This paper describes the first successful fiber optic oxygen detection sensor systems developed for the Boeing Delta IV Launch Vehicle harsh environment of engine section. It illustrates a novel multi-point fiber optic microsensor (optrode) based on dynamic luminescence quenching that was developed for measuring oxygen leak detection for the space applications. The sensor optrodes employ the quenching by oxygen of the fluorescence from a ruthenium complex. These optrodes were fabricated using Ruthenium-based fluorescent indicator immobilized in a porous glass rod placed at the end of multimode fiber. The light from a blue LED is launched into the optrode via a fiber optic bundle and used as the excitation source. The optrode’s fluorescent emission intensity in the range of 0% to 10% oxygen is measured as a function of time. The measuring system is based on high reliability and low cost. The system consists of four units: 1) temperature compensated oxygen optrodes combined with an optical setup, 2) multipoint sensor communication fiber optic network cable, 3) digital/analogue optoelectronic signal processing unit with built-in micro controller for control of data acquisition and processing, and 4) a laptop computer for data display and storage. In testing, the sensor exhibited excellent response time and reversibility. To qualify the sensors, performed detail investigation for thermal, humidity, temperature, vibration and accelerate testing for life expectancy of harsh environmental of engine section. Extensive networking using MatLab were carried out for lab and actual field demonstrations.

Triboluminescent phosphors provide a method for converting kinetic signals to optical signals for particle detection. Several methods, including vapor deposition, electron beam, and spray-on were evaluated for depositing a thin translucent coating of ZnS:Mn phosphor material onto transparent substrates. The objective was to be able to optically detect impact events on the back side of the substrate while still retaining some capacity to view distant optical events. During the experiments, optical detectors within a light-tight test chamber were used to measure the optical signals generated by the coatings. The measurements resulted from optical signals that were generated by particle impacts and sample phosphorescence, along with electrical interferences between the particle sources, the ambient background, and the detectors. Signal levels and translucency measurements from various coatings are described, along with lessons learned about the coating processes, the detectors, and the limitations of the measurements.

We present a study of a fiber optic sensor for leak detection based on Surface Plasmon Resonance (SPR). We use Palladium as the sensitive material for hydrogen detection. In this configuration, the transducer layer is a multilayer stack made of a silver, a silica and Pd layer. The spectral modulation of the light transmitted by the fiber allows to detect hydrogen on the environment. The multilayer thickness defines the sensor performance. The silica thickness tunes the resonant wavelength whereas the silver and Pd thickness determines the sensor sensitivity. The study of the sensor performance as function of several thicknesses (Pd/Si/Ag) is achieved and we present the optimal configuration at a concentration of 4% hydrogen in argon.

With the increase worldwide demand for hydrocarbon fuels and the vast development of new fuel production and delivery infrastructure installations around the world, there is a growing need for reliable fuel leak detection technologies to provide safety and reduce environmental risks. Hydrocarbon leaks (gas or liquid) pose an extreme danger and need to be detected very quickly to avoid potential disasters. Gas leaks have the greatest potential for causing damage due to the explosion risk from the dispersion of gas clouds. This paper describes progress towards the development of a fast response, high sensitivity, distributed fiber optic fuel leak detection (HySens^TM) system based on the use of an optical fiber that uses a hydrocarbon sensitive fluorescent coating to detect the presence of fuel leaks present in close proximity along the length of the sensor fiber. The HySense^TM system operates in two modes, leak detection and leak localization, and will trigger an alarm within seconds of exposure contact. The fast and accurate response of the sensor provides reliable fluid leak detection for pipelines, tanks, airports, pumps, and valves to detect and minimize any potential catastrophic damage.

There exist several image-enhancement algorithms and tasks associated with imaging through turbulence that depend on defining the quality of an image. Examples include: “lucky imaging”, choosing the width of the inverse filter for image reconstruction, or stopping iterative deconvolution. We collected a number of image quality metrics found in the literature. Particularly interesting are the blind, “no-reference” metrics. We discuss ways of evaluating the usefulness of these metrics, even when a fully objective comparison is impossible because of the lack of a reference image. Metrics are tested on simulated and real data. Field data comes from experiments performed by the NATO SET 165 research group over a 7 km distance in Dayton, Ohio.

Spinel is a rugged ceramic transparent from ultraviolet to midwave infrared (0.18 – 5.5 μm) wavelengths. It has the best transmission from 4-5 μm among the competing materials ALON and sapphire with comparable mechanical properties. We have developed low absorption loss spinel as an exit window aperture for High Energy Laser systems. We demonstrated that spinel possesses excellent thermo-optical characteristics required for the High Energy Laser systems and at the same time it can provide the necessary ruggedness desired for the realistic and harsh battlefield environment. We have demonstrated through testing that spinel can withstand very adverse conditions of rain, sand storms and salt fog conditions without any change in its optical performance. We have also developed rugged anti-reflective coatings and anti-reflective surface structures to maintain high optical transmission in adverse environment.

With the advanced of instrument design for space exploration and NIR application, the optical systems working at cold temperature become more and more common. Over the past, many lens system has been used at cryogenic temperature making available a lot of cryogenic material data including CTEs and index of refraction. It is now more accessible than ever to design cryogenic lens system. However making a lens design working at cryogenic temperature is still a challenge. To avoid any problem during operation (mostly at cold temperature), both optical and mechanical designer must work together. This paper gives a modest overview of the most recent progress in this field. It provides the basic knowledge that can be used by both lens and mechanical designers to perform cryogenic optical design with success.

We review in this paper the various architectures that have been proposed in industry to implement see-through head-mounted display (HMD), especially for the consumer electronics market.

“Lucky-region fusion” (LRF) is an image processing technique that has proven successful in enhancing the quality of images distorted by atmospheric turbulence. The LRF algorithm extracts sharp regions of an image obtained from a series of short exposure frames, and “fuses” them into a final image with improved quality. In previous research, the LRF algorithm had been implemented on a PC using a compiled programming language. However, the PC usually does not have sufficient processing power to handle real-time extraction, processing and reduction required when the LRF algorithm is applied not to single picture images but rather to real-time video from fast, high-resolution image sensors. This paper describes a hardware implementation of the LRF algorithm on a Virtex 6 field programmable gate array (FPGA) to achieve real-time video processing. The novelty in our approach is the creation of a “black box” LRF video processing system with a standard camera link input, a user controller interface, and a standard camera link output.

Head Mounted Displays (HMDs), and especially see-through HMDs have gained renewed interest in recent time, and for the first time outside the traditional military and defense realm, due to several high profile consumer electronics companies presenting their products to hit market. Consumer electronics HMDs have quite different requirements and constrains as their military counterparts. Voice comments are the de-facto interface for such devices, but when the voice recognition does not work (not connection to the cloud for example), trackpad and gesture sensing technologies have to be used to communicate information to the device. We review in this paper the various technologies developed today integrating optical gesture sensing in a small footprint, as well as the various related 3d depth mapping sensors.

Low cost see-through technologies for wearable AR displays have been an elusive key element to enable the market for consumer oriented mobile AR. This paper will explore the various available technologies and the key challenges to develop a platform that will enable affordable wearable displays for the consumer and professional market.

Extensive peer reviewed scientific research has demonstrated the utility of polarization difference imaging (PDI) to reveal subtle surface details and textures in poor lighting conditions caused by fog, smoke, clouds or turbid water. We present sample results of a new real time PDI camera showing the ability of the camera to enhanced imaging harsh environments, particularly in turbid water.

Light-emitting diodes (LEDs) are becoming common as energy efficient light sources. Their long life, small footprint and low energy consumption show great promise in many applications including those that relate to harsh environments. However, in designing an efficient light source, a mathematical model is required. The development of such a mathematical model was identified as a priority task by the U.S. Department of Energy in 2010 for general lighting. In this paper, we report an experiment involving two high-power white LED models which were stressed with different currents and junction temperatures. It shows the large variation between different models and stress conditions that takes place in the degradation process. This is part of an effort to develop a tool for the simulation of LED degradation for harsh environment lighting conditions.

Solid state lighting technology has made great advances over the last decade and has become the technology of choice to displace legacy incandescent and as well as the more efficient fluorescent lights. While efficiencies have been improved and cost of the LEDs has been steadily lowered still many challenges exist in the thermal, electrical, optical, and packaging implementations.

The extremum of a real-valued nonanalytic function of a complex variable that defies Cauchy-Riemann equations can be found using formal derivatives. This letter shows how the first and second derivative tests can be recast via formal gradient and formal Hessian. The elegance of the method is illustrated with examples.

Recent development in High Power LED (HPL) is poised to replace traditional lighting sources such as Fluorescent, HID, Halogen and conventional incandescent bulbs in many applications. Due to the solid state compact nature of the light source it is inherently rugged and reliable and has been the favored lighting source for most indoor and outdoor applications including many hazardous locations that impact, and safety environments including mining, bridge, aerospace, and automotive . In order to accelerate this transition many enhancements and advances are taking place to improve on the reliability, and thermal performance of these devices.

With the use of large LED arrays, it is possible to generate large heat loads at the system level which can cause challenges for overall heat dissipation, especially when cooling requirements call for passive methods. These two challenges work together to cause elevated LED die temperatures, which have been linked to lower quantum efficiencies, shorter lifetimes, emission wavelength shifts and catastrophic device failure. It has been predicted previously that the lifetime of a device decays exponentially as the temperature increases. This can result in a lifetime decrease from 42,000 hours to 18,000 hours when the device temperature increases from 40°C to 50°C.

This paper explores the various improvements and advances made in the micro-packaging of LEDs to enhance their performance.

The paper proposes the diagnostic and prognostic modeling and test validation of a Wireless Integrated Strain Monitoring and Simulation System (WISMOS). The effort verifies a hardware and web based software tool that is able to evaluate and optimize sensorized aerospace composite structures for the purpose of Structural Health Monitoring (SHM). The tool is an extension of an existing suite of an SHM system, based on a diagnostic-prognostic system (DPS) methodology. The goal of the extended SHM-DPS is to apply multi-scale nonlinear physics-based Progressive Failure analyses to the “as-is” structural configuration to determine residual strength, remaining service life, and future inspection intervals and maintenance procedures. The DPS solution meets the JTI Green Regional Aircraft (GRA) goals towards low weight, durable and reliable commercial aircraft. It will take advantage of the currently developed methodologies within the European Clean sky JTI project WISMOS, with the capability to transmit, store and process strain data from a network of wireless sensors (e.g. strain gages, FBGA) and utilize a DPS-based methodology, based on multi scale progressive failure analysis (MS-PFA), to determine structural health and to advice with respect to condition based inspection and maintenance. As part of the validation of the Diagnostic and prognostic system, Carbon/Epoxy ASTM coupons were fabricated and tested to extract the mechanical properties. Subsequently two composite stiffened panels were manufactured, instrumented and tested under compressive loading: 1) an undamaged stiffened buckling panel; and 2) a damaged stiffened buckling panel including an initial diamond cut. Next numerical Finite element models of the two panels were developed and analyzed under test conditions using Multi-Scale Progressive Failure Analysis (an extension of FEM) to evaluate the damage/fracture evolution process, as well as the identification of contributing failure modes. The comparisons between predictions and test results were within 10% accuracy.

Acoustic emission sensing is a leading structural health monitoring technique use for the early warning detection of structural damage associated with impacts, cracks, fracture, and delaminations in advanced materials. Current AE systems based on electronic PZT transducers suffer from various limitations that prevent its wide dynamic use in practical avionics and aerospace applications where weight, size and power are critical for operation. This paper describes progress towards the development of a wireless in-flight distributed fiber optic acoustic emission monitoring system (FAESense™) suitable for the onboard-unattended detection, localization, and classification of damage in avionics and aerospace structures. Fiber optic AE sensors offer significant advantages over its counterpart electronic AE sensors by using a high-density array of micron-size AE transducers distributed and multiplex over long lengths of a standard single mode optical fiber. Immediate SHM applications are found in commercial and military aircraft, helicopters, spacecraft, wind mil turbine blades, and in next generation weapon systems, as well as in the petrochemical and aerospace industries, civil structures, power utilities, and a wide spectrum of other applications.

The combination of fossil fuels with bio-fuels, specially ethanol and methanol, has acquired relevance and attention in several countries in recent years. A variety of factors have induced this trend: market prices, constant geopolitical events, new sustainability policies and laws, etc. The fuels used in the automotive industry, including bio-fuels, normally contain additives as anti-shock agents and as octane booster. These additives may endanger (beside the high volatility implied) public health or environment due to the nature of its chemical composition.

Raman spectral information from different additives, specially toluene, contained in E10 gasoline-ethanol blends has been obtained by using an own-design Fourier-Transform Raman spectrometer (FT-Raman). This information has been also compared with Raman spectra from pure additives and with standard Raman lines in order to validate its accuracy in frequency. The spectral information is presented in the range of 0 cm⁻¹ to 3500 cm⁻¹ with a resolution of 1.66 cm⁻¹. The Raman spectra obtained shows a reduced frequency deviation (less than 0.4 cm⁻¹ when compared to standard Raman spectra from different calibration materials, e.g. cyclohexane and toluene, without compensation for instrumental response).

The Fourier-Transform Raman spectrometer prototype used for the spectral analysis, consisting of a Michelson interferometer and a self-designed photon counter cooled down on a three stage Peltier element arrangement, is able to extract high resolution and precise Raman spectra from the additives in the fuels analyzed. The proposed FT-Raman prototype has no additional complex hardware or software control. The mechanical and thermal disturbances affecting the FT-Raman system are mathematically compensated by extracting the optical path information from the generated interference pattern of λ = 632.8nm Helium-Neon laser (HeNe laser), which is used at the spectrum evaluation. This allows the device to be used in complicated environments where certain level of security is required (e.g. fuel production, storage, transportation, etc.).

A fiber optic system can be designed, assembled and installed with many options for active and passive components and system elements. Interconnection systems should be designed with a detailed BOM, including fiber/cable, connectors, ruggedization materials and other passive components for the desired application. The selection of these items should be specific to the requirements of the system when considering environmental and mechanical limitations, and from the standpoint of the users who will be installing, maintaining and possibly repairing the system sometime in the future. Proper installation, maintenance and repair training is essential.

The paper will review various up-to-date alternatives, particularly for mil-aero applications, available when selecting components at design-in stage and discussing options for different scenarios of required optical performance. Considerations of component selection with regard to capabilities of the installers, maintenance and repair personnel and other key people who will be responsible for the success of the system will also be discussed.

Training resources will be discussed. A fiber optic system when compared to an electrical system is not necessarily more difficult to install and maintain, but training for key different issues is a must. With appropriate component selection at the design stage and adequate training of installers/handlers is completed, the fiber optic system will be successful.

Optical latches are important for a wide range of applications including communication systems, optical logic systems, optical random access memory (RAM) and encryption. All optical logic operations using quantum dot (QD) based semiconductor optical amplifier (SOA) and Mach-Zehnder interferometer (MZI) have been studied. The building block of an optical latch such as NAND gate has been fabricated and their operation experimentally demonstrated at ~ 80 GHz. A rate equation model has been developed for the QD-SOA-MZI and it has been used to analyze the Boolean logic operation. The model has been used to analyze the Set-Reset (S-R) latch and the D-Flip-Flop (DFF) devices. The DFF is the basic device for building larger logic circuits. The results show that the latches would work to speeds of ~ 250 Gb/s.

A compact and fast-response wavelength monitor is described that can determine the wavelength of individual laser pulses with a resolution of a few pm. It combines a position-sensitive photo detector with an optical coating that converts the wavelength information of the incident light into a spatial intensity distribution on the photo detector. Differential read-out of the photo detector is used to determine the centroid of this distribution. Wavelength change between individual laser pulses is detected as a shift of the centroid of the spatial light distribution on the detector. The wavelength monitor is demonstrated with results from a wavelength-tunable fiber laser that can produce randomly accessible sequences of laser pulses.

This paper describes micro soldering method of hermetic DIL (dual in line) laser diode module packaging. Normally, reliable, reproducible, high-yield packaging technologies are essential for meeting the cost, performance, and service objectives for the harsh environment of aerospace applications. For this package a new novel technique incorporating microscope with twin micro tweezers, a CCD image captured camera as monitoring probe and preformed rings of Pb-Sn and In-Sn alloys for hermetic sealing using a micro-soldering process was developed. The procedure is able to confine the solder seal to a small region inside the ferrule near the fiber feed-through hole on the wall of the DIL package. After completing the development, which included temperature and thermal cycling and analysis showed the improved method using lead-tin alloy had no fiber damage after the micro-soldering seal. The new process resulted in 100% success in our packaging design.

An imager that can measure the distance from each pixel to the point on the object that is in focus at the pixel is described. Since it provides numeric information of the distance from the camera to all points in its field of view it is ideally suited for autonomous vehicle navigation and robotic vision. This eliminates the LIDAR conventionally used for range measurements. The light arriving at a pixel through a convex lens adds constructively only if it comes from the object point in focus at this pixel. The light from all other object points cancels. Thus, the lens selects the point on the object who's range is to be determined. The range measurement is accomplished by short light guides at each pixel. The light guides contain a p - n junction and a pair of contacts along its length. They, too, contain light sensing elements along the length. The device uses ambient light that is only coherent in spherical shell shaped light packets of thickness of one coherence length. Each of the frequency components of the broad band light arriving at a pixel has a phase proportional to the distance from an object point to its image pixel.

We present successful results obtained for thermal/ vibration testing of ruggedized, IR-transmitting chalcogenide glass fiber cables using a government facility with state-of-the-art equipment capable of MIL-SPEC environmental testing. We will also present results of a direct imprinting process to create novel “moth eye” patterned surfaces on the IR fiber cable ends that significantly reduces endface reflection losses from 17% to less than 3%. The cables with these imprinted “moth eye” ends transmit much higher IR laser power without damage than was obtained for previous cables with traditional AR coatings.

To achieve a very effective automotive power steering system, we need two important data, the angular position of the wheel and the torque applied on the shaft by the driver of the car. We present a new accurate optical fiber angular position sensor connected to an automotive power steering column. In this new design, the sensor allows the measurement of the angular position of a car steering wheel over a large and adjustable range (± several turns of the 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 response both theoretically and experimentally with a multimode step index optical fiber [r_f (fiber radius) = 300 μm; r_c (core radius) = 50 μm; n_c (core index) = 1,457; N.A. = 0, 22 and the wavelength is 632,8 nm at the ambient Temperature (20°C)]. We show that the sensitivity can be controlled as a function of the sensor's length. We compare modeling and experimental validation and we conclude with a perspective on what could soon be an industrial sensor.

Achieving affordable high speed fiber optic communication networks for airplane systems has proved to be challenging. In this paper we describe a summary of the EU Framework 7 project DAPHNE (Developing Aircraft Photonic Networks).

DAPHNE aimed to exploit photonic technology from terrestrial communications networks, and then develop and optimize aircraft photonic networks to take advantage of the potential cost savings. The main areas of emphasis were on: multiplexing networks; providing standard components; simplifying installation; and reducing through life support costs. DAPHNE (fifteen partners from seven nations) finished in February 2013; and was supported by the European Commission‟s Seventh Framework Programme, although the consortium members are continuing with in-house developments.

The use of singlemode fibers on aircraft has been limited due to the perceived robustness of the connection and cost implications compared to multi-mode fiber systems. However, single-mode fibers are required for certain functions such as wavelength division multiplexing, analogue RF over fiber and fiber Bragg grating systems for structural health monitoring. In this paper a selection of connectors using singlemode fibers have been assessed for their operation in the presence of contaminants, both particulate and fluid. Butt-coupled connectors and expanded-beam type connectors were assessed under the same conditions. The results have shown that different connector designs behave differently in the presence of contamination but no single design could perform well over all test conditions. The results of the tests will be presented and discussed.

A full-spectral monitoring (FSM) system utilizing (charged coupled device) CCD array spectroradiometer and optical fiber has been developed and implemented for accelerated laboratory weathering instruments. The system provides in-situ, real-time irradiance monitoring and control. Compared to the conventional photo diode and fixed band pass interference filter radiometer used for irradiance measurement and control, FSM represents a revolutionary step forward for the weathering industry. Additionally a calibration process utilizing an identical xenon lamp used for testing has been developed for the FSM system. This calibration process greatly simplifies the traditional Mercury plus FEL lamps based calibration process. The total measurement uncertainty of this FSM is also analyzed and discussed in the paper.

Plastic Optical Fiber (POF) technology is utilized for wide variety of applications for its easiness of handling and robustness against environmental variation. Thanks to its large core diameter (typically 1mm) and large numerical aperture (typically 0.5) which provides wider acceptance angle, dimensional tolerance of POF can be extremely large. This is the reason why the simple and low cost connection technology can be used with POF.

Among these existing applications, the POF manufactures are primarily focusing on growing automotive and industrial data-com areas. Industrial data-com applications include field-bus system in plant area, power application (power station, sub-station) and locomotive control systems. Automotive data-com with POF is used for In-vehicle networks for infotainment systems or safety information bus.

For these applications, POF is required to be durable against harsh environment such as high temperature (~105C), dynamic mechanical movement for robotic arms and compatibility with machine oil or other chemical substances. To satisfy these application specific requirements, the structure and material of POF and its jacketing are optimally designed. Through these development activities, POF technology evolved into well adopted industrial standard. As an extension of this evolution, aero space application is another great possibility to challenge for POF industry.

The present paper reports the latest technology and the features of those jacketed POF used in these applications, and describe about future possibility for aerospace applications.

We present a novel LP-CPV (Low Power Concentrating Photo-Voltaics) technology well suited for Low Earth Orbit small satellites. The LP-CPV consists of three layers: the first two layers are optical redirection layers which implement non-tracking concentrating functionality and the third one is a support layer for single crystal silicon lamellar strips covering 10% of the overall area. The optical layers are diffractive transparent plastic layers embossed with micro-structures via roll-to-roll embossing. Instead of using spectral dispersion, we use diffraction efficiency modulation to reduce the amount of IR light concentrated on the crystal silicon strips, therefore allowing maximum conversion efficiency even at 10X concentration over silicon. All three layers (concentrating optics and lamellar silicon PV strips) comprise, when deployed, a uniaxial PV system periodic in the other (non-axis) principal in-plane direction. The layers can be rolled together in one compact cylindrical roll to minimize the payload volume. The entire LP-CPV system can then be deployed/unrolled in space and held in place, but can also be rolled back in order to prevent damage from solar flares, micro-meteorites, etc.

This paper will focus on the trends for the space-based lasers, optics and terminals used in the intersatellite networks. Reviewed and evaluate the recent development in the space-based laser technologies and the critical parameters that are employed for successful high-speed inter-satellite communications systems.

Building laser for high speed communications network for the harsh environment of space using optical links in space has proven to be complicated task and many such schemes were tried without success in the past. 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. However in the last few years, there has been impressive progress made to bring the concept of laser-based intersatellite systems 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-based systems and they are just few numbers of potential advantages for system design over radio frequency communication.

We report integrated coherent optical receivers designed specifically for RF Photonics applications. These receivers may be implemented in either single- or dual-polarization (DP) systems which utilize I/Q (in-phase, quadrature) phase modulation. The integrated receivers incorporate a monolithic 90 degree optical hybrid followed by eight high power-handling InGaAs photodiodes. Linear operation to +27 dBm of total optical input power, 20 mA photocurrent per diode, output third-order intercept (OIP3) > 40 dBm, third-order harmonic distortion < -100 dBc, and RF bandwidths > 4 GHz is presented. Such photoreceiver power-handling and linearity is required to optimize the photonic system spurious free dynamic range (SFDR), noise figure (NF) and link gain.

Novel fiber optic transmitter control methodologies, high optical power and low RIN source lasers, high performance photodiodes and DWDM laser capability provide high dynamic range and high capacity transport for a wide range of sensing and communications applications. Measured component and system level test data demonstrates these performance improvements. Higher spur free dynamic range in excess of 110 dB·Hz^2/3 over broad range of K-band frequencies is demonstrated, increasing the practical use of fiber as a transport method for high sensitivity applications. Multichannel DWDM operation provides simplified capacity expansion without compromising system performance, allowing arrayed photonic systems to be deployed. System characterization for a wide range of optical wavelengths and RF frequencies is provided to demonstrate these levels of performance in practical applications. Photonic component cost reductions combined with compact packaging further increase the ability of high performance fiber optic transport to address a wider range of applications, as the size, weight and performance barriers are eliminated. This paper provides a summary of the current state of the art of commercially available photonic components for high performance externally modulated analog optical links from a practical perspective.

Recently, optical fiber transmission lines have flows of huge data including confidential information. Presently, the mathematical cipher is employed in some access systems to protect eavesdropping. However, the cipher break history shows such mathematical cipher is not reliable enough. Such fact demands an urgent development of more reliable cipher and drives us to focus actively on the research and development of physical cipher. Y-00 quantum cipher is an encryption scheme combined with physical phenomena and mathematical cipher, and it provides high speed performance and a provable security. So far, we have applied Y-00 quantum cipher to point-to-point transmission systems. However, secure communication system in the multiple remote point access system from a local point is also important. In this work, we propose a secure multiple point access system using the intensity modulated Y-00 quantum cipher. A one-to-three point transmission system using Y-00 quantum cipher in the wavelength division multiplexing (WDM) scheme is experimentally demonstrated where Y-00 quantum ciphers encrypted with three different secret keys are transmitted from a local point to three users in different remote access points. For the first time to our knowledge, Y-00 cipher communications between users with the correct keys are successfully demonstrated at 2.5-Gb/s data rate while users with the different keys are not able to communicate.

Multiple channels of light can propagate through a multimode fiber without interfering with each other and can be independently detected at the output end of the fiber using spatial domain multiplexing (SDM). Each channel forms a separate concentric ring at the output. The typical single pin-diode structure cannot simultaneously detect and demultiplex the multiple channel propagation supported by the SDM architecture. An array of concentric circular pindiodes can be used to simultaneously detect and de-multiplex the SDM signals; however, an all optical solution is generally preferable. This paper presents simple architecture for an all optical SDM de-multiplexer.

Free Space Optical (FSO) communication is the fusion of wireless technology and optical fiber communications systems. It has the potential of providing fiber optic data rates without the physical restraints of optical fiber cables. This endeavor presents a novel receiver structure with potential for omnidirectional free space optical communications. Interesting approaches for accomplishing omnidirectional free space lasercomm such as direct detection and solar blind non-line of sight UV scattering have been reported over the last few years. However, these technologies have resulted in limited distances of the order of 10 to 100 meters and data rates often limited to less than 1 Mb/s. This endeavor reports the architecture of an omnidirectional receiver setup by integrating an off the shelf detector and a fiber bundle, where the fiber bundle couples omnidirectional photons within its field of view and delivers these photons to the detector. The coupling of light from all directions into a detector is regulated by the cone of the acceptance angle of the fiber. Multiple fibers with overlapping acceptance angles provide the necessary coverage that may be needed to extract the optical signal from the free space optical channel. Simulated results showing the normalized power pattern of the system is presented to demonstrate omnidirectional potential of the structure. Theoretical power level versus distance plot for an FSO System employing On-O Keying (OOK) is also presented.

As ultracold atom sensors begin to see their way to the field, there is a growing need for small, accurate, and robust laser systems to cool and manipulate atoms for sensing applications such as magnetometers, gravimeters, atomic clocks and inertial sensing. In this paper we present a frequency-agile, butterfly packaged laser source, absolutely referenced to an atomic transition. We also present the entire laser system, including a fiber-coupled optical amplifier and liquid crystal shutters, replacing a laboratory table’s worth of optics with a system the size of a paperback novel.

QD Vision has developed Quantum Dot Light Emitting Devices whose emission spans the wavelength range from 1000 nm to 1.35 μm, using tunable, narrow band quantum dot emission. These devices emit sufficient power for long range-detection by a variety of systems, run at very low drive voltages, and are producible in area emitting form-factors that are very thin and light weight. Potential applications for these devices include covert illumination, tagging, display backlighting, and line-of-sight communications.

In this paper, we demonstrate electrically driven quantum dot light emitting devices that emit in the wavelength range of 1000 nm to 1.35 μm, with full-widths at half-maximum as low as 128 nm. The devices discussed are characterized with respect to their efficiency, power output, and lifetime, and this data is used to evaluate their suitability for use in a variety of defense-related applications. Example devices are discussed, including completed prototypes 1.5mm thick with active areas up to 4 cm². Experimental results are presented that demonstrate a low turn-on voltage of 1.4 V, a maximum external quantum efficiency of 2.5 %, a power efficiency of 25 mW/W, and a peak radiance of 18.3 W/sr.m². Lifetimes of more than 1000 hours at operating drive levels are also shown.

A humidity fiber optic sensor based on phase-shifted (PS) fiber Bragg Gratings (FBG) is demonstrated in this paper. The sensor (PS-FBG) is coated with a moisture sensitive polyimide. When this thin coating is exposed to moisture its swells, hence inducing tensile stress on the PS-FBG and affecting its Bragg wavelength. Due to its intrinsic properties, the PS-FBG sensor presents the same trend of wavelength variation as standard fiber Bragg Grating sensor but with higher measurement resolution, and reliable measurements can be obtained in different humidity and temperature environments. This paper assesses the suitability, including sensitivity and response time, of the phaseshifted FBG sensor approach for humidity sensing. By monitoring this change, it is demonstrated that the humidity level of the environment can be accurately monitored.

We present an experimental demonstration of an all optical memory consisting of a single semiconductor optical amplifier as the active medium based on wave mixing. The circuit is a fiber ring consisting of a semiconductor amplifier, a bi-directional 2x2 fiber coupler, an isolator, a polarization controller, and a Faraday mirror. The output is observed on the spectrum analyzer, which consists of the peak wavelength of the SOA plus an additional signal generated through wave mixing, which is tunable within the band gap of the SOA. We shall demonstrate two modes of operation of the device, which will consist of a flip flop switch between three states, as well as a single data storage memory. The stable states consist of two modes, where the mode amplitude represents the state. Mode 1 corresponds to 1500 nanometers and mode 2 corresponds to 1530 nanometers. A contrast ratio between an “on” and “off” state is measured for each mode and the mode of operation is based on the polarization. We shall present the states for the circuit, the effect of drive current on the system, the effect of the SOA structure, wave mixing effects, and how to operate the device for both logic operation and data storage.

Conventional circuit designs have considered only visibility distance and transmission power. However, these are part of circuit design variables. There are a variety of other variables such as modulation method, carrier wave length, type of wavefront. Communication circuits should be designed appropriately depending on the installation environment. This study has performed an evaluation of the propagation characteristics of combinations of each modulation method and carrier waves, and considered indexes for communication circuit designs that suit the installation environment. As a result, the result has been obtained that modulation method needs to be selected depending on the CNR, and the wave length and wavefront of carrier waves depending on the propagation distance.

A Tunable diode laser spectrometer (TDLS) system has been designed to scan the near-surface atmosphere for ammonia gas over a wide range of distances (10 m to 1 Km). Since the system is designed for space applications, it needs to be small, lightweight, and low power, which dictates the use of relatively low frequency measurement scans. The spectrometer uses a diode laser, which is subject to a large 1/f noise component at these low frequencies. In this work, digital signal processing techniques are used to maximize the measurement sensitivity of a low frequency TDLS system depending on Double Fast Fourier Transform (DFFT-BF) based- filter. Simulations of the 1/f noise spectrum and ammonia gas absorption peak were performed using a sinusoidal waveform to drive the diode laser. A DFFT-BF-BF method is proposed that reduces the average of the error in the gas readings to nearly 50 percent. Because, this method decreases the effect of 1/f noise while keeping the measurement signal relatively constant.

The advantages of optical fiber sensing in harsh electromagnetic as well as physical stress environments make them uniquely suited for structural health monitoring and non-destructive testing. In addition to aerospace applications they are making a strong footprint in geophysical monitoring and exploration applications for higher temperature and pressure environments, due to the high temperature resilience of fused silica glass sensors. Deeper oil searches and geothermal exploration and harvesting are possible with these novel capabilities. Progress in components and technologies that are enabling these systems to be fieldworthy are reviewed and emerging techniques summarized that could leapfrog the system performance and reliability.

The purpose of this effort is to apply an in-situ corrosion remote sensing capability in aircraft structural environments. The technique will permit detection of corrosion on and within aircraft structures and component junctions that are susceptible to corrosion, but which are not accessible for visual inspection. The field application configuration includes surface and embedded optical fiber probes interfaced with a Fourier Transform Infrared (FTIR) interferometer for evanescent wave absorption spectroscopic measurements. The mature and fielded technique will allow periodic remote sensing for structural health monitoring and detection of corrosion.

The potential advantages of optical fiber sensors result from the fact that the sensing element, the optical fiber, is small size, light weight, and immune to electromagnetic field. Also it can be attached to surfaces or embedded in junctions in aircraft structures, in locations where humidity and corrosion can accumulate, but cannot be directly observed.