Haul Communication Research Articles

A hybrid FSO/RF communication system with DSP for long haul communication

Abstract Due to the exceptional growth in mobile data traffic, emerging mobile access networks need a lot of bandwidth and robust network architecture as a crucial solution in delivering a high capacity for support in the future. The proposed work presents a detailed investigation of hybrid free space optical/radio frequency (FSO/RF) communication system at 320 Gbps channel capacity. A digital signal processing (DSP) compensation mechanism is used in the receiver system along with circular polarization division multiplexed (CPDM) 256-quadrature amplitude modulation (QAM) to improve system performance. Constellation diagrams have been used to measure the effectiveness of the system. The constellation diagrams which are considered for investigating the proposal are, (a) without DSP (digital signal processing), (b) with DSP without normalization and low pass filtering, (c) with DSP without carrier phase estimation (CPE) and frequency offset estimation (FOE) and (d) with DSP using normalization, low pass filtering, CPE and FOE, in FSO/RF system under clear weather, rain and haze. Effects of presence and absence of DSP in the coherent receiver have been investigated. Results show the improvement in system performance with least error vector magnitude (EVM), when DSP incorporated FSO/RF system is implemented using normalization, low pass filtering, CPE, FOE with perfect placements of symbols.

Implementation and analysis of 32 channel MDRZ DWDM system at narrow channel spacing

This work is proposed to examine modified duobinary return to zero modulation in DWDM long haul communication system. In this framework we simulate 32 channels each channel data rate is 40 Gbps multiplexed with the channel spacing 80 GHz, 90 GHz and 100 GHz to perceive 1.2 Tbps data. This data completed transmission Distance over 250 KM by utilizing scattering remuneration strategy. This 40 Gbps data is encoded by utilizing Mach Zehnder modulator (MRZ) inferred by CW laser of power − 10 dBm, − 5 dBm, 0 dBm, 5 dBm, 10 dBm. In the system analysis, we use modified duobinary return to zero (MDRZ) in the DWDM communication long haul system.

Suppression of Four Wave Mixing Effects Under Different Spectrally Efficient Modulation Techniques in Hybrid DWDM-OTDM Systems

Next generation optical networks require high spectral efficiency to meet the demand of high bandwidth for ultra-long haul communication. Spectrally efficient modulations using hybrid DWDM-OTDM systems can be used to achieve this. However, fiber nonlinearities such as four-wave mixing (FWM) will increase simultaneously and this will degrade the performance of WDM optical system. This paper explores the FWM reduction in 32 channels, 40 Gb/s hybrid DWDM-OTDM network using RZ-OOK, 16-QAM and PDM-QPSK modulation format at 200 GHz and 100 GHz channel spacing. Optical received power, BER, Q- factor, eye diagram and FWM side band power are analyzed at -15dBm to +15dBm channel power. All these modulations have shown a significant reduction in FWM. In addition, the 16-QAM gives highest reduction in FWM along with least BER of 7.9×10−158 and maximum Q-value of 27.74.

Tapered waveguide design for mode conversion in mode division multiplexing (MDM)

ABSTRACT In this paper, a tapered waveguide design was used in mode division multiplexing (MDM) as a mode converter. It was investigated to be used for switching purposes in short haul communication in a data center. This paper shows the results of a Gaussian beam being converted into transverse modes and vice versa. It also shows the multiplexed version of the modes being converted into a specific target mode. There are two and three combinations of multiplexed modes in the tapered waveguide design, with modes computed as well as converted into targeted modes. The reason for this experiment is to accomplish the goal of replacing opto-electronic switches at data centers into an all-optical switching mechanism. Therefore, this design will enable the processing of large amounts of data using optical switching apparatus by creating additional data channels. It results in providing an all-optical mode conversion switch that incorporates high-speed routing of data from one server into another data center.

Palliation of Four-Wave Mixing in Optical Fibers Using Improved DSP Receiver

A long haul optical communication system (LHOCS) is one of the key resources to fulfill the higher capacity requirements in future communication networks. To launch LHOCS, the system mainly faces high order nonlinear effects. The four-wave mixing (FWM) is one of the major nonlinear effects, which limits the transmission distance. Therefore, in this paper, an advanced duo-binary (DB) modulation scheme-based system is evaluated by employing an improved digital signal processing (IDSP) approach at the receiver side to suppress the FWM effect. In addition, an analytical analysis is also performed for the proposed system. To observe the difference between the IDSP and conventional digital signal processing (DSP), the various performance metrics such as bit error rate (BER), Q-factor, and optical signal-to-noise ratio (OSNR) parameters are evaluated. Variable channel spacing along with polarization mode dispersion (PMD) are analyzed at several ranges of input powers and fiber lengths. The analytical and simulation-based calculations exhibit the effectiveness of the proposed model and hence, FWM effect are compensated to achieve 500 km optical fiber propagation range with a BER below 10−6.

Hybrid Dy-NFIS & RLS equalization for ZCC code in optical-CDMA over multi-mode optical fiber

For long haul coherent optical fiber communication systems, it is significant to precisely monitor the quality of transmission links and optical signals. The channel capacity beyond Shannon limit of Single-mode optical fiber (SMOF) is achieved with the help of Multi-mode optical fiber (MMOF), where the signal is multiplexed in different spatial modes. To increase single-mode transmission capacity and to avoid a foreseen “capacity crunch”, researchers have been motivated to employ MMOF as an alternative. Furthermore, different multiplexing techniques could be applied in MMOF to improve the communication system. One of these techniques is the Optical Code Division Multiple Access (Optical-CDMA), which simplifies and decentralizes network controls to improve spectral efficiency and information security increasing flexibility in bandwidth granularity. This technique also allows synchronous and simultaneous transmission medium to be shared by many users. However, during the propagation of the data over the MMOF based on Optical-CDMA, an inevitable encountered issue is pulse dispersion, nonlinearity and MAI due to mode coupling. Moreover, pulse dispersion, nonlinearity and MAI are significant aspects for the evaluation of the performance of high-speed MMOF communication systems based on Optical-CDMA. This work suggests a hybrid algorithm based on nonlinear algorithm (Dynamic evolving neural fuzzy inference (Dy-NFIS)) and linear algorithm (Recursive least squares (RLS)) equalization for ZCC code in Optical-CDMA over MMOF. Root mean squared error (RMSE), mean squared error (MSE) and Structural Similarity index (SSIM) are used to measure performance results.

Fractional LMS and NLMS Algorithms for Line Echo Cancellation

In long haul communication environments, speech data transmission is severely affected by echoes. This phenomenon results in high bit errors as well as in degraded and annoying performance. Traditionally these problems, including hybrid and acoustic echoes, have been controlled through the use of echo suppressors. These suppressors were subsequently replaced by line echo cancellers using adaptive Finite Impulse Response filters. Fractional calculus has been applied successfully for fixed filtering with constant coefficients and in discrete time adaptive filtering that adjusts the weights according to the environment. This paper presents the Fractional Least Mean Square (FLMS) and Fractional Normalized LMS (FNLMS) algorithms for application in echo cancellation. Moreover, the performances of the FLMS and FNLMS are compared with those provided by the standard LMS, NLMS and Block Discrete Fourier Transform solutions. The mean square error criterion is used as the performance comparison criterion for two types of voice signals namely real and synthetic. The simulation results show a performance improvement of about 50% over the traditional counterparts.

DSP-Assisted Nonlinear Impairments Tolerant 100 Gbps Optical Backhaul Network for Long-Haul Transmission.

High capacity long haul communication and cost-effective solutions for low loss transmission are the major advantages of optical fibers, which makes them a promising solution to be used for backhaul network transportation. A distortion-tolerant 100 Gbps framework that consists of long haul and high capacity transport based wavelength division multiplexed (WDM) system is investigated in this paper, with an analysis on different design parameters to mitigate the amplified spontaneous emission (ASE) noise and nonlinear effects due to the fiber transmission. The performance degradation in the presence of non-linear effects is evaluated and a digital signal processing (DSP) assisted receiver is proposed in order to achieve bit error rate (BER) of 1.56 × and quality factor (Q-factor) of 5, using 25 and 50 GHz channel spacing with 90 m effective area of the optical fiber. Analytical calculations of the proposed WDM system are presented and the simulation results verify the effectiveness of the proposed approach in order to mitigate non-linear effects for up to 300 km length of optical fiber transmission.

Novel spider web photonic crystal fiber for robust mode transmission applications with supporting orbital angular momentum transmission property

In this article, a novel spider web shaped circular photonic crystal fiber (PCF) is proposed and analyzed. It can support more orbital angular momentum (OAM) modes up to 26. This PCF also operates at 1000 nm bandwidth ranging from 800 to 1800 nm. The proposed PCF provides a design strategy for better OAM quality by using the finite element method (FEM). It also includes seven OAM parameters with a better requirement of PCF. In addition, relatively lower confinement loss (less than $$10^{ - 8}$$ dB/m) is obtained for maximum eigenmodes. The most of OAM modes are shown smooth dispersion profile. Besides, the nonlinear coefficient is comparatively low, maximum modes are shown nonlinear coefficient around 2 to 3 W−1 km−1 at 1.55 μm. This novel structure is a strong candidate for robust, secure, high speed, and high-capacity transmission. It can be also used in mode division multiplexing, long haul communication and sensing.

Performance Analysis of Laser Phase Noise Compensated COOFDM System

AbstractOrthogonal Frequency Division Multiplexing along with the coherent detection and spectrally efficient modulation formats is a promising solution for long haul and high speed communication systems. Although they offer significant advantages which make them suitable for high speed and long haul communication systems they all are susceptible to phase noise. In this paper a combination of RF-pilot-based approach followed by pilot-based equalization approach is used for laser phase noise compensation. The various parameters such as drive voltage, bias voltage and extinction ratio are optimized to get the optimum performance from the proposed scheme. The designed system is then analyzed in terms of Symbol Error Rate (SER), constellation diagrams and error vector magnitude using various types of Quadrature Amplitude Modulation (QAM) formats.

Ring-based coil structure photonic crystal fiber for transmission of Orbital Angular Momentum with large bandwidth: Outline, investigation and analysis

A unique, spectacular design of Photonic Crystal Fiber (PCF) is discussed in this paper to introduce one of the highest numbers of Orbital Angular Momentum (OAM) modes for the very first time with a very large bandwidth of 1,900 nm. Three layers of convoluted coiled structure air cavities formed the cladding region. The optimal design of PCF is used to derive the OAM properties. Finite Element Method (FEM) is used to examine and calculate the fundamental optical characteristics. The result of simulation supports 56 OAM modes with flat dispersion variation. Most of the OAM modes for confinement loss are below 10−8 dB/m where the lowest value is 1.7407×10−11 dB/m at wavelength 1,100 nm for HE11,1 mode. The non-linear coefficient and numerical aperture are lower than 4 W−1km−1 and 0.17, respectively. These splendid optical characteristics ensure the addressed design as a striking competitor for OAM transmission with large bandwidth and many other relevant optical communications. It can be used in long haul communication, encoding and Mode Division Multiplexing (MDM).

Performance Optimization of Diagonal Identity Matrix and Enhanced Double Weight Codes in Terms of Security for Short Haul Communication

Optical code division multiplexing is getting attention because it is an imminent multiple access technology which can cater ever increasing data traffic as well as multiple user access in optical networks. In this work, a zero cross correlation based diagonal identity matrix code is presented and it is compared with the enhanced double weight code to check the superior code in OCDMA system at data speed of 30 Gbps. Effect of some parameters of OCDMA system which prominently affects the security of the system and these are input power, linewidth and modulator extinction ratio. Optimization using single parameter optimization and multiple parameter optimizations has been done. In order to accomplish the work, optiwave optisystem software is used and extensive literature survey is done, issues encountered are carefully checked and to address the issues, proposed system is presented. Results are evaluated in terms of Q factor, bit error rate (BER) and signal to noise ratio. Novelty of proposed work is the search of optimal parameters of both the codes in terms of enhanced security such that eavesdropping at these optimal parameters will become tedious for unauthorized user.

Performance analysis of a 10 Gbps-60 GHz high speed RoF transmission system

Radio over fibre (RoF) is a revolutionary technology, which integrates radio and optical networks with a substantial bandwidth for wireless communication systems with minimum distortion and low cost. This paper investigates the performance of a radio over fibre system for high speed, moderate data of 10 Gbps encoded by RZ and NRZ code. The Mach-Zehnder modulator (MZM) is used to modulate the encoded data using 60 GHz radio frequency (RF). The results are obtained for the RoF system for the optical fibre of various lengths of 30, 45, 60 and 70 km. The performance of RZ and NRZ encoding is discussed using BER, Q factor, eye diagram and output power. It is observed that NRZ performs better than RZ for long haul communication.

A high speed 100 Gbps MDM-SAC-OCDMA multimode transmission system for short haul communication

In this work, a cost-effective spectrum amplitude coding optical code division multiple access (SAC-OCDMA) multimode transmission system is designed with the integration of mode division multiplexing (MDM) scheme in order to transmit 100 Gbps of data over 11 km multimode link. OCDMA scheme is carried out by using random diagonal (RD) code whereas MDM scheme is carried out by using modal multiplexing of Hermite Gaussian (HG) modes 00 and 01. The reported results show the successful transmission of 100 Gbps data over multimode link. Furthermore, the performance of multimode fiber and few mode fiber is investigated in terms of bit error rate which shows that few mode fiber performs better than multimode fiber link for the proposed MDM-OCDMA system. Moreover, the decomposition of HG modes into linearly polarized (LP) modes at receiver side is presented.

Highly-birefringent and ultra-wideband low-loss photonic crystal fiber with rhombic and elliptical holes

In this paper we propose a novel type of highly-birefringent and ultra-wideband low-loss photonic crystal fiber (PCF) incorporating elliptical holes in the cladding and rhombic holes located along the transversal axes. The PCF is simulated and analyzed with finite-difference time-domain method. The properties of PCFs were investigated for various distribution, shape and size of air holes. For the optimized PCF design the birefringence reaches 8×10−3 at 1550 nm and the confinement loss is as low as 5×10−4dB/km with single mode operation in an ultra-broad transmission band (500 nm–1800 nm). Furthermore, the single mode and single polarization transmission could be achieved in this PCF at longer wavelengths beyond 1600 nm. This kind of PCF has potentials in optical long haul communication and optical fiber sensing.

Effect of Alternate Polarization for SD-WDM System Using Hybrid Optical Amplifier

The effect of alternate polarization (alP) has been investigated for 400 × 200 Gbps super dense wavelength division multiplexing (SD-WDM) system using RAMAN-EDFA-RAMAN hybrid optical amplifier (HOA). Further evaluation has carried out for the characteristics of bit error rate (BER) and quality factor (Q-factor) for enhance long haul optical communication. Remarkable performances have recorded by al-PNRZ modulation technique with acceptable outcome in terms of quality factor (Q-factor) 20.5 dB and bit error rate (BER) of 10–40 with 100 GHz channel spacing.

Secure EEG Signal Transmission for Remote Health Monitoring Using Optical Chaos

For the very first time, we present the use of optical chaos for the secure transmission of electroencephalogram (EEG) signals through optical fiber medium in remote health monitoring systems. In our proposed scheme, a semiconductor laser source is used to generate optical chaos, which hides EEG signal before its transmission over the optical fiber medium. The EEG signals are acquired by using a 14-channel Emotiv headset device, which are then processed and rescaled to be compatible with the experimental environment (Optisystem). The mixing of EEG signals and chaos is performed using additive chaos masking scheme, which exhibits certain useful properties such as simplicity and easy recovery of the message. Chaotic data (a combination of EEG signals and chaos) is sent over the optical fiber medium to investigate propagation issues associated with secure EEG signal transmission. The scheme is implemented for long haul communication in which the linear impairments of optical fiber are controlled for successful transmission of the secure signal. The parameters at transmitting and receiving sides are selected to achieve synchronization, such that the transmitted signal could be subtracted from identical chaos to restore the original EEG signal at the receiving side. The scheme is tested for different lengths of the optical fiber cable in which the quality of the received signal is determined by obtaining Q-factors. This scheme could also be used with medical signals such as electrocardiography and electromyography.

Performance Analysis of Distributed Raman Amplifier Using Different Pumping Methods in DWDM Communication Systems

Abstract The objective of this work is to investigate and compare the impact of forward, backward and bidirectional pumping methods in repeater less distributed Raman fiber amplifier system and to analyze its benefits in long haul optical communication links. The effect of different pump wavelengths and pump powers are also analyzed. By adjusting the forward pump power as well as backward pump powers carefully, the transmission performance can be improved. The pump power ratio is adjusted to 20% so that the degradation of signal due to non-linear effect is reduced. The distributed gain and pump penetration depth for different pump power ratios are also examined. A comparison of different pumping methods reveals that bidirectional pumping gives the optimum performance in terms of higher gain and lower noise figure when compared to single pumps and unidirectional pumping. Low pump power ratios lead to better transmission performance than higher pump ratios due to lesser non-linear effects. The simulation results indicate that signal power evolution decreases with the increase in length of the fiber. It is also found that the pump power is more relevant during the first 50 km of the distributed fiber line and it decreases as it goes beyond 100 km. By choosing the optimum pumping methods and number of pumps, Raman Amplifiers can be used in almost all places where optical amplifiers are required.

Simulation and implementation design of multi-mode decoder for WiMAX and WLAN applications

The need for achieving high data throughput with low hardware complexity for long haul communication systems is a challenging task. The emerging communication systems in recent times have benefited from the availability of multi-mode decoders which can achieve better error rate performance with reduced complexity under noisy channel conditions. This paper presents a low complex multi-mode decoder architecture for Wi-Max and WLAN applications. To achieve good error correcting performance with a better decoding stability, a modified optimally quantized offset min-sum decoding is adopted. By exploring the properties of the layered decoding scheme, an enhanced quasi-cyclic low-density parity-check (QC-LDPC) code with sub-matrix re-ordering and layered decoding scheme is employed to offer adequate flexibility for parallel degree optimization and convergence speed. This in turn reduces the linear encoding complexity and data correlation problems during the multi-mode operations of the proposed decoder. Furthermore, to reduce interconnect complexity and the critical path delay, a modified reconfigurable routing network is employed. The proposed multi-rate decoder is designed and implemented using 65 nm CMOS Technology to support all the modes of IEEE 802.11n and IEEE 802.16e applications. The implementation results show that the multi-mode decoder achieves good throughput-to-area ratio (TAR) with less power consumption when compared to other multi-mode decoders.

Solid core PCF-based mode selector for MDM-Ro-FSO transmission systems

Radio-over-free-space (Ro-FSO) technology is a combination of free-space optics (FSO) and radio over fiber. It plays a significant role in radio-frequency signal transmission in mobile network communication through high-speed optical carrier without any licensing and costly cables. Photonic crystal fibers also play a significant role to deliver data at faster rate for short haul communication. This paper, for the first time to the author’s best knowledge, utilizes mode division multiplexing in conjunction with solid core PCFs to transmit $$2 \times 2.5$$ Gbps–5 GHz data over 2.5 km free-space link. The results are reported in terms of bit error rate, spatial profiles of received modes, mode spectrum of modes and eye diagrams. Furthermore, proposed PCF-MDM-Ro-FSO transmission system is also reported under the impact of atmospheric turbulences.