自光感型支化酰亚胺制备及其性能研究

采用星型氨基单体和各种芳香二酐单体并与邻位烷基苯胺封端合成一系列自光感型支化酰亚胺(HPI),并进行了表征。紫外光谱表明HPI薄膜具有较高的透光性,同时HPI-1薄膜具有较低介电性能。HPI薄膜也表现出较高的玻璃化转变温度(Tg>190℃)和良好的热稳定性能(T5%>506℃)。紫外光刻蚀后的薄膜经过SEM分析,表明具有较细的条带(4μm)。

Photoelectric Inspecting of Artillery Bore

A photoelectric equipment for inspecting artillery bore is composed of digital display grating sensor and data processing with computer.It can replace the traditional mechanical measurer and realize the automatic inspection of artillery bore.Introduced are briefly the working principles and analysis of this device.

Automatic separation system for marine meiobenthos based on laser-induced fluorescence technology

An automatic system for marine meiobenthos separation was developed by using laser-induced fluorescence tech- nology. Rose Bengal was used as organism dye and the spectrums of Rose Bengal were measured. Laser-induced fluorescence system was established to detect marine meiobenthos in sediments. Data obtained from experiments were analyzed by using a mathematical model. The results showed that laser-induced fluorescence technology worked well in the system. The system could select the meiobenthos efficiently and precisely.

Optimised Pattern Recognition for Robotic Weldment Geometry Measuring

Today, automated robot welding of components with low tolerances in series production is state-of-the-art. But turning to small batch production particularly of parts with high tolerances, engineering and construction of automated solutions is just at the beginning of providing economic efficiency. While weld seam tracking is well established for the described problem, geometric recognition of weldments is not yet solved satisfactorily. This paper will present an optimisation approach of a laser sensor guided and programmed robot welding system which was developed within the project ROPROF at the TU Dortmund. With this development, a working prototype of a robot weld system was built by a steel construction company as well as additional demonstration software showing the potential and transferability of adjusted geometric location of weldments for industrial applications.

Recent Progress in Optical Fiber Sensors Based on Brillouin Scattering at University of Ottawa

The distributed sensor is proven to be a powerful tool for civil structural and material process monitoring. Brillouin scattering in fiber can be used as point sensors or distributed sensors for measurement of temperature, strain, birefringence and vibration over centimeters （Brillouin grating length） for point sensor or the pulse length for the distributed sensor. Simultaneous strain and temperature measurement with a spatial resolution of 20 cm is demonstrated in a Panda fiber using Brillouin grating technique with the temperature accuracy and strain accuracy of 0.4 ℃ and 9 με. This technique can also be used for distributed birefringence measurement. For Brillouin optical time domain analysis （BOTDA）, we have developed a new technique to measure differential Brillouin gain instead of Brillouin gain itself. This technique allows high precision temperature and strain measurement over long sensing length with sub-meter spatial resolution： 50-cm spatial resolution for 50-km length, using return-to-zero coded optical pulses of BOTDA with the temperature resolution of 0.7 ℃, which is equivalent to strain accuracy of 12 με. For over 50-km sensing length, we proposed and demonstrated frequency-division-multiplexing （FDM） and time-division-multiplexing （TDM） based BOTDA technique for 75-km and 100-km sensing length without inline amplification within the sensing length. The spatial resolution of 2m （100km） and Brillouin frequency shift accuracy of 1.5 MHz have been obtained for TDM based BOTDA and 1-m resolution （75 km） with Brillouin frequency shift accuracy of 1 MHz using FDM based BOTDA. The civil structural health monitoring with BOTDA technique has been demonstrated.

Laser Beam Shaping and Mode Conversion in Optical Fibers

A new class of all-fiber beam shaping devices has been realized by inverse etching the end face of single mode and multimode fibers to form a concave cone tip. Concave tip fiber can convert a Gaussian beam profile to a flat top beam profile with a uniform intensity distribution. A flat top beam with intensity variation of approx. 5% and flat top diameter to spot diameter ratio of 67% has been achieved. This device can also change the beam shape from a Gaussian to a donut by moving the observation plane. A flat top multimode fiber beam delivery is attractive for applications which require high power and uniform intensity distribution. In single mode fiber, concave tips could be used to reduce the beam spot size diameter, enabling efficient light coupling from a single mode fiber to an integrated optical waveguide.

Optical Fiber Sensors： a Route From University of Kent to Portugal

In this work the authors first summarily describe the main topics that were the subject of their post-graduate activity in fiber sensing at the Applied Optics Group of University of Kent in the late 1980s and early 1990s. After their return to Porto, Portugal, the know-how acquired during their stay at Kent and the collaboration paths that followed between the University of Porto and University of Kent were instrumental in the start-up and progress of optical fiber sensing activity in Portugal. The main topics addressed in this field, the description of some of the relevant developments achieved in recent years, the present situation and the guidelines for the future research and development activity in Portugal in fiber sensing will be the core of this work.

Fiber-Optic Sensor Applications in Civil and Geotechnical Engineering

Different types of fiber-optic sensors based on glass or polymeric fibers are used to evaluate material behavior or to monitor the integrity and long-term stability of load-bearing structure components. Fiber-optic sensors have been established as a new and innovative measurement technology in very different fields, such as material science, civil engineering, light-weight structures, geotechnical areas as well as chemical and high-voltage substations. Very often, mechanical quantities such as deformation, strain or vibration are requested. However, measurement of chemical quantities in materials and structure components, such as pH value in steel reinforced concrete members also provides information about the integrity of concrete structures. A special fiber-optic chemical sensor for monitoring the alkaline state （pH value） of the cementitious matrix in steel-reinforced concrete structures with the purpose of early detection of corrosion-initiating factors is described. The paper presents the use of several fiber-optic sensor technologies in engineering. One example concerns the use of highly resolving concrete-embeddable fiber Fabry-Perot acoustic emission （AE） sensors for the assessment of the bearing behaviour of large concrete piles in existing foundations or during and after its installation. Another example concerns fiber Bragg grating （FBG） sensors attached to anchor steels （micro piles） to measure the strain distribution in loaded soil anchors. Polymer optical fibers （POF） can be -- because of their high elasticity and high ultimate strain - well integrated into textiles to monitor their deformation behaviour. Such ＂intelligent＂ textiles are capable of monitoring displacement of soil or slopes, critical mechanical deformation in geotechnical structures （dikes, dams, and embankments） as well as in masonry structures during and after earthquakes.

Review on Recent Developments of Fluorescent Oxygen and Carbon Dioxide Optical Fiber Sensors

Oxygen and carbon dioxide sensors are involved in many chemical and biochemical reactions. Consequently, considerable efforts over years have been devoted to discover and improve suitable techniques for measuring gas concentrations by optical fiber sensors. Optical gas sensors consist of a gas-sensitive dye entrapped in a matrix with a high permeability to gas. With such sensors, gas concentration is evaluated based upon the reduction in luminescence intensity caused by gas quenching of the emitting state. However, the luminescence quenching effect of oxygen is highly sensitive to temperature. Thus, a simple, low-cost plastic optical fiber sensor for dual sensing of temperature and oxygen is presented. Also, a modified Stern-Volmer model is introduced to compensate for the temperature drift while the temperature is obtained by above dual sensor. Recently, we presented highly-sensitive oxygen and dissolved oxygen sensors comprising an optical fiber coated at one end with platinum （II） meso-tetrakis（pentafluorophenyl）porphyrin （PtTFPP） and PtTFPP entrapped core-shell silica nanoparticles embedded in an n-octyltriethoxysilane（Octyl-triEOS）/tetraethylorthosilane （TEOS） composite xerogel. Also, two-dimensional gas measurement for the distribution of chemical parameters in non-homogeneous samples is developed and is of interest in medical and biological researches.

Loop Topology Based White Light Interferometric Fiber Optic Sensor Network for Application of Perimeter Security

A loop topology based white light interferometric sensor network for perimeter security has been designed and demonstrated. In the perimeter security sensing system, where fiber sensors are packaged in the suspended cable or buried cable, a bi-directional optical path interrogator is built by using Michelson or Mach-Zehnder interferometer. A practical implementation of this technique is presented by using an amplified spontaneous emission （ASE） light source and standard single mode fiber, which are common in communication industry. The sensor loop topology is completely passive and absolute length measurements can be obtained for each sensing fiber segment so that it can be used to measure quasi-distribution strain perturbation. For the long distance perimeter monitoring, this technique not only extends the multiplexing potential, but also provides a redundancy for the sensing system. One breakdown point is allowed in the sensor loop because the sensing system will still work even if the embedded sensor loop breaks somewhere.

An Optical Fiber Hydrophone Using Equivalent Phase Shift Fiber Bragg Grating for Underwater Acoustic Measurement

An optical fiber hydrophone based on equivalent phase shift fiber Bragg grating （EPS-FBG） with temperature compensation package provides an improvement of sensitivity in underwater acoustic measurement at wide frequency range, from 2.SkHz to 12kHz. The acoustic pressure is transduced into elastic vibration of a circle metal disk, resulting in an intensity modulation of the reflected light wave back from fiber Bragg grating （FBG）. Experiment shows that the 500 EPS-FBG hydrophone has a minimum detectable acoustic pressure of about at 5 kHz and achieves about 18-dB improvement of acoustic pressure sensitivity compared with a regular apodized FBG hydrophone.

Fiber Laser Based Hydrophone Systems

We report our recent work on distributed feedback fiber laser based hydrophones. Some issues related to sensitivity, such as fiber laser phase condition, demodulation, and packaging, are also discussed. With the development of appropriate digital signal processing （DSP） techniques and packaging designs, an interferometric-type distributed feedback （DFB） fiber laser hydrophone system with acoustic sensitivity of 58.0 dB·re·uPa-Hz-0.5 at 1 kHz or a minimum detectable acoustic pressure below 800 uPa during field test is attained. We have also investigated an intensity-type DFB fiber laser hydrophone system and its performance.

Multi-Channel Monolithic Integrated Optic Fiber Bragg Grating Sensor Interrogator

Fiber Bragg grating （FBG） is a mature sensing technology for the measurement of strain, vibration, acoustics, acceleration, pressure, temperature, moisture, and corrosion. It has gained rapid acceptance in civil, aerospace, chemical and petrochemical, medicine, aviation and automotive industries. The most prominent advantages of FBG are： small size and light weight, distributed array of FBG transducers on a single fiber, and immunity to radio frequency interference. However, a major disadvantage of FBG technology is that conventional state-of-the-art FBG interrogation system is typically bulky, heavy, and costly bench top instruments that are typically assembled from off-the-shelf fiber optic and optical components integrated with a signal electronics board into an instrument console. Based on the industrial need for a compact FBG interrogation system, this paper describes recent progress towards the development of miniature fiber Bragg grating sensor interrogator （FBG-TransceiverTM） system based on multi-channel monolithic integrated optic sensor microchip technology. The integrated optic microchip technology enables monolithic integration of all functionalities, both passive and active, of conventional bench top FBG sensor interrogator system, packaged in a miniaturized, low power operation, 2 cmx5 cm small form factor （SFF） package suitable for long-term structural health monitoring in applications where size, weight, and power are critical for operation.

Staying Coherent After Kent： From Optical Communications to Biomedical Optics

In this paper, an overview of author＇s research is presented, commencing at the University of Kent under Prof. David A. Jackson. Early research in short optical pulses and fiber-optic delay-line digital correlators led to optical communications research in code-division multiple access networking. This research was based on broadband incoherent light, and this theme continued with research into spectrum-sliced wavelength-division multiplexing. In shifting from photonics research to biomedical optics and biophotonics in the late 1990s, the emphasis on exploiting broadband light continued with research in optical coherence tomography, amongst other topics. In addition to the research outcomes, how these outcomes were attained is described, including mention of the exceptional contributions of many of my colleagues.

Study on Fiber-Optic Low-Coherence Interferometric and Fiber Bragg Grating Sensors

This article reviews author＇s research work on fiber-optic sensors over the last twenty years. It includes two aspects： low-coherence interferometric sensors （LCI） and fiber Bragg grating （FBG） sensors. For LCI sensors, author＇s work mainly focuses on the interrogation and multiplexing methods for Fizeau and Fabry-Perot interferometric sensors at the University of Kent at Canterbury （UKC）, UK, and study on novel Fabry-Perot interferometric sensors and their multiplexing methods at Chongqing University （CQU） and University of Electronic Science ＆ Technology of China （UESTC）, China, respectively. For FBG sensors, a number of multiplexing schemes are proposed and demonstrated at UKC, and then novel methods for realization of multi-parameter measurement and long-distance measurement based on the FBG sensor and its combination with other optical fiber sensors are also reported at CQU ＆ UESTC. Thus, author＇s study on these two topics can be diviaed into two periods, at UKC and at CQU ＆ UESTC, China. This review is presented in such a time sequence.

Optical Sensing Based on Light Coupling Between Two Parallel Long-Period Fiber Gratings

A new optical intensity-based sensing mechanism for the measurement of refractive index and minute displacement is proposed in this paper, which is based on modifying the amount of light coupled between two parallel long-period fiber gratings. The characteristics of this sensing mechanism with experiments and simulation results are demonstrated.

Research Activities Arising From the University of Kent

In this paper I describe research activities in the field of optical fiber sensing undertaken by me after leaving the Applied Optics Group at the University of Kent. The main topics covered are long period gratings, neural network based signal processing, plasmonic sensors, and polymer fiber gratings. Ⅰ also give a summary of my two periods of research at the University of Kent, covering 1985-1988 and 1991-2001.

Broadband Fourier-Domain Mode-Locked Lasers

Broadband, high-speed wavelength-swept lasers can substantially enhance applications in optical coherence tomography, chemical spectroscopy, and fiber-optic sensing. We report the demonstration of Fourier-domain mode-lock lasers operating at about 90kHz effective sweep rate over a 158nm sweep range using a single-band design and over a 284nm sweep range across the 1.3 μm to 1.5μm wavelength spectrum using a unique broadband design. A novel dual-detection full-range Fourier-domain optical coherence tomography system is developed which provides 7 I-tm axial resolution （in air）at about 90 kHz axial scan rate for mirror-image resolved Doppler imaging in a human finger and an African frog tadpole.

Research Following a Foundation in the Applied Optics Group at University of Kent

This paper summarizes research activities at University of Kent over the period from September 1981 through November 1984. Subsequent researches undertaken in the US Naval Research Laboratory and two start-up companies are also described.

Route to OCT From OFS at University of Kent

A review is presented of several technical solutions developed by the Applied Optics Group （AOG） in the field of low coherence interferometry applied to optical fiber sensors （OFS） that subsequently allowed AOG to quickly progress in the field of optical coherence tomography （OCT）.