This pdf file contains the Front Matter associated with SPIE Proceedings Volume 7853, including the Title page, Copyright information, Table of Contents, and Conference Committee listing.

Gas sensing is evolving into an important application contributing particularly to environmental and safety monitoring. Fibre optic sensing will have an important role to play as the need for gas measurements increase. This paper seeks to overview of the optical techniques which are compatible with fibre optic technology and present a limited snapshot of the applications. Fibre optic techniques offer intrinsic safety, reliability and very long interrogation distances over the fibre link together with prospects for highly multiplexed and distributed systems. There are two basic approaches for fibre sensing targeted at gas measurements. The first involves some intermediate compound in contact with the end of the fibre (or deposited along the fibre) whose optical properties change with the presence of the gas of interest, usually measured spectroscopically. The second involves direct absorption spectroscopy typically in the near infrared. Former techniques are invariably responsive to a number of gas species and are usually difficult to calibrate accurately. The latter techniques are highly gas specific and can be accurately calibrated. However both approaches have their application sectors depending upon particular measurement requirements. The paper presents a brief overview of the principles of both these techniques and analyses some of their applications.

We review recent advances in the plasmonic sensors associated with chemical and biological sensor system and introduce their structural design method for enhancement of sensing performance such as detection limits, sensitivity, and dynamic range, relative to the commercial systems. In addition, the effect of structural parameters of surface plasmon resonance based sensors with transmission or reflection-type configuration is discussed. We also discuss the optimal condition of the sensors with nano-structures as well as flat metallic layer structures for practical sensing and provide the methods for improving sensing capability.

A CCD fiber Bragg grating sensor demodulation system based on FPGA is proposed. The system is divided into three units: spectral imaging unit, signal detection unit and signal acquisition and processing unit. The spectral imaging unit uses reflective imaging system, which has few aberration, small size, simple structure and low cost. In the signal detection unit, information of spectrum are accessed by CCD detector, the measurement of spectral line is converted into the measurement of the pixel position of spot, multi point can be simultaneously measured, so the system's reusability, stability and reliability are improved. In the signal acquisition and processing unit, drive circuit and signal acquisition and processing circuit are designed by programmable logic device FPGA, fully use of programmable and high real-time features, simplified system design, improved the system's real-time monitoring capabilities and demodulation speed.

Optical fiber sensors (OFS) play an important role in modern intellectualized sensing system. A novel optical fiber sensor based on single mode fiber laser is proposed in this paper. The basic elements of the novel fiber laser sensor (FLS) is based in the fact that the output power of fiber laser is influenced by the loss which caused by the absorption loss of analyte in evanescent field of the fiber. The action of the fiber laser sensor is theoretical investigated using two-level system rate equations. The function which contacted the output power of the fiber laser and the absorption loss of analyte is build upon the complex refraction index of the analyte and the loss of the resonant cavity of the fiber laser though evanescent field. The relative sensitivity of the fiber laser sensor is given finally.

A Fiber Bragg gratings (FBG) Interrogation scheme with scan fiber laser was demonstrated. The ring cavity scan fiber laser was investigated and the scan fiber laser module was made and test, the 200Hz scan frequency, ~0.02nm line width, more than 40nm scan range and more than 1 mW output power were obtained. A 12 channels, 20 FBGs per channel FBG interrogator was made with this laser module and the high speed signal process circuit base on FPGA. The centroid finding method which has advantage on interrogation speed and accurate was taken for finding the peak of the return FBG spectrum. The FBG interrogator was test and less than 3pm standard deviation with 200Hz scan frequency were obtained.

Porous silicon has attracted a great deal of attention and research for biochemical sensing applications. In this study, we report a novel porous silicon based resonant grating filters as an optical sensor platform. A narrow bandwidth in the reflectance spectrum is shown of this porous silicon grating filters and this resonance dip shift obviously after little infiltration. This research also played a potential role for the extensive applications in all-silicon biosensor.

The signal-to-noise ratio (SNR) enhancement using polarization scrambler, narrowband-stop grating and cumulative average processing in Brillouin optical time domain reflectometer (BOTDR) is studied experimentally. Compared to the result without these methods, it is confirmed that these techniques can provide the SNR enhancement in our experiment. This makes it possible to perform a better detection threshold and resolution. The experiment result shows that a temperature resolution of 2°C with a spatial resolution of 3 m is achieved on our BOTDR sensor system.

The detection abilities of PGC scheme dealing with the single frequency signal are investigated, based on which, the frequency domain of the signal is analyzed. Based on the Bessel function theoretic, the mathematical model has been established to analyze the performance of interferometric fiber-optic sensor under the PGC demodulation scheme. The spectrums of interferometer output signals are analyzed when the input signal is single frequency signal and multifrequency signal. Simulation results show that the dynamic domain upper limit of fiber-optic sensor when it operates with the multi-frequency signal must be much smaller than that it operates the single frequency signal.

Using the finite element method to simulate THz photonic crystal fiber(PCF)transmission and sensing characteristics. According to solid TPCF guidance, the refractive index, attenuation and relativity sensitivity were analyzed. And we analyzed firstly the transformation of PCF hole-shape to the influence of sensing on THz wave region. Then we simulate and calculate THz high density polyethylene PCF(HDPE-PCF) some parameters, at last the design considerations were given.

We describe in this paper a near infrared (NIR) Stokes polarimeter. This instrument measures the Stokes parameters of a light beam that exits an optical fiber. The key components of this polarimeter include two photoelastic modulators (PEMs) that operate at different resonant frequencies, a calcite analyzer and a Ge-photodiode detector. The two PEMs in the instrument are oriented at 0° and 45°, respectively, and the analyzer is oriented at 22.5°. The electronic signal from the detector is processed using two different demodulation methods. The normalized Stokes parameters are calculated and displayed on the Poincare sphere. We have shown the high accuracy, sensitivity and stability of this instrument in measuring normalized Stokes parameters.

Structural Health Monitoring (SHM) has assumed a significant role in assessing the structures safety and integrity. SHM can be understood as the integration of sensing intelligence and possibly also actuation devices to allow the structure loading and damaging conditions to be recorded, analyzed, localized and predicted in such a way that non-destructive testing becomes an integral part of the structure. SHM sensing requirements are very well suited for fiber optic sensing technology. So in this paper, after a very brief introduction of the basic SHM concepts, the main fiber optic technologies for this application will be reviewed, several examples and the main current technical challenges will be addressed and, finally, the conclusions summarized.

This paper presents a fast estimation method for feedback level factor C of a self-mixing interferometry (SMI) system. The reconstruction of a displacement waveform using a SMI signal needs to know a C value. However, it is difficult to maintain a constant C value during the reconstruction process. We study the features of the reconstructed displacement waveforms incorporating different pre-set C values and classify waveforms into two types. Bisection method is introduced in our method for fast estimating C value. The effectiveness of our proposed method has been verified by both simulation and experimental data.

A novel long-period fiber grating (LPG) refractive index sensor is presented for the measurements of ambient refractive indices which are higher than that of the fiber cladding. As the measurement parameter, the transmission power of the core mode is interrogated at a single wavelength where the core mode and a leaky mode are phase-matched. Firstly, the couplings of the core mode to leaky modes in the novel structure are analyzed by using complex coupled-mode theory, and then classified into three cases analogous to those in the damped oscillations. The power evolutions of the core mode in the couplings are thus intuitively understood. Based on these, for the first time, we demonstrate, with optimized design parameters the transmission power of the core mode is rather sensitive to the change of a higher ambient refractive index at resonant wavelengths. Then we focus on two optimization objectives. One is to enlarge the operational range while keeping given sensitivity, the other is to enhance the sensitivity within a given operational range. Finally, we demonstrate the operational range of the LPG refractive index sensor can be from 1.46 to 1.7 with a sensitivity of ~10^-4, while for a given operational range from 1.455 to 1.465, the sensitivity can be ~10^-6, if assuming the dynamic range of the power is less than 30dB and the measurement resolution is 0.01dB for both cases.

According to the requirement of single-component toxic gases recognition and trace concentration measurement, a novel gas-sensitive sensor array is developed, which chooses metallic porphyrin as sensitive material. Moreover, the multi-spot sensor array detector is designed based on the absorption spectrum measurement and multi-spot measurement. This paper focuses on the structural design of the system and the establishment of the spectral analysis method. The model of after-spectrophotometric structure is adopted by the detector. The entire hardware platform is implemented based on S3C44B0 & μC/OS-II embedded system. In addition, this paper puts forward a recognition model, that combines Principal Component Analysis (PCA) with BP Artificial Neural Networks (BPANN), and an algorithm for trace concentration measurement, based on visible light absorption spectrum analysis. The experimental results show that the correct rate of prediction for 50 unknown samples is 98%, and the maximum relative measuring error is 3%.

A new type of evanescent field sensors based on a doubly cladding single mode fiber is proposed. The theoretical analysis shows that the measurable refractive index (RI) ranges for the sensors are limited in the single mode in the fiber becoming leaky and the range is less than the RI difference between the core and the cladding of the fibers. Two temperature sensors and a humidity sensor were fabricated. One temperature sensor showed a good linear response in a range of 60°C, the modulation depth of 40 dB, and the insertion loss of -1.4 dB. The humidity sensors fabricated by agarose gel had a measurable moisture range of 16 ~ 100% of RH. Its optical power variation with humidity is 8.5 dB and insertion loss is 3.9 dB. We confirmed that the DC single mode fiber sensors became a new type of intensity sensors characterized in good linear response, low insertion loss, high modulation depth, and low cost in fabrication.

A new demodulation technique based on diffraction grating is proposed for high speed application. Compared with tunable filter method, the diffraction grating method has the advantages of potential high interrogation speed, high energy efficiency, no sweeping movements, which makes it a competitive interrogation method in certain field such as dynamic strain monitoring. The optical layout is crucial to guarantee the required performance of the interrogator. A structure which consists of two diffraction gratings, a fiber collimator, a reflection mirror, and a detector is adopted in the consideration of spectrum resolution, optical aberration, and geometrical size. The initial parameters for the structure are figured out by the optical path calculation involving the coefficient of the employed optical elements. The optimized procedure is following sequentially in order to minimize the aberration and obtain the pre-defined specifications theoretically. As the central wavelength for the interrogator is 1550nm, the InGaAs linear array sensor is introduced as the photoelectrical detector. Experiment of demodulation for FBG sensing system is carried out to verify the feasibility of this technique. The wavelength resolution for the interrogator is 1pm, and the demodulation speed is about 2kHz.

The phase/birefringence sensitivities of the fundamental mode of air-silica microstructure optical fibers to strain and pressure are investigated. Theoretical models are built for both hollow-core photonic bandgap fibers and solid-core highly non-linear photonic crystal fibers to study the effects of axial strain, lateral pressure, and acoustic pressure on the fiber length and the effective refractive indexes of the fundamental mode. Numerical simulation shows that the phase/birefringence sensitivity to pressure of a hollow-core photonic bandgap fiber depends strongly on the thickness of the outer solid-silica layer and the air-filling ratio of the microstructure inner-cladding, and the normalized phase sensitivity to acoustic pressure can be 35 dB higher than that of the conventional single mode fiber. Potential applications of the microstructure optical fibers for high sensitivity hydrophones and novel polarization controllers are discussed.

Two kinds of self-loading Farby-Perot (F-P) fiber sensors were prepared by creating micro-grooves on side-face of single mode fiber-28 (SMF-28) and photonic crystal fiber (PCF) with 157 nm excimer laser. Self-loading F-P interference fringe shifts were measured under different temperature, stress and alcohol solution. Temperature sensing experiments show that the sensitivity of PCF and SMF F-P sensors are 0.0580nm/°C and 0.0535nm/°C when the temperature ranges from 30 °C to100 °C. The interference fringe shifts of PCF and SMF F-P sensors are 1.6 nm and 2.2 nm when they were loaded with 80 μm elongation along fiber axis, which correspond to stress sensitivity of 1.41pm/με and 1.50pm/με respectively. The interference fringe shifts of the SMF F-P sensor and the all-solid PCF sensor are 0.4775nm and 0.3490nm when the quality percentage of alcohol changes from 0 to 99.99%.

The amount of light is an important issue in several scenarios ranging from scenic design, light pollution study, illumination engineering, and agriculture. It is typically determined by using a portable digital light or lux meter. By realizing that the proliferation of cell phones is currently tremendous, this paper proposes for the first time a low-cost cell phone based digital light meter. Our innovative idea comes from the fact that the digital camera built into the cell phone is functioned as a two-dimensional light sensitive device and the captured image can be made diffuse. In this way, the diffused image is correlated to the corresponding light level by the built-in microprocessor of the cell phone and our specific algorithm embedded. Our experiment using a typical cell phone embedded with a digital camera and our JAVA program will be discussed.

The purpose of this work is the development of a high sensitivity and biocompatibility Fiber-Optic hydrophone for invivo ultrasound measurements. The selected sensing element- chitosan diaphragm allows matched-load condition due to its relatively permeable property. Chitosan is a natural polysaccharide which considered as biocompatible and biodegradable material that can be safe in performing the in-vivo measurement. The configuration of the sensor is based on the fiber-optic Fabry-Perot interferometry which offers good spatial resolution in the tens of MHz range [1] and robust response. Significant applications of the proposed sensor are in vivo micro-imaging [2], in-vivo lithotripsy measurement [3] or event the laboratory characterization of medical ultrasound sources. In this paper, the performance of the sensor is characterized by comparison with a PVDF needle hydrophone in term of sensitivity, frequency response and directivity.

Specialty optical fibers have been introduced and developed with unusual guiding structures and novel applications. The one of technical challenges to develop the refractive index guided microstructured specialty fibers is how to realize the low loss link between the traditional fiber and specialty optical fiber. In order to insert the microstructured fiber based devices into the standard single mode fiber system, several linkage approaches have been developed and demonstrated. In this paper, we have summarized the recently research progress related with this issue.

Surface plasmon resonance (SPR) sensors with spectral interrogation provide a high refractive index resolution, a large dynamic range and a fixed optical detection module. In this work, we propose a new spectral detection unit that uses only one spectrometer to measure the SPR spectrum from multiple sensing spots rapidly and serially without any mechanical movement. This spectral detection unit is designed based on a spatial light modulator (SLM) configured as a programmable optical aperture for the spectrometer. To demonstrate this concept, a five-channel SPR sensor was built based on the proposed multichannel detection unit and we evaluated the device performance using a refractive index test. The average device refractive index resolution was 1.4 x 10^-6 refractive index units (RIU).

A signal demodulation scheme based on heterodyne technique is demonstrated, which can help fiber-optic hydrophone system meet the demand of large dynamic range and large scale multiplexing. Optical system based on the heterodyne demodulation is given. Reference signal in the demodulation procedure is obtained from the optical heterodyne output, which is quite different from other reported heterodyne techniques. This method not only simplifies RF electronics, but also eliminates the effects of frequency shift vibration generated by the acoustic-optic modulators. Demodulation algorithm is presented and the maximum signal processing capability is analyze. Experiments are carried out and the results show that a signal with a frequency of 1kHz and amplitude of 40rad could be demodulated without distortion when the heterodyne frequency is 64kHz. The same signal is demodulated using PGC scheme with a modulating frequency equal to the heterodyne frequency, and the result shows distortion. Comparing the two demodulation methods verifies that the system we have designed works well and is more suitable for the detection of large signal. Besides, this architecture of system offering advantage of easy to be time-division multiplexed. Together with wavelength-division multiplexing, it demonstrates the potential for the fiber-optic hydrophone to achieve large-scale arrays with high dynamic range.

We report a low-cost interrogator for fiber-optic interferometric and Bragg grating sensors. The interrogator is based on a compact optical path scanner which is made by splicing a hollow fiber to a single mode fiber and by sealing a segment of air and a segment of thermally expanded liquid inside the hollow fiber. The facets between the fiber-air interface and the air-liquid interface reflect the light from the single mode fiber back, and the optical path difference between the two facets can be controlled by changing the temperature of the liquid. When the compact optical path scanner is place inside a white light interferometer together with a sensing fiber-optic Fabry-Perot interferometer, the optical path difference of the sensing interferometer can be decoded as the optical path difference of the scanner when the interference signal gets maximum. The decoding accuracy of such an interferometer interrogation system was measured to be 14 nm over a range of 40 μm. The compact optical path scanner can also be used to form a wavelength meter, which can be applied to decode the Bragg wavelength of a fiber Bragg grating sensor. A decoding accuracy of 3.5 pm was obtained.

The tropospheric SO₂ in Pearl River delta region was firstly measured by airborne Multi Axis Differential Optical Absorption Spectroscopy in China on 10 December, 2008. The SO₂ slant columns were derived with DOAS method in the wavelength from 310~ 325nm and the vertical columns were retrieved by radiative transfer model SCIATRAN. High values were observed near power plant regions with the vertical column density values higher than 8x10¹⁶molec./cm² in the measurement. Combining with the meteorological data from local station the SO₂ flux from the power plant was calculated, the emission flux of SO₂ was about 2.59x10²⁵molec./s. Over the city of Zhuhai, the observed SO₂ vertical column density was 2.46x10¹⁶molec./cm². This is in good agreement with ground-based MAX-DOAS of 2.62x10¹⁶molec./cm² if the same aerosol parameter settings and a well mixed boundary layer of 1000 m is assumed.

A Fabry-Perot interference enhanced surface plasmon resonance (SPR) sensor was designed and analyzed numerically. In this paper, a micro-fluidic channel with two parallel interfaces formed on the metal film of an angularinterrogated SPR sensor was employed. The shift of the narrow reflection dips as a function of the refractive index change of the fluid (angular sensitivity Sθ ) was very high. Meanwhile, the angular dip width δθ_FWHM was very narrow (<0.01°) and can be adjusted by changing the thickness of the resonant cavity. The corresponding intrinsic sensitivity IS = S_θ/δθ_FWHM higher than 10⁵ RIU^-1 around the resonant angle can be achieved.

After several decades, the development and application of absorptive fiber semiconductor temperature sensor have been slowed down for the difficulty to satisfy the critical requirement of the special wavelength and broadband lightsource. On the other hand, temperature-dependent refractive index, i.e., thermal-optic effect of the semiconductor materials has not gained much attention beyond the semiconductor processing industry. With a much larger temperature-dependent refractive index than the common optical materials, such as glass and quartz, many semiconductor are also popular coating materials on fiber. Taking advantage of the interaction of large temperature-dependent refractive index and temperature-dependant absorption coefficient of semiconductor, we manage to build a very small, sensitive, simple and low cost fiber temperature probe operating at communication wavelength. We develop a sensor model for an optical fiber-germanium (Ge) film type temperature sensor based on the modified optical film theory, which involves temperature-dependent absorption below infrared transparent window of Ge as second major cause for reflectivity change beside thermal optical effect. Investigation of the feasibility and sensitivity of the fiber-film probe has been carried out theoretically and experimentally within the temperature regime of -20-120°C, which is the most used temperature range for industry monitoring. A sensitivity of reflectivity change about 0.001/°C has been demonstrated by the experimental results of the novel designed sensor. Further discussion on the potential of sensitivity and further application are presented.

A new-conceptual fiber-optic gyroscope is introduced. The gyroscope employs the two newly-emerged novel technologies: the optical frequency-modulated continuous-wave (FMCW) interference, and the differential fiber-optic gyroscope, and therefore, it can overcome the problems in the traditional fiber-optic gyroscopes, such as temperature drift and poor long-term stability. The FMCW interference, which was originally investigated in radar technology, has been successfully used to construct various fiber-optic interferometers and sensors. The advantages of this technology include accurate calibration of the phase, simple count of fringes, and easy signal processing. The interest in the application of the FMCW technique to rotation sensing has been growing for a long period. The problem in the FMCW fiber-optic gyroscope is that the gyroscope must be an unbalanced, and the initial optical path difference in the gyroscope will cause an unexpected non-reciprocal phase drift if the environmental conditions are unstable. This paper reports a differential FMCW fiber-optic gyroscope. The advantages of this fiber-optic gyroscope include: (1) Due to the nature of the differential interferometer structure, the unexpected non-reciprocal phase drift is automatically removed, and the calibration fact of the gyroscope is automatically doubled. (2) Benefited from the FMCW technology, this gyroscope has no zero-sensitivity point problem, and it has a higher resolution and a larger dynamic range.

Gas analysis based on tunable diode laser absorption spectroscopy (TDLAS) provides features of high sensitivity, fast response and high selectivity. When target gas concentration is below a few parts-per-million spectrometers become more and more sensitive towards noise, interference, drift effects and background changes associated with low level signals. It is purpose of this paper to address some of the problems which are encountered at this low signal levels and to describe a signal processing strategy for gas monitoring with wavelet transform. Different parameters of wavelet by taking gas detection of H₂S as an illustration are studied and an improved wavelet-based signal enhancement process is proposed based on the feature of TDLAS second-harmonic signal. The algorithm uses bior3.9 wavelet basic function and multi-resolution decomposition. The results show a plausible improvement in performance of TDLAS system and enhancement of detection limit from 10ppm to hundreds of ppb level under various noise conditions.

Based on the increased interest for optical fibres development for the use in smart structures and sensors, this study has aimed to investigate the chemical reliability of standard commercial epoxy-acrylate polymer coated fibres subjected to aggressive chemical reagents in gaseous and liquid phase, such as acetylene, ammoniac, dimethyl sulfoxide. Multimode optical fibre was exposed to gaseous reagents for different durations after prior vide exposure. Tensile testing results were treated using Weibull statistics. A comparison of mean failure strength of as-aged fibres to the water influence for similar exposure duration has revealed the highest sensitivity to dimethyl sulfoxide reagent.

Increased demands on air quality have created incentives for new methods to monitor gas pollution. In this paper we will present an online gas analyzer for industrial flue pollution monitoring based on tunable diode laser absorption spectroscopy (TDLAS) technology. Signal measurements with a sensitive device inevitably suffer from the predictable or unpredictable sources such as intensity fluctuations and the laser output wavelength dithers. In order to eliminate or at least reduce the measurement uncertainty and gain high reliability, a close-circle digital-control module with functions of digital signal generator, digital lock-in-amplifier (D-LIA), data acquisition and data processing has been developed to substitute the previous independent signal generator board, analog lock-in-amplifier and data acquisition card in our TDLAS system. With the help of the digital-control module and the advanced digital signal processing techniques the performance of the TDLAS system has demonstrated great improvement in long term field tests.

An image spectrometer of a spatial remote sensing satellite requires shortwave band ranging from 2.1μm to 3μm which is one of the most important bands in remote sensing. We designed an infrared sub-system of the image spectrometer using a homemade 640x1 InGaAs shortwave infrared sensor working on FPA system which requires high uniformity and low level of dark current. The working temperature should be -15±0.2 Degree Celsius. This paper compares three different kinds of methods to control temperature of the sensor. First design uses a temperature control chip Max1978 from Maxim Company. Second design uses ADN8830 from ANALOG Company. Third design is based on FPGA device APA300. Experiment shows that MAX1978 has driving mosfet inside its chip which makes the stability is not appropriate for this homemade shortwave sensor. While the ADN8830 the supply power is limited to 5V, which also limits the driving power of the chip, experiments show that ADN8830 works very well when the voltage is below 5V, but the result is not acceptable when sensor demand more driving current. The FPGA design covers all the disadvantages above, but it introduced a new problem, the electrical circuit takes much more board resources than MAX1978 and ADN8830.

The dispersion properties of LPCF were fully analyzed by using the beam propagation method (BPM). It is shown that the zero dispersion wavelengh (ZDW) of LPCF can be altered to the designed value in a certain range without the modification of the geometric structure. This property is useful for sensing and nonlinear optics applications.

At present, laser optical pumping magnetometer of sensitivity is continuous improved and can measure the range from Earth magnetic field to the bio-magnetic field. In the bio-magnetic field, magnetocardiography (MCG) is paid also more and more attention. In this paper, we will discuss cesium optically pumped magnetometer theoretical analysis, system design, the magnetic field gradient measuring principle. On this basis, we build optically pumped magnetometer in a gradient structure for the cardiac magnetic measurements and filter through the wavelet transform. Based on optical pumping magnetometer measuring MCG will be applied in life science, clinical medicine and other fields.

In this paper, the chromatic confocal technique application in position measurement is studyed theoretically and experimentally. Firstly, a set of refractive lenses are designed and a position measurement device is established for this purpose. Then, calibration of wavelength-depth relationship has been performed. The calibration results accords with the theoretical design results well. Third, influence of the detector pinhole size on axial resolution of the measurement system is analyzed. It is clear from numerical simulation that the full width of half maximum (FWHM) of spectral distribution on the detector will increase with enlargement of pinhole size, which makes axial resolution decrease. The experiment results also disclose identical tendency. It can be concluded that the position measurement system can realize rapid position measurement with higher precision.

In this paper, we report a new facile method for the synthesis of water-soluble PbS quantum dots (QDs), using dihydrolipoic acid (DHLA) as a stabilizer. The prepared QDs were characterized by optical techniques and high-resolution transmission electron microscopy (TEM). Next, these water-soluble luminescent PbS QDs were further used to detect copper (II). The obtained experimental results show that the fluorescence of the PbS QDs could be markedly quenched by Cu(II) whereas approximate concentrations of other physiologically relevant cations, such as Zn(II), Ca(II), Mg(II), Mn(II), Na(I) and K(I) etc., almost did not interfere with the fluorescence quenching progress of copper ions. Based on this, a simple and rapid method for Cu(II) determination was developed. Under optimal conditions, the response was linearly proportional to the copper(II) concentration in the range of 1 to 11.5x10^-8 mol•L^-1, with a correlation coefficient of 0.995. Hence, aqueous DHLA-stabilized PbS QDs may be a promising fluorescent probe in sensing copper(II) selectively.

The enhancement of evanescent waves in multilayer planar waveguides with a uniaxially anisotropic metamaterials layer is investigated. Without loss of generality, we assume that the anisotropic metamaterials have an arbitrary angle between the optical axis and the interface, and then we derive the characteristic equations and the analytical expression of energy flux of this waveguides. It is found that the enhancement factor increases rapidly at first with increasing of the thickness of the metamaterials in the case when the optical axis is parallel to or normal to the interface, namely the angle is equal to 0 or π/2. The enhancement factor eventually reaches its maximum when complete surface polaritons are established at the boundary between the metamaterials and the cladding [D.-K. Qing, G. Chen, Appl. Phy. Lett. 84(5), 669-671 (2004).]. Numerical results confirm our theoretical analysis.

In this paper, a high birefringence loop mirror sensing head was introduced, and its temperature, strain sensing properties with panda-type HBFLM were analyzed and researched in experiment. Experimental results showed that both the temperature and strain sensors have high sensitivity, linearity. Its temperature sensitivity reached 1.41 nm/°C, with the sensitivity linearity was up to 0.99968; Its strain sensitivity was 0.02362 nm /με, when the linearity between strain and wavelength shifts was above 0.99912. This panda HBFLM temperature sensor can be widely used in some industries requiring high sensitivity, miniaturization of structure, and stability, such as high voltage cables, oil temperature measurement, and large monitoring structure fields such as detecting important buildings, bridges, dams.

An image spectrometer of a spatial remote sensing satellite requires shortwave band range from 2.1μm to 3μm which is one of the most important bands in remote sensing. We designed an infrared sub-system of the image spectrometer using a homemade 640x1 InGaAs shortwave infrared sensor working on FPA system which requires high uniformity and low level of dark current. The working temperature should be -15±0.2 Degree Celsius. This paper studies the model of noise for focal plane array (FPA) system, investigated the relationship with temperature and dark current noise, and adopts Incremental PID algorithm to generate PWM wave in order to control the temperature of the sensor. There are four modules compose of the FPGA module design. All of the modules are coded by VHDL and implemented in FPGA device APA300. Experiment shows the intelligent temperature control system succeeds in controlling the temperature of the sensor.

We investigate an ultra-weak feedback effect of DBR fiber lasers based on the steady-state rate equations. The ultra-weak-feedback effects of DBR fiber lasers are introduced by the fiber Rayleigh scattering and the scattering of the fiber splicing point. The output powers of the DBR fiber lasers are modulated when their feedbacks are modulated. A simple vibration sensing scheme based on this effect is proposed and demonstrated. The optimized design of the sensing scheme is discussed at last.

We study a novel multi-parameter sensing device based on writing Bragg grating in the multimode fiber of single-multi-single mode fiber structure. The theoretical analysis of the novel device is given based on a compound coupled mode theory. The simulation results of strain and temperature sensing simultaneous are demonstrated, and the elementary results of the refractive index sensing with temperature-compensation are also given.

We have studied the properties of defect modes in one-dimensional ternary photonic crystal with one defect layer using transfer matrix method(TMM). we first compared the transmission spectra of one dimensional ternary photonic crystal with that of one dimensional binary photonic crystal, and found more bandgaps in the ternary structures. Then we are interested in the defect mode properties of the ternary structures, especially the optical sensing abilities. In the special bandgap owned only by the ternary photonic crystals, the defect modes are found to be very sensitive for sensing very small refractive index changes or very small thickness modulations of the defect layer medium. The defect mode wavelength could shift by 3nm for each refractive index change of 0.006, and the defect mode wavelength could shift by 13nm for each thickness change of 10nm. Finally we introduced a negative-refractive-index defect layer into the ternary structure and found that the defect mode wavelength could shift even by 27nm (two times of 13nm) for each thickness change of 10nm.

This paper presents comprehensive research on fused-tapered Bragg reflection integrative FGC where high-quality and easy-fabricating are two main considerations. The technical procedure of FGC fabrication is fixed after a series of experiments. The possible factors that may determine the device performance were carefully analyzed. The fused-tapered FGC was successfully fabricated and a novel testing system was established. The adding and dropping functions of FGC were investigated experimentally.

A C₂H₅OH gas sensor based on a LPFG coated with the T_iO₂ nano-film is presented.Based on LPmodes,the four-layer model is studied the change of the effective refractive indics and the resonance wavelength of cladding modes as the thickness of overlay increased.The elementary experimental results show that the wavelength of the LPFG loss peak is shifted by ~1.7nm for the case of the T_iO₂ nano-film of ~80nm in thickness when the concentration of surrounding C₂H₅OH gas is 1000ppm. And the sensitivity is 1.7 10^-3 nm/ppm. The results indicate that the LPFG sensor is highly sensitive to C₂H₅OH gas and the sensing scheme is feasible.

With the development of the society and economy and the improvement of living standards, people need more and more pressing security. Perimeter security alarm system is widely regarded as the first line of defense. A highly sensitive Fiber Bragg grating (FBG) vibration sensor based on the theory of the string vibration, combined with neural network adaptive dynamic programming algorithm for the perimeter security alarm system make the detection intelligently. Intelligent information processing unit identify the true cause of the vibration of the invasion or the natural environment by analyzing the frequency of vibration signals, energy, amplitude and duration. Compared with traditional perimeter security alarm systems, such as infrared perimeter security system and electric fence system, FBG perimeter security alarm system takes outdoor passive structures, free of electromagnetic interference, transmission distance through optical fiber can be as long as 20 km It is able to detect the location of event within short period of time (high-speed response, less than 3 second).This system can locate the fiber cable's breaking sites and alarm automatically if the cable were be cut. And the system can prevent effectively the false alarm from small animals, birds, strong wind, scattering things, snowfalls and vibration of sensor line itself. It can also be integrated into other security systems. This system can be widely used in variety fields such as military bases, nuclear sites, airports, warehouses, prisons, residence community etc. It will be a new force of perimeter security technology.

VNIR multi-spectral image sensor has wide applications in remote sensing and imaging spectroscopy. An image spectrometer of a spatial remote programmable push-broom sensing satellite requires visible near infrared band ranges from 0.4μm to 1.04μm which is one of the most important bands in remote sensing. This paper introduces a method of design the driving system for 1024x1024 VNIR CCD sensor for programmable push-broom remote sensing. The digital driving signal is generated by the FPGA device. There are seven modules in the FPGA program and all the modules are coded by VHDL. The driving system have five mainly functions: drive the sensor as the demand of timing schedule, control the AD convert device to work, get the parameter via RS232 from control platform, process the data input from the AD device, output the processed data to PCI sample card to display in computer end. All the modules above succeed working on FPGA device APA600. This paper also introduced several important keys when designing the driving system including module synchronization, critical path optimization.

Thermal properties and spectroscopic properties of the glass micro-sphere were presented in this paper. The Er³⁺ emission spectra of a kind of Erbium-doped glass microsphere were measured and discussed under 532nm excitation in a series of temperatures. The change in the temperature of the microsphere leads to a change in both the size and the index of refraction of the sphere, which results in the resonance shift of the peaks of whispering gallery modes in emission spectra. The temperature of the environment surrounding the sphere can be determined by monitoring the shift, which allows us to calibrate the sensing function of the shift proportional to temperature. Based on the thermal effects, we propose a novel optical temperature sensor using micrometer-sized sphere.

Heart sound includes a lot of physiological and pathological information of heart and blood vessel. Heart sound detecting is an important method to gain the heart status, and has important significance to early diagnoses of cardiopathy. In order to improve sensitivity and reduce noise, a heart sound measurement method based on fiber Bragg grating was researched. By the vibration principle of plane round diaphragm, a heart sound sensor structure of fiber Bragg grating was designed and a heart sound sensing mathematical model was established. A formula of heart sound sensitivity was deduced and the theoretical sensitivity of the designed sensor is 957.11pm/KPa. Based on matched grating method, the experiment system was built, by which the excursion of reflected wavelength of the sensing grating was detected and the information of heart sound was obtained. Experiments show that the designed sensor can detect the heart sound and the reflected wavelength variety range is about 70pm. When the sampling frequency is 1 KHz, the extracted heart sound waveform by using the db4 wavelet has the same characteristics with a standard heart sound sensor.

The demodulations of the Bragg wavelength shifts are significant and gaining more and more interesting. Detecting the wavelength shifts based on the interferometry has a very high sensitivity. The unbalanced Mach-Zehnder interferometer system can translate the Bragg wavelength of FBGs caused by the strain into the phase information. The tested strain can be obtained through the phase variation by the three-step phase-shifting method. A finite element model is built up and theoretical analysis has been done. Series experiments measuring the strain properties of the cantilever are carried on. The results show that the tested strain and the changed phase have a linear relationship. The unbalanced Mach-Zehnder interferometer system owns a high-sensitivity and accuracy.

In the field of micro laser welding, besides the special requirement in the parameter of lasers, the locating in welding points accurately is very important. The article adopt position sensitive detector (PSD) as hard core, combine optic system, electric circuits and PC and software processing, confirm the location of welding points. The signal detection circuits adopt the special integrate circuit H-2476 to process weak signal. It is an integrated circuit for high-speed, high-sensitivity optical range finding, which has stronger noiseproof feature, combine digital filter arithmetic, carry out repair the any non-ideal factors, increasing the measure precision. The amplifier adopt programmable amplifier LTC6915. The system adapt two dimension stepping motor drive the workbench, computer and corresponding software processing, make sure the location of spot weld. According to different workpieces to design the clamps. The system on-line detect PSD 's output signal in the moving processing. At the workbench moves in the X direction, the filaments offset is detected dynamic. Analyze the X axes moving sampling signal direction could be estimate the Y axes moving direction, and regulate the Y axes moving values. The workbench driver adopt A3979, it is a stepping motor driver with insert transducer and operate easily. It adapts the requirement of location in micro laser welding fields, real-time control to adjust by computer. It can be content up 20 μm's laser micro welding requirement on the whole. Using laser powder cladding technology achieve inter-penetration welding of high quality and reliability.

The simulation based on the finite-element (FE) method plays an important role in the investigation of the intra-body communication (IBC). In this paper, the method for modeling the whole human body based on the finite-element method is proposed, while a finite-element model of the whole human body used for the simulations of the waveguide intra-body communication has been developed. Finally, the simulations of the waveguide IBC with different signal transmission paths have been achieved by using the developed finite-element model. Moreover, both the potential distributions and the signal attenuations of the simulation results are discussed in detail, which indicate that the proposed method and model offer the significant advantages in the theoretical analysis and the system design of the waveguide intra-body communication.