Phase noise influence in long-range coherent optical OFDM systems with delay detection, IFFT multiplexing and FFT demodulation

We present a study of the influence of dispersion induced phase noise for CO-OFDM systems using FFT multiplexing/IFFT demultiplexing techniques (software based). The software based system provides a method for a rigorous evaluation of the phase noise variance caused by Common Phase Error (CPE) and Inter-Carrier Interference (ICI) including - for the first time to our knowledge - in explicit form the effect of equalization enhanced phase noise (EEPN). This, in turns, leads to an analytic BER specification. Numerical results focus on a CO-OFDM system with 10-25 GS/s QPSK channel modulation. A worst case constellation configuration is identified for the phase noise influence and the resulting BER is compared to the BER of a conventional single channel QPSK system with the same capacity as the CO-OFDM implementation. Results are evaluated as a function of transmission distance. For both types of systems, the phase noise variance increases significantly with increasing transmission distance. For a total capacity of 400 (1000) Gbit/s, the transmission distance to have the BER < 10-2 for the worst case CO-OFDM design is less than 800 and 460 km, respectively, whereas for a single channel QPSK system it is less than 1400 and 560 km

Performance analysis of OFDM technology on radio-over-fiber systems

Dissertação de mest., Engenharia Eletrónica e Telecomunicações, Faculdade de Ciências e Tecnologia, Univ. do Algarve, 2011Nowadays, the demand for high speed, high quality and diversity in distributed services presents a challenge for telecommunication technology. Wireless systems provide the accessibility to end-user, but are not the solution for long distance links. Currently, the ideal technology for long-range transmissions at high data rates is optical fiber. Hence, a new concept for high capacity networks emerges, with centralized services into Base Stations (BS) engineered to provide flexibility and control over the system, and to perform operations such as electrical to optical domain conversion and modulation. Such Radio-over-Fiber (RoF) networks also appear as an attractive technology because they are efficient and cost effective. Orthogonal Frequency Division Multiplexing (OFDM) technology is widely used in a number of standards. For instance, it is actually the Multi-Carrier Modulation (MCM) technique applied in 802.11a/g/n wireless standards and in Digital Video Broadcasting-Terrestrial (DVB-T), among other prevailing systems, which makes this subject one particularly pertinent to study. OFDM systems are an appealing choice for waveform modulation, as they are very bandwidth efficient comparing to others MCM, and provide flexibility in data transmission rates. Additionally, an important advantage dwells in its natural robustness against severely interfering environments. In this thesis, fundamentals on OFDM technology are extensively described, and its application to wireless and optical fiber networks is introduced. The combined channel effects of these technologies on OFDM signals are investigated. In terms of performance analysis, this exposition focuses on understanding the importance of OFDM modulation parameters, and explores some OFDM signal properties. To achieve this, a simulator was implemented with Matlab to create arbitrary OFDM waveforms and emulate channel effects. This study also investigates the efficiency of OFDM technology over a real Radio Frequency (RF) system with an ideal communication channel. Finally, an experimental RoF configuration is implemented and its performance is assessed

Cost-effective optical transmission systems based on orthogonal frequency division multiplexing

Orthogonal frequency division multiplexing (OFDM)is becoming increasingly popular in optical fiber applications because as data rates increase, the computational requirements involved in electronic dispersion compensation for serial modulation formats become impractical. Some investigations explain that OFDM can be used for the electronic compensation of chromatic dispersion and polarization mode dispersion in single-mode optical fiber systems and for mode dispersion in multimode systems. The main goal of this Master thesis is to study on one hand the OFDM systems and on the other, the optical transmission systems and also the combination of the two: optical OFDM systems. A general classification of the present proposals for optical OFDM implementations is presented and two of the identified schemes, those which lead to more cost-effective solutions, have been studied in deeper detail. These are based on conventional Intensity Modulation and Direct Detection (IM/DD) optical transmission systems. The first system relies on a RF up-conversion stage prior to the optical intensity modulation that allows to modulate the real and imaginary parts of the optical OFDM signal into the phase and quadrature components of an RF frequency, while the second involves imposing the Hermitian symmetry among the subcarriers in order to obtain an OFDM signal which is purely real. Starting from a built in demo of the software called Virtual Photonics Inc. (VPI) a practical investigation about OFDM optical systems has been done. This demo is called Long Haul transmission and implements the RF up-conversion optical OFDM scheme. This demo is only an example restricted to a specific scenario and offers little flexibility. That is why a new VPI simulation setup has been created by exploiting the Matlab interface provided by VPI where the OFDM coding and decoding have been developed in Matlab code and can be adjusted and modified to any scenario. Additionally, another VPI simulation setup has been developed which allows to impose the Hermitian symmetry among the subcarriers allowing for the obtention of a purely real OFDM signal to be directly Intensity modulated over an optical carrier. Results and comparisons of the outcome of both, our simulation setups and the VPI demo, are presented showing good agreement. Moreover, our setups have incorporated several improvements based on the investigation of optical OFDM systems carried out. Also, the functionalities of the software have been exploited to come out with user-friendly setups that allow any researcher in the field to carry out advanced simulations with little effort

Single-Laser Multi-Terabit/s Systems

Optical communication systems carry the bulk of all data traffic worldwide. This book introduces multi-Terabit/s transmission systems and three key technologies for next generation networks. A software-defined multi-format transmitter, an optical comb source and an optical processing scheme for the fast Fourier transform for Tbit/s signals. Three world records demonstrate the potential: The first single laser 10 Tbit/s and 26 Tbit/s OFDM and the first 32.5 Tbit/s Nyquist WDM experiments

Single-Laser Multi-Terabit/s Systems

Optical communication systems carry the bulk of all data traffic worldwide. This book introduces multi-Terabit/s transmission systems and three key technologies for next generation networks. A software-defined multi-format transmitter, an optical comb source and an optical processing scheme for the fast Fourier transform for Tbit/s signals. Three world records demonstrate the potential: The first single laser 10 Tbit/s and 26 Tbit/s OFDM and the first 32.5 Tbit/s Nyquist WDM experiments

Digital Adaptive Carrier Phase Estimation in Multi-Level Phase Shift Keying Coherent Optical Communication Systems

The analysis of adaptive carrier phase estimation is investigated in long-haul high speed n-level phase shift keying (n-PSK) optical fiber communication systems based on the one-tap normalized least-mean-square (LMS) algorithm. The close-form expressions for the estimated carrier phase and the bit-error-rate floor have been derived in the n-PSK coherent optical transmission systems. The results show that the one-tap normalized LMS algorithm performs pretty well in the carrier phase estimation, but will be less effective with the increment of modulation levels, in the compensation of both intrinsic laser phase noise and equalization enhanced phase noise.Comment: 5 pages in [IEEE] International Conference on Information Science and Control Engineering (ICISCE) 2016. arXiv admin note: text overlap with arXiv:1602.0685