Volume 40, Issue 4 -

Next generation optical networks require large capacity communication networks for proper utilization of gain bandwidth of the networks. Optical amplifiers with wavelength division multiplexed (WDM) systems are the key technologies for the realization of these networks. In this paper, we have investigated the performance of the networks using different modulation techniques, such as return-to-zero (RZ), non-return-to-zero (NRZ) and duobinary. Attempts were taken to design 8 channels, 10 Gbps WDM network at channel spacing of 0.8 nm. An innovative model with EDFA-Raman amplifier is designed to examine the performance of the different modulation schemes. From the results, it is found that NRZ configuration gives maximum output power and good quality of communication as compared to other modulation schemes. Further, it is seen that with increase in channel dispersion from 2 to 4 ps/nm/km, the quality of the signal started decreasing.

Different fiber amplifiers such as semiconductor optical amplifier, erbium-doped fiber amplifier and erbium ytterbium-co-doped fiber amplifier (EYCDFA) are investigated for 16×40 GB/s wavelength division multiplexing system. Various performance parameters including Q-factor, bit error rate, jitter, eye opening and eye closure are observed and analyzed. It is reported that EYCDFA is a better choice among the tested amplifiers. The proposed system is also investigated in terms of transmission distance.

Analysis of proposed 400×10 Gbps super dense wavelength division multiplexing (SD-WDM) system has been evaluated in term of crosstalk and optical signal to crosstalk ratio (OSCR). Amplification is carried out using RAMAN-EDFA hybrid optical amplifier (HOA) for the transmission of 300 km. The pump power of 550 mW at 1520 nm and 580 mW at 1530 nm are set to RAMAN and EDFA optical amplifier respectively. Further, the power level of 0 dBm with channel spacing of 100 GHz has shown the remarkable outcome of controlling the fiber nonlinearity to maintain the best rating optical communication for long haul distance.

Thulium-doped fiber amplifier is a very proficient broadband fiber amplifier in S-band. Silica-based TDFA is a popular choice due to some of its evident features such as non-toxic nature, easy splicing and simple assembling. In this work, we have simulated and optimized various TDFA’s physical and operational parameters in order to obtain required gain spectra at different channel spacings. Further, a comparative study has been carried out between single and dual-pumped TDFAs. By using dual pumping scheme (1040 nm and 1000 nm) as fundamental source of excitation, maximum gain of 23.31 dB has been achieved at 1468.8 nm in region spanning 1400 nm to 1470 nm wavelengths with noise figure of 3.72 dB.

At present, photonic crystals (PhCs) are used to design various combinational and sequential circuits. In this paper, an all-optical one-bit magnitude comparator is proposed using PhC waveguide without using nonlinear material. It is based on beam interference principle, using T-shaped lattice with silicon dielectric rods in air background. It is demonstrated through finite-difference time-domain simulation and verified numerically using MATLAB simulation. The size of PhC lattice structure can be as small as 19.167 a ×19.167 a , where ‘ a ’ is the lattice constant of the PhC.

In this paper, we have proposed and analyzed a novel cost-effective ultradense wavelength division multiplexed (UDWDM) passive optical network (PON) which uses phase modulation (PM) of the optical carriers in the optical line terminal (OLT) in order to achieve inherent noise immunity in the network. In the demodulation of the optical PM signal at the optical network unit (ONU), we have proposed to use a simple injection–locked Fabry–Perot (FP) laser diode (LD) for achieving PM to intensity modulation (IM) converter which is followed by a photodiode to recover the specific channel information. A detailed analysis of PM–IM conversion in an injection–locked FPLD has been carried out and the viability of the proposed scheme has been established. The proposed UDWDM–PON which is a broadband access network is cost-effective and long reach.

In this paper, we proposed optical filter based on two-dimensional photonic crystal elliptical channel for wavelength division multiplexing. We employed ring resonator with ellipse shaped core in proposed structure. The resonance wavelength of the ring resonators depends on two parameters: refractive index and radius of dielectric rods. We investigate the physical parameters governing the filter performance. Our results show that the transmission efficiency is 100 % due to nearly zero reflection and loss in channel. Band width of 4 nm and quality factor of 389 is obtained for filter. Also, the total footprint of proposed structure is 230.4 µm 2 which makes it suitable for all optical integrated circuits.

In the contemporary world there is enormous hike in communication engineering applications, outcome with massive heat dissipation from the processing nodes. So energy efficient information network is one of paramount issue nowadays. For that optical reversible computing could be a landmark with base as optical logic gate. Reduction in power dissipation, consumption could be accomplished through a blend of reversible and irreversible optical processing and the nodes may recuperate the data. Accordingly, in this article two designs with semiconductor optical amplifier, used as Mach–Zehnder interferometer based all optical reversible Feynman gate, irreversible AND logic gate within a single photonic circuit has been proposed. The output waveforms for AND logic operation, Feynman logic the P (data output identical to input), Q (A ⊕ B) has been verified at 100 Gbps data rate. The designs have been evaluated on the basis of key parameter extinction ratio factor. Numerical simulations have inferred excellent ER performance with design-2(ER>13 dB) in contrast to design-1(ER as 10.2 dB). Performance evaluations for significant deign parameters as pump current, length, width, carrier transport, confine and current injection factor yielded excellent performance. This evaluation could be an assist toward design of contemporary optical networks.

In this work, we have developed an analytical model of an actively Q-switched Ytterbium-doped fiber laser by using two coupled cavities with amplifying fibers in Mach–Zehnder interferometer configuration. This oscillator system provides high peak power and high energy nanosecond pulse. The pulse energy is almost twice the energy of an individual fiber laser with a combining efficiency goes up 99%. This concept brings some novel perspectives for scaling the high energy and high peak power of nanosecond pulse fiber laser.

A photonic crystal fiber in square lattice architecture is numerically investigated and proposed for broadband dispersion compensation in optical transmission system. Simulation results reveal that it is possible to obtain an ultra-high negative dispersion of about −571.7 to −1889.7 (ps/nm.km) in the wavelength range of 1340 nm to 1640 nm. Experimentally it is demonstrated that the design fiber covers a high birefringence of order 4.74×10 ‒3 at the wavelength of 1550 nm. Here, numerical investigation of guiding properties and geometrical properties of the proposed PCF are conducted using the finite element method (FEM) with perfectly match layers. Moreover, it is established more firmly that the proposed fiber successfully compensates the chromatic dispersion of standard single mode in entire band of interest. Our result is attractive due to successfully achieve ultra-high negative dispersion that is more promisor than the prior best results.

In this article, a low loss circular photonic crystal fiber (C-PCF) has been suggested as Terahertz (THz) waveguide. Both the core and cladding vicinity of the suggested PCF are constituted by circular-shaped air holes. The optical properties such as effective material loss, effective area, core power fraction and V-parameter have numerically been probed by utilizing full vectorial finite element method (FEM) with perfectly matched layers (FMLs) boundary condition. The reported PCF reveals low absorption loss and large effective area of 0.04 cm −1 and 2.80×10 −07  m 2 respectively at 1 THz operating frequency. In addition, the core power fraction of the fiber is about 50.83 % at the same activation frequency. The V-parameter shows that the proposed PCF acts as a single mode over 0.70 to 1.15 THz frequency. So, the reported PCF offers the best performance in long distance communication applications.

The effect of nano-hybrid sensor based on a wavelength division multiplexed technique (WDM) is studied using photonics crystal fiber and fiber Bragg grating (FBG). The full duplex scheme is used in the proposed system to receive and transmit the data at the same time for fast processing. The finite difference time domain photonics simulation software (FDTD) is used to observed variation in reflection and the transmission power spectra of the photonic gratings. Using line defects we created two linear waveguides, further, it is used as an optical sensor. From this work, we recommend that the proposed system can be used as in communication field for data transmission and also used in sensing application to sense the property and deformation of the object.

We have proposed and demonstrated a novel architecture to implement in Coarse Wavelength-Division-Multiplexing (CWDM) technologies to give integrated broadband services for residential complex use system. For keeping the speed of 1000 Mbps at the bus IFs, CWDM technology is employed, and eight wavelengths are allocated to eight bus IFs, respectively. We also have evaluated characteristics of the transmission by calculated and measured the throughputs. The optical IP network can be easy in-service by adjusting the number of wavelengths and optical transceivers. We believe this novel scheme can be applied for future broadband network.

Free space optical (FSO) communication systems are gaining high popularity from the last decade due to its various advantages such as no license spectrum, low-cost implementation etc. In this work, 160 Gbps data is transmitted over 8 km FSO link by adopting alternate mark inversion (AMI), wavelength division multiplexing (WDM) and polarization division multiplexing (PDM) schemes. The results are reported in terms of Q factor, bit error rate, signal to noise ratio, total received power and eye diagrams.

In this paper, the transmission performance of 64×10 Gbps wavelength division multiplexing system using semiconductor optical amplifier (SOA) with 0.4nm channel spacing has been demonstrated with different modulation data formats. The suitability of various data formats like nonreturn to zero rectangular (NRZ-rectangular), nonreturn to zero raised cosine, return to zero raised cosine, return to zero rectangular, return to zero supergaussian and return to zero soliton for an optical transmission link at ‒40dBm signal input power is evaluated. The results have been carried out by evaluating the value of quality factor, bit error rate (BER), eye closure and received optical power. It is found that using NRZ-rectangular data format, the signal can travel up to a transmission length of 260 km with acceptable BER (1.10e-09) and Q-factor (15.0 dB), respectively.

Free Space Optics (FSO) is a wireless optical communication technology which depends on propagation of optical beam through air. FSO communication system provides secure communication link, cost-effective solution and license-free operation. In this paper, the FSO communication link has been analysed in turbulent atmosphere using homotopy perturbation method (HPM). We have designed a FSO system operating at an optical wavelength of 850 nm with a signal power of 4 dBm having a link range of 2 km between transmitter and receiver unit. It has been observed that in atmospheric turbulence high performance FSO link is achieved by increasing the aperture diameter of receiver telescope.

An unprecedented demand for connecting physical objects with the internet expedites the realization of internet of things, thus creating new challenges to explore new spectrums which are suitable for communication. Visible light communication (VLC) is one promising candidate not only to remove the spectrum crunch issues but also to offer virtually unlimited, unregulated spectrum. This paper discusses how VLC can help solving spectrum crunch, non-availability issues of radio frequency spectrum and how readily available spectrum of VLC can be utilized to cope up with the bandwidth requirements of next-generation networks. Furthermore, this paper also lists the technological innovations in the area of VLC from early days till present and its possible applications in various domains.

In this paper, comparative analysis of code performance of dissimilar optical 2-D codes from Optical Orthogonal code family has been studied. Optical 2-D codes considered from OOC family are ( n,w ,1,2) OOC, SPS/OOC, OCFHC/OOC, EPC/OCS and VWOOC. By utilizing hard limiting error probability (HEP) equations and combinatorial method, code performance of each considered code is evaluated in detail. On the basis of detailed comparative performance analysis, EPC/OCS is concluded as best performing codes among all other optical codes under consideration. EPC/OCS possesses much better correlation properties, along with lower hit probability values which are responsible for its supremacy in performance characteristics to the other OOCs considered.

Optical code division multiple access (OCDMA) system provides highly secured transmission in addition to its capabilities to support asynchronous transmission and soft blocking. Two-dimensional OCDMA codes are chosen in this paper due to their high cardinality, good spectral efficiency and flexibility in their construction methods against direct sequence codes. This paper focuses on study of impact of multiple access interference (MAI) at high data rates for 2-D prime codesbased OCDMA system. It is shown that how the change in number of simultaneous users affects the transmission quality. Further, performance of the system is analysed in terms of bit error rate, received electrical power and eye openings. In addition, this paper also shows a comparative analysis of 2-D codes-based OCDMA system and wavelength division multiple access (WDMA) system in order to justify the improved performance of the proposed system. It is observed that the performance of 2-D OCDMA system is much better than WDMA system in terms of quality as well as security.

Obtaining analytically closed-form expression for bit error rate (BER) of an optical wireless communication (OWC) system under weak atmospheric turbulence is extremely difficult and intractable. In this paper, a simple closed-form approximate expression for average BER of OWC system under weak turbulence condition is obtained using point estimate method. The proposed expression is used to compute the BER for on-off keying (OOK) and sub carrier intensity modulated (SIM) binary phase shift keying (BPSK) modulation schemes. Results obtained using proposed expression are compared with those obtained using Gauss-Hermite quadrature approximation and Monte-Carlo simulations.