Volume 45, Issue 1

Optical amplifiers are developed to boost up the performance of the communication systems. Amplifiers such as erbium doped fiber amplifier (EDFA), RAMAN and semiconductor optical amplifier (SOA) are used for this purpose. It is mandatory to use optical amplifiers for signal transmission to long distances. In this paper, the hybrid optical amplifier EDFA-RAMAN-EDFA is proposed to enhance the signal quality received at receiver end and to initiate the efficient transmission of 8 × 10 Gbps transmission speed for wavelength division multiplexed (WDM) system. The proposed mechanism is evaluated with respect to various parameters such as quality factor, eye-height, and bit error rate (BER) and eye diagram considering various values of transmission distance ranging from 100 to 200 km. The analysis shows that the proposed mechanism has better quality factor value and minimum BER value than the traditional approach. Wider eye opening for proposed technique represents that the distortions produced in the system are least.

Tera hertz optical asymmetric demultiplexer (TOAD) using two semiconductor optical amplifiers and two control signals has been used to design an all optical parity checker and generator. The same circuit can generate and check both even and odd parity using a control input. The numerical simulation using Matlab 2007b is done for performance analysis of the proposed device in terms of output bit pattern, amplified spontaneous emission (ASE) noise, extinction ratio, contrast ratio, pseudo eye diagram, relative eye opening (98.9% for 20 dB gain and 96.21% for 10 dB gain) and their variation with input control pulse energy, amplified spontaneous emission noise factor for different unsaturated gain. The simulated value of E.R. = 81.39 dB, C.R. = 83.15 dB, REOP = 98.9% and Q value = 86.16 dB are found for this proposal.

The sensing of different liquids is investigated with micro-ring resonator (MRR) sensor by changing refractive index (RI) of chemical solutions. Aniline, carbon disulphide, chlorobenzene, chloroform, ethanol, glycerin, and methanol are detected using the proposed MRR. The developed structures are simulated using finite difference-time domain (FDTD) by using DFT analyzer of optical field. The normalized amplitude vs. wavelength is measured by changing RI of inner ring waveguide that obtain liquid sensor with high sensitivity.

Multilevel modulation formats have been now investigated very much to increase the speed and data capacity of optical communication networks in the limited bandwidth. Quadrature phase modulated signal has captured the attention of the researchers in this aim due to its high spectral efficiency and less bit error rate. Quaternary Bit-Swap logic operation is very important fundamental logic operation related to fast and secure computing and communication. Here in this report the authors propose a new method of implementation of all-optical quaternary Bit-Swap logic operation with quadrature phase modulated signal using four wave mixing.

In order to select the heterogeneous multicore fiber (MCF) configuration with ultra-low crosstalk and low peak bending radius, comparative crosstalk analysis have been done for the three possible core configurations, namely, Configuration 1 - different refractive index (R.I.) and different radius, Configuration 2 - different R.I., and Configuration 3 - different radius. Using the coupled mode equation and the simplified expressions of mode coupling coefficient (MCC) for different configurations of heterogeneous cores, the crosstalk performance of all the heterogeneous MCF configurations along with the homogeneous MCF have been investigated analytically with respect to core pitch ( D ) and fiber bending radius ( R b ${R}_{b}$ ). Further, these expressions of MCC have been extended to obtain the simplified expressions of MCC for the estimation of crosstalk levels in respective trench-assisted (TA) heterogeneous MCF configurations. It is observed from the analysis that in Configuration 1, crosstalk level is lowest and the rate of decrease in the crosstalk with respect to the core pitch is highest compared to the other configurations of heterogeneous MCF. The values of crosstalk obtained analytically have been validated by comparing it with the values obtained from finite element method (FEM) based numerical simulation results. Further, we have investigated the impact of a fixed percent change (5%) in the core parameters (radius and/or R.I.) of one of the core of a homogeneous MCF, to realize the different heterogeneous MCF configurations, on the variations in crosstalk levels, difference in the mode effective refractive index of the core 1 and core 2 ( Δ n e f f = n e f f 1 − n e f f 2 $\Delta {n}_{eff}={n}_{eff1}-{n}_{eff2}$ ), and the peak bending radius ( R p k ${R}_{pk}$ ). For the same percent variations (5%) in the core parameters (radius and/or R.I.) of different configurations of cores (Config. 1-Config. 3), Config. 1 MCF has highest variation in Δ n e f f $\Delta {n}_{eff}$ value compared to other configurations of MCF. Further, this highest variation in Δ n e f f $\Delta {n}_{eff}$ value of Config. 1 MCF results in smallest peak bending radius. The smaller value of peak bending radius allows MCF to bend into smaller radius. Therefore, Configuration 1 is the potential choice for the design of MCF with smaller peak bending radius and ultra-low crosstalk level compared to the other configurations of SI-heterogeneous MCF.

We present investigation of Petermann I and II spot sizes in the presence of Kerr nonlinearity. Our study is based on the simple power series formulation for fundamental modal field of single-mode-graded index fiber developed by Chebyshev formalism. Based on the said power series expression in the absence of nonlinearity, analytical expressions of the said spot sizes can be prescribed. Using the analytical expressions of the said spot sizes in the absence of nonlinearity, we apply iterative technique in order to predict the said propagation characteristics in presence of Kerr nonlinearity. In this context, we choose some typical single-mode step and parabolic index fibers. We show that the our results agree excellently with the exact results which can be obtained by using rigorous finite-element technique. This leads to verification of accuracy of our simple technique. Moreover, evaluation of the concerned parameters by our formalism involves little computation. Thus, our method provides an accurate but simple alternative to the existing rigorous methods in this context. Accordingly, this novel and simple formalism will prove user friendly to the system engineers in the field non linear optics.

Heterogeneous IoT-enabled networks generally accommodate both jitter tolerant and intolerant traffic. Optical Burst Switched (OBS) backbone networks handle the resultant volumes of such traffic by transmitting it in huge size chunks called bursts. Because of the lack of or limited buffering capabilities within the core network, burst contentions may frequently occur and thus affect overall supportable quality of service (QoS). Burst contention(s) in the core network is generally characterized by frequent burst losses as well as differential delays especially when traffic levels surge. Burst contention can be resolved in the core network by way of partial buffering using fiber delay lines (FDLs), wavelength conversion using wavelength converters (WCs) or deflection routing. In this paper, we assume that burst contention is resolved by way of deflecting contending bursts to other less congested paths even though this may lead to differential delays incurred by bursts as they traverse the network. This will contribute to undesirable jitter that may ultimately compromise overall QoS. Noting that jitter is mostly caused by deflection routing which itself is a result of poor wavelength and routing assigning, the paper proposes a controlled deflection routing (CDR) and wavelength assignment based scheme that allows the deflection of bursts to alternate paths only after controller buffer preset thresholds are surpassed. In this way, bursts (or burst fragments) intended for a common destination are always most likely to be routed on the same or least cost path end-to-end. We describe the scheme as well as compare its performance to other existing approaches. Overall, both analytical and simulation results show that the proposed scheme does lower both congestion (on deflection routes) as well as jitter, thus also improving throughput as well as avoiding congestion on deflection paths.

Distributed high-bandwidth consumption services such as cloud computing require large-capacity, long-distance, and wide-coverage development requirements for Next-Generation Passive Optical Networks (NG-PON2). With the development of NG-PON2 technology, the optical line terminal (OLT) device structure of passive optical network (PON) system is also increasingly complex and heterogeneous. This leads to the problem of network congestion and low bandwidth utilization caused by the unbalanced use of link and port resources in the traditional core network in the PON network. Based on the 40G coherent PON experimental system, this paper studies the traffic balancing problem of OLT equipment, and proposes a dynamic traffic balancing strategy based on real-time monitoring of load sharing and reporting of police and periodic adjustment. The experimental results show that the designed dynamic traffic balancing strategy can effectively reduce the PON network blocking rate and improve bandwidth utilization.

The blocking probability is studied for improving the quality of service of the network. The call blocking model for mode of operation to determine the types of applications suitable for Generalized Multi-Protocol Label Switched (GMPLS) networks is proposed. The performance of optical network depends upon various parameters such as number of channels, number of sources, traffic intensity which directly affect the blocking probability of the network. A mathematical model of an optical network for blocking probability of cleared calls and holding calls is developed. In the proposed model, blocking probability of the network gets reduced with a large number of servers. The proposed models decrease the blocking probability of the network to a level of 10 –40 . In addition, the blocking performance for held calls is also analyzed to compare the amount of traffic intensity that can be handled and completed properly with that of the cleared calls probability. The blocking probability is less for cleared calls than that for held calls as more traffic intensity can be handled in case of cleared calls but the chances for call completion increases in case of held calls.

The study has outlined the performance evaluation of bidirectional wavelength division multiple access broadband optical passive elastic networks operation efficiency. Signal power level, Q coefficient parameter, and minimum data error rates are measured numerically in both downstream and upstream directions based on broadband passive optical networks (BPONs). The transmission data rate available in the downstream direction is 10 Gb/s, while its value in the upstream direction is 2 Gb/s. The suitable operating wavelength is selected in the near-infrared region around 1550 nm for minimum losses. The bits sequence length of the optical transmitter is taken in to account for testing the optical network performance efficiency. The proposed model has presented better performance than the previous model by 25.76 % in downstream direction and by 12.28 % in upstream direction. As well as the bidirectional wavelength division multiple access broadband passive optical elastic networks performance efficiency is measured.

Free Space Optical (FSO) communication systems are gaining popularity due to its tremendous speed, advanced capacity, cost effectiveness, secure and easy to deploy wireless networks. This technology has proven an effective choice for last mile applications and hard to reach areas where deployment of optical fibre links is not feasible. But FSO link is highly weather dependent and as signal passes through the atmospheric channel, the main impairments are the atmospheric turbulence, which induce fading and deteriorate the system performance. Delhi has a great potential for FSO communication because of its clear skies. Since there is no analysis for weather condition found in Delhi, this work provides analysis of typical Delhi weather condition ranging from heavy to light rain, fog and clear sky. The performance of FSO link is analysed in terms of attenuation and link length margin under different weather condition. The results are concluded to identify which atmospheric condition influences more on FSO link performance.

All-optical arithmetic and logic unit is an integral part of contemporary optical data processing network. Accordingly, in this paper a method to develop all-optical arithmetic unit has been proposed. The proposed logic unit consists of semiconductor optical amplifier (SOA) whose fast non-linear characteristics have been utilized for the execution of numerous binary logic operations such as AND, OR, NAND, NOR, EXOR, buffer etc., as well as arithmetic operations, for instance half-addition and half-subtraction, etc. Numerical simulations for the various logic operations have been realized and output verified for the 100 Gbps data rate. Numerical executions have been also done for the crucial key parameters as the bias voltage, confinement factor, and laser power, yielded with good extinction ratio more than 10 dB. The proposed design consists of SOA with benefits of design as rapid switching speed, consumes low power and avoids optoelectronic translation. The design is having with good prospect for impending all optical complex computing networks.

In this paper, the major aim is to enhance the bandwidth and therefore increase the capacity of the optical fibre communication system by reducing the dispersion in the fibre. Dispersion compensation is necessary to reduce losses and cost of the system. In this paper, we are basically focusing on reducing or decreasing chromatic dispersion. Chromatic dispersion is a type of dispersion in which pulse broadening occurs due to delay in different spectral components. We here make use of dispersion compensated fibre (DCF) for reducing the dispersion in the WDM system. Here, we basically use three dispersion compensated techniques (pre-compensation, post-compensation and mix compensation). The comparison in the three models of dispersion compensated technique is made in terms of transmission power vs. Q factor and also transmission power vs. Bit Error Rate.

Free space optics (FSO) systems have gained considerable attention because of their numerous features and services. It has evolved into a promising technology for high data rate transmission in wireless communication systems. However, there are some atmospheric effects which inhibit its performance. In this paper, performance of code division multiple access–free space optics (CDMA–FSO) by combining multidiagonal (MD) codes and orthogonal frequency division multiplexing–free space optics (OFDM-FSO) systems over using advance line coding formats under the sway of turbulence conditions are investigated and compared. A comparative study has shown that CDMA–FSO offers better SNR with both CSRZ and AMI coding format under diverse conditions at data rate 15 and 20 Gbps.

System performance, which depends on the data transmission rates and propagation distances between two satellites in low Earth orbit (LEO) based on wavelength division multiplexing (WDM) techniques, is thoroughly studied. This study demonstrates the effect of WDM techniques on multi transceiver inter-satellite wireless optical communications. The system performance parameters with propagation distance at a multiple transceiver system are discussed using two previous models. The system performance parameters are investigated with 250 Gb/s transmission bit rates and 5000 km propagation distances for 16 transceiver systems. The maximum quality factor (Q factor), light peak signal per noise ratio, and signal peak per noise ratio are the primary important performance parameters in this study.

Free space optics (FSO) can be used as an alternative to the currently used wireless radio communication systems to meet the increasing demands for the uninterrupted internet connection in High-Speed Trains (HSTs). FSO is less prone to interference, license-free and more secure as compared to Radio Frequency (RF) technology. In this paper, we have compared three different wavelengths (850, 1330, and 1550 nm) for the dual-wavelength model at a bit rate of 10 Gb/s to see which two wavelengths provide better results. The system is studied for return to zero (RZ) and non-return to zero (NRZ) modulation formats this electronic document is a “live” template and already defines the components of your paper [title, text, heads, etc.] in its style sheet.

This paper analyzes the effects of laser linewidth on the performance of eight-channel dual-polarization quadrature phase-shift keying (DP-QPSK) dense wavelength division multiplexing (DWDM) transmission at 50 GHz channel spacing. The performance of differential encoding and Gray coding is compared with the system without any coding for the DP-QPSK DWDM system. It is shown that the differentially-encoded system performs better for lasers with linewidth (∆ν) greater than 0.04 MHz compared to the system with Gray coding and system without any coding. However, for lasers with linewidth lesser than 0.04 MHz, the three systems considered here perform equally and there is no need for differential or Gray coding in such a case. It is also shown that if we apply frequency offset estimation (FOE) before adaptive equalization (AE) in the digital coherent receiver then it further improve the performance of the differentially encoded system with lasers sources having linewidth even greater than 0.1 MHz.