Distributed Fiber-Optic Intrusion Sensor System
Juan C.Juarez ,Member,IEEE ,Eric W.Maier,Kyoo Nam Choi ,Member,IEEE ,and
Henry F.Taylor ,Fellow,IEEE,Fellow,OSA
Abstract—A distributed sensor system for detecting and lo-cating intruders based on the phase-sensitive optical-time-domain re?ectometer (-OTDR)is described.The sensing element is a cabled single-mode telecommunications ?ber buried along the monitored perimeter.Light pulses from a continuous-wave Er:?ber Fabry–Pérot laser with a narrow
(3kHz)instantaneous linewidth and low (few kilohertz per second)frequency drift are injected into one end of the ?ber,and the backscattered light is monitored with a photodetector.The effect of phase changes resulting from the pressure of the intruder on the ground immedi-ately above the buried ?ber are sensed by subtracting a -OTDR trace from an earlier stored trace.In laboratory tests with ?ber on reels,the effects of localized phase perturbations induced by a piezoelectric ?ber stretcher on -OTDR traces were observed.In ?eld tests,people walking on the ground above a buried ?ber cable induced phase shifts of
several-radians.
Index Terms—Distributed sensor,Er:?ber laser,?ber sensor,in-trusion sensor,optical-phase sensor,optical-time-domain re?ec-tometer (OTDR),perimeter security.
I.I NTRODUCTION
T
HE optical-time-domain re?ectometer (OTDR),initially demonstrated over two decades ago [1]–[3],is now widely used for locating breaks and other anomalies in ?ber-optic links and networks.In an OTDR system,light pulses from a semicon-ductor laser are injected into one end of a ?ber,and Rayleigh-backscattered light returned from the ?ber is monitored with a photodetector.The system detects the presence and location of perturbations that affect the intensity of the light returned from the ?ber but does not in general respond to the phase modulation of the light.The spectral width of the modulated laser is very broad (gigahertz to terahertz range)so that ?uctuations in the return signal due to interference of backscattered components from different parts of the ?ber are,for the most part,avoided.When present to a noticeable extent,coherent effects represent an undesirable source of noise in an OTDR trace.
The distributed sensor described in this paper utilizes a phase-sensitive OTDR
(-OTDR)system designed to enhance coherent effects rather than avoid them [4].Phase sensitivity
Manuscript received September 10,2004;revised January 25,2005.
J.C.Juarez is with the Department of Electrical Engineering,Texas A&M University,College Station,TX 77843-3128USA (e-mail:jcj@https://www.doczj.com/doc/a27207104.html,).E.W.Maier was with the Department of Electrical Engineering,Texas A&M University,College Station,TX 77843-3128,USA.He is now with the Mission Operations Directorate,Flight Control,National Aeronautics and Space Administration (NASA),Houston,TX 77058USA (e-mail:eric.maier1@https://www.doczj.com/doc/a27207104.html,).
K.N.Choi is with the Department of Communication Engineering,Incheon City College,Incheon 402-750,South Korea (e-mail:knchoi@icc.ac.kr).
H. F.Taylor is with the Department of Electrical Engineering,Texas A&M University,College Station,TX 77843-3128USA (e-mail:taylor@https://www.doczj.com/doc/a27207104.html,).
Digital Object Identi?er 10.1109/JLT.2005.849924
results from interference of the light backscattered from dif-ferent parts of the ?ber,which arrive simultaneously at the photodetector.As a practical matter,
the -OTDR can detect perturbations much too small to be perceived with a conven-tional OTDR system.
In prior research,
the -OTDR has been applied with both pulsed and continuous-wave (CW)laser light sources to de-tect and determine the location of phase perturbations caused by stretching or heating optical ?bers.A repetitively
pulsed -switched yttrium aluminum garnet laser was the light source in a system for observing a piezoelectrically induced length change,and a pulsed semiconductor laser was used in the detec-tion of a rapidly increasing temperature [5].A single-frequency CW semiconductor laser in conjunction with an external acous-tooptic modulator was used to sense a localized thermal per-turbation [6],[7],and an Er:?ber laser,in combination with an electrooptic modulator,was applied to observe a piezoelectri-cally induced length change [8].
Other distributed sensors applicable for intrusion sensing are based on the Sagnac interferometer.The ?rst reported was a two-interferometer con?guration incorporating a Mach–Zehnder to measure the phase-change rate with the Sagnac interferometer to detect nonreciprocal phase pertur-bances [9].Modi?ed versions have been proposed to eliminate the position sensitivity of the Sagnac interferometer with a phase shifter or the need for a highly coherent light source with wavelength-division-multiplexing (WDM)techniques [10].A frequency modulation CW technique was applied to a birefringent Sagnac loop to use the intensity and fre-quency of a beat signal produced by two forward-coupled mode beams to determine the amplitude and location of an applied stress,respectively [11].A dual-wavelength,merged Sagnac and Michelson interferometer system has been pro-posed with a broad-band source for optimal operation of the Sagnac [12].Two-loop and variable-loop Sagnac interferometer systems have been investigated to preserve the inherent insen-sitivity to reciprocal disturbances of the Sagnac [13],[14].A single-source,single-detector WDM system incorporating dual 40-km Sagnac loops has been applied with real-time location of multiple time-varying disturbances [15].
In the distributed intrusion sensor reported here,the phase changes of interest result from the pressure of an intruder on the ground above the buried ?ber cable [4],[16],as illustrated in Fig.1.Light pulses from a CW laser are gated into one end of the ?ber via a pulsed intensity modulator,and the backscat-tered light from the ?ber is monitored with a photodetector.As with the conventional OTDR,
the -OTDR trace is a plot of re-turned optical power versus time.When the sensing ?ber and light source are stabilized,the resulting trace exhibits a unique
0733-8724/$20.00?2005IEEE
Fig.1.Phase-sensitive OTDR ( -OTDR)used for intrusion sensing.
temporal signature characteristic of the state of the sensor.The effect of phase changes resulting from the pressure of a person on the ground immediately above or near the buried ?ber are sensed by subtracting
a -OTDR trace from an earlier stored trace.The time at which changes in
the -OTDR trace occur are proportional to the range (distance along the ?ber from the proximal end)at which the phase perturbation is applied.The
spatial
resolution
of the sensor is determined by the width of the
pulses ,gated into the ?ber such
that
,
where is the speed of light in a vacuum
and is the group refractive index [17].
In contrast to the conventional OTDR,
the -OTDR used for intrusion sensing requires a laser with minimal frequency drift as well as narrow instantaneous linewidth.Low frequency drift is critical because frequency modulation of the laser causes trace-to-trace ?uctuations in
the -OTDR waveform—a source of noise that obscures the effect of an intruder.The Er:?ber laser was selected for this application because it emits in the spectral region where silica ?ber losses are a minimum,it can be used with Er:?ber ampli?ers to achieve high average and pulsed power levels,and it can emit in a single longitudinal mode for narrow-linewidth operation [8].
This paper describes the laboratory characterization of
a -OTDR system,followed by ?eld testing of an intrusion sensing system using a buried cable.In laboratory experiments with ?ber on reels,the effects of controlled phase perturbations induced by a piezoelectric ?ber stretcher
on -OTDR traces were characterized.In ?eld tests with intruders walking on the ground over a buried ?ber cable,phase shifts of
several-radians were observed.
II.E R :F IBER L ASER
The experimental setup for the light source,which utilizes all single-mode ?ber paths,is shown in Fig.2.The Fabry–Pérot cavity is formed by two ?ber Bragg grating (FBG)re?ectors with an identical re?ectance peak wavelengths of 1555.4
nm
Fig.2.Experimental setup for ?ber laser used as the light source in the intrusion sensor
system.
Fig.3.Delayed self-heterodyne measurement of laser linewidth using a 63-km optical delay line.
and spectral widths of 0.4nm.The FBG re?ectances are 99.9%(back side)and 92%(output side).The 3-m-long
Er -doped ?ber gain medium is pumped by a 980-nm semiconductor laser diode (LD)via a WDM coupler.An optical feedback loop cou-pled to the laser cavity via two 90/10directional couplers (DCs)was added to improve the spectral characteristics of the laser [8].Optical isolators ensure unidirectional propagation in the feed-back loop and suppress coupling of the laser emission back into the cavity.The laser is housed in a thermally insulated enclosure,as a constant temperature environment is essential to achieving a stable single-mode lasing spectrum with low frequency drift.The optical output power from this laser is about
50W,and the emission wavelength of 1555.4nm measured with an op-tical spectrum analyzer corresponds to the re?ectance peak of the FBGs.
A delayed self-heterodyne setup consisting of a ?ber Mach–Zehnder interferometer (MZI)with a 63-km delay line in one arm was used for the instantaneous linewidth mea-surement [18],[19].An electrooptic modulator driven by a sinusoidal voltage shifts the center frequency of the correlated signal to 100kHz.As shown in Fig.3,the laser exhibits a resolution-limited spectral width
of 3kHz.Such narrow spectral widths,indicative of single longitudinal mode opera-tion,are frequently seen in these Er:?ber lasers [20]–[22].The selection of a single longitudinal mode probably results from
JUAREZ et al.:DISTRIBUTED FIBER-OPTIC INTRUSION SENSOR SYSTEM
2083
Fig.4.Monitoring the laser frequency drift with two MZIs.
the formation of an intracavity refractive index grating due to spatial hole burning in the Er-doped ?ber.
The rate of frequency drift was determined by observing tem-poral fringes in a pair of unbalanced ?ber MZIs with path length differences of 200m,as illustrated in Fig.4.Each of the MZIs was insulated from thermal and acoustic effects with multiple layers of foam board and shredded Styrofoam.The use of two individually packaged and physically separated MZIs to simul-taneously monitor the laser reduces the uncertainty as to the origin of the observed temporal fringes.Although well insu-lated,the two MZIs are themselves still affected to some extent by environmental perturbations.
Temporal fringes in an MZI output result from a frequency
drift
in the laser,which results in a phase shift
of
with being the time-delay difference in the interferom-eter.In the present
case,
1s so that one fringe
(radian phase shift)corresponds to a 1-MHz frequency change.
Insulating the MZIs signi?cantly reduced environmental effects from affecting the frequency drift measurements,as shown in Fig.5.This is inferred because the fringes have a constant phase relative to each other,thus implying that the frequency drift measurements are due to the laser.When the ambient temperature change was relatively rapid,a frequency drift
of 4–5MHz/min was observed [Fig.5(a)].Under normal laboratory conditions with minimal disturbances,frequency drifts
of 1–1.5MHz/min [Fig.5(b)]were routinely measured.Under the quietest of conditions,frequency drifts in the order of 100–300kHz/min were observed [Fig.5(c)].The MZIs were stable enough to detect when the laser hopped modes,as seen by the momentary phase shifts in Fig.4(a)and (c),which were captured simultaneously by both MZIs.
III.OTDR L ABORATORY S IMULATION
The performance of
the -OTDR was tested in a laboratory setting with the arrangement of Fig.6.Light from the CW laser passed through a bandpass ?lter (BPF),consisting of an FBG with re?ectance peak matched to the lasing wavelength in se-ries with a circulator,to remove spontaneous emission.The light was then ampli?ed by an erbium-doped ?ber ampli?er (EDFA),the output of which was ?ltered by a second BPF identical to the ?rst.Narrow
(10-s)light pulses from the laser were gated into the ?ber with an electrooptic modulator (EOM),ampli?ed with another EDFA,and coupled into the sensing ?ber via a 3-dB ?ber-optic directional coupler (50/50DC).The distributed
in-Fig.5.Frequency drift:(a)environmental disturbances at 2:52:03p.m.;(b)normal laboratory conditions at 8:36:44a.m.;and (c)minimal disturbances at 10:32:04p.m.
trusion sensor was simulated by two thermally insulated spools of single-mode ?ber (2and 10km)with a phase modulator (PZT),consisting of about 10m of ?ber wound on a piezoelec-tric ?ber cylinder,spliced in between them to produce controlled phase changes simulating an intruder.The backscattered light from the sensing ?ber passed through the 50/50DC to an op-tical receiver containing an InGaAs photodiode and a transimpe-dence ampli?er.Data was acquired with a 60-megasamples per
2084JOURNAL OF LIGHTW A VE TECHNOLOGY ,VOL.23,NO.6,JUNE
2005
https://www.doczj.com/doc/a27207104.html,boratory setup for characterizing the -OTDR
system.
Fig.7.Effect of a phase perturbation on successive -OTDR traces.
second (MS/s)Gage data acquisition card and processed with a LabView system.
The EOM was pulsed continuously with a period of
150s,which exceeded the
120-s round-trip time for light propaga-tion in the ?ber so that successive returns did not overlap.The ability to detect phase changes was initially tested by pulsing the PZT element to induce a phase change of
approximately
radians at the 2-km location for every second laser pulse.Fig.7displays two consecutive superimposed traces and the dif-ference between the two traces.The difference waveform peaks at
20s from the start of
the -OTDR trace,corresponding to the round-trip transit time for the 2-km length of ?ber.
In another test of the phase response of the system,ramp volt-ages varying
through
radians were applied to the PZT ele-ment,and the amplitude changes over 64
consecutive -OTDR traces were monitored.Superimposing the traces shows how the phase modulation causes a large change in the envelope at the 2-km location,while the remainder of the trace stays relatively constant [Fig.8(a)].Subtracting these OTDR traces from a ref-erence trace with no applied PZT voltage shows the varying in-tensities more clearly at the 2-km location [Fig.8(b)]with a spa-tial resolution of about 1km due to the
10-s pulses launched into the ?ber.The dependence of the peak amplitude of the dif-ference in these two traces is close to a sinusoidal function of applied phase shift [Fig.8(c)],as expected because of the inter-ferometric nature of
the -OTDR
response.
Fig.8.(a)Consecutive OTDR traces superimposed with phase changes at 2-km location.(b)Differences of OTDR traces superimposed with phase changes at 2-km location.(c)Magnitudes of 2-km location plotted versus applied phase shifter voltage.
IV .I NTRUSION S ENSOR F IELD T ESTS
Field tests to detect and locate intrusions occurring over a buried ?ber-optic cable were performed using the same experi-mental arrangement as in the laboratory experiments described
JUAREZ et al.:DISTRIBUTED FIBER-OPTIC INTRUSION SENSOR SYSTEM
2085
Fig.9.Con?guration of buried
sensor.
Fig.10. -OTDR traces acquired before and after an 80-km person has stepped on the ground above the cable.
previously and illustrated in Fig.6,except that the PZT phase modulator was removed from the system,and in its place was spliced 44m of a 3-mm-diameter single-mode ?ber-optic cable buried at a depth of 20cm in clay soil.The buried cable passed through a conduit installed in the wall of the laboratory building in which the monitoring equipment was housed,as illustrated in Fig.9.
As one illustration of the phase response of the buried
cable,-OTDR traces acquired before and after an 80-kg person has stepped on the ground above the cable,as well as the difference of the two waveforms,are shown in Fig.10.As in the laboratory test,the width of the laser pulse entering the ?ber was
10s.As in the laboratory results of Figs.7and 8,the 2-km range at which the response appears is the distance from the proximal end of the ?ber to the location of the phase change.
The superposition of 200consecutive OTDR traces collected over a time period of 60ms as a person walked back and forth across the buried cable is shown in Fig.11(a).Difference plots generated by subtracting the latest OTDR trace from a running average of the last ten traces show the intrusion effect with greater clarity [Fig.11(b)].Finally,in Fig.12,the temporal dependence of
the -OTDR response shows the effect of phase changes due to individual steps taken by a person walking on the ground above the buried cable.Three steps can be
observed
Fig.11.(a)Superposition of -OTDR traces produced in response to a person walking on the ground above the buried cable.(b)Difference plots of the same
data.
Fig.12.Response of -OTDR over a time period of 2s at ranges of 2,3,and 4km when a person is walking on the ground above the buried ?ber cable at the 2-km location.
in the trace corresponding to a range of 2km,which commence at times of approximately 0.25,0.85,and 1.60s from the
2086JOURNAL OF LIGHTW A VE TECHNOLOGY,VOL.23,NO.6,JUNE2005 beginning of the data record.As expected,the response is only
in evidence at the2-km range,corresponding to the location
of the intruder.For each of the steps,the interference pattern
traverses at least four fringes,corresponding to a phase
shift
radians.
V.C ONCLUSION
A distributed sensor system for detecting and locating
intruders based on the phase-sensitive optical time-domain re-
?ectometer
(-OTDR)has been investigated.The light source
for the system is a continuous-wave(CW)Er:?ber Fabry–P′erot
laser with a narrow
(3kHz)instantaneous linewidth and low
(few kilohertz per second)frequency drift.Phase changes along
the length of the?ber are sensed by subtracting
a-OTDR trace
from an earlier stored trace.In laboratory tests with?ber on
reels,the effects of localized phase perturbations induced by a
piezoelectric?ber stretcher
on-OTDR traces were observed.
In the?rst?eld tests of a system in which the sensing element is
a cabled single-mode?ber buried along a monitored perimeter,
phase shifts of
several-radians produced by people walking
on the ground above the buried cable were observed.Based
on these initial results,this technology may be regarded as a
candidate for providing low-cost perimeter security for nuclear
power plants,electrical power distribution centers,storage
facilities for fuel and volatile chemicals,communication hubs,
airports,government of?ces,military bases,embassies,and
national borders.
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Juan C.Juarez(M’99)was born in Laredo,TX,in
1978.He received the B.S.and M.S.degrees in elec-
trical engineering from Texas A&M University,Col-
lege Station,in2000and2002,respectively.He is
currently working toward the Ph.D.degree in elec-
trical engineering at the same university.
In summer2001,he worked for the Product De-
velopment Group of Corning Cable Systems,where
he tested and developed hardware and software for
a low-cost directional coupler test bench.In summer
2003,he worked in the Nonproliferation and Inter-
national Security Division of Los Alamos National Laboratory,studying ver-
tical-cavity surface-emitting lasers(VCSELs)for use with a quantum key distri-
bution(QKD)system.He currently works as a Research Assistant with the De-
partment of Electrical Engineering at Texas A&M University.His research in-
terests are in the?elds of?ber-optic sensors,?ber lasers,VCSELs,and quantum
encryption systems.
Mr.Juarez is a Member of Tau Beta Pi and served as the Texas Delta Chapter
President from2000to2001.He is also a Member of Eta Kappa Nu.
Eric W.Maier,photograph and biography not available at the time of
publication.
Kyoo Nam Choi(M’01),photograph and biography not available at the time of
publication.
JUAREZ et al.:DISTRIBUTED FIBER-OPTIC INTRUSION SENSOR SYSTEM2087 Henry F.Taylor(SM’78–F’85)was born in
Ft.Worth,TX,on September27,1940.He received
the B.A.,M.A.,and Ph.D.degrees in physics from
Rice University,Houston,TX,in1962,1965,and
1967,respectively.
He was employed as a Research Physicist at the
Naval Ocean Systems Center(formerly the Naval
Electronics Laboratory Center),San Diego,CA,
from1967to1978.From1978to1980,he was with
Rockwell International,Thousand Oaks,CA,where
he was Principal Scientist of the Optoelectronics
Department of the Microelectronics Research and Development Center.From
1980to1985,he was Head of the Optical Techniques Branch of the Naval
Research Laboratory,Washington,DC.He joined the Electrical Engineering
faculty at Texas A&M University,College Station,as a Professor of Elec-
trical Engineering and Director of the Institute for Solid State Electronics in
November1985and has held the Irma Runyon Chair in Electrical Engineering
since1988.In2001,he was promoted to his present position of Distinguished
Professor of Electrical Engineering at Texas A&M University.Since1970,his
principal research interests have been in the?elds of?ber optics,integrated
optics,and diode laser applications.He has authored more than300journal
papers and conference presentations and holds40U.S.patents.
Dr.Taylor is a Fellow of the Optical Society of America(OSA),a Life
Member of the American Society of Naval Engineers,and a Member of the
American Physical Society.He was awarded a Civil Service Commission/Navy
fellowship to study Systems Analysis at the Massachusetts Institute of Tech-
nology,Cambridge,from1971to1972.He also received the Naval Electronics
Laboratory Center Annual Science Achievement Award in1974,the American
Society of Naval Engineers’Solberg Award for Applied Research in1975,
and the Texas A&M Association of Former Students Award for Excellence
in Research in1991.He served as Conference Chairman for the IEEE/OSA
Topical Meeting on Integrated and Guided Wave Optics for1986and as
Program Chairman in1984.He was a Member of the steering committee for
the Optical Fiber Communication(OFC)and Integrated Optics and Optical
Communications Conferences(IOOC)from1987to1989.He was Guest Editor
for a Special Issue of the IEEE T RANSACTIONS ON C IRCUITS AND S YSTEMS
in December1979and for a Special Issue of the J OURNAL OF L IGHTWA VE
T ECHNOLOGY in March1987.
分布式光纤传感技术报告-12.10
摘要 分布式光纤传感技术是在70年代末提出的，在这十几年里,产生了一系列分布式光纤传感机理和测量系统,并在多个领域得以逐步应用。目前, 这项技术已成为光纤传感技术中最具前途的技术之一。本文主要介绍了光纤的相关特性，分布式光纤传感技术的特点、作用及其分类，详细论述了各种分布式光纤传感器的原理、分布式光纤传感技术的研究现状和具体应用。 关键字：光纤分布式光纤传感技术原理研究现状应用
目录 摘要 引言 1、分布式光纤传感技术简介 1.1光纤基础知识 1)光纤的结构特性 2)光纤的机械特性 3)光纤的损耗特性 2、分布式光纤传感技术原理 2.1 基于光纤后向散射的全分布式光纤传感技术 2.1.1 基于OTDR的微弯传感器 2.1.2 基于自发拉曼散射的光时域散射型（ROTDR）传感器 2.1.3基于受激拉曼效应的传感器 2.1.4基于自发布里渊散射的光时域反射型（BOTDR）传感器 2.1.5基于受激布里渊散射效应的传感器 1)基于布里渊散射的光时域分析型（BOTDA）传感器 2)基于布里渊散射的光频域分析型（BOFDA）传感器 3)基于布里渊散射的光相关域分析型（BOCDA）传感器 4)基于布里渊散射的光相关域反射型（BOCDR）传感 2.1.6基于瑞利散射的偏振光时域反射型（POTDR）传感器 2.1.7基于相位敏感的光时域反射型（Φ-OTDR）传感器 2.2 长距离干涉传感技术 2.3 基于光纤干涉仪的准分布式光纤传感技术 2.4 基于FBG的准分布式光线传感技术 3、分布式光纤传感技术国内外研究进展 4、分布式光线传感技术应用实例
光纤光栅传感器是一种常用的光学传感器件，分布式光纤光栅就属于准分布式光纤传感器件中的一种。选题方向合理。请尽快确定课题完成方式，明确研究内容，尽快开展课题调研论证工作。75 分布式光纤光栅传感技术 光纤传感技术是一种以光纤为媒介，光为载体，感知和传输外界信号（被测量）的新型传感技术，是伴随着光导纤维及光纤通信技术发展而逐步形成的。在光通信系统中，光纤被用作远距离传输光波信号的媒质，在这类应用中，光纤传输的光信号受外界因素的影响越小越好，但是，在实际的光传输过程中，光纤容易受到外界环境因素的影响，如温度、压力、应变等外界条件的变化将引起光纤中传输光波的特征参数如频率、相位、光强、偏振态等的变化，通过测量这些参数的变化，就可以得到外界作用于光纤的物理量，这就是光纤传感技术。光纤传感技术的基本原理是：将光源的光入射进光纤，当光在光纤中传输的过程中受到外界物理量影响，使得被测参数与光纤内传输的光相互作用，进行调制，从而使其光学性质如光的频率、波长(颜色)、强度、相位、偏振态等发生变化成为被调制的信号光，然后将这一调制的信号光送入光探测器中进行解调，经信号处理后就可获得被测参数。 光纤传感器与传统传感器相比具有许多明显优势： 1）体积小、重量轻，几何形状具有多方面的适应性，可以做成任意形状的传感器和传感器阵列。 2）抗电磁干扰能力强、耐高温、耐腐蚀，在易燃、易爆环境下安全可靠。 3）光纤传感器件多是无源器件，对被测对象影响较小。 4）便于复用，便于成网。它既可以作为信息的传递媒介，又可以作为信号测量的传感装置。 5）光纤传感器传输频带宽，动态范围大，测量距离长。 光纤传感器的种类很多，按照其工作方式可分为：点式、准分布式和分布式三类。其中，准分布式光纤传感器是使用传感网络系统进行测量的，其光纤不作为传感元件，只作为传输元件，其敏感元件为多个点式的传感器，它们采用串联或各种网络结构形式连接起来，利用波分复用、时分复用或频分复用等技术形成分布式网络系统，进而可以较精确地分时或同时得到被测量信息的空间分布，也可同时得到某一点或某些空间点上不同被测量的分布信息。 光纤光栅传感器除了具有一般光纤传感器耐高温、耐腐蚀等优点之外，还具有波长编码，抗干扰能力强等特性。另外，它较易于在一根光纤中连续写入多个光栅，以制成分布式光纤光栅传感，制得的光栅阵列轻巧柔软，可与渡分复用或时分复用技术等相结合，且十分适于作为分布式传感兀件贴于结构表面或埋人到材料和结构的内部，以实现对结构应变、温度以及压力等的多点监测，这对于目
基于分布式光纤传感的桩基检测技 术可行性研究报告 项目名称：基于分布式光纤传感的桩基检测技术研究 For personal use only in study and research; not for commercial use 项目类别：新技术研究与开发 委托单位：武汉市城市建设投资开发集团有限公司 For personal use only in study and research; not for commercial use 中铁大桥勘测设计院有限公司 申报单位：华中科技大学 编写单位：华中科技大学
编写时间：2013年1月16日 基于分布式光纤传感的桩基检测技术研究 一、项目研究的意义、目的和国内外发展概况 1.1项目研究的意义、目的 桩基是大型构筑物的重要组成部分，是涉及工程安全问题的结构中占主导地位的构件之一。一旦基础失效，势必造成整体建筑物破坏。因此，桩基检测是整个建筑结构安全、稳定的保障。 桩基检测是对单桩承载力和桩身质量等进行全面评价的重要措施，是确认桩基工程合格的重要环节，同时也是对不合格桩进行补强或返工的依据。因为桩基是隐蔽工程，发现其缺陷，以及其后的处理都有难度，因此，在桩基设计前要进行必要的试验，施工后都需要检测。 传统的桩基检测，主要基于声波的反射原理，以及静态载荷下沉降率的研究。其特点是在时间上不具有连续观测的可行性。因此，分
布式光纤传感器观测手段是桩基检测技术的革命性进展。 本课题研究目的是确定分布式光纤传感在桩基检测中的理论计算基础，使智能FRP筋优良检测性能在桩基检测中充分发挥，其检测原理是基于布里渊散射机理的PPP-BOTDA分布式光纤传感技术。分布式光纤检测技术广泛用于大型重要构筑物（机场、桥梁和隧道等）的温度、变形检测，较之发展较快的光栅光纤，分布式光纤具有更好的应用功能。光栅光纤是准分布式的，在一条线路上一般只能布设8-9个观测点；而分布式光纤可以在空间上连续检测每一个点，空间分辨率可以达到10cm，温度测量精度达到0.1度，应变测量统计精度达到2.4微应变，而智能筋较分布式光纤，在实际施工中，智能筋检测施工要求更简单，智能筋内的传感光纤由于复合材料的保护，其耐久性更好。虽然因此智能筋的检测精度较分布式光纤有所降低，但与一般检测方法比，智能筋检测更加准确有效，且具有长期检测特点。因此，对智能FRP筋在桩基检测应用的研究具有远大前景，其先进检测技术在桩基工程中的应用将推动桩基质量提高，全寿命期的实时监控将大大减少因桩基损坏造成的损失。 1.2国内外发展概况 桩基检测技术是一门新兴行业，我国的检测技术起源十20世纪80年代末，当时的检测方法主要采用声波透射法来抽检。随着工程建设的的蓬勃发展，在桥梁、高层建筑、重型厂房、港口码头、海上采油平台等工程中大量采用桩基础，从而推动了检测频率、检测方法
光纤中的散射光 当光（电磁）波射入介质时，若介质中存在某些不均匀性（如电场、相位、粒子数密度n、声速v等）使光（电磁）波的传播发生变化，有一部分能量偏离预定的传播方向而向空间中其他任意方向弥散开来，这就是光散射。光的散射现象的表现形式是多种多样的，从不同的角度出发，可有不同的分类，但从产物的物理机制来看，可以分为两大类： 第一类是非纯净介质中的光散射，该散射现象不是介质本身所固有的，而强烈地依赖于掺杂进来的散射中心的性质或介质本身的纯净度。其规律主要表现为：散射光的频率与入射光的频率相同；散射光的强度与入射波长成一定关系。 第二类是纯净介质中的散射，即使所考虑的介质是由成分相同的纯物质组成，其中不含有外来掺杂的质点、颗粒或结构缺陷等，仍然有可能产生光的散射现象，这些散射现象是介质本身所固有的，与介质本身的纯净度没有本质上的关系。属于这类纯净介质的散射现象有如下几种： 1）瑞利散射设介质是由相同的原子或分子组成，由于这些原子或分子空间分布的随机性的统计起伏（密度起伏），造成与电极化特性相应的随机性起伏，而形成入射光的散射。这种散射现象的特点是频率与入射光频率相同，在散射前后原子或分子内能不发生变化，散射光强度与入射光波长的四次方成反比。 2）拉曼散射这种散射现象通常发生在由分子组成的纯净介质中，组成戒指的分子是由一定的原子或离子组成的，它们在分子内部按一定的方式运动（振动或转动），分子内部粒子间的这种相对运动将导致感生电偶极矩随时间的周期性调制，从而可以产生对入射光的散射作用；在单色光入射的情况下，这将是散射光的频率相对于入射光发生一定的移动，频移量正好等于上述调制频率，亦即与散射分子的组成和内部相对运动规律有关。 3）布里渊散射对于任何种类的纯净介质来说，由于组成介质的质点群连续不断的做热运动，使得在介质内始终存在着不同程度上的弹性力学振动或声波场。连续介质的这种宏观弹性力学振动，意味着介质密度（从而也是折射率）随时间和空间的周期性起伏，因而可对入射光产生散射作用，这种作用类似于超声波对光的衍射作用，并且散射光的频移大小与散射角及介质的声波特性有关。
文章编号：1007-2322（2013）00-0000-00 文献标志码：A 中图分类号：XXX 分布式光纤传感多参量监测技术的研究现状及趋 势 闫志学 （中国电力科学研究院，北京海淀，100192） The Present Situation and Trend of Research on Distributed Optical Fiber Sensing Technology of Multi-Parameter Monitoring Yan-Zhixue China Electric Power Research Institute, Beijing 100192 摘要：鉴于目前智能电网发展的需求，保障输电线路的正常运行，亟待开发用于输电线路安全监测的多参量传感技术，以建立适应现代社会电力发展所需的智能输电线路。以具有抗电磁干扰、易植入、易组网等特点的光纤传感技术为基础，阐述了基于瑞利散射、拉曼散射、布里渊散射的分布式光纤传感技术和研究进展，并在此基础上分析了分布式光纤传感技术的发展趋势。探讨了基于ROTDR、BOTDR、BOTDA、Φ-OTDR技术相融合的分布式光纤传感技术，研究了分布式光纤多参量监测技术，及其在智能电网中应用于温度、应变、振动等参量同时在线监测的技术预测。该技术的发展及应用将会实现输电线路的火灾、覆冰、局部放电监测、动态载流量和热寿命预测等分析及故障分析与定位技术，提高输电线路的智能监测水平。单根光纤多种参量的监测技术，实现了输电线路减负及运维管理简便的目的,将会引领输电线路智能监测并达到一个顶峰。 关键词：分布式光纤传感技术；多参量；智能电网；温度；应变；振动 Abstract:In view o f the demand of the smart grid’s development, and ensure the normal working of electric transmission lines, the multi parameter sensing technology of safety monitoring of transmission line is expected to develop, in order to establish the adaptive intelligent electric transmission lines needed for modern social power development. The research based on optical fiber sensor whose features are anti electromagnetic interference, be easy to implant and easy networking. The technology and research progress of the distributed optical fiber sensors were described, which based on Rayleigh scattering, Raman scattering and Brillouin scattering. And the development trend of the distributed optical fiber sensors was also analyzed. The distributed optical fiber sensors are used for multi parameter monitor which based on the mixing of ROTDR, BOTDR, BOTDA and Φ-OTDR were discussed, also studied the distributed optical fiber multi parameter monitoring, and forecast its application for online monitoring the smart grid of temperature, strain, vibration ect. The technology development and application will achieve electric transmission line of fire, ice and partial discharge monitoring, dynamic load flow and thermal life prediction analysis, also fault analysis and location technology, improve the level of intelligent monitoring of electric transmission line. Monitoring technology of single fiber various parameters, realizes the transmission line burden and operation management simple purpose, will lead to transmission line intelligent monitoring and reach a peak. Key words:the distributed optical fiber sensors; multi parameter; the smart grid; temperature; strain; vibration 0引言 光纤传感技术按照工作方式的不同可以划分为点式光纤传感[1]、准分布式光纤传感[2]和分布式光纤传感。目前，设备的状态监测[3-4]都需要大量监测数据，即大量传感器采集，点式光纤传感器需要一支传感器对应一个解调通道，传感器只能星型布网，呈现出传感光缆布置复杂、仪器设备繁多等缺点，因此点式传感器的发展受到工程应用的局限；准分布式光纤传感不仅可以实现对设备关键点的监测，还能够实现传感器多种组网技术，因此其在设备全方位立体监测中非常适宜；分布式光纤传感中，光纤既是传输媒介又是传感元件，可以实现空间上的连续探测，因此其在线路和大面积表面监测
长距离分布式光纤振动传感系统关键技术要点 发表时间：2018-10-22T14:09:53.943Z 来源：《防护工程》2018年第14期作者：李顺为 [导读] 分布式光纤传感器作为光纤传感器相关技术中较为重要的器件，其不仅具有普通光纤传感器所具有的无辐射干扰性 李顺为 身份证号码：45042119830530XXXX 摘要：分布式光纤传感器作为光纤传感器相关技术中较为重要的器件，其不仅具有普通光纤传感器所具有的无辐射干扰性，抗电磁干扰较好，化学稳定性良好等优势，而且还具有光纤所具有的一维空间实施连续性分布的特性，其最主要的作用就是能够进行长距离的监测，以及定位精确等相关优势。本文主要对长距离分布式光纤震动传感系统的关键技术进行相应分析。 关键词：分布式光纤感；偏振态控制；相位锁定；定位 一、前言 对于光纤传感技术而言，由于其具有较高的灵敏度，且定位精准，能够抗电磁干扰等优势，极其受人们欢迎，且已经成为传感领域当中研究的重点。所谓光纤传感器，主要就是指通过对光波的利用，并将其作为实施探测事件的承载，并将光纤当做传输承载的一种媒介，并利用光波进行监测，以此实现对相关事件的探测[1]。根据光纤在传感器当中所具有的作用，主要将光纤传感器分为两种，也就是功能型与非功能型；而依照光波在光纤当中进行调制的方式，主要分为强度调制型、偏振调制型、频率调制型和相位调制型；依照探测过程是否有光波干涉，主要分为干涉型以及非干涉型[2]。本文主要依据长距离振动传感系统所具有的特点，以光纤M-Z干涉仪的光相位传感方法，对其关键技术进行分析。 二、光相位检测与定位的基本原理 对于长距离分布式光纤振动传感系统而言，本文主要对光相位调制型的光纤M-Z干涉仪对相关振动时间实施相应的传感。当M-Z振动传感器通常是被埋藏在地下的相关管道以及电缆周围实施工作的时候，振动时间通常是根据应力，对光波的相位实施调制。对于光纤M-Z 当中的振动传感系统而言，其径向应力的实际检测灵敏度通常能够达到10-9rad/m.Pa。 对于探测系统当中总长度达到L的光纤，入射光波通常为Ain。当光纤没有受到应力作用的时候，出射的光波为：Aout=Ainexp（i2πnL/c）[3]。 当传感系统的某个位置受到相应径向力作用的时候，该位置的光纤长度，光纤直径、折射率等都会出现相应的变化，其参数的不断变化，就致使光波的相位产生相应的变化，假设外界产生的应力作用，出现的相位变化为Δφ，这时出射的光波为：Aout=Ainexp[i （2πnL/c+Δφ）]，光在光纤当中的相位为：φ=βL（β为光纤中光传播常数，L为光传播的距离）[4]。 三、长距离分布式光纤振动传感系统关键技术 （一）、系统的抗偏振衰落技术 所谓长距离分布式的光纤传感系统，主要就是通过对光纤M-Z干涉仪进行使用，并以此对振动的信号进行探测，其所输出的结果主要是指光所产生的干涉信号。干涉信号所具有的清晰度，主要是根据M-Z干涉仪两臂当中的光信号具体的偏振态所决定。其在实际运用过程中，主要根据光纤形变等相关因素，所导致的光纤双折射，就会使其光波出现偏振态变化，并致使干涉信号出现衰落，这对振动信号的有效定位以及识别具有严重影响。而所谓的光纤双折射，就是光纤由于其自身原因，以及外界环境等原因，都会是光纤出现形变，或者是受力不均匀的现象，这就使光纤转变为不同方向的异性介质，并导致光纤出现双折射的现象。 系统的抗偏振衰落技术，主要是依据光纤的双折射以及光偏振态所具有的变化之间的关系进行分，以此使偏振态控制器所产生的干扰信号的强度得以有效增强，并使长距离振动传感系统对振动信号所具有的探测能力得以有效提高。 对于长距离振动传感系统而言，其主要是通过对全光纤M-Z的干涉仪结构进行选用。而保偏光纤由于具有较高的成本，因此，系统就需要对普通的G652单模光纤进行使用。如图1所示，由于普通的单模光纤所具有的双折射能够使x与y方向上所具有的基模LP01或者 HE11，有着不同的传播常数，这就会使基模的偏振态能够沿着光纤所延伸方向产生相应变化。如果光的偏振态通过一个周期，变回成初始的状态，其所产生的光纤长度就是一个拍所具有的长度Lb：Lb=2π/Δβ，其中，Δβ是单模光纤当中两个互相正交的偏振基模，也就是HE11x 与HE11y沿着光纤的轴向实施传输过程中的传播常数差为：Δβ=βx-βy=2π(nx-ny)/λ[5]。以上所述的两个物理量当中，Δβ主要表现为单模光纤双折射主要原因为：拍长Lb主要表现为单模光纤双折射所具有的大小。 图1 光纤双折射导致偏振态的改变示意图 （二）、相位锁定技术 对于长距离分布式的光纤传感系统而言，其主要对光纤M-Z的干涉仪结构进行选用，其所输出的信号，主要就是指干涉仪所产生的相位差。其在实际运用过程中，不仅需要对振动信号所导致形成的相位差变化进行感测，而且光纤应力与温度等相对的缓变也会使相位差产生变化。而对于这种较为缓慢的、出现的相位变化而言，其会对信号输出所具有的响应度以及灵敏度都具有严重影响。 相位锁定技术使用主要的检测方法为以下几点：（1）相位调制载波法。该法主要由A.Dandridge等人所提出的，其主要是对小相位进行检测，实际的测量范围主要为10-7rad[6]。对于长距离的M-Z振动传感系统而言，主要是对PGC进行利用，其实现探测灵敏度较高的主要原理就是，在M-Z干涉仪上面的探测臂上，对有规律的扰动实施相应的引入，以此产生相应的载波，并将需要进行探测的小相位信号在载波上实施加载，并通过载波的探测，对小相位实施相应的检测。（2）直流相位跟踪法。由于这种方法的实现较为简单，只需要使用模拟
分布式光纤传感器系统测量原理 [摘要]: 光在光纤中传播，光与介质中光学声子、声学声子发生碰撞，会产生后向散射的光，这些后向散射的光的频率、强度均会发生改变。其改变量的大小与折射率等有关，而折射率等因素受光纤的应变、温度的影响。 [关键词]：光纤；光纤传感器；测量 中国分类号：TN6 文献标识码：A 文章编号：1002-6908(2007)0110021-01 1．BOTDR的分布式温度和应变测量 BOTDR的分布式应变测量原理，当入射光在光纤中传播时，入射光会与声波声子相互作用，产生布里渊散射。其散射光的传播方向与入射光的传播方向相反。当入射光的波长那布里渊散射的最大能量的频率与入射光的频率之差大约是11GHz。这个频移量就叫做布里渊频移。如果光纤沿径向发生了应变，那布里渊散射对应于应力的频移量，如图1所示： 为了测量分布式的应变，通过使用BOTDR技术，沿着光纤观测布里渊散射光的频谱，确定布里渊频移的大小，从而达到测量应力的目的。如图2所示。在光纤的一端脉冲光入射，同时在这端使用时间域的BOTDR接收布里渊后向散射光。因此，产生布里渊散射的位置与脉冲光发射的位置的距离Z可以由下列登时确定，在这个式中，时间T是发射脉冲光与接收的布里渊散射光的时间差。 为了能获得布里渊散射光的频谱，我们重复上面所做的步骤，我们缓慢的改变入射光的频谱宽度。在布里渊散射光的不同频率段，我们能获得大量的分布式能量。如图2所示。所以，我们能够从获得的布里渊散射光的波形，知道在光纤中任何位置，那散射光的频谱。所以，我们固定频谱到那些Lorentzian弯曲和使用能量峰值的频谱。通过相应弯曲位置的应力。 应变与布里渊频率的改变量的各自联系。在实际的测量中，测量之前，（1）中的系数和布里渊频移可以在无应变时测量出来。然后，频移转换成应变。 注：本文中所涉及到的图表、注解、公式等内容请以PDF格式阅读原文。
第37卷 第6期 中 国 激 光 Vol.37,No.62010年6月 CHIN ES E J OURNAL OF LAS ERS J une ,2010 文章编号:025827025(2010)0621501204 用于分布式光纤传感的全光纤激光器 高存孝1 朱少岚1,2 冯 莉1 宋志远1,2 曹宗英1 何浩东1 牛林全1,2 1 中国科学院西安光学精密机械研究所瞬态光学与光子技术国家重点实验室,陕西西安710119 2 中国科学院研究生院,北京100049 摘要 报道了一台适用于分布式光纤传感的全光纤激光器。激光器基于主振荡功率放大(MOPA )技术,种子光源为半导体激光器,放大器为掺铒光纤放大器。实现了重复频率和脉冲宽度分别独立可调的激光输出,中心波长为 1550nm ,光谱的3dB 带宽小于0.2nm ,获得的最高峰值功率为1.1kW ,输出的激光脉冲中放大自发辐射(ASE ) 功率分数的最大值低于10%。 关键词 激光器;光纤激光器;掺铒光纤放大器;分布式光纤传感 中图分类号 TN248.1 文献标识码 A doi :10.3788/CJL 20103706.1501 A n All Fi be r L as e r f o r Dis t ri but ed Op t ical Fi be r S e ns o r Gao Cunxiao 1 Zhu Shaolan 1,2 Feng Li 1 Song Zhiyuan 1,2 Cao Zongying 1 He Haodong 1 Niu Linquan 1,2 1 St a te Key L abor ator y of Tr a nsie nt Op tics a n d Photonics ,Xi ′a n I nstit ute of Op tics a n d Precision Mecha nics , Chi nese Aca de m y of Sciences ,Xi ′a n ,S ha a nxi 710119,Chi n a 2 Gr a d ua te U niversit y of Chi nese Aca dem y of Scie nces ,Beiji ng 100049,Chi n a Abs t r act An all fiber laser which is suitable for dist ributed optical fiber sensor is reported.The laser is based on the technique of master 2oscillator 2power 2amplifier (MOPA ),whose seed laser is a laser diode and amplifier is Er 3+doped fiber amplifier.The laser operates in wavelength of 1550nm with the tunable repetition rate and the p ulsewdith ,and the 3dB width is less than 0.2nm.The maximum peak power 1.1kW of laser p ulse is obtained ,and the power of amplified spontaneous emission (AS E )in the outp ut pulse is less than 10%in all condition.Key w or ds lasers ;fiber laser ;Er 3+doped fiber amplifier ;dist ributed optical fiber sensor 收稿日期:2010203222;收到修改稿日期:2010204216 作者简介:高存孝(1979—),男,助理研究员,主要从事脉冲光纤激光器、放大器以及脉冲半导体激光器技术等方面的研 究。E 2mail :cxgao @https://www.doczj.com/doc/a27207104.html, 1 引 言 分布式光纤传感技术是集光、机、电为一体的综合性技术,具有寿命长、耐高电压、抗电磁干扰和系统简单等优点,可以实现连续的空间温度测量、气体泄漏的在线监测等,目前已经广泛用于电力冶金、石油化工、交通运输和火灾预防报警等诸多领域[1～4]。在分布式光纤传感系统中光纤既作为传输通道,同时又是传感的功能元件,可以非常容易地获得链路上被测量参数的空间分布和时间变化信息,这是传统光纤传感所无法比拟的。 目前的分布式光纤传感技术主要有:基于光纤拉曼散射或布里渊散射的光时域反射及频域反射技 术、基于光纤瑞利散射的偏振光时域反射技术、长距 离光干涉技术、菲涅耳反射技术以及准分布式光纤布拉格光栅复用技术等[5～12]。这些技术分别有各自的特点,适合于不同的应用场合。对于基于光纤拉曼散射的光时域反射技术而言,其工作原理是利用光纤背向拉曼散射的温度效应,即光纤所处空间各点的温度场能够改变光纤中背向拉曼散射光的强度,通过测量拉曼反射光的强度就可以得到相应的温度值,并使用光时域反射技术来确定所测温度点的位置。这种分布式光纤传感技术系统结构简单、成本低和应用范围广,目前已经实现了10km 以上的测量距离,是一种很有市场前景的技术。
分布式光纤传感技术在地震监测中的应用探讨 刘文义 （中国地震局第二监测中心，陕西西安 710054） 1 分布式光纤传感技术 分布式光纤传感利用光导纤维具有的传感、传输双重特性，实现对被测量对象沿光纤分布的多点甚至连续测量，以达到取代多台独立点传感器的目的。它既具有光纤的抗电磁场干扰、大信号传输带宽等优点，又突破了点式光纤传感的限制，可以同时获得被测量对象测量参数的空间分布及其随时间变化的信息，并使之能够进行远距离遥测监控，在许多工程领域有重大的应用价值。 分布式光纤传感技术主要有3个方面的突破：①基于瑞利散射的分布式光纤传感技术；②基于拉曼散射的分布式光纤传感技术；③基于布里渊散射的分布式光纤传感技术。基于布里渊散射的分布式传感技术的研究起步较晚，但由于它在温度、应变测量上所达到的测量精度、测量范围以及空间分辨率均高于其他传感技术，因此，这种技术在目前得到广泛关注与研究。 2 布里渊分布式光纤传感系统研究现状和产品性能分析 （1）传感方案的研究现状。目前，基于布里渊散射的分布式光纤传感系统从方案上分主要有三种：时域反射计（BOTDR）的光纤传感技术、时域分析（BOTDA）的光纤传感技术、光频域分析（BOFDA）的光纤传感技术。由于基于BOTDR的传感方式最大的优点是只需要单端入射，结构简单，从而在实际应用中会很方便，所以，目前国内外对此方案的研究投入相对较多，是技术与产品最成熟的光纤传感器。 （2）传感系统性能的研究现状。对传感系统的性能的研究成果比较突出的主要集中在以下4个方面：温度或应变传感系统的研究；温度和应变同时传感系统的研究；提高系统空间分辨率的研究；提高系统传感距离的研究。 （3）主要分布式光纤传感器产品。目前主要有日本、英国、瑞士、加拿大等国的公司生产商用产品。 3 分布式光纤监测技术的最新进展 （1）国际研究进展。近年来，光纤传感器研究现状和发展趋势呈现出以下几个方面的特点：传感监测的解调技术更加先进，性能和指标更加精确和准确；分布式监测越来越受重视，已成为地质、岩土和土木工程监测的发展方向；应用技术的研究在不断加强，包括光纤传感器的封装技术，特种传感光纤的研制，传感光纤的铺设和安装技术等；相关技术的应用领域和范围迅速扩大。 （2）我国研究应用现状。近几年，我国在研究和应用方面有了长足的发展，新型传感技术不断涌现，工程的应用面不断扩大。与国际上一些先进国家相比还存在着一定的差距，主要体现在一些核心的传感解调技术还掌握在少数国家手中，监测仪器昂贵导致这些先进技术的推广和应用受到了很大影响。 4 在地震监测中的可行性研究 与目前地震监测的方法相比，分布式光纤传感器除具有结构简单、灵敏度高、耐腐蚀、电绝缘、防爆性好、抗电磁干扰、光路可挠曲、易于与计算机连接、便于遥测等优点外，其最显著的优点就是可以测出光纤沿线任一点上的应变、温度和损伤等信息，实现对监测对象的全方位立体监测。因此，引进、研究和开发分布式光纤应变/温度观测技术对活动块体边界带（或断裂带）的监测具有重要意义。 （作者信箱：sf55@https://www.doczj.com/doc/a27207104.html,） 101
分布式光纤传感温度报警系统Ξ 张在宣 郭 宁 余向东 吴孝彪 (中国计量学院光电子技术研究所,杭州310034) 摘 要 研制了一种由分布光纤温度传感器系统组成的新型在线自动温度检测、报警系统,它是一种特殊的光纤通信网络,也是一种光纤雷达。文中讨论了系统的工作原理、调制与解调原理,系统的组成结构和系统的报警特性。在一根2km光纤上可采集一千个温度信息并能进行空间定位,是一种理想的温度报警系统。 关键词 分布光纤温度传感器 光时域反射技术 温度报警系统 一、前 言 分布式光纤温度传感器系统实质上是分布光纤喇曼(Raman)光子传感器(DOFRPS)系统,它是近年来发展起来的一种用于实时测量空间温度场的光纤传感系统。在系统中光纤既是传输媒体又是传感媒体,利用光纤背向喇曼散射的温度效应,光纤所处空间各点的温度场调制了光纤中的背向喇曼散射的强度,即反斯托克斯(stokes)背向喇曼散射光的强度),经波分复用器和光电检测器采集了带有温度信息的背向喇曼散射光电信号,再经信号处理系统解调后,将温度信息实时从噪声中提取出来并进行显示,它是一种典型的光纤通信网络;在时域里,利用光纤中光波的传播速度和背向光回波的时间间隔,利用光纤的光时域反射(O TDR)技术对所测温度点定位,它是一种典型的光雷达系统。 分布光纤传感系统中的传感光纤不带电,抗射频和电磁干扰,防燃、防爆、抗腐蚀、耐高电压和强电磁场、耐电离辐射,能在有害环境中安全运行,系统具有自标定、自校准和自检测功能;即使在光纤受损时不仅可继续工作,而且可检测出断点位置。在一根2km光纤上可采集一千个温度信息并能进行空间定位,由于分布光纤传感系统的优越特性,已经开始应用于火灾自动温度报警系统。 分布光纤温度传感器的主要用途: 11用于煤矿、隧道的温度自动报警控制系统; 21油库、油轮,危险品仓库,大型货轮,军火库等温度自动报警控制系统; 31高层建筑、智能大厦、桥梁、高速公路等在线动态检测和火灾防治及报警; 41各种大、中型变压器,发电机组的温度分布测量,热保护和故障诊断; 51地下和架空高压电力电缆的热检测与监控; 61火力发电所的配管温度、供热系统的管道、输油管道的热点检测和故障诊断;化工原料、照相材料及油料生产过程在线动态检测; 71作为一种典型的机敏结构用于航空、航天飞行器在线动态检测和机器人的神经网络系统。 分布光纤温度传感系统是一种光机电和计算机一体化的高科技,世界上有英国、日本、瑞士和我国研制生产,英国、日本等应用于大型变压器、发电机组热保护和保障诊断,日本、瑞士和我国开始应用于火灾自动报警控制系统。 分布光纤温度传感器系统可显示温度的传播方向、速度和受热面积。可将报警区域的 42计量技术 20001№2Ξ国家首批产学研工程项目资助
电缆局放监测中的分布式光纤传感 方案探讨 作者吴海生 (上海欧忆智能网络有限公司，上海，200040) 摘要：为确保电网的运行安全，对交联聚乙烯（XLPE）电力电缆局部放电的在线监测和定位技术已受到国内外众多专家的研究热点之一。本文在介绍了电力电缆局部放电危害，电力电缆局部放电机理以及现有监测技术后，提出了基于分布式光纤传感技术的电力电缆局部放电监测方案。并探讨了方案实施中的关键技术解决思路与方法。 关键字电力电缆局部放电光纤传感在线定位监测 一、电力电缆的局部放电危害 近年来，随着我国城市智能电网的不断改造建设，具有高温大容量特点的交联聚乙烯（XLPE）电力电缆作为主流产品已经广泛应用于输电线路和配电网中。资料表明：在对全国主要城市126家电力电缆运行维护单位10kV以上的电力电缆(总长度91 000 km)运行状态进行调查统计和故障原因分析发现，我国的10～220 kV电力电缆的平均运行故障率相对经济发达国家仍高出约10倍【1】。 交联聚乙烯电力电缆主要故障的早期表现均为故障部位的局部放电现象。电力电缆局部放电程度也与电力电缆绝缘状况密切相关。局部放电量的变化预示着电缆绝缘一定存在着可能危及电缆安全运行寿命的缺陷，是电力电缆绝缘崩溃的前兆。一旦绝缘崩溃，将造成电网的停电损失。因此，对电力电缆的局部放电的监测是获知电力电缆运行状态的重要方法。图1为因过度局放造成的电缆绝缘被击穿损坏结果图： 图1 局部放电击穿电缆绝缘结果图 由于绝大多数的电力电缆从局部放电到电缆绝缘击穿都有一个较长的时间过程，国内外专家学者、IEC、IEEE以及CIGRE等国际电力权威组织一致推荐局部放电监测是作为对XLPE绝缘电力电缆运行状况评价的最佳方法。因此，准确在线监测量XLPE绝缘电力电缆的局部放电发生部位，及时消除局部放电隐患，是建设坚强可靠智能电网的最直观、最理想、最有效的方法。同时，亦是研究开发难度最大的方法。目前仍然没有实用的相关技术得以实现。 二、电力电缆的局部放电机理与现有监测技术 国际电工委员会IEC60270对局部放电（简称：局放、PD）现象的定义是：在高压下固体或液体绝缘系统里一小部分的局部介质破坏。 电力电缆局部放电的形成机理是：当电缆在制造中，因材料不纯、加工设备故障等原因，使电缆本体内部产生材料缺陷。当电缆在施工中的不当，或使用中遭到外力破坏，造成电缆外护套等电缆破损缺陷。上述这些缺陷处会在电缆导体的高电压强电场作用下，产生高电压尖端放电等现象。持续的高压放电，产
光纤分布式声波传感技术 刘德中通信学院 2013010917006 内容摘要 声波属于物质波,其实质是质点振动、应力、压力等在弹性介质中的多样表现形式。在声学的研究领域中,声波的产生机制、传播形式以及检测方法是会共同涉及的内容。目前的声波检测技术就是利用声波信号在弹性介质内的传播变化实现对检测目标的测探、准确识别、定位等。 在光纤传感领域,当前的一个研究热点就是光纤声波检测,它可以用作水听器,应用于海洋、陆地石油、天然气勘探输油管道实时检测预警系统;也可用作光纤麦克风,用光纤光栅制成的声波传感探头基元以光纤光栅的中心波长调制来获得传感信息的,它具有灵敏度高、抗干扰能力强、全光纤的特点,同时还具有能够实现波分复用、检测探头的微型化等特点。 关键词：声波检测光纤传感技术分布式震动传感布里渊散射 一、技术原理 （一）基于光纤光栅的传感器 基于光纤光栅的传感器的原理是当温度、应变、折射率、应力、浓度等外界环境因素出现变化时,光纤光栅的有效折射率或者是光纤光栅周期就会发生 改变,从而使得光纤光栅的中心波长出现变化,对这一变化量经过信号处理之 后,就能够获得所需要检测的参数。这一过程中,传感信号的获得方式是通过光 纤光栅中心波长的调制实现的,相比于强度调制传感器而言,光纤光栅传感器 的灵敏度更高,更广的动态测量范围。所以,基于光纤光栅的传感器以其自身强 大的抗干扰能力、高灵敏 度以及对光源的稳定性及 能量特征要求低的特性, 使其在精确、精密测量方 面十分合适,光纤光栅传 感器目前已经占据了以光 纤为主要材料的44%左右。 （二）光纤声波传感器 声音属于微压动态信号,要想测量声音信号,可以通过监测频率或声压来实现。一般情况下,人们在传递和探测声信号时,会使用电子式传声器,该传声 器具有声-电换能原理,然而在一些特殊的环境中,如在核磁共振、强电磁干扰 或易燃易爆环境中,一些电子式传声器会失去作用,加之信号衰减会给传感器 端的弱电量信号带来不利影响,所以在较远的距离间无法使用电子式传声器, 这给远距测量带来了诸多难题。为了让信息能够准确传递出去,必须研宄一种 无源传声器,这种传声器不受电磁的干扰,还能在较远的距离间进行传输。光纤
第31卷 第6期 岩 土 工 程 学 报 Vol.31 No.6 2009年6月 Chinese Journal of Geotechnical Engineering June 2009 分布式光纤传感技术在预制桩基桩内力测试中的应用 魏广庆1，施 斌1，贾建勋2，胡 盛1，李 科1，张 丹1 (1. 南京大学光电传感工程监测中心，江苏 南京 210093；2. 山西省电力勘测设计院，山西 太原 030001) 摘 要：分布式光纤传感技术具有分布式和长距离检测等特点，且传感光纤极易植入到成型工程构件中，在线形工程 构件的监测和检测中具有独特优势。介绍了布里渊光时域反射计（BOTDR）的传感原理及预制桩传感光纤的植入工艺， 给出了基于分布式应变模式下桩身变形和内力的分析方法和计算公式，并结合实例对测试误差来源进行了分析。研究 表明：采用开槽粘贴布纤的铺设工艺，实现了预制桩分布式光纤应变测试，可获得桩身轴力、侧摩阻力及桩端阻力的 分布特征，简化和完善了预制桩的内力测试工作。测试精度可通过设置参比光纤、提高定位精度、完善铺设工艺及滤 波去噪等方法进行提高。 关键词：预制基桩；桩身内力；布里渊光时域反射计；分布式检测 中图分类号：TU473 文献标识码：A 文章编号：1000–4548(2009)06–0911–06 作者简介：魏广庆(1979– )，男，江苏南京人，博士研究生，从事光纤传感技术在岩土工程监测中应用研究。E-mail: gqwei_nj79@https://www.doczj.com/doc/a27207104.html,。 Application of distributed optical fiber sensing to testing inner force of prefabricated piles WEI Guang-qing1，SHI Bin1，JIA Jian-xun2，HU Sheng1，LI Ke1，ZHANG Dan1 (1. Center for Engineering Monitoring with Opto-Electronic Sensing of Nanjing University, Nanjing 210093, China; 2. Shanxi Electric Power Exploration and Design Institute, Taiyuan 030001, China) A bstract: The distributed optical fiber sensing technique has unique advantages in monitoring and inspecting of linear engineering, such as long distributed sensing and being easy to be fixed in the molded structures. The basic principle of the Brilliouin optical time domain reflectometer (BOTDR) and the technique to fix the sensing optical fiber in prefabricated piles are presented. The formulas for the distortion and internal force of the piles under the distributed strain mode are deduced, and the test results and the origin of the test error are analyzed through practical examples. The research results show that the pile strain distribution tested by the sensing optical fiber, laid in the prefabricated piles by slotting and sticking it with epoxy, can help to obtain the pile axis force, skin friction, end-bearing resistance and pile bearing features. The test error can be eliminated by setting comparative optical fiber, raising position-setting precision, consummating the sensing techniques, filtering wave, and denoising, among others. Key words:prefabricated pile; pile inner force; BOTDR; distributed sensing test 0 引 言 基桩内力测试是了解桩土作用规律及荷载传递特性最为可靠的途径，为了完成此项测试工作，需要在桩身不同部位埋入应变或应力类传感器件。由于预制桩一般采用特殊工艺制作而成，预应力管桩还要经过钢筋预拉、离心旋转及高温养护等工序制作而成，因此很难将传感器在制作桩时预埋设入桩中。预制桩在施工过程中，桩与周边土石发生很大的摩擦，粘贴在桩表面的应变计及其导线很难成活下来[1]。采用事先内置钢板和管件等特殊方法可使得应变计成活率大幅提高[2]，但是这些方法需在制作时作特殊处理，而且各种钢板和管件的植入也改变了桩身的完整性和力学属性，使测试结果不能客观反应桩身内力的实际情况，因此需要寻求一种新的测试方法来完善和简化预制桩的内力测试。 分布式光纤传感技术以普通光纤为传感和传输介质，无需其他外置传感器件，且光纤纤细柔韧，很易植入到构件体内或外表，并与监测构件变形协调一致，在众多成型工程构件监测中得到广泛应用[3-4]。通过其─────── 基金项目：国家自然科学基金项目（40702045）；国家教育部重点项目（01086） 收稿日期：2008–04–03