Volume 34, Issue 1

Coherent population oscillations (CPO) in quantum dots (QDs) have been utilized in this article to achieve slow and fast light effects in a semiconductor optical amplifier. These phenomena have been achieved based on a pump-probe scheme and tuning the input current source. Coupled rate equations have been developed to determine the carrier dynamics and occupation probabilities. The effects of barrier, wetting layer and excited state densities have been included for CPO phenomenon occurring between the ground states. A quantum disc model embedded in another disc has been assumed for modeling the QDs and density matrix elements are used to obtain induced polarization at the signal frequency after determining the energy states and state probabilities. Tunable absorption dip, corresponding refractive index variation and group index, exhibit widely tunable slow and fast light characteristics by changing the bias condition.

A novel hyperchaos synchronization system is presented. Hyperchaos synchronization in injection two-section semiconductor lasers was achieved for its application in secure communication. We found also a route from single-period to hyperchaos after passing quasi-period and chaos with increasing frequency detuning while the receiver synchronized with the transmitter in these dynamical regions. All optical private data communication encoded by a rate of 0.16 Gbit/s on/off phase shift key and a rate of 0.16 Gbit/s amplitude modulation and photoelectric private data communication encoded by a rate of 0.2 Gbit/s on/off current shift key and a current modulation of 0.12 GHz frequency, respectively, are simulated via this hyperchaos synchronization system. Decoding has been numerically demonstrated to achieve successfully.

In this paper, performance evaluation of Ethernet Passive Optical Network (EPON) in the absence and presence of Dispersion Compensation Techniques (DCT) has been observed. It has been observed that Q 2 value lies in the range of 22 to 13 and 26.5 to 24 for transmission distance at 0 to 30 km in case of RZ without and with DCT. In other case, it lies in the range of 23.5 to 14.5 and 27.5 to 25 for transmission distance at 0 to 30 km in NRZ without and with DCT in EPON. Using dispersion compensation technique we can increase the transmission speed as well as transmission distance of EPON systems.

We propose and present a cost effective and simple technique of simultaneous generation and propagation of millimeter wave with recently standardized 10 giga bit passive optical network (GPON) by mixing of 2.5 Gbit/s, 30 GHz radio wave with 10 Gbit/s based band signal and then modulated by single Mach Zehnder modulator (MZM). In this scheme, we have applied 1490 nm for downstream, 1310 nm for upstream transmission and ON OFF keying (OOK) modulation format to make it fully align with existing standards and infrastructure. Simulation results show error free transmission performance with negligible power penalty over 25 km bidirectional fiber. We also highlight the principles and discuss the main technical challenges for commercial realization of 60 GHz spectrum.

In this paper, the performance of radio-over-fiber (RoF) links employing intensity modulation has been investigated in terms of bit-error rate (BER) and optical signal-to-noise ratio (SNR). An analytical model including dispersion, laser and radio frequency (RF) oscillator phase noise is constructed to estimate the BER performance for 16-quadrature amplitude modulation (QAM) based radio over fiber systems. It has been observed that the RF oscillator line-width and filter bandwidth affect the BER significantly. BER increases monotonously as the value of laser line width increases but for increased RF oscillator line widths specifically above 1 Hz, the BER degrades to a great extent [10 −2 ] which is not desirable for efficient communication system.

Using Chebyshev power series approach, accurate description for the first higher order (LP 11 ) mode of graded index fibers having three different profile shape functions are presented in this paper and applied to predict their propagation characteristics. These characteristics include fractional power guided through the core, excitation efficiency and Petermann I and II spot sizes with their approximate analytic formulations. We have shown that where two and three Chebyshev points in LP 11 mode approximation present fairly accurate results, the values based on our calculations involving four Chebyshev points match excellently with available exact numerical results.

This article formulates a framework that solves the offline physical layer impairment-routing and wavelength assignment (PLI-RWA) issue in translucent wavelength division multiplexed (WDM) optical networks. For network design, the PLI-Signal Quality Aware RWA (PLI-SQARWA) algorithm is employed that (a) guarantees zero blocking due to signal degradation and wavelength contention and (b) minimizes the total required number of regenerators and all-optical wavelength converters (AOWCs). Further, in view of a latency efficient technology capable of delivering a cost effective implementation suitable for large scale deployment, our previously proposed novel electro-optical hybrid translucent nodes are deployed within the network. Unlike our previous studies which assumed the use of full range wavelength converter (FRWC) within the hybrid node, in the current study, we use limited range wavelength converter (LRWC) to resolve wavelength conflicts. For network equipped with hybrid nodes and employing PLI-SQARWA, performance results, in presence of FRWCs and LRWCs, respectively are presented.

In this paper we approximate the fundamental mode in single mode step-index linear and nonlinear optical fiber by single Lorentzian parameter within scalar variational framework with improved version of previous field. We show that it improves in performance in comparison to earlier one in wider range of V and works well in low- V region more accurately in terms of propagation constant, group delay and wave-guide dispersion.

Two-dimensional photonic crystal structure based on Thue-Morse sequence is studied. The proposed structure is a candidate for studding optical properties of a Thue-Morse sequence and it is shown that by changing some properties of the proposed structure such as radiuses, refractive indices and so etc. optical properties of it, varied. Also bandgap of the proposed structure has enough ability to be controlled. For this structure, results show that with suitable selection of crystal structure bandgap engineering could be realized.