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A novel magnetic field sensor by using an optical fiber Bragg grating (FBG) cascaded by a cleaved optical fiber end, which is face surrounded with magnetic fluid (MF), is experimentally demonstrated. Through Fresnel reflection (FR) of the fiber end face, side mode suppression ratio (SMSR) of reflection spectrum of the FBG is tuned by refractive index (RI) of the MF, which is sensitivity to the external magnetic field. As a result, magnetic field measurement is successfully achieved. Compared with previously reported methods based on FR of a fiber end only, it eliminates the influence of power level fluctuation of the optical source and therefore improves the measurement accuracy and stability. Furthermore, temperature can be measured simultaneously by monitoring wavelength shift of the FBG. Published version

In this paper, a dual-parameter measurement scheme based on a fiber loop mirror (FLM) assisted reflective long period fiber grating (LPFG) is proposed and experimentally demonstrated. Due to the Sagnac fiber loop mirror, a reflective long period fiber grating was generated resulting in a compact sensing routing design. Moreover, the refractive index and temperature could be simultaneously determined through monitoring two dips’ wavelength shifts of the FLM assisted reflective LPFG. Experimental results show that the RI sensitivity of the sensor is from 34.48nm/RIU to 241.12nm/RIU in the RI range from 1.3467 to 1.4526, and the temperature sensitivity can reach 1.5274 nm / °C.

In this work, we present an optical fiber sensor system for remote refractive index measurement using the optical time domain reflectometry technique as an interrogation method, and investigate the refractive index sensibility of the sensor system in detail. The sensor system operates based on Fresnel reflection at the fiber’s end that is cleaved as a vertical planar surface. Surrounding refractive index from a long distance away can be measured easily through utilizing this sensor system. The experimental setup is simple and easy to handle. Experimental results show the feasibility of the remote measurement of refractive index. The range of this measurement can reach ~30km, moreover, to ensure its repeatability and accuracy, we retest the same sample for many times, some of which are artificially applied with disturbance. Lastly we make a comparative analysis to certify that the sensor system has a good potential to remote practical applications.

The geometric conditions of diffuse illumination, 8 degree observation, specular light include (SCI) and specular light exclude (SCE) often be employed to measure the surface color of material with different gloss value. The SCE condition is usually realized by setting light trap on the integrating sphere. However, the structure of light trap has its negative influence on the light intensity uniformity, and can led to the inaccuracy of the test results under SCE or SCI condition. Due to the different sizes of the light trap, structures of the measurement instrument will led to inter instrument agreement among the measurement of sample with different gloss. This paper designs a measuring structure to measure the SCE and SCI results simultaneously; proposes a method to calculate the 8 degree gloss value based on the SCE and SCI test result; proposes a computing modal to modify the SCI and SCE measure result based on the 8 degree gloss value, experimental verifying is also carried out. The experimental results demonstrate the structure and modified model effectively reduce the negative influence of light trap. The inter instrument disagreement caused by the geometric dimension of different light trap is significantly decreased.

This paper briefly introduces the commonly used photoelectric auto collimator structure and its working principle. A new method for calibrating the initial point of collimator CCD imagine by a pyramid prism was proposed. It consists of a two-dimension rotate instrument, a pyramid prism and a collimator. By combing with the algorithm of calculating the center position of beam spot, a more precise calibration of the initial point of the collimator CCD imagine was realized. Optical properties of the pyramid prism and its impact of initial point calibration were analysed under the oblique incidence. At the same time, effect of the manufacturing errors of pyramid prism on the calibration accuracy was analysed. Experimental data shows that the method has a good reproducibility with a relative standard deviation of less than 10%.

A brief review of recent progress in researches, productions and applications of distributed fiber Raman sensors at China Jiliang University (CJLU) is presented. In order to improve the measurement distance, the accuracy, the space resolution, the ability of multi-parameter measurements, and the intelligence of distributed fiber sensor systems, a new generation fiber sensor technology based on the optical fiber nonlinear scattering fusion principle is proposed. A series of new generation distributed fiber sensors are investigated and designed, which consist of new generation ultra-long distributed fiber Raman and Rayleigh scattering sensors integrated with a fiber Raman amplifier (FRA), auto-correction full distributed fiber Raman temperature sensors based on Raman correlation dual sources, distributed fiber Raman temperature sensors based on a pulse coding source, distributed fiber Raman temperature sensors using a fiber Raman wavelength shifter, a new type of Brillouin optical time domain analyzers (BOTDA) integrated with a fiber Raman amplifier, distributed fiber Raman and Brillouin sensors integrated with a fiber Raman amplifier, and distributed fiber Brillouin sensors integrated with a fiber Brillouin frequency shifter. Sensor networks are important components of the internet of things. The distributed optical fiber sensor network (Rayleigh, Raman, and Brillouin scattering) is a 3S (smart materials, smart structure, and smart skill) system, which is easy to construct smart fiber sensor networks. The distributed optical fiber sensor has been applied to the power grids, railways, bridges, tunnels, roads, constructions, water supply systems, dams, oil and gas pipelines and other facilities, and can be integrated with wireless networks. © (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

A refractometer based on a superimposed optical fiber grating, where a fiber Bragg grating (FBG) with broadband reflection (~2.7nm) is superimposed in the rear part of a tilted fiber Bragg grating (TFBG), is proposed and experimentally demonstrated. The superimposed grating is immersed in liquid with different refractive index. Optical power reflected back by the FBG is modulated twice by the TFBG that greatly enhances the sensitivity. And by using the broadband reflection FBG, instead of a normal FBG, signal to noise ratio is also improved.

A temperature sensor by using an alcohol-filled side-hole fiber (SHF) based Sagnac interferometer is proposed and experimentally demonstrated. The alcohol liquid is filled into air holes of the SHF. Due to its temperature-dependent refractive index, interference pattern of the Sagnac interferometer shifts at sensitivity of 86.1 pm/°C when temperature is changed in a range between 20°C and 70°C.

In this paper ,the advantages and disadvantages of the methods to achieve White LED are reviewed, and phosphor-converted white LEDs are discussed in detail. In the case of blue chip exciting YAG phosphor to get white LED, use Mie scattering theory to construct physical model, then analyze how the package, concentration, thickness and particle size of phosphor work on extraction efficiency, spatial Chroma uniformity and color temperature of white LED. The conclusion of this paper advances the application of LED solid-state light source. In the end, the paper puts forward the direction and focus of phosphor research.

Standard measuring condition of d/0 structure has been widely applied on spectrophotometer. Ordinarily, in order to eliminate the impact of light source fluctuation, the inner surface of integrating sphere is selected as reference in the design of integrating sphere system. This design ensures the temporal stability of measurement. But the reflected light of inner surface and diffuse reflection light of sample are both detected as reference signal. It greatly impacts repeatability and error of indication. This paper improves d/0 measuring condition configuration with LEDs light source, and finds the method to reduce the error considering light source and integrating sphere. Then this paper simulates the configuration and establishes experiment for it. The results indicates that this configuration can effectively revise the error which carried by the diffuse light.

In this paper, a two locking lasers BOTDR (Brillouin optical time domain reflectometry) system is demonstrated. Two narrow linewidth DFB lasers are used as the light sources. Their frequencies are locked with a frequency difference of about 11 GHz, which can greatly improve the measurement accuracy and system stability. At a 5-km standard single-mode fiber, distributed temperature measurements can be achieved in lab with a spatial resolution of 10m and a temperature resolution of 2°C.

The paper describes a fiber sensor for the evaluation of static axis strain and dynamic vibration. A section of high birefringence polarization maintaining fiber (Hi-Bi PMF) is incorporated in a Sagnac fiber loop as the sensing element. The static axis strain measurement is realized by analyzing the attenuation peak wavelength shifts and the strain sensitivity of 1.09 pm/μs is achieved. Using the power intensity demodulation method, the experimental results of dynamic acoustic vibration measurement show that it can detect the acoustic vibrations over the frequency range of 50Hz to 22 kHz.

A distributed temperature sensor (DTS) system with a sensing distance of 4 km was developed for applications in tunnel temperature measurement and fire alarm. Characteristics of DTS and experiment results are introduced. The results show that DTS system can play an important role in tunnel fire alarm.

A novel compact temperature sensor based on a fiber loop mirror (FLM) combined with an alcohol-filled highlybirefringent photonic crystal fiber (HiBi-PCF) is proposed and experimentally demonstrated. The output of the FLM is an interference spectrum with many dips, of which the resonant wavelengths are quite sensitive to temperature because the interference of the FLM is sensitive to the optical path difference due to the refractive index change of the filled alcohol. Experimental results show that the temperature sensitivity reaches up to 5.42nm/°C for a 6.3cm long alcoholfilled PCF used in the FLM.

Demodulation based on a long-period grating (LPG) in a photonic crystal fiber (PCF) with differential processing was proposed to eliminate the noise of fiber sensors and raise the accuracy of the highly-birefringent fiber loop mirror (HiBi-FLM) temperature sensor. Utilizing the property temperature insensitive and the filtering function of the LPG in PCF, the intensities of two signals located respectively within the positive and negative linear region of the LPG's transmission spectrum can be monitored simultaneously and accurately. The noise of fiber sensors is eliminated effectively by the algorithm of two signals, since the two signals (also including the noise of fiber sensors) transmit through the same way to the monitor. Experimental results show that the proposed demodulation eliminates not only all of power fluctuations in the system, but also raises the accuracy of the sensor. The value of the algorithm remains constant when the power of light source varies ±10% and the relative error between the measured temperature change and the true change is only 0.34%. Compared with the sensing without the algorithm, the accuracy increases from~90.5% to ~99.7%.

A novel temperature-insensitive tilt sensor is proposed by embedding two chirped fiber Bragg gratings (CFBGs) into a cylindrical cantilever-based pendulum in two orthogonal planes. Due to the tilt-induced nonuniform strain field applied along the length of the CFBGs, their bandwidths of reflection spectra vary with the applied tilt angle. By measuring the reflected optical powers of the two CFBGs illuminated by a flattened broadband light source, temperature-insensitive measurement of both inclination angle and direction in two dimensions can be realized. Theoretical calculations and preliminary experimental results verified the feasibility of the proposed sensor design. The measurement is in real-time manner and the sensor is cost-efficient because it is an intensity-modulated sensor.

The theory of mesopic vision provides an important theoretical foundation for the choice of road lighting sources. Based upon a number of recent mesopic photometry studies, an equation ( Emes = B�EP ) to deduce from the Ep (photopic illumination) to Emes (mesopic equivalent illumination) is proposed, where B is instant for modified coefficient. The coefficient B can be used easily to calculate the mesopic equivalent illumination by using the measuring results of photopic illumination for different correlated color temperature (CCT) light sources under mesopic light levels. Using the equation, we analyze the variation of coefficient B with background lighting level of the different correlated color temperature lighting sources under mesopic vision levels. By calculating the mesopic equivalent illumination of the different sources, our results showing that the higher correlated color temperature LED sources have better visual effects. Moreover, the results provide a basis for further studies on the illuminometer, which might be suitable for mesopic vision.

A simple novel load sensor has been demonstrated by embedding a uniform fiber Bragg grating (FBG) along the axis of a tapered cylindrical polymer rod. Due to the load-induced nonuniform strain field applied along the length of the FBG, the bandwidth of its reflection spectrum varies linearly with the applied load. By measuring the reflected optical power of the chirped FBG illuminated by a flattened broadband light source, temperature-insensitive measurement of load is realized. It is intensity-modulated so that complex wavelength interrogation system is avoided in the sensor system. In the experiment, the achieved sensitivity is 0.99 nW/N over a range from 0 to 43.12 N. Since the FBG is well protected by embedding in the tapered elastic polymer rod, excellent reliability is expected.

A novel method to measure refractive index by using a phase-shift-adjustable fiber Bragg grating (PSA-FBG) is proposed and demonstrated. The PSA-FBG was obtained by cutting a uniform FBG in the middle and introducing a small air gap between the two FBG halves as phase shift. Tested materials were filled into the small gap so that the quantity of the phase shift is related to refractive index of the tested material. Measurement of refractive index can be carried out by measuring wavelength variation of the phase shift-induced narrow transmission window of the PSA-FBG. Experimental results agree well with numerical analysis, showing a uniform refractive index sensitivity of 0.86 nm/u.r.i with resolution of 0.012.

For breaking through the restrictions of multiple LED products with irregular radiation patterns, free-form microlens optics is designed by the Snell's law and “edge-ray principle” for illumination applications. This non-imaging optics can freely redistribute LED radiations onto target surfaces for prescribed uniform illuminations without considering the specific radiation patterns of LED sources. The surface shape of the single free-form microlens is totally determined by the practical illumination requirements, and calculated by using the three dimensional ray tracing method and B-spline fitting way. Some models of free-from microlens optics were done to achieve prescribed rectangular illuminations. The simulation experiments for these models were done, and the results show that the achieved illuminations have high uniformities, precise illuminating shapes, and insensitivity of the radiation pattern of the sources used, which means that free-form microlens optics is applicable in LED lighting with competitive advantages.

Ba 2 SiO 3 Cl 2 :Eu 2+ , Mn 2+ phosphor was synthesized by high-temperature solid state reaction at 900~1200°C in a slightly reducing atmosphere for 2.0~8.0 hours. The raw materials were the mixture of BaCO 3 , SiO 2 , MnCO 3 , NH 4 Cl, and Eu 2 O 3 in the mol ratio of 3, 2, 0.004, 2 and 0.02. Ba 2 SiO 3 Cl 2 :Eu 2+ , Mn 2+ phosphor's absorption and luminescence spectra were studied. The results indicated that the emission band consists of three peaks located at 425 nm, 492nm and 608nm, respectively. The emission peaks at 425 and 492nm originate from the transition 5d→4f of Eu 2+ ions that occupy the two Ba 2+ sites in the crystal of Ba 2 SiO 3 Cl 2 , while the 608nm emission is attributed to the energy transfer from Eu2+ ions to Mn 2+ ions. The white light can be obtained by mixing the three emission colors of blue (425 nm), green (492 nm) and red-orange (608 nm) in the single host. When the concentrations of the Eu 2+ ions and Mn 2+ ions were 0.02mol and 0.004mol respectively, the sample presented intense white emitting. The excitation spectra of the three emissions extending from 300 nm to 460 nm indicated that Ba 2 SiO 3 Cl 2 :Eu 2+ phosphor can be excitated by InGaN chip UV emission effectively, and it is a single-phase white phosphor with low-cost and high brightness for white LEDs.

The continuing research efforts in white light created by mixing red, green and blue light emitting diodes (RGB LED) will allow their applications in high quality lighting systems in the (near) future. There are still many issues to tackle in this kind of light source, for instance the color uniformity and the change of color-render property owing to the change of LED's temperature. In this paper we simulate the effects on color uniformity of the near-field light distribution due to different LED-chips arrays (at optimum packaging density for uniform irradiance) using High-Power RGB LED-chips. The results showing the color uniformity of near-field which can be achieved with different RGB LED-chips arrays are presented. Several configurations of RGB LED-chips arrays and relevant data for color variation are given respectively. An analysis of luminous efficacy of radiation (LER) and color rendering index (CRI) of this source is performed, which are affected by the peak wavelength, spectral width, and the output peak emission power ratio of LED-chips.

Calibration models of quantitative analysis of peanut oil content in ternary blended edible oil by near infrared spectroscopy were built using partial least square (PLS) regression. A total of 92 samples blended with three kinds of pure oil in different proportion (V/V) were prepared. Near infrared diffuse reflectance spectra of the samples were collected over 4 000 cm -1 -10 000 cm -1 spectral region with a FT-NIR spectrometer. A calibration model of prediction to the peanut oil content was established with PLS using the original spectra and validated with leave-one-out cross validation method. The correlation coefficient and the RMSEC of the model were 0.9926 and 2.91%, respectively. The result showed that near infrared spectroscopy could be an ideal tool for fast determination to the peanut oil content in blended edible oil.

Thermal, optical and electrical parameters are main characterization of light-emitting diodes (LEDs). Consumers are often concerned about the explicit properties such as luminous intensity, luminous flux and color. But Manufacturers may pay more attention to the thermal characteristic. Excess heat at the junction directly affects the LED performance in terms of color shit, light output and life. To measure all these parameters of LED accurately and simultaneously, we designed an integrated system, product number SSP8112, which was based on a new developed thermal, optical and electrical measurement instrument and a specially-made integrating sphere with temperature controller. The thermal measurement segment of the instrument was developed in accordance with JESD51-1 standard; it can automatically record the transient response curve of heat with a 50μs time resolution and a 0.5mV voltage resolution. And the integrating sphere, which has high light reflectivity, good thermal insulation and tolerance to high temperature, was used to achieve the optical response during the experiment. The principle and structure of this system were introduced and discussed, and at the end an application example was presented.

The NIR region is composed of radiation with wavelengths of 700-2500nm. The analytical technology of NIR has many virtues, such as fast (one minute or less per sample), nondestructive, suitable for on-line use. So it can be applied to the textile field. But because of the interference from strongly overlapping constituents' spectra and from light scatter variations, the transformations of the diffuse spectroscopy measurements should ideally pass through two stages, response linearization and optical correction. Before being used in linear calibration model, the spectra data usually is pretreated by the different pretreatment methods. The pretreatment methods contain derivative, smoothing, normalizing, data compression and so on. These pretreatment methods resolve the overlapping peaks, remove the linear baselines and eliminate the spectral noise. Then three methods, Multiple Linear Regression (MLR), Partial Least-Squares (PLS) and Neural networks are adopted to establish a model to with the pretreated spectra data. The first two methods express a linear relationship between the spectral data and the concentration. And the third method is a nonlinear method. The validation sample set is used to validate these three established models. Depending on the comparison of the results, the best linear calibration model to estimate the unknown samples is set up.

The fast qualitative analysis of textile fiber is a crucial step in textile manufacture, export and inspection. This paper presents a near infrared spectroscopy classification method based on SVM for fast qualitative analysis of textile fiber. SVM is a new automatic classification tool and it has successfully been applied to standard classification tasks, such as text classification, pattern identification, bioinformatics and medical diagnosis. In this paper, SVM is extended into near infrared fast qualitative analysis of textile fiber for the first time. In this paper, eight kinds classification algorithms which are composed of two classifiers(C-SVC and ν-SVC) and four kernel functions (linear, polynomial, RBF and sigmoid) are used to do classification experiments and comparison analysis for ten kinds familiar textiles fiber. Experiment results show that it is feasible to apply SVM in fast qualitative analysis of textile fiber, and the optimal classifier algorithm and the corresponding experimental results are reported.

Near Infrared (NIR) spectroscopy in the region from 1300 to 1700nm, coupled with multivariate analytic statistical techniques, have been used to predict the chemical properties of textile fiber. Molecule absorbs electromagnetic wave with especial wavelength, which leads to bring characteristic absorption spectrum. Characteristic wavelength is the most important parameter in NIR detection. How to select characteristic wavelength is the key to NIR measure. Different mathematical methods are used to find relationship between the NIR absorption spectrum and the chemical properties of the textile fiber. We adopt stepwise multiple linear regression (SMLR) to select characteristic wavelength. As objective condition is limited, this article only refers to cotton and terylene. By computing correlation coefficient, we establish calibration equation with the smoothed absorbance data. Finally, the bias was controlled under 6%. Then, we find that NIR can be used to carry on qualitative analysis and quantitative analysis of the textile.

Photosynthesis of plants is to absorb the special wavelength of sunlight by the chlorophylls. According to the absorption spectrum of chlorophylls, we managed to make a LED lamp for the growing of green plants, and the relative energy spectrum distribution of the lamp match with the absorbing spectrum of green plants. Because the absorption wavelength range of chlorophylls are respectively 390~420nm, 430~460nm and 650~680nm, we choose different peak wavelength LEDs which are respectively at 400nm, 450nm, 655nm. By calculation, the general energy ratio of the three types of LEDs is 22:46:33, which corresponds to the absorption spectrum of chlorophylls. The illuminance of lamp for the growing of green plants on plants away 0.5 meter is 80lx by measuring. The LEDs lamp can be used to complement light and increase the efficiency of photosynthesis in cloudy, in door or at night. In another word, the photosynthesis is more powerful, and the more carbohydrates are synthesized, supplying enough material and energy for the growing of green plants.

The Raman spectra intensity can be enhanced in liquid core optical fiber (LCOF) .The total Raman power emitted by the LCOF is a function of the following parameters: LCOF length, LCOF loss coefficients at the laser and Raman wavelengths, the concentration of analyte and input laser power. The attenuation of the light in CS 2 is small in the range from 1400nm to1700nm. We dissolved liquid CCL 4 into CS 2 and got different solutions of different concentrations. When the analyte concentration was changed, the analyte molecules and the numerical aperture of the LCOF were also changed, so there is an optimum concentration at which the maximum Raman spectrum can be obtained. Our experiment result is in good agreement with the calculated results. Backward Raman scattering is superior to forward Raman scattering in our experiment. Raman intensity first increases to a maximum with fiber length, then decrease because the fiber attenuation becomes dominant. Therefore, there exists the optimum fiber length. In our experiment, we find that higher Raman intensity can be obtained when the fiber length is 2m. The Raman intensity becomes powerful when the input pump power becomes larger. Raman linewidth becomes narrow when the concentration decreased. Our experiment also approves it.

With the development of optical fiber communication technology, optical spectrum analyzer (OSA) suitable for field use is urgently required. The laboratory-based OSA can be available only in a laboratory environment and unsuited to field use. By eliminating unwanted functions and fine design, the portable OSA can meet the requirement for field test and provide low cost and high performance. In this paper, a kind of high speed and portable OSA suitable for plastic fiber field test is designed, whose wavelength measurement accuracy is better than 0.1nm and spectrum energy measurement sensitivity is -30dBm.

The main characteristic affecting on fiber transmission are attenuation and dispersion in optical fiber. The equipment of measuring attenuation has been set up in this letter. The attenuation in some organic optical fiber is measured. The lowest losses are 238dB/km at 670nm for PS core, 197 dB/km at 580nm for PMMA core, and 0.2dB/m at 650nm for C 6 H 6 liquid-core optical fiber. Temperature and ultraviolet radiation affecting on loss in fiber are researched.

The operation principle and model of hybrid FRA is discussed. Hybrid FRA consisting of general fiber G652 and DCF includes DCT + G652, G652 + DCF and G652 + DCF + G652. The optimum design of hybrid FRA has been done by using optimum design software of FRA--OptiAmplifier 3.03. The best structure is G652 + DCF. It has many advantages: dispersion compensation of network, wide operation wavelength range (That depend on pump laser wavelength). The configuration has been set up and researched. Using Raman laser (1427nm) as an excited source, Raman gain spectrum of optical fiber and small signal amplification spectrum of is measured by optical spectrum analyzer Q8384. The hybrid FRA has gain bandwidths of 88nm in S and C band. It will increase the transmission channels of fiber communication network.

The backscattering spectrum of optical fiber has been measured by use 1427 nm Raman laser and Q8384 optical spectrum analyzer and Stokes and anti-Stokes ZX band backscattering spectrum has been first observed and discussed, ZX band frequency shift is 1THz, bandwidth 3THz(3dB). Optimum design of S-band negative dispersion DCF discrete fiber Raman amplifier has been researched by OPTIAMP DESIGN 3.3 SOFTWARE (made in Canada Optiwave Corporation) and gain spectrum and gain vs. power of DCF discrete fiber Raman amplifier have been measured, practical including Stokes ZX band backscattering gain effect. Pump on/off small signal gain is 13dB (pump power 700mw; fiber 5.1km) and gain band width is 88nm (1440nm-1528nm). The operation principle, configuration and performance of distributed fiber Raman temperature sensors system has been researched. Amplification of anti-Stokes spontaneity Raman scattering (ARS) effect of fiber and its temperature effect has been first observed and discussed. It has been applied to 30km distributed FRS system.

The operation principle of distributed optical fiber Raman gain amplifier has been discussed. The amplification phenomena have been observed in the 1410-nm wavelength range pumped by the 1320-nm solid laser using 23-km single-mode GI optical fiber. The Raman gain is depending on optical fiber interaction length . The optical fiber effective interaction lengths are 15.5 km and 10.5 km when pump pulse peak power are 50W and 30W. The relation between the gain of Raman amplifier and pump power at different effective interaction length of optical fiber is discussed. The Raman gain of optical fiber is 0.62x10-15 m/W during 50W pump power and the effective interaction area of optical fiber is 30 micrometers 2. The effective interaction area of optical fiber is 41.4 micrometers 2 during the pump power is 30W.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.