Duobinary Modulation Formats Research Articles

Investigation Of Fwm Effect On Ber In Wdm Optical Communication System With Binary And Duobinary Modulation Format

This paper simulates two channel WDM optical communication system to investigate the effect of FWM on Bit Error Rate for Duo-binary & binary modulation like NRZ Rectangular at different dispersion value ,core effective area of fiber & channel spacing for 100km long optical communication system. BER got improved with duobinary modulation format & by increasing core effective area which will offer a significant performance benefit in digital systems.

Quadrature Duobinary for High-Spectral Efficiency 100G Transmission

This paper proposes and analyzes a quadrature duobinary modulation format with coherent detection for high-spectral efficiency wavelength-division-multiplexing transmission systems at 112 Gb/s per channel. A practical system design of a dual polarization quadrature duobinary (DP-QDB) format with coherent heterodyne detection is analyzed and compared with the DP-differential quadrature phase-shift keying format for feasibility of 112 Gb/s transmission. Using simulation analysis, we show that the relatively narrow spectrum of quadrature duobinary modulation provides an effective practical means for realizing high-spectral efficiency transmission, approaching the theoretical limit of 4 bits/s/Hz, while also providing excellent tolerance to optical filter cascades for a robust optical networking functionality.

New Branch Metrics for MLSE Receivers Based on Polarization Diversity for PMD Mitigation

In this paper, we analyze the performance of polarization-diversity receivers employing maximum-likelihood sequence estimation (MLSE) to combat the effects of polarization mode dispersion (PMD) for both the intensity-modulation direct detection (IMDD) and duobinary modulation formats at 43 Gb/s. We propose and study several parametric branch metrics, showing that the use of MLSE receivers based on polarization diversity with appropriate branch metrics allows to cancel out the high penalty incurred by standard MLSE receivers in the presence of PMD.

Transmission Performance of 40 Gb/s PM Duobinary Signals due to Fiber Nonlinearities in DWDM Systems Using VSB Filtering Techniques

We investigate theoretically the tolerance of 40 Gbps phase-modulated (PM) duobinary signals using a vestigial sideband (VSB) filter on impairments which occurred in dense wavelength-division multiplexing (DWDM) systems, compared to the conventional duobinary signals. Our simulation results show that PM duobinary signals can't have the gain on the spectral efficiency achieved by utilizing the VSB filtering technique. In order to increase the spectral efficiency, they indispensably require to be transmitted at the optimum bandwidth of multiplexer (MUX) and demultiplexer (DEMUX) since they are susceptible to inter-channel crosstalk. It is also shown that the PM duobinary modulation format has a large tolerance on self-phase modulation (SPM) and cross-phase modulation (XPM) under the condition which MUX and DEMUX have been tuned at an optimum bandwidth; it has 1.2 dB power penalty at the fiber launching power (FLP) of 15 dBm and the channel spacing of 50 GHz.

107 Gb/s uncompensated transmission over a 470 km hybrid fiber link with in-line SOAs using MLSE and duobinary signals

We experimentally demonstrate uncompensated 8-channel wavelength division multiplexing (WDM) and single channel transmission at 10.7 Gb/s over a 470 km hybrid fiber link with in-line semiconductor optical amplifiers (SOAs). Two different forms of the duobinary modulation format are investigated and compared. Maximum Likelihood Sequence Estimation (MLSE) receiver technology is found to significantly mitigate nonlinear effects from the SOAs and to enable the long transmission, especially for optical duobinary signals derived from differential phase shift keying (DPSK) signals directly detected after narrowband optical filter demodulation. The MLSE also helps to compensate for a non-optimal Fabry-Perot optical filter demodulator.

Optical transmission of variable-pulse-width alternating-phase duobinary modulation: MATLAB Simulink simulation and comparison with carrier-suppressed return-to-zero amplitude-shift-keying experimental transmission

Abstract. Transmission in a 40-Gbit/s alternating-phase 0 and duo-binary modulation format with 67%, 50%, and 33% pulse width modu-lation duobinary carrier suppression CS and carrier maximum pulsecarving is demonstrated. A minimum 136-ps/nm dispersion tolerancecan be achieved at this transmission rate.At least 5- and 1.2-dB receiversensitivity improvements are achieved for CS return-to-zero RZ 67%and 50% duobinary modulation, respectively, as compared with the ex-perimental measurement under CS RZ differential phase-shift keyingtransmission over a 320-km three-span optically amplified dispersion-compensated standard single-mode fiber system. A MATLAB Simulinkplatform is described for simulation of the transmission performance. © 2008 Society of Photo-Optical Instrumentation Engineers. DOI: 10.1117/1.2957965 Subject terms: optical communications; modulation formats; duobinary;modulation . Paper 080186 received Mar. 8, 2008; accepted for publication Apr. 28, 2008;published online Jul. 22, 2008.

Modeling of Coherent and Incoherent Rayleigh Crosstalk in Conventional Optical Links

Performance of Rayleigh-dominated transmission is modeled using approximated and exact noise power spectral densities (PSDs) and results are compared to experimental measurements for nonreturn-to-zero, return-to-zero, and duobinary modulation formats. Both models accurately predict penalties associated with coherent Rayleigh crosstalk for all three formats with typical accuracy within 1 dB. For incoherent Rayleigh crosstalk, the numerical model using exact PSDs improves prediction accuracy by as much as 4 dB over the analytic model. The large, previously unexplained disagreement is attributed to the set of analytic approximations. Our results indicate that a rigorous description of the channel spectrum should be used when calculating impairments caused by incoherent Rayleigh crosstalk, particularly in very dense wavelength-division-multiplexed systems requiring a narrow optical filtering.

On the Decision-Feedback Equalizer in Optically Amplified Direct-Detection Systems

This paper investigates the combined feed-forward and decision-feedback equalizer (DFE) in a lightwave system with optical amplifiers and a direct-detection receiver. Based on a nonlinear channel model, the paper provides a modification of the classical minimum mean square error theory of the DFE. Furthermore, an analytical method that is capable of accurate bit error rate (BER) evaluation is used to optimize the DFE for minimum BER. The paper evaluates the DFE performance for both optical ON-OFF keying and duobinary modulation formats in the presence of chromatic dispersion as well as the DFE performance for the mitigation of higher order polarization mode dispersion in first-order compensated systems. The paper shows that the DFE can compensate for the BER degradation due to narrow-band receiver-side optical filtering and can significantly improve the spectral efficiency of dense wavelength-division multiplexed systems.

Investigation of Interplay between Driving Voltage of MZ Modulators and Bandwidth of Low-pass Filters in Duobinary Modulation Formats

We have theoretically investigated the effects of the interplay between the driving voltage of Mach-Zehnder (MZ) modulators and the bandwidth of low-pass filters (LPF) in 10[Gb/s] duobinary modulation systems. For the change of driving voltage ratios(driving voltage/ switching voltage), the transmission performance has been evaluated over 200[㎞] of single-mode fiber(SMF) systems. For driving voltage ratios with smaller than 100[%], the transmission performance has been maintained and greatly affected by the bandwidth of LPFs than the driving voltage. For driving voltage ratios with larger than 100[%], the transmission performance has been degraded and is not sensitive to the bandwidth of LPFs. To see the limitation of driving voltage, we have reduced the driving voltage ratio to 50[%]. Our results suggest that 10[Gb/s] duobinary signals with driving voltage ratio with smaller than 100[%] have been transmitted over 200[km] SMF within 2[㏈] power penalty without dispersion compensation. For the driving voltage ratio with 50[%], we have verified that the transmission performance was maintained.

Comparison between NRZ and duobinary Modulation at 43 gb/s for MLSI-based and DCF-based transmission systems

In this paper, the performance of midlink spectral inversion (MLSI) is compared with the performance of conventional dispersion compensation fiber (DCF)-based transmission for two data formats: 43-Gb/s ON-OFF keying nonreturn-to-zero (OOK-NRZ) and 43-Gb/s duobinary. In the MLSI-based system, a polarization-diverse subsystem was used for spectral inversion employing magnesium-oxide-doped periodically poled lithium niobate (PPLN) waveguide technology. The transmission link consists of 8 /spl times/ 100 km standard single-mode fiber (SSMF) using erbium-doped fiber amplifiers (EDFAs) for amplification. Compared to the DCF-based system, it is seen that the MLSI-based configuration enhances the dispersion tolerance for both the NRZ and the duobinary modulation formats. It is concluded that the combination of the MLSI and the duobinary modulation format yields a highly dispersion-tolerant stable 43-Gb/s transmission system.

Experimental measurements of uncompensated reach increase from MLSE-EDC with regard to measurement BER and modulation format

Comprehensive experimental measurement data are presented comparing the performance of an optical receiver with MLSE-EDC technology against a standard receiver for signals with uncompensated chromatic dispersion. Signals with the NRZ and duobinary modulation formats are investigated. We find that the MLSE-EDC technology provides greater uncompensated reach advantage for both formats as the allowable measured BER is increased, demonstrating the EDC technology has greatest effect and application in conjunction with strong forward error correction. We also measure signal quality vs. dispersion with constant OSNR and draw similar conclusions along with further insights into the application space of the EDC technology for both modulation formats.

Improvement of Power Margin in 10-Gb/s SOA-Boosted Transmission Systems Using Phase-Modulated Duobinary Modulation Formats

We theoretically investigate the performance of 10-Gb/s semiconductor optical amplifier (SOA)-boosted transmission systems using the nonreturn-to-zero (NRZ), conventional duobinary, and phase-modulated (PM)-duobinary modulation formats. NRZ and conventional duobinary modulation formats are based on the intensity modulation. When the NRZ and conventional duobinary modulation formats are used, the nonlinear characteristics of SOA severely distort the signals. On the other hand, the PM-duobinary modulation format is based on differential binary phase-shift-keying modulation. When the PM-duobinary modulation format is employed, the nonlinear characteristics of SOA scarcely affect the signals which maintain a constant intensity in SOAs. Using the PM-duobinary modulation format, we can significantly improve the power margin in SOA-boosted transmission systems.

Improved polarization-mode-dispersion tolerance in duobinary transmission

Polarization-mode-dispersion tolerance of a low-pass filter duobinary modulation format is investigated. With the optimum residual dispersion, the optical signal-to-noise ratio penalty at a differential group delay of 40 ps is measured to be 1 dB (at BER=6/spl times/10/sup -5/): 1.5 dB less than that without residual dispersion in a 10.7-Gb/s duobinary transmission. Numerical simulations show reasonable agreement with the experimental results.