A 1.55-μm solid-state laser source for DWDM applications

We describe the design and operation of a 1550-nm diode pumped Er,Yb:glass laser with >130 mW of output power and a free running linewidth of ~22 kHz. Due to the low frequency relaxation oscillation, near shot limited relative intensity noise performance is obtained throughout the radio frequency (RF) range of interest for cable television and dense wavelength division multiplexed (CATV/DWDM) applications. For long-haul spans an intracavity lithium niobate phase modulator allows for chirping of the linewidth to bandwidths and at rates sufficient to defeat stimulated Brillouin scattering (SBS). For certain applications, the high output power can eliminate the need for an erbium-doped fiber amplifier (EDFA)     

Phase noise characterization of SAW oscillators based on a Newtonminimization procedure

An iterative minimization technique is used to optimize the values of circuit and device parameters which determine the phase noise response of a voltage-controlled SAW-stabilized oscillator (VCSO). An expression-developed by T.E. Parker (1985) is used to calculate the double-sideband phase noise to carrier ratio from circuit parameter values; good agreement between calculations and phase noise measurements is achieved by minimizing the squared error through the use of a steepest-descent/Newton-Raphson minimization scheme. Less accurately known circuit parameters are thus optimized in an iterative fashion. Exact expressions for the elements of the Hessian Matrix are used in the Newton-Raphson procedure, allowing for fast computations. The numerical findings suggest that useful results can be obtained in the determination of VCSO circuit parameters     

On the determination of the terminal impedances of a nonuniform transmission line

The problem of determining the terminal impedance values of a lossless nonuniform transmission line is addressed. The transmission line is assumed to have discontinuities at input and output with local reflection coefficientsGamma_{1}andGamma_{2}, respectively. A set of formulas is given which allowsGamma_{1}andGamma_{2}to be recovered once high-frequency data forS_{11}(omega) is specified; the formulas extend the generality of earlier theory to the case whereGamma_{1}orGamma_{2}may be either positive or negative. It is also shown thatS_{11} (omega)) magnitude and phase information is necessary to uniquely determineGamma_{1}andGamma_{2}.     

Synthesis of nonuniform transmission lines with terminaldiscontinuities

An integral equation was previously derived by the authors (ibid., vol.AP-34, p.546-53, Apr. 1986) for the inverse problem associated with finite-length nonuniform lines having known impedance discontinuities at the input and output. A procedure for determining the characteristic impedance profile of the line from the solution of the integral equation was also presented. Here, the numerical aspects of this inverse problem are treated. This equation is solved using general expansions of both the kernel and unknown functions, thereby reducing the integral equation to a system of linear algebraic equations. This makes possible a numerical implementation of the theory by which the impedance profile of a nonuniform line may be reconstructed from given spectral data. The realizability aspects of the problem are treated and several examples of computer-assisted profile inversion are presented     

Design and implementation of dynamic near-infrared optical tomographic imaging instrumentation for simultaneous dual-breast measurements

Dynamic near-infrared optical tomographic measurement instrumentation capable of simultaneous bilateral breast imaging, having a capability of four source wavelengths and 32 source-detector fibers for each breast, is described. The system records dynamic optical data simultaneously from both breasts, while verifying proper optical fiber contact with the tissue through implementation of automatic schemes for evaluating data integrity. Factors influencing system complexity and performance are discussed, and experimental measurements are provided to demonstrate the repeatability of the instrumentation. Considerations in experimental design are presented, as well as techniques for avoiding undesirable measurement artifacts, given the high sensitivity and dynamic range (1:10(9)) of the system. We present exemplary clinical results comparing the measured physiologic response of a healthy individual and of a subject with breast cancer to a Valsalva maneuver.