Volume 43, Issue 2

The objective of current work is to design and analyzed 96×10 Gbps DWDM system taking EDFA, SOA, and RAMAN amplifier as an inline amplifiers up to a fiber length of 300 km. The performance of EDFA, SOA, and RAMAN amplifier is measured on the basis of power received, Q-factor, probability of error and BER for various values of fiber distance. In this paper it has been proved that for 96 channels DWDM system at 10 Gbps bit rate, EDFA reveals superior performance as far as the amount of power received is concerned. The value of quality factor (Q-factor) for RAMAN amplifier is almost identical to that of the Q-factor for EDFA and is higher than the Q-factor for SOA till a fiber length of roughly 80 km thereafter SOA reveals somewhat better Q-factor than EDFA and RAMAN amplifier. As far as BER is concerned EDFA and RAMAN amplifier show roughly identical and somewhat lower BER than SOA till a fiber length of roughly 80 km, afterwards SOA reveal somewhat lesser BER till the fiber length of 210 km. In relation to the probability of error P(E), It is analyzed that P(E) remains more or less same for the entire set of optical amplifiers(OAs) but beyond the fiber length of 240 km EDFA shows somewhat lower P(E) than the other two OAs. At the end the Eye diagrams for the three OAs are also figure out.

In this paper, Two Dimensional (2D) Photonic Crystal (PhC) based 3-input all optical NOR, NAND and XNOR gates is proposed and designed. The proposed device is formed by the combination of line defects and square cavity. The performance of the device is analyzed using 2D Finite Difference Time Domain (FDTD) method. The band gap analysis is done by Plane Wave Expansion (PWE) method. The device has the lattice constant and refractive index of 616 nm and 3.46, respectively. The dimension of the proposed structure is about 12.5 µm*12 µm which is highly compact and suitable for photonic integrated circuits (PIC).

The basic logic gates play a key role in performing the mathematical computation. The plasmonics has the uniqueness of confining surface plasmons beyond the diffraction limit. Plasmonic-based Mach-Zehnder interferometer with an extinction ratio of 26 dB is proposed to design the structure of all-optical XOR and XNOR logic gate. A theoretical analysis of proposed gate is carried out using finite-difference-time-domain method and MATLAB simulation results.

A porous core photonic crystal fiber (PCF) for transmitting terahertz waves is reported and characterized using finite element method. It is shown that by enveloping an octagonal core consisting of only circular air holes in a hexagonal cladding, it is possible to attain low effective material loss that is 73.8% lower than the bulk material absorption loss at 1.0 THz operating frequency. Moreover, a low confinement loss of 7.53×10 –5 cm −1 and dispersion profile of 1.0823±0.06 ps/THz/cm within 0.7–1 THz are obtained using carefully selected geometrical design parameters. Other guiding properties such as single-mode operation, bending loss, and effective area are also investigated. The structural design of this porous core PCF is comparatively simple since it contains noncomplex lattices and circular shaped air holes; and therefore, may be implemented using existing fabrication techniques. Due to its auspicious guiding properties, the proposed fiber may be used in single mode terahertz imaging and other short distance terahertz applications.

Passive Optical Network (PON) plays an important role in optical access network due to its characteristics of resources saving and network protocol transparency. In the process of running and operating a PON system, a reliable network management system (NMS) is necessary. In order to acquisition the management object, NMS should perform topology automatic discovery process with the help of embedded software. Aiming at various types of the convergence network’s topology and the complicated architecture, this article proposes a topology automatic discovery algorithm to promote the network management. We have designed and verified the automatic discovery method on our simulation platform with SNMP-Agent-enabled OLTs.

High-speed single-mode fiber-optic communication systems have been presented based on various hybrid multiplexing schemes. Refractive index step and silica-doped germanium percentage parameters are also preserved during their technological boundaries of attention. It is noticed that the connect design parameters suffer more nonlinearity with the number of connects. Two different propagation techniques have been used to investigate the transmitted data rates as a criterion to enhance system performance. The first technique is soliton propagation, where the control parameters lead to equilibrium between the pulse spreading due to dispersion and the pulse shrinking because of nonlinearity. The second technique is the MTDM technique where the parameters are adjusted to lead to minimum dispersion. Two cases are investigated: no dispersion cancellation and dispersion cancellation. The investigations are conducted over an enormous range of the set of control parameters. Thermal effects are considered through three basic quantities, namely the transmission data rates, the dispersion characteristics, and the spectral losses.

With the overwhelming use of the Internet, the wavelength division multiplexing (WDM) optical networks have become the major mode of communication for wide applications. Hence, the routing and wavelength assignment (RWA) for a given traffic in WDM networks is the chief challenge in optical networks. This paper presents the RWA problem in WDM networks using the hybrid algorithm of flower pollination (FP) and simulated annealing (SA) algorithm (FA+SA) with and without wavelength conversion capability at the nodes of the network. Comparative analysis with techniques presented in literature is also carried out, i. e. differential evolution algorithm (DEA), firefly algorithm (FA), particle swarm optimization with less number of informers (Psolbest), SA and genetic algorithm (GA). The results prove that hybrid algorithm of FP and SA is potentially more efficient than algorithms present in literature for the light path establishment in an optical network.

In Ethernet Passive Optical Network, with Load Adaptive Polling Sequence Arrangement (LASA) method, the Optical Line Terminal assigns delayed polling sequence arrangement for a set of Optical Network Units (ONUs) over the cycles. This arrangement has resulted in identical cycle time with Constant Bit Rate traffic. In addition, the LASA through its arrangement provides sleep mode to different set of ONUs over the cycles and provides maximum sleep time for ONUs. With these advantages of LASA and keeping the scenario with different cycle times for the ONUs, in this work, the Variable Bit Rate (VBR) based LASA method is analyzed. The variation in the cycle times has resulted in two cases and in each case by varying the maximum ( Mxi ) and the minimum ( Mni ) idle times, a maximum of 40.6% reduction in power consumption is observed in LASA with VBR scheduling method than traditional one.

There is a misunderstanding in Optical Burst Switching (OBS) networks about the congestion status in the network that can cause a reduction in the performance of the networks. OBS networks are bufferless in their nature so when a burst drop happens in the network it can be because of the congestion or contention in the network but TCP cannot distinguish it is due to the congestion or contention. TCP wrongly decreases the congestion window size (cwnd) and causes significant reduction of the network performance. In this paper we are trying to employ a new algorithm by using fuzzy logic and some thresholds to divide the network into several areas then we can solve the problem. This new scheme can help us to distinguish a burst drop is because of the congestion or a burst contention in the network. Extensive simulative studies show that the proposed algorithm outperforms TCP Vegas in terms of throughput and packet delivery count.

Optical Burst Switching (OBS) networks are new emerging techniques that alternate Optical Circuit Switching (OCS) and Optical Packet Switching (OPS) techniques. The high bandwidth of fiber links in these networks, besides WDM (Wavelength Division Multiplexing) helps the Internet to handle the heavy traffic. OBS networks have an important issue that needs to be tackled. These networks are bufferless in their nature, so when two bursts are trying to reserve one wavelength one of them is dropped. This drop can be assumed as an indicator of congestion; as a result, the sending rate will be decreased, despite the fact that the network may not be congested. So, wired protocols like TCP (Transmission Control Protocol) cannot work to their high potential in OBS networks. In this paper, we propose a new scheme based on a probable approach that can distinguish burst drops caused by contentions from burst drops caused by contention, so we can improve the performance of the network. Extensive simulative studies show that the proposed algorithm outperforms TCP Vegas in terms of throughput and packet delivery count.

In this work, an optical hybrid communication system is proposed. It is a combination of diffused link (DL) configuration of free space optics (FSO) setup and fiber optic setup. It is a 16-channel dense wavelength division multiplexing (DWDM) system, with 400 Gbps/channel data rate. It uses dual polarization-quadrature phase shift keying (DP-QPSK) modulation technique for all the setups. Bit error rate (BER), eye diagram, quality actor (Q-factor), optical time domain reflectometer (OTDR), optical spectrum analyzer (OSA) signals are considered as performance parameters of the proposed system. It is found that the link distance is 340 m for DL setup and 1,000 km for fiber setup. The system will be very much useful for solving first mile, last mile problem with long distance optical communication applications in 5 G era.

In this paper, the Spectral Amplitude Coding Optical Code Division Multiple Access (SAC-OCDMA) is investigated in Free Space Optics (FSO) using Zero Cross Correlation (ZCC) codes to evaluate its performance limits in terms of link range. The system is analyzed under clear, haze, moderate fog and dense fog weather conditions. This system has been evaluated numerically and by simulation analysis by maintaining the transmitted power at 10 dBm, for safety reason, according to International Telecommunication Union (ITU) and minimum acceptable BER of 10 {10} –9 . The simulation results shown that the present system can transmit 622 Mbps/1 Gbps up to maximum link range of 1450 m/1100 m and 61 m/54 m under clear and dense fog conditions, respectively.

Radio over fiber (RoF) is a promising solution for the next-generation wireless networks including fifth-generation Cloud/Centralized Radio Access Network (C-RAN). There exists a possibility to use Sigma Delta Modulated RoF (S-DRoF) that combines the advantages of analog RoF and digital RoF by means of sigma delta modulation (SDM) at the transmitter side subsequently replacing the employment of expensive and high-speed digital-to-analog converters. In this paper, we demonstrate the usage of second-order SDM for LTE 20 MHz signal having 64 QAM modulation on a central carrier frequency of 1.14 GHz for the implementation of S-DRoF for 20 km of standard single mode fiber with baud rate from 25 to 100 Mbaud. Furthermore, a comprehensive analysis of the design of SDM is explained followed by the experimental setup. The performance is reported in terms of error vector magnitude, constellations and adjacent channel power ratio. The results show that the proposed architecture performance is in with accordance to the limitations set by the 3GPP (Third Generation Partnership Project) standards and is a reasonable choice either for upgrading installed systems as well as for the new deployments.

The increase in the cardinality of the frequency encoding-optical code division multiple access (OCDMA) system directly affects the length of the optical code, which leads us to find a less expensive solution. In this work, I propose an improved version of the diagonal eigenvalue Unit code (DEU) called Enhanced diagonal eigenvalue Unit code (EDEU) that is much easier in terms of construction and short in code length compared to the DEU code. The results found showed that the performance of the EDEU code exceeds the DEU code in terms of bit error rate (BER), and allowed us to multiplex about 15 more users when using the EDEU code compared to the system using the DEU code. As a result, the EDEU code is very suitable for use in access and OCDMA systems and it can be seen as a strong competitor to existing codes.

In this work, we study the performance analysis of underwater optical wireless communication (UOWC) transmission link by incorporating optical code division multiple access (OCDMA) using pulse position modulation (PPM) to enhance the channel range and cardinality. Bit error rate (BER) variations are examined versus the range, modulation type (on–off keying (OOK), quadrature amplitude modulation (QAM), etc.), number of users as well as the channel attenuation caused by different water types. The power and transmitter inclination angle limitation, of the enhanced system, are also presented in order to determine the threshold for which the minimum BER 10 −9 is achievable.

Due to the increase in demand for high data rates in mobile communication, orthogonal frequency division multiplexing (OFDM) system is employed in many applications. It efficiently overcomes the effect of Inter-symbol Interference caused due to the fading of the channel, but Peak to Average Power Ratio (PAPR) is unitary of the disadvantages in OFDM System. In the stage-I, the OFDM system is designed with different modulation schemes like QAM-16, BPSK, and QPSK. In the latter stage, we work on the reduction of PAPR by using a clipping technique and we establish a significant reduction in PAPR as compared to the conventional clipping technique.