Direct search methods are best known as unconstrained optimization techniques that do not explicitly use derivatives. Direct search methods were formally proposed and widely applied in the 1960s but fell out of favor with the mathematical optimization community by the early 1970s because they lacked coherent mathematical analysis. Nonetheless, users remained loyal to these methods, most of which were easy to program, some of which were reliable. In the past fifteen years, these methods have seen a revival due, in part, to the appearance of mathematical analysis, as well as to interest in parallel and distributed com- puting. This review begins by briefly summarizing the history of direct search methods and considering the special properties of problems for which they are well suited. Our focus then turns to a broad class of methods for which we provide a unifying framework that lends itself to a variety of convergence results. The underlying principles allow general- ization to handle bound constraints and linear constraints. We also discuss extensions to problems with nonlinear constraints.

https://www.cs.wm.edu/~va/research/sirev.pdf

Optimization by Direct Search: New Perspectives on Some Classical and Modern Methods ∗

The present invention relates to optical confinements, methods of preparing and methods of using them for analyzing molecules and/or monitoring chemical reactions. The apparatus and methods embodied in the present invention are particularly useful for high-throughput and low-cost single-molecular analysis.

Arrays of optical confinements and uses thereof

This paper reviews recent progress in broad-band Raman amplifiers for wavelength-division-multiplexed (WDM) applications. After the fundamentals of Raman amplifiers are discussed in contrast to erbium-doped fiber amplifiers, a new technique called "WDM pumping" is introduced to obtain ultrabroad and flat gain in Raman amplifiers only using WDM diode pumps. The design issues of this technique are then developed to realize outstanding performances such as 100 nm of flat gain bandwidth, 0.1 dB flatness over 80 nm, and so forth.

Ultrabroad-band Raman amplifiers pumped and gain-equalized by wavelength-division-multiplexed high-power laser diodes

Catalytic automotive exhaust aftertreatment

Aspects of the subject disclosure may include, for example, receiving, by a feed point of a dielectric antenna, electromagnetic waves from a dielectric core coupled to the feed point without an electrical return path, where at least a portion of the dielectric antenna comprises a conductive surface, directing, by the feed point, the electromagnetic waves to a proximal portion of the dielectric antenna, and radiating, via an aperture of the dielectric antenna, a wireless signal responsive to the electromagnetic waves being received at the aperture. Other embodiments are disclosed.

Method and apparatus for coupling an antenna to a device

Disclosed is a family of dispersion compensating optical fibers that are adapted for use with conventional single-mode transmission fibers that are optimized for zero dispersion operation at a wavelength in the range from 1290 nm to 1330 nm to form a transmission link suitable for low dispersion operation in the 1520-1565 nm wavelength window. The dispersion compensating fibers are capable of providing a dispersion more negative than -20 ps/nm-km and attenuation less than 1 dB/km at wavelengths in the 1520-1565 nm region. Certain of the dispersion compensating fibers also exhibit a dispersion versus wavelength relationship having a negative slope in the 1520-1565 nm region, to compensate for the dispersion versus wavelength slope of the transmission fiber. The dispersion compensating fiber can be advantageously combined with a fiber amplifier to form a compensator that is adapted to overcome attenuation introduced into the system by the dispersion compensating fiber. In one embodiment, the dispersion compensating fiber is also a distributed fiber amplifier.

Dispersion compensating devices and systems

Disclosed is a single mode optical waveguide fiber having a core refractive index profile in which the profile parameters are selected to providean attenuation minimum. A set of profiles having the same general shape and dimensions is shown to have a group of profiles contained in a sub-set which exhibit a minimum of attenuation as compared to the remaining members of the set. The members of the sub-set have been found to have the lowest effective group index, n geff, and the lowest change in .beta.2 under waveguide fiber bending.

Low attenuation optical waveguide

An compound core optical waveguide fiber designed for high data rate or single channel or WDM systems which may include optical amplifiers. The waveguide is characterized by a core having two or three regions wherein the refractive index can be varied. The relative size of the regions may also be varied. By adjusting these variables, the desired mode field diameter, zero dispersion wavelength, dispersion slope and cut off wavelength were obtained. The optical properties are chosen to limit non-linear effects while maintaining low attenuation and acceptable bend performance. In addition, the residual stress within the waveguide is maintained at a low level to limit stress induced birefringence. The low residual stress in the uncoated waveguide, together with a dual coating system having selected moduli and glass transition temperatures results in low polarization mode dispersion.

Increased capacity optical waveguide

Increasing demand has caused substantial interest in high bit rate (> 5 Gbit/s) telephony systems, as reflected in emerging use of dispersion-shifted fibers for 1550 nm transmission in new system installations. However, the upgrading of existing standard single-mode 1310 nm optimized optical fiber routes to higher capacities is also of great concern to long-haul telecommunication providers with large embedded fiber systems. Ideally, the upgrade method would provide for both increased data rates and longer span capability, so that the existing fiber could carry more data with a minimum amount of new equipment. In the 1550 nm wavelength window, erbium-doped fiber amplifiers (EDFAs) can reduce loss limitations. Unfortunately, for typical silica step-index fibers, chromatic dispersion has limited production-grade intensity modulated direct detection (IMDD) transmission systems to, for example, about 100 km between regeneration sites at 2.5 Gbit/s, resulting in a bit-rate-distance product of 250 Gbit-km/s.

All-Optical, Fiber-Based 1550 nm Dispersion Compensation in a 10 Gbit/s, 150 km Transmission Experiment over 1310 nm Optimized Fiber

A single mode optical waveguide fiber having a positive total dispersion is disclosed. The novel waveguide fiber has a core region comprising three distinct segments. Studies of this novel waveguide, wherein properties are calculated as various ones of the core region parameters are changed, show that the waveguide satisfies the requirements of a fiber in a high bit rate, long regenerator spacing system. The novel waveguide design is relatively simple to manufacture and maintains its functional properties at tight tolerances when the core region parameters are varied over a prescribed range. This high performance waveguide limits self phase modulation and four wave mixing, facilitates wavelength division multiplexing, and is compatible with optical amplifiers.

David K. Smith

Papers

Dispersion compensating devices and systems

Low attenuation optical waveguide

Increased capacity optical waveguide

All-Optical, Fiber-Based 1550 nm Dispersion Compensation in a 10 Gbit/s, 150 km Transmission Experiment over 1310 nm Optimized Fiber

Positive dispersion optical waveguide