Optical Fiber Array Research Articles

Analytical solutions of the discrete nonlinear Schrödinger equation in arrays of optical fibers

Abstract We find the analytical solutions of the discrete nonlinear Schrodinger equation which models arrays of optical fibers according to the fact that the signal which propagate in the fiber under consideration of the array can be prone to the lateness or accelerating effects of the neighbouring fibers. Firstly, we give the recurrence relation which governs the number of fiber “ n ”and secondly, we apply the projective Riccati method to achieve the resolution.

Multi-instability of gap solitons and dynamics of nonlinear excitations in the array of optical fibers

Abstract The nonlinear localized excitations and gap multi-instability phenomena in the array of optical fibers are investigated analytically by means of the method of multiple scales combined with the averaging method. The perturbative analysis in nonlinear discrete systems leads to a system of four coupled nonlinear oscillated equations without second members. The method of multiple scales is used to show the different possibilities of instability. The averaging method is considered to show how the angular frequency received the perturbation with the evolution of time.

Schemes of a fiber-optic multiplexing sensor array based on a 3×3 star coupler

A Michelson-based fiber-optic low-coherence interferometric quasi-distributed sensing system permitting absolute length measurement in a sensor array is proposed. The main part of the sensing system is a fiberoptic 3 x 3 star coupler. The architecture of fiber-optic sensors can be easily realized as a linear sensor array, twin sensor arrays, or a loop sensor array. The proposed sensing scheme will be useful for the measurement of strain distribution. An important application could be deformation sensing in smart structures. A six-sensor array is demonstrated experimentally.

Fiber optic acoustic sensor technology

Fiber optic sensor technology has been under development for over 25 years, recently a major milestone has been reached- the introduction of the Fiber Optic Wide Aperture Array on the first Virginia class submarine. This paper will review the development of this technology, outlining the principles of operation and the technological developments that led to fiber optic interferometric sensors becoming viable for production in an advanced sonar system. The Fiber Optic Wide Aperture array is a large channel count planar array mounted on the side of the submarine, but fiber sensor technology is also being developed for both towed arrays (as a replacement for the Navy’s thin-line towed arrays) and for bottom mounted acoustic arrays for a number of Navy applications. This paper will describe the development of the fiber optic hydrophones for these applications as well as the optical interrogation techniques. One of the key features of fiber optic sensor technology is the ability to passively multiplex many hydrophone channels per fiber, several multiplexing techniques will also be described. Some of the issues and challenges of this technology, such as coherent noise for large channel count systems will also be briefly discussed.

Utilizing Optical Tomography with Ultrasound Localization to Image Heterogeneous Hemoglobin Distribution in Large Breast Cancers

PURPOSE: Angiogenesis in advanced breast cancers is highly distorted and heterogeneous. Noninvasive imaging that can monitor angiogenesis may be invaluable initially for diagnosis and then for assessing tumor response to treatment. By combining ultrasound (US) and near-infrared (NIR) optical imaging, a reliable new technique has emerged for localizing and characterizing tumor angiogenesis within the breast. METHODS: This new technique employs a commercial US transducer coupled with an array of NIR optical fibers mounted on a hand-held probe. The US image is used for lesion localization and for guiding optical imaging reconstruction. Optical sensors are used for imaging tumor total hemoglobin distribution, which is directly related to tumor angiogenesis. RESULTS: Six large breast carcinomas were studied and microvessel density count was then performed on tissue samples obtained from these cancers. Two patients had locally advanced breast cancers and received neoadjuvant chemotherapy for 3 months. In one patient, before chemotherapy, the total hemoglobin distribution showed a high concentration at the cancer periphery; the distribution was later confined to the core area after 3 months of treatment. In another patient, as treatment progressed, the maximum hemoglobin concentration decreased from 255.3, to 147.5, to 76.9 wmol/I with an associated reduction in spatial extension. The other four patients had cancers of 2.0 to 3.0 cm in size and were imaged either at the time of core biopsy or definitive surgery. The histologic microvessel density counts from these tumor samples correlate to hemoglobin distributions with a correlation coefficient of 0.64 (P < .05). CONCLUSION: These initial results suggest that this new imaging technique may have great potential in imaging the heterogeneous vascular distribution of larger breast cancers in vivo and in monitoring treatment-related changes in angiogenesis during chemotherapy.

Salicylic Acid-Dependent Expression of Host Genes in Compatible Arabidopsis-Virus Interactions

Plant viruses elicit the expression of common sets of genes in susceptible hosts. Studies in Arabidopsis (Arabidopsis thaliana) and tomato (Lycopersicon esculentum) indicate that at least one-third of the genes induced in common by viruses have been previously associated with plant defense and stress responses. The genetic and molecular requirements for the induction of these stress and defense-related genes during compatible host-virus interactions were investigated with a panel of Arabidopsis mutant and transgenic plants defective in one or more defense signaling pathways. pad4, eds5, NahG, npr1, jar1, ein2, sid2, eds1, and wild-type Columbia-0 and Wassilewskija-2 plants were infected with two different viruses, cucumber mosaic virus and oilseed rape mosaic virus. Gene expression was assayed by a high-throughput fiber-optic bead array consisting of 388 genes and by RNA gel blots. These analyses demonstrated that, in compatible host-virus interactions, the expression of the majority of defense-related genes is induced by a salicylic acid-dependent, NPR1-independent signaling pathway with a few notable exceptions that did require NPR1. Interestingly, none of the mutant or transgenic plants showed enhanced susceptibility to either cucumber mosaic virus or oilseed rape mosaic virus based on both symptoms and virus accumulation. This observation is in contrast to the enhanced disease susceptibility phenotypes that these mutations or transgenes confer to some bacterial and fungal pathogens. These experimental results suggest that expression of many defense-related genes in compatible host plants might share components of signaling pathways involved in incompatible host-pathogen interactions, but their increased expression has no negative effect on viral infection.

Performance comparison of parallel optical interconnects for enterprise servers

There is an emerging need in the computing industry for higher bandwidth, longer distance, and increased density interconnections within clusters of high performance enterprise-class computer systems. Many of these servers share a common set of high level requirements which lend themselves to the use of parallel optical interconnects to either supplement or replace existing copper data buses. In this paper, we describe the results of application testing performed on 12-fiber parallel optical cables and connectors, including a relative comparison between three different multimode cable assembly sources. Assembly loss and effects of both axial and off-axis pull forces are measured for cable samples mated to a laser transmitter array. Significant variations exist in the performance of the same type of cable assembly from different manufacturing sources, particularly concerning their susceptibility to pull forces; we also investigate the effects of fiber strain relief to improve performance of these links. While currently available 12-fiber array connectors are not equivalent in performance to standard duplex connectors, this work suggests areas for future improvement and data communication application requirements which should be considered when using parallel fiber optic arrays.

Using a fiber-optic seismic array for well monitoring

At the end of 2002, permanent fiber-optic sensors were first used to carry out seismic recordings on the Izaute gas storage field. This successful experiment illustrates the potential applications of this technology; these include measurement of pressure, constraints, temperature, and seismic that can be used in such applications as microseismic monitoring and multiphase metering.

A shear and plantar pressure sensor based on fiber-optic bend loss

Lower-limb complications associated with diabetes include the development of plantar ulcers that can lead to infection and subsequent amputation. While we know from force-plate analyses that medial/lateral and anterior/posterior shear components of ground-reaction forces exist, little is known about the actual distribution of these stresses during daily activities or about the role that shear stresses play in causing plantar ulceration. Furthermore, one critical reason why these data have not been obtained previously is the lack of a validated, widely used, commercially available shear sensor, partly because of the various technical issues associated with measuring shear. In this study, we present a novel means of transducing plantar pressure and shear stress with a fiber-optic sensor. The pressure/shear sensor consists of an array of optical fibers lying in perpendicular rows and columns separated by elastomeric pads. We constructed a map of normal and shear stresses based on observed macrobending through the intensity attenuation from the physical deformation of two adjacent perpendicular fibers. Initial results show that this sensor exhibits low noise and responds to applied normal and shear loads with good repeatability.

Array-Based Binary Analysis for Bacterial Typing

An allele-specific oligonucleotide microarray was developed for rapid typing of pathogens based on analysis of genomic variations. Using a panel of Escherichia coli strains as a model system, selected loci were sequenced to uncover differences, such as single- or multiple-nucleotide polymorphisms as well as insertion/deletions (indels). While typical genomic profiling experiments employ specific sequences targeted to genomic DNA unique to a single strain or virulent gene, the present array is designed to type bacteria based on a patterned signature response across multiple loci. In the signature concept, all strains are interrogated by hybridizing their amplified DNA to an array containing multiple probe sequences. Allele-specific oligonucleotide probe sequences targeting each of these variable regions were synthesized and included in a custom fiber-optic array. For each locus, a set of specific probe sequences is selected, such that hybridization gives a binary signal/no signal response to each of the probes. Using this strategy for multiple loci, many pathogens or microorganisms could be classified using a limited number of probes. Because of the advantages of the fiber-optic array platform over other array formats, including sensitivity and speed, the platform described in this paper is capable of supporting a high-throughput diagnostic strategy.

A rare-cell detector for cancer.

Although a reliable method for detection of cancer cells in blood would be an important tool for diagnosis and monitoring of solid tumors in early stages, current technologies cannot reliably detect the extremely low concentrations of these rare cells. The preferred method of detection, automated digital microscopy (ADM), is too slow to scan the large substrate areas. Here we report an approach that uses fiber-optic array scanning technology (FAST), which applies laser-printing techniques to the rare-cell detection problem. With FAST cytometry, laser-printing optics are used to excite 300,000 cells per sec, and emission is collected in an extremely wide field of view, enabling a 500-fold speed-up over ADM with comparable sensitivity and superior specificity. The combination of FAST enrichment and ADM imaging has the performance required for reliable detection of early-stage cancer in blood.

Acoustic performance of a large-aperture, seabed, fiber-optic hydrophone array

A large-aperture, seabed mounted, fiber-optic hydrophone array has been constructed and characterized. The system is designed for use as a large area surveillance array for deployment in shallow water regions. The underwater portion comprises two arrays of 48 hydrophones separated by a 3 km fiber-optic link, which are connected to a shore station by 40 km of single-mode optical fiber. The hydrophone is based on a fiber-optic Michelson interferometer and the acoustic transduction mechanism is a fiber-wrapped mandrel design. No electrical power is required in the underwater portion. The performance of the system is described, characterized during laboratory measurements and during a recent sea trial. Specifically, measurements of the acoustic resolution, array shape, beam patterns, array gain, and target tracking capability of this array. The system demonstrates self-noise levels up to 20 dB (typically 10 dB) lower than the ambient acoustic noise experienced in the sea trial and array gains close to the theoretical maximum. The system telemetry and electronics have been designed to be expandable to accommodate several hundred hydrophones.

High-speed Si resonant cavity enhanced photodetectors and arrays

Over the past decade a new family of optoelectronic devices has emerged whose performance is enhanced by placing the active device structure inside a Fabry–Perot resonant microcavity [P. E. Green, IEEE Spectrum 13 (2002)]. The increased optical field allows photodetectors to be made thinner and therefore faster, while simultaneously increasing the quantum efficiency at the resonant wavelengths. We have demonstrated a variety of resonant cavity enhanced (RCE) photodetectors in compound semiconductors [B. Yang, J. D. Schaub, S. M. Csutak, D. J. Rogers, and J. C. Campbell, IEEE Photonics Technol. Lett. 15, 745 (2003)] and Si [M. K. Emsley, O. I. Dosunmu, and M. S. Ünlü, IEEE J. Selected Topics Quantum Electron. 8, 948 (2002)], operating at optical communication wavelengths ranging from 850 nm to 1550 nm. The focus of this article is on Si photodetectors and arrays. High bandwidth short distance communications standards are being developed based on parallel optical interconnect fiber arrays to meet the needs of increasing data rates of interchip communication in modern computer architecture. To ensure that this standard becomes an attractive option for computer systems, low cost components must be implemented on both the transmitting and receiving end of the fibers. To meet this low cost requirement silicon based receiver circuits are the most viable option, however, high speed, high efficiency silicon photodetectors present a technical challenge. Commercially reproducible silicon wafers with a high reflectance buried distributed Bragg reflector (DBR) have been designed and fabricated [M. K. Emsley, O. I. Dosunmu, and M. S. Ünlü, IEEE J. Selected Topics Quantum Electron. 8, 948 (2002)]. The substrates consist of a two-period, 90% reflecting, DBR fabricated using a double silicon-on-insulator (SOI) process. Resonant-cavity-enhanced (RCE) Si photodetectors have been fabricated with 40% quantum efficiency at 850 nm and a FWHM of 29 ps suitable for 10 Gbps data communications. Recently, 1×12 photodetector arrays have been fabricated, packaged, and tested with silicon based amplifiers to demonstrate the feasibility of a low cost solution for optical interconnects.

Fiber optic sensor arrays: a new method to improve multiplexing capability with a low complexity approach

In this paper, we show some preliminary numerical results in order to increase the multiplexing capability of a multipoint fiber Bragg grating (FBG) sensor network without increase the system complexity. We base the new approach on the possibility of exploiting the chirped-pulsed frequency modulation technique (C-PFM). This technique, extensively used in radar applications, is based on the amplitude modulation of the emitted signal (pulsed) by a chirped frequency signal and on the demodulation of the reflected signal by means of adaptive filter. FBG sensors are instrumental to obtain cheap and easy handling multipoint sensing arrays.

Fibre-optic array for curvature assessment: application in otitis diagnosis.

A contact-free sensor consisting of two parallel optical-fibre arrays was designed to assess surface shapes of diffusely scattering media. By sequentially illuminating objects using one fibre array and detecting the diffusely back-scattered photons by the other, a source-detector intensity matrix was formed, where the matrix element (i, j) was the intensity at detector j when light source i was excited. Experimental data from convex and concave polyacetal plastic surfaces were recorded. A mathematical model was used for simulating source-detector intensity matrices for the surfaces analysed in the experiments. Experimental results from the system were compared with the theoretically expected results provided by the mathematical model. The shape and relative amplitude showed similar behaviour in the experiments and simulations. A convex/concave discriminator index D, representing the detected intensity difference between two source-detector separations, was defined. The relative dynamic range of D, defined as the difference between the maximum and the minimum divided by the mean of the index, was 1.37 for convex surfaces and 0.68 for concave surfaces, at a measuring distance of 4.5 mm. The index D was positive for convex surfaces and negative for concave surfaces, which showed that the system could distinguish between convex and concave surfaces, an important result for the diagnosis of otitis media.

A Transillumination CT Imaging System in Near-Infrared Regions with Optical Fiber Arrays

A Transillumination CT Imaging System in Near-Infrared Regions with Optical Fiber Arrays

Optical switch with auto-aligning fibers and latching micro-mirrors

This paper presents an innovative device for self-aligning in a V-groove and a self-latching vertical mirror on the suspension diaphragm using the out of plane fiber-optical switch array technique. The self-aligning offers integrating the optical fiber and mirror within the same optical switch. The self-latching vertical mirror is supported on the suspension diaphragm by four cantilever beams. The theoretical analysis includes a dynamic simulation using the ANSYS software and corner compensation using the IntelliCAD software. The fabrication process consists of wet etching micromachining, lithography, and excimer laser ablation. This proposed process is simpler than those proposed in other works. An electrostatic driving voltage is used to operate the optical switch. The mirror is made of a photoresist coating with gold film as the switching element. The reflectivity of the gold film mirror is higher than 85% using a wavelength of 1310 nm. The micro-optical switch has a maximum displacement of 48 μm and the switching time is below 0.4 ms with a driving voltage of 100 VDC.

Measurement of Friction Coefficient for Automatic Assemble of Optical Fiber Array

Measurement of Friction Coefficient for Automatic Assemble of Optical Fiber Array

Encoded fiber-optic microsphere arrays for probing protein-carbohydrate interactions.

Carbohydrate-binding proteins and their glycoconjugate ligands play significant roles in a number of critical biological processes. Immune response, viral membrane fusion, glycoprotein homeostasis, and signaling all involve carbohydratebinding protein mediation at key steps. A more detailed understanding of the exact nature of carbohydrate–protein interactions is expected to render them attractive therapeutic targets. To facilitate these biochemical investigations, glycobiologists require tools that will enable the simultaneous identification of carbohydrate-binding proteins and the oligosaccharide structures they bind. Carbohydrate microarrays were introduced as a promising tool to aid in the discovery of oligosaccharide moieties necessary for carbohydrate-binding protein recognition. Microarrays require small quantities of material, enable simultaneous screening of a defined set of structures against a host of potential binding partners, and, in some cases, are fully amenable to present high-throughput screening technologies, such as robotic printing and fluorescence scanning devices. In the past year, several systems were described that present both natural and synthetically derived carbohydrate structures in array formats. These systems differ in the mode of immobilization (covalent versus noncovalent), the surface upon which the immobilization was performed, and the

Large-scale remotely pumped and interrogated fiber-optic interferometric sensor array

We report a demonstration of a large-scale remotely interrogated remotely pumped fiber-optic, interferometric sensor array. The system is designed primarily for underwater acoustic applications where each sensor is configured as a hydrophone and a large number of sensors (i.e., up to /spl sim/500) are required to be interrogated through link lengths of several tens of kilometers. A system comprising of 96 sensors combined using time and dense wavelength-division multiplexing and interrogated through a 40-km fiber link is demonstrated. A remotely pumped erbium-doped fiber amplifier is incorporated into the array to increase the distance between the array and interrogation electronics. We describe the performance of our system and validate a previously published model.