Volume 42, Issue 1

In this article, an experimental system based on the Quadruple Pass Double Stage with a tunable pass filter configuration, is used to amplify the output signal of the Erbium-doped fiber amplification and eliminate the noise due to the amplified spontaneous emission backwards. The pumping power of the second stage is set at 220 mW, and the input power at −50 dBm, a maximum gain of 68 dB at a minimum noise threshold is achieved.

This paper aims to study single-parameter and dual-parameter chaos control of a dual-ring erbium-doped fiber laser. We present the control model to pressure chaotic behavior of the laser to a periodic state or multi-periodic states by introducing a periodic mutational signal to adjust the losses of dual ring. When the loss of single ring is shifted between two different levels, the laser behaviors can be deduced to two single-period states, while two rings can emit cyclic pulses. We find a control-locking regime and discuss its frequency characteristic of the laser. When another signal is taken to control to perform on the loss, the laser can be deduced to show a period-2 state, a period-3 state, period-4 state and other multi-periodic states. And we find dual-dynamic controlled regimes, in which, one ring of the laser can be produced to show a periodic state while another ring presents a period-3 state. We find also a dual-period regime or a period-4 regime. When both the losses of dual ring are adjusted by shifting between different levels, the laser can produce a period-4, a period-6 and other multi-periodic states. The result indicates that chaos control of a dual-ring erbium-doped fiber laser can be realized using the single-parameter and dual-parameter methods.

An all optical encoder based triangular lattice shape photonic crystal (PC) is proposed. The device is composed of two ring resonator waveguides and two OR gate with four input ports waveguides and two output ports waveguides in triangular lattice shape PC. The band diagram of base PC structure calculated by plane wave expansion (PWE) method. Also, transmission and distribution of electrical field behaviors of the proposed device are verified by two dimensional finite difference time domain (2D-FDTD) method. The proposed 4 × 2 encoder can operate at third communication window range, considering definitions of logic 0 and 1 being the normalized transmission as less than 3% and greater than 95% respectively. Despite the nonlinear encoders, in our case, due to the non-use of non-linear effects such as Kerr effect, low input power required for encoder.

In this paper synthesis and extensive investigation of the microstructural and optoelectronic properties of polyaniline (PANI), Multiwalled carbon nanotube (MWCNTs) and MWCNTs reinforced PANI composites is presented. MWCNTs- PANI composites have been deposited by spin coating on silicon wafer substrate. Fourier Transform Infrared Spectroscopy shows no difference between PANI and its composites. However a change in peaks shape and absorption intensity has been observed. A strong effect of the MWCNTs weight percentage on the PANI/MWCNTs composites has been demonstrated. It was find that the thermal stability improved with increasing MWCNTs content. The optical band gap of the PANI thin films has been effectively tuned from 2.38 to 1.78 eV as the MWCNTs content increases from 5 to 15 wt.% The Current–voltage (I–V) characteristics of the fabricated devices shows a significant improvement in current with MWCNTs weight percentage content. It was observed a strong enhancement of composite in the conductivity as well as in the current level. The microscopic images show that the dispersion of MWCNTs into PANI leads to the formation a new conductive pathway.

The most recently developed optical encoders are based on non-linear Kerr effect which require high input power. Here, we report 8 to 3 optical binary encoder based on linear effects which greatly reduces the input power requirement. The proposed encoder consists of three optical 4-input port OR gates and an optical buffer gate. Simulation results have proved correct operation states of the encoder and numerical analysis is done in order to additional evaluation. The maximum switching delay and total footprint of proposed structure are about 160 fs and 1418 µm 2 , respectively.

In this proposed work, we have designed two-dimensional photonic crystal ring resonator (2DPC-RR)-based eight-channel demultiplexer for dense wavelength division multiplexing (DWDM) systems. The performance parameters of the proposed demultiplexer such as resonant wavelength, spectral width, quality factor, channel spacing and crosstalk are investigated. The demultiplexer consists of bus waveguide, quasi-square RR and L bend waveguides. Each quasi-square RR has eight-shaped microcavity with different refractive index, which plays an active role for channel selection. The plane wave expansion method is used to generate the modes and photonic band gap of the demultiplexer. The finite difference time domain method is employed to analysis the field distribution and normalized transmission of the proposed demultiplexer. The transmission efficiency, Q factor, spectral width and channel spacing of the demultiplexer are about 98 %, 2,022, 0.8 nm and 1.1 nm, respectively. The aforementioned results are meeting the requirements of the ITU-T G. 694.1 DWDM systems.

In this paper, an ultra-fast all-optical modulator, based on a new shape of nonlinear photonic crystal ring resonator, is designed and studied. Numerical methods such as plane wave expansion (PWE) and finite-difference time domain (FDTD) are used to perform simulations. The modulation technique consists of carrier light controlling by means of input light signal and Kerr effect. The investigation of extinction ratio and insertion loss within the carrier input power shows that the choice of 0.7 W is the optimal value of that power to ensure the tradeoff between both characteristics. The suggested modulator demonstrates an excellent extinction ratio about 20.8018, a very low insertion loss of −13.98 and a short switching time about 13.4 ps. According to the obtained results, the modulator can be considered as an ultra-fast and ultra-compact optical component.

A microring resonator (MRR) and an add/drop devices are presented to generate picosecond solitonic pulse and signal as multichannel localized wavelengths, applicable for WDM-based free space optics (FSO) communication. A Gaussian pulse is inputted to the first ring resonator of the proposed system. Because of the nonlinear Kerr effect, chaotic signals are created. The second MRR filters the generated signals and shape solitonic pulses, where the accurate FWHM of 20 ps with intensity of 2.45 W are obtained. The add/drop device is applied for tuning the solitonic pulses. Results indicate that a range of solitonic wavelengths from 1550 nm to 1600 nm are obtained, where FSR and FWHM are 144 pm and 5 pm, respectively. Finally, performance of the proposed MRR system is evaluated in terms of bit error rate (BER) and Q factor. In the analysis, the proposed solitonic pulse is compared to conventional counterparts. Using the proposed MRR system, BER and Q factor of WDM-based FSO are considerably improved.

In this paper, we have proposed a way for reducing the dispersion level in plastic optical grating fiber by optimizing the grating-coupling strength ( ξ ) numerically. The effects of average refractive index ( δn ) and temperature ( T ) variation on the dispersion properties are investigated. Results show that, for reducing the dispersion level, the ξ parameter should be optimized and the amplitude of the δn needs to be reduced. Also results show that the dispersion due to the wavelength shift induced by the temperature variation will be eliminated by operating at high ξ value.

A novel architecture of N × N reconfigurable multiwavelength optical cross-connect based on tunable fiber Bragg grating (FBG) and optical circulator is proposed. The effect of cross talk in dense wavelength division multiplexing system with 0.8-nm channel spacing at 9×10 Gbps is also evaluated. Optical signal to noise ratio achieved is 40.95 dB at input transmission power of −10 dBm with acceptable bit error rate, i.e. 1.16×10 −10 at −30 dB FBG cross talk in the presence of fiber nonlinearities. It is found that signal is transmitted to a distance of 50 km without optical amplifier.

Optical fiber communication is the backbone of the entire telecommunication industries in the world. In this work, the real-time backbone long-distance optical fibers (single mode) are tested and analyzed with two different wavelengths (1,310 nm and 1,550 nm) with the help of optical time domain reflectometer. Using these two different wavelengths, how the losses and events of the backbone optical fibers are changing are compared and analyzed. This work will give a way to study the nature of long-distance backbone optical fiber and understand the real-time application of the fiber optic communication.

The call blocking is the most vital factor in generalized multiprotocol label switching (GMPLS) Networks. Call blocking depends upon many factors such as traffic intensity, number of servers and number of links. Call blocking performance for GMPLS networks has been calculated in this paper by using a proposed mathematical model. The proposed model investigates the dependency of probability of call blocking upon the number of wavelengths and number of links. In the suggested model, the blocking performance of GMPLS network is improved.

Software-defined networking (SDN) and optical transmission are the most cost-effective technologies for implementing high-bandwidth-based communication in the fog/cloud computing environment. The passive optical network uses optical line terminals and optical network units as optical edge devices (OEDs) to deliver fog/cloud-based services effectively. The security of such OEDs is one of the key issues for successful implementation of fog/cloud computing over the SDN-based optical network. The main security challenge is to detect and prevent the malicious OED that transmitting abusing data-frames in the SDN-based optical fog/cloud computing network. An OED can be easily hacked by the attacker to launch intrusive attacks those affect the quality of service of the optical channel. In this paper, a secure framework is proposed for identifying malicious OED in the fog/cloud computing over the SDN-based optical network. It identifies the malicious OED and shifts it to the honeypot to mitigate and analyze the attack. It uses two-stage hidden Markov model (HMM), intrusion detection system (IDS)-based fog manager and an optical virtual honeypot device (OVHD). A two-stage HMM is effectively used to reduce the false alarms of IDS in the identification of malicious OED and shifting it onto the OVHD. The OVHD is created in the SDN-based optical network by using the concept of free-available-resource and optical network virtualization. The proposed OVHD logs all malicious activities as well as attacker’s path for preventing future attacks. In order to validate the proposed framework, the simulation of two-stage HMM is implemented in MATLAB and mitigation impacts of the internal attacks are studied by using iFogSim toolkit. The results show the effectiveness of the proposed framework.

In this paper, artificial neural network-based adaptive optimal threshold estimation for a two-dimensional optical code division multiple access conventional correlation receiver is proposed. A multilayer perceptron neural network with back-propagation learning algorithm is considered. This estimator uses the weight ( w ) and the length ( F ) of the code word, the number of active users ( Ν ) and the signal to noise ratio as inputs to estimate the required optimal threshold. We have evaluated the proposed approach on a data set of 46,200 samples. We have found that it gives accurate results: 0.029 for the root mean square error, 0.37% for the relative root mean square error and 99.984% for the correlation coefficient (R), which reflects the efficiency of the proposed optimal threshold estimator.

In this paper, we investigate the performance of a high-altitude platform (HAP)-based relaying free-space optical communication (FSO) system, where HAP plays a role as a relay node that employs detect-and-forward relaying scheme to connect between two ground stations (GSs). M$M$-ary pulse-position modulation (PPM), spatial diversity, and heterodyne detection receiver are used to improve the system’s performance. Instead of using multiple-input multiple-output (MIMO), which makes the HAP complex, multiple-input single-output (MISO) is applied to the uplink while single-input multiple-output (SIMO) is utilized for the downlink. Consequently, the HAP only needs a couple of transmit and receive aperture. The expression for the bit error rate (BER) of the proposed FSO system is derived considering the impact of atmospheric attenuation and turbulence. The achievable BER with low values has proved the feasibility of our proposed system. In addition, the advantages of using M$M$-PPM, spatial diversity, and heterodyne detection are demonstrated in terms of the power gain and the geometric distance between two GSs. Other useful information for system design regarding the required transmitted power, the number of transmit/receive apertures, the modulation level, and the local oscillator power is also provided in this paper.

In order to respond to the increasing demand of capacity and bandwidth caused by the high number of wireless applications and users, LiFi technology was introduced. It uses the visible light spectrum instead of the radio spectrum to transmit data wirelessly through the illumination of LED lamps. The main advantage of this technology is to provide wireless communications with high data rates. Other advantages include efficiency, availability, security and safety. Also, this technology uses free unlicensed spectrum, and it is cost-effective. Additionally, unlike RF systems, no multipath fading and the transmitter and receiver circuits are not complex. However, LiFi has several issues, which include high path loss, sensitivity to blockages and Non-line-of-sight (NLOS) situations. Probably, the biggest issue of LiFi is the uplink communication which is difficult to implement due to practical and cost reasons. Several future applications of this technology include places where RF is restricted such as hospitals and airplanes. Also, it can be used for traffic management, underwater communication, and outdoor access to the Internet. Moreover, it can be combined with WiFi technology either in hybrid technique or aggregated technique. It is found that later technique gives better results. Another possible application is the optical attocells. It is found that the hexagonal cells model is the best for deterministic deployments of optical APs, whereas the hard-core point process (HCPP) model is the best for random deployments. Furthermore, LiFi can be used for multiuser access with high data rate by using non-orthogonal multiple access (NOMA) technique. Due to the great features of LiFi, more applications and everyday life devices will adopt this technology in the future. However, Because of its limitations, it may not totally replace RF technology, but they will work collaboratively to achieve a better performance.

In this paper, we proposed an improved optical heterodyne scheme based on optical carrier suppression (OCS) and optical injection locking techniques (OIL) for prospective applications in radio-over-fiber (RoF) systems to generate high-quality millimeter waves. In our scheme, the 60-Ghz millimeter wave signal is generated by heterodyning the outputs of two vertical cavity surface emitting lasers (VCSELs) that are optically injection locked by the two modulation sidebands provided by a 30-GHz externally modulated master tunable laser with suppressed center wavelength. The combined OCS and OIL heterodyne method are not only able to eliminate the phase noise caused by the instability of laser frequencies, but also can further suppress the center wavelength, thus improving the heterodyne performance. We evaluate the transmission quality of the proposed RoF system from the center station to base stations through simulation, and results prove our proposed OCS-OIL-heterodyne scheme to have error-free propagation within a distance of 40 km, better than the OCS-heterodyne scheme.

Chaotic signals are regarded as secure carriers for communication due to its high sensitivity to parameter and initial condition perturbations. This paper studies the problem of optical secure communication modeled by the perturbed nonlinear Schrödinger equation. First, we prove that the chaotic signal can be easily produced from the optical soliton signal when external perturbations are executed to the Schrodinger equation. Chaos synchronization is then proved to be accomplished between the derived system and the original system which are different in the first-order derivative terms. Furthermore, we analyze the effects of system parameters on the chaos synchronization. Numerical results show that smaller differences can lead to more rapid synchronization. We also find that changing system parameters can affect the speed of chaos synchronization.

This paper introduces a novel code called two dimensional Pascal’s triangle zero cross correlation (2D-PTZCC) for spectral/spatial coding with its structure of the corresponding system to implement in spectral amplitude coding optical code division multiple access (SAC-OCDMA) systems The novel code is derived from a one dimensional zero cross correlation (1D-ZCC) code using Pascal’s triangle rule. The analytical results prove that the proposed code has totally removed the multiple access interference (MAI), in addition the phase induced intensity noise (PIIN) influence is highly reduced due to the zero cross correlation (ZCC) property. Comparing with the recent developed two-dimensional codes like 2D multi diagonal (2D-MD), 2D dynamic cyclic shift (2D-DCS), 2D diluted perfect difference (2D-DPD) and 2D perfect difference (2D-PD) codes for the same code length. The results of simulation show that the suggested code improve the system capacity and increase the number of simultaneous users reaches 29 % and 64 % comparing to 2D-DPD and 2D-PD codes, respectively. As well, it supplies higher signal power and data bit rates whereas it saves effective source power around −0.81dBm for 2D-DCS and 2D-DPD codes and consumes minor light spectral width. The passage from 1D to 2D ameliorated 1.68 times the system capacity and saved around −4.27dBm$ - 4.27{\rm{ dBm}}$ the effective power for each user.

Hybrid wavelength division multiplexed (WDM)/Time division multiplexed (TDM) virtual passive optical networks (VPONs) are considered to provide cost efficient solutions for ever increasing bandwidth requirements of next generation optical access networks. With the development in technology effective bandwidth assignment has emerged as a major concern area. In this paper a novel heavy load optimized dynamic bandwidth allocation algorithm (HLO-DBA) is proposed for the hybrid WDM/TDM VPONs. Multi point control protocol of Ethernet passive optical network (EPON) is implemented for WDM/TDM VPONs subscribers. The excess bandwidth of lightly loaded subscribers is distributed among heavily loaded users through an efficient mechanism. The proposed technique effectively utilize the idle period between the last transmitted REPORT messages from previous transmission cycle (t-1) to the first GRANT message in the current cycle (t). Optical network units (ONUs) connecting the subscribers are scheduled in such a way so as to reduce the wastage of bandwidth. Performance evaluation of HLO-DBA in terms of quality of service (QOS) metrics like throughput and average delay is done to validate the optimization of the proposed mechanism.

Visible light communication (VLC), popularly known as light fidelity (Li-Fi), is a promising alternative to overcome the limitations of radio-wave communication. VLC is a green technology which uses light-emitting diode (LED) illumination to transmit data without needing fibre cables. VLC is applicable for both indoor and outdoor communication. In this study, we investigate the effect of sandstorms on VLC via simulating a vehicular-to-road VLC (V2LC) outdoor application. Sandstorms are a weather phenomenon which frequently occurs in the Arab peninsula and other parts of the world; in this context, researchers have not thus far addressed the effect of sand particles, which absorb and scatter light, on VLC. Our simulation is conducted using MATLAB software (Natick, Massachusetts, U.S.A.), and the results show that the effect of sandstorms on VLC is similar to that of fog and rain as investigated by other researchers. However, sandstorms are also different in terms of the nature of sandstorm particles, with different sizes and refraction indices when compared with rain and fog particles. We also find that high-density-clay sandstorms, among other types of storms, most severely affect VLC communication and limit the transmission range. Other low- and medium-density storms less severely affect VLC while exhibiting a relatively larger communication range.

This paper evaluates the signal-to-cross talk ratio (SXR) of cross talk induced by stimulated Raman scattering (SRS) in radio-over-fiber (RoF) systems based on wavelength-division multiplexing. The reported study has modeled the relations of SXR to modulation frequency, optical power, transmission length, and effective area of fiber for various values of the walk-off parameter. The summary of experimental results reveals that SXR decreases with increases in channel input power and transmission distance and increased with increases in fiber effective area and modulation frequency. Results showed that increasing the walk-off parameter from 13.6 to 81.6 ps/km increased the SXR by almost 6 dBm. Furthermore, various fibers, including standard single-mode fiber (SMF), Corning LEAF, and Alcatel TeraLight were tested for their capacity to mitigate SRS-induced cross talk. These tests demonstrated that standard SMF suppressed SRS cross talk effectively and offered values of SXR 3 dBm and 6 dBm higher than the values exhibited by Alcatel TeraLight and Corning LEAF, respectively.

The proposed traffic grooming methodology for long-reach-passive optical networks will decrease the latency in upstream. The scheduling and wavelength assignment for ethernet passive optical networks has been shown to perform much better in terms of delay. The dynamic traffic grooming algorithm based on intelligent water drop is proposed in which new depositions function has been introduced for efficient handling of bandwidth. Therefore, once equally distanced optical network units were scheduled on constant wavelengths, the void formation impact is reduced. The outcomes conjointly depict the result of the planned methodology on bandwidth utilization improvement and jitter by 1.46 and 408.66 µs improvements respectively, even overall latency is improved by 465.83 µs by value. These results depict the validity of the planned dynamic bandwidth allocation methodology for traffic grooming.