Volume 44, Issue 3

An innovative cost-effective fourth-generation bidirectional wireless hybrid transport system, employing optical add-drop multiplexing technique, power doubler amplifier and data comparator, is proposed and experimentally demonstrated. The proposed system can transmits, downlink 80 community antenna television (CATV) channels, two different wireless-over-fiber (WoF) data signals (1.5-Gbps/2.4-GHz, 2.5-Gbps/3.5-GHz) at two different base stations over 40 km and 80 km single-mode fiber (SMF), respectively, and an uplink 5-Gbps baseband (BB) signal at central station over 40 km SMF, using a single optical carrier. The good carrier-to-noise ratio, composite-second order and composite-triple bit are achieved for CATV channels, and small BER and open eye-diagrams are achieved for WoF and BB signals.

In this paper, a combination of Tone Reservation-Signal to Clipping noise Ratio (TR-SCR) and Companding schemes is proposed for underwater wireless optical communication (UOWC), in order to solve the problem of high peak-to-average power ratio (PAPR) of underwater Optical-Orthogonal Frequency Division Multiplexing (O-OFDM) system. Two optical modulation schemes, namely Direct Current-biased Optical OFDM (DCO-OFDM) and Asymmetrically Clipped Optical OFDM (ACO-OFDM), are adopted separately to achieve intensity modulation/direct detection over the seawater channel, with a distance of 100 meters of wireless optical transition to obtain the system bit error rate (BER). In the TR-SCR scheme, only the maximum amplitude signal is selected to reduce the complexity of the algorithm. The LSA method is introduced in the TR-SCR scheme for iteratively updating the signal to speed up the convergence. Finally, with the combination of the Companding scheme, the PAPR performance is significantly improved. The PAPR of the underwater optical OFDM system is reduced to 3.85 dB with its BER still satisfying the UOWC system requirements.

In this paper, we are going to design simulate an all optical OR gate based on two-dimensional photonic crystals. The proposed structure was designed based on phase shift keying technique. The working principle of the proposed structure is based on constructive and destructive interference of optical beams. The simulation results shows that the rise and fall times are 0.8 and 0.2 ps, respectively.

The electro-optic effect becomes prominent when an electric field is applied across the optic axis of a dielectric material inducing the changes in refractive indices of the medium. Kerr and Pockels cells are massively used as optical switches because of their nonlinear electro-optic character. Potassium di-hydrogen Phosphate (KDP) crystal is a very good electro-optic Pockels material as well as has a good switching behavior in optical and opto-electronic domain. The principle of this electro optic effect can be successfully used to develop optical switch based information processing devices. Transmission co-efficient of the polarized light beam have been modulated in a new way by introducing a multi passing scheme across a electro-optic material. Here transmission co-efficient plays a vital role to examine how much output intensity changes for developing feedback one by one in ascending order. In this paper a novel study for the sizable increase of transmission co-efficient of a KDP crystal for a fixed biasing voltage is reported adopting proper feedback mechanism of light. This paper we also observe an theoretical basis for achieving unit transmission coefficient which minimum amount of voltage require for adopting comparatively many large number of feedback.

Application of fiber Bragg grating (FBG) in optical communication is an evolving field. In this research paper, various types of chirped FBG’s (CFBG) have been used with avalanche photodiode (APD) on the designed optical fiber communication (OFC) link. Data rate of 20 Gbps and return-to-zero modulation format has been kept as fixed parameters. The designed link has been evaluated for varying fiber lengths (100, 200, 300, 400 and 500 km), various type of CFBG’s (linear, quadratic, square root and cubic root) with Gaussian apodization function, varying grating lengths (10, 20, 30, 40 and 50 mm) and operating temperatures (5°C, 10°C, 15°C, 20°C, 25°C, 30°C). The designed OFC link has also been evaluated for APD with and without CFBG. The performance evaluation matrix parameters selected are Q -factor, bit error rate and eye diagram. The OFC link employing CFBG with APD has been found to be superior. In compensating chromatic dispersion, optimum results have been observed for linear CFBG with Gaussian apodization function in comparison to other types of CFBG with 50 mm grating length for the maximum transmission distance.

In this paper novel designs for linear block code encoder and decoder using optical techniques have been proposed. The structures are designed and simulated using lithium niobate based Mach–Zehnder Interferometer (LN-MZI) and nonlinear material MEH-PPV [poly (2-methoxy-5-(28-ethylhexyloxy)-PPV)] (plasmonic) based MZI (P-MZI). The proposed LN-MZI designs offer attractive parameters such as high extinction ratio (>35 dB) and low insertion loss (<0.095 dB), while the proposed P-MZI designs possess a compact structure (3,020–12,375 µm 2 ). An analytical comparison between the two design methodologies and other earlier proposed designs is presented. Each design is presented with a verified mathematical structure. Other performance parameters like contrast ratio and amplitude modulation have also been computed for the presented designs.

The study has outlined the finite element technique used for the fiber modal analysis of photonic crystal fiber (PCF) structure with a hexagonal/circular air holes arrangement on the cladding of pure fiber-optic silica. The used fibers that are namely highly nonlinear fiber (HNLF), single model silica fiber (SMSF) are combined with PCFs with different dopants concentration. Leakage loss, number of guided resonant modes, fiber birefringence, effective refractive index and cross-section areas and nonlinear coefficient parameters are measured inaccurate estimation. The optimum resonant guided modes are also estimated for different lattice infrastructure in circular PCFs.

We demonstrate a radio-over-fiber-based hybrid wavelength-division-multiplexed/time division multiplexed passive optical network (PON) to transmit 5 Gbps data rate to serve 32 subscribers. A broadband light source (BLS) is realized by mutual injection locking between two Fabry-Perot laser diodes at the transmission section to seed wavelength-division-multiplexed channels. Mutual injection locking technique is used to enhance the performance over single Fabry-Perot laser diode and 15  dB/Hz improvements in relative intensity noise(RIN) is realized in our proposed network system. All-optical up-conversion of a 10-GHz 1.25 Gbps on off keying radio frequency (RF) signal is achieved using one single-arm Mach-Zehnder modulator (MZM). Transmission performance over 25-km single mode fiber is investigated. Low bit error rate with enhanced eye-diagram is obtained in our proposed system. As a result, the radio over fiber (ROF)-based wavelength-division-multiplexed/time division multiplexed PON set up employing mutually injection locked Fabry-Perot laser diodes can be a better choice in high speed long-haul optical communication system.

For addressing needs of modern day communication needs, new type of networks are required to be evolved to cater the demand of high data rates. Use of survivable elastic-optical-network (EON) with existing passive-optical-networks (PON) may provide the solution for this. The present work focus on employing EON–PON based wave-length-division multiplexing enabled communication system comprises of 2×5 Gbps for downlink and 2×1 Gbps for uplink over a single-mode-fibre of length 100 km. The results are the evaluated via bit-error-rate analyser, q factor and eye diagrams.

The internet services have become more popular rapidly over the decades. This is because of the inspiration created by new content-hungry applications on end-user devices like smart phones. Wavelength division multiplexed mesh networks are the optical backbone, working as the aggregating point of huge volume traffic, interconnecting several access networks and end users. The need of virtual data center is to retain services in case of failures such as optical link failures and resource or power outage in data centers that occurs in the cloud infrastructure and improve the survivability. The physical infrastructure may disconnect the virtual machines and physical data centers. This leads to the reduction in computational as well as communicational capabilities of the cloud. To overcome these issues, an integer linear programming model called hamiltonian graph analysis – mixed integer linear programming (HGA-MILP) is proposed in this work by utilizing hamiltonian graph model. The main motive of this research is to design a survivable data centre network mapping problem against physical link failures. Use of hamiltonian path methodology is helpful to organize data and improve network performance.

There is an increase in the number of chronic and heart diseases due to work culture etc. The current hospital-centric system is becoming inefficient to treat patients that demand immediate attention and this can efficiently be implemented by using the Internet of Things (IoT) technology. The aim of this paper is to implement IoT-based health monitoring system which measures temperature, blood pressure, and heartbeat of a patient located remotely and send the data to the doctor for analyzing the condition of the patient. And also an optical light sensor is used to check the light condition in the patient room and based on the sensor value the light will be controlled (ON/OFF). The system is implemented using a BeagleBone Black (BBB) development board. This model saves the work time of the doctors to check the patient’s condition. By using the Global System for Mobile communication (GSM), the patient’s data is sent to the cloud through which the doctor can monitor the parameters anywhere in the world using the mobile application or web page.

Weather conditions are severely degraded the performance of FSO communication link. Atmospheric turbulence is one of the important weather conditions that degrade the performance even under clear sky condition. In this paper, we provide a noble analytical approach to evaluate the performance of STBC coded FDM FSO communication system with direct detection optical receiver under turbulent condition. Analysis is carried out to find the channel capacity of RF subcarrier modulation taking into consideration the effect of strong atmospheric turbulence which is modeled as gamma-gamma distribution and the probability density function of the conditional CNR, conditioned on a given turbulence-induced fading is derived considering equal gain receive diversity combining technique with direct detection optical receiver followed by RF synchronous demodulation. Results are evaluated numerically in terms of average CNR, BER and channel capacity for several system parameters like turbulence variance, link distance, data rate, etc.

With the continuous progress of society, people’s requirements for communication technology are getting higher and higher, and the traditional communication system has not been able to meet the growing data needs of society. Therefore, it is of practical significance and guiding significance to study the transmission reliability of communication system. In this study, the wireless communication system-based on optical fiber and Class-AB technology and non-linear distortion model used for improving communication quality were briefly introduced, and then simulation analysis was carried out on the traditional simulation system and communication system designed in this study using VPI TransmissionMaker software. The results demonstrated that the proposed system had better stability than the traditional system. The comparison of the electricity frequency spectrum between the two systems showed that the proposed system could effectively suppress the third-order distortion current, and 28.6  dBm distortion current was suppressed. The Spurious Free Dynamic Range (SFDR) of the proposed system was higher, and the fit line slope of the distortion current was 5, differing from that of the traditional system, 3. which further demonstrated that the distortion current was inhibited. In conclusion, the optical communication system designed in this study can effectively improve the communication quality and increase the reliability of wireless communication.

The effect of crosstalk due to inter-core coupling on the bit error rate (BER) performance of a fiber optic communication link with a homogeneous multi-core optical fiber (MCF) and a direct detection receiver with optical preamplifier is analytically evaluated and presented in this paper. Coupling coefficients due to inter-core coupling in a 7-core MCF is evaluated numerically with as a function of core-to-core distance (pitch) and relative refractive index contrast. Coupling length is determined against various index contrasts and at different core pitches. Crosstalk power, Signal to Crosstalk plus Noise Ratio (SCNR), BER and power penalty at any output core with light launched into other core of a 7-core MCF are determined analytically. The results show that there is mentionable deterioration in BER performance due to coupling induced crosstalk, and system suffers distinct power penalty at a given BER. For example, power penalty at BER of 10e-9 is found to be 4.0 dB and 4.3 dB for a MCF link of 10 km corresponding to relative refractive index difference of 0.0036 and 0.0030, respectively, for a pitch value of 30 µm and core radius of 4.5 µm.

Transmission of data between satellites has been revolutionized via the use of Inter-satellite optical wireless communication (Is-OWC). In this work, we evaluate the validation of high speed and long reach Is-OWC system suing return-zero encoding and wavelength division multiplexing. Two channels, each carrying 10 Gbps of information transmits data on Is-OWC link of 2200 Km length. The performance of the proposed system is investigates in terms of bit-error rate, Q-factor and eye patterns.

This paper studies the bit error performance analysis of decode-and-forward (DF) relays-based free-space optical (FSO) communication systems using avalanche photodiode (APD). The system uses subcarrier intensity binary phase shift keying (BPSK) modulated signals and subjects to scintillation due to optical turbulence. A log-normal random process is considered to model the received signal intensity fluctuation for a clear-air condition (weak atmospheric turbulence) scenario. Mathematical expressions of the average bit error probability and bit error rate (BER) are derived by taking into account the impact of atmospheric loss, thermal-noise and shot-noise limited conditions. It can be inferred from the numerical results that using DF relay nodes can extend the transmission distance and minimize BER performance of FSO system significantly compared with the direct transmission. Moreover, the selection of APD’s gain values is essential to minimize the system’s error rate performance. Therefore, the system could achieve the minimal BER by selecting an optimal average APD gain value appropriately. Moreover, the optimal average gain values of APD significantly depend on various conditions, such as the bit rate, total transmitted power, and the number of relay nodes.

In this paper, the performance of a mixed dual hop asymmetric radio frequency andfree space optical (RF-FSO) communication link is investigated. A closed form analytical expression for evaluating outage probability of mixed RF-FSO link is obtained. The source to relay link is RF link modelled using Nakagami- m fading. The relay to destination link is an FSO link subjected to atmospheric turbulence, modelled using K-distribution. Decode-and-Forward (DF) relaying protocol is used. Further, the effect of pointing error on the performance of the link is analysed using obtained closed form expression. It has been observed that increase in the pointing error leads to reduction in outage performance of the link.