Modified Duobinary Return To Zero Research Articles

Mode Division Multiplexing Free Space Optical Communication System Performance with Aperture Averaging in Atmospheric Turbulence and Various Weather Conditions

Due to the serious challenge for mobile operators as a result of spectrum congestion in radio frequency spectrum, free space optical (FSO) communication has been considered a timeous alternative especially for future generation high capacity wireless networks. Although FSO offers advantages such as huge data carrying capacity among others, it suffers from the drawback of atmospheric turbulence and adverse weather conditions. As a mitigation to this problem, mode division multiplexing (MDM) has been another research direction. This paper proposes the design and numerical simulation of a hybrid modified duobinary return to zero (MDRZ) MDM free space optical communication system, which to the best of the authors’ knowledge has not been a subject of investigation. The performance metrics used are the bit error rate, quality factor and received optical power. Two modes, HG00 and HG01 were investigated and compared. It has been observed that the BER, Q factor and received power degrades as we increase the beam divergence, FSO transmission distance and data rate. Moreover, the performance gap between clear and moderate weather conditions is more for HG00 than for HG01 for the same considered data rates. The aperture averaging has been shown to be a strong mitigation strategy especially in foggy conditions.

Performance comparison of different intensity modulation formats for FSO systems

Abstract Intensity modulation (IM) formats are the legacy formats which are continuing to act as modulation formats of interest in fiber optic communication systems and optical networks. The IM formats have become formats of interest in free space optic communication (FSO) systems due to its simple generation and detection principle, thus making FSO system economical and easier to handle/operate under adverse and random characteristics of atmospheric channel. This paper compares the performance of different IM formats (with memory and without memory or memoryless). The IM formats considered here are non return to zero (NRZ), return to zero (RZ), carrier suppressed RZ (CSRZ), vestigial side band CSRZ (VSB-CSRZ), duobinary RZ (DRZ) and modified duobinary RZ (MDRZ). The comparative analysis investigates the effect of launch power and length of FSO channel at different data rates of 10 Gb/s and 40 Gb/s for single channel FSO system, with the help of simulations. The results discussed, depicts that VSB-CSRZ outperforms other modulation formats at 10 Gb/s and duobinary format has shown lesser degradation in system performance when bit rate increases from 10 Gb/s to 40 Gb/s.

A fiber-wireless integration approach in WDM-PON architecture, boosted with polarization multiplexing and optical frequency comb source

Abstract The paper discusses an optical frequency comb source (OMCG)-enabled hybrid single mode fiber (SMF) and free space optical (FSO) communication system (fiber-wireless) delivering a total capacity of 96 Gbps by incorporating polarization division multiplexing (PDM) in passive optical network (PON) architecture. For the accomplishment of PDM, three diverse states of polarization (SOPs) are explored such as 00, 450, and 900. Performance investigation of proposed system is conducted for assessing Q factor and BER by exploring the different modulation formats in proposed system such as modified duo-binary return to zero (MDRZ), return to zero (RZ), compressed spectrum RZ (CSRZ), and non-RZ (NRZ). Results revealed that presented design can cover 30 km SMF + 3.4 km FSO range by incorporating MDRZ due to its spectral efficient and dispersion tolerant properties.

Ultra-long haul high speed 96 × 40 GB/s radio over IsOWC system employing advanced modulation scheme

Abstract This paper successfully demonstrates that point-to-point (P2P) superdense wavelength division multiplexing (SDWDM) based on the radio over intersatellite optical wireless communication (Ro-IsOWC) system of 96 channels separated by a 100 GHz bandwidth with 40 GB/s data rate on each stream at a 10,000 km link range has been designed and investigated. The performance of the proposed work has been evaluated by considering the comparison of advanced modulation schemes such as carrier-suppressed return-to-zero (CSRZ), duobinary return-to-zero (DRZ), and modified duobinary return-to-zero (MDRZ) with an optical preamplifier on the bases of bit error rate (BER), quality factor, eye height, and optical signal-to-noise ratio (OSNR) in the clear weather condition. Moreover, the effects of internal parameters such as transceiver aperture diameter and gain of an optical amplifier also have been analyzed with an optimized modulated system. Apart from this, the system performance also has been assessed under varying data rates and OWC frequency ranges with the best-suited modulation format. It has been found that the CSRZ modulation format has shown robust performance and can achieve BER as better as 10−09 with a 5.5 dB quality factor for all wavelengths. It also has been observed that the quality of the received signal deteriorates below an unacceptable value for data rate and link distance beyond 40 GB/s and 10,000 km, respectively.

Investigation of MDRZ and DPSK modulation schemes employed in DWDM systems for smart city 5G access networks

Wavelength division multiplexing (WDM) is one of the emerging technologies for data transmission in 5G access network assembly between the antenna unit (AU) and the distribution unit (DU). Here, in this work, we evaluate and analyze a dense wavelength division multiplexing (DWDM) — passive optical networks (PONs) employing erbium–ytterbium-doped fiber amplifier (EYDFA) [Formula: see text] Raman hybrid optical amplifier (HOA) using two modulation schemes — modified duobinary return to zero (MDRZ) and differential phase shift keying (DPSK) for alternate channels, where the channel count has been varied from 8 to 40. The system has been analyzed over the wavelength span of 1550–1558.8[Formula: see text]nm with a channel spacing, input power and data rate of 25[Formula: see text]GHz, 0[Formula: see text]dB and 40[Formula: see text]Gb/s, respectively. An average gain, gain ripple and optical signal-to-noise ratio (OSNR) of 20.87, 0.95 and 30[Formula: see text]dB, respectively have been observed in the case of HOA along with the achievement of Q-factor of up to 9 at the receiving end of the system. The DPSK-modulated channels result in higher values of gain and OSNR along with lower gain ripple as compared to MDRZ channels making the proposed system a good option for 5G access network applications.

FWM crosstalk reduction and performance investigation of SC-DWDM system employing ML techniques

This article presents a comprehensive approach towards mitigation of four-wave mixing (FWM) induced crosstalk for a super-combined dense wavelength division multiplexing (SC-DWDM) system with in-line erbium-ytterbium doped fiber amplifier (EYDFA) + Raman hybrid optical amplifier (HOA). The performance of modified duo-binary return to zero (MDRZ) and differential phase-shift keying (DPSK) modulation formats employed on alternate channels of the 40-channel system have been compared considering equal (ECSA) and unequal channel spacing allocation (UECSA) schemes at a data rate of 40 Gbps. In the case of the UECSA scheme, the DPSK modulated channels have shown a reduction of FWM crosstalk components and intensities of up to 80% and 40 dB, respectively at a low bit error rate (BER) of 2.5 × 10−14. Different artificial neural network (ANN) techniques have been compared for gain spectrum estimation of HOA has been carried out based on input features of channel spacing, the number of channels and wavelength. Levenberg-Marquardt's (LM) model proves to be the best fit as compared to other ANN techniques. The k-nearest neighbours (KNN), support vector machine (SVM) and decision tree (DT) algorithms have been applied for the estimation of impairments based on root mean square error (RMSE) and coefficient of determination (R2) values as performance metrics. The best-performing model results applying an ANN approach with predicted R2 values of quality - factor (Q-factor) and noise figure (NF) of 0.74 and 0.56, respectively.

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.

Performance Comparison of Different Modulation Formats for a 40 Gbps Hybrid Optical CDMA/DWDM System against ISI and FWM

This paper carries out a numerical simulation investigating three different modulation formats: carrier suppressed return to zero (CSRZ), modified duobinary return to zero (MDRZ) and return to zero (RZ). The purpose of this investigation is to find the optimum modulation format for the hybrid optical code division multiple accesses–dense wavelength division multiplexing (optical CDMA/DWDM) system with the implementation of an electro-optic phase modulator (EOPM) at a data rate of 40 Gbps per channel, with a transmitted power of 22 dBm and transmission distance of 105.075 km. The results revealed that CSRZ was superior to MDRZ and RZ and was more tolerant to optical fiber nonlinearity. Furthermore, unlike the DWDM systems, the performance of the proposed hybrid system based RZ format was better than the performance of MDRZ. Hence, the CSRZ modulation format is the best candidate for the optical CDMA/DWDM with EOPM module due to its high performance.

Fog attenuation penalty analysis in terrestrial optical wireless communication-modified duo-binary return-to-zero system with various receiver pointing errors

In metropolitan communication infrastructures a revolutionary technique is emerge known as terrestrial optical wireless communication (OWC), which makes a high-rise building connection is possible. Even with this solution, there are many other problems like the influence of haze and fog in the propagation channel which obstruct and scatter OWC propagation light and consequently led to a big attenuation, due to propagate in temporal, angular and spatial of the light signal. Not to mention the minimum visibility that discourages the implementation of the pointing errors (PE) and tracking system. This present work aims to analyze the interrelation between multiple scattering (dense fog, heavy fog, light fog, heavy haze and light haze) and receiver PE under modified duo-binary return-to-zero (MDRZ) system. We found that PE caused by beam swag is the main controlling factor and industriously minimize the link margin, signal-to-noise ratio (SNR), and raise the bit error rate (BER) when there is an increasing the turbulence strength and the track length. We recommended to guarantee transmitter– receiver alignment by installing a variable field of view (FOV) receiver (a tracking system) to overcome the scattering impact of the fog that make render urban laser communication effective in the presence of PE.

Performance analysis of wavelength division multiplexing MDM-PON system using different advanced modulations

Abstract Mode division multiplexing (MDM) is very competent next generation multiplexing technique and is becoming popular among researchers these days. In this research article, an integrated passive optical network (PON) using MDM and wavelength division multiplexing (WDM) is proposed at 25 Gbps over 3 km multimode fiber (MMF) link distance. For MDM, diverse Laguerre–Gaussian (LG) such as LG12, LG15, LG18, LG111 and LG114 are incorporated and also for cost reduction, vertical cavity surface emitting laser (VCSEL) is located in optical line terminal (OLT). Performance of diverse advanced modulations such as compressed spectrum return to zero (CSRZ), duo-binary return to zero (DRZ) and modified duo-binary return to zero (MDRZ) is evaluated and compared with non-return to zero (NRZ) in terms of Bit error rate (BER) at varied MMF link lengths. Results revealed that CSRZ performance stand out and NRZ provide worst performance.

Performance analysis of 1280 Gbps DWDM – FSO system employing advanced modulation schemes

In this work, we present a 1280 Gbps hybrid fiber + FSO system employing 32 channel dense wavelength division multiplexing (DWDM) and advanced modulation schemes. The system performance has been investigated by considering modified duobinary return-to-zero (MDRZ), duobinary return-to-zero (DRZ), and compressed spectrum return-to-zero (CSRZ) modulation formats under clear weather conditions. The effect of internal system parameters such as beam divergence, diameter of transmitter & receiver aperture has been analyzed in case of duobinary scheme as it outperforms the other two modulation formats. The performance of the proposed system has also been examined for different climatic turbulent conditions including rain, haze and fog weather conditions to predict the maximum range of transmission by employing duobinary modulation format. The received signal quality deteriorates below an unacceptable value in case of heavy fog, haze and rain weather conditions for the FSO range beyond 800 m, 1400 m and 1000 m respectively.

Estimating the Performance of Free Space Optical Communication in Rain Weather Conditions Using Various Models and Modified Duobinary Return to Zero Technique

Free space optical communication (FSO) system has remarkably gained importance of late due to the various advantages associated with it. However, before deployment of FSO communication system, an understanding of the laser beam scintillation due to the atmospheric as well as other weather-induced losses need to be understood. This paper mainly focuses on simulative performance analysis of an FSO system under rain conditions using Optisystems commercial software and rainfall data. Thus, the available models which are the Suriza, Carbonnea, Japan and Samir models were used to determine the rainfall-induced attenuation for a given rainfall rate. Unlike in the previous articles that only used on off keying as the modulation scheme at the transmitter, we have used modified duobinary return to zero (MDRZ) modulation. Further, to improve the MDRZ-based FSO performance in rain conditions, we have used the single-input multiple-output (SIMO) concept with equal gain combining (EGC) at the receiver and again proved that the improvement in BER, Q factor and received optical power suggests that MDRZ-based SIMO FSO communication results in a remarkable improvement.

Performance of Carrier- Suppressed Return-to-Zero(CSRZ), Duo binary Return-to-Zero(DRZ) and Modified Duo binary Return-to-Zero(MDRZ) Modulation Methods in WDM-PON Systems

In this paper the different modulation techniques used in fiber optic technology are compared to check which one has the better bit error rate (BER). There are a number of different modulation techniques used in WDN-PON systems but here the comparison is made among carrier-suppressed return-to-zero (CSRZ), duobinary return-to-zero (DRZ) and modified duobinary return-to-zero (MDRZ) modulation. The comparison to determine which is better is made my performing simulations in OptiSystem version 17 software. OptiSystem 17 is the current version of the software at the time the simulations were being carried out. In the OptiSystem software an optical fiber system is simulated from transmitter all the way to receiver. In the experiment when checking the performance of the different modulation formats, the optical fiber and the receiver are left unchanged and only the transmitter part is changed according to the modulation format being simulated at that particular instance. The modulation in the transmitter is done by using proper components from the OptiSystem library which when organized in the right order will give out a signal modulated in a certain format by the time it is fed into the optical fiber. Knowing the performance of modulation can help in WDM PON where the network gets to use passive components as it goes to user. Since no active amplification or correction equipment is used in WDM-PON, therefore using the format with the best performance can help with performance of overall system.

Optical carrier suppression with modified duo binary return to zero and polarization shift keying modulation schemes over free space communication system

Free space optical (FSO) communication has been a subject of interest for researcher and the corporate world since a few decades ago. This has been motivated by the huge benefits associated with this technology. Meanwhile, the generation and all optical up conversion of millimeter wave (mmw) for propagation in a FSO channel has been an important research direction. In this article, a single side band tone mmw generated by the optical carrier suppression (OCS) method has been modulated by modified duo-binary return to zero (MDRZ) and polarization shift keying (PolSK) modulated baseband data. The resulting optical signal was propagated in a FSO cannel subjected to combined weather and atmospheric turbulence induced fading. Later on, a comparative analysis was carried out between hybrid OCS/MDRZ and OCS/PolSK mmw signals propagated over free space. Using the performance metrics such as the bit error rate, quality (Q) factor and the received power among others, the simulation results indicated that hybrid OCS/MDRZ performs better than hybrid OCS/PolSK.

Analytical study of DWDM optical long haul network with symmetrical dispersion compensation

Objective: To design 40 Gbps ultra-dense wavelength division multiplexed (DWDM) optical network for 32 and 64 channels. Methods: Proposed DWDM architecture supports three different advance modulation schemes with symmetrical dispersion compensation unit. Performance of proposed work has been investigated using parameters bit error rate (BER) and quality factor. For efficient analysis, we employ variation in channel spacing, transmission length of fiber and input laser power, which is resulted into some significant observations. Findings: Carrier Suppressed Return to Zero (CSRZ) scheme exhibits a good quality factor with maximum achievable distance up to 4250 km due to highest tolerance to nonlinear effects. Modified Duobinary Return to Zero (MDRZ) modulation scheme also provides a good quality factor with laser power variation due to high receiver sensitivity, but with limited reach upto 2750 km. While Duobinary Return to Zero (DRZ) scheme provides moderate transmission coverage up to 3750 km in comparison to CSRZ and MDRZ, with a lesser quality factor due to effect of Inter Symbol Interference (ISI). We observe that an increase in number of simultaneous users through the channels results into performance degradation. Application: This work delivers very huge data rate and good spectral efficiency to sustain the current high traffic growth. Keywords: Dispersion, Long Haul System, Optical Network, Symmetrical Compensation, DWDM

Design And Analysis Of Ultra High Capacity DWDM System With And Without Square Root Module For Different Modulation Formats

In this paper, an ultra high capacity Inter satellite Optical Wireless Communication system (IsOWC) is simulated with and without square root module for different advanced modulation formats. The system is proposed by using 64 channels dense wavelength division multiplexing. For various input powers, the inter satellite link has been designed for external modulation of carrier suppressed return-to-zero(CSRZ), duo binary return-to-zero(DRZ), and modified duo binary return-to-zero(MDRZ) at different bit rate. The system is simulated without square root module at 10, 20 and 40Gbps and only at 40Gbps with square root module. The performance parameters Q-factor, eye diagram, received power are obtained for different bit rates to decide which modulation format is best. Results at 10 and 20Gbps shows that the CSRZ modulation performs better than the other two modulations but at 40Gbps MDRZ modulation performs the best. The results of previous system are only compared at 40Gbps with the new system which includes square root module and comparison shows that MDRZ still have the best performance but the performance of DRZ is very much enhanced as compared to without square root at 40Gbps.

Carrier Suppressed Return-to-Zero (CSRZ) and Modified Duobinary Return- to- Zero (MDRZ) Advance Optical Modulation Formats Analysis for Long Haul Rural Coverage

The rapid increase in the usage of data communication and data consuming devices demands higher data rate and reliable communication. In order to meet these demands new technologies are required which will be able to provide optimal quality of service and higher data rates. Next-Generation optical networks promise fast and flexible connectivity to resolve above challenging demands and can provide enough capacity for the next few years but the increase in data rate and transmission distance causes increase in dispersion. It occurs when different frequencies or mode of light in optical fiber are received by the terminals at different time and it increases, with an increase in fiber length. This is the major cause for breaking down quality of signal in optical fiber. Different modulation techniques are used to reduce the effect of dispersion, and improve the performance of the optical system. In this work, Performance of Carrier Suppressed Return-to-Zero (CSRZ) & Modified Duobinary Return-to-Zero (MDRZ) Advance Optical Modulation Formats are investigated in terms of Eye Height, Bit Error Rate (BER) and Quality Factor at 2Gbps for two different lengths of fiber in Optisystem. It found that MDRZ gives dispersion less transmission and less BER for long distance transmission.

Carrier Suppressed Return-to-Zero (CSRZ) and Modified Duobinary Return- to- Zero (MDRZ) Advance Optical Modulation Formats Analysis for Long Haul Rural Coverage

The rapid increase in the usage of data communication and data consuming devices demands higher data rate and reliable communication. In order to meet these demands new technologies are required which will be able to provide optimal quality of service and higher data rates. Next-Generation optical networks promise fast and flexible connectivity to resolve above challenging demands and can provide enough capacity for the next few years but the increase in data rate and transmission distance causes increase in dispersion. It occurs when different frequencies or mode of light in optical fiber are received by the terminals at different time and it increases, with an increase in fiber length. This is the major cause for breaking down quality of signal in optical fiber. Different modulation techniques are used to reduce the effect of dispersion, and improve the performance of the optical system. In this work, Performance of Carrier Suppressed Return-to-Zero (CSRZ) & Modified Duobinary Return-to-Zero (MDRZ) Advance Optical Modulation Formats are investigated in terms of Eye Height, Bit Error Rate (BER) and Quality Factor at 2Gbps for two different lengths of fiber in Optisystem. It found that MDRZ gives dispersion less transmission and less BER for long distance transmission.

Ultra high capacity inter-satellite optical wireless communication system using different optimized modulation formats

In this paper, an ultra-high capacity inter-satellite optical wireless communication (OWC) system using different modulation is presented. The proposed system is achieved by using 64-channel dense wavelength division multiplexing (DWDM) by different modulation methods. The inter-satellite link has been designed for various distance and external modulation of carrier-suppressed return-to-zero (CSRZ), duo binary return-to-zero (DRZ) and modified duo binary return-to-zero (MDRZ) at different bit rate. The proposed system is simulated at different bit rates, 10, 20 and 40 Gbps by using atmosphere model. To show the good performance of the proposed system, its eye diagram, received power and Q-factor are shown. The comparative analyses show that at 10 and 20 Gbps, the proposed system has maximum quality factor, Q, and minimum bit error rate (BER) for all three modulations. Also, at 40 Gbps the MDRZ modulation has better performance in comparison to the CSRZ and DRZ modulations.

Performance Analysis of DWDM System for Different Modulation Schemes Using Variations in Channel Spacing

AbstractThis paper reflects the analytical study of dense wavelength division multiplexed optical network with different number of channels at various channel spacing in order to achieve higher data rates by means of few advanced modulation schemes. Bit error rate and quality factor are being analyzed with the variation in number of channels, channel spacing and transmission length of fiber. Advanced modulation schemes being compared here are carrier suppressed return to zero (CSRZ), duobinary return to zero (DRZ), modified duobinary return to zero (MDRZ), 33 % differential phase shift keying (33 % DPSK), 66 % DPSK and differential quaternary phase shift keying (DQPSK). It is keenly observed that CSRZ scheme with 100 GHz channel spacing serves best performance in terms of max. Q factor, min. BER and maximum transmission coverage upto 4,000 km for 16 and 32 channels DWDM system since CSRZ is high tolerant to nonlinear effects. On the other hand, MDRZ scheme with 75 GHz channel spacing exhibits transmission coverage upto 4,000 km and 4,500 km for 16 and 32 channels respectively, but with degraded signal due to effect of inter symbol interference (ISI).