Synthesis of C(3) benzofuran-derived bisaryl quaternary centers: approaches to diazonamide A.

[reaction: see text] Two complementary strategies for the synthesis of the diazonamide A bisaryl quaternary center are described. The first strategy relies upon an extremely facile tandem cyclopropanation/ring-opening sequence, which has proven amenable to chiral catalysis to provide enantioenriched material. The second strategy relies upon a more concise alkylation route ideal for material advancement.

Influence of mode coupling on differential mode delay.

The manner in which the differential mode delay (DMD) pulse response is affected by ellipticity- and microbending-induced mode coupling has been analyzed numerically. We have considered both a fiber profile containing a central index dip and fiber profiles with sinusoidal ripples. We find that slowly varying profile components can be correctly estimated from DMD results even in the presence of substantial mode coupling.

Effect of mode coupling on the total pulse response of perturbed optical fibers.

A computer program has been developed to study the total pulse response of optical fibers with profile ripple and central index depressions in the presence of arbitrary mode coupling. We have found that the magnitude of the compression of the total pulse response generated by mode coupling depends significantly on the details of the refractive-index profile of the test fiber.

Calculated pulse responses of perturbed fiber profiles.

The effects of a central index dip and profile ripple on the total pulse width of a near-optimum optical fiber are analyzed. A comparison of our results, which are based on numerical integration of the scalar wave equation, with the results of the WKB method demonstrates that the WKB theory cannot be applied to rapidly varying refractive-index profile perturbations. Subsequently, we investigate the change in the pulse width resulting from strong mode coupling within each of the fiber's mode groups.