Mitigation of nonlinear transmission effects for OFDM 16-QAM optical signal using adaptive modulation (original) (raw)
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Adaptive performance improvement of OFDM radio over fiber systems
2007
Nonlinear distortion due to large peak to average power ratio is a major concern with OFDM systems. In this paper, we present an efficient adaptive modulation technique to mitigate nonlinear distortion effects of OFDM radio signals transmitted over optical fiber (Radio-over-Fiber: ROF). First, we modulate all subcarriers at primary (high) level. Then we identify the subcarriers with high distortion and appropriately reduce the modulation level on those subcarriers to secondary levels. This is done at the transmitter side for each OFDM symbol. This procedure is repeated until the nonlinear distortion is below a predetermined threshold. This technique is shown to improve the BER performance considerably while the reduction in data rate for a system with 64 subcarriers and 16 QAM as primary and 4 QAM as secondary modulation levels is around 4%.
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IEEE/OSA Journal of Lightwave Technology, 2009
We theoretically investigate the performance limitations of subcarrier multiplexed (SCM) wavelength-division-multiplexing (WDM) systems using optical double-sideband (DSB) modulated, 16-quadrature amplitude-modulated (QAM) signals. The performance limitations are investigated using crosstalk power and SCM channel spacing for various transmission conditions, including impairment factors such as dispersion and fiber nonlinearities for a single wavelength channel first. The effects of WDM channel spacing on SCM systems with multiwavelength channels are also evaluated via the calculated bit error rate (BER) performance, based on the performance limitations found in the single-wavelength simulation. This enables us to provide guidelines for the design of SCM/WDM systems for fiber-to-the-home (FTTH) network in WDM-passive optical network (PON) architecture, based on the performance limitations.
An efficient modulation technique to mitigate nonlinearities in optical OFDM
2014 Australasian Telecommunication Networks and Applications Conference (ATNAC), 2014
The optical OFDM (O-OFDM) system is a growing technology for next generation high-speed optical communication. Two types of O-OFDM; CO-OFDM (Coherent-Optical OFDM) and Direct-current-based optical OFDM (DC-OFDM) are discussed. Mach-Zehnder modulators (MZMs) are used in up-converter part of CO-OFDM system to convert the RF signal to optical signal when the light cannot directly modulate for higher speed. The MZM has a cosine behavior with high nonlinear characteristic that affects the system performance. This paper aims to investigate an efficient pulse modulation technique for mitigating nonlinearity effect in the Mach-Zehnder modulator of CO-OFDM system. It also highlights the proposed method, an efficient CO-OFDM system to solve the existing nonlinearity issue. This technique influences positively on OSNR to reduce non linearity over different distances of optical channel and improve the system performance in terms of power consumption and bandwidth efficiency.
Adaptive Modulation for OFDM Systems
The goal for the fourth generation (4G) of mobile communications system is to seamlessly integrate a wide variety of communication services such as high speed data, video and multimedia traffic as well as voice signals. One of the promising approaches to 4G is adaptive OFDM (AOFDM). In AOFDM, adaptive transmission scheme is employed according to channel fading condition with OFDM to improve the performance. In this paper, we have considered only adaptive modulation. First we have investigated the OFDM system performance of uncoded adaptive modulation using quadrature amplitude modulation (QAM) and phase shift keying (PSK). To further enhance the system, we employ convolutional coding to OFDM system. The obtained results show that a significant improvements in terms of bit error rate (BER) and throughput can be achieved demonstrating the superiority of the adaptive modulation schemes compared to fixed transmission schemes.
OFDM/OQAM PERFORMANCES FOR HIGH SPEED OPTICAL COMMUNICATION IN LONG HAUL FIBER OVER 1600 Km
IAEME PUBLICATION, 2014
Orthogonal Frequency Division Multiplex (OFDM) is a high-speed digital communication technique which presents a big potential as an ideal solution for high-speed transmission in optical fiber networks. This study shows the OFDM modulation associated with Offset Quadrature Amplitude Modulation (OQAM) that is filtered using an analysis and synthesis filter banks in an optical communication platform at the rate of 10 GB/s over 1600 Km using a single mode fiber (SMF). The simulations are performed in the VPI Photonics software environment. The results show that the filtered OFDM/OQAM provides better transmission performance than the classical OFDM/QAM firstly because it does not require equalization to certain distances; secondly distances are greater than those achieved with the conventional OFDM in similar studies. Making some changes in the filter banks parameters improves significantly the performance of the system. The bandwidth is maximized because we do not use the cyclic prefix (CP) in OFDM/OQAM. Moreover the complexity of transmitters and receivers can be reduced, which shows OFDM/OQAM as an effective solution to combat the effects of the chromatic dispersion (CD), the polarization mode dispersion (PMD), the inter-symbol interference (ISI) and nonlinearities.
Nonlinear Effects Mitigation in Coherent Optical OFDM System in Presence of High Peak Power
Journal of Lightwave Technology, 2000
The nonlinear effects of Mach-Zehnder modulator (MZM) and self phase modulation (SPM), in optical orthogonal frequency division multiplexing (OFDM) under the presence of high peak power is studied. A full coherent optical communication system is presented and analyzed. Standard method to reduce the peak to average power ratio (PAPR) values combined with improved technique to mitigate the nonlinear effect, by means of optimized digital pre-distortion, is analyzed and a full performance analysis is presented.
Nonlinearity Mitigation in Im / DD Optical Ofdm Using New SLM Scheme
2019
Optical orthogonal frequency-division multiplexing (O-OFDM) systems have received a great deal of attention as a transmission technology for high-capacity long-haul optical transport networks. However, it is also very sensitive to nonlinear effects due to high peak to average power ratio (PAPR) problem as conventional OFDM system. This paper proposes Fast Hartley based selective mapping with Riemann Sequence for PAPR reduction in IM/DD Optical OFDM system. Results show that the proposed method performs better in terms of PAPR and bit error rate performance and it is less complex than other conventional methods.
Optics express, 2014
In this work we experimentally investigate the improved intra-channel fiber nonlinearity tolerance of digital subcarrier multiplexed (SCM) signals in a single-channel coherent optical transmission system. The digital signal processing (DSP) for the generation and reception of the SCM signals is described. We show experimentally that the SCM signal with a nearly-optimum number of subcarriers can extend the maximum reach by 23% in a 24 GBaud DP-QPSK transmission with a BER threshold of 3.8 × 10(-3) and by 8% in a 24 GBaud DP-16-QAM transmission with a BER threshold of 2 × 10(-2). Moreover, we show by simulations that the improved performance of SCM signals is observed over a wide range of baud rates, further indicating the merits of SCM signals in baud-rate flexible agile transmissions and future high-speed optical transport systems.