We analyze signal waveform generated by a semiconductor optical amplifier (SOA)-based switch with a delayed-interferometric (DI) configuration by controlling an assist light under gain or transparent wavelength. To take advantage of the rectangular-shape waveform generated by the switch, we investigate and optimize the waveform quality by means of both Q-factor and concordance rate to rectangular-shape of the converted waveform.
We achieved high-speed wavelength division multiplexing (WDM) transmission in the visible to infrared region over a 1km photonic crystal fiber (PCF). We realized ultra-wide and high-speed WDM transmission using six wavelengths in the 658 to 1550nm wavelength range, which corresponds to a frequency bandwidth of 263THz. We demonstrated WDM transmission of 1Gbit/s at 658nm and 10Gbit/s at 780nm and four infrared wavelengths. Our experimental results show that low loss PCF is very attractive for use in future high capacity WDM systems with an ultra wide bandwidth.
A robust front-end pre-filter incorporating non-quadratic signal processing techniques is proposed. We will demonstrate the effectiveness of this filter in suppressing impulsive noises in a coded direct sequence code-division multiple access (DS-CDMA)communication system. Based on M-Estimation approach, the pre-filter works by minimizing an appropriate penalty function in an iterative fashion with minimal increase in computational complexity of the system. With the use of this pre-filter in the system, performance enhancement in excess of 6dB in non-Gaussian impulsive channels is demonstrated while maintaining comparable performance in Gaussian channel.
We have developed a special-purpose computer for analyzing X-ray scattering of models of macromolecules, named XSAM-2 (solution X-ray Scattering Analysis of Macromolecules). XSAM-2 contains 64 circuits operating in parallel for calculating X-ray scattering intensities using the pipeline method. XSAM-2 calculates 122 times faster than a personal computer with a Pentium 4 processor.
We propose a novel steganographic system that is able to provide a high quality stego image in spite of the high capacity of the concealed information. The number of insertion bits in a pixel is different according to each pixel's characteristics. In addition to that, our system is able to verify whether if the secret information was sent from the sender correctly or if an attacker forged the secret message. We use two frequency coefficients in DCT domain to generate the symbol code to check the integrity of secret information.
This paper investigates the performance of a MOS track-and-hold circuit as the front end of a wide input range and high-speed single-sided ADC. In order to reduce charge injection and clock feedthrough errors, a new technique for employing a dummy transistor in the bootstrapped switch of the track and hold circuit is introduced. Performance of the proposed circuit for the two cases of constant and non-linear hold capacitor is studied. It is also shown that how and when dummy switch and bulk switching method can improve the accuracy of the T/H.