The influence of nonfundamental pump modes in erbium-doped fiber amplifiers

This work analyzes how the characteristics of an erbium-doped fiber amplifier (EDFA) depends on the mode distribution of 800-nm pump light. The analysis is performed by using a large-signal model of an optimally pumped erbium-doped fiber amplifier. Special attention is given to the gain degradation, and noise figures of the amplifier for co- and counterpropagating pump light.     

Lattices in the Pseudoeuclidean Plane

Because of the metric structure of the pseudoeuclidean plane, lattices have some remarkable features, e.g., concerning their symmetry groups and concerning isotropic, space- and time-like elements. Especially (p,q,s)-lattices, which are characterized by the fact that their symmetry groups contain hyperbolic rotations, are showing some interesting structures and substructures.     

Enantioselective synthesis of 3-demethoxyaranciamycinone via asymmetric epoxidation

The tetracyclic olefin 1 was enantioselectively epoxidized using a molybdenum(VI)- oxodiperoxo complex containing a chiral lactamide. Conversion to the glycosides 8 and 9 showed the epoxide 2 to be the predominant (3 : 1) enantiomer.     

Sub-Stonean spaces and corona sets

A self-contained account of the theory of sub-Stonean spaces, and their relations to Stonean spaces and Rickart spaces is given. Of particular interest are the corona sets (of the form β(X) for locally compact, σ-compact spaces, because these highly nontrivial sub-Stonean spaces lend themselves to C?ech-cohomological considerations. The theory of sub-Stonean spaces is essential for our solution of the diagonalization problem for C(X)? M_n, found in K. Grove and G. K. Pedersen, Diagonalizing matrices over C(X), submitted for publication.     

Injective choice functions for countable families

This paper proves a necessary and sufficient condition for an arbitrary countable family of sets to have an injective choice function. Some applications are indicated.     

Performance improvement of direct detection systems using local and/or long-distance pumped fiber amplifiers

Erbium-doped fiber amplifiers (EDFAs) in eight different system configurations are investigated, using a full-scale model, and the midline placement of the amplifier is shown to be optimal. A distributed amplifier compared to the remote pumping scheme shows no system improvement. Use of a booster (next to the transmitter), a midline remote-pumped amplifier, and a preamplifier (next to the receiver) allows up to 180 km of extra transmission fiber to be added.