In this paper, a FMF sensor with double gourd structure is prepared. The transmission spectrum and mode changes of double gourd structure with different lengths are studied, the temperature sensitivity and linearity of the sensor are analyzed. Five sensors with different FMF lengths are prepared. The waist-enlarged spacing are 0.7cm, 1.0cm, 1.3cm, 1.6cm and 1.9cm, respectively. The FMF length are 4.1cm, 5cm, 5.9cm, 6.8cm and 7.7cm, respectively. The experimental results show that the highest temperature sensitivity of FMF sensor is 86.95pm/℃. There is no one-to-one correspondence between the temperature sensitivity and the length of the sensor.
A accurate position method for distributed fiber grating system based on code division multiplexing technology is proposed. In this paper, by using the fiber grating characteristics and code division multiplexing technology, the system are optimized. By designing delay interferometer, the optical signal modulation and demodulation are gained , which effectively improve the system's signal to noise ratio. Through the simulation experiment, the positioning detection is realized by discriminating the fiber gratings at different positions on the optical fiber. Experiments were carried out on 6m and 2.2km optical fibers respectively, the preliminary results proved the correctness and feasibility of the method.
A high sensitivity strain sensor based on cascaded cladding mode resonant double-clad fiber (DCF) and simple mode fiber is proposed. The basic principle of the sensor is analyzed, and the preparation of the sensor is performed. In different length of double-clad fiber, the strain sensing characteristics are analyzed detailedly. Experimental results show that, as the length of the connected double-clad fiber increases, the trough of the resonant spectrum will gradually increase. That is, the length of the access DCF is inversely proportional to the free spectral range. With the increase of tensile force, the resonance spectrum is blue shift, and the tension sensitivity can be up to -1.87nm/mε.
Combining with the characteristics of disciplines and OBE mode, also aiming at the phenomena of low learning enthusiasm for the major required courses for senior students, the course of optical fiber sensing was chosen as the demonstration for the teaching mode reform. In the light of "theory as the base, focus on the application, highlighting the practice" principle, we emphasis on the introduction of the latest scientific research achievements and current development trends, highlight the practicability and practicality. By observation learning and course project, enables students to carry out innovative project design and implementation means related to the practical problems in science and engineering of this course.
In view of the current poor learning initiative of undergraduates, the idea of creating a good learning environment and motivating active learning enthusiasm is proposed. In practice, the professional tutor is allocated and professional introduction course is opened for college freshman. It can promote communication between the professional teachers and students as early as possible, and guide students to know and devote the professional knowledge by the preconceived form. Practice results show that these solutions can improve the students interest in learning initiative, so that the active learning and self-learning has become a habit in the classroom.
KEYWORDS: Scientific research, Charge-coupled devices, Optoelectronics, Electronics, Video processing, Video, Signal processing, New and emerging technologies
The CCD principle and application course is professional and comprehensive. It involves many subject contents. The course content includes eight aspects. In order to complete the teaching tasks within a limited time, improve the classroom teaching quality and prompt students master the course content faster and better, so the multidimensional interactive classroom teaching is proposed. In the teaching practice, the interactive relationship between the frontier science, scientific research project, living example and classroom content is researched detailedly. Finally, it has been proved practically that the proposed multidimensional interactive classroom teaching can achieved good teaching effect.
A refractive index sensor based on taper Michelson interferometer in multimode fiber is proposed. The Hydrofluoric acid corrosion processing is studied in the preparation of single cone multimode optical fiber sensor. The taper Michelson interferometer is fabricated by changing corrosion time. The relationship between fiber sensor feature and corrosion time is analyzed. The experimental results show that the interference spectrum shift in the direction of short wave with the increase of the refractive index. The refractive index sensitivity can reach 115.8008 nm/RIU. Thereby, it can be used in detecting the refractive index in different areas including the environmental protection, health care and food production.
In this paper, a refractive index insensitive PbS fiber temperature sensor based on Sagnac interferometer is proposed. Firstly, the sensing mechanism of refractive index and temperature is analyzed. Then a large amount of sensors with different length are fabricated. Comparing the transmission spectrum of these sensors, the PbS fiber with the length of 4mm and 10mm are chosen for sensing experiments. Finally, the experiment platform is established to measure temperature and refractive index. Under the condition of different temperature and refractive index, the relationship between the interference spectrum, temperature and refractive index is analyzed, respectively. In temperature experiment, the temperature range is 30℃-65℃. The experimental results show that the interference spectrum is red shifted. When the PbS fiber length is 4mm, the temperature sensitivity can be up to 78.23pm/℃. When the PbS fiber length is 10mm, the temperature sensitivity is 59.16pm/℃. The refractive index range is 1.3525-1.4505 corresponding to the glycerite solution concentration of 10%-80%. The experimental results show that there is no wavelength shift in the interference spectrum. So this PbS fiber sensor is almost insensitive to refractive index.
A tension sensor of Photonic Crystal Fiber(PCF) is presented based on core-offset splicing and waist-enlarged fiber taper. The tension response characteristics of the sensor are studied experimentally. To analyzing the modal interference, many samples with different PCF lengths between the two splicing areas, different core-offset distances and different waist-enlarged fiber taper diameters are fabricated and tested. When the tension range is 0 to 4000με, the results show that the spectrum is blue shift with the increasing of the axial tension. The sensitivity is-2.1 pm/με. The experimental results show that the tension sensitivity can be not influenced by the PCF lengths, the core-offset distances.The waist-enlarged fiber taper diameters and the tension sensor is very sensitive to axial tension and the relationship between the wavelength shift and tension is linearity. To determine the number of the interfering modes, the transmission spectra of these sensor is transformed by the fast fourier transform (FFT) method. There are several peaks in the spatial frequency spectra at these sensors. Only one cladding mode is dominantly excited, while the other cladding modes are weak. The spatial frequency is proportional to the differential mode group index. Compared with the traditional fiber sensor, this sensor has some advantages including the easily fabricated, simple structure and high sensitivity. It can be used in industrial production, building monitoring, aerospace and other fields.
In order to improve the equilibrium between fiber sensor performance and cost, a curvature sensor based on Few Mode Fiber(FMF) is proposed. A length of FMF is spliced with waist enlarge between two Single mode Fibers(SMFs) to form two spherical- shape structure. Fiber core mode interfere with clad mode due to the excite and couple function of spherical-shape structure, respectively. The phase difference between the cladding and core regions of the fiber changes with the external strain increase, and then the interference spectrum changes. Two sensors with different length of FMF are fabricated, and the transmission spectrum are obtained. The result shows the optical power at certain wavelength is increasing with the curvature increasing. When the curvature range is 0~0.42m-1 and the FMF is 5.7cm, the curvature sensitivity can be 11.22dB/m-1. When the FMF is 5.9cm, the curvature sensitivity can be climbed to 14.08dB/m-1.
A refractive index insensitive curvature sensor based on cladding-mode resonance of specialty triple-clad fiber (STCF) is proposed. The corresponding mode properties of STCF are investigated theoretically based on the coupled mode theory. The different mode dispersion curves are calculated and a resonance wavelength is obtained. A straightforward experiment is performed to prove the curvature sensitivity. Experimental results shows that the curvature sensitivity can be achieve -11.03374nm/m-1 in the range of 0~1.17m-1, and it also has good linearity. This curvature sensor has the advantages of simple structure, easy manufacturing, highly sensitivity and has no cross-sensitivity when it compared to the other sensors. Thus it can be used for curvature monitoring in time.
A fiber-optic temperature sensor based on specialty triple-clad fiber (STCF) is proposed. Based on coupling mode theory, the STCF can be equivalent to a rod waveguide and two tube waveguides. The different mode dispersion curves are calculated and a resonance wavelength is obtained. A straightforward experiment is performed to prove the temperature sensitivity. Experimental results shows that the temperature sensitivity can be achieve 97.2pm /°C in 20~90°C and there is a good repeatability. The resonance wavelength has a red shift and increase as increasing temperature. Thus, this sensor can be used for temperature monitoring in time.
A specialty optical taper is proposed for receiving optical signal. According to the geometrical optics, the coupling
efficiency for different shape curve is analyzed, such as piecewise function type, parabola type, and linear type. The
relationship between the different large endface radius, small endface radius, taper length, refractive index and coupling
efficiency is analyzed, respectively. By comparing the input and output light energy of specialty optical taper, the
coupling efficiency can be analyzed in experiment. The experimental results are in good accordance with the theoretical
data. For the ±1.5 mm radial displacement, the coupling efficiency can be more than 50% in different directions,
respectively. Finally, the errors are also given.
Fiber amplifiers such as Erbium-doped fiber amplifier (EDFA) played a key role in developing long-haul transmission
system and have been an important element for enabling the development of optical communication system. EDFA
amplifies the optical signal directly, without the optical-electric-optical switch and has the advantages such as high gain,
broad band, low noise figure. It is widely used in repeaterless submarine system, smart grid and community antenna
television system. This article describe the application of optical-fiber amplifiers in distributed optical fiber sensing
system, focusing on erbium-doped fiber preamplifiers in modern transmission optical systems. To enhance the
measurement range of a spontaneous Brillouin intensity based distributed fiber optical sensor and improve the receiver
sensitivity, a two cascaded EDFAs C-band preamplifier with an optical bridge structure is proposed in this paper. The
first cascaded EDFA is consisted of a length of 4.3m erbium-doped fiber and pumped in a forward pump light using a
laser operating at 975nm. The second one made by using a length of 16m erbium-doped fiber is pumped in a forward
pump light which is the remnant pump light of the first cascaded EDFA. At the preamplifier output, DWDM, centered at
the signal wavelength, is used to suppress unwanted amplified spontaneous emission. The experimental results show that
the two cascade preamplifier with a bridge structure can be used to amplify for input Brillouin backscattering light
greater than about -43dBm. The optical gain is characterized and more than 26dB is obtained at 1549.50nm with 300mW
pump power.
A humidity sensor is proposed for detecting air moisture content based on tapered optical fiber. According to optical
energy transmission theory, geometrical optics, the sensing mechanism of humidity sensor is described by analyzing the
evanescent field around the sensing fiber. The relationships between the dimensions and spectral characteristics of the
taper have been analyzed, respectively. The results show that the taper shape is important for designing a humidity
sensor. The experimental curves can be obtained by comparing the transimission loss and humidity, and the errors are
also given. The humidity is analyzed in different air moisture content. The humidity measurement resolution is 1% as the
measuring range varies within 50~95%. The transmision loss decreases as increasing humidity. Thus, the high dynamic
performance can allows this sensor to be used for humidity monitoring in time.
KEYWORDS: Glasses, Color difference, Charge-coupled devices, Control systems, Data acquisition, Reflectivity, Signal processing, Data conversion, Human-machine interfaces, Computing systems
A design of scanning mode coated glass color difference online detection system was introduced. The system
consisted of color difference data acquirement part and orbit control part. The function of the color difference data
acquirement part was to acquire glass spectral reflectance and then processed them to get the color difference value.
Using fiber for light guiding, the reflected light from surface of glass was transmitted into light division part, and the
dispersive light was imaged on linear CCD, and then the output signals from the CCD was sampled pixel by pixel, and
the spectral reflectance of coated glass was obtained finally. Then, the acquired spectral reflectance signals was sent to
industrial personal computer through USB interface, using standard color space and color difference formula nominated
by International Commission on Illumination (CIE) in 1976 to process these signals, and the reflected color parameter
and color difference of coated glass was gained in the end.
The function of the orbit control part was to move the detection probe by way of transverse scanning mode above
the glass strip, and control the measuring start-stop time of the color difference data acquirement part at the same time.
The color difference data acquirement part of the system was put on the orbit which is after annealing area in coated
glass production line, and the protected fiber probe was placed on slide of the orbit. Using single chip microcomputer to
control transmission mechanism of the slide, which made the slide move by way of transverse scanning mode on the
glass strip, meanwhile, the color difference data acquirement part of the system was also controlled by the single chip
microcomputer, and it made the acquirement part measure color difference data when the probe reached the needed
working speed and required place on the glass strip.
The scanning mode coated glass color difference online detection system can measure color parameter and color
difference of each transverse point on glass strip, it can also measure lengthways color stability on glass strip.
Furthermore, the measuring results can be transmitted to coated control room through intranet, so it is very useful to
improve producing technique in time. In addition, equipping necessary marking machine, this system can classify glass
board automatically based on the measuring result.
This paper uses a contact mechanics and radial crushing strength to analyze the force properties of photonic crystal fiber which is placed in the V-groove. In this paper, we calculate the stress distribution of the fiber in the V-groove under two ultimate conditions. The first one is supposed that fiber is a solid cylinder which is fabricated by isotropy material. The second one is supposed that fiber is a hollow cylinder. It is calculated that the maximal stress of the fiber is the tension. This stress is near the outer air holes which are parallel to the contact surface. Then we use finite-element (FE)approach to testify the result and calculate the maximal stress the photonic crystal fiber could hold. Finally, we present the stress distribution and the strain of the fiber.
Because the structure of Photonic Crystal Fiber (PCF) is very complex, and it is very difficult that traditional fiber fusion
splice obtains optical axial information of PCF. Therefore, we must search for a bran-new optical imaging method to get
section information of Photonic Crystal Fiber. Based on complex trait of PCF, a novel high-precision optics imaging
system is presented in this article. The system uses a thinned electron-bombarded CCD (EBCCD) which is a kind of
image sensor as imaging element, the thinned electron-bombarded CCD can offer low light level performance superior to
conventional image intensifier coupled CCD approaches, this high-performance device can provide high contrast high
resolution in low light level surveillance imaging; in order to realize precision focusing of image, we use a ultra-highprecision
pace motor to adjust position of imaging lens. In this way, we can obtain legible section information of PCF.
We may realize further concrete analysis for section information of PCF by digital image processing technology. Using
this section information may distinguish different sorts of PCF, compute some parameters such as the size of PCF
ventage, cladding structure of PCF and so on, and provide necessary analysis data for PCF fixation, adjustment,
regulation, fusion and cutting system.
A polarization maintaining fiber grating multiplexed sensors based on characteristics of some parameters such as transverse strain, longitudinal strain, temperature and rotating speed of tyre and so on is introduced in the article, and all of those are important for safe operation of cars. In addition, a novel fiber grating wavelength demodulation scheme based on the phase-shifted fiber grating is proposed. One or several spectral windows with slight line-width are unfolded in reflecting spectrum of phase-shifted fiber grating. And the location of window changes at linearly with phase-shifted change. The phase-shifted change of phase-shifted fiber grating can match with phase-shift change of multiplexed sensors through using special phase-shifted fiber grating in the demodulation systems. So we can gain some spectral windows with slight line-width in the end, which is looked upon an impulse signal, and these signals can provide convenience for searching wave peak later.
A novel unsymmetrical intrinsic Fabry-Perot fiber optic strain sensor has been developed to improve the measurement of strain for different structures. Sensing principle, structure and sensing characteristics are studied. Some kinds of the unsymmetrical intrinsic Fabry-Perot interferometric (UIFPI) strain sensor are designed and fabricated. Temperature and strain characteristic of these sensors have been tested. The experiments indicate that these UIFPI sensors possessing favorable linear static and dynamic strain characteristic. The temperature characteristics of the UIFPI strain sensors with different carrier materials are distinct and the naked fiber-optic structure sensor is not sensitive to temperature. The experimental results reveal that the sensitivity is also depended on the cavity length of the UIFPI sensor.
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