Mani Mina

On trading wavelengths with fibers: a cost-performance based study

We consider the effect of multiple fibers on wavelength division multiplexing networks without wavelength conversion. We study networks with dynamic wavelength routing and develop accurate analytical models to compare various possible options using single- and multiple-fiber networks. We use results of an analytical model and simulation-based studies to evaluate the blocking performance and cost of multifiber networks. The number of fibers required providing high performance in multifiber networks and their costs are compared. A case is made for using multiple fibers in each link with fewer wavelengths instead of using a single fiber with many wavelengths. In particular, we show that a network with four fibers per link and with four wavelengths on each fiber without any wavelength conversion on any node yields similar same performance as the networks with one fiber per link and 16 wavelengths per fiber on each link and with full wavelength conversion capability on all nodes. In addition, the multifiber network may also offer the cost advantage depending on the relative cost of components. We develop a parametric cost model to show that multiple fibers in each link are an attractive option. Finally, such multifiber networks also has fault tolerance, with respect to a single fiber failure, already built into the system.

Light-trail testbed for IP-centric applications

The Internet transport infrastructure is evolving toward a model of high-speed routers interconnected by intelligent optical networks. In this article we review current optical networking architectures and describe a new concept proposed in A. Gumaste and I. Chlamtac [2003]: light-trails. We develop light-trails as a novel and amenable control and management solution to address IP-centric communication problems at the optical layer. We implement a testbed to demonstrate light-trail feasibility. We also present three medium access control protocols for light-trails and evaluate their performance. The goal of light-trails and our solution is to combine commercially available components with emerging network technologies to provide a transparent, reliable, and highly scalable communication network.

Source of low-frequency fluctuations in functional MRI signal

To investigate the source of native low‐frequency fluctuations (LFF) in functional MRI (fMRI) signal.

Short Paper: A Signal Fingerprinting Paradigm for General Physical Layer and Sensor Network Security and Assurance

In this paper, we present a new paradigm for security in conventional networks that has dramatic implications for improving their physical layer network security. We call this paradigm, Detecting Intrusions at Layer ONe (DILON). DILON’s enabling hypothesis is that the inherent variability in the construction of digital devices leads to significant variability in their analog signaling. This is true not only for different device models but even for nearly identical devices of the same manufacturing lot. The idea is that by oversampling digital signals to make analog measurements that constitute “voiceprints” of network devices. These form a profile that can be used for detecting MAC address spoofing, reconfiguration of network topologies, and in the long term possibly predict the failure of network devices. This paper discusses historic references and how digital networks enable new approaches as well as a number of applications.

Physical-Layer Identification of Wired Ethernet Devices

This work sets forth a systematic approach for the investigation and utilization of the signal characteristics of digital devices for use in a security context. A methodology, built upon an optimal detector, the matched filter, is proposed that allows for the reliable identification and tracking of wired Ethernet cards by use of their hardware signaling characteristics. The matched filter is found to be sensitive enough to differentiate between devices using only a single Ethernet frame; an adaptive thresholding strategy employing prediction intervals is used to cope with the stochastic nature of the signals. To demonstrate the validity of the methodology, and to determine which portions of the signal are useful for identification purposes, experiments were performed on three different models of 10/100 Ethernet cards, totaling 27 devices in all. In selecting the cards, an effort was made to maximize intramodel similarity and thus present a worst-case scenario. While the primary focus of the work is network-based authentication, forensic applications are also considered. By using data collected from the same devices at different times, it is shown that some models of cards can be reidentified even after a month has elapsed since they were last seen.

Mach–Zehnder Interferometric Switch Utilizing Faraday Rotation

An all-fiber interferometric switch based on Faraday rotation exhibited by magneto-optic materials in the presence of an external magnetic field is reported. The interferometer is Mach-Zehnder type and the related phase shift was obtained by the rotation of the state of polarization of a linearly polarized optical signal. The operation of the switch is demonstrated experimentally. The effect of the optical beam size on the achievable Faraday rotation is also investigated. Hysteresis is avoided as the magnetic field required for switching is much lower than the saturation field

Neural Network Approaches to Data Fusion

The challenge of meeting the increasingly sophisticated industrial inspection needs has led to the development of a number of nondestructive evaluation (NDE) methodologies. NDE techniques rely largely on the interaction of some form of energy and the test specimen to provide information relating to the condition of the material. The choice of energy utilized in the inspection process is dictated by the type of material under inspection as well as by the nature and location of the flaw. A variety of energy sources have been employed to interrogate materials. These include acoustic, electromagnetic, optical and x-ray energy sources [1]. Each of these methods brings its own set of advantages and disadvantages and often no single technique offers a full solution to the inspection problem. As an example, ultrasonic imaging techniques offer excellent resolution and sensitivity to both surface breaking as well as subsurface cracks. However, the method is also sensitive to a wide variety of measurement conditions including surface roughness and coupling. In contrast, eddy current techniques do not require contact with the test specimen and are relatively insensitive to surface roughness conditions. The disadvantages associated with the eddy current method lies its insensitivity to defects that lie in the recesses of the material, its poor resolution capabilities, and its sensitivity to variations in liftoff. The energy / material interaction process is also fundamentally different in the two cases. Unlike the ultrasonic method which relies on wave propagation of energy, the eddy current process is essentially diffusive in nature. It can therefore be argued that one could profit from integrating information obtained from the two tests. The challenge lies in isolating components of information that are either complementary or redundant. The complementary segments of information can be utilized to improve the quality of characterization while at the same time using redundant information to improve the signal-to-noise ratio(SNR).

Current-Controlled, High-Speed Magneto-Optic Switching

In this paper, an optical switch utilizing a magneto-optic Faraday rotator (MOFR) capable of submicrosecond switching is presented. The optical circuit and supporting electronic circuitry are presented. High optical switching speeds are accomplished through the design of an electronic circuit capable of creating high-speed magnetic pulses. Rise times of 75 ns of 40-Oe magnetic fields are achieved for optical circuit control. Experimental results of the electrical and optical circuit are presented. Circuit design and practical considerations are discussed.

Fiber-Based Magneto-Optic Sagnac Optical Modulator

In this paper, a fiber-based, magneto-optic (MO) optical modulator based on Sagnac interferometry is proposed. The system uses a Faraday rotator to produce optical modulation with low magnetic fields. The Sagnac geometry allows for increased modulation at lower fields than traditional MO modulators. A formulation of the system is provided using Jones calculus. Experimental results at 1550 nm using single mode fiber are reported, including a discussion of dynamic range and effect of magnetic field strength. Theoretical and practical advantages and limitations are discussed. Methods for improving modulation speed, dynamic range, and performance are presented.

Field Coil for Magneto-Optic Switching: Capacitance Considerations

A tractable method for accurately predicting the parasitic capacitance of a field coil as part of an all-fiber Mach-Zehnder interferometric switch based on Faraday rotation is reported. The effects of the wire insulation layer, inter-turn air gap as well as capacitive coupling to the four nearest adjacent turns are considered in predicting the effective parasitic capacitance for single-layer coils. The complex distributed capacitance network that results is resolved using Kron reduction to yield the equivalent shunt capacitance. Several coil configurations were designed and compared to experimental results. This new approach can be used in conjunction with existing expressions for inductance and loss to enable the complete and accurate a priori design of field generating coils.