Etude des nouveaux formats de modulation pour la mont

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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
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• Outline

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• 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

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• 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

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1. Introduction (1)Interest of OFDM for the
optical access network
Application Débit requis
Téléchargement des données 2 Mb/s
VoIP, Video-telephony, Videoconferencing 1 Mb/s
Musique à la demande (contenu multimédia) 2 Mb/s
Jeux en ligne 1 Mb/s
TV numérique SD 3 Mb/s
TV numérique HD 10 Mb/s
TV numérique HD canaux additionnels (2 HD DTV) 20 Mb/s
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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

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Interest of OFDM
Spectre de DB, NRZ, DPSK et RZ

• 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
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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)

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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 rate without 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)

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• 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

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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)

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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

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2. Experimentation (3)Low-cost MB-OFDM for
remote modulation of colorless ONU, EAM solution
Received signal's constellation
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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

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2. Experimentation (7)Comparison with NRZ signal
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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

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2. Experimentation (9)Comparison with NRZ signal
For EAM solution
Measured factor OFDM remote modulation NRZ remote modulation
Architecture WDM/TDM-PON WDM/TDM-PON
Launched power laser 2dBm 2dBm
Bit rate 1.92Gbit/s 2Gbit/s
SNR 19dB (BERlt10-9) 19dB (BERgt10-6)
Achieved splitting Ratio (BERlt10-9) 1x16 (SNR 19dB) 1x8 (SNR 23dB)
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Discussion
Increase the bit rate in optical access network GPON ? 10G in access Fiber chromatic dispersion Expensive component Chirp of components
Low cost infrastructure and low cost ONU module Low cost components Colorless ONU RF cost vs optical cost Fiber single architecture
Colorless ONU Rayleigh Backscattering

• 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

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• 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

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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

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2. Experimentation (2)Direct modulation of DFB
laser at a bit rate of 10Gbit/s
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2. Experimentation (3)Direct modulation of
low-cost laser at a bit rate of 10Gbit/s DFB
laser
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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

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2. Experimentation (5)Comparison with NRZ
modulation 2.5GHz DFB laser
Considering factors Direct modulation with AMOOFDM signal Direct modulation with NRZ-OOK signal
Architecture TDM-PON TDM-PON
Launch power 9.6dBm 9.6dBm
Bit rate 10Gb/s 10Gb/s
Transmission distance possible 110 km 0
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Discussion
Increase the capacity in optical access network GPON ? 10G in access Transmission distance ? 100km Fiber chromatic dispersion Expensive component Chirp of components

• 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

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• 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

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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

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This work was performed in the framework of
E-Photon One network of excellence and the French
ANTARES project

• Thank you for your attention
• Any question ?

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Annexe (1)

• Definition of EVM

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