Development of OFDM in WDM- Radio over fiber access network

Radio over Fiber (RoF) is one of the latest technologies in optical communication systems that provide effective convergence of optical and wireless access network system. RoF is a technology whereby light is modulated by a radio signal and transmitted over an optical fiber link to facilities wireless access. Wavelength�Division Multiplexing (WDM) is a multiplexing technique for fiber optic system to multiplex a number of optical carrier signals onto a single-mode fiber optic (SMF) by using difference wavelengths of laser light to carrier different signals which promising solutions to the ever increasing demand for bandwidth. Orthogonal Frequency Division Multiplexing (OFDM) technique distributes the data over a large number of carriers that are spaced apart at precise frequencies with overlapping bands. The use of FFT for modulation provides orthogonality to the sub- carriers, which prevents the demodulators from seeing frequencies other than their own. Hence by incorporating OFDM along with the optical fiber, the RoF system with WDM can be used for both short distance as well as long-haul transmission at very high data rate. This improves the system flexibility and provides a very large coverage area without increasing the cost and complexity of the system very much. This project investigates the feasibility of OFDM as a modulation technique to transmit the basebands signal over SMF. RF-to-optical up-conversion and optical-to�RF down-conversion have been modeled and used as optical modulator and optical demodulator respectively. Result from Optisystem model shows the performance of OFDM signal through the WDM RoF access network. The system was utilized to carry data rates 10Gbps, the modulation type for OFDM is 4 QAM 2 bit per symbol for each channel and OFDM demodulator are employed together with coherent detection at receiver part to receive the OFDM signals over a SMF network transmission. The signal power is decreasing while the length of optical fiber was increasing for channel 1 does not apply to other channels

Broadband optical sources for low-cost WDM-MB-OFDM networks

[EN] Multiband OFDM signal transmission through a 10 km optical fiber link is experimentally demonstrated by using a broadband source. We propose the use of optical broadband sources in multiband OFDM signal transmitters as a low-cost and power fading free solution. The OFDM band is dynamically selected in the receiver by means of an MZI. Therefore, MB-OFDM is demonstrated at 1.5 Gb/s per band in access networks, supporting up to 20 ONUs.Chicharro López, FI.; Ortega Tamarit, B.; Diego Antón, MD.; Mora Almerich, J. (2017). Broadband optical sources for low-cost WDM-MB-OFDM networks. IEEE Communications Letters. 21(8):1759-1762. doi:10.1109/LCOMM.2017.2702175S1759176221

Harnessing machine learning for fiber-induced nonlinearity mitigation in long-haul coherent optical OFDM

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).Coherent optical orthogonal frequency division multiplexing (CO-OFDM) has attracted a lot of interest in optical fiber communications due to its simplified digital signal processing (DSP) units, high spectral-efficiency, flexibility, and tolerance to linear impairments. However, CO-OFDM’s high peak-to-average power ratio imposes high vulnerability to fiber-induced non-linearities. DSP-based machine learning has been considered as a promising approach for fiber non-linearity compensation without sacrificing computational complexity. In this paper, we review the existing machine learning approaches for CO-OFDM in a common framework and review the progress in this area with a focus on practical aspects and comparison with benchmark DSP solutions.Peer reviewe

Modeling and compensation of nonlinear distortion in direct-detection optical Fast-OFDM systems

Fast-OFDM based intensity-modulation and direct-detection (IM/DD) has been proposed for the deployment of cost-efficient optical access networks, due to simple implementation and high spectral efficiency. In this work, the generalized memory polynomial (GMP) is firstly applied to model the nonlinear characteristic of IM/DD Fast-OFDM links, including memory effects. After model validation using measured data of a 10 km single mode fiber link, the GMP is used for performance investigations of a combined clipping and digital post-distortion approach to optical Fast-OFDM, considering both 4PAM and 8PAM modulation formats and different number of Fast-OFDM subcarriers. This work firstly reports performance results of optical 8PAM-Fast-OFDM systems using 2PAM-based training signals for digital post-distortion and FFT-based channel estimation. Excellent performance improvements are achieved using the proposed distortion compensation scheme, relative to conventional system implementation

Development of a dc-ac power conditioner for wind generator by using neural network

This project present of development single phase DC-AC converter for wind generator application. The mathematical model of the wind generator and Artificial Neural Network control for DC-AC converter is derived. The controller is designed to stabilize the output voltage of DC-AC converter. To verify the effectiveness of the proposal controller, both simulation and experimental are developed. The simulation and experimental result show that the amplitude of output voltage of the DC-AC converter can be controlled

Experimental demonstration of IDMA-OFDM for passive optical network

We present interleave division multiple access (IDMA) scheme combined with orthogonal frequency division multiplexing (OFDM) for passive optical network, which offers improved transmission performance and good chromatic dispersion tolerance. The interleavers are employed to separate different users and the generated chips are modulated on OFDM subcarriers. The feasibility of IDMA-OFDM-PON is experimentally verified with a bitrate of 3.3 Gb/s per user. Compared with OFDMA, IDMA-OFDM offers 8 and 6 dB gains in term of receiver sensitivity in the cases of 2 and 4 users, respectively

Spectrum-Efficient Triple-Layer Hybrid Optical OFDM for IM/DD-Based Optical Wireless Communications

In this paper, a triple-layer hybrid optical orthogonal frequency division multiplexing (THO-OFDM) for intensity modulation with direct detection (IM/DD) systems with a high spectral efficiency is proposed. We combine N-point asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM), N/2-point ACO-OFDM, and N/2-point pulse amplitude modulated discrete multitoned (PAM-DMT) in a single frame for simultaneous transmission. The time- and frequency-domain demodulation methods are introduced by fully exploiting the special structure of the proposed THO-OFDM. Theoretical analysis show that, the proposed THO-OFDM can reach the spectral efficiency limit of the conventional layered ACO-OFDM (LACO-OFDM). Simulation results demonstrate that, the time-domain receiver offers improved bit error rate (BER) performance compared with the frequency-domain with ∼40% reduced computation complexity when using 512 subcarriers. Furthermore, we show a 3 dB improvement in the peak-to-average power ratio (PAPR) compared with LACO-OFDM for the same three layers