To get rid of the complex analogue control loops that are traditionally used in resonator fiber optic gyroscope (R-FOG) and to meet the requirements of high accuracy as well as small-size and light-weight in Inertial Navigation Systems (INSs), a digital controller is developed and demonstrated experimentally to control the R-FOG with the digital serrodyne modulation. The digital controller is designed to implement the function of tracking the laser diode frequency drift and to compensate for the imperfect 2π modulation voltage of the phase modulator for the serrodyne modulation. To acquire the resonant frequency, the digital serrodyne modulation with symmetric frequency shift is adopted as a counter-measure for Rayleigh backscattering noise. The optimal serrodyne modulation generated frequency shift is decided to be in the range of 100~120 kHz according to the numerical calculation. The successful demonstration of the open loop operation with the digital controller is deemed as the basis for the digitalized closed-loop experiment in future.

A compact cell phone size radio frequency (ZigBee) wireless strain measurement sensor system to measure the structural strain deformation was developed. The developed system provides an accurate strain measurement data stream to the Internet for further Diagnostic and Prognostic (DPS) correlation. Existing methods of structural measurement by strain sensors (gauges) do not completely satisfy problems posed by continuous structural health monitoring. The need for efficient health monitoring methods with real-time requirements to bidirectional data flow from sensors and to a commanding device is becoming critical for keeping our daily life safety. The use of full-field strain measurement techniques could reduce costly experimental programs through better understanding of material behavior. Wireless sensor-network technology is a monitoring method that is estimated to grow rapidly providing potential for cost savings over traditional wired sensors. The many of currently available wireless monitoring methods have: the proactive and constant data rate character of the data streams rather than traditional reactive, event-driven data delivery; mostly static node placement on structures with limited number of nodes. Alpha STAR Electronics' wireless sensor network system, ASWN, addresses some of these deficiencies, making the system easier to operate. The ASWN strain measurement system utilizes off-the-shelf sensors, namely strain gauges, with an analog-to-digital converter/amplifier and ZigBee radio chips to keep cost lower. Strain data is captured by the sensor, converted to digital form and delivered to the ZigBee radio chip, which in turn broadcasts the information using wireless protocols to a Personal Data Assistant (PDA) or Laptop/Desktop computers. From here, data is forwarded to remote computers for higher-level analysis and feedback using traditional cellular and satellite communication or the Ethernet infrastructure. This system offers a compact size, lower cost, and temperature insensitivity for critical structural applications, which require immediate monitoring and feedback.

The reliable, accurate and low cost measurement of angular position is an important challenge for numerous industries such as aerospace or automotive industries. We propose a new optical fiber angular position sensor connected to an automotive power steering column. This sensor allows the measurement of the angular position of a car steering wheel over a large range (± 3 turns of wheel). The wheel rotation induces micro-bending in the transducer part of the optical fiber sensing system. This system operates as an amplitude modulation sensor based on mode coupling in the transducing fiber in the case when all the modes are equally excited. We study the sensor's response both theoretically and experimentally with a multimode step index optical fiber [Rf (fiber radius) = 300μm; rc (core radius) = 50μm; n_c (core index) = 1,457; N.A. = 0, 22 and the wavelength is 632, 8 nm at the ambient Temperature (20°C)]. This sensor has been tested between (-3x360) and (+3x360) degrees with 0,147 sensitivity. We show that the sensitivity can be controlled as a function of the sensor's length and the study of the sensor's output power as a function of the angular position has been achieved. We compare modeling and experimental validation and we conclude by a perspective of what could be soon an industrial sensor.

Hydrogen detection in space application is very challenging; public acceptance of hydrogen fuel would require the integration of a reliable hydrogen safety sensor. For detecting leakage of cryogenic fluids in spaceport facilities, launch vehicle industry and aerospace agencies are currently relying heavily on the bulky mass spectrometers, which fill one or more equipment racks, and weigh several hundred kilograms. Optical hydrogen sensors are intrinsically safe since they produce no arc or spark in an explosive environment caused by the leakage of hydrogen. Safety remains a top priority since leakage of hydrogen in air during production, storage, transfer and distribution creates an explosive atmosphere for concentrations between 4% (v/v) - the lower explosive limit (LEL) and 74.5% (v/v) - the upper explosive limit (UEL) at room temperature and pressure. Being a very small molecule, hydrogen is prone to leakage through seals and micro-cracks. This paper describes the development of fiber optic emerging technologies for detection of hydrogen in space applications. These systems consisted of Micro Mirror, Fiber Bragg grating, Evanescent Optical Fiber and Colorimetric Technology. The paper would discuss the sensor design and performance data under field deployment conditions.

In a recent study (1) on transportation infrastructure, the results are very disturbing. It states that 83% of the United States transportation infrastructure in not capable of meeting the needs of the next 10 years. While other countries have been more aggressive in infrastructure development and monitoring, the United States is lagging behind. There are a broad range of infrastructure sensing applications in transportation that are not being met. Many of these vital assets are aging or not adequately monitored with the potential for catastrophic failure. As examples, the bridge failure in Minneapolis, Minnesota was due to a structural failure. Fire safety problems, with recent life-loss fires, in road tunnels are challenging due to specific features of their infrastructure, nature of traffic using them and insufficient safety rules on vehicles. As a result, road tunnel fire safety issues are a concern. NIST has recognized the need and is funding innovative research for the development of infrastructure monitoring and inspection technologies. Specifically, NIST through its Technology Innovation Program (TIP) will fund the development of a network of distributed, integrated sensor architectures that will monitor bridges, roadways, tunnels, dams and other critical infrastructure applications (2) Many of these applications can be facilitated by using fiber optic sensors. This paper will specifically address monitoring bridges and tunnels using distributed fiber optic sensors to monitor strain, vibration, temperature and the associated benefits.

In this work, we report a theoretical study for optimizing the optical components choice to design a new low cost and high performances multimode fiber optic gyroscope (MFOG). This study shows that high performances can be obtained by using all optical components with the same SI 50/125 multimode optical fiber associated with low coherence light source, such as a LED, and a photodetector with large active area. For further improvement of MFOG performances, we present a detailed analysis of the photo-detection circuits design considerations.

The increasing trend to use vision sensors in transportation is driven both by legislation and consumer demands for higher safety and better driving experiences. Awareness of what surrounds an automotive vehicle can directly affect the safe driving and maneuvering of that vehicle. Consequently, panoramic 360° field-of-view (FoW) imaging is becoming an industry prerequisite. However, to obtain a complete view of the area around a vehicle, several sensor systems are necessary. This paper explains how panomorph optics can satisfy the needs of various vision applications with only one sensor or panomorph lens configuration. A panomorph lens is a hemispheric wide-angle anamorphic lens with enhanced resolution in a predefined zone of interest. Because panomorph lenses feature an optimal pixel-per-degree relationship, the resulting vision systems provide ideal area coverage, which in turn reduces and maximizes the processing. Here we present how panomorph technology is one of the most promising ways to integrate many automotive vision applications (processing/viewing) onto one single camera module. For example: a single panomorph sensor on the front of a vehicle could provide all the information necessary for assistance in crash avoidance, lane tracking, early warning alerts, parking aids, road sign and pedestrian detection, as well as various video monitoring views for difficult areas such as blind spots. Keywords: wide-angle lens, panoramic, panomorph, immersive, hemispheric, anamorphic, 360° vision systems, vision sensors, automotive vehicles, field of view, transportation, driver assistance systems, lane tracking, blind spot, pedestrian detection, road sign detection, parking assistance

Liquid hydrogen and oxygen are widely used as fuels in space vehicles. Because both are highly dangerous materials prone to explosion, detection of the liquid level in fuel tank becomes a critical element for the safety and efficiency in space operations. Two liquid level sensing techniques are presented in this paper. The first technique is based on optical fiber long period gratings. In this technique, the full length of a specially fabricated fiber is the body of the probe becomes the length of the sensing fiber that is submerged in the liquid can be detected by the interrogation system. The second system uses optical fibers to guide light to and from an array of point probes. These probes are specially fabricated, miniature optical components which reflects a substantial amount of light back into the lead fiber when the probe is gas but almost no light when it is in liquid. A detailed theoretical study by computer simulation was carried out on these two techniques in order to determine which technique was more suitable for experimental investigation. The study revealed that although the first technique may provide more potential benefits in terms of weight and easy installation; a number of technical challenges make it not suitable for a short term solution. The second, probe array based technique, on the other hand, is more mature technically. The rest of the research program was therefore focused on the experimental investigation of the probe array detection technique and the test results are presented in this paper.

The US Port Security Agency has strongly emphasized the needs for tighter control at transportation hubs. Distributed arrays of miniature CMOS cameras are providing some solutions today. However, due to the high bandwidth required and the low valued content of such cameras (simple video feed), large computing power and analysis algorithms as well as control software are needed, which makes such an architecture cumbersome, heavy, slow and expensive. We present a novel technique by integrating cheap and mass replicable stealth 3D sensing micro-devices in a distributed network. These micro-sensors are based on conventional structures illumination via successive fringe patterns on the object to be sensed. The communication bandwidth between each sensor remains very small, but is of very high valued content. Key technologies to integrate such a sensor are digital optics and structured laser illumination.

On July 18, 2008, the FAA mandated that new aircraft are to include inerting technology to significantly reduce the potential for flammable vapor spaces in center wing fuel tanks. All passenger aircraft constructed since 1991 must also be retrofitted with this technology. This ruling is the result of 18 aircraft that have experienced fuel tank flammable vapor ignition incidents since 1960. Included in these are the TWA 800 and Avianca Flight 203 incidents that resulted in 337 total fatalities. Comprised of heavier hydrocarbon components, jet fuel is much less volatile, with Jet A having a flash point of approximately 100°F and JP-4 having a flash point of approximately 0°F. In contrast, straight-run gasoline has a flash point of approximately -40°F. The flash point is the minimum temperature where a liquid fuel can generate enough vapor to form a flammable mixture with air. If the temperature is below the flash point there isn't enough fuel evaporating to form a flammable fuel-air mixture. Since jet fuel and gasoline have similar flammable concentration limits, gasoline must produce much more vapor at a given temperature to have such a low flash point; hence gasoline is much more volatile than jet fuel. In this paper we explore Fluorescence Technology as applied to the design and development of O2 sensors that can be used for this application and discuss the various test and measurement techniques used to estimate the O2 gas concentration. We compare the various intensity based approaches and contrast them with the frequency domain techniques that measure phase to extract fluorescent lifetimes. The various inerting fuel tank requirements are explained and finally a novel compact measurement system using that uses the frequency heterodyning cross correlation technique that can be used for various applications is described in detail while the benefits are explored together with some test data collected.

Modern day propulsion systems are used in aerospace applications for different purposes. The aerospace industry typically requires propulsion systems to operate in a rocket mode in order to drive large boost vehicles. The defense industry generally requires propulsion systems to operate in an air-breathing mode in order to drive missiles. A mixed system could use an air-breathing first stage and a rocket-mode upper stage for space access. Thus, propulsion systems can be used for high mass payloads and where the payload is dominated by the fuel/oxidizer mass being used by the propulsion system. The pulse detonation wave engine (PDWE) uses an alternative type of detonation cycle to achieve the same propulsion results. The primary component of the PDWE is the combustion chamber (or detonation tube). The PDWE represents an attractive propulsion source since its engine cycle is thermodynamically closest to that of a constant volume reaction. This characteristic leads to the inference that a maximum of the potential energy of the PDWE is put into thrust and not into flow work. Consequently, the volume must be increased. The technical community has increasingly adopted the alternative choice of increasing total volume by designing the engine to include a set of banks of smaller combustion chambers. This technique increases the complexity of the ignition subsystem because the inter-chamber timing must be considered. Current approaches to igniting the PDWE have involved separate shock or blast wave initiators and chemical additives designed to enhance detonatibility. An optical ignition subsystem generates a series of optical pulses, where the optical pulses ignite the fuel/oxidizer mixture such that the chambers detonate in a desired order. The detonation system also has an optical transport subsystem for transporting the optical pulses from the optical ignition subsystem to the chambers. The use of optical ignition and transport provides a non-toxic, small, lightweight, precisely controlled detonation system.

We report on the use of thin film coatings, both single and multi-layered, deposited on the flat side of a lapped, D-shaped fibre to enhance the sensitivity of two kinds of surface plasmon resonance based optical fibre sensors. The first kind involves the use of a tilted Bragg grating inscribed within the fibre core, prior to fibre coating, while the second relies on a surface relief grating photoinscribed after the fibre has been coated. Some of the devices operate in air with high coupling efficiency in excess of 40dB and an estimated index sensitivity of Δλ/Δn = 90nm from 1 to 1.15 index range showing potential for gas sensing. Other sensors produced index sensitivities (Δλ/Δn) ranging from 6790nm to 12500nm in the aqueous index regime. The materials used for these fibre optical devices are germanium, silica, silver, gold and palladium.

Micro/nanomanufactured electromagnetic metamaterials in the THz spectral range may help extending the use of metamaterials in transportation. S-string based THz metamaterials as manufactured by SSLS, in particular, the meta-foil, provide a promising platform for applications. Special emphasis may be given to antennas being conformal or quickly steerable or tunable for inter-traffic communication. Achievements by SSLS in co-operation with MIT and Zhejiang University are discussed and potential applications outlined.

The process of optical imaging and the use of a glass lens have been hitherto inseparable since it is the lens that is responsible for mapping incoming rays to form an image. While performing this critical role, the lens, by virtue of its geometry and materials composition, presents constraints on the size, weight, angular field of view, and environmental stability of an optical imaging system as a whole. Here, a new approach to optical imaging is presented. Tough polymeric light-sensing fibers are suspended on a frame to form large-scale, low-density, two- and three-dimensional photonic meshgrids. While a single grid can indeed locate a point of illumination, it is the stacking of a multiplicity of such grids, afforded by their essential transparency, which allows for the detection of the direction of illumination with a wide angular field of view. A surface-spanning-arrangement of such fibers is used to extract an arbitrary optical intensity distribution in a plane using a tomographic algorithm. Lensless imaging is achieved by a volumetric fiber assembly that extracts both the phase and intensity distributions of an incoming electromagnetic field, enabling one to readily determine the object from which the field originally emanated.

We present a novel technique to fabricate low cost mass replicable plastic HUDs for the transportation industry. HUD are implemented in numerous sectors today (in avionics, automobile, military, machinery,...). Typical implementations include an optical combiner which produces the desired virtual image while leaving the field mostly unaffected by the optics. Such combiners optics are usually implemented as cumbersome catadioptric devices in automobile, dichroic coated curved plates, or expensive volume holograms in commercial and military aviation. We propose a novel way to design, model and fabricate combiner masters which can be replicated in mass by UV casting in plastic. We review the various design techniques required for such elements and the novel mastering technology.

Recently there has been strong interest in wireless white LED (WLED) communication link applications in airplanes and avionics platforms for size, weight, cost, and electromagnetic interference (EMI) reduction. Wireless WLED link has additional advantage of providing network security because the optical signal from WLED link is well confined within an airplane or avionics vehicle. In this paper we discuss and analyze commercial-off-he-shelf WLED design and color measurement results. An experimental implementation of a low cost WLED transceiver which shows error free freespace operation at 10Mb/s is successfully demonstrated. The feasibly of implementing free space optical link which meets both lighting and communication requirements using WLED array is analyzed by mathematical modeling using MATLAB simulation technique.

Space-based optical communications using satellites in low earth orbit (LEO) and Geo-synchronous orbits (GEO) hold great promise for the proposed Internet in the Sky network of the future. Building high speed communications network using optical links in space has proven to be an extremely complicated task and many such schemes were tried without success in the past. However in the last few years, there has been impressive progress made to bring the concept to fruition in civilian and government-non classified projects. Laser Communications offer a viable alternative to established RF communications for inter-satellite links and other applications where high performance links are a necessity. High data rate, small antenna size, narrow beam divergence, and a narrow field of view are characteristics of laser communications that offer a number of potential advantages for system design. This paper will focus on the requirements of the spacebased lasers and optics used for beam forming, as well as receiver antenna gain and detectors used in free space communications. Also discussed are the critical parameters in the transmitter, channel, receiver, and link budget that are employed in successful inter-satellite communications system.

Today, the ever increasing number of controls in automobile and aviation cockpits leads to the cluttering of various interfaces (keyboards, switches, panels, etc...). LCD touch screens have proved to be a good alternative to reduce cluttering by reconfiguring in real time different interfaces, appearing on demand as they are needed by the user. However, the underlying screen still remains cumbersome and fragile glass device. We present a novel way to produce virtual consoles and interfaces by projecting diffractive images and sensing the position of the fingers by the use of IR diffractive optics.

Thermites are energetic materials which are made of a metallic oxide mixed with a reducing metal1. The reactivity of classical thermites is moderate but it can be substantially improved when micron-sized particles are replaced by nanoparticles. In this paper, three examples of nanothermites are given in order to illustrate the contribution of these nanomaterials in the future spatial and defence applications: - the incidence of the size of the metallic oxide particles on the reactivity was illustrated by the case of WO₃/Al nanothermites, - the correlation between the composition/structure of the oxide phase and the reactivity was achieved on Al_xMo_yO_z/Al nanothermites, - the fabrication of Gas Generating Nanothermites was performed by adding military explosives in porous mineral oxides (Cr₂O₃; MnO₂) used to fabricate nanothermites.

The research discussed below describes experiments and computer simulations involving propagation of polarized radiation in optical fiber cables designed for use in aircraft environments. The main concern of this effort is optical fiber link systems that are installed in military aircraft. Propagation of polarized radiation in a single mode fiber can be theoretically described with electromagnetic field equations for a bounded system. The state of propagation of the radiation polarization will be affected by environmental stress and strain on the fiber, by imperfections within the fiber, cracks or breaks in the fiber across the fiber optical axis, and by a variety of discontinuities at fiber connectors. The transmission, reflection, and scattering of radiation within an optical fiber affected by these various effects results in mode changing of propagating radiation within the fiber. Mode changing effects by imperfection in the fiber link system have been experimentally measured. The experimental results discussed below are preliminary results and applicable to modeling techniques in the future.

Non-destructive testing of critical structural components is time consuming, while necessary for maintaining safe operation. Large aerospace structures, such as the vertical stabilizers of aircraft undergo inspection at regular intervals for damage diagnostics. However, conventional techniques for damage detection and identification before repair can be scheduled are conducted off-line and therefore can take weeks. The use of guided ultrasound waves is being investigated to expedite damage detection in composites. We measure the frequency dependent loss of ultrasonic guided waves for a structure comprising a boron-nitride composite skin sandwiching an aluminum honeycomb. A wide range of ultrasound frequencies propagate as measured using PZTs, with the lowest attenuation observed about 200-250 kHz. These measurements are confirmed using optical fiber Bragg grating arrays used as ultrasound transducers.