Band 42, Heft 3

This paper aims to analyze the performance of FBG 60 channel wavelength-division multiplexing system using different optical amplifiers namely RAMAN, erbium-doped fiber amplifier (EDFA) and semiconductor optical amplifier (SOA) separately at 10 Gbps data rate up to a fiber length of 280 km. Based upon the results, the performance of the three amplifiers has been compared on the basis of multiple performance parameters. It is seen that EDFA simulates good results in terms of bit error rate (BER) up to a fiber distance of approximately 80 km and Q factor up to a distance of approximately 90 km among all the three amplifiers. However, power received is least in EDFA. RAMAN amplifier provides a better Q factor after the fiber distance of approximately 90 km and a better BER after the fiber distance of approximately 80 km compared to the other three amplifiers. SOA shows better results in terms of power received up to a fiber distance of approximately 100 km. RAMAN amplifier provides better output power after a distance of 100 km. Eye diagrams and power spectrums of the network with different optical amplifiers has also been analyzed.

In this paper, OR and AND logic gate functions are realized in a triangular lattice using two dimensional photonic crystal (2DPC). The proposed design of logic gates are based on the phenomenon of resonance and interference. The OR and AND logic gates are constructed by varying the rod radius and by creating Y-shaped waveguide in the structure. Initially, the OR gate is designed with reference input and without reference input and it’s extended for AND gate. The functional parameters of the logic gates such as response period, bit rate, contrast ratio and field distribution of different logics are investigated through 2D finite difference time domain (FDTD) method. The contrast ratio, response period, bit rate and size of the three input OR gate are 30 dB, 0.52 ps, 1.92 Tbps and 12.6 μm×11 μm, respectively. Similarly, the aforementioned parameters are estimated for two input OR gate, two input AND gate and three input AND gate. The proposed logic gates are highly desirable for integrated optics.

This research work provides an insight on a radio over fiber (RoF) based passive optical network (RoF-PON) utilizing two diverse electrical phase shifts with optical single sideband modulation (OSSB) by exploiting Mach Zender modulator. The influence of chromatic dispersion (CD) in PONs employing single mode fiber (SMF) is a noteworthy issue and should be limited. The two techniques of OSSB modulation, in view of the two distinct angles of the hybrid coupler are employed for the design and implementation of RoF-PON. The RF signal is partitioned into two ways equally before applying it to the dual drive Mach Zender modulator input, utilizing an electrical hybrid coupler that imparts two discrete phase shifts of 90° and 120° to generate two OSSB signals individually. By utilizing traditional OSSB technique having 90° phase shift, either of the first-order sideband (lower or upper first order) suppression occurs yet second-order harmonics are still existent in the system. As opposed to this, the OSSB technique using 120° phase shift causes the suppression of either lower first order and higher second order sideband or vice versa. When contrasted to the PON based on traditional technique (90° phase shift technique), the suppression of second order sideband in PON using 120° technique lessens the system CD. Hence the PON based on 120° phase shift technique has enhanced functionality in terms of system BER, received power and power losses as compared to that with traditional OSSB technique.

Due to the explosive growth in internet traffic, servers are facing bottleneck in speed and bandwidth requirements. To meet these ever increasing demands fiber optic technology can be used. This paper discusses, a hybrid buffer based optical packet switch design with its pros and cons. This hybrid buffer offers both electronic and optical buffering. This paper investigates the packet loss rate (PLR) performance of hybrid buffer under variety of conditions. The usage of buffer under different loading conditions has discussed. The sharing of electronic and optical buffers with respect to arrival of traffic is simulated, and delay ratio of electronic to optical buffering is computed. Average energy consumption at various loading condition is evaluated. The performance of switch is also investigated in a hypothetical five nodes network, and PLR is obtained under four different combinations of buffering and deflection of contending packets.

All optical majority gate is an optical logic structure with three input and one output ports. In this paper we designed an optical majority gate using a nonlinear resonant cavity based on photonic crystals. Plane wave expansion and finite difference time domain methods were used for calculating the band structure diagram and optical behavior of the optical majority gate, respectively. The proposed structure is ON, when two or three input ports are ON. The maximum time delay of our majority gate is about 5 ps.

Optical packet switching (OPS) is an emerging area of research in next-generation datacenter applications. There is an exponential growth in the internet traffic due to applications such as social networking, cloud computing, video streaming, etc. Fiber optical network plays a critical role in various data center (DC) operations. Large bandwidth of the optical fiber made OPS, a promising technology for DCs. Arrayed waveguide gratings (AWGs) are used more frequently in the core of optical packet switches due to its low insertion loss and wavelength dependent routing pattern. Optical switching function can be performed by AWG if each input port is properly equipped with Tunable wavelength converters (TWCs). This paper presents analysis of four optical packet switches namely AWG and Feedback Loop Buffer based switch, AWG and Electronic Memory based switch, Petabit Optical Switch, AWG and Feedback Loop Buffer Loss Compensated based Switch. Switches are analyzed for Bit Error Rate (BER) and energy consumption. The power and noise analysis is performed for calculating the total power required for correct operation of switch and to determine the BER using physical layer analysis. Minimum power level is determined so that received bits are decoded correctly. Energy consumption per bit is also evaluated to identify architecture consuming less energy in the considered architectures.

The purpose of this paper is to demonstrate an implementation of Er 3+ /Yb 3+ codoped glass waveguide amplifiers (EYDWA) as a post-amplifier can provide an extended reach and a high split-ratio for the cost-effective implementation of hybrid fiber-to-the-x (FTTx) and free space optical (FSO) technologies. The performance has been compared on the basis of transmission distance, however the results of simulation show enhancement offered by EYDWA. This amplifier was able to reach transmission distance ratio of 160:5 km for GPON:FSO. Moreover in this paper, was study different characterizations of EYDWA amplifier, which depend essentially on the opt-geometric parameters, such as concentrations of ions erbium, length of the waveguide amplifier and the effect of those parameters to optimize the gain G, quality factor Q, min of BER and eye diagram.

The required upgradation of the single-mode fibre (SMF)’s network capacity constrained by the non-linear Shannon’s limit, and the capacity provisioning which is needed by the future diverse Internet traffic can be resolved by the space division multiplexing (SDM) based elastic optical networks (EONs) (SDM-b-EONs). Recently, the multiple core fibre (MCF) technology has gained momentum over the current multi-fibre (MF) technology after laboratory experiments conducted on MCF models established much lower inter-core crosstalk values. In view of channel assignment, the spatial-super-channel (Spat-Sup-Chn) method has evolved as a prime candidate owing to its use of the joint switching (JoSw) mechanism which minimizes the cost. In the current work, in a JoSw based MCF enabled SDM-b-EON, for provisioning the demands; we aim at cost minimization while assigning both, the spectral and the spatial resources. Initially, we establish that in specific cases; use of the complete core allotment (CCA) technique, which uses all the MCF cores to provision the demands, leads to spectrum underutilization following which; we introduce a novel core adapting allotment (CAA) technique which adapts the cores amounts. We then investigate the possibility of using the CAA technique to provision the Spat-Sup-Chns simultaneously ensuring the same spectral requirements as needed when the CCA technique is used. For the performance evaluations, we consider the 37 core trench-assisted MCFs and our results show that by using the CAA technique, indeed there is a possibility of the transceivers amount being minimized in effect resulting in the Spat-Sup-Chn method being an economically practical solution.

With the increase in demand of bandwidth hungry applications, it is recommended to develop a high data rate system for long-haul coherent optical orthogonal frequency division multiplexing (CO-OFDM). At a very high data rate, CO-OFDM signal experiences deterioration. At 50 Gbps, the signal experiences ISI effect and in order to overcome this ISI effect, a prolonged system has been developed to reach optimal ISI compensation technique. One of the prominent and competent techniques to enhance system performance is (SDCM) symmetrical dispersion compensation module. In order to make system more bandwidth efficient 4-QAM (Quadrature Amplitude Modulation) with gray coding is applied and manual adjustments are done at receiver phase to decrease error vector magnitude (EVM). OFDM data stream is successfully transmitted over a distance of 4,000 km to compete the demand of long-haul CO-OFDM system. With different launch powers and laser linewidths, the performance of the system is enhanced in terms of Q -factor, SNR and EVM.

Optical communication has given new means to faster more secure and efficient means of passing information. This paper draws a comparison of various multiplexing techniques used in free space optics and intersatellite communication to enhance data rates and user over a single channel under the impact of turbulences.

Self-Phase Modulation affects the performance of Radio over Fiber (RoF) system by inducing spectral broadening of the transmitted pulse and thereby produces dispersion. This paper analyses the effects of SPM on optical pulse propagating through the fiber and proposed a SSP (symmetrical-symmetrical-post) compensation technique to overcome the effects of SPM in single-tone RoF system. The simulation results reveal that the pulse broadening due to SPM is reduced by utilizing SSP compensation technique in the transmission channel as it provides a 2 dB increase in OSNR as compared to the conventional compensation technique. The proposed technique provides an optimum result at a bit rate of 40 Gbps and launched power of 10 mW over a transmission distance of 400 km for mitigating SPM effects.

Optical wireless communication is one of the emerging technologies. Over the last few years it has been the growing interests which have some indoor and outdoor applications. The demand for wireless communication has been growing day-by-day. With radio spectrum, there are some problems related to congestion, limitations on bandwidth as the number of users are increasing day-by-day. As a result, optical wireless communication systems are been used which provides high data rates, much higher bandwidth, unregulated spectrum and highly secured networks. In this paper a review is done on optical wireless communication. Various fields and applications are discussed like under water, space, aircrafts, light fidelity (Li-Fi), etc. Different light sources, coding schemes, modulation techniques are discussed. Also some of the challenges are discussed here.

Cross-phase modulation (XPM) is one of the major limiting effects in wavelength division multiplexed (WDM) optical transmission systems. This paper mathematically investigates the impact of XPM-induced crosstalk with second (2OD), third (3OD) and combination of sub-planck higher-order dispersion (HOD) parameters for WDM systems at different combinations of effective core areas, optical powers, modulating frequencies and dispersion values. It has been observed that XPM-induced crosstalk increases with increase in optical powers, modulating frequencies and dispersion values, but it reduces for higher effective core areas. The results for 2OD, 3OD and combination of dispersion parameters up to eighth order (8OD) have been reported. For instance, with a transmission length of 50 km for different values of optical power ranging from 0.1 mW to 2 mW, crosstalk due to XPM was observed to vary from (−75 to −44 dB), (−172 to −144 dB) and (−275 to −250 dB) in the presence of 2OD, 3OD and ∑n=48nOD \mathop \sum \limits_{n = 4}^8 n{\rm{OD}} combination, respectively. On the basis of analysis, one can select the appropriate frequency as well as the value of dispersion or type of fibre to achieve minimum crosstalk.

The development of SAC-OCDMA system is based on the creation of new code structure. A novel proposed code structure is called ZFD that is based on the combination of various matrix creation methods and especially on the factorial function. This approach has not been exploited before in the OCDMA system. This novel code has its own advantage that represented in its possibility to generate code-words in flexible way by setting variable basic codes at fixed code weight. The performance of this proposed code is demonstrated via mathematical methods. It is represented by its optimal cross-correlation to avoid the multiple access interference (MAI). Consequently, the effects of the contributed noises using direct detection method have been considered. These noises are represented by shot noise and thermal noise. In addition, a system of three users was simulated with ZFD code under the C band (1530–1565 nm) for the upstream signal with different channel spacing (0.8, 1 and 1.2 nm). In this paper, several parameter effects such as fiber length, effective source power and data rate have been studied and compared to prove the effectiveness of this code. Also, ZFD code has been compared to some other codes such as RD, EDW and MDW according to the previous parameters. The suggested code has reached good results in terms of the bit error rate (BER) and the eye diagram.

In this work, OFDM (orthogonal frequency division multiplexing) is analyzed for different transmission schemes on the basis of BER (Bit Error Rate), transmitting-receiving signal, constellation diagram and the best transmitting scheme is determined for OFDM. OFDM is analogous to Frequency Division Multiple Access (FDMA) in which the multiple user access is achieved by sub-dividing the existing spectrum into various channels, which are then allocated to users. In this paper Mat-lab simulation OFDM is used to see, how the Bit Error Ratio (BER) of a transmission varies when signal to Noise Ratio (S/N) and Multi-Propagation effect are altered to transmit a computer file in binary data from modulated by 16-QAM and QPSK modulation, finally at the end of the transmission, when the receiver receives the data, a comparison of the transmitted and the received messages is done in order to calculate the Bit Error Ratio (BER).

It is known that the high bandwidth demands are accomplished by deploying the concept of wavelength division multiplexing in optical networks which involves the transmission of multiple wavelength signals spaced very close to each other. Due to closely spaced wavelengths, the signal power of one channel phase modulates the adjacent channel which in turn produces nonlinear effects such as cross-phase modulation (XPM), self-phase modulation (SPM) and four-wave mixing (FWM). Thus, in this paper, PC-DCF (pre-compensating dispersion compensating fiber) technique has been demonstrated and evaluated in the transmission link to compensate the XPM effects, and this result seems to significantly enhance w.r.t. transmission performance and system capacity considering performance metrics such as Optical Signal to Noise Ratio (OSNR), bit rate, Q-factor and bit error rate (BER). It is evident from the simulation results as well as through mathematical modeling that the proposed technique (PC-DCF) provides optimum results at the channel spacing of 100 GHz, bit rate of 10 Gbps and input power of 5 mW which collectively provides a 5 dB increase in OSNR as compared to the existing compensating technique.

A scheme to suppress nonlinear intermodulation distortion in microwave photonic (MWP) link is proposed by using polarizers to compensate inherent non-linear behavior of dual-electrode Mach-Zehnder modulator (DE-MZM). Insertion losses and extinction ratio have also been considered. Simulation results depict that spurious free dynamic range (SFDR) of proposed link reaches to 130.743 dB.Hz 2/3 . A suppression of 41 dB in third order intermodulation distortions and an improvement of 15.3 dB is reported when compared with the conventional link. In addition, an electrical spectrum at different polarization angles is extracted and 79∘79^\circ is found to be optimum value of polarization angle.

Optical burst switching (OBS) is a new emerging network that is developing rapidly. By increasing the amount of traffic on the Internet the necessity for having networks like OBS ones that can carry heavy traffic is needed. These networks have an important problem due to being bufferless. The congestion control of the network is a little confusing for some protocols like transport control protocol (TCP) Vegas as they are appropriate for conventional wired networks not optical ones. When a drop happens in OBS networks it can be because of two reasons: 1. congestion and 2. Contention that has been possible due to the bufferless nature of the network. When a contention happens and a packet drops, TCP thinks that the network is experiencing heavy load however it may not, and it decreases the sending rate, as a result, it leads to a reduction in the performance of the network. In this paper, we are trying to improve the performance of the network by employing a new algorithm that called Fuzzy-RTT Performance Improver. This algorithm is based on fuzzy logic and round-trip time measurements. Simulative results show that this algorithm outperforms TCP Vegas in terms of throughput and packet delivery count.

The database replication mechanism ensures the duplication of data from one geographical location to another. In recent past, PDDRA (pre-fetching-based dynamic data replication algorithm) is investigated heavily under various classes of request arrivals. The request arriving at a particular server for replication depends on many factors such as bandwidth supported by link, its geographical location and routing algorithms. The number of served requests depends on the processing speed and buffering capacity of a particular server. If a request cannot be served at the server, it is dropped. If a bunch of requests arrive at a server, then traffic modelled as bursty traffic. The objective of this paper is to investigate the performance of dynamic replication algorithm under bursty request arrival. In a similar context, a mathematical model is detailed for the estimation of request burst length, such that both buffering capacity and transmission delay can be kept minimal. Finally, simulation results are present to evaluate the fraction of successful request under diverse conditions.

This paper presents a multi-hop coherent orthogonal frequency division multiplexing free space optical communication system (OFDM-FSO) model which includes a relay transmission mode of decode and forward (DF) over Malaga disrubution (M) and we analyse the results by deriving mathematical expressions for average bit error rate (BER) and outage probability. And the FSO link is characterized by path loss, pointing errors and atmospheric turbulence and also weather conditions like clear air, haze, light fog have been considered in the channel model. The BER and outage probability of the proposed system are examined including the effects of pointing errors and weather conditions. From this work, we can justify that with multi-hop configuration coverage area and signal power improves which bolsters the usage of relay in FSO communication for efficient and reliable system design.