of same optical branching device, they are the approximate optical device that meet Gaussian of spectral characteristic, the homemade broadband grating selected for use of optical filter in an embodiment, centre wavelength is respectively 1301nm and 1302nm, bandwidth 1nm, spectrum crossover part is greater than 700Pm.Foregoing sensing Fiber Bragg Grating FBG, the centre wavelength of grating are 1301.400nm.
Foregoing dual edge filter wavelength demodulating system, wherein first photoelectric conversion module, second photoelectric conversion module are connected with first optical filter, second optical filter respectively, detect the light intensity of optical filter output, photoelectric conversion module selects for use photoelectric diode (GD3553Y) and amplifier (CA3140) to form.
Claims (7)
1, a kind of dual edge filter wavelength detuner: mainly simulate a digital signal modular converter, microprocessor and display part and form by device (3), first optical branching device (1), second optical branching device (2), first optical filter, second optical filter, first photoelectric conversion module, second photoelectric conversion module, the two-way of light source, selection specific wavelength, the terminal of closing that it is characterized in that first optical branching device (1) connects the device (3) of selecting specific wavelength, and (1) two branch terminal of first optical branching device connects the terminal of closing of light source and second optical branching device (2) respectively; Second optical branching device (2) is assigned to two branch terminals with 50: 50 ratio and is connected with second optical filter with first optical filter respectively; The spectral characteristic of two wave filters overlaps, and crossover is the effective range for measuring partly, and first optical filter, the second optical filter light path output terminal connect first photoelectric conversion module, second photoelectric conversion module respectively, detects the light intensity of optical filter output; First photoelectric conversion module, second photoelectric conversion module connect two-way and simulate a digital signal modular converter, the digital signal of output enters microprocessor, the data processing that microprocessor carries out is that the electric signal from two photoelectric conversion modules is carried out division arithmetic, then total is done logarithm operation and is obtained ρ (x).
2, a kind of dual edge demodulation by filter method, it is characterized in that the broadband light of light source output imports a shunt of first optical branching device (1), through selecting the device (3) of specific wavelength, return the narrow band light of a specific wavelength, this narrow band light turns back to the terminal of closing that another minute terminal of first optical branching device (1) enters second optical branching device (2), this narrow band light is on average assigned in first optical filter and second optical filter by second optical branching device (2), the spectral characteristic of first optical filter and second optical filter overlaps, the optical device that meets Gaussian, crossover is partly for the effective range of wavelength measurement, tested narrow band light is input to first photoelectric conversion module and second photoelectric conversion module by first optical filter and second optical filter respectively simultaneously, detect the light intensity of optical filter output, export two analog electrical signals, this simulating signal enters two-way and simulates a digital signal modular converter, the digital signal of output enters microprocessor, the data processing that microprocessor carries out is that the electric signal from two photoelectric conversion modules is carried out division arithmetic, then total is done logarithm operation and is obtained ρ (x).
3, dual edge filter wavelength detuner as claimed in claim 1 is characterized in that light source selects wideband light source for use.
4, dual edge filter wavelength detuner as claimed in claim 1 is characterized in that selecting the device (3) of specific wavelength to select Fiber Bragg Grating FBG for use.
5, dual edge filter wavelength detuner as claimed in claim 1 is characterized in that first optical filter and second optical filter are the broadband gratings.
6, a kind of dual edge demodulation by filter method as claimed in claim 2, it is characterized in that the data processing that microprocessor carries out is that the electric signal from two photoelectric conversion modules is carried out division arithmetic, then total is done logarithm operation and obtained ρ (x), tested arrowband light wavelength: x and ρ (x) are linear.
7, a kind of dual edge demodulation by filter method as claimed in claim 2 is characterized in that microprocessor replaces with divider and logarithm device, is connected the digital signal output end that two-way is simulated a digital signal modular converter, realizes data processing with hardware.
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| CN101769762B (en) * | 2010-01-29 | 2011-10-19 | 武汉理工大学 | Sensing demodulating system for optical chirped-grating |
| CN105628065B (en) * | 2015-12-22 | 2017-12-08 | 南京工程学院 | A kind of fiber grating signal demodulating equipment and demodulation method |
| CN105910550A (en) * | 2016-06-24 | 2016-08-31 | 桂林创研科技有限公司 | Distributed optical fiber Bragg grating demodulation system |
| CN106644036A (en) * | 2016-12-26 | 2017-05-10 | 华中科技大学 | Sound wave detector based on polymer thin film and dual-wavelength demodulation method |
| CN108152006B (en) * | 2017-12-05 | 2019-07-09 | 浙江大学 | A kind of test device and method that back reflected laser ratio influences wideband light source |
| CN109506687A (en) * | 2018-12-26 | 2019-03-22 | 中国工程物理研究院流体物理研究所 | A kind of measuring system and measurement method for dynamic test |
| CN111521206B (en) * | 2020-07-03 | 2020-10-13 | 武汉智慧地铁科技有限公司 | Wavelength demodulation method for fiber grating edge superposition filtering |
| CN114812634A (en) * | 2022-04-19 | 2022-07-29 | 南京邮电大学 | Fiber grating wavelength demodulator |
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Effective date of registration: 20091218 Address after: Hubei city of Wuhan province Wuchang Luoshi Road No. 122 Patentee after: Wuhan Ligong Guangke Co., Ltd. Address before: Hubei city of Wuhan province Wuchang Luoshi Road No. 122 Patentee before: Wuhan University of Technology |