Volume 35, Issue 2

In this work, we present a numerical study of an all-optical logical gate based in a symmetric nonlinear directional coupler (NLDC) in Photonic Fiber Crystals (PCFs) PCFs operating with two ultrashort fundamental soliton pulses of 100 fs, modulated by PAM-ASK with binary amplitude modulation to represent the logical level 1 and 0. The performance of a symmetric dual core NLDCPCF to execute two-input logical functions is examined. We evaluate the effect resulting from an increment in the PAM coding parameter offset ( ε ), considering the anomalous Group Velocity Dispersion (GVD), third-order dispersion ( β 3 ) and nonlinear effects Self Phase Modulation (SPM), Self-Steepening (SS), lntrapulse Raman Scattering (IRS) in a lossless configuration. Our results indicate that is possible to get logical operations for the cores 1 or 2 using a phase control to the input pulse in one of the fibers.

The ABCD matrix prescribed for a upside down tapered hemispherical microlens end drawn from a parabolic index circular core fiber is used to formulate analytical expression of coupling efficiency of excitation of this optical device by a laser diode. In our analysis, we assume Gaussian field distribution for both the source and the fiber. For maximum coupling efficiency, the lens transmitted spot size of the source should match with the fiber spot size. In our investigations, we employ two different laser diodes emitting wavelengths 1.3 μm and 1.5 μm respectively. It is found that the wavelength 1.5 μm is more efficient in the context of present coupling optics. Our formalism predicts the concerned coupling optics excellently and the execution of our formalism requires little computations. This simple but accurate technique is expected to benefit the system designers and packagers concerned with optimum launch optics.

We propose a novel scheme to generate optical frequency comb by using Mach-Zehnder modulator and recirculating frequency shifter loop based on IQ modulator driven by radio frequency clock signals. A system of 4 flat and stable comb lines generation based on Mach-Zehnder modulator is set as the seed light source of the recirculating loop. Through theorical analysis and simulation it is shown that the proposed theoretical model is proved in good agreement with simulation results.

The Optical Burst Switching (OBS) is an emergent result to the technology issue that could achieve a viable network in future. They have the ability to meet the bandwidth requisite of those applications that call for intensive bandwidth. The field of optical transmission has undergone numerous advancements and is still being researched mainly due to the fact that optical data transmission can be done at enormous speeds. The concept of OBS is still far from perfection facing issues in case of security threat. The transfer of optical switching paradigm to optical burst switching faces serious downfall in the fields of burst aggregation, routing, authentication, dispute resolution and quality of service (QoS). This paper proposes a framework based on QKD based secure edge router architecture design to provide burst confidentiality. The QKD protocol offers high level of confidentiality as it is indestructible. The design architecture was implemented in FPGA using diverse models and the results were taken. The results show that the proposed model is suitable for real time secure routing applications of the Optical burst switched networks.

In this paper, a kind of surface plasmonic waveguide (SPW) with two wedges separated by a nano-gap is presented. Based on the finite element method (FEM), the dependence of the distribution of electric field magnitude, effective index, propagation length, mode area of the fundamental mode and quality factor on the geometrical parameters and the shape of waveguide is analyzed. Results show that the distribution of electric field magnitude concentrates round the tips of the two wedges. The effective index decreases while the propagation length and mode area increase with the increasing angles of the two wedges or the increasing gap between the two wedges. Comparison with the SPW with single wedge has been carried out. It has been shown that the SPW with two wedges has better propagation properties than the SPW with single wedge. According to the simulation, when the gap is 2 nm and the angles of the two wedges are 1/18π–1/4π, the propagation length is at the order of 10 μm, the mode area can decrease to 0.3–8 nm 2 and the quality factor can be improved by 2–4 orders of magnitude than the single wedge SPW. Thus, it can be reasonably thought that this kind of SPW can be used in future ultradense photonic integrated circuits to avoid crosstalk or to improve the microminiaturization and integrated level. Finally, the possibility to use the SPW with two wedges in the area of sensor is discussed.

In this paper, the general structural models of single-fiber bidirectional wavelength division multiplexing passive optical network with star topology and ring topology are proposed. The performances of the two general structural models including network scale, construction cost and system reliability, are analyzed and compared numerically. In particular, link failure and node failure are considered as two different types of failures and discussed separately in the context. The characteristics of the two models, which are concluded in the end of this paper, can be the guide in the deployment of WDM-PON.

I have demonstrated a novel scheme to generate orthogonal frequency division multiplexing signals for radio over fiber systems using a fiber bragg grating and a direct-modulation laser. I employ the FBG because the bandwidth of the optical modulator is largely reduced and the architecture of the ROF system is simpler. Because no expensive broadband external modulator is used, the overall system is considered as a cost-effective solution. The simple structure and low cost of the DD-OFDM system is attractive for the future cost-effective systems.

In this work, simulative investigation to evaluate the performance of WDM based OFDM-RoF transmission links consisting of two- and four-channels OFDM-RoF transmission links at different transmission rates have been reported. Further, a comparison is carried out for 4 QAM and 16 QAM modulation schemes to evaluate the effect of Mary-coding on the performance of such systems at high transmission rates. The fading problems due to fiber dispersion is minimized by incorporating OSSB scheme in our proposed WDM based OFDM-RoF transmission links.

This work is focused on how to implement 4- and 8-channel dense wavelength division multiplexing (DWDM) system, with each channel of 10 Gbps over an optical span of 100 km in the presence of four wave mixing (FWM) under the impact of unequal-channel spacing and laser line-width. In this proposed work, we have evaluated electrical power, Q-factor and average eye opening of 4- and 8-channel dense wavelength division multiplexing in the presence of FWM under the impact of equal channel spacing of 0.24 nm and 0.27 nm at 100 kHz, 10 MHz and 100 MHz laser line-widths. The comparison of parameters in the terms of electrical power, Q-factor and average eye opening has been observed at different laser line-widths.