CN102353394A - Time division multiplexing (TDM)-based low-reflectivity triangle spectrum-shaped fiber grating sensing system - Google Patents
Time division multiplexing (TDM)-based low-reflectivity triangle spectrum-shaped fiber grating sensing system Download PDFInfo
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Abstract
The invention discloses a time division multiplexing (TDM)-based low-reflectivity triangle spectrum-shaped fiber grating sensing system. The system mainly comprises a distribution feedback laser, an electro-optical modulator, a circulator, an optical amplifier, a triangle spectrum-shaped fiber grating sensor, a high-speed optical detector, a pulse signal generator and a signal acquisition device, wherein the distribution feedback laser is used for emitting narrow line-width laser; pulse signal light is formed by the narrow line-width laser through the electro-optical modulator or is generated by internal modulation through the distribution feedback laser; the pulse light passes through the circulator and then is reflected by a triangle spectrum-shaped fiber grating; the reflected light passes through the circulator to enter the optical amplifier and is amplified into the high-speed optical detector; and a light signal is converted into an electrical signal through the high-speed optical detector, and the electrical signal is converted into a digital signal and is processed through the signal acquisition device. In the system, the distribution feedback laser and the low-reflectivity triangle spectrum-shaped fiber grating sensor are combined, a large-scale fiber grating sensing network is constructed through TDM, and thousands of sensors are multiplexed on a single fiber, so that the costs of a light source and a wavelength detection device are reduced.
Description
Technical field
The invention belongs to sensory field of optic fibre, particularly a kind of large-capacity fiber grating sensing system and construction method thereof.
Background technology
Fibre Optical Sensor is to be accompanied by the development of optical fiber communication and one type of novel sensing technology rising, is the important component part of technology of Internet of things.Optical fiber sensing technology have anti-electromagnetic interference (EMI), long-time stability good, collect sensing and be transmitted as the advantage of many uniquenesses such as one, size be little, in light weight, be widely applied to a plurality of fields such as building, electric power, petrochemical industry, traffic.Wherein, optical fiber grating sensing is to be studied and to use one of maximum technology at present.Except characteristics with general Fibre Optical Sensor; Fiber grating sensing system also has the characteristics of Wavelength-encoding; The measuring method that it adopts the monitoring wavelength signals to change; Can effectively avoid of the influence of external interference such as light source fluctuation, have high measuring accuracy and antijamming capability measurement result.
The typical optical fiber grating sensing system is as shown in Figure 1.It is made up of wideband light source 1, photo-coupler 2, fiber-optic grating sensor 3, wavelengt demodulator 4, data handling system 5, adopts the multiplex mode of wavelength-division multiplex.Broadband light is sent by light source 1, and by fiber-optic grating sensor 3 reflections, reflected light is received and detects by wavelengt demodulator 4, and gives controlling computer with structural transmission behind photo-coupler 2.If (for example temperature, pressure etc.) to be measured changes, the reflection wavelength of fiber-optic grating sensor 3 also changes thereupon, and this variation is detected by wavelengt demodulator 4, and data transmission is carried out data analysis and processing to data handling system 5.In order to tell the signal that each fiber-optic grating sensor reflects, the reflection wavelength of each fiber-optic grating sensor is all inequality in this system, and in order to stay certain space to wavelength change, the reflection wavelength of fiber-optic grating sensor differs about 2nm.Because the restriction of light source bandwidth, the quantity of this system's ability receiving optical fiber grating sensor has only dozens of.When adopting optical fiber grating sensing network that facilities such as bridge, tunnel, oil depot are monitored, the monitoring that needs is counted often has hundreds and thousands of, and traditional fiber grating sensing system can not meet the demands.
Therefore, the large-capacity fiber grating sensing technology has huge meaning and value to improving system effectiveness, it has been carried out extensive studies both at home and abroad.Existing certain methods is used for realizing improving the capacity of fiber grating sensing system; For example: Yu Youlong etc. are at " active ripple, space division multiplexing optical fiber grating sensing network " (Chinese laser; 2001,29 (2), pp.131-134) article; Propose to use 1 * 3 photoswitch to carry out space division multiplexing, can bring up to original 3 times to power system capacity.
Chan; People such as P.K.C are at " FMCW multiplexing of fiber bragg grating sensors " (Selected topics in quantum electronics; IEEE Journal of; 2000,6 (5): 756-763.) proposition makes the capacity of system can reach hundreds of with the Wavelength demodulation of the technology realization fiber grating of continuous wave frequency in the literary composition.
Yu Youlong etc. are in " the fiber grating sensing system time domain address lookup technology of high resolving power single channel output " (optics journal .2001,21 (7): 874-877) propose time-multiplexed mode in the article and carry out multiplexing.
In these methods, the power system capacity that space division multiplexing method can improve is limited, and is limited by the serviceable life of light shutter device, and application is restricted; Time-division multiplex technology can significantly improve power system capacity, but needs to adopt high-power wideband light source, costs an arm and a leg, and is difficult in actual engineering, use.
Summary of the invention
The objective of the invention is to design a kind of high capacity, fiber grating sensing system cheaply, promptly based on time-multiplexed antiradar reflectivity three angular spectrum shape fiber grating sensing systems.Native system adopts the multiplexing method that wavelength-division and time-division combine, with antiradar reflectivity three angular spectrum shape fiber gratings as senser element, make can be multiplexing on the simple optical fiber fiber-optic grating sensor quantity can reach thousands of individual.Do not adopt the wideband light source in the traditional fiber grating sensing system in this method; But used common distributed feed-back (DFB) laser instrument as system source; There are not tunable optic filter, non-equilibrium Mach-Zehnder interferometer equiwavelength demodulation device yet; Simplify system architecture greatly, reduced system cost.
Technical scheme of the present invention:, mainly form by distributed feed-back (DFB) laser instrument, electrooptic modulator, circulator, image intensifer, three angular spectrum shape fiber-optic grating sensors, high speed photodetector, pulse signal generator and signal pickup assembly based on time-multiplexed antiradar reflectivity three angular spectrum shape fiber grating sensing systems (referring to Fig. 2); DFB laser sends narrow-linewidth laser, through forming pulse light behind the electrooptic modulator, and this pulsed light or produce through internal modulation by DFB laser; Pulsed light is reflected by three angular spectrum shape fiber-optic grating sensors through behind the circulator; Reflected light arrives image intensifer through circulator; Arrive high speed photodetector through amplifying the back; Light signal is converted to electric signal by high speed photodetector, and is converted to digital signal and carry out signal Processing by signal pickup assembly.
In the system of the present invention; Three angular spectrum shape fiber gratings as sensor adopt identical technological parameter in manufacturing process; Therefore has identical spectral response; And through the control of the exposure in manufacturing process, make its reflectivity perhaps lower about 0.1%, generally adopt 0.05% reflectivity in use.The spectral response figure of one three angular spectrum shape fiber grating instance is as shown in Figure 3, and its reflection wavelength can be selected other wavelength as required in practical application near 1556nm.
In the system of the present invention, DFB laser sends narrow-linewidth laser, and its wavelength is in the centre position, the range of linearity of three angular spectrum shapes of three angular spectrum shape fiber-optic grating sensors.Through behind the electrooptic modulator, be modulated into pulse signal, pulse width is generally 10～50ns by the deration of signal decision of pulse signal generator.
In the process that pulsed light is reflected by three angular spectrum shape fiber gratings; Because the reflectivity of three angular spectrum shape fiber gratings is very low; Therefore; Even hundreds and thousands of three angular spectrum shape fiber-optic grating sensors of serial connection on the simple optical fiber, high speed photodetector also can be received three angular spectrum shape fiber-optic grating sensor reflected signals of least significant end.Two 10 meters at adjacent three angular spectrum shape fiber-optic grating sensors intervals are perhaps farther; This has guaranteed that the pulsed light that reflects back from each three angular spectrum shape fiber-optic grating sensor can be by a delay inequality; The time of the light pulse of returning through detection of reflected, can know this light pulse is by which three angular spectrum shape fiber gratings reflection.
When measured physical quantity changes; Can have influence on the reflection wavelength of certain three angular spectrum shape fiber-optic grating sensor; After its spectral response perhaps moves right left; The reflected impulse light intensity can become big accordingly or diminish, and through detecting the Strength Changes of this pulsed light, just can calculate the variation of measured physical quantity.
Advantage of the present invention is: through the combination of distributed feed-back (DFB) laser instrument and antiradar reflectivity three angular spectrum shape fiber-optic grating sensors; Can make up large-scale optical fiber grating sensing network through time-multiplexed mode; Multiplexing number of sensors can reach thousands of on the simple optical fiber, and greatly reduces the cost of light source and wavelength pick-up unit.
Description of drawings
Fig. 1: typical optical fiber grating sensing system synoptic diagram
Fig. 2: based on time-multiplexed antiradar reflectivity three angular spectrum shape fiber grating sensing system synoptic diagram
Fig. 3: the spectral response figure of one three angular spectrum shape fiber-optic grating sensor instance
Among the figure: 1, wideband light source 2, photo-coupler 3, fiber-optic grating sensor 4, wavelengt demodulator 5, data handling system 6, distributed feed-back (DFB) laser instrument 7, electrooptic modulator 8, circulator 9, image intensifer 10, three angular spectrum shape fiber-optic grating sensors 11, high speed photodetector 12, pulse signal generator 13, signal pickup assembly.
Embodiment
A kind of embodiment of the present invention is as shown in Figure 2.Based on time-multiplexed antiradar reflectivity three angular spectrum shape fiber grating sensing systems, mainly form by DFB laser 6, electrooptic modulator 7, circulator 8, image intensifer 9, three angular spectrum shape fiber-optic grating sensors 10, high speed photodetector 11, pulse signal generator 12, signal pickup assembly 13 etc.
Fiber-optic grating sensor is to adopt excimer laser to obtain through the method for uv-exposure; Among the spectral response figure of three angular spectrum shape fiber-optic grating sensors shown in Figure 3; The spectral shape of this sensor is a triangle; Be owing to employing chirped fiber grating phase mask plate, and obtain through the method for non-homogeneous exposure.In the system each three angular spectrum shape fiber-optic grating sensors adopt identical technological parameter in manufacturing process; Therefore has identical spectral response; And through the control of the exposure in manufacturing process; Make its reflectivity perhaps lower about 0.1%, we generally adopt 0.05% reflectivity in use.The reflection wavelength of three angular spectrum shape fiber-optic grating sensors among Fig. 3 can be selected other wavelength as required in practical application near 1556nm.
Minor increment L between two adjacent three angular spectrum shape fiber-optic grating sensors is by the pulse width decision of signal generator.If the pulse width that signal generator sends is t, the effective refractive index of optical fiber is n, and the light light velocity in a vacuum is c, then must satisfy between them:
Thereby guarantee that the pulse signal that each triangular wave Bragg grating sensor reflects can be not overlapping.
DFB laser 6 sends narrow-linewidth laser, and its wavelength should be in the centre position, the range of linearity of three angular spectrum shapes of three angular spectrum shape fiber-optic grating sensors 10.Through behind the electrooptic modulator 7, be modulated into pulse signal, pulse width is generally 10～50ns by the deration of signal decision of pulse signal generator 12.Pulse light also can be produced through internal modulation by DFB laser 6.Pulsed light is reflected by three angular spectrum shape fiber-optic grating sensors 10 through circulator 8 backs, and then arrives high speed photodetectors 11 through circulator 8.The delay inequality that the light pulse of adjacent two three angular spectrum shape fiber-optic grating sensors reflection arrives high speed photodetector is 2nL/c.
The light signal of three angular spectrum shape fiber-optic grating sensors, 10 reflections is converted to electric signal by high speed photodetector 11, and is converted to digital signal and carry out signal Processing by signal pickup assembly 13.Because the spectral shape of three angular spectrum shape fiber-optic grating sensors is a triangle, its reflectivity is relevant with wavelength.If its reflectivity to wavelength X is R, work as sensor so and receive ectocine, behind the wavelength change Δ λ, its reflectivity becomes R ':
R′＝R+k·Δλ (2)
Wherein k is the slope of three angular spectrum shapes.Accordingly, if the light pulse intensity before the reflection is I, then photo-detector receives that light intensity also becomes IR ' by original IR.The light intensity that receives through photo-detector changes, and just can extrapolate variation to be measured.
Claims (3)
1. based on time-multiplexed antiradar reflectivity three angular spectrum shape fiber grating sensing systems, it is characterized in that: this system comprises DFB laser (6), electrooptic modulator (7), circulator (8), image intensifer (9), three angular spectrum shape fiber-optic grating sensors (10), high speed photodetector (11), pulse signal generator (12) and signal pickup assembly (13); DFB laser (6) sends narrow-linewidth laser, forms pulse light through electrooptic modulator (7) back, this pulsed light or produced through internal modulation by DFB laser (6); Pulsed light is reflected by three angular spectrum shape fiber-optic grating sensors (10) through circulator (8) back; Reflected light arrives image intensifer (9) through circulator (8); Arrive high speed photodetector (11) through amplifying the back; Light signal is converted to electric signal by high speed photodetector (11), and is converted to digital signal and carry out signal Processing by signal pickup assembly (13).
2. according to claim 1 based on time-multiplexed antiradar reflectivity three angular spectrum shape fiber grating sensing systems, it is characterized in that: the wavelength of DFB laser (6) is in the centre position, the three angular spectrum shape ranges of linearity of three angular spectrum shape fiber-optic grating sensors (10).
3. according to claim 1 based on time-multiplexed antiradar reflectivity three angular spectrum shape fiber grating sensing systems, it is characterized in that: two 10 meters at adjacent three angular spectrum shape fiber-optic grating sensors (10) intervals are perhaps farther.
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| CN103954307A (en) * | 2014-04-29 | 2014-07-30 | 中国人民解放军海军工程大学 | Optical fiber laser sensor time division and wavelength division combined multiplexing method |
| CN104181635A (en) * | 2014-08-15 | 2014-12-03 | 山东省科学院激光研究所 | Intensity distribution type demodulation system and distribution type sensing optical fiber |
| CN105553557A (en) * | 2015-12-16 | 2016-05-04 | 华进半导体封装先导技术研发中心有限公司 | Optical receiving unit structure for optical fiber communication |
| CN106066203A (en) * | 2016-05-25 | 2016-11-02 | 武汉理工大学 | Distributed highly sensitive vibration-detection system based on ultrashort optical fiber optical grating array and method |
| CN107478577A (en) * | 2017-08-08 | 2017-12-15 | 江苏中能光电技术有限公司 | Multiplexing fiber-optic gas sensing system based on weak optical fiber Bragg grating and optical time domain reflectometer |
| CN108267160A (en) * | 2017-12-28 | 2018-07-10 | 博立信（北京）科技有限公司 | Time-multiplexed fiber Bragg grating sensor |
| CN108508097A (en) * | 2017-02-28 | 2018-09-07 | 香港理工大学 | A kind of rail crack monitoring system based on fiber ultrasonic guided wave technology |
| CN109579887A (en) * | 2018-12-04 | 2019-04-05 | 上海第二工业大学 | A kind of time division multiplex optical fiber grating sensing system and method based on composite coding |
| CN111812036A (en) * | 2020-07-17 | 2020-10-23 | 宝宇(武汉)激光技术有限公司 | Time division multiplexing ultrasonic detection network |
| GB2596257A (en) * | 2015-03-06 | 2021-12-22 | Silixa Ltd | Method and apparatus for optical sensing |
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Cited By (17)
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| CN103954307B (en) * | 2014-04-29 | 2016-09-21 | 中国人民解放军海军工程大学 | Fiber laser sensor time-division, wavelength-division associating multiplexing method |
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| GB2596257A (en) * | 2015-03-06 | 2021-12-22 | Silixa Ltd | Method and apparatus for optical sensing |
| US11719560B2 (en) | 2015-03-06 | 2023-08-08 | Silixa Ltd. | Method and apparatus for optical sensing |
| GB2598697B (en) * | 2015-03-06 | 2022-07-06 | Silixa Ltd | Method and apparatus for optical sensing |
| GB2596257B (en) * | 2015-03-06 | 2022-06-08 | Silixa Ltd | Method and apparatus for optical sensing |
| GB2598697A (en) * | 2015-03-06 | 2022-03-09 | Silixa Ltd | Method and apparatus for optical sensing |
| CN105553557A (en) * | 2015-12-16 | 2016-05-04 | 华进半导体封装先导技术研发中心有限公司 | Optical receiving unit structure for optical fiber communication |
| CN106066203A (en) * | 2016-05-25 | 2016-11-02 | 武汉理工大学 | Distributed highly sensitive vibration-detection system based on ultrashort optical fiber optical grating array and method |
| CN106066203B (en) * | 2016-05-25 | 2019-01-29 | 武汉理工大学 | The highly sensitive vibration-detection system of distribution and method based on ultrashort optical fiber optical grating array |
| CN108508097B (en) * | 2017-02-28 | 2021-03-02 | 香港理工大学 | Rail crack monitoring system based on optical fiber ultrasonic guided wave technology |
| CN108508097A (en) * | 2017-02-28 | 2018-09-07 | 香港理工大学 | A kind of rail crack monitoring system based on fiber ultrasonic guided wave technology |
| CN107478577A (en) * | 2017-08-08 | 2017-12-15 | 江苏中能光电技术有限公司 | Multiplexing fiber-optic gas sensing system based on weak optical fiber Bragg grating and optical time domain reflectometer |
| CN108267160A (en) * | 2017-12-28 | 2018-07-10 | 博立信（北京）科技有限公司 | Time-multiplexed fiber Bragg grating sensor |
| CN109579887A (en) * | 2018-12-04 | 2019-04-05 | 上海第二工业大学 | A kind of time division multiplex optical fiber grating sensing system and method based on composite coding |
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Application publication date: 20120215 |