An externally modulated AM-VSB CATV transport system in the 1550nm region using negative dispersion fiber (NDF) as the transmission medium is proposed and successfully demonstrated. Good performances of carrier-to-noise radio (CNR), composite second order (CSO) and composite triple beat (CTB) were achieved over an-80km NDF transmission without dispersion compensation. Externally modulated transmitter has a positive residual Mach-Zehnder modulator (MZM) chirp; but, NDF has a negative dispersion property in the transmission fiber. This negative dispersion property overcomes the positive frequency chirp and results in system with better transmission performance.
Pseudomorphic In0.25Al0.75P/In0.75Ga0.25As high electron mobility transistors (HEMTs) were fabricated to investigate the short-channel effect in the sub-0.1-µm gate-length region. Employing a thin Schottky barrier and a thin channel layer structure enabled us to suppress the short-channel effect in short-gate HEMTs, and a high-performance 47-nm-gate HEMT with a 423-GHz current gain cutoff frequency was achieved. The present results show the possibility of the practical use of pseudomorphic HEMTs with a scaled-down structure for various applications, such as ultra-high-speed digital circuits and millimeter-wave communications/observations.
Parametric Raman nonlinearities in Silicon waveguides is used to demonstrate wavelength conversion from Stokes to anti-Stokes channels. The effects of two photon absorption and free carrier nonlinear losses on the conversion process have also been analyzed. We find that scaling down the waveguide dimensions to submicron sizes is advantageous in terms of increasing the Raman nonlinearities and reducing the carrier lifetime and hence nonlinear absorption.
Modified sign Haar transform with sign Walsh-like structure is introduced in this article. This nonlinear transform converts binary/ternary vectors into digital spectral domain and is invertible. Recursive definitions for the calculation of this transform have been developed. The properties of logic functions and variables in the spectral domain of the modified sign Haar transform are presented.
Stimulated Raman scattering (SRS) degrades the performance of wavelength-division-multiplexed (WDM) optical fiber communication systems by amplifying the longer-wavelength channels at the expense of shorter-wavelength channels, and making the spectral profile of transmission tilted. The spectral transmission tilt due to SRS of single-mode fiber span is measured by using a technique to separate it from the total loss profile of the fiber. An empirical model is developed to predict the transmission tilt for single-mode fiber of any fiber length under various optical power levels. The application of the model in test and evaluation of gain-flattened optical fiber amplifiers is introduced.
This paper presents the design and performance analysis of low-noise and low-power 0.35µm SiGe UWB amplifiers for 3.1-10.6GHz radio receivers, which have been approved by the US Federal Communications Commission on Feb. 14, 2002. Particularly, common-gate amplifiers show good characteristics that are controllable with a single current source. These amplifiers give typical gain of 10.2dB, which is flat to within ±0.3dB variation over 3.1-10.6GHz. The noise figure achieved is about 5.1 dB and power dissipation is 5.6mW under a power supply of ±1.5V. The results stand high when compared to recently published figures.