The precision of traditional methods of edge detection of precise Parts with linear CCD only reach &mgr;m because of the size
of CCD cells. A sup-pixel edge detection method of CCD based on least square method and derivative operator method is
proposed to improve the measurement precision. The Image Gradient obtained using derivative operator method. Point A
with the max Gradient is then regarded as the point of the edge, and then the pixels nearby edge are interpolated linearly. For
example, a high-speed data acquisition system is designed using high accuracy linear CCD TCD1501D and high speed A/D
converter TLC5510. Experimental results show that the resolution &mgr; of the system design is 0.02pixel and the
measurement precision is improved by one order of magnitude over traditional methods of edge detection.
A comprehensive study of the noise characteristic in optical balanced receivers in differential phase shift keying (DPSK) systems is performed. The receiver model based on Karhunen-Loève (KL) transform which may include the main transmission impairments in WDM systems is proposed as well as the numerical computation techniques for bit error ratio (BER) assessment. The statistics of the decision current is obtained which shows exact agreement with that of Monte-Carlo simulation, so the analytical result is reliable for accurate estimation of BER. After validated by the time consuming Monte-Carlo error count, the proposed model is adopted in a back-to-back simulation and the 3 dB advantage of DPSK over traditional on-off keying (OOK) is clearly verified.
This paper studies advanced optical phase modulation formats in 40Gb/s Ultra-long-haul systems. As well known, the performance of 40Gb/s Ultra-long-haul systems depends upon the modulation formats. Since DPSK modulation format has higher spectral efficiency and more tolerance to fibre nonlinearity induced impairment, different duty cycle has important impact on result. In this letter, we comprehensively analyzed the transmitting performances of optical phase modulation formats with using the eye-opening penalty (EOP). NRZ-DPSK, full frequency modulated RZ-DPSK (FullRZ-DPSK), half frequency modulated RZ-DPSK (HalfRZ-DPSK) and CSRZ-DPSK modulation formats was numerical simulated within four kinds fiber system: G.652 Fiber, True Wave fiber (TW), True Wave-Reduced Slope fiber (TW-RS) and Large Effective Area Fiber (LEAF). Through modelling and simulation, we compute the EOP of these phase modulation formats, with different average optical input power. The numerical simulation result shows thatCSRZ-DPSK is best performance in all phase modulation, and G.652 outperforms other types of fibers in 40Gb/s Ultra-long-haul systems.
This paper studies the routing and wavelength assignment (RWA) problem in wavelength-routed all-optical networks with dynamic traffic demand. As well known, the performance of network restoration strongly depends upon the routing and rerouting policies. In this letter, we comprehensively analyzed the restoration performance under two main alternate dynamic routing algorithm, LLR(Least Loaded Routing) and FPLC(Fixed-Paths Least-Congestion routing), and two
rerouting policies, based on K-path backup or Dijkstra algorithm. Through modelling and simulation, we compute the restoration efficiencies of four combinations on the NSFNET T1 backbone network, with different traffic load. The numerical simulation result shows that the rerouting policy based on Dijkstra algorithm has improved more 10%-20% performance than the rerouting policy based on K-path backup. The LLR and FPLC routing algorithm achieve the same performance by and large when the same rerouting policy is used.
This paper studies PMD compensation problems in the optical communication. In an adaptive compensation process of a practical PMD compensator, three main parts are included: an equalizer, a detection part and an algorithm. In order to achieve faster and simpler, particle swarm optimization (PSO) algorithm was introduced to this process. Although the original PSO algorithm is easy to trap into sub-optima, we proposed a new modified PSO to avoid sub-optima but keep the simplicity at the same time. This is the first time to introduce the conception of collision into PSO arithmetic, so it is called collision PSO. Through the numerical simulation, this proposed method showed the better result than the original PSO methods.