Modified Synchronization Scheme for Coherent Optical OFDM Systems

Abstract

We propose a series of modified methods covering timing and frequency synchronization in the coherent optical orthogonal frequency-division-multiplexing (CO-OFDM) system. The modified timing synchronization method eliminates the ambiguity of Park's method, and the modified frequency synchronization method employs only one training symbol without any loss of accuracy compared to Schmidl's method. The proposed synchronization scheme is tested in a 20 Gb∕s CO-OFDM simulated system, with the result that the modified synchronization scheme gives a more accurate timing estimation and a more economical frequency offset estimation with a wide estimation range in the relatively short transmission distance. Meanwhile, chromatic dispersion compensation added before the synchronization keeps the modified scheme's performance stable over longer distances and makes better subcarrier recovery with the optical signal-to-noise ratio improved by 3 dB at the bit-error rate of 10 −3 .

OFDM synchronization system using wavelet transform for symbol rate detection

“…As the wavelet-based OFDM has higher bandwidth efficiency and can gain better bit error rate (BER) performance than the conventional OFDM in fading channels [19] and carrier frequency offset with phase noise [20], in this paper, we propose a new method for the synchronization of OFDM using wavelet transform. This proposal is a potential approach, given that detecting the clock symbol rate is critical for OFDM receiver clock [21] and using the wavelet for high resolution of frequency is a suitable solution for low-frequency channel, e.g., the well-known wavelet transforms namely Haar and Daubechies wavelet used in discrete signals [22]. The results show that the wavelet transform is feasible and promising toward 5G communications by using the extracted frequency domain for symbol clock rate detection.…”

“…Typically, the proposed method extracts a clock waveform synchronized with a symbol rate due to denoising by multi-resolution analysis for detecting discontinuity between symbols. The proposed algorithm for extracting channel distortion and frequency offset using wavelet analysis is a promising approach, given that the OFDM model construction method with timing recovery and frequency synchronization can be applied to various communication systems, such as broadcasting systems [11,12], optical communications [13] or long term evolution (LTE) network [14].…”

Frequency Synchronization Based on a Cascading Cross‐Correlation Function for CO‐FBMC‐OQAM

“…Fractional frequency offset part [20][21][22][23] , called IFO and FFO respectively. For full-range frequency synchronization, the accurate estimation and compensation for FFO with an estimated range of (−1, +1) is very critical.…”

High-Precision and Low-Complexity Symbol Synchronization Algorithm Based on Dual-Threshold Amplitude Decision for Real-Time IMDD OFDM-PON

“…For example, there is an ambiguity caused by the side lobes of the time metric in [8]. When training symbols are affected by dispersion during transmission, it will significantly affect the performance of synchronization [19].Therefore, it becomes crucial to explore new symbol synchronization algorithms for real-time OFDM-PON system.…”