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Etude des nouveaux formats de modulation pour la montée en débit dans le réseau d'accès optique

Etude des nouveaux formats de modulation pour la montée en débit dans le réseau d'accès optique. 28/03/2008 – Journée de doctorant ENSTB. DUONG Thanh Nga Encardrant à FT: GENAY Naveena Directeur de thèse: SIMON Jean-Claude. Outline. 1. Introduction Contexte Experimentation

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Etude des nouveaux formats de modulation pour la montée en débit dans le réseau d'accès optique

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  1. Etude des nouveaux formats de modulation pour la montée en débit dans le réseau d'accès optique 28/03/2008 – Journée de doctorant ENSTB DUONG Thanh Nga Encardrant à FT: GENAY Naveena Directeur de thèse: SIMON Jean-Claude

  2. Outline 1 • Introduction • Contexte • Experimentation • Low-cost MB-OFDM for remote modulation of colorless ONU • Direct modulation of 2.5GHz DFB laser at a bit rate of 10Gbit/s • Conclusion and perspective 2 3

  3. Outline 1 • Introduction • Contexte • Experimentation • Low-cost MB-OFDM for remote modulation of colorless ONU • Direct modulation of DFB laser at a bit rate of 10Gbit/s • Conclusion and perspective 2 3

  4. 1. Introduction (1)Interest of OFDM for the optical access network

  5. 1. Introduction (2)Interest of OFDM for the optical access network • Increase the capacity and decrease the cost of the system in optical access network • Increase the bit rate up to 10Gbit/s and more • Increase the transmission distance up to 100km without chromatic dispersion compensation • Fiber chromatic dispersion • Rayleigh Backscattering in architecture colorless ONU • Cost of system • Solution • Low-cost ONU module • Direct modulation of laser • To use advanced modulation format which is robust to fiber chromatic dispersion like DB, DPSK or OFDM modulation format

  6. Spectre de DB, NRZ, DPSK et RZ Interest of OFDM • Duo-binary (DB) • Un spectre est plus comprimé que celui du NRZ • Plus tolérance à la dispersion chromatique • Détection simple • Complexité de l'émetteur • DPSK/DQPSK • Appliquer la technique remodulation • La complexité du récepteur → coût élevé • DPSK/DQPSK-ASK • Forte tolérance à la DC • La complexité de l'émetteur et du récepteur • Faible sensibilité au récepteur • OFDM • Technique de transmission multi-porteuses • Utiliser l'algorithme FFT/IFFT • Chaque sous-porteuse est modulé par un format de modulation numérique différent Le signal modulé DPSK

  7. 1. Introduction (3)Interest of OFDM for the optical access network • What is OFDM ? • Widely use in the radio communication • DAB (Digital Audio Broadcasting) • DVB-T (Digital Video Broadcasting-Terrestrial) • DRM (Digital Radio Mondiale) • Wireless system • Multi-carriers modulation format which uses a large number of closely-spaced orthogonal sub-carriers • Use FFT/IFFT algorithm • Each sub-carrier is modulated with a conventional modulation (QPSK, m-QAM, etc…)

  8. 1. Introduction (5)Interests of OFDM for optical access network • Why we use OFDM for optical access network? • High density of information (Bit/s/Hz) → increase the bit ratewithout increasing RF cost (using low bandwidth component) • More tolerant to fiber chromatic dispersion (multi-path resilience) and we can optimize the transmission performance by adjusting the modulation format on each sub-carrier → 10G compatible • Could be implemented with DSP technique on fast and low cost devices • Reuse existing development in radio system (ISO/IEC DIS26908 UWB standard for MB-OFDM) • Improve the transmission performance with the help of FEC (BER = 10-4 without FEC)

  9. Outline 1 • Introduction • Contexte • Experimentation • Low-cost MB-OFDM for remote modulation of colorless ONU • Direct modulation of DFB laser at a bit rate of 10Gbit/s • Conclusion 2 3

  10. CWDM 1xN ONU CW CW laser Remote modulation 20km Splitter OLT CW Rx 1.92Gbit/s OFDM 2. Experimentation (1)Low-cost MB-OFDM for remote modulation of colorless ONU • Bidirectional transmission on 20km single-fiber hybrid WDM/TDM-PON architecture • CW laser at 1550nm sent downstream • Upstream data was generated by MB-OFDM at 1.92Gbit/s (3 OFDM bands at a bit rate of 640Mbit/s for each band)

  11. CW signal l1 OFDM Signal EAM CWDM SOA1 SOA2 Modulated upstream signal l1 2. Experimentation (2)Low-cost MB-OFDM for remote modulation of colorless ONU, EAM solution • Filter: CWDM having 0.6dB insertion losses and bandwidth of 20nm • EAM: 14dB insertion losses, 10dB extinction ratio and bandwidth of 12GHz • 2SOAs: 18dB optical gain • 3 OFDM bands centred at 744MHz, 1272MHz and 1800MHz. 128 sub-carriers modulated by QPSK format each band

  12. upstream transmission for 1x16 splitting ratio BTB transmission, 2. Experimentation (3)Low-cost MB-OFDM for remote modulation of colorless ONU, EAM solution Received signal's constellation

  13. 1x16 BTB 6dB 2dB 1x8 2. Experimentation (4)Low-cost MB-OFDM for remote modulation of colorless ONU, EAM solution • Remote modulation was possible on a single fiber hybrid architecture • There are 2dB penalty for 1x8 splitting ratio and 6dB for 1x16 splitting ratio

  14. NRZ EAM CWDM SOA1 SOA2 2. Experimentation (7)Comparison with NRZ signal

  15. 1x4 1x16 1x2 (pour 2Vp-p) 1x8 No splitter R-EAM solution EAM solution 2. Experimentation (8)Comparison with NRZ signal • Remote modulation was also possible on a single fiber hybrid architecture • Only a splitting ratio of 1x8 was achieved for EAM solution and no splitter could be added for R-EAM solution (at 1.3Vp-p input at R-EAM)-error floor for 1x2 splitting ratio at 2Vp-p

  16. 2. Experimentation (9)Comparison with NRZ signal For EAM solution

  17. Discussion • OFDM modulation is a good candidate as a cost effective solution for colorless ONU • OFDM format is more tolerant to Rayleigh backscattering than NRZ format in a bidirectional link

  18. Outline 1 • Introduction • Interest of OFDM modulation for the optical access network • Experimentation • Low-cost MB-OFDM for remote modulation of colorless ONU • Direct modulation of low-cost laser at a bit rate of 10Gbit/s • Conclusion 2 3

  19. 20km, 50km, 110km SMF DSP modulation S/P M-QAM mapper IFFT P/S DFB laser AWG Encoded data in AOV DSP demodulation Optical receiver A/D converter Encoded data out Negotiation between Tx and Rx 2. Experimentation (1)Direct modulation of DFB laser at a bit rate of 10Gbit/s • Direct modulation of 2.5GHz DFB laser by 10Gbit/s AMOOFDM signal • 64 sub-carriers • The m-QAM mapping varies from 4-QAM to 32-QAM • Transmission distance was taken to be 20km, 50km and 110km • No dispersion compensation

  20. Sub No.1 Sub No.31 Sub No.10 Sub No.23 2. Experimentation (2)Direct modulation of DFB laser at a bit rate of 10Gbit/s

  21. BERk is the bit error rate of kth sub-carrier • ND is the number of sub-carrier which contain the real data • The transmission is possible on 110km SMF • A BER of 10-3 was obtained at a received optical power of -16dBm • The penalties for 20km and 50km optical links are negligible (the sensibility is considering at BER of 10-4) • The penalty on 110km optical link was approximately 2dB because of chromatic dispersion 2. Experimentation (3)Direct modulation of low-cost laser at a bit rate of 10Gbit/s – DFB laser

  22. 2. Experimentation (4)Comparison with NRS modulation – DFB laser • Modulate directly with signal NRZ-OOK at a bit rate of 10Gb/s using the same DFB laser and receiver • There was an error-floor at a bit rate of 9x10-4 for BTB curve and at a bit rate of 3x10-2 for 20km transmission. • Transmission over 50km and 110km SMF were impossible due to the effect of chromatic dispersion AMOOFDM is more tolerant to fiber chromatic dispersion than NRZ-OOK signal

  23. 2. Experimentation (5)Comparison with NRZ modulation – 2.5GHz DFB laser

  24. Discussion • AMOOFDM modulation is a good candidate as a cost effective solution for optical access network in order to increase the capacity (bit rate and transmission distance) • AMOOFDM format is more tolerant to fiber dispersion chromatic than NRZ format

  25. 1 2 3 Outline • Introduction • Contexte • Experimentation • Low-cost MB-OFDM for remote modulation of colorless ONU • Direct modulation of DFB laser at a bit rate of 10Gbit/s • Conclusion and perspective

  26. 3. Conclusion • A remote modulation scheme was presented for upstream transmission in hybrid WDM/TDM-PON single fiber architecture • A solutions are proposed for the colorless ONU: EAM solution. A bit rate of 1.92Gbit/s was archived for each wavelength • Comparison between NRZ and OFDM remote modulation for both solutions was performed • OFDM format is more robust to Rayleigh Backscattered light than NRZ-OOK modulation • 10Gb/s transmission is experimentally demonstrated over 110km SMF by direct modulation of 2GHz bandwidth DFB laser without dispersion compensation • A comparison between NRZ-OOK format and AMOOFDM format was performed at a bit rate of 10Gb/s • AMOOFDM modulation format is more tolerant with fiber chromatic dispersion than NRZ-OOK format

  27. Thank you for your attention Any question ? This work was performed in the framework of E-Photon One network of excellence and the French ANTARES project

  28. Annexe (1) • Definition of EVM

  29. 1. Introduction (4)Interest of OFDM for the optical access network

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