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We have developed a real-time sleep apnea monitoring system called “Apnea MedAssist II”. This has three independent sensors: ECG, SpO2 and Breath sensor. These sensors are connected to a smartphone via Bluetooth. The signal processing of the sensor signals and automated classification of a sleep epoch as an apnea event or a non-apnea event are done in a smart phone. The soft ware for signal processing and automated classification can be imported to an Android OS based smart phones as an `app' that we have developed. The system has accuracy well over 97% when tested on Physionet database. The system is being readied for limited patient trial.

An interpolation algorithm technique to automatically lock the wavelength of semiconductor laser systems by balancing the temperature and bias current of the laser is demonstrated. The wavelength accuracy is +20 pm in the bias current range of 30-120 mA for typical distributed feedback lasers and electroabsorption modulated lasers. This method is software based and does not require any optical or electrical wavelength locking circuitry.

We have formulated a matrix eigenvalue problem for cylindrical optical fibers from a set of finite difference equations. Numerical solution of this problem yields the propagation constants for propagating modes. The method can be used for arbitrary index profiles, does not require the explicit evaluation of Bessel or modified Bessel functions, and does not use iterative methods to search for the propagation constants as was the case in earlier proposed methods using finite differences. The method is accurate, fast, and simple. We have established the convergence and stability of this method, and explored the effects of finite cladding width on the dispersion characteristics.

We have developed a set of computer codes that compute the propagation constants and field patterns for the propagating modes of cylindrical optical fibers. From a simple set of finite difference equations, solutions of the scalar Helmholtz wave-equation may be computed across a range of normalized frequencies to generate curves describing the dispersion characteristics of the fiber. Accurate cutoff frequencies for any mode can also be computed. We designed the computer codes around α-index profiles since these profiles have been extensively covered in the literature, but our system also supports arbitrary profiles within the limits of the "small index gradient" and "weakly guiding" approximations. The computer codes are accurate and fast. They may be used interactively to explore dispersion in optical fibers and the effects of finite cladding width on dispersion.

A guided wave optical interconnect has been designed which reduces or eliminates clock skew by ensuring simultaneous delivery of clock pulses to chips mounted on a wafer. The interconnect consists of a multimode trunk waveguide and a set of branch waveguides, one per chip, each of which couples one mode out of the trunk waveguide. The elimination of clock skew is accomplished by taking advantage of the different group velocities of the modes inherent in multimode waveguides and suitably tailoring the propagation constants of the trunk waveguide according to the location of the respective chip on the wafer. Inverse scattering theory, specifically, the method of Darboux transformations, is used to design the refractive index profiles of the trunk waveguides, using the set of propagation constants selected during the first stage of the design as input data. It is shown that, by using transverse coupling and suitable design of the trunk and branch waveguides, efficient coupling from the trunk to the branch waveguides can be ensured. Techniques for ensuring a symmetric trunk refractive index profile are investigated. >

A simple numerical method based on finite differences to solve the scalar wave equation encountered in optical fibers is presented. The method uses the Ricatti transformation to the scalar wave equation and is capable of analyzing fibers of arbitrary refractive index profiles. Achieving errors as low as 0.005% for propagation constants is possible for lower-order modes. However, the error seems to increase for frequencies closer to cutoff.

An explicit central difference scheme to implement the beam-propagation algorithm for analyzing pulse propagation in photonic integrated circuits is discussed. The method has been successfully applied to planar waveguides, channel waveguides, and waveguide couplers. The method shows stability even after long propagation distances and does not involve computation of fast Fourier transform at any step, contrary to the methods discussed earlier. © 1992 John Wiley & Sons, Inc.

An inverse scattering theory is used to design an optical binary switch. The binary output states of the switch are modelled as phase conjugate reflection coefficients relating to two different refractive index profiles in a waveguiding structure. Proper spatial intensity filtering of the input laser radiation in conjuction with the nonlinearity of the waveguide material can lead to switching in a thin-film waveguide.

Application of inverse scattering theory at fixed angular momentum for designing circular optical waveguides possessing prescribed propagation constants β for a fixed azimuthal mode number is well known. However, waveguides designed using such a method, in general, will not be able to transmit other azimuthal modes without being dephased. In order to overcome this problem, the inverse scattering procedure at fixed energy is modified and applied to this design problem. It is shown that when gradient of the refractive index is negligible the method can be used to design waveguides with the same propagation constant for different azimuthal modes. This allows the modes to propagate through the waveguide without dephasing.

In this letter we consider burst switching for very high speed routing in the next generation Internet backbone. In this scenario, Internet protocol (IP) packets to a given destination are collected in bursts at the network edges. We propose a burst assembly mechanism that can reduce the traffic autocorrelation or degree of self-similarity, and at the same time keep the delay due to burst formation limited at the network edges.

The probability density function of the mode partition noise of a nearly single-mode cw laser is discussed. Nearly single-mode lasers are modeled here as those with a single dominant mode and 2 n side modes with nonnegligible strengths. The drop out rate of each side mode obeys an exponential distribution. The combined probability density function of the drop out rate for 2 n side modes is derived here. This density is evaluated when side modes with various intensities are present.

The authors review electromagnetic inverse scattering theory for inhomogeneous dielectric waveguides and devices. Typically the parameters of these system components are expressed as functions of frequency or wavenumber, so that spectral, i.e. time-harmonic, methods are appropriate. Spectral, i.e. time-harmonic, inverse scattering theory is reviewed using the propagation of electromagnetic waves in inhomogeneous dielectric waveguides as a physical model. Permittivity profiles are reconstructed from scattering matrix data. Applications to the design of couplers, logical gates, and nonuniform transmission lines are discussed. >

A 4/spl times/4 cross-connect and a 1/spl times/8 power splitter based on self-imaging waveguides are analyzed using the beam propagation method. The cross-talk levels in the cross-connect and power levels at the output of the power splitter are calculated.

We demonstrate that optimum switch performance can be achieved by matching the basic delay line unit in the optical buffer to the degree of self-similarity of the input traffic, in tandem with a scheduling algorithm for void filling.

This paper describes the application of commercial-off-the-shelf (COTS) fiber optic technology to support an antenna remoting infrastructure for high density, multi-channel wireless communications. The approach uses fiber optic supertrunking of multiple RF channels. It employs Er-doped fiber amplifiers (EDFAs) to provide extended range capabilities (20 km to 50 km) with analog signals without the use of electronic repeaters. We describe a design approach that facilitates radio frequency (RF) spectrum management and improves range operations with a smaller compliment of antennas. The objective is to affect cost reductions through system improvements related to the quantity of antennas, placement of antennas, maintenance of equipment and management of the RF spectrum. The discussion includes analysis and results of the constraints on the optimum operating condition with a balance between distortion, thermal noise, optical intensity noise, spontaneous intensity noise and the optical receiver sensitivity. The goals include reduction in costs and the mitigation of collocation and interference problems.

Advances in fiber optic technologies provide the capabilities to employ remote antenna links that improve the performance of RF communications systems in tactical and training scenarios. Such links support improved system flexibility, reduced radio frequency interference and improved personnel protection from anti-radiation ordnance. We discuss the application of commercial off-the-shelf (COTS) wavelength division multiplexing (WDM) and erbium doped fiber amplifier (EDFA) technologies to approaches for expansion of the transmission capacity of existing fiber optic links used for antenna remoting of RF channels. In a previous paper by Cleveland and Tamil (see MILCOM'96, IEEE Military Commun. Conf., p.42-46, 1996), they described the link performance achieved with an EDFA repeater for remoting of a supertrunk for SINCGARS SIP transceiver signals from the Operations Center at the National Training Center to remote antennas. This paper expands the performance analysis to include the addition of optical wavelength division multiplexing (WDM) for the transport of multiple RF supertrunks on a single fiber. The added supertrunk services could include EPLRS, video and cellular telephony links. Our discussion includes an analysis of the constraints imposed by EDFA and WDM components on the optimum link operating condition. We consider the balance between distortion, crosstalk, thermal noise, optical intensity noise, spontaneous emission-signal beat noise and the optical receiver sensitivity. We discuss these factors in terms of the limitations to the link dynamic range and the maximum signal-to-noise ratio.

Multiband operation of planar and phased array antennas is becoming increasingly important in both military and commercial communications due to the need for flexibility in meeting a number of operational SATCOM requirements. With today's technology, multiband operation requires changing antenna feed components and so hinders rapid changeover to different operating frequency bands. Planar antenna size and weight may be reduced by employing optical feed design concepts (i.e. optical generation and control) in the development of a wideband phased array communication system architecture. The resulting antenna system can be rapidly reconfigured to operate on any of several bands, and has mechanical stability advantages.

Electromagnetic inverse scattering theory is used to model the ON and OFF states of an all‐optical logic gate. The scattering data are two phase‐conjugate reflection coefficients that were obtained by pole reflection.

Interest in the deployment of Wavelength Division Multiplexing (WDM) in regional and metropolitan networks has increased recently. We consider an example of regional/metropolitan rings and investigate the interaction of node-induced crosstalk with fiber nonlinearities in it. The phenomenon is studied in two cases, namely the case of Non-Zero Dispersion Shifted Fiber (NZDSF) operating in the anomalous dispersion regime and the case of Single Mode Fiber (SMF) with uniformly distributed segments of Dispersion Compensating Fiber (DCF). The dependence of the effect of the crosstalk/nonlinear interaction on the frequency difference between signal and crosstalk carriers and on signal power is examined in detail. It is shown that the node-induced crosstalk can interact with fiber nonlinearities and introduce limitations on transmission performance. This interaction should therefore be taken into consideration in designing regional and metropolitan networks.

The first part of this paper presents a method for designing guided wave optical interconnects with reduced clock skew, applicable in a chip-to-chip or intra chip situation. The interconnect consists of a multimode trunk waveguide and a set of single mode branch waveguides each of which couples one mode out of the trunk waveguide (see Fig.1). The graded-index guided wave interconnects can effectively reduce clock skew by suitable design of the refractive index profiles [1],[2]. This design is accomplished by properly tailoring the propagation constants of the guided modes to provide equal propagation times to a set of detectors. The scheme presented in this paper employs several optical channels, each having a different refractive index profile. This includes a main multimode channel and several single-mode waveguides coupled to the main line. Total system design takes into account the problem of clock skew as well as efficient coupling between the trunk and branch waveguides. An inverse scattering technique that provides the design parameters of an optoelectronic guided-wave structure from the prescribed transmission characteristics has been used to design the interconnect. This technique is contrary to the traditional techniques which require iterative adjustments of the design parameters to achieve the required transmission characteristics.

Optical solitons propagating in media exhibiting saturable nonlinearity offer advantages over Kerr-medium solitons for transmission over large distances through optical fibers with loss. Soliton pulses in saturable media offer greater energy for a given peak power, and upper-branch solitons decrease in width with distance traveled. These properties result in pulses that remain distinct and detectable for greater distances than Kerr-medium solitons do with the same peak power.