Accurate measurements of forces applied to the optical cable reels with high spinning speeds, will render information on the breakdown of optical fibers, and thus improve the odds of success and un-winding efficiency. In this paper we analyze and deduce the cable wire stress at high pay-off speeds. A high-sensitive opti-mechanical testing sensory device is designed to measure both the axial tension of the cables and the radial pressure of the cable reels at varying stress points simultaneously. The time resolution of this new device is less than 0.015ms, the response time is up to 15μs, and its sensitivity is about 500pc/N, which satisfies the mechanical testing requirements at high spinning speeds. In addition, the spinning speed of 260m/s led to the break-down of the optical fibers, and the spinning speed of 250m/s tested finally led to a deceleration near the end of the broken fibers. It is obvious that this kit can meet the requirement to obtain the periodic signals of the varying forces for each layer and each turn of optical fiber cables. Moreover, we found that the pay-off fiber cable is safe with the unwinding speed of 250m/s and the break-down of optical cables happens during the deceleration process. However, it is under the unwinding speed of 260m/s that pay-off fiber cables broke during the experiment. The abnormal breakdown signals are captured at these unwinding speeds, respectively.
In the process of the high speed pay-off of the optical fiber cables, there are some problems unsolved such as testing the broken fibers or cables, monitoring the working states of the pay-off, and so on. In this paper, in order to solve these problems, a kind of dynamic testing technology to test the bending losses and the bending parameters of optical fiber pay-off cables based on the dual-wavelength, at the high pay-off speed, is proposed. Using the dual-wavelength method, the distribution of bending radius and bending length near the stripping points of the fibers on the optical fiber cable steel can be inversed by the difference of the bending loss index. On the other hand, a kind of dynamic dual-wavelength testing device is designed and developed, which is of broad band and high sensitivity and can obtain the periodic signals of the cable loss index with the changing of strong bending in real time. Besides, the static and dynamic calibration devices are designed, and the relationship between the two calibration methods is also established. Furthermore, the relationship between the curvature radius and the strong bending losses when the curvature radius is less than 6mm and the relationship between the bending length and the loss is studied experimentally. The results show that it has fast time response, strong anti-interference ability and high sensibility. There is obvious difference of the bending states between the scanning interval and the retrace interval, and the loss in the retrace interval increases greatly more than in the scanning interval. It is important to note that the minimum curvature radius of the strong bending cable is about 0.5mm at the speed of 200m/s. Our work will be beneficial to analysis the process and the mechanism of the fault of the fiber broking, as well as the fiber communication, fiber sensor, and so on.
In order to study and improve atmospheric and air pollution monitoring sensor, a new
mathematical model of random signals is established based on measuring process of light
scattering signals analyzed by laser particle counter which combines the high speed data
acquisition card PCI-9812 and optical particles counting sensor. The measured random signals
can be divided into stability constant part and random variation part. The performance of the
instrument is improved by both this model and analytical methods. Statistical distributions of the
amplitude of the standard particles with different diameters are studied by the original experiment
and improved one. The resolving power of particle size could attain more than 90%. The results
reveal statistical distributions match well with lognormal distribution with a natural number as an
independent variable. The lognormal distribution plays an important role in describing the
random fluctuation characteristics of random process in both theories and experiments.
Furthermore, both normal and lognormal distribution fitting are applied in analyzing the
experimental results and testified by chi-square distribution fit test and correlation coefficient for
comparison.
Electrical effect induced by laser plasma in air is measured using a tiny probe placed in close to a metal target. Analysis shows that the resulting signal wave varies with detection distance. Based on the testing system, an equivalent circuit model was proposed to analyze the formation mechanism and evolution of the electrical signal and its dependence on the probe distance. The observed signal peak polarity overturn was also analyzed and explained. Finally, our method provides an explanation for the effects of the testing angle on the probe signals according to the time and space evolution of the laser plasma.
On the basis of electromagnetic theory, the scattering light intensity from a series of dielectric surfaces
with different roughness is calculated by using monte-carlo method and the boundary condition of
Kirchhoff approximation. The geometry profile of rough surfaces obeys Guass distribution and all of
the surfaces have the same corelation length. With the increasing of rms height, the width of diffuse
scattering intensity distribution, the attenuation of scattering peak value and its moving to the normal
direction are observed. After theoretical analysis, it is obtained that the statistical distribution of the
local slope varies with the rms height and reflecting index of these local slope are the main reasons for
these phenomenon.
A model of the random background noise acting on particle signals is established to study the impact of the background
noise of the photoelectric sensor in the laser airborne particle counter on the statistical character of the aerosol scattering
pulse signals. The results show that the noises broaden the statistical distribution of the particle's measurement. Further
numerical research shows that the output of the signal amplitude still has the same distribution when the airborne particle
with the lognormal distribution was modulated by random noise which has lognormal distribution. Namely it follows the
statistics law of invariance. Based on this model, the background noise of photoelectric sensor and the counting
distributions of random signal for aerosol's scattering pulse are obtained and analyzed by using a high-speed data
acquisition card PCI-9812. It is found that the experiment results and simulation results are well consistent.
In this paper, the transposition process of the polarization of light state is described by the
Stokes-Mueller formula, according to which the depolarized capability of the p-polarized light by
rough surfaces is discussed. The values of M11/M00 in Mueller matrix of the typical targets' surfaces
are measured by experiment. The results indicate that the value of M11/M00 decreases with the
increasing of surface roughness, which implies that the depolarized capability of the p-polarized light
increases. Besides, the values of M11/M00 of metal targets are larger than 0.61, while the values of
camouflage cloth, wooden plates and cement boards are all less than 0.3, which provides a possible way to detect metal targets by polarization imaging.
In order to accurately measure counting efficiency of laser airborne particle counter, the characteristics and shortages of
the signal amplitude response functions of domestic instruments were analyzed firstly. Then the design of performance
optimization for optical sensors was developed through using sheath air inlets to replace the original inlets, which can
cause the signal amplitude response functions to be described by the normal distribution. Base on these, a new method
for calculating counting efficiency was presented. Through analyzing the relation between signal amplitude response
function and coordinate origin, the counting efficiency for mono-disperse particles can be confirmed. If the signal
amplitude response function intersected with the coordinate axis, fitting the incomplete curve into the complete curve
using non-linear Least Square Method, then the counting efficiency can be defined as the ratio of the included area of the
incomplete curve to the complete curve. If the whole signal amplitude response function totally diverged from the
coordinate origin, it proved that the counting efficiency of mono-disperse particles was up to 100%. The theory and
experiments prove that this method is simple, useful and practical. It also offers the clear guidance direction for
appraising performance of the instrument.
Antiresonant guiding microstructured optical fiber (MOF), a new kind of photonic band gap fiber, has several attractive applications including tunable filters, optical modulators and sensors. This new kind of photonic bandgap fiber with low refractive index core surrounded by a finite lattice of high refractive index inclusions reveals several intriguing properties, which are mainly determined by the individual properties of high refractive index inclusions rather than their positions and number. In this paper the dispersion properties of these fibers with hexagonal lattice of cylindrical high refractive index inclusions are discussed based on a full vector multipole method. The influences of inclusion space, inclusion rings number and core size on dispersion properties are investigated with photonic band gap location almost unchanged by keeping the diameter and refractive index of the high refractive index inclusions fixed. In order to evaluate the dispersion property dependence on high refractive index inclusions, the comparisons between fibers with different diameters or refractive indexes inclusions are also done. Numerical results show that the waveguide dispersion can be adjusted in a wide range for individual band with the bandgap location almost unchanged. It is confirmed that the dispersion is more susceptive to inclusion space and fiber core size than inclusion rings number. Individual properties of high refractive index inclusions can affect not only the location of band gaps but also the dispersion properties remarkably. This research is useful to optical fiber communication, fiber nonlinear applications and tunable device designs.
The light scattering signal amplitude distribution of aerosols, which was measured by the single particle counting
technique, was applied to calculate aerosol mass concentration using an inversion algorithm. Therefore, how to
accurately extract the information of the signal amplitude distribution is a crucial problem for aerosol mass concentration
inversion. In view of mass concentration inversion accuracy and stability are related to information extraction methods,
the linear and non-linear segmentation methods were presented. Experimental results indicate the information entropy of
the signal amplitude distribution obtained by the non-linear segmentation method is clearly larger in the same number of
signal subsets, and when inversion accuracy achieves stability, the ratio of information entropy to the number of signal
subsets is also larger than that of the linear segmentation method, leading to rapid stability of inversion accuracy. The
study of the information entropy characteristic of the signal amplitude distribution of aerosol provides theoretical
guidance for the circuit design of an optical particle counter.
Laser shock cleaning (LSC) has been proved an effective method to clean sub-micron and micron particles from solid surface during last five years. In this report, dynamics of the interaction between plasma shock wave and adhered spherical particles is analyzed in theory, considering the change of particle contact radius induced by the load of the shock wave. Analysis of the rolling mechanism at the initial contact of the shock wave with particles shows working gap has a serious influence to the cleaning and smaller diameter particles are more difficult to be removed with smaller cleaned area. Moreover, particle energy obtained from the shock wave is analyzed through which particle removal trace and cleaned area are studied combined reflection shock wave and irregular turnover of the particle into account. Removal of micron copper particles on a silica surface in air is experimented at different working gap. Results show that particles can be effectively removed within the suitable working gap, i.e., 0.8 mm for 150 mJ explosion energy, and higher working gap represents poorer cleaning efficiency. Moreover, the cleaning situation of the heavy contamination shows out an interesting phenomenon of the cleaned area (0.4cm2) profile that is an ellipse caused by the non-uniform pressure distribution of plasma shock wave.
KEYWORDS: Mirrors, Plasma, Wave propagation, Signal attenuation, Pulsed laser operation, Laser ablation, Iron, Space mirrors, Signal detection, Signal processing
A novel method, namely, fiber-coupling zig-zag beam deflection method has been proposed to investigate the attenuation
of plasma shock waves in air in this paper. The main innovation of this method is to use a zig-zag laser beam as the
probing beam, instead of a straight beam in traditional beam deflection method. The zig-zag beam is formed by eight
times successive reflections on a pair of parallel mirrors. Shock waves propagate through the space between two mirrors
which contains nine zigzags in the horizontal plane. This space can be designated as the testing field. After the probing
beam leaves the testing field, it is coupled into a single mode optical fiber which guides the beam into a photomultiplier
to complete the process of photoelectrical conversion.
Plasma shock waves are generated during laser ablation of Fe target in air. The laser used in our experiment is a Qswitched
Nd: YAG laser operating at wavelength of 1064nm and pulse width (FWHM) of 7ns. The output of
160mJ/pulse of this laser is focused on the surface of the target which is far exceeds the ablation threshold of Fe. When a
shock wave propagates in the testing field, it will meet the zig-zag probing beam nine times one after another.
Correspondingly, nine deflection signals will be induced by the perturbations of the shock wave, which can be utilized to
illuminate the propagating behavior of the shock wave. The whole attenuation process of the shock wave can be
demonstrated intuitively only through one experimental curve with the nine deflection signals. From the curve, the
average velocity of the shock wave can be calculated out with high and reliable precision. It is found that shock waves
attenuate into acoustic waves within 10mm in air because of the inhalement of environmental media. The development
of this novel optical technology provides a powerful tool for the detection of shock wave propagation and riches
diagnostic methods of shock waves.
A new feature of relationship between macro-bending losses and bending length of mono-mode fibers is found experimentally: when bending radius is 4mm nearly no loss is detected on the condition that bending angle is less than 20 degrees. The similar phenomena happen when bending radius is 3mm or 2mm. The turning bending degree that bending losses will increase rapidly is called critical angle by us. The result will give us some new clues that how the bending losses change with bending length on earth. And some theoretical work should be done to explain the phenomenon.
There are a few difference in the characters of the optical sensors of the particle's counter when it is been making because of the technical difference between the sensors. So, the criterion must been used for the sensors. In the traditional method, only one or two kinds of the standard particles is used as criterion because that the continual function of distribution of the particles can not be gotten from an old data processing method. That is to say there is not reflected absolutely for the characters of the sensor itself because of the non-linearity and continuity of the distribution. And than, the effecting of the criterion of the counter is weakening greatly. In this paper, a new infinite channels concept and a probability function are put forward, through which, the continual distribution function of the particles can be gotten by using the technology of the A/D conversion, coding channels, data address and sum. Three kinds of the distribution function of the standard particles are used as criterion, the criterion can be completed through the comparing the standard function and real-measuring function. At last, the debugging is very simple in the Electro-circuit instead of the optics and the effect of it is enhanced greatly.
A theoretical and experimental study is conducted to investigate applicability of a single-mode fiber ultrasonic sensor for detecting the shock-wave in optical breakdown in air induced by a high power laser pulse. The sensor is based on the ultrasonically induced modal birefringence which alters the polarization state of the optical beam propagating through the fiber. The shock-wave signals have been gotten by using the sensor. It is shown that the single-mode fiber sensor has enough sensibility to detect shock-wave in air, but it is dependent on the fiber- ultrasonic interaction length and the intensity of shock- wave.
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