Duobinary Coding Research Articles

Design and Performance Analysis of DWDM-PON

This paper presents on the design and analysis of Dense Wavelength Division Multiplexing Passive Optical Network (DWDM-PON) which is the upcoming trend technology nowadays to transmit up to 40 Gbps data. Various modulation techniques such as Non-Return Zero (NRZ), Return-Zero (RZ) and duo binary coding are simulated in this DWDM-PON. Using OptiSystem software, DWDM-PON is designed and simulated for 32 channels with spacing of 100 GHz and bit rate of 10 Gbps. An Erbium Doped Fiber Amplifier (EDFA) and Dispersion - Compensating Fiber (DCF) is deployed in the DWDM design. It is found that duo binary modulation technique gives the best performance with minimum BER of 2.66x10-19. From the simulation result, it also found that the proposed DWDM PON design is suitable to be deployed for current network.

A 1.792 Tbps RoF-based PDM-DQPSK DWDM system for high-capacity long-haul 5 G and beyond optical network

This article proposes a high-capacity, cost-effective, and reliable transceiver system for 5 G and beyond optical communication. The system uses differential quadrature phase-shift keying (DQPSK), carrier-suppressed non-return-to-zero (CSNRZ) modulation, duobinary coding, radio over fiber (RoF), and dense wavelength division multiplexing (DWDM) techniques to improve the system’s efficiency. The RoF technology has been implemented using a 3.5 GHz radio frequency in compliance with 3GPP, IEEE, and ITU standards for 5 G communication. The performance of the proposed system has been analyzed using numerical methods in terms of constellation diagram, eye diagram, bit error rate (BER), optical signal-to-noise ratio (OSNR) requirement, and receiver sensitivity. 1.792 Tbps maximum data rate has been achieved in the simulation analysis using the 64-channel DWDM technique. Erbium-doped fiber amplifier (EDFA) compensates for signal attenuation, and dispersion compensating fiber (DCF) compensates for dispersion in a multi-span transmission link. The maximum transmission distance has been extended up to 1600 km at a BER of 10−12. The proposed system shall support high transfer rates and reliable connectivity requirements of 5 G and beyond networks.

PERFORMANCE EVALUATION OF HIGH DATA RATE OPTICAL COMMUNICATION SYSTEM UTILIZING FBG COMPENSATED DISPERSION SCHEMES UNDER DIFFERENT MODULATION TECHNIQUES

In this paper, comparative study of three dispersion compensation fiber models, namely, pre, post and symmetrical involving ideal dispersion compensation fiber Bragg grating for three different modulation schemes in 40 Gb/s single channel optical fiber transmission system are performance evaluated. Three modulation schemes, different namely, duo-binary coding, modified duo-binary and carrier suppressed return to zero are simulated and analyzed in terms of Q-factor and bit error rate for each set up by range of CW laser power. The simulation of optical system based on optisystem-10.The result report that the symmetrical with ideal FBG at duo-binary coding depicts good performance for increasing the input power from-5 dBm to 10 dBm. It is clear that best Q value obtained is 28.24 dB for BER of 5.9 ×10-176 at input power of 5 dBm using symmetrical compensation cascaded with ideal FBG for duo-binary modulation scheme.

Investigation of Influence of Mixed Configurations on Performance of WDM-PON

This paper aims at assessing of implementation of the concept of mixed systems in wavelength-division-multiplexing passive optical networks (WDM-PONs). At the first stage, the authors evaluate performance of two equal-channel transmission systems with non-return-to-zero (NRZ) and duobinary (DB) coding in terms of Q-factor, minimal channel spacing and supported data rate. At the second stage, two configurations of mixed transmission systems are proposed. The system with unequal channel spacing and multiple modulation formats (MMFs) as well as the system with mixed line rates (MLRs) and MMFs are investigated. The obtained results reveal that the impact of implementation of both systems is positive and concept of mixed transmission system can be considered as a potential solution for the increase of spectral efficiency (SE) of WDM-PON transmission system.DOI: http://dx.doi.org/10.5755/j01.eie.23.2.18003

Intercarrier interference reduction in MC-CDMA system through second order duobinary coded phase rotated conjugate cancellation scheme.

Multi-carrier code division multiple access (MC-CDMA) technique is one of the strong candidates for next generation wireless mobile communication systems. Multi-carrier systems are very much sensitive to carrier frequency offset (CFO) results in intercarrier interference (ICI). To mitigate ICI without any spectral loss, a second order duobinary coded phase rotated conjugate cancellation algorithm is proposed in this paper. In the conventional phase rotated conjugate cancellation (PRCC) technique, one path carries the MC-CDMA signal with a phase spin of ϕ and the other path carries the conjugate of the first path signal with -ϕ phase spin. This artificial phase rotation allows the transmitter to tune the transmitted signals so that the ICI effects could be mutually cancelled at the receiver. Although the PRCC technique reduces the spectral efficiency, the limitation can be overcome by the joint second order duobinary coding scheme with PRCC technique. In the proposed method, the correlative coding between the binary symbols modulated on adjacent subcarriers is used to reduce the ICI without any spectral loss. Simulation results show that the proposed PRCC method provides better carrier to interference ratio (CIR) and bit error rate (BER) performances compared to the conventional conjugate cancellation (CC) technique.

A High Speed and Ultra Long-Haul Radio-Over-Fiber System Employing Dual Photoelectric Arms Coherent Modulation and Optical Duo-Binary Coding

A novel high speed and ultra long-haul radio-over-fiber (ROF) system based on Dual Photoelectric Arms Coherent Modulation (DPACM) and Optical Duo-Binary Coding (ODBC) is proposed, and demonstrated. The signal spectrum bandwidth, generated by ODBC based on the first order DPACM, is half of non-return-to-zero (NRZ ) signal spectrum bandwidth. The secondary order DPACM generates a 40-GHz Millimeter-wave (mm-wave) that is transmitted over fiber (ROF). The simulation results show that, the bit rate can be up to 40 Gbps and the transmission distance is over 1500 Km, based on the ROF system with a 0 dBm continuous-wave laser source, multiple stages Er-Doped Fiber Amplifier (EDFA), a standard single mode fiber (SSMF) with a dispersion of 17 ps/nm/Km and a attenuation of 0.2 dB/Km.

Improved dispersion tolerance of Miller coding by integrating duobinary coding

A Miller–Duobinary coding scheme is proposed to increase optical transmission distance by compressing the optical spectrum compared with that of Miller coding and thereby demonstrating much larger tolerance against fiber dispersion. In this modulation scheme we investigate the dispersion tolerance of this code and found it to be nearly twice that of Miller coding only by employing single photodetector at 1 dB power penalty. The transmission reach can further be extended for higher power penalty. The circuit complexity of the proposed scheme is comparable to traditional Duobinary coding. The dispersion tolerance of Miller–Duobinary code obtained at 3 dB power penalty is \(-971\) to \(+964\) ps/nm.

Comparison between Duobinary Filter and Delay-And-Add Technique of Duobinary Transmission in Fiber Optic Communication System

Binary code is a two level of bit sequence of 1 and 0. On the other side, Duobinary (DB) is a three- level code of 1, 0 and -1 levels. Using duobinary transmission instead of binary transmission, it can improve the system performance, bandwidth efficiency of output signal, average power of signal, noise and distortion ratio of output wave shapes. Duobinary encoding and decoding are used in a significant bandwidth reduction of MAC signals transmitted by high and medium power TV satellites and also used in fiber optic communication system. This paperis based on the the observationof generation performance and transmission of duobinary coding and simulation of a single channel (1550-nm) 90-km OC-192 link. In duobinary transmission, the duobinary encoding can be implemented either with a combination of a delay-and-add operation or with a duobinary filter. Duobinary filter reduces bandwidth , wavelength, noise and distortion and improves the eye diagram of the output signals than the delay-and-add circuit in duobinary transmission of optical communication system. Also in this paper circuit design, simulation and fabrication of a duobinary encoder and decoder circuit for data communication system are presented. Keywords: Duobinary transmission, Duobinary filter, Delay-and-add circuit, Optsim, Eye diagram.

Demonstration of a 40 Gb/s Wavelength-Reused WDM-PON Using Coding and Equalization [Invited

The wavelength-division-multiplexed passive optical network (WDM-PON) has been generally regarded as a promising solution to the next-generation access network that will be required to deliver services over 40 Gb/s. However, fiber dispersion often limits the capacity and reach of WDM-PONs. Compared with dispersion compensation fiber, which is bulky and expensive with significant power loss, digital signal processing is a more suitable way to mitigate chromatic dispersion in PONs. Furthermore, expense is a critical concern in the WDM-PON, due to its need for a large number of lasers and a complex wavelength control mechanism. One practical solution is to reuse the downstream (DS) signal as the carrier for the upstream (US) modulation. In this case, the residual DS signal after remodulation can seriously degrade US transmission. In addition, system performance can be deteriorated by the unwanted reflection as uplinks and downlinks share one wavelength. In this paper, we propose using modified duobinary (MD) coding in the DS to improve its dispersion tolerance and reduce the crosstalk between DS and US induced by remodulation and reflection. MD is a correlative level code that can reduce signal bandwidth and achieve DC balance. We demonstrate a 15 km WDM-PON delivering a 40 Gb/s MD-coded signal in the downlink and a 10 Gb/s on-off keying signal in the uplink. Compared with no coding, the maximal allowable extinction ratio of the DS signal (ERd) is improved by 4 dB. Moreover, the reflection tolerance of the uplink and downlink is enhanced by 5 and 4 dB, respectively. In addition, investigations on the use of different equalizers in the DS to further suppress fiber dispersion confirm that the superior performance of nonlinear equalization in MD-coded transmission and that the network reach can be extended to 25 km by a nonlinear decision feedback equalizer.

Joint Effect of MLSE and Receiver Filters Optimization on Dispersion Robustness of IMDD, DPSK, DQPSK, and Duobinary Modulation

We analyze the effectiveness of a 32-state maximum-likelihood sequence-estimation (MLSE) receiver on chromatic dispersion robustness of optical transmission based on several binary modulation formats: intensity modulation direct detection, differential phase-shift keying, and duobinary line coding. Multilevel differential quadrature phase-shift keying modulation is also analyzed using a four-state 2-bit/symbol joint MLSE processor. For all modulation formats, receiver filters are optimized together with the use of the MLSE technique.

Improving dispersion tolerance of manchester coding by incorporating duobinary coding

A Manchester-duobinary coding scheme is proposed to compact the optical spectrum compared with that using pure Manchester coding and thus demonstrate much larger tolerance against fiber dispersion. With this modulation format, the dispersion tolerance can be extended to nearly three times of that using pure Manchester coding. Dispersion tolerance of Manchester-duobinary is from -800 to +920 ps/nm at 2-dB power penalty

Reduction of laser modulation bandwidth requirement in FSK systems using duobinary coding and differential detection

The duobinary signalling concept is applied to direct frequency modulation of a semiconductor laser. The main goal is the achievement of a low-cost high bit-rate transmission with reduced modulation bandwidth requirement of the laser diode. The simulation and experimental work demonstrate a laser modulation bandwidth reduction of about 50%. The system exhibits a high tolerance against fibre nonlinear effects, up to 20 dBm, and phase noise, up to 170 MHz of linewidth at 10 Gbit/s.

INTEGRATED WIDE-BAND CMOS DUOBINARY TRANSMITTER FOR OPTICAL COMMUNICATION SYSTEMS

Inter symbol interference (ISI) caused by dispersion in optical fibers is the major limiting factor on the achievable data rate or transmission distance in high-speed fiber-optic interconnects1. Compared with optical-domain and other electrical-domain dispersion compensation methods, duobinary coding technology is used due to its higher spectral efficiency. In this paper, a monolithically integrated duobinary optical transmitter has be designed and fabricated in standard 0.18 μm CMOS technology. This transmitter consists of a duobinary encoder and a VCSEL driver. The master-slave D flip-flop structure is used to generate the wideband one bit delay which is important for the realization of duobinary signal. An open drain structure is used in VCSEL driver design to provide the higher current output in low supply voltage condition. This duobinary transmitter can operate up to 5 Gb/s with 20 mA current output. The current consumption is only 50 mA under 1.8 V supply voltage.

Experimental demonstration of 10-gb/s data format conversions between NRZ and RZ using SOA-loop-mirror

This paper describes the demonstration of a simple all-optical data format conversion scheme between return-to-zero (RZ) and nonreturn-to-zero (NRZ) that employs a semiconductor optical amplifier (SOA) in a nonlinear optical loop mirror. The format conversion has been performed between the most widely used data formats-NRZ and RZ formats. The format conversion scheme is based on gain variation by an intensity-dependent phase change in an SOA-loop mirror. The input data stream acts as a control signal that induces the phase differences between clockwise- and counterclockwise-propagating data inside an SOA-loop mirror. It is possible to change the data format of the output data stream by controlling the phase differences of the clockwise and counterclockwise pulse in an SOA-loop mirror appropriately. For the converted NRZ data from RZ data, 10-Gb/s error-free transmission up to 78 km over standard single-mode fiber has been obtained. By comparing the conventional NRZ transmission with the Mach-Zehnder modulation scheme, the proposed RZ-to-NRZ conversion shows an improved transmission performance. The NRZ-to-RZ conversion has clear eye openings up to 78 km. On the contrary, the conventional RZ binary data from a mode-locked laser has a nearly closed eye even at 52 km. The converted RZ data has a 2-dB conversion power margin to the injected NRZ data, which indicates an increase in the receiver sensitivity due to the signal format conversion. The improved transmission distance of the converted RZ signal is due to the duobinary coding effect of the SOA-loop mirror. The SOA has the possibility of high-speed operation over 40 Gb/s, and the SOA-loop mirror has the capabilities of format and wavelength conversions. Therefore, the SOA-loop mirror can be a universal building block in future all-optical networks. In addition, the proposed format conversion scheme can serve as an important format converter between the ultrafast optical-time-division-multiplexed networks and the lower line-rate wavelength-division-multiplexed networks.

Impact of Response Flatness on Duobinary Transmission Performance: An Optimized Transmitter With Improved Sensitivity

We study the effect of transmitter response amplitude and group delay ripples on the performance of systems using duobinary coding. We demonstrate an improved 10-Gb/s transmitter with very low required optical signal-to-noise ratio in back-to-back and transmission over about 4300 ps/nm (258 km of single-mode fiber at 1550 nm) with about 2-dB penalty (at bit-error rate BER=10/sup -3/).

A 1580-nm band WDM transmission technology employing optical duobinary coding

This paper reports 1580-nm band wavelength division multiplexed (WDM) transmission employing optical duobinary coding over dispersion-shifted fibers. By using the 1580 nm band, the generation of four-wave mixing (FWM) over dispersion-shifted fibers (DSFs) can he suppressed. Optical duobinary coding is dispersion-tolerant because of its narrow bandwidth, and enables the use of the conventional binary intensity modulated direct detection (IM-DD) receiver. First, comparisons are made for WDM transmission performance in the 1580-nm band between conventional binary nonreturn-to-zero (NRZ) coding with and without postdispersion compensation, and optical duobinary coding by computer simulation is described. From the numerical simulations, it is found that the optical duobinary coding has superior transmission performance to the conventional binary coding without any dispersion compensation, and that the difference in the transmission performance between two coding methods is very small even if postdispersion compensation at the optical receiver is applied to the NRZ coding method. Second, transmission performance between the conventional binary NRZ and the optical duobinary signals without any dispersion compensation is compared with the straight-line experiment over 500-km dispersion-shifted fiber. The experimental results reveal that the transmission distance with optical duobinary coding is doubled in comparison with that of the conventional binary NRZ signals. Finally, 16-channel, 10-Gb/s optical duobinary WDM signals in the 1580-nm band are successfully transmitted over 640 km (80 km/spl times/8) of DSF without any dispersion compensation or management.

Dispersion-compensation-free 16 × 10 Gbit/sWDM transmissionin 1580 nm band over 640 km of dispersion-shifted fibreby employing optical duobinary coding

16-channel, 10 Gbit/s optical duobinary WDM signals in the 1580 nm band are successfully transmitted over 640 km (80 km /spl times/8) of dispersion-shifted fibre with no dispersion compensation or management.

Relation between spectrum bandwidth and the effectsof chromatic dispersion in optical transmissions

The authors have shown numerically, and confirmed experimentally, that reducing the bandwidth of the sequence spectrum (as opposed to the pulse spectrum), for instance using a duobinary coding, does not necessarily improve the propagation through dispersive fibres.

A single-chip three-level regenerator IC for high-speed optical transmission systems applying duo-binary coding schemes

A three-level regenerator IC operating at 160 Mbit/s or more has been developed for high-speed optical transmission systems, such as local area network and computer links. It was a modified duo-binary class-II coding scheme and provides good performance for long-period pattern transients. Two decision circuits and a nonlinear timing extraction circuit consisting of 430 transistors and resistors are monolithically integrated on a single 2.5/spl times/2.5-mm/SUP 2/ chip using 3-/spl mu/m Si bipolar IC technology. The ICs are primarily designed for a 160-Mbit/s transmission bit rate, with a 1.2-1/24 mark ratio, a 5 V/spl plusmn/10% supply voltage, and 0-70/spl deg/C temperature range. The following characteristics are achieved: 5 mV decision sensitivity, +9.8/-7.8/spl deg/ static pattern jitter, /spl plusmn/7/spl deg/ timing phase shift, transition time of 0.95 ns, and power dissipation of less than 470 mW.