In the paper, we propose one new type sensor with light modulation method. Having learned to delay a light signal by means of optical fibers, the temperature field may be detected by this way. According to the light speed which can be modulated in a photorefractive material in which written steady volume-index grating by two laser beams in opposite direction, the light signal may transmit with phase modulating due to intervening of another frequency shifting laser beam. In the experiment, the inner grating would be written in an optical fiber in which suitable Stannum has been doped. The periodic structure in the fiber can make the light signal reflect and the value of phase shift corresponds to the effective length of the periodic grating. According to magneto-optical Faraday effect, temperature may changes polarization direction by shifting Verdet constant. During testing period, a Sn-doped fiber is exposed to measured temperature environment and certain uniform steady field. Under this environment, the more the temperature increases, the shorter the effective interference area is in the fiber. Comparing with light delayed signal that transmits through fiber with different temperature, the delaying value may be corresponded to temperature. This research work is supported by the National Natural Science Foundation of China under grant No.60472023.
Mostly, the principle of FGB strain sensor is to detect the shift of the central wavelength of FBGs. Now, we propose a new strain sensor using light speed extraordinary controlled method in a periodic structure modulated optical fiber. According to light speed which can be modulated in a photorefractive material in which written volume-index grating by two laser beams in opposite direction of fiber, the light signal may transmit with phase modulating due to intervening of another frequency shifting laser beam. In the experiment, the inner grating would be written in an optical fiber in which suitable little Stannum has been doped. Based on quantum theory, the energy-band structure has a zero slope at the edges of Brillouin zone and the group velocity of photons at the band structure of a periodic structure is zero. Due to the effect of stress, optical principal axle rotation angle of each beam is shifted, inducing the inner effective grating changed. During the testing period, pressure is put to a point of the fiber and fiber would be partly in uniform magnetic field. Under this environment, according to elasto-optical effect and magneto-optical effect, the pressing position and pressure value can be determined. This research work is supported by the National Natural Science Foundation of China under grant No.60472023.
Under special environment, usually the magnetic intensity must be tested with full optical system. The purpose of the paper is to present theoretical analysis about testing magnetic parameter using light speed modulating and indicate the advantages to obtain new method of optical test. According to the light speed can be modulated in a photorefractive material in which written steady volume-index grating by two laser beams in opposite direction, so as to the light signal may transmit with phase modulating because of the intervening of another frequency shifting laser beam. In the experiment, the inner grating would be written in an optical fiber in which the suitable little Stannum has been doped. The periodic structure in the fiber can make the light signal reflect and the value of the phase shift is corresponding to the change of the periodic structure. With the quantum theory, the energy-band structure has a zero slope at the edges of the Brillouin zone and the group velocity of the photons at the band structure of a periodic structure is zero. According to the magneto-optical effect, the magnetic field may make the polarization plane change. After the two laser beams come into two ends of a fiber, the magnetic field can make their polarizations direction rotate and the interfering effect should be decreased simultaneously. During the testing period, a Sn-doped fiber is exposed to a magnetic field with linear distribution. Under this environment, the more increasing of magnetic intensity, the shorter length of effective steady grating in fiber is. Compared with light delayed signals transmitting through fiber in or not in the magnetic field, the delaying value may be correspondent to average magnetic intensity. This research work was supported by the National Natural Science Foundation of China under grant No.60472023.
During some special processing or under the special environment, usually the magnetic intensity must be tested with full
optics system. According to the light speed can be modulated in a photorefractive material in which written
volume-index grating by two laser beams in opposite direction, so as to the light signal may transmit with phase
modulating due to intervening of another frequency shifting laser beam. In the experiment, the inner grating would be
written in an optical fiber in which the suitable little Stannum has been doped. The periodic structure in the fiber can
make the light signal reflect and the value of the phase shift is corresponding to the change of the periodic structure. With
the quantum theory, the energy-band structure has a zero slope at the edges of the Brillouin zone and the group velocity
of the photons at the band structure of a periodic structure is zero. According to the magneto-optical effect, the measured
magnetic field may make the polarization plane change. After the two laser beams come into two ends of a fiber, the
magnetic field can make their polarizations direction rotate and the interfering effect should be decreased simultaneously.
During the testing period, a Sn-doped fiber is exposed to a magnetic field with linear distribution. Under this
environment, the more increasing of magnetic intensity, the shorter effective interference area is in the fiber. Comparing
with the light delayed signal that transmits through fiber that in or not in the magnetic field, the delaying value may be
corresponded to the average magnetic intensity. The output signal light could be processed by various smart way. This
research work was supported by the National Natural Science Foundation of China under grant No.60472023.
In the paper, we propose one new type sensor with using light modulation method. Having learned to delay a light signal
by means of optical fibers, the temperature filed may be detected by this way. According to the light speed can be
modulated in a photorefractive material in which written steady volume-index grating by two laser beams in opposite
direction, so as to the light signal may transmit with phase modulating due to intervening of another frequency shifting
laser beam. In the experiment, the inner grating would be written in an optical fiber in which the suitable Stannum has
been doped. The periodic structure in the fiber can make the light signal reflect and the value of the phase shift is
corresponding to the effective length of the periodic grating. According to magneto-optical Faraday effect, the
temperature may changes polarization direction by shifting the Verdet constant. During the testing period, a Sn-doped
fiber is exposed to measured temperature environment and certain uniform steady field. Under this environment, the
more increasing of temperature, the shorter effective interference area is in the fiber. Comparing with the light delayed
signal that transmits through fiber with different temperature, the delaying value may be corresponded to the temperature.
This research work was supported by the National Natural Science Foundation of China under grant No.60472023.
The principle of the most of the FGB strain sensor is to detect the shift of the central wavelength in FBGs. Now, we
propose a new strain sensor using light speed extraordinary controlled method in a periodic structure modulated optical
fiber. According to the light speed can be modulated in a photorefractive material in which written volume-index grating
by two laser beams in opposite direction of fiber, so as to the light signal may transmit with phase modulating due to
intervening of another frequency shifting laser beam. In the experiment, the inner grating would be written in an optical
fiber in which the suitable little Stannum has been doped. With the quantum theory, the energy-band structure has a zero
slope at the edges of the Brillouin zone and the group velocity of the photons at the band structure of a periodic structure
is zero. Due to the effect of stress, the optical principal axle rotation angle of each beam is shifted, inducing the inner
effective grating changed. During the testing period, pressure is put to a point of the fiber and fiber would be partly in
uniform magnetic field. Under this environment, according to the elasto-optical effect and magneto-optical effect, the
pressing position and pressure value can be determined. The output signal light could be processed by various smart way.
This research work was supported by the National Natural Science Foundation of China under grant No.60472023.
KEYWORDS: Crystals, Laser crystals, Modulation, Signal processing, Stereolithography, High speed photography, Electromagnetic radiation, Argon ion lasers, Modulators, Signal detection
During some high processing, such as high-speed photography and so on, the encode pulse or driving signal must be
compressed with full optics system. According to the light speed can be slowed down in a photorefractive crystal bar in
which written volume-index grating by two laser beam, so as to the light signal may be transmitted in slow speed under 1/
7 of light speed in vacuum. Because the genesis of the phenomenon is the inner index periodic structure, so the out put
signal compressed may be realized through erasing the periodic structure in the opposite direction of signal beam using
another laser beam when the signal light transmitting the crystal bar. However, every finite signal stream can be further
compressed by the same way again. Different erasing method would get many kinds of out put signal to adapt to various
design.
During some high precision measuring, the LD light beam on frequency modulating would be carried time marks using frequency, such as FMCW test system. In this system, the frequency is shifted usually by changing the injection current of a LD. In the same time, the intensity of the laser beam must be changed. This change have no use for the test. In our experiment, the intensity change can be controlled by a modulator through electronic circuits according to a high speed response detector. This is a closed-loop control system using opti-electronic method, but not a signal clipper. Then, the laser beam can be modulated on intensity through another modulator to carry available signal in the measuring system for another testing value.
Laser direct forming experiments were carried out systematically with 316L stainless steel and nickel-base alloy to investigate the technical characterizations deeply and some metal components were fabricated. It is found that, the height of single cladding layer, which was affected by almost all the processing parameters and was quite hard to be precisely controlled, was very important to laser direct forming for not only the accuracy of vertical direction but also the fabrication stability. The variation of the width of single clad, which was mainly affected by laser power, spot diameter and scanning velocity, was similar to that in laser surface melting. The surface quality was another important characterization for laser direct forming and was remarkably affected by oxidation and powder attachment. In order to improve the surface quality, the flow flux ofshielding gas should not less than 10l/mm.
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