Duobinary Return To Zero Research Articles

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.

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.

Unequal channel spacing 8×5Gbps optical system utilizing different signal representations.

Data representations are important to communication networks; they convert the data bits into a signal form, which affects the system capacity, maximum bit rate, transmission distance, and different linear and nonlinear impairments. In this paper, we propose non-return-to-zero (NRZ), chirped NRZ, duobinary, and duobinary return-to-zero (DRZ) data representations with eight dense wavelength division multiplexing channels for transmitting a 5Gbps data rate through a 250km fiber length. The results of the simulation design are calculated at different equal and unequal channel spacings, and the quality factor is measured over a wide range of optical power. For equal channel spacing, the DRZ has a preferable performance with a 28.40 quality factor at 18dBm threshold power, and the chirped NRZ has a preferable performance with a 26.06 quality factor at 12dBm threshold power. For unequal channel spacing, the DRZ has a 25.76 quality factor at 17dBm threshold power, and the NRZ has a 25.06 quality factor at 10dBm threshold power.

Design of Broadband Passive Optical Network Incorporating Different Modulation Formats and Colorless ONUs

In this work, a bidirectional broadband passive optical network (BPON) is proposed at 622.08 Mbps by incorporating colorless optical network units and different pulse shapes such as Duo-binary return to zero (DRZ), return to zero (RZ) and non-return to zero (NRZ). For varied link lengths, launching powers in terms of log BER, and Quality factor for downstream and upstream, the design of BPON is examined. The duo-binary advanced pulse shape outperformed the others in bidirectional BPON, achieving a symmetrical distance of 25 kilometres.

Investigation of WDM-MDM PON employing different modulation formats

Advancement in the technology and optical communication sector has led to an increase in the demands of high bit rate and bandwidth, required for reliable data transmission. To meet such demands, future generation optical networks came into existence. In this paper, we propose a 100 Gbps, 4-channel WDM-MDM PON with two input wavelengths of 1550 nm and 1555 nm and using LP 01 and LP 11 modes. The system performance has been analyzed for different internal parameters considering return-to-zero (RZ), non-return-to-zero (NRZ), alternate mark inversion (AMI) and duobinary return-to-zero (DRZ) modulation schemes. DRZ modulation outperforms the other encoding schemes resulting in achievement of an acceptable bit error rate (BER) of ≤ 10−14 over 10 km of fiber length at a 25 Gbps data rate.

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.

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.

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.

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).

Simulation of high capacity 40 Gb/s long haul DWDM system using different modulation formats and dispersion compensation schemes in the presence of Kerr's effect

In this paper, simulative analysis of 40 Gb/s long haul (500–2000 km) DWDM system with ultra high capacity upto 1.28 Tb/s has been carried out for carrier-suppressed return-to-zero (CSRZ), duobinary return-to-zero (DRZ) and modified duobinary return-to-zero (MDRZ) modulation formats. The DWDM system has been analyzed for the pre, post and symmetrical dispersion compensation schemes for 16 Channels with 25 GHz channel spacing in order to find the optimum modulation format for a high bit rate optical transmission system. The effect of variation in input power and transmission distances is observed in terms of Q value and eye opening for various formats. It is found that symmetrical compensation is superior to pre and post dispersion compensation schemes. It has also been observed that the performance of DWDM system is severely limited by the four-wave mixing (FWM) effect and is determined that MDRZ format seems to be the best choice for the transmission distance beyond 1550 km despite slightly more complex transmitter and receiver configuration. Further, symmetrical compensation scheme has been investigated for 32×40 Gb/s MDRZ format for faithful transmission over 1450 km.

Reduction of pulse-to-pulse interaction using alternative RZ formats in 40-Gb/s systems

We show that pulse-to-pulse interaction at 40 Gb/s can be reduced by alternating the optical phase of adjacent bits by using either a modified-duobinary return-to-zero (RZ) modulation format or RZ with alternating phase. Also, the generation of ghost pulses can be greatly suppressed using the modified-duobinary and duobinary RZ format.