1 Improving Chromatic Dispersion Tolerance in Long-Haul Fibre Links using Coherent OOFDM M. A. Jarajreh, Z. Ghassemlooy, and W. P. Ng Optical Communications Research Group School of Computing, Engineering and Information Sciences University of Northumbria at Newcastle, UK

Contents OFDM and Optical OFDM (OOFDM) Applications of OOFDM Modems Coherent -OOFDM (CO-OOFDM)Modems Design CO-OOFDM Modems - Modelling (Matlab and VPi) Motivation Results Back-to-Back Performance Back-to-Back Performance Effect of Number of Sub-carriers and CP on CD Tolerance Effect of Number of Sub-carriers and CP on CD Tolerance Effect of Number of Sub-carriers ON Transmission performance Effect of Number of Sub-carriers ON Transmission performance Effect of Sampling Speed on CD Tolerance Effect of Sampling Speed on CD Tolerance Effect of Sampling Speed on Transmission Performance in Fibre Links Effect of Sampling Speed on Transmission Performance in Fibre Links The Effect of Adaptively Modulated CO-OOFDM on CD Tolerance The Effect of Adaptively Modulated CO-OOFDM on CD Tolerance Conclusions

OFDM 3 Orthogonal Frequency Division Multiplexing (OFDM) Harmonically related narrowband sub-carriers The sub-carriers spaced by 1/Ts The peak of each sub-carrier coincides with trough of other sub-carriers Splitting a high-speed data stream into a number of low-speed streams Different sub-carrier transmitted simultaneously

4 What is OOFDM By introducing OFDM in the optical domain, Optical OFDM (OOFDM) was generated Advantages of OOFDM Cost-effective High-speed Excellent flexibility and robustness Optical OFDM

5 Access and local area networks IMDD modems Future high-capacity long-haul networks Coherent modems Combating optical fibers dispersion and polarization mode dispersion Applications of OOFDM Modems

Coherent -OOFDM Modems Design 6 CO-OOFDM modem diagram used in numerical simulations, (dotted line is either fibre or integrated optics)

CO-OOFDM Modems - Modelling Matlab: easy to model the OFDM modem 32-QAM modulation   32-QAM detection with additive noise 7

CO-OOFDM Modems – Modelling 8 Screen shots (Coherent OFDM System) (Virtual Photonic Inc.) VPi Software

9 The achievable signal transmission capacity of an Optical Orthogonal Frequency Division Multiplexing (OOFDM) modem over Single Mode Fibre (SMF) links is affected considerably by: Fibre Chromatics Dispersion (CD) Number of sub-carriers Cyclic prefix Fibre nonlinearity Optical launch power Numerical simulations are undertaken to investigate the above-mentioned effects on the system performance of Coherent OOFDM Motivation

10 Results Work will be presented Back-to-back Performance Effect of number of subcarriers and Cyclic Prefix (CP) on Chromatic Dispersion (CD) Tolerance Effect of sampling speed on CD tolerance The result of utilizing AM-CO-OOFDM on CD tolerance

11 Simulation Parameters ParametersValues No. of subcarriers64 Wavelength1550 nm Light sourceLaser diode PhotodetectorPIN Photodetector responsivity0.9 Fibre span80 km Chromatic dispersion17 ps/nm/km Fibre loss0.2 dB/km ADC/DAC - sampling rate - clipping ratio - quantization 12.5 GS/s 13 dB 10 bits Data rates - DBPSK - DQPSK - 16-QAM - 32-QAM - 64-QAM QAM QAM 10 Gb/s 20 Gb/s 40 Gb/s 50 Gb/s 60 Gb/s 70 Gb/s 80 Gb/s Low pass filter order and 3- dB bandwidth 2nd & 6.5GHz EDFA span EDFA gain EDFA noise figure 80km 16 dB 6 dB

12 Back-to-Back Performance Quantization and clipping effects were switched off

13 Adjacent Symbol Interference (ASI) Symbol Smearing Due to Channel

14 Cyclic Prefix Inserted in Guard Interval to Suppress Adjacent Channel Interference

15 Effect of Number of Sub-carriers and CP on CD Tolerance Cyclic prefix is more effective if compared with the number of subcarriers in combating dispersion

16 Effect of Number of Sub-carriers ON Transmission performance With -6dBm launch power, 64 subcarriers is the optimum number of subcarriers

17 Effect of Sampling Speed on CD Tolerance Lower sampling speed can increase CD tolerance for a fixed number of subcarriers

18 Effect of Sampling Speed on Transmission Performance in Fibre Links With the presence of non-linearity, lower sampling speed does not mean higher performance

19 The Effect of Adaptively Modulated CO-OOFDM on CD Tolerance Adaptively modulating the CO-OOFDM subcarriers increases CD tolerance

20 Conclusions For coherent OOFDM modems, for a given modulation format, increasing the number of sub-carriers or cyclic prefix length, increases dispersion tolerance effectively A longer length CP is more effective in combating fibre dispersion than use of large number of sub-carriers For coherent OOFDM Modem the optimum launched power is -6 dBm For a given number of subcarriers sampling speed can increase the system dispersion tolerance Utilizing CO-AMOOFDM increases the system tolerance to CD

21 Thank you for your attention ! Any questions?

Web: Web: Tel: Tel: Future Contact