Spectrum-efficient and scalable elastic optical path network: architecture, benefits, and enabling technologies

The sustained growth of data traffic volume calls for an introduction of an efficient and scalable transport platform for links of 100 Gb/s and beyond in the future optical network. In this article, after briefly reviewing the existing major technology options, we propose a novel, spectrum- efficient, and scalable optical transport network architecture called SLICE. The SLICE architecture enables sub-wavelength, superwavelength, and multiple-rate data traffic accommodation in a highly spectrum-efficient manner, thereby providing a fractional bandwidth service. Dynamic bandwidth variation of elastic optical paths provides network operators with new business opportunities offering cost-effective and highly available connectivity services through time-dependent bandwidth sharing, energy-efficient network operation, and highly survivable restoration with bandwidth squeezing. We also discuss an optical orthogonal frequency-division multiplexing-based flexible-rate transponder and a bandwidth-variable wavelength cross-connect as the enabling technologies of SLICE concept. Finally, we present the performance evaluation and technical challenges that arise in this new network architecture.     

Polarimetric Characteristics of sea ice in the sea of Okhotsk observed by airborne L-band SAR

The Phased-Array L-Band SAR (PALSAR) aboard the Advanced Land Observing Satellite (ALOS) is capable of globally acquiring fully polarimetric data. In order to confirm the ability of L-band polarimetric synthetic aperture radar (SAR) to investigate sea ice before the ALOS launch, we conducted a field experiment using an airborne Polarimetric and Interferometric SAR (Pi-SAR) in the Sea of Okhotsk in 1999. This paper presents the analyzed results of data acquired in that experiment. The extracted polarimetric parameters of several ice types suggested that polarimetric coherences and phase differences between right-right (RR) and left-left (LL) are good candidates for discriminating ice types. The polarimetric anisotropy as well as the beta angle of the first eigenvector calculated in the polarimetric decomposition procedure are alternative parameters that are sensitive to ice type differences. Due to the low depolarization characteristics of open water, it could be discriminated from sea ice by scattering entropy in all incidence angle ranges. From the relation between ice thickness and the polarimetric parameters, we found that backscattering coefficients and vertical (VV) to horizontal (HH) backscattering ratio are highly correlated with ice thickness. Since the ratio is sensitive to ice surface dielectric constants, a simple simulation using the integral equation method surface model was conducted by using the physical parameters of typical sea ice. A two-dimensional ice thickness map was derived from an empirical relation between the VV-to-HH backscattering ratio and ice thickness.     

Dependence of single-longitudinal-mode probability on DFB laser facet structure

The probability of single-longitudinal-mode (SLM) operation is calculated for three kinds of DFB facet structures. To obtain high SLM probability, a DFB laser with cleaved facets requires relatively large kL, but the introduction of asymmetry to facet reflectivity greatly relaxes the kL requirements.     

Drain structure optimization for highly reliable deep submicrometern-channel MOSFET

A guideline for n^- fully gate overlapped (FOLD) structure design optimization has been studied. From the viewpoint of reliability, the greatest reduction in substrate current directly leads to the most reliable n^- design for the FOLD structure. The current path modulation phenomenon due to the trapped charge at the n ^- extension region dominates the hot-carrier induced characteristics change for conventional lightly doped drain (LDD) structure with side-wall spacer. This phenomenon is minimized in the FOLD structure due to its higher controllability of the gate electrode than the LDD structure at the n^- extension region. Furthermore, it was also confirmed that the 0.3 μm optimized FOLD structure can achieve high circuit performance at 3.3 V operation, maintaining hot-carrier resistance     

Broad wavelength tuning under single-mode oscillation with a multi-electrode distributed feedback laser

Broad wavelength tuning under single-mode oscillation is achieved for a 1.5 ?m range multi-electrode distributed feedback laser. The lasing wavelength can be tuned electrically, maintaining a stable single-mode oscillation without mode jumping. The tuning has reached over 20 ? under a noticeable condition of constant power (5mW), with a sufficient side-mode suppression ratio over 30 dB.     

InP/InGaAs double-heterojunction bipolar transistor with step-graded InGaAsP collector

An MOCVD-grown InP/InGaAs double-heterojunction bipolar transistor with a step-graded InGaAsP collector is described. This transistor allows high injection current densities over 2.9*10/sup 5/ A/cm/sup 2/, which suggests no significant current blocking related to the wide-gap InP layers. A cutoff frequency of 155 GHz and a maximum oscillation frequency of 90 GHz are obtained at the collector current density of 1.6*10/sup 5/ A/cm/sup 2/.<>     

Nanoindentation as a strength probe—a study on the hardness dependence of indent size for fine-grained and coarse-grained ferritic steel

A nanoindentation hardness testing system, including an atomic-force microscope (AFM)-based nanoindentation tester and a calibration method using electrolytically polished single-crystal metals as references, was proposed. This was applied to a study of the mechanical properties of fine-grained ferritic steel (grain size of 1.2 μm) and coarse-grained ferritic steel (30 μm). An empirical function giving the macroscopic hardness for all four reference metals from the nanoindentation force curves was established. The converted Vickers hardness (HV*) of the coarse-grained steel is almost independent of the indent size. The fine-grained steel shows only HV* 130 with an indent of only 100 nm, compared with a macroscopic hardness of HV 210. The difference, HV 80, is considered to reflect the amount of grain-boundary strengthening. The critical indent size for the hardness transition seems to be around 1 μm, comparable to the grain size of the specimen. This result supports the explanation of grainboundary strengthening. It is also consistent with Pickering’s work on low-carbon steel, as the estimated locking parameter (k of 2.6×10⁵ N/m^3/2) in the Hall-Petch relationship is in good agreement with his value of 2.4×10⁵ N/m^3/2.