Volume 43, Issue 4

This paper highlights a proposed optimized gain flatness technique for nonuniform gain spectrum of the erbium-doped fiber amplifier (EDFA) by introduction of long period fiber gratings (LPFG). In this analysis, EDFA gain spectrum has been evaluated between 1525 and 1600 nm with −20 dBm input signal power. Attenuation peaks of LPFG are optimized with a grating period of 240 µm and grating length of 30000 µm in the wavelength range of 1.1–1.8 μm, to compensate the peak gain of EDFA. Results have shown that EDFA peak gain of 35.94 dB is achieved at 1532.89 nm wavelength. This 35.94 dB peak gain is flattened up to 2.65 dB using long period fiber gratings. Also, less than ±0.3 dB gain flatness is achieved between 1528 and 1560 nm wavelength. The proposed less complex technique can be used to modify the grating parameters during fabrication in order to produce the loss peak at desired wavelength, which is efficient to flatten EDFA gain peak.

This paper studies the problem of data access at the receiver with large bit error rate and low quality factor. Due to this issue the information got inaccurately at the receiver side, the data should have high quality factor and low bit error rate to be simple of identification at the receiver when using the gates. The nonlinear properties of the semiconductor optical amplifier are utilized to accomplish the Boolean variable based math work, in which AND, NAND, and OR gates potentially used to endorse the Boolean function. Through blend this gates together any Boolean function can be accomplished and utilized to perform optical signal processing. The quality factor and BER are measured by utilizing the eye diagram analyzer, the state of the output bit and also shaped by the oscilloscope visualizer in optiwave simulation program. These models can be used for wavelength converter, header recognition, parity checking, binary addition, packet-header modification, encoding and encryption with pattern matching, and data encryption with high speed and high quality factor.

Free space optical (FSO) communication is coming up as an attractive alternative to solve the connectivity hindrances. It is an efficient optical technology having several advantages such as narrow beam size, unlicensed spectrum, high reliability, huge modulation bandwidth, low power and higher grade of security. In this paper, we have proposed an FSO communication system model using EDFA-EDFA hybrid optical amplifier (HOA) configuration which provides enhanced reach and higher data rate. For transmitting channel, weak turbulence approximation which exhibits log-normal statistics is considered. Q -factor, bit error rate (BER) and Eye diagram have been taken as performance metrics. From simulative results, it has been observed that the designed FSO communication system efficiently enhances the transmission reach from 1,000 to 5,000 m along with a substantial improvement in Q -factor and BER.

Photonic crystals (PCs) have an excellent ability to confine and control the manipulation of light. PCs are periodic or aperiodic arrangement of dielectric, metallo dielectric or super conductor micro and nanostructure materials. The periodicity of refractive index distribution in one, two and three dimensions affects the propagation of electromagnetic waves inside the PC structure. As a result of periodicity, photonic band gap (PBG) exists in a specific wavelength of PC structure and reflects the beam of light through it. This is an active part to design optical devices with a specified wavelength range. The PBG of periodic and aperiodic structures is calculated by plane wave expansion method. The wavelength division multiplexing (WDM) is an emerging technology in optical field. The multiplexer and demultiplexer are playing a prominent role for transmission and reception of light signals in WDM systems. This paper investigates and enumerates the two-dimensional (2D) PC square lattice structure-based WDM demultiplexers using quasi-square ring resonator (QSRR). The periodic array of inner rods located inside the QSRR whose shapes and refractive index justify the resonant wavelength of the channels. The channels are dropped at output ports with different resonant wavelengths by altering the size and refractive index of cavity. Typically, the resonant wavelength of the channel is shifted to higher wavelength while increasing the dielectric strength of the QSRR. The dielectric strength of the QSRR is altered by varying the inner rod radius which reflects the size of the air gap. The demultiplexer is composed of bus waveguide, scatterer rod, and reflector rod whose dimensions are also responsible to enhance or alter the performance of the systems. The finite difference time domain method is utilized to analyse the functional parameters of the structure such as the resonant wavelength, transmission efficiency, Q factor, spectral width, channel spacing and crosstalk. The impact of performance parameters is investigated through different shape of inner core and refractive index of QSRR. The observed resonant wavelength of the channels (1,525–1,610 nm) of the demultiplexers is falling under WDM systems and overall size is minimized to 434.16 μm 2 . The average channel spacing is about 0.75 nm, spectral width is 0.76 nm, Q factor is 2,036 and crosstalk between the channels is −30 dB. The significance of the attempt is to reduce the crosstalk which is attained by grouping odd and even numbers of channels separately. Finally, four-channel demultiplexer is designed by altering the refractive index of the inner rods (i. e. inner core) linearly and the performance parameters are investigated. Then, the point-to-point network is designed to incorporate and evaluate the performance of the demultiplexer. The observed maximum travelling distance, Bit Error Rate (BER) and receiver sensitivity of the network are 85 km, 10 −9 and −16 dBm, respectively. The device could be incorporated in photonic integrated circuits for dense WDM applications.

As energy efficiency is one of the prominent issues in the today’s era. Reversible computing may serve as a critical step toward this paramount issue. Optical reversible computing is one of the tactics to serve this aspiration. In this paper, an optical reversible hybrid adder-subtractor device delineated with the help of electro-optic effect inside lithium-niobate based Mach-Zehnder interferometer (MZI) for WDM applications. The proposed device in this work is combinational circuits and can be used as an adder as well as subtractor in advance applications. The perception is established with the help of simulation results of beam propagation method (BPM) and mathematically proven with MATLAB simulation results.

In this paper, we propose a design of octagonal photonic crystal fiber with relevant parameters such as effective mode index, propagation constant, second-order dispersion and field distribution of fundamental mode (LP 01 ). The measured parameters can be applied for generating supercontinuum, and also this model is used especially for generating vortex modes and OAM modes in space division multiplexing (SDM) applications. Highly negative dispersion is achieved at −800 ps/nm.km at wavelength of 1.1 μm, and second-order dispersion profile leads to study about the nonlinearity as well as broadband spectrum of the proposed model.

This paper has presented the basic infrastructure of different multilayer graded index fiber profiles design. The optimum graded refractive index fiber profile design for the control of total Losses and dispersion effects are considered. The trade-off between different refractive index fiber profiles is realized in order to achieve loss and dispersion effects management. It is evident that the proposed first optical fiber has presented lower dispersion and splice loss than other proposed fibers. As well as the proposed third optical fiber outlines lower effective mode field diameter and micro bending loss than other proposed fibers. Dominant mode, cutoff wavelength and international telecommunication union-telecommunication (ITU-T) values for each fiber are examined based on finite difference method.

The physical layer of an optical network is vulnerable towards various types of security threats such as physical infrastructure attacks and eavesdropping, where the security item requires more attention in front of the dramatically grows in network capacity. In this paper, authors propose a comparison in performance of zero correlation zone-Optical Code Division Multiple Access based on different confidentiality mechanisms implemented using existing optical logic components such as line selectors, wavelength convertors and XOR gates. The performance of the proposed designs in terms of log of the bit error rate (BER) as function of the received power was evaluated through OptiSystem software simulation. The achieved results demonstrate that design 3 is the best confidentiality solution in terms of received power, BER performance and architecture complexity.

Fiber to the home (FTTH) passive optical network is one of the cost effective and effortlessly planning systems in the current era of communication systems. However, one of the substantial limitations of this optical communication network is the monitoring operation. It is essential to locate the fault branch in the network in order to take the required action to overcome the problem. Unfortunately, since the network is all passive, it is necessary to introduce a technique that should be passive and has the capacity to locate the fault location inside the network. In this paper, a methodology to localize the fault line was introduced, where a combination of Fiber Bragg Gratings was suggested, using this approach, the fault location can be easily determined among 36-branch, distributed in eight groups. Simulation results show that the broken line can be determined through monitoring the reflected signals from all the branches in the Central Office without paying any power to locate the leakage. In other words, it is easy to recognize the fault location by monitoring the power of the reflected signals, where after comprehensive simulations and power calculations, it was possible to put a threshold for that reflected power, hence, the fault branch, for any reason, may reflect power of less than that threshold, otherwise, the branch is not considered as broken.

The optical fiber communication offers a huge bandwidth for data transmission at higher data rates but to increase the throughput for long-haul networks, metro data links, and data centers, additional fiber is required which is not economical. For effective reception of signals at the receiver, the photo detector in optical communication requires higher efficiency, lower noise, ultrafast response and optimum received signal strength. The inherent dispersion and nonlinear impairments in optical fiber communication system can be overcome by using the Fiber Bragg Grating (FBG) which is a Dispersion Compensating Module. FBG helps to improve the long-haul transmission by providing an efficient system performance. This paper presents a detailed review of FBG and photo detectors and their use in an Optical communication system. This paper will help the researchers to find useful material at a single platform.

In this paper, two models of fiber-to-the-x (FTTx) networks are provided, one of hybrid dense wavelength division multiplexing/coarse wavelength division multiplexing (DWDM/CWDM) with high subscriber’s allocated bandwidth, and the other of hybrid ultra-dense wavelength division multiplexing/coarse wavelength division multiplexing (UDWDM/CWDM) with high network capacity. The effect of the fiber chromatic dispersion on the signal quality was demonstrated. The behavior of the network with respect to the changing of the DWDM channel spacing and the relation between the channel spacing and the system bit rate was discussed.

This study has presented the complete comparison non return to zero (NRZ) and return to zero (RZ) modulation techniques for upgrading long haul optical wireless communication systems. Electrical signal to noise ratio is measured. Q-ranges factor are measured at the receiver side for different transmission distance from 500 to 1000  km. As well as the performance parameters of optical wireless communication systems are estimated at different transmission data rates with possible maximum transmission distance. NRZ modulation technique has outlined better performance than RZ modulation technique for upgrading optical wireless communication systems.

This paper has deeply simulated the different configurations of pre, post, and symmetric dispersion compensation-based dispersion compensated fiber (DCF), Gaussian optic filter (GOF), and fiber Bragg grating. Output power, signal quality factor, and signal gain are the performance parameters in this study for the complete comparison for the proposed techniques for dispersion compensation. It is observed that FBG has presented the best performance parameters optimization in compared to other compensation techniques for different configurations of compensation. The FBG dispersion compensation technique is the key solution for dispersion compensation in compared with other compensation techniques that are comparatively as in previous section. It is observed that the FBG is the best dispersion compensation technique and change its location, and length, apodization, and chirp functions, to obtain the best performance of FBG and give the best quality factor, output power, and gain, FBG can be employed in different categories such as post compensation, pre compensation, and symmetric compensation with different FBG lengths, apodization, and chirp functions.

The study shows the basic interaction between different optical sources and optical detectors for high-speed optical communication networks. Optical sources that are namely continuous wave (CW) laser, laser rate equations as well as the vertical cavity surface emitting laser (VCSEL). The utilized optical modulators are indicated as Mach Zehnder modulator (MZM) as well as the Electro-absorption modulator (EAM). The data rate available 40 Gb/s for propagation length ranges from 10 km to 50 km. It is observed that the interaction between CW laser/MZM or CW laser/EAM has presented better performance than other combinations. In order to measure the system performances, many interesting parameters have been investigated. These can be including the electrical received power, highest signal quality factor, Optical signal per noise ratio as well as the lowest data error rates.

The study presents the basic apodization and chirp functions based fiber Bragg grating (FBG) for upgrading optical fiber performance efficiency. Variations of apodization and chirp functions are studied with grating length variations. Optical power after FBG, signal to noise ratio, maximum Q -factor, and output power are measured in the presence of the chirp functions. Gaussian apodization function has outlined good performance than other proposed apodization functions. As well as linear chirp function is better performance than other chirp functions. The optical system performance tested with/without chirp effects with high bit rates.

Radio over fiber (RoF) is an empowering technology for the next-generation wireless networks including fifth generation cloud radio access networks. In this paper, we propose a new fronthaul interface which has been demonstrated for a 20-MHz LTE signal having 64-Quadrature amplitude modulation (QAM) modulation over 50 km of standard single-mode fiber. The proposed methodology potentially reduces the overall bandwidth requirement of the link. The performance analysis has been demonstrated for conventional analog RoF (A-RoF) and proposed digital RoF (D-RoF). As a figure of merit, the performance evaluation of the two architectures is reported by analyzing error vector magnitude (EVM), signal-to-noise ratio and eye-opening penalty. It is shown that digital optical links can mitigate the impairments present in A-RoF links and can support the transmission up to 50 km. Moreover, it is shown that efficient D-RoF links can be obtained with a relatively low amount of analog-to–digital-converter resolution bits. For the D-RoF link, the EVM was measured to be less than 2 % at 50 km. This is within the LTE specifications, proving it as a cost and power effective solution for next-generation wireless networks.