CN101539438B - Fiber grating sensing demodulation method and devices based on microwave photon filters - Google Patents
Fiber grating sensing demodulation method and devices based on microwave photon filters Download PDFInfo
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- CN101539438B CN101539438B CN2009100978719A CN200910097871A CN101539438B CN 101539438 B CN101539438 B CN 101539438B CN 2009100978719 A CN2009100978719 A CN 2009100978719A CN 200910097871 A CN200910097871 A CN 200910097871A CN 101539438 B CN101539438 B CN 101539438B
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Abstract
The invention relates to a fiber grating sensing demodulation method and devices based on microwave photon filters. The method converts the wavelength drift quantity of sensing Fiber Bragg Grating into the strength variable quantity of electric signals with specific frequency by utilizing chirped fiber grating unequal-armed Sagnac circular structure and utilizing the filter action of the structure to the electric signals, thus demodulating the wavelength information. The devices for realizing the method comprise a broadband light source, a three-port optical circulator, a sending Fiber Bragg Grating, an electro-optical modulator, an optical fiber amplifier, a Sagnac ring, a photodetector and an electro-dynamometer; two ports of a 3-dB four-port optical fiber coupler are optically connected with the two ends of a linear chirped fiber grating by two-section optical fiber , and the other two ports thereof as used as the input port and the output port of the Sagnac ring. The invention changes the wavelength variable quantity of the fiber grating into the power variable quantity of modulation electric signals, thus implementing power detection to the demodulated electric signals and greatly reducing the cost and complexity of the demodulation system.
Description
Technical field
The invention belongs to the interleaving techniques field that Fibre Optical Sensor and microwave photon are learned, relate to the fiber grating sensing demodulation technology, be specially adapted to the application of the low-cost demodulation scheme of fiber grating demodulation, be specifically related to a kind of employing microwave photon filter, change the wavelength variations of optical fiber grating sensing the size variation of microwave signal into, thus the device that demodulates the method for optic fiber grating wavelength variable quantity and realize this method.
Background technology
Fiber grating is widely used in stress, in temperature and the refractive index sensing system.In the optical fiber grating sensing field, method and low-cost equipment that the development fast demodulation goes out the optic fiber grating wavelength variable quantity have very significant meaning.
Traditional fiber grating demodulation method often adopts the optical filter demodulation method, as tunable F-P filter method, and non-equilibrium M-Z fibre optic interferometer method and coupling raster method etc.These methods or higher to the performance requirement of optical filter, cost is higher; Perhaps need more optical filter, the higher and complex structure of cost, difficult practicability.
Summary of the invention
Purpose of the present invention is exactly at the prior art deficiency, utilization is converted into the optic fiber grating wavelength variable quantity based on Sarnia gram (Sagnac) ring microwave photon filter the intensive quantity of electric signal, a kind of novel optical fiber and optical grating sensing demodulation method has been proposed, realized low cost optic fiber grating wavelength demodulation on a large scale, the device of realizing this method is provided simultaneously.
Method of the present invention may further comprise the steps:
1, wideband light source enters the sensing bragg grating through optical circulator, and after reflection, to enter in the electrooptic modulator (EOM) by frequency be that the electric signal modulation of f is laggard goes in the fiber amplifier to amplify; The reflection peak of sensing bragg grating is positioned near the centre wavelength of wideband light source;
2, the light after the amplification enters Sarnia gram ring; Sarnia gram ring comprises 3-dB four fiber port coupling mechanism and linear chirp optical fiber gratings, described linear chirp optical fiber grating is the optical fibre device of the index modulation that writes by ultraviolet light in optical fiber, at the diverse location reflection different wave length of linear chirp optical fiber grating, the length of light Sarnia gram ring two arms is respectively L
1And L
2Light after the amplification is divided into two-way after entering Sarnia gram ring by the input port of 3-dB four fiber port coupling mechanisms, enters two arms of Sarnia gram ring respectively;
3, the light of two arms that enters Sarnia gram ring through the linear chirp optical fiber grating reflection after, the output port output from four port 3-dB fiber couplers enters photodetector, changing into power is P
eElectric signal,
P
e＝p
0[1+mcos(Δφ/2)sin(2πft+φ
0)]
P wherein
0Be the power that broadband light reflects through the sensing bragg grating, m is the depth of modulation of electrooptic modulator, φ
0Be the phase place of photodetector output electric signal, Δ φ is the phase differential of the signal after modulating through Sarnia gram ring two arms,
Δφ＝4πf·n
eff·(L
1-L
2+2z-l)/c
N wherein
EffBe optical fibre refractivity, c is a light transmitting speed in a vacuum, and l is the length of linear chirp optical fiber grating, and z is the position that reflection takes place in linear chirp optical fiber grating light, by the wavelength decision of sensing bragg grating; For the electric signal of selected frequency, the electric signal power that detects on photodetector is relevant with the phase differential of Sarnia gram ring two arms, and is promptly relevant in the position of linear chirp optical fiber grating reflection with light modulated;
4, the electric signal that photodetector is obtained inserts electrodymamometer, and the read-out power size can obtain the wavelength of sensor fibre grating.
The device of realizing said method is: wideband light source is connected with the first port light of three ports light rings, second port of three ports light rings is connected with an end light of sensing bragg grating, the 3rd port of three ports light rings is connected with the input end light of electrooptic modulator, the output terminal of electrooptic modulator is connected with the input end light of fiber amplifier, the electricity of electrooptic modulator drives mouth and is electrically connected with signal source, the output terminal of fiber amplifier is connected with the input port light of Sarnia gram ring, the output port of Sarnia gram ring is connected with the input end light of photodetector, and the output terminal of photodetector is electrically connected with the input end of electrodymamometer; Described Sarnia gram ring comprises 3-dB four fiber port coupling mechanism and linear chirp optical fiber gratings, the two ends of linear chirp optical fiber grating are connected with two output port light of 3-dB four fiber port coupling mechanisms by two sections optical fiber respectively, two input port and output ports that port encircles as the Sarnia gram respectively in addition of 3-dB four fiber port coupling mechanisms.
Among the present invention, adopt chirped fiber grating unequal arm Sarnia gram ring structure, utilize its filter action, the wavelength shift of sensing bragg grating is converted to the Strength Changes amount of this characteristic frequency electric signal, thereby the wavelength information demodulation is come out the electric signal of certain frequency.The Sarnia gram encircles temperature variation, mechanical vibration etc. to external world and disturbs insensitive, this demodulation method is than traditional demodulation scheme simultaneously, the wavelength variable quantity of fiber grating is converted into the power variation of modulation signal, thereby the electric signal to modulation carries out power detection, because required electric signal process chip is comparatively ripe, thereby greatly reduce the cost and the complexity of demodulating system.
Description of drawings
Fig. 1 is a structural representation of the present invention.
Embodiment
As shown in Figure 1, structure based on the fiber grating sensing demodulation device of microwave photon filter is: wideband light source 1 is connected with the first port light of three ports light rings 2, second port of three ports light rings 2 is connected with an end light of sensing bragg grating 3, the 3rd port of three ports light rings 2 is connected with the input end light of electrooptic modulator 5, the output terminal of electrooptic modulator 5 is connected with the input end light of fiber amplifier 6, the electricity of electrooptic modulator 5 drives mouth and is electrically connected with signal source 4, the output terminal of fiber amplifier 6 is connected with the input port light of Sarnia gram ring, the output port of Sarnia gram ring is connected with the input end light of photodetector 11, and the output terminal of photodetector 11 is electrically connected with the input end of electrodymamometer 12; Described Sarnia gram ring comprises 3-dB four fiber port coupling mechanisms 7 and linear chirp optical fiber grating 10, the two ends of linear chirp optical fiber grating 10 are connected with two output port light of 3-dB four fiber port coupling mechanisms 7 with 9 by two sections optical fiber 8 respectively, two input port and output ports that port encircles as the Sarnia gram respectively in addition of 3-dB four fiber port coupling mechanisms 10.
Concrete detection method may further comprise the steps:
Wideband light source enters the sensing bragg grating through optical circulator, and after reflection, to enter in the electrooptic modulator (EOM) by frequency be that the electric signal modulation of f is laggard goes in the fiber amplifier to amplify; The reflection peak of sensing bragg grating is positioned near the centre wavelength of wideband light source;
Light after the amplification enters Sarnia gram ring; Sarnia gram ring comprises 3-dB four fiber port coupling mechanism and linear chirp optical fiber gratings, described linear chirp optical fiber grating is the optical fibre device of the index modulation that writes by ultraviolet light in optical fiber, at the diverse location reflection different wave length of linear chirp optical fiber grating, the length of light Sarnia gram ring two arms is respectively L
1And L
2Light after the amplification is divided into two-way after entering Sarnia gram ring by the input port of 3-dB four fiber port coupling mechanisms, enters two arms of Sarnia gram ring respectively;
The light of two arms that enters Sarnia gram ring through the linear chirp optical fiber grating reflection after, the output port output from four port 3-dB fiber couplers enters photodetector, changing into power is P
eElectric signal,
P
e＝P
0[1+mcos(Δφ/2)sin(2πft+φ
0)] (1)
P wherein
0Be the power that broadband light reflects through the sensing bragg grating, m is the depth of modulation of electrooptic modulator, φ
0Be the phase place of photodetector output electric signal, Δ φ is the phase differential of the signal after modulating through Sarnia gram ring two arms,
Δφ＝4πf·n
eff·(L
1-l
2+2z-l)/c (2)
N wherein
EffBe optical fibre refractivity, c is a light transmitting speed in a vacuum, and l is the length of linear chirp optical fiber grating, and z is the position that reflection takes place in linear chirp optical fiber grating light, by the wavelength decision of sensing bragg grating; For the electric signal of selected frequency, the electric signal power that detects on photodetector is relevant with the phase differential of Sarnia gram ring two arms, and is promptly relevant in the position of linear chirp optical fiber grating reflection with light modulated;
The electric signal that photodetector is obtained inserts electrodymamometer, and the read-out power size can obtain the wavelength of sensor fibre grating.
Claims (1)
1. fiber grating sensing demodulation method based on microwave photon filter is characterized in that this method may further comprise the steps:
Step (1) wideband light source enters the sensing bragg grating through optical circulator, and after reflection, to enter in the electrooptic modulator by frequency be that the electric signal modulation of f is laggard goes in the fiber amplifier to amplify; The reflection peak of sensing bragg grating is positioned near the centre wavelength of wideband light source;
Light after step (2) is amplified enters Sarnia gram ring; Sarnia gram ring comprises 3-dB four fiber port coupling mechanism and linear chirp optical fiber gratings, described linear chirp optical fiber grating is the optical fibre device of the index modulation that writes by ultraviolet light in optical fiber, at the diverse location reflection different wave length of linear chirp optical fiber grating, the length of light Sarnia gram ring two arms is respectively L
1And L
2Light after the amplification is divided into two-way after entering Sarnia gram ring by the input port of 3-dB four fiber port coupling mechanisms, enters two arms of Sarnia gram ring respectively;
The light of two arms that step (3) enters Sarnia gram ring through the linear chirp optical fiber grating reflection after, the output port output from four port 3-dB fiber couplers enters photodetector, changing into power is P
eElectric signal,
P
e＝P
0[1+mcos(Δφ/2)sin(2πft+φ
0)]
P wherein
0Be the power that broadband light reflects through the sensing bragg grating, m is the depth of modulation of electrooptic modulator, φ
0Be the phase place of photodetector output electric signal, Δ φ is the phase differential of the signal after modulating through Sarnia gram ring two arms,
Δφ＝4πf·n
eff·(L
1-L
2+2z-l)/c
N wherein
EffBe optical fibre refractivity, c is a light transmitting speed in a vacuum, and l is the length of linear chirp optical fiber grating, and z is the position that reflection takes place in linear chirp optical fiber grating light, by the wavelength decision of sensing bragg grating; For the electric signal of selected frequency, the electric signal power that detects on photodetector is relevant with the phase differential of Sarnia gram ring two arms, and is promptly relevant in the position of linear chirp optical fiber grating reflection with light modulated;
Step (4) inserts electrodymamometer with the electric signal that photodetector obtains, and the read-out power size can obtain the wavelength of sensor fibre grating.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102141691A (en) * | 2011-04-25 | 2011-08-03 | 东北大学 | Magnetic control tunable optical fiber comb filter |
| CN103018838B (en) * | 2012-12-07 | 2016-03-02 | 南京邮电大学 | Wide-band tuning high q-factor single-pass band microwave photon filter |
| CN103776475A (en) * | 2014-01-28 | 2014-05-07 | 浙江大学 | Optical fiber sensor and sensing method based on linear filter and photoelectric detector |
| CN104568219A (en) * | 2015-01-15 | 2015-04-29 | 厦门大学 | Temperature measurement device and method based on single-passband microwave photon filter |
| CN109004983B (en) * | 2018-06-21 | 2021-06-18 | 上海第二工业大学 | Accurate sensing method based on phase-to-intensity modulation conversion principle |
| CN109520533A (en) * | 2019-01-23 | 2019-03-26 | 国网江西省电力有限公司信息通信分公司 | Fiber grating demodulation device and method based on fiber optic loop microwave photon filter |
| CN113438026B (en) * | 2021-06-24 | 2022-10-18 | 中国科学院半导体研究所 | Optical frequency hopping communication system based on optical fiber Bragg grating |
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