22 research outputs found
A Novel Solution to the Dynamic Routing and Wavelength Assignment Problem in Transparent Optical Networks
We present an evolutionary programming algorithm for solving the dynamic
routing and wavelength assignment (DRWA) problem in optical wavelength-division
multiplexing (WDM) networks under wavelength continuity constraint. We assume
an ideal physical channel and therefore neglect the blocking of connection
requests due to the physical impairments. The problem formulation includes
suitable constraints that enable the algorithm to balance the load among the
individuals and thus results in a lower blocking probability and lower mean
execution time than the existing bio-inspired algorithms available in the
literature for the DRWA problems. Three types of wavelength assignment
techniques, such as First fit, Random, and Round Robin wavelength assignment
techniques have been investigated here. The ability to guarantee both low
blocking probability without any wavelength converters and small delay makes
the improved algorithm very attractive for current optical switching networks.Comment: 12 Pages, IJCNC Journal 201
Molecular beam epitaxy and defect structure of Ge (111)/epi-Gd2O3 (111) /Si (111) heterostructures
Molecular beam epitaxy of Ge (111) thin films on epitaxial-Gd2O3/Si(111)
substrates is reported, along with a systematic investigation of the evolution
of Ge growth, and structural defects in the grown epilayer. While Ge growth
begins in the Volmer-Weber growth mode, the resultant islands coalesce within
the first 10 nm of growth, beyond which a smooth two-dimensional surface
evolves. Coalescence of the initially formed islands results in formation of
rotation and reflection microtwins, which constitute a volume fraction of less
than 1 %. It is also observed that while the stacking sequence of the (111)
planes in the Ge epilayer is similar to that of the Si substrate, the (111)
planes of the Gd2O3 epilayer are rotated by 180 degree about the [111]
direction. In metal-semiconductor-metal schottky photodiodes fabricated with
these all-epitaxial Ge-on-insulator (GeOI) samples, significant suppression of
dark current is observed due to the presence of the Gd2O3 epilayer. These
results are promising for application of these GeOI structures as virtual
substrates, or for realization of high-speed group-IV photonic components.Comment: 15 pages, 6 figure