Volume 44, Issue 1

A comprehensive and integrated exact analytical formalism is presented for erbium-doped fiber amplifiers and lasers (EDFALs) in one single configuration based on solutions of a system of rate and propagation equations represented by a homogenously broadened four band transition scheme while incorporating amplified spontaneous emission and excited state absorption effects. The formalism, under steady-state conditions, concurrently provides considerable insight into physical characteristics underlying phenomena pertinent to EDFALs and allows precise evaluation of behavior exhibited by EDFALs through a judicious selection of pump intensity and fiber length in standard eye-safe low-erbium concentration uniformly doped mono-mode silica glass fibers in co- and counter- propagating directions appropriate to signal, pump and ASE regimes.

This study has presented the nonlinear medium such as passive nonlinear medium like highly nonlinear fiber (HNLF) and active nonlinear medium like SOA. The FWM effects have ended up plainly huge at high optical power levels and have become even more meaningful when the capacity of the optical transmission line is increased, which has been reached through decreasing the channel separations. Also, anatomy has been done to analyze the performance of FWM when unequal channel spacing is considered. The outcomes indicate that when unequal channel spacing is used, the power levels of the beat frequency generated due to FWM effect in WDM system was increased to large values, so the performance of the wavelength division multiplexing (WDM) system is not enhanced, on the other hand when equal channel separations are used, and at the same bandwidth required to transmit 4 input channels the quality of receiving signal is greater than the system used unequal channel separation. This means that in the WDM system equal channels separation is more efficient than unequal channels separation-based SOA. The simulation is done using 4 channel wave division multiplexing signals at a rate of 10 Gb/s.

The study presents the average power model of optical Raman fiber amplifiers based on frequency spacing and amplifier section stage optimization technique. The amplifier section stage is taken from 25 to 75 km and frequency spacing is taken from 0.2 up to 1 nm. Input/output Raman signal variations are measured versus operating wavelength range and bit time period variations. The suitable input signal power for the optical transmitter is chosen to be −10 dBm and return to zero modulation code is applied with an available data rate of 10 Gb/s. Sixty-four channels are multiplexed to benefit a multi-number of users with suitable power levels.

Nonlinear photonic crystal ring resonators are suitable mechanisms that can be used for designing optical logic gates and digital structures. In this paper, we designed two nonlinear resonant rings by adding doped glass rods inside the photonic crystal ring resonator. An optical half adder was designed using these nonlinear photonic crystal ring resonators. We used plane wave expansion and finite difference time domain methods to simulate our optical half adder. The simulations show that when one of the input ports is ON, the normalized optical power at the S is about 90 %. The time delay in this case is 7 ps. Also when both the input ports are ON, the normalized optical power at the C is about 155 %. The time delay in this case is 8 ps.

Optics has strong potentiality in data processing. Here, quantum Fredkin gate is implemented with the help of switching property of optical nonlinear material and polarization-based encoding and decoding technique of optical signal. The gate is very much useful for quantum computing and communications.

This study has presented spatial continuous wave laser and spatiotemporal vertical cavity surface emitting laser (VCSEL) for high speed long haul optical wireless communication channels. Possible data rates range from 40 Gb/s to 250 Gb/s over propagation distance ranges from 500 km to 2500 km. The optical wireless communication (OWC) system performance is tested through the measurement of maximum Q-factor, minimum bit error rate (BER) and signal to noise ratio (SNR). It is observed that spatiotemporal VCSEL has presented better performance than CW laser in the OWC system, especially for long haul transmission applications. It is observed that SNR improvement ratio ranges from 8.15 % to 19 % by using spatiotemporal VCSEL than CW laser for bit rate of 40 Gb/s over propagation distance ranges from 500 km to 2500 km. Max. Q-factor improvement ratio ranges from 4.62 % to 13.71 % by using spatiotemporal VCSEL than CW laser for data rate of 40 Gb/s over propagation distance ranges from 500 km to 2500 km. So it is clear that spatiotemporal VCSEL is more suitable for long haul OWC applications than other optical sources.

This research focuses on the side-polished Single-Mode Optical Fibers (SMOF) as refractive index (RI) sensor utilizing properties of Surface Plasmon Resonance. The SMOF with cladding stripped off shows a D-shaped optical fiber with high sensitivity functionalization. Here we show silver protected by graphene oxide (GO) as viable candidates. A few layers of GO on top of silver thin layer were applied as a material to overcome silver coating degradation process. This silver/GO sensor was characterized using various RIs of analyte likely deionized water and alcohol solutions. Sensor with GO has shown fast response and high sensitivity in respect of RI, where sensitivity increases in range from 1.30 to 1.34 RIU (refractive index unit). This device shows highest sensitivity of up to 833.33 nm/ RIU. The polishing process using SMOF stops at few microns above the core of the fiber with the drop of output power fixed to be 1 dB as an indication to standardize the amount of cladding been removed. The thickness of 30 nm Ag was deposited using electron beam evaporation method on D-shaped optical fiber with subsequent protected layer of GO in solutions form. The use of COMSOL Multiphysics has also been carried out to observe numerical findings. The response of the GO has shown a sensitivity improvement which proves new promising approaches for the newly developed sensors.

This study outlines the high-speed light sources in high-speed passive optical local area communication networks. Directly modulated laser measured is selected as a light source for data rate transfer of 40 Gb/s for propagation range up to 20 km. Optical output power after fiber-optic cable is measured. Signal power amplitude, Q -factor, and data error rates after the receive side are also measured. Hybrid optical amplifier, optical filters, and electrical filters are used for upgrading the network performance operation efficiency. The study assured that the optical communication network can be extended to 20 km distance with data rates of 40 Gb/s with achieving maximum Q -factor of 14.98 and minimum data rates of 3.55 ×10 –51 .

Cloud computing services and real-time Internet applications have spawned a large variety of potential requirements for quality of service (QoS), especially the latency and connection setup time. However, with the optical networks develop toward to larger scale, wider coverage and more users access, conventional resource reservation protocol traffic engineering (RSVP-TE) signal hop by hop transmission scheme cannot meet the requirements of these new applications for real-time dynamic services and fast restoration with long propagation delays. This paper proposes a novel RSVP-TE bilateral-recursive region re-routing crankback mechanism (BRCB) base on distributed path computation element (PCE) for generalized multiprotocol label switching (GMPLS) optical networks. In this mechanism, the backtracking nodes re-route and update the region routing paths which bypass the crankback and re-routing failure nodes when crankback occurs. It not only reduces the influencing factors of the scale of network, signaling crankback position and frequency to path connection setup time, but also avoids the backtracking of teardown messages.

A visible light communication (VLC) provides potential and effective communication paradigm due to the demand of high data-rate applications. VLC networks, consisting of multiple light emitting diodes (LEDs) and it provides the low-cost high data-rate transmission to multiple users simultaneously in indoor environments. VLC has been recently introduced as a secure directional data transmission in vehicle to vehicle to provide an intelligent vehicle control system. However, the performance of this system is mostly affected by the collision of data transmission between different users. In this paper, we introduce an optimal visible light communication (OVLC) network that allows vehicles which have provides collision aware data transmission to improve the chance of transmitting information successively according to the network condition. Firstly, the next forwarding node is selected by the chaotic fish swarm optimization (CFSO) algorithm with the help of vehicle information’s such as intensity of light, the distance and speed of neighboring vehicles. The second contribution is to illustrate the congestion control (CC) system for avoiding extra time due to the control packets exchange process. The optimal result is then forward to the source vehicle equipped device, which helps the driver to make a healthy to control vehicle and efficiently avoid or prevent road accidents under different circumstances. The results show that the proposed OVLC network performs very efficient than existing network in terms of quality metrics, such as throughput, delay, packet loss rate, energy consumption and fairness index.

Underwater optical wireless communications (UOWC) have recently received considerable attention for both research and commercial use because of their facility to provide a much higher data rate than the traditional acoustic method within comparatively small distances. Many potential application of UWOC systems have been proposed for environmental monitoring, exploration, disaster precaution, and military operations. In all the above mentioned research works, high absorption and scattering of optical transmission in the water limits the benefits of UOWC systems to only few meters. In order to overcome these technical challenges, several new system design approaches proposed. This work is done in salt water. Salt water cannot be used for drinking because it causes dehydration. This paper analysis the performance of the system using different water samples like salt water, turbid water, normal water, etc.

Free space optical communication systems (FSO’s) have surfaced as admired means of communication in the past few years. High speed of operation, low bandwidth requirements and system reliability are the major factors responsible for their wide range of applications. These communication systems use air as a medium of transmission. Since there is no component like fiber or cable, but air is only medium, the variations in atmospheric conditions play a vital role in performance of these networks. The reason behind is that the conditions like presence of humidity, haze, snowfall, rain, dust or smoke changes the attenuation coefficient of medium. The raised attenuation levels results in increased losses and need to be carefully monitored. The present work analyzes the influence of rain on the performance of FSO network in terms of quality of transmission. The paper discusses the impact of rainfall on attenuation coefficient of air. Then impact of this attenuation on network transmission is presented in terms of BER and Q -factor. In order to demonstrate the impact, BER and Q -value is calculated for 10 Gbps FSO link for clear weather and rainfall conditions.

In this paper, Li-Fi system based on orthogonal frequency division multiplexing (Li-Fi-OFDM) is presented. In these systems, light-emitting diodes (LEDs) are used to send information data using intensity modulation. LEDs have a limited dynamic range and the voltage-current characteristic shows a nonlinear behavior. Li-Fi-OFDM signal is used to drive these transmitter LEDs. However, LEDs chip overheating and nonlinear distortions occur, due to high peak-to-average power ratio (PAPR) of the OFDM signal. The proposed approach develops a new PAPR reduction method of OFDM in Li-Fi systems based on time-domain windowing techniques. Several windows such as rectangular, Hanning and raised cosine methods have been applied to the OFDM time-domain signal in order to reduce its PAPR while maintain acceptable bit error rate (BER) performance at receiver side. The simulation results of the work have shown the advantages of the offered method; the proposed scheme achieves a significant PAPR reduction compare to the unwindowed signals. Our proposed system also slightly improves the BER performance for all windowing methods employed.

The work has simulated different order Gaussian pulses effects on the high data rate fiber communication channel and optical receiver sensitivity with/without self-phase modulation (SPM). The light signal per noise ratio, and total dispersion coefficient after optical fiber communication channel are measured at different order Gaussian pulses. Receiver sensitivity and maximum Q -factor are also measured for an optical receiver at high transmission data rates at different order Gaussian pulses. As well as Soliton peak power is measured for different transmission data rates with/without SPM effects. It is observed that the system performance is degraded over 100 Gb/s data transmission and 50 km fiber distance especially in the presence of SPM effects. It is evident that the system performance efficiency is degraded with high order Gaussian pulses. It is recommended to use first-order Gaussian pulse for upgrade optical communication system performance efficiency.

Orthogonal Frequency Division Multiplexing (OFDM) is one of the popular techniques used for 4 G, 5 G and backbone optical communication networks to meet the large data transfer requirement applications. Optical Communication model based on Coherent Optical OFDM (CO-OFDM) using 4-Quadrature Amplitude Modulation (QAM), 16-QAM and 64-QAM has been evaluated by different researchers. To understand and evaluate the effects of polarization, we have proposed an Optical Communication model with Polarization Division Multiplexing (PDM). The proposed CO-OFDM PDM system has been evaluated for different link lengths of 50, 100 and 150 km at varying data rates of 10, 20 and 30 Gbps. The performance of the designed link has been evaluated in terms of Q -factor, Bit Error Rate (BER), Optical Spectrum and constellation diagram. The results clearly exhibit that the Q -factor, BER and constellations are superior when PDM is incorporated with the CO-OFDM link using X -QAM.

This study has deeply investigated the basic equations analysis of dispersion and loss in photonic crystal fibers (PCF) within the operating wavelengths of 850, 1,300, and 1,550 nm. The confinement loss, effective refractive index, and effective cross-section area of PCF are also studied. The variations of total dispersion and losses against hole diameter and distance between holes variations in PCF are clarified. Confinement loss, effective refractive index, and effective cross-section area variations for PCF are sketches with the variations of the operating wavelength.

In the present day world, the satellite technology is recording high growth rate on day to day basis through which the part played by optical wireless communication via satellite has been found to be playing an important role. The system has been evaluated by means of two methods. The first one being the communication system using 48 transponders in the satellite by means of Optisystem 15.2 software. The second one attributes to the concept of Satellite to Satellite Optical Wireless Communication (SSOWC) wherein 48 transponders are used by means of Optisystem 15.2 software. In this, the factors realized are Q -factor, bit error rate, effective noise band width and noise power. These factors were verified and analyzed to make use of satellite optical wireless communication of the respective transponder performance.