Volume 44, Issue 2

The unbounded growth of Cloud-based services and Internet-of-Things (IoT) using Software Defined Networking (SDN) has resulted in bandwidth requirements that have grown enormously over the years. To meet this exponential growth that is currently outpacing Moore’s Law, we need Optical Interconnection Networks (OIN) that can satisfy the user’s requirements. In a similar direction Arrayed Waveguide Gratings (AWG)-based optical interconnects have been heavily investigated in past and many switch designs have emerged over the period of time. This paper proposes a dual-buffer-based optical switch design where the primary buffer stores the contending packets, while the secondary input buffer stores the contending packets which are blocked by AWG for one slot duration only. Moreover, if a blocked packet is generated on the same node then All-Optical Negative Acknowledgement (AO-NACK) will be used for blocked packets. This paper investigates the various issues related to storage of blocked packets, the analysis is done both at physical and network layers in terms of bit error rate (BER) and packet loss probability, respectively. It is found that with proposed switch design BER is 10 times lower than the earlier design, and the number of re-transmitted packets at the load of 0.8, reduces to 26 from 32 as in earlier switch design.

This paper describes study of photonic crystal fiber (PCF) in order to study the influence of temperature on the chromatic dispersion; these types of fibers are based on commercial structures, but air holes will be infiltrated with water. Using finite domain-beam propagation method, it is shown that the zero dispersion wavelength can be shifted from 1.058753 to 1.271767   µm, a shift of 213   nm. At 50   °C, a shift of 169   nm. As a result, we reveal that the proposed PCF can successfully compensate for the chromatic dispersion by the influence of temperature. Furthermore, the design model and methodology can be applied to design other dispersion-based devices, such as dispersion-flattened fibers and dispersion-shifted fibers, or can be used also as a sensor of temperature.

The generation of 80 GHz millimeter wave (mm-wave) signal and its transmission over single mode fiber (SMF) is presented. The mm-wave signal is generated with dual parallel dual drive Mach Zehnder modulators using frequency quadrupling of 20 GHz radio frequency signal. Transmission of generated mm-wave signal over SMF has been investigated. The impact of varying modulation depth on optical side band suppression ratio and radio frequency spurious suppression ratio for different extinction ratios (ER) is studied. Further, the impact of dispersion, on received power is also analyzed. Error analysis between analytical and simulation results is carried out. It has been observed, that increasing ER leads to reduction in both peak error and mean error and the received power is reduced under the combined effect of second and third order dispersion at very high modulation depth.

VCSEL can be used as the transmitter for optical interconnect applications especially for short reach communication. In this research paper, we proposed a VCSEL structure design which can generate the wavelength of 1160 nm. The VCSEL structure is proposed with the aim of small aperture diameter because for optical interconnects applications the size should reduce. Two distributed Bragg reflectors (DBR), i. e. top DBR and bottom DBR are used to confine the active cavity area and InGaAsP/InP material is used for the formation of active cavity region. Then, the performance of the proposed VCSEL is evaluated at various oxide aperture diameters in the range 2–7 µm for anode voltage, anode current and total power emitted is also calculated to achieve optimized performance.

A simple and accurate method based on degenerate four-wave mixing (FWM) to evaluate optical fiber dispersion and nonlinearity is presented. We investigated the continuous wave degenerate FWM characteristics of two photonic crystal fibers (PCFs) and a SMF28 fiber. Simply by measuring and analyzing the continuous wave degenerate FWM conversion efficiency as a function of the wavelength difference between pump and signal waves, fitting between experimental data and analytical FWM conversion efficiency expression is carried out to determine the dispersion, dispersion slope and nonlinear coefficient of the fiber. The fiber parameters simultaneously obtained from a single set of FWM measurement for Single Mode Fiber 28 (SMF28) are found to be agreement with the manufacturer specifications for this fiber, thus validating the PCF results and, more generally, the acceptable accuracy of the simple method proposed here.

With the rapid development of mobile Internet, high-definition video and cloud computing, users’ bandwidth demands are not only larger and larger but also more and more diverse. To solve this problem, there searchers put forward the concept of elastic optical network (EON). EON adopts the transmission mode of elastic grid, which can allocate spectrum resources flexibly and meet high bandwidth and diversity requirements at the same time. Routing and spectrum allocation (RSA) is an important issue in EON. In this paper, we present a heuristic algorithm named constrained-lower-indexed-block (CLIB) allocation algorithm for the RSA problem. The algorithm is based on the K candidate paths. When there are available spectrum blocks on multiple candidate paths, if the increase of the path length does not exceed a given threshold, the lower index spectrum would be selected for the connection request on a longer path. The aim of the algorithm is to concentrate the occupied frequency slices on one side of the spectrum and leave another side of the spectrum to the later arrived connection requests as much as possible, to reduce the blocking probability of connection requests. Simulation results show that comparing with the first-last-fit and hybrid grouping algorithms, the CLIB algorithm can reduce the blocking probability of connection requests.

In this paper, a competent flat gain hybrid optical amplifier is proposed with an optimum arrangement of erbium doped fiber amplifier (EDFA) and Raman amplifier. Attempts are made to design a hybrid optical amplifier for100 channels, 10 Gbps super dense wavelength division multiplexed (SDWDM) systems at channel spacing of 0.1 nm. Work capacity of the system was compared on the basis of various parameters, viz., noise figure and gain that determined the performance of the system. The gain spectrum of the hybrid optical amplifier depends upon the parameters viz., laser input power, pump power and pump wavelength of the amplifier. It was found that for wavelength range 1,560.38–1,579.59 nm, a flat gain of 4.34 dB is achieved for input power of −10 dB with noise figure variation of 0.818 dB without using any gain flattering scheme. Being simple and cost effective, this hybrid optical amplifier could be recommended for gain flatness characteristics and acceptable noise figure for dense wavelength multiplexed systems.

This paper proposes a novel method for constructing optical zero-correlation zone (OZCZ) codes based on the Mutually Orthogonal Complementary Sets (MOCS) matrix and the concatenation operation. The most important property of the obtained codes is that the periodic correlation function of the proposed codes is zero for the phase shifts within the zero-correlation zone. The procedure of construction is simple, flexible and offers increasing number of users M = 2 n + 1 \left( {M = {2^{n + 1}}} \right) . In the other hand, we have presented a fully reconfigurable hardware implementation based on very high description language of the proposed OZCZ codes for optical code-division multiple-access encoder system. The implementation is performed on an Altera field-programmable gate arrays device using ROM memory and an up counter. The simulation results have been found satisfactory and are in conformity with the theoretical observations.

The outage performance of FSO system assisted with decode and forward relay is studied using diversity techniques like wavelength and time which helps in mitigating atmospheric turbulence. The channel modelled using Malaga turbulence model with the combined effects of path loss and pointing errors. We derive outage performance analysis for multi hop system using no, wavelength and time diversity schemes, respectively. And we justified the usage of diversity techniques, Because of which the FSO system performance gets enhanced.

A free-space optic (FSO) system model considering non-Hermitian orthogonal frequency division multiplexing (OFDM) modulation followed by optical differential quadrature phase shift keying (DQPSK) modulation is proposed. Analysis is presented for an OFDM-DQPSK FSO link considering an optical direct detection receiver based on dual detection optical QPSK demodulator. Analytical approach is developed to find the expressions for output current and signal to noise ratio (SNR) in presence of atmospheric turbulence. The conditional bit error rate (BER) for a given turbulence-induced fading is also derived. Average SNR and BER are obtained considering the turbulence-induced fading to be log-normal distribution. Results are evaluated in terms of average SNR and BER for different link distances, number of OFDM subcarriers, background current and different wavelengths. It is noticed that the proposed OFDM FSO system suffers 4 and 1.4 dB power penalty at a BER of 10 −12 due to the effect of atmospheric turbulence and background radiation respectively for 512 number of OFDM subcarrier and link distance of 2,000 m. Comparison of the results is made with simulation results as well as experimental results reported earlier. The proposed OFDM FSO system provides better performance, with an almost 3 dB improvement in receiver sensitivity compared to the experimental results on OFDM-QPSK FSO link reported earlier at a BER of 10 −6 . Finally, the analytical results are verified by numerical simulation.

Large capacity optical networks require flattened gain spectrum and large gain bandwidth of the optical networks. In order to achieve this large number of hybrid optical amplifiers are designed. Here we proposed a competent flat gain hybrid optical amplifier with an optimum combination of Erbium Doped Fiber Amplifier (EDFA) and Raman amplifier. Attempts are made to design a hybrid optical amplifier for 100 channels, 10 Gbps Super Dense Wavelength Division Multiplexed (SDWDM) systems at different channel spacing of 0.1, 0.2, 0.4 and 0.8 nm. Work capacity of the network was compared on the basis of various parameters viz., gain and noise figure that determined the performance of the system. The gain spectrum of the hybrid optical amplifier depends upon the parameters viz., pump wavelength, pump power and laser input power of the amplifier. Various efforts were conceded out to optimize these parameters. It was found that for wavelength range 1,570.5–1,580.75 nm, a flat gain of 5.36 dB is achieved for input power of −15 dB with noise figure variation of 0.57 dB without using any gain flattering scheme. Being simple and cost effective, this hybrid optical amplifier could be recommended for gain flatness characteristics and acceptable noise figure for super dense wavelength division multiplexed system.

In quantum optical computing both of Pauli X, Y, Z gates and Hadamard gate are essential and important issues. Several proposals are given for addressing these issues. In this paper, the authors propose polarization encoded all-optical schemes which implement Hadamard logic, Pauli X, Pauli Y and Pauli Z gates followed by Hadamard logic gate separately. An integrated scheme is also proposed where three Pauli gates (X, Y and Z) followed by a single Hadamard gate is developed using polarization encoding mechanism. The outputs of the proposed systems follow the truth tables of the respective operations exactly. As the systems use the polarization character of light, so fully quantum optical operations with superfast speed are achieved.

Copper nanoparticles (Cu) anchored lithium niobate (LiNbO 3 ) nanostructures were prepared by a simple hydrothermal technique. The fine and sparse Cu nanoparticles were homogeneously dispersed over the surface of LiNbO 3 . An effectual anchoring of Cu was evidenced from the acquired reflection planes in diffraction analysis, which clearly indicate the face-centered cubic structure of Cu. The UV-Visible spectrum of LiNbO 3 and Cu/LiNbO 3 nanocomposites were also studied. When the Cu nanoparticles were doped with LiNbO 3 /LiTaO 3 superlattice system, the change in the dispersion relation was observed theoretically. The characteristics of the polariton dispersion variation with filling factor of Cu nanoparticles concentration were investigated systematically. The importance of the polariton modes in communication sector was analyzed and the occurrence of new modes on the polaritonic gap, where the propagation of the electromagnetic wave is forbidden, were obtained in the system due to the presence of copper nanoparticles.

Radio over Fibre (RoF) transport of high-speed wireless data provides a comprehensive solution for the forthcoming highly-reliable and spectral-efficient wireless systems. MIMO is one of the most widely used wireless technologies to increase the system reliability and capacity without any increased demand of power/bandwidth. However, the inherent non-linearities of RoF link and the multipath fading of the wireless channel can degrade the overall performance of the wireless system. In this work, authors demonstrate RoF transport of adaptively modulated MIMO signals and report the improvement in spectral efficiency under the impact of RoF link non-linearity. The transmitter of the proposed RoF based wireless system selects the appropriate modulation scheme with the assumption of perfect channel state information to achieve the acceptable BER at the subscriber end. The spectral efficiency improvement by this self-recovering MIMO-RoF system is evaluated by incorporating orthogonal Space-Time Block Code with 2 × 2 antenna configuration over the frequency-selective Rayleigh fading channel.

This paper proposes an ultra-high capacity free space optical communication (FSO) system, employing optical dual polarization quadrature phase shift keying (DP-QPSK) modulation format. It is a 16-channel dense wavelength division multiplexing (DWDM) system with 120 Gbps/channel bit rate. The FSO system is analyzed with three optical advanced modulation schemes; such as 4-quadrature amplitude modulation (4-QAM), quadrature phase shift keying (QPSK) and DP-QPSK. The main focus of the projected system is to improve the FSO setup performance in terms of eye diagram, bit error rate (BER), high received power and Q-factor. The center channel wavelength used for the proposed system is 1550 nm. In the present wireless communication world, the proposed system will be highly helpful as an ultrahigh capacity wireless system.

In the last decade, huge development has been seen in the field of wireless communication. The performance depends on the shape and size of the antenna. The future aim of wireless communication is to provide data with high speed data range even in harsh geographical areas. Here aim is to design and compare the E and H slot, T-slot, O-slot and U-slot antenna. The designed patch antenna operates at a frequency of 60 GHz with maximum antenna gain and minimum radiation loss using high frequency structure simulator (HFSS). We will use Rogers RT/duroid 5880 as substrate due to its suitable mechanical and insulating properties. Resonant frequency used will be 60 GHz and height will be 1.6 mm, 1.57 mm, 1.6 mm and 0.508 mm for E and H slot, T-slot, O-slot and U-slot, respectively.

A cost-effective spectrum sliced wavelength division multiplexing radio over free space (SS-WDM RoFSO) full duplex communication system architecture has been proposed and analyzed. For the downlink, a 10 Gbits/s high spectrally efficient and amplitude maintaining modified duobinary return to zero (MDRZ) modulated the filtered slices from the light source. The free space optical (FSO) channel was modeled by the well-known Gamma-Gamma model and was further subjected to moderate rain attenuation conditions. Four FSO transceivers were used to mitigate against laser beam scintillation, geometrical losses and rain attenuation. For uplink, a reflective semiconductor optical amplifier (RSOA) was used both as a modulator and an amplifier. Its amplitude squeezing effect was used to erase the information in the MDRZ modulated downstream seeding wavelength for uplink transmission of 10 Gbits/s NRZ OOK signals. At a bit error rate (BER) of 1.262 × 10 − 9 $1.262\times 10^{-9}$ , our proposed architecture revealed that 10 Gbits/s symmetric SS-WDM RoFSO can achieve 4.167 km of free space transmission. Power penalty of approximately 0.2 and 3 dB was achieved for downstream and upstream, respectively, which assures the feasibility of the proposed architecture. Such a system is meant to co-exist with the forthcoming fifth generation long-term evolution urban systems.