In this paper, a whisker array sensor for object surface shape measurement is designed and experimentally demonstrated. The developed sensor is based on a 4×4 whisker array with fiber Bragg grating, which imitates the structure of the facial whiskers of animals like mice and dogs. The surface shape reconstruction is based on the curvature information of each sensing point by measuring the wavelength shift of each fiber Bragg grating fixed on the whisker. The conversion coefficient between wavelength shift and bending curvature is obtained then the change of fiber Bragg grating is converted into corresponding bending curvature. The measurement error on the altitude of the whisker of each sensing point is about 1.2%. By curve fitting the curvature information of the whole fiber Bragg grating whisker array, the surface shape of the target surface is reconstructed. In this experiment, the spatial resolution of the sensor is 10 mm, which can theoretically meet the need of any spatial resolution by adjusting the measurement algorithm. The design successfully realizes surface shape sensing, which has important practical value in the field of robot tactile, in aviation and disaster relief.
In this paper, a novel Double-Deviations mathematical model and Uniform Design Method for flattop all-fiber MZI interleaver is proposed. It provides an innovative, versatile and practical solution for the design of cascaded MZI filters. Obtain the parameters of the all-fiber comb filters by constructing the uniform design table, then the scheme is numerically simulated and verified in three different structures. When evaluating the performance of flattop all-fiber interleave , a new goodness-of-fit criterion named "double difference function of the optical comb transform output spectrum and the target square wave" was established. It can adequately consider the information provided by evaluation index of the output waveform. The geometrical significance of Double-Deviations and the convergence proof of function sequence based on it is described and analyzed. The preliminary numerical simulation results show that the flattop all-fiber MZI filters designed under Uniform Design Method have optimum performance. When compared with the output waveform obtained by the traditional algorithm, the scheme proposed has less calculation time, high approximation accuracy, flatter pass-band and stop-band of the filter, whose advantage is highlighted obviously for solving high dimension parameter optimization problem in the optical fiber field.
The edge demodulation structure consisting of a micro-ring resonator and an asymmetric M-Z interferometer is proposed and investigated for applications in sensing system. According to the linear conversion between wavelength and intensity in the demodulation principle, the parameters affecting the linear region of spectral response are analyzed theoretically. Numerical analysis shows that the ratio of δ to ΔΦ is 0.5 is the best premise to realize wavelength demodulation. The accuracy decreases with the increase of coupling coefficient K, but the demodulation range is improved. The change of coupling angle k1 and k2 makes the waveform shrink according to a certain rule, thus changing the detection sensitivity. Meanwhile, the demodulation performance improves as the transmission factor α increases.
IGBT is a high-power device used in the field of power electronics. Its internal temperature rise will lead to module failure, which will seriously affect the safe operation of high-voltage converter systems. At present, mature methods used in IGBT failure detection are limited to indirect analysis through current and voltage, and less to real-time measurement of internal temperature distribution and thermal conduction state. In this paper, a fiber grating sensing system is introduced in the silica-gel layer inside the IGBT. We design and build a fiber grating sensor system for real-time monitoring of the IGBT internal temperature distribution and the thermal conduction state of the silica-gel, and it is monitored online in the incubator, laboratory and operating conditions. The system has been running in Xiamen Ludao ±320kV flexible DC converter station demonstration project for five months. The results show that the system has strong stability and fast response time, and the data acquisition can be synchronized with IGBT temperature changing. It provides a reliable basis and timely alarming for the fault detection.
To solve the problem of cross sensitization when the strain and the temperature are measured at the same time, we
propose a structure of a ditrigon cantilever beam of uniform strength, realize a sensor structure in which the strain and
the temperature can measured at the same time by a single fiber grating. The beam is bended and elongate the grating
sticked on the surface of the beam, the reflectance spectrum from the grating is splitted into a double-peak spectrum. The
strain can be measured by the space of the double peak. The variation of temperature is converted into the whole
displacement of the reflectance spectrum.
The XPM technique is applied to the demodulation system for fiber grating sensor for the first time in this thesis.
According to XPM principle, the intensity of accessorial light can be altered by feedback control and the phase of the
light signal from the M-Z interferometer can be modulated in a phase-locked way, thus the system phase-difference can
be locked at the point of the highest sensitivity. It resolves the precision non-linearity of interferometric demodulation,
the limit of very small range for demodulating, the non-linearity of the demodulating sensitivity, the affect of backlight
and undercurrent pair in the demodulating circuit, the delay-effect by PZT tune and the error from the machine.
All-optical switching based on cross-phase modulation using Bragg grating in the highly nonlinear photonic crystal fiber
(PCF) is investigated numerically. Differential method is used in the simulation process. The numerical solutions of the
coupled-mode equations which describe all-optical switching are presented. Switching characteristics influenced by
different pump shape and pump power are analyzed. Furthermore, switching characters of using Bragg grating in a
highly nonlinear photonic crystal fiber and in a conventional one are compared.
KEYWORDS: Phase modulation, Radio optics, Dispersion, Modulators, Radio over Fiber, Modulation, Microwave radiation, Signal detection, Eye, Telecommunications
We have theoretically investigated the transmission performance of the optical microwave up-conversion link by using a
phase modulator and a dispersive fiber (standard single mode fiber). A theoretical approach has lead to the evaluation of
the influence of dispersion on the 60 GHz radio-over-fiber (ROF) links. According to our theoretically analysis, the data
signals carried by optical millimeter (mm)-wave after transmission along fiber suffer not only from fading but also from
the time shift of the code edges due to the fiber dispersive, which limits the transmission distance of the optical mm-wave
signals. The simulation results agree well with our theoretical analysis.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.