This PDF file contains the front matter associated with SPIE Proceedings Volume 6757, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

Intensity-modulated fiber-optic sensors have many advantages including simplicity and potential low cost. The developments of several intensity-modulated fiber Bragg grating (FBG) sensor systems are introduced in this paper. These include a displacement sensor, a tilt sensor (both based on chirped FBGs), and a dual-FBG based sensor which can measure lots of parameters such as strain. For the chirped FBG based sensors, the measurands are related to reflection optical powers of the sensing FBGs by changing their chirp rates (or reflection bandwidths) which are insensitive to temperature. While the dual-FBG based sensor is based on electrical beating of modulated radio-frequency (RF) signals reflected from the two FBGs, which act as the sensing element and reference respectively. The power of the RF beating signal depends on the wavelength separation of the two FBGs. By monitoring the RF signal power, intensity-modulated FBG sensing with the sensitivity depending on the modulation frequency of the light source is realized while the temperature effect is compensated by the reference FBG. Experimental measurement of strain, displacement and tilt angle are implemented and good results are achieved.

This paper presents the development of a sapphire-based fiber-optic sensing system for temperature monitoring in harsh environment, including sensor and system design, implementation, laboratory tests and field demonstration. The sensor is built with single-crystal sapphire fiber and sapphire wafer. As the sensing element, the wafer constitutes an extrinsic Fabry-Perot interferometer (EFPI) by its two surfaces. Its optical thickness has significant thermal dependence and provides temperature information through white light interferometry. The sensors were tested to 1600°C with 0.2% full scale accuracy and 0.5°C resolution. They were further demonstrated in industrial environment. A complete sensing system was developed around the sensor for temperature monitoring in a coal gasifier at the Tampa Electric Company's Polk Power Station. It consists of three major components: 1) Sensors and their packaging which were installed in the coal gasifier, 2) Optical interrogation unit for detection and transmission of sensor signal, and 3) Processing and control unit for signal demodulation. The system continuously operated and delivered temperature readings for seven months.

Modern oil production in the oilfield management needs a sensor which enable fast, reliable and cost-effective through highly integrated optical measurement systems. A sensor for accurate and long-term fluid high pressure and temperature monitoring in oil down-hole based on optical fiber Bragg grating is presented. This sensor, using fiber Bragg grating written in side-hole single mode fiber, has small size and simple construct. At different temperature, the pressure measurements from atmospheric pressure to 40 Mpa has been made. It has very linear relationship between peak separation and pressure.

The liquid core optical ring resonator (LCORR) integrates an array of optical ring resonators into a microfluidics channel. The LCORR is made of a micro-sized glass capillary; the circular cross-section of the capillary acts as an optical ring resonator while the resonating light interacts with the fluid sample passing through the core. Q-factors larger than 10⁷ have been achieved in LCORRs on the order of 100 micrometers in diameter. This implies an effective interaction length between the evanescent field of the resonator and the fluidic core of over 10 cm. The novel integrated architecture and excellent photonic performance lead to a number of applications in sensing, analytical chemistry, and photonics. For the last decade, optical ring resonators have been explored for label-free bio/chemical detection. The LCORR architecture possesses the same capabilities as other optical ring resonator bio/chemical sensors while also integrating micro-capillary-based fluidics with the sensor head. The integrated fluidics design in combination with the micro-sized sensor head and pico-liter sample volume lead to a lab-on-a-chip sensor for biomolecules, such as biomarkers and specific DNA sequences. Also, because the ring resonator creates a high-intensity field inside the microfluidic channel, the LCORR is an excellent microfluidic platform for surface-enhanced Raman scattering (SERS) detection in silver colloids. Finally, the high quality factor of the capillary-based resonator enables novel opto-fluidic devices, such as dye lasers. We will discuss the details of these concepts and present our research results in each of these applications.

We report in this paper the fabrication of high performance thermal LPFGs by point-by-point CO₂ laser irradiations. These thermal LPFGs have shown much better temperature tolerance and promised applications in high temperature harsh environments. The computer-controlled fabrication system with in situ signal monitoring capability is described. The fabricated LPFGs survived high temperatures up to 800°C. Long term stability test at 550°C for 200 hours indicated that thermal shock at a higher temperature could significantly reduce the drift.

Thermoreversible compounds have been investigated for applications as a transducer in a fiber-optic temperature sensor utilizing a 2×2 fiber optic coupler. The dependence of the reflected optical power on the temperature has been studied. The reflected optical power at 632.8 nm indicated a monotonous change in the temperature range of observation, corresponding to 2.05dB increase in the optical power when the temperature increased from 20°C to 134°C. The temperature dependence of the optical properties was found to be reversible, which indicates that the temperature transducer is reversible as well.

Typical control systems that are found in modern power plants must control the many physical aspects of the complex processes that occur inside the various components of the power plant. As detection and monitoring of pollutants becomes increasingly important to plant operation, these control systems will become increasingly complex, and will depend upon accurate monitoring of the concentration levels of the various chemical species that are found in the gas streams. In many cases this monitoring can be done optically. Optical access can also be used to measure thermal emissions and the particulate loading levels in the fluid streams. Some typical environments were optical access is needed are combustion chambers, reactor vessels, the gas and solid flows in fluidized beds, hot gas filters and heat exchangers. These applications all have harsh environments that are at high temperatures and pressures. They are often laden with products of combustion and other fine particulate matter which is destructive to any optical window that could be used to monitor the processes in these environments in order to apply some control scheme over the process. The dust and char that normally collects on the optical surfaces reduces the optical quality and thus impairs the ability of the optical surface to transmit data. Once this has occurred, there is generally no way to clean the optical surface during operation. The probe must be dismounted from the vessel, disassembled and cleaned or replaced, then remounted. This would require the shutdown of the particular component of the plant where optical monitoring is required. This renders the probe ineffective to be used as the monitoring part of any control system application. The components of optical monitoring equipment are usually built in supporting structures that require precise alignment. This is almost always accomplished using fine scale adjustments to specialized mounting hardware that is attached to the reactor vessel. When the temperature of these supporting structures increases due to the high temperature process that is occurring inside the vessel, the optical alignment can often suffer due to the thermal expansion of the mounting structure. This can render them useless especially for gas velocity measurements or other situations where precise optical alignment is required. What is needed is an optical probe that can be inserted into any hazardous environment that will not suffer alignment problems or other failure modes that are related to high temperature dirty environments, and at the same time maintain a clean optical surface through the lifetime of the devise so that it may be continually used for optical inspection or for control system applications. This paper describes details of the construction and the use of a transpiration purged optical probe which mitigates the problems that are outlined above. The transpiration probe may be used as either an emitter or a detector. The probe is implemented in the harsh high temperature environment of the NETL pulsed combustion system where products of combustion and particulate matter have been shown to degrade the performance of a normal optical window. Assessments of combustion heat release are made by monitoring the ultraviolet signatures that are produced by the concentration of OH during a pulsed combustion process. It is shown that these measurements are directly correlated with the pressure within the pulsed combustor. Probe temperature measurements are also presented to show how the probe and its mounting hardware remain at constant temperatures well below the high temperature environment which they monitor.

Monitoring of gaseous species is important in a variety of applications including industrial process gas monitoring, mine safety, and homeland security. Fiber optic sensors have been used in a variety of forms to monitor various types of gaseous species. Optical fiber sensors utilizing both random hole and photonic crystal fibers have been investigated. One limitation to these types of fiber sensors is the fact that the holes run parallel to the optic axis of the fiber, requiring gases to diffuse over long distances. Diffusion of gases over long distances through tube sizes which are on the order of microns is a relatively slow process. This can significantly impact the response time of the sensors which are made from these types of fibers. This paper presents results on the development of optical fibers for gas sensing applications which have holes extending in the radial direction as opposed to the longitudinal direction (as in the case of photonic crystal fibers). The holes are made by a process which utilizes phase separation of the glass matrix at relatively low temperatures. The secondary phase is removed by subsequent leaching processes, leaving a three dimensionally porous structure. The porosity is arranged in a stochastic fashion within the fiber. Results of the fiber sensor development and testing will be presented. The microstructural analysis of the fibers by scanning electron microscopy as well as the optical characterization of the fibers will be presented. Fabrication procedures for the optical fibers and the optical fiber sensors will also be described.

In this study, a new zeolite thin film-coated long-period fiber grating (LPFG) sensor was developed and evaluated for chemical vapor detection. The sensor was fabricated by growing nanoporous MFI-type zeolite (pore size ~0.55nm) thin film on fiber grating using in situ hydrothermal crystallization method. The hydrothermal synthesis process was controlled by continuously monitoring the LPFG transmission spectrum evolution, which indicated the zeolite film formation and growth process. The zeolite-LPFG sensor was activated by calcination in air to remove the structural directing agent from the zeolite pores and then demonstrated for sensitive detection of chemical vapor in gas phases.

We present a novel label-free method of quantifying single stranded DNA concentrations in solution using the Liquid Core Optical Ring Resonator (LCORR). The LCORR is a glass capillary that is capable of evanescent sensing of analytes while providing fluidic delivery through its hollow core. An evanescent field is excited in the ring-shaped circumference of the LCORR by externally coupled photons, which circulate via total internal reflection in the form of Whispering Gallery Modes (WGM's). When the wall of the capillary is etched to under 5 μm, the evanescent field from the WGM's is exposed in both the internal and external media. Chemical modification of the interior of the LCORR enables specific capture of target oligonucleotides by hybridization with a covalently bound probe. Refractive index changes at this interface are shown to produce a measurable change in the optical signal by shifting the resonance condition of the cavity. Real time kinetic analysis of the hybridization between the two complimentary strands is demonstrated as well as a thorough calibration of the sensor response to strand lengths between 25 and 100 bases and bulk concentration from 0.5 nM to 10 μM. Non-specific binding of completely mismatched oligonucleotides is shown to be minimal and single base mismatch detection is also demonstrated definitively.

The SSULI (Special Sensor Ultraviolet Limb Imager) is a low-resolution hyperspectral far and extreme ultraviolet limb-scanning imager designed to monitor ionospheric and thermospheric airglow. SSULI has a spectral range from 80 to 170 nm, and a nominal resolution of 2.1 nm (at 147 nm). The instrument is scheduled to fly aboard all Defense Meteorological Satellite Program (DMSP) Block 5D3 weather satellites. The first SSULI instrument was launched in fall 2003, aboard the DMSP F16 flight, and has been collecting data since December 2003. The second SSULI flight aboard DMSP F17 began in fall 2006. Early in the missions, both instruments began to observe intermittent but significant periods of noise across the entire instrument passband, beyond the expected ion noise associated with sub-auroral latitudes and the South Atlantic Anomaly. The morphology and intensity of the noise correlates strongly with environmental conditions such as spacecraft potential. In order for the ground processing software to extract individual emission features from the measured spectra, the data must be filtered for quality and the noise must be characterized on short time scales and introduced as additional basis functions for use with the Multiple Linear Regression (MLR) feature extraction algorithm. New algorithms, in the form of an Ion Noise Filter, have been developed for use with the MLR. The techniques used in the Ion Noise Filter are discussed and examples of the successful extraction of spectra are demonstrated.

Efforts at the U.S. Army Research, Development and Engineering Center (ARDEC) at Picatinny, New Jersey are focused on developing methods to counter GPS jamming and electronic warfare (EW) threat by eliminating GPS dependency entirely. In addition, the need for munitions cost reduction requires alternatives to expensive high-grade inertia components. Efforts at ARDEC include investigations of novel methods for onboard measurement of munitions full position and angular orientation independent of GPS signals or high-grade inertia components. Currently, two types of direct angular measurement sensors are being investigated. A first sensor, Radio Frequency Polarized Sensor (RFPS), uses an electromagnetic field as a reference. A second sensor is based on magnetometers, using the Earth magnetic field for orientation measurement. Magnetometers, however, can only provide two independent orientation measurements. The RFPS may also be used to make full object position and angular orientation measurement relative to a reference coordinate system, which may be moving or stationary. The potential applications of novel RFPS sensors is in providing highly effective inexpensive replacement for GPS, which could be used in a "Layered Navigation" scheme employing alternate referencing methods and reduce the current dependency on GPS as a primary reference for guided gun-fired munitions. Other potential applications of RFPSs is in UAVs, UGVs, and robotic platforms.

The use of collimators and shields for measurements and imaging with X- and γ -rays requires a well-defined collimation for the pixels and well-determined formula for the effect of the collimators. We analyze the geometric effects of tubular and pinhole collimators and the effects of curved shields for the case of omni-directional fluxes. These effects can affect measurements of X- and γ-rays as well as UV rays behind the shield and collimators. On the other hand, such effects can be used to enhance the capability of multi-spectral sensors by using appropriate covers in front of them.

The application of fiber grating sensing technology in fire alarming based on temperature detection has the advantages of high accuracy, high reliability and strong immunity from electronic and magnetic fields. It is especially advantageous to use this system in the petroleum and chemistry industry because it can provide an extraordinary safe means for the fire alarm. But due to the traditional optical Wavelength Division Multiplexing (WDM) technology is limited by the optic source bandwidth, the number of its multiplexing points is few. In this paper WDM technology will be developed mixing with Identified Bragg, which is called Identified and Wavelength Multiplexing, to build the Fiber Grating (FBG) fire alarm system integrated with computers. Some technologies applied in fire alarming system of fiber grating such as the transmission of test signals which pass through modulate and demodulate, the disposal of software system, the output of control signal and the strong ability of anti-disturbance have been studied and discussed.

In this paper, our present work, which aimed at investigating a novel optical fiber biochemical sensor based on long period grating (LPG), is introduced. Biochemical sensor is one of the most attractive fields of sensor research, especially with the development and occurrence of all kinds of novel theory and technology such as LPG. When there is a refraction index periodic perturbation, the guiding mode and cladding mode in LPG couple with each other. This make the LPG is sensitive to the ambient refractive index. This means it can be a novel bio-chemical sensor when it is applied in the fields of biochemistry. After investigating the principle of coupling in LPG, where the formulas of resonance wave length and band width are induced by 3-layer step index model, we developed an optical fiber biochemical sensor. The structure of its probe is designed by coating some function films whose thickness is between several tens and several hundreds nanometers on the cladding of optical fiber. Experiments of monitoring the saline separateness process of Bovine Serum Albumin (BSA) and Mice-Immunoglobulin G (M-IgG) by using the developed LPG sensor have been done. The monitoring indicated that for the BSA, the saline separateness occurs when the saturation is between 50% and 60%, for the M-IgG, the percentage is between 30%-40%. Besides the monitoring, the experiments could also analyze the effects of protein type (different molecule structure), protein consistency and saline saturation to saline separateness. The experimental results show that the optical fiber biochemical sensor based on LPG has many advantages such as simple structure, high sensitivity and miniature. It has a promising future in many research fields and application fields.