Volume 46, Issue 1

In line fiber Mach–Zehnder inferometer (MZI) pulse compression was designed three different lengths of single mode-polarization maintaining fiber with (8, 16, 24) cm after splicing them between two single mode fibers (SMF-28e) with (23 and 13) cm and applying different weights on splicing region and the cross sectional area of SM-PM fiber, the designed performance of the in line fiber compressor system was studies in terms of compressor factor. Two minima pulse compression factor were obtained, one is 1.13 with FWHM 251.584 pm, centered wavelength 1547.394 nm, 52 cm interferometer length and 5 g was applied on the micro-cavity splicing region, and the second is equal 1.10 with FWHM 259.730 pm, centered wavelength 1547.120 pm and, 68 cm interferometer length and 10 g was applied on the cross sectional area of the second PMFs, in the case of single and cascaded interferometers, respectively. The input of the all interferometers was pulsed laser source with peak power 1.2297 mW, 286 pm spatial FWHM, 10 ns temporal FWHM, 3 kHz repetition rate and centered at 1546.7 nm.

Capacity enhancement in satellite wireless optical systems (SWOS) systems is an ultimate task to accomplish due to ever-increasing internet services and it can be achieved by incorporating polarization division multiplexed (PDM) quadrature phase shift keying (PDM-QPSK). Herein, 2λ × 160 Gbps intersatellite optical wireless communication (IsOWC) system is proposed using PDM-QPSK. Spectral efficiency is prime requirement to enhance the performance of system and therefore, a suppression of optical single sideband (OSSB) in PDM-QPSK carrier spectrum is performed by employing fiber Bragg grating with 0.99 reflectivity. Proposed system is investigated in terms of log BER and error vector magnitude percentage (EVMP) at varied SWOS distances. Further, effects of the digital signal processing (DSP) in the receiver are analyzed by considering and neglecting the module. Results revealed that suppression of sidebands and employment of DSP enhance the system performance and competent to cover 52,000 km SWOS distance.

In this paper, the concept of a novel optical FM/PM demodulator which can be designed from low-cost passive optical components and can have peak-to-peak bandwidth in the GHz region has been described. The bandwidth can be increased by reducing the single mode fiber length incorporated in the design, which is followed by a corresponding fall in frequency sensitivity of the device. The bandwidth and frequency sensitivity can be traded-off keeping their product a constant. The crossover wavelength can be tuned by changing the length of the optical delay line and the length of the single mode fiber (SMF). The Figure of Merit (FOM) of the demodulator, defined as the bandwidth sensitivity product, has a value of π which is greater than that of a passive hybrid Tee microwave discriminator and those of Mach-Zehnder interferometer-based designs. Calculated third harmonic distortion (3HD) of the demodulated optical FM signal increases with the increase in FM index and with the increase in SMF length for a given modulation frequency. Typical 3HD for the device with SMF length of 1 cm is calculated to be −39.9 dB for FM index = 2 and a modulation frequency of 400 MHz.

Optical Codes Division Multiple Access is a multiplexing approach in which the transmitter a distinguishable optical code is assigned to each user in the communication channel. OCDMA is designed for radio frequency (RF) communication systems and it is a variation of the CDMA system. Subsequently, to develop all OCDMA communication systems, the success of CDMA in wireless networks, as well as the full benefits of fibre optics, such as good security, extremely high bandwidth, low attenuation, and long-haul transmission. In this research Spectral Amplitude Coding-Optical Code Division Multiple Access is proposed. Initially, Modified Double Weight and Zero Cross-Correlation (MDW-ZCC) is proposed in this research to construct the code design of SAC-OCDMA, it produces the best possible autocorrelation and cross-correlation values. Subsequently, a combined Single Photodiode (SPD) and Direct detection technique is introduced to decode the transmitter information and it reduces the noise. Accordingly, a Gaussian approximation technique is presented to estimate the Bit error rate from the eye diagram of BER and Q-factor. Accordingly, the proposed method is simulated using Python software. The performance metrics are Q-factor, and bit error rate and the proposed method is compared with the existing Three-Dimensional Single Weight Zero Cross-Correlation (3D-SWZCC) Code, Two Dimensional Spectral/Spatial Cyclic Shift (2D-SSCS), and Permutation Matrix Zero Cross-Correlation (PM-ZCC) Code. Subsequently, these results exhibit that the proposed method produces the best performance than the other methods and it estimates the BER. Consequently, future work is based on the study of 3D codes with m-sequence code in the spectral/time/spatial OCDMA domain. The approach has elegantly integrated the design of an encoder and a decoder, allowing the system to efficiently create code in 3D bipolar mode, respectively.

The photonic aspects of semiconducting hexagon-shaped photonic crystal fiber including effective mode area, effective mode index, dispersion, and confinement loss, have already been investigated. The finite element method has been used to compute the maximum distribution of the studied photonic crystal fiber by COMSOL software. The linear modifications from both the effective mode index and an effective mode area have been investigated. Dispersion and confinement loss are examined in terms of air hole ring number and wavelength. For every wavelength, the effective-index model implies that the studied fiber can indeed be single mode. Even though its practical single-mode range inside the opacity aperture of silica appears large, it is eventually confined by a bend-loss edge at both brief & medium wavelengths. Moreover, the reported fiber offers minimal confinement loss of almost 10 −8  dB/cm, birefringence 0.0012, and dispersion around 10 −11  ps/km nm.

A system is represented that uses 20 nm of channel spacing and unequal channel spacing along with four different types of transmission fibers on subcarrier multiplexing–wavelength division multiplexing (SCM/WDM) based radio over fiber (RoF) link. These five different kinds of fibers have been analyzed offering different propagation parameters. In case of 20 nm of channel spacing the performance of the link is improved by 35.32% with the use of True wave fiber. In this paper, 8 channel SCM–WDM based RoF based model is simulated and analyzed with different type of optical fibers covering distance of 10 km. A comparison of Q-factor at different optical power and different optical lengths has been made. Q-factor, bit error rate and eye diagrams have been examined for assessing the performance of the model.

In this manuscript the plasmonic flower shaped silver nano dipole antenna is investigated on the silicon dioxide substrate for the optical wireless communication. The nano-circuit modeling of the proposed flower shaped nano dipole antenna is discussed which will enable the design of nano-photonic chips. The resonance tuning of the proposed flower shaped nano antenna is exhibited through end-to-end stacking of the flower cells over a petal of the nanostructure. The various possible structures were designed to tune the frequency in the range from 170 to 271 THz which covers 1550 nm window of the optical communication. The gap tuned flower shaped nano dipole antenna is designed by controlling the optical coupling of the waves in between two dipole arms of the nano-antenna. Further the detailed investigation on the performance of the flower shaped nano dipole antenna is executed through the design parameters such as gap of the nano dipole antenna feed G and radius of the flower cell R . The optimum nano-antenna characteristics which are suitable for the optical wireless communication are observed at the resonance frequencies such as 270, 284.5, 260.5, 226.5 and 209 THz with reflection coefficients −42.17, −42.42, −42.17, −45.20 and −50.33 dB respectively.

In an all-optical communication system, an erbium-doped fiber amplifier performs a very significant role. The effectiveness of the operation of this kind of amplifier depends on different parameters of the amplifier. Variation of the intensities of pump and signal with distance along the radius of the fiber from the core axis is one such significant parameter. In our present case, we have studied the distribution of the intensities of both the pump and signal along the radius of the fiber in an erbium-doped dual-mode fiber amplifier for the LP 11 mode. In the present case, some step-index fibers of different normalized frequencies have opted. Our study is an application of the Chebyshev technique expressing the LP 11 modal field in the form of a power series. A little computation is required for the prediction of the concerned results by this technique. Results obtained from this study show an excellent match with those found by the rigorous finite element method establishing its accuracy. This study using such a user-friendly and accurate technique will be helpful to the optical engineers involved in this domain.

To achieve high data rate, futuristic wavelength division multiplexing passive optical network (WDM-PON) has pursued due to capability of multiplexing individual wavelength. This paper illustrates the possibility of different data rates along with distance to solve the challenges for next-generation WDM-PON systems. It is superior to present PON design due to rapid progress in different passive components for access network. In this paper, recent progress such as 20 Gb/s (gigabits per second) to 80 Gbps. WDM-PON technology has been carried out. Due to recent development in PON systems, demonstration of 80 Gbps (10 Gbps per wavelength * 8) based WDM-PON system with simplified and optimized design for last mile is presented. The simulation results have been compared to demonstrate the effect of the results achieved. At last, better quality (Q)-factor of 3.46, low value of BER (bit error rate) i.e., 2.48 × 10 −11 with reach of 80 km whereas high value of Q-factor of 22.16, eye height of 4.75 and BER of 3.61 × 10 −10 has achieved successfully using WDM-PON system.

In this paper a quantum dot light emitting diode (QDLED) system is modeled as a three dimensionless differential system. We identified three vital parameters Γ the rate of the output coupling rate of photons in the optical mode to the nonradiative decay rate of the number of carriers in the wetting layer (WL), Γ 1 the rate of the Einstein coefficient to the nonradiative decay rate of the number of carriers in the WL and δ o such that I/ We is the divide the injection current on Einstein coefficient multiplying elementary charge. Using these parameters a novel way to stability of the dynamics based on the number of interior equilibrium solutions admitted by the system has been obtained. We investigate the considered model is reach in dynamics and identified various bifurcations that are experienced by the considered system from the parameter space. These are saddle-node bifurcation, trans-critical bifurcation, and pitchfork bifurcation. In this study we offer mathematical proof for the incidence of these bifurcations that take place in the considered dynamical system as the parameters move between the regions presented in the parameter space and accordingly, this method was enhanced with numerical results.

Nowadays, polarization division multiplexing (PDM) employing different states of polarizations (SOP) is a prominent candidate to offer high capacity and improved performance. However, the incorporation of PDM in indoor wireless optical communication (WOC) systems is limited to horizontal and vertical SOPs only. Therefore, in this research article, a cost-effective and high capacity 90 Gbps non-return to zero (NRZ) line coding based 18 channels VLC system is presented by incorporating red–green–blue laser diodes (RGB LDs). Performance investigations of different SOPs such as SOP 0°, SOP 45°, and SOP 90° are carried out at diverse VLC link distances in terms of log BER and Q factor. Results revealed that the proposed VLC system can successfully cover the 6 m distance and red LD together with SOP 0 is found to be the highest performing.

In this work, a high-speed optical wireless system is realized to cater to the bandwidth demands of data services in inter-satellite by using 4 × 210 Gbps capacity enabled by dual-polarization (DP) 128-Quadrature amplitude modulation (QAM) at 25 GHz channel spacing and artificial intelligence (AI). For nonlinear compensation, equalization, normalization, and interference reduction, digital signal processing (DSP), and matched filters are included in the receiver. Results are analyzed by considering error vector magnitude (EVM), Q-factor, and BER at different link lengths. Moreover, two polarizations such as horizontal and vertical polarizations are investigated separately to find out optimal polarization state. Further comparison of the proposed DP-128 QAM is performed with quadrature phase-shift keying (QPSK)and results revealed that the QAM system carrying different states of polarization (SOPs) successfully covered 17,500 km at 125 Gbps and offered enhanced performance as compared to the conventional QPSK and QAM modulations due to narrow carrier spectrum (2 7 symbols).

In this paper, An UWOC system using a hybrid LD/LED link is proposed. A simulation was assumed to study the quality of the received optical signal with different modulation schemes such as 64-PPM, 4-QAM, NRZ-OOK, and RZ-OOK. A total of 64-PPM modulation schemes have enhanced the distance link compared with other modulation schemes. PIN and APD PDs are employed to validate the quality of the received optical signal under different water depths. Various metrics of BER, Q. factor, and data rate was introduced to assess the reliability of the hybrid LD/LED link. The simulation results show the proposed system can be achieved a good link with different water depths. The attenuation coefficient of water varies with depth and restricted the performance link distance by hybrid LD/LED link. The 64- PPM is a suitable modulation scheme for getting a long-distance link. The photodetector APD PD outperforms the PIN PD when 64-PPM and 4-QAM are applied.

A novel PCF (photonic crystal fiber) with variable air holes is designed to solve the problem that it is difficult to obtain flatted dispersion and low confinement losses simultaneously it can obtain flatted dispersion and low confinement losses by changing the size of air hole in the cladding. The structure of the optical fiber is analyzed by using FVFEM (full vector finite-element method) and APML (anisotropic perfectly matching layer) boundary conditions. The effective refractive index of the air hole at 1.55 μm is n 0  = 1, and that of quartz is set as 1.45,under these conditions, the simulation results show that the optical fiber has super-flat dispersion in the wavelength range of 1.25–1.78 μm, the dispersion varies ranges from 0 ± 0.68 (ps/nm km), and the confinement losses is less than 10 −3  dBb/m.

The purpose of this paper is to design an experimental system for underwater wireless optical communications (UWOC). By using an amplitude shift key (ASK), different frequencies in KHz are modulated over LED light. Four strategies are evaluated and compared (SISO, SIMO, MISO, and MIMO) with the purpose of determining the success of receiving optical signals. To receive these frequencies, a solar cell and photodiode (BPX61) are utilized. A digital storage oscilloscope (DSO) is used to view the received signal at the identical optical conditions. The results indicate that the system has a satisfactory link quality to receive frequencies when all four approaches are used in the same settings. The PD BPX61 is more efficient at receiving frequencies from the solar cell. The measurable frequency range of the received signals was 500 KHz for the PD BPX61 and 100 KHz for the solar cell. The (SISO) technique achieves the lowest SNR values, whereas the MIMO technique achieves the highest values.

In this paper, the hybrid LD/LED link for the UWOC system is proposed. The Three different wavelengths, namely 715, 532, and 412 nm are adopted as a carrier signal at different water depth variations. A simulation was carried out to assess the quality of the received signal based on bit error rate (BER), quality factor (Q. factor), and data rate. The results indicate that the suggestion system can achieve a good link with different water depths. In addition, the APD PD is better than the PIN PD. The enhancement in the maximum distance link can be achieved with an LD link.

One of the essential aspects of life is communication and in all communication systems, modulation and demodulation perform a crucial role in the transmission of transmitter-to-receiver data. Using various multiplexing techniques such as FDMA, CDMA and TDMA to work with the communication system, faced various problems such as low bit rate, multi-path fading, ISI and time dispersion. The incorporation of the OFDM approach gives an attractive solution to the aforementioned issues. OFDM transmitters and OFDM receivers with different modulation techniques are included in the OFDM-based different communication system. CO-OFDM was recently suggested and its extreme robustness against polarisation mode dispersion and chromatic dispersion was demonstrated in proof-of-concept transmission experiments. Optical fiber-based wired networks and also free space wireless networks require a premier technique for multiplexing i.e. CO-OFDM. In this paper, we investigated the performance of various modulation techniques which highlights several benefits such as channel robustness and greater efficiency of the available spectrum where multicarrier is used as high data rate bit streams from a single source are divided into the number of small subcarriers. OFDM is commonly regarded as discrete multitone (DMT) in this case. So in this review article, OFDM systems are also incorporated with their advantages and applications.

Optics has been successfully used for data processing. The basic building blocks of quantum computers are the quantum gates. Here, a quantum CNOT gate is proposed. To implement the gate advantages of polarization-based encoding technique and optical Kerr material-based switching are utilized. CS 2 can show this type of switching feature. An Nd-YAG laser source of 1.064 μm wavelength is used to implement the scheme. Intensity of the laser pulse should be of the order of 10 18  W/m 2 to excite the 2nd order nonlinearity of the isotropic nonlinear material.

In this paper, an experimental system for underwater wireless optical communications (UWOC) is designed on a lab scale. An amplitude shift key (ASK) modulation is used for modulating the frequency of the white LED light with a multiple input-multiple output (MIMO) technique. A solar cell and a photodiode (BPX61) are used as a detector to receive these frequencies and then compare the performances. Water turbidity was increased to investigate the effect on received frequencies by adding different concentrations of the hydroxyls Al(OH)3 and Mg(OH)2. We examined the (Vpp, SNR, and Av) parameter values to assess the quality of the proposed link. The lowest values of SNR are achieved by adding the fifth concentration C5 of suspended particles to the water with a solar cell in the receiver. Furthermore, the highest values of SNR are obtained by adding the first concentration C1 with the use of the photodiode detector (BPX61). The results show that the solar cell cannot be sensitive to the signal after 75 kHz. While the photodiode (PBX61) can be sensitive to the signal up to 300 kHz at the five concentrations of suspended particles.

Photonic crystals are periodic structures that are suitable for designing a variety of optical gates and logic circuits. In this paper, XOR and NOT logic gates are designed using two-dimensional square lattice photonic crystals. This structure consists of two inputs and one output, and the logical values ​​in the inputs and outputs are defined based on the amount of optical power. The plane wave expansion (PWE) method has been used in band structure calculations. The simulation results show that the proposed structure in a range of wavelengths has a photonic band gap that has a wavelength of 1.55 µm in this range. Therefore, the light sources placed in the inputs have a wavelength of 1.55 µm. Due to the use of a square structure that is easier to design and build, this structure is suitable for use in optically integrated circuits. Another advantage of this structure, in addition to its small dimensions, is the very low value of zero logic, which has increased the contrast ratio in the structure. The contrast ratio obtained in this structure is equal to 19.1 dB.

Nowadays, mental–insulator–metal (MIM) waveguides are widely used in the design of optical plasmonic waveguides due to their superior ability to confine surface plasmons up to sub wavelength scale. This research proposes the design of series and parallel circuits using cascaded plasmonic Mach–Zehnder interferometers (PMZIs). Each PMZI employs a nonlinear arm to switch light across the output port via the insertion of the nonlinear Kerr material poly(2-methoxy-5-(28-ethylhexyloxy)-PPV). The proposed design is having footprint of 104 µm × 11 µm. The finite-difference time-domain method is used to study, design, and analysis all optical series and parallel circuit proposals.

For communication in space, information transmission lines are critical for reaching the whole world. A long delay and a poor data transfer rates have been observed in radio frequency (RF) communication and therefore inter-satellite communication has become more common in recent years and optical wireless communication has advanced dramatically. Owing to its multiple advantages, including large channel bandwidth, high-speed connectivity and economical operations, IsOWC technology is becoming popular among researchers. Uniphase modulations such as NRZ modulation does not have efficient spectrum for high speed inter-satellite communication. PDM-256-QAM at 160 Gbps over IsOWC channel is demonstrated in this work using matched filter and DSP. Proposed system is investigated for PDM-256-QAM at 850 and 1550 nm wavelength and results analyzed in terms of Q factor, log symbol error rate (SER) and error vector magnitude (EVM).

This paper studies and investigates the performance of Gaussian minimum shift keying (GMSK) for underwater optical wireless communication (UOWC). Various scatterings may result in inter-symbol interference (ISI) and degrade system error performance in UWOC links. Bit-error rate (BER) is evaluated using different water environment models such as clear seawater, coastal, and harbor for a 20 m link range. Simulation results indicate the BER performance is degraded due to the temporal dispersion of impulse response for high data rates in turbid water. In addition, the bandwidth-symbol time product (BT) is an essential parameter in GMSK, affecting BER performance and power efficiency. Therefore, BT must be chosen with a value that balances BER and power efficiency. The results show that GMSK with BT = 0.5 is a good choice that satisfies BER = 10 −5 for SNR = 10 dB with an efficient power spectrum due to constant envelope and low out-of-band radiation.