Volume 32, Issue 4

In this article it is examined the influence between the projection size of the point light source and the detection error of coordinate center when projecting on the photo-sensitive matrix. With the help of simulation it is formed the dependence of detection error of coordinate from magnitude of dispersion radius projection in case of different position of light source relative to the receiver. Analized operating characteristic of two delimitation of coordinate algorithms: using maximal likehood method and using the centroid method. It is find of the ratio between the dispersion radius and size of receiver in the case of minimal error.

An optical, 2R regenerator based on self phase modulation (SPM) spectral broadening, combining a 4 m-wide rib waveguide and a surface relief Bragg grating, both written on a 5 cm-long Si chip is proposed and theoretically analyzed. Because of the SPM nature and its origin of Kerr optical nonlinearities, this regenerator has subpicosecond response time. The nonlinear power transfer curves are plotted using 2.5 ps input pulses and regeneration can be done at 120 Gbit/s. It is tried to do all the simulations on both a Silicon (Si) and a Chalcogenide (ChG) chip with the same size and spectral properties to have a fair comparison between these two materials. Simulations show more practical nonlinear power transfer function with the Si chip comparing to the ChG one. The phase-shifted Bragg grating written on the same rib waveguide is proposed to regenerate 60 ps-wide pulses, for the first time.

We present a new design for N -channel wavelength division demultiplexer using multistage multimode interference (MMI) structure. First, the general formulation for an N -channel demultiplexer in multimode area has been discussed. In this paper, we proposed a single parameter for designing a demultiplexer with desired wavelengths, number of output channels and channel spacing. Then we simulated an 8-channel wavelength demultiplexer with high quality factor in the telecommunication range. The simulated structure shows 5 nm channel spacing and 2451 average quality factor. The excellent properties of this formulation are the high quality factor and its capability for choosing the desired number of output channels and channel spacing. The beam propagation method is used for simulation of the proposed device.

A variety of unitary transforms have attracted considerable attention for their application in data, image compression and other signal processing applications. Among many transforms, the KarhunenLoeve transform (KLT) is known to be optimal because of its advantages of computational efficiency, residual correlation and rate distortion criterion. In this paper, it is shown that the all-optical KarhunenLoeve transform can be realized using multimode interference (MMI) structures on silicon wire waveguides. The transfer matrix method (TMM) and the beam propagation method (BPM) are used to verify and optimally design the proposed devices.

Hole-assisted fibers (HAFs) in a fiber ribbon have been studied for high-speed parallel transmission systems. This paper describes the influence of hole-structure variations on the group delay variation caused by stress, the mode field diameter (MFD), and the higher order mode characteristics. Calculations are made using the previously proposed calculation method with finite element method (FEM). We discuss the effectiveness and limitation of the previously proposed parameter based on the calculations.

For the hexagonal-lattice photonic crystal waveguides with the 60/120-bent sections, the light waves prefer to turn into the 120-bent section rather than propagate along the 60-bent ones. Our FDTD simulation results show that the backward optical fields (propagating along the 120-bent section) are more intense than the forward ones (propagating along the 60-bent section). And these results are in good agreement with those simulated by RSoft-BeamPROP.

Optical burst switching (OBS) has been regarded as the next generation optical switching technology. In this paper, the routing problem based on particle swarm optimization (PSO) algorithm in OBS has been studies and analyzed. Simulation results indicate that, the PSO based routing algorithm will optimal than the conversional shortest path first algorithm in space cost and calculation cost. Conclusions have certain theoretical significances for the improvement of OBS routing protocols.

In this paper, we propose a framework to construct multiple VNTs in WDM-based optical network and then propose a control scheme, which we call a managed self-organization, to achieve adaptive and efficient VNT controls. Our basic idea is that, we introduce a system manager for managing and controlling the overall performance in multiple VNTs environments. The system manager collects the activities that represent the conditions of VNTs, calculate the overall condition of the network, and loosely controls each VNT through the feedback of the information about the overall condition. Simulation results show that the VNT control with system manager can adapt to the large traffic fluctuation within 47 minutes, while the VNT control without system manager takes more than 200 minutes.

In this paper, Performance evaluation of Free Space Optics (FSO) communication in the presence of Forward Error Correction techniques has been observed. It has been observed that Q 2 value lies in the range of 17 to 10 dB and 26 to 12 dB at 2.50 Gbit/s in the absence and presence of FEC at transmission distance of 500 m to 1 km in Free Space Optics (FSO) communication. Similarly the BER lies in the range of 10 13 to 10 3 and 10 99 to 10 4 without and with FEC at transmission distance of 500m to 1 km. Hence with FEC technique, we have achieved BER of 10 9 at 950m with bit rate of 2.50Gbit/s in Free Space Optics Communication.

In this paper, a reliable Wavelength-Division-Multiplexing Passive Optical Network (WDM-PON) system is proposed. It can provide the protection against both the feeder fiber failure and the distribution fiber failure. When the fiber failure occurs, the corresponding switches in the OLT and in the ONU can switch to the protection link without affecting the users in normal status. That is to say, the protection for one ONU is independent of the other ONUs.

In this paper is presented an architecture aiming the distribution of orthogonal frequency division multiplexing (OFDM) signals, compatible with ultra-wide band (UWB) standards, in wavelength division multiplexing (WDM) radio-over-fiber (RoF) scenario. The suggested WDM architecture allows unicast and multicast transmission of OFDM signals within the standard millimeter-wave (mm-wave) UWB bands, from 3.1 to 10.6 GHz and from 57 to 64 GHz, respectively 8 GHz and 60 GHz. The generation of the OFDM-UWB signals with the desired mm-wave carriers' frequencies is made using an optical frequency-quadrupling technique, thus with lower bandwidth requirements for the optical modulator, and allowing the use of a lower frequency electrical drive signal. The OFDM-UWB signals distribution is fully passive, recurring to a cyclic AWG (Arrayed Waveguide Grating). Two types of modulation are used, double side band (DSB) for up-/down-link unicast transmission and DSB with carrier suppression for down-link multicast. In this later case, we avoid the need for high precision filtering, to remove the optical carrier at the receiver, providing a system with greater tolerance to frequency variations. The system's performance is evaluated for different bit rates, input powers and transmission distances, allowing transmission up to 12 km over single mode fiber (SMF), with a maximum EVM below the maximum permissible relative constellation error which is set to a root mean square (RMS) EVM of 14.13% ECMA-368 International Standard: High rate ultra wide-band PHY and MAC Standard, 2007.

In this paper we present a comparative study of the equalization enhanced phase noise (EEPN) for pre- and post-compensation of chromatic dispersion in high capacity and high constellation systems. This is to our knowledge the first detailed study in this area for pre-compensation systems. Our main results show that the local oscillator phase noise determines the EEPN influence in post-compensation implementations whereas the transmitter laser determines the EEPN in pre-compensation implementations. As a result of significance for the implementation of practical longer-range systems it is to be emphasized that the use of chromatic dispersion equalization in the optical domain e.g. by the use of dispersion compensation fibers eliminates the EEPN entirely. Thus, this seems an efficient solution for such systems operating at high constellations in the future.

A new code for reduction the phase induced intensity noise has been presented. The new code is proposed for Spectral Amplitude-Coding Optical Code Division Multiple Accesses (SAC-OCDMA). This new code family we call it Dynamic Cyclic Shift (DCS) code. The DCS code reduced the effect of Multi Access Interference (MAI) due to it is the property of variable cross correlation. We find that the performance of the DCS code is a batter than other SAC-OCDMA codes such as; Random Diagonal (RD) code, Modified Quadratic Congruence (MQC) code and Modified Frequency Hopping (MFH) code. Through the mathematical calculation and simulation analysis, for the bit-error rate of DCS code is significantly better than other SAC-OCDMA codes, the effect of Phase Induced Intensity Noise is reduced. In addition, proofof-principle simulations of 10 Gb/s for 20 km have been successfully demonstrated and achieved low BER compared to the other codes.

This paper proposes a scheme generating optical packets in OLS system, using Manchester-SCM for label and CSRZ-DPSK for payload based on dedicated wavelength techniques. Through simulation analysis, we get that this scheme can achieve more reliable transmission of optical packets compared to DPSK/SCM scheme previously studied.