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Next-Generation Optical Access Networks

Next-Generation Optical Access Networks. 李承俊 2010-12-08 258okm@sjtu.edu.cn. Outline. CURRENT-GENERATION PON: TDM-PONs · Bandwidth Enhancement of TDM-PONs · Reach Extension and User-Number Increase of TDM-PONs NEXT-GENERATION PON ARCHITECTURES · C+1 Generation PONs

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Next-Generation Optical Access Networks

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  1. Next-Generation Optical Access Networks 李承俊 2010-12-08 258okm@sjtu.edu.cn

  2. Outline • CURRENT-GENERATION PON: TDM-PONs · Bandwidth Enhancement of TDM-PONs · Reach Extension and User-Number Increase of TDM-PONs • NEXT-GENERATION PON ARCHITECTURES · C+1 Generation PONs · C+2 Generation PONs • SUCCESS-DWA PON and SUCCESS-HPON

  3. CURRENT-GENERATION PON: TDM-PONs • The demand for ever higher data rates remains strong. • Currently, the broadly accepted optical access solution is the time-division multiplexed (TDM) PON.

  4. The downstream traffic is continuously broadcast to all ONU. In the upstream, each ONU transmits during the time slots that are allocated by the OLT.

  5. Enhancements of TDM-PONs • Bandwidth Enhancement 1. Standardize a higher rate version of TDM-PONs. 2. New services/signals can be launched on different wavelengths to enhance system bandwidth and service. • Reach Extension and User-Number Increase of TDM-PONs 1. Supporting more users in a PON system can enhance bandwidth efficiency and improve cost sharing. 2. Extending the physical reach of a PON allows the consolidation of the access and core networks.

  6. NEXT-GENERATION PON ARCHITECTURES • To emphasize that these systems enable a smooth upgrade from current generation TDM-PONs in the near future, we categorize them as the C+1 generation PON system. • Most other next-generation PON proposals focus on achieving much higher capacities to satisfy the long-term demand. We categorize such systems as the C+2 generation PON system.

  7. C+1 generation PON system • Service Overlay With WDM Techniques:

  8. C+1 generation PON system • Service Overlay With SCM(subcarrier multiplexing)

  9. C+1 generation PON system • Service Overlay With Spectral-Shaping Line-Coding Technique

  10. C+2 generation PON system • The basic architecture

  11. C+2 generation PON system • WDM-PONs Based on Spectral Slicing:

  12. C+2 generation PON system • WDM-PONs Based on Tunable Components • WDM-PONs Based on Injection Locking • WDM-PONs Based on Centralized Light Sources (CLSs)

  13. SUCCESS-DWA PON • SUCCESS-DWA PON: Stanford University access (SUCCESS) dynamic wavelength allocation (DWA) • Key parts: Tunable lasers (TLs), the arrayed waveguide grating (AWG) thin-film WDM filters

  14. SUCCESS-DWA PON

  15. DOWNSTREAM • 4×4 cyclic AWG • Notice that the AWG does allow all TLs to simultaneously transmit on the same wavelength.

  16. DOWNSTREAM • In the four TDM PON case, all four OLTs (lasers) must be activated, despite the fact that some OLTs may only be serving a few subscribers. • With the SUCCESS-DWA PON, on the other hand, only one TL and AWG are initially added to the central office, and the subscribers across multiple PONs are all serviced by the single TL. As demand grows, additional TLs can be added to the AWG. • Additional AWGs can be added to shift from four TLs serving four PONs to four TLs serving each single PON.

  17. UPSTREAM • For fig.3(a), all the ONUs have Only one fixed wavelength transmitter. The performance is limited. • For fig.3(b), The light source at each ONU can be 1. a fixed-wavelength FP. the ONU is virtually grouped with other ONUs at the same wavelength, and shares the same PD in the time domain. 2. two or more FPs at different wavelengths the ONU can choose one of the FPs for transmission. 3. a TL the ONU can use any of the upstream wavelengths

  18. UPSTREAM

  19. UPSTREAM • For fig.3(c), the DeMux at the OLT is tunable. Each end user has a specific upstream wavelength , and cost-effective VCSELs(垂直腔面发射激光器) would be ideal light sources.

  20. UPSTREAM

  21. UPSTREAM • Each user is equipped with a fixed-wavelength transmitter that corresponds to the upstream group to which he has been assigned. • upstream and downstream AWGs pass completely different wavelengths and require different channel spacing. Therefore, separate AWGs are necessary for up/downstream. • To cover all end users located on different physical PONs, the first several subscribers from different PONs are assigned different upstream wavelengths.

  22. Broadcast • The full WDM-PON does not inherently support multicast or broadcast in the physical layer. • For the SUCCESS-DWA PON, broadcast can be realized by having two passbands on the user WDM filters at the ONUs.

  23. SUCCESS-HPON • The basic topology consists of a single-fiber collector ring with stars attached to it. The collector ring strings up remote nodes (RNs),which are the centers of the stars. • A RN has either a passive power splitter (coupler) or an AWG inside. 1. If a RN contains a passive splitter, one dedicate wavelength on DWDM grid is used to broadcast the downstream data for the ONUs attached to the RN. 2. if a RN possesses an AWG, each ONU has its own dedicated wavelength on a DWDM grid to communicate with OLT.

  24. Remote Node Design

  25. Remote Node Design • For fig.2(a), RN contains an AWG that supports DWDM. Each thin-film filter drops a different wavelength band. • For fig.2(b),RN contains a passive optical splitter that supports PON-like CWDM transmission. Cascading thin-film filters that pass a DWDM wavelength and a CWDM wavelength may be needed for downstream and upstream data transmission. • They are attractive from the network maintenance’s point of view, but they lack protection and restoration capability.

  26. Remote Node Design • For fig.2(c), A simple circuit consists of photo diode and integrator that detect the optical power on one side of the ring. • If optical power ceases, the node assumes there is a broken fiber link and triggers the 2 × 2 optical switch to swap from the “bar” state to the “cross” state such that the RN listens to the traffic on the other side. • When the RN experiences power failure, the power sensing circuit will stop functioning. However, it will not affect the light path and normal operation can proceed as usual.

  27. Reference • Kazovsky, L.G, Wei-Tao Shaw, Gutierrez, D, Ning Cheng, Shing-Wa Wong, “Next-Generation Optical Access Networks”,J. Lightw. Technol, (Invited Paper) • Kazovsky, L.G,” Burst-Mode Metro and Access Networks”,Conf.OFC/NFOEC.2007 • Y.-L. Hsueh, M. S. Rogge, S. Yamamoto, and L. G. Kazovsky, “A highly flexible and efficient passive optical network employing dynamic wavelength allocation,” J. Lightw. Technol., vol. 23, no. 1, pp. 277–286, Jan. 2005. • Y.-L. Hsueh, W.-T. Shaw, L. G. Kazovsky, A. Agata, and S. Yamamoto, “SUCCESS PON demonstrator: Experimental exploration of next-generation optical access networks,” IEEE Commun. Mag., vol. 43, no. 8, pp. S26–S33, Aug. 2005. • F.-T. An, K. S. Kim, D. Gutierrez, S. Yam, E. Hu, K. Shrikhande, and L. G. Kazovsky, “SUCCESS: A next-generation hybrid WDM/TDM optical access network architecture,” J. Lightw. Technol., vol. 22, no. 11, pp. 2557–2569, Nov. 2004.

  28. Thank you !

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