Homodyne Ultra-Dense WDM PONs: Can They be Affordable?
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Homodyne Ultra-Dense WDM PONs: Can They be Affordable?

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Several homodyne transceiver architectures are proposed and discussed, regarding their feasible implementation as future subsystems in ultra-dense WDM-PONs.

Several homodyne transceiver architectures are proposed and discussed, regarding their feasible implementation as future subsystems in ultra-dense WDM-PONs.

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Homodyne Ultra-Dense WDM PONs: Can They be Affordable? Presentation Transcript

  • 1. Homodyne Ultra dense WDM-PONs: can they be affordable in access? Josep Prat ` Josep M. Fabrega Ronald Freund ` Universitat Politecnica de Catalunya - BarcelonaTech Fraunhofer Institute for Telecommunications - Heinrich Hertz Institut jmfabrega@tsc.upc.edu June 10, 2010 ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 1 / 27
  • 2. Outline Introduction Transceiver architectures Case studies Conclusions ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 2 / 27
  • 3. Introduction Novel multimedia applications Voice over IP Video on demand HDTV User bit rate demand expected to be increasing Nielsen law: bandwidth per user increments in a 50 % per year In 2020 each user would demand an average bandwidth of 1 Gb/s ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 3 / 27
  • 4. FTTH roadmap and tendencies in PONs Actual tendencies: PON standardization bodies pushing towards high capacity systems by increasing the aggregate bit rate (10 Gb/s) ONU operates at a very high bit rate in the opto-electronics transceivers just to use a small fraction of it (≈ 3 %) High power consumption! New philosophy proposed, exploiting the pure WDM dimension ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 4 / 27
  • 5. Towards this new philosopy Advantages Drawbacks IM-DD Simplicity sensitivity optical filters selectivity Coherent Use of advanced modulation formats Image frequency (heterodyne) Electrical filtering for channel selection Phase noise (Homodyne) Detection amplitude, phase and polarization Linear transformation optical ⇒ electrical Increase of sensitivity ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 5 / 27
  • 6. How to minimize this phase error? OPLLs: Several architectures proposed Decision driven [1] Costas [2] Balanced [3] Subcarrier modulated [4] Phase diversity with zero IF receiver Analog mutiple differential detection [5] Digital phase estimation: Wiener filter [6, 7] Regenerative frequency dividers [8] Viterbi & Viterbi [9, 10] But many of them are not the cheap solutions we search for! ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 6 / 27
  • 7. How to minimize this phase error? OPLLs: Several architectures proposed Decision driven [1] Costas [2] Balanced [3] Subcarrier modulated [4] Phase diversity with zero IF receiver Analog mutiple differential detection [5] Digital phase estimation: Wiener filter [6, 7] Regenerative frequency dividers [8] Viterbi & Viterbi [9, 10] But many of them are not the cheap solutions we search for! New solutions have to be proposed ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 6 / 27
  • 8. Lock-In amplified OPLL Low-cost PLL based on balanced OPLL [3] Compared to other oPLL architectures: Costas [2] Balanced [3] Subcarrier modulated [4] 10 ns loop delay (eq. 20 cm of fiber) Linewidth tolerance BER 10−9 Linewidth tolerance BER 10−3 Balanced 420 kHz 1.2 MHz Costas 1.15 MHz 2.65 MHz SCM 1.35 MHz 2.75 MHz Lock-In amplified 675 kHz 3.1 MHz ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 7 / 27
  • 9. Lock-In amplified OPLL Low-cost PLL based on balanced OPLL [3] Compared to other oPLL architectures: Costas [2] Balanced [3] Subcarrier modulated [4] 10 ns loop delay (eq. 20 cm of fiber) Linewidth tolerance BER 10−9 Linewidth tolerance BER 10−3 Balanced 420 kHz 1.2 MHz Costas 1.15 MHz 2.65 MHz SCM 1.35 MHz 2.75 MHz Lock-In amplified 675 kHz 3.1 MHz Lock-In amplifier OPLL is a competitive low-cost solution! ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 7 / 27
  • 10. Time switched phase diversity Phase diversity by switching from I to Q component at each bit Less components duplicity than standard phase diversity (lower cost) 3 dB penalty respect to an ideal system Linewidth tolerance for 10−3 BER-floor: 1.8 % of bitrate [11] 3 GHz channel spacing for 1 dB penalty at BER of 10−9 [12] A similar structure has been recently integrated in InP substrate [13] A more simple structure is achieved when driving the laser directly [14] ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 8 / 27
  • 11. Time switched phase diversity Phase diversity by switching from I to Q component at each bit Less components duplicity than standard phase diversity (lower cost) 3 dB penalty respect to an ideal system Linewidth tolerance for 10−3 BER-floor: 1.8 % of bitrate [11] 3 GHz channel spacing for 1 dB penalty at BER of 10−9 [12] A similar structure has been recently integrated in InP substrate [13] A more simple structure is achieved when driving the laser directly [14] Time-switched phase diversity provides high performances at low cost ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 8 / 27
  • 12. Outline Introduction Transceiver architectures Case studies Conclusions ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 9 / 27
  • 13. Summary of the performances Phase noise Technique Linewidth Penalty Required key Complexity tolerance component Decision-drive loop 5 MHz 0 dB 90◦ hybrid High Costas loop 4.9 MHz 0 dB 90◦ hybrid Medium/High Subcarrier loop 5.1 MHz 0 dB 90◦ hybrid High Balanced loop 2.4 MHz 2 dB Optical coupler Low Lock-In loop 6.4 MHz 1 dB Optical coupler Low Full phase diversity 5% bitrate 0 dB 90◦ hybrid Medium Time-switch (Scrambler) 1.8% bitrate 4 dB Phase modulator Medium Time-switch (Direct drive) 3.4% bitrate 4 dB High-chirp laser Low Penalty is respect to an ideal system whereas tolerance is for a BER-floor of 10−3 Three main approaches: Optical phase locked loop, full phase diversity and time-switched diversity ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 10 / 27
  • 14. Summary of the performances Phase noise Technique Linewidth Penalty Required key Complexity tolerance component Decision-drive loop 5 MHz 0 dB 90◦ hybrid High Costas loop 4.9 MHz 0 dB 90◦ hybrid Medium/High Subcarrier loop 5.1 MHz 0 dB 90◦ hybrid High Balanced loop 2.4 MHz 2 dB Optical coupler Low Lock-In loop 6.4 MHz 1 dB Optical coupler Low Full phase diversity 5% bitrate 0 dB 90◦ hybrid Medium Time-switch (Scrambler) 1.8% bitrate 4 dB Phase modulator Medium Time-switch (Direct drive) 3.4% bitrate 4 dB High-chirp laser Low Penalty is respect to an ideal system whereas tolerance is for a BER-floor of 10−3 Three main approaches: Optical phase locked loop, full phase diversity and time-switched diversity Polarization mismatch Local control Polarization diversity Polarization switching Penalty 0 dB 0 dB 3 dB Key component Polarization actuator Pol. beam splitter Pol. scrambler/switch Response time 1 ms – 1 s < 10 µs < 10 µs Complexity High Med./high Low (if placed at CO) Several transceiver architectures are going to be discussed in the following slides: The targeted modulation format is DPSK/BPSK, although other multilevel modulations can be used Channel selection is performed by tuning the local laser to the right wavelength and filtered by the electrical filters ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 10 / 27
  • 15. Operation specifications Bitrate fixed at 1 Gb/s, to directly transmit the common EPON protocol over fiber Downstream modulation format to be used is PSK, because of its good trade-off between performances and simplicity Upstream modulation format PSK preferred IM can be also used with an asymmetrical up/down data rate to not to penalize optical power budget Digital and analog signal processing adopted against impairments Assume a double fiber network, avoiding Rayleigh backscattering ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 11 / 27
  • 16. Transceiver architectures proposed A D G B H E C F I Architectures A, C, E and G are intended for BPSK modulation DPSK modulation format has to be used in architectures B, D, F, and I Polarization is managed at OLT for architectures A, B, E, F, G, H and I In transceivers C and D a PBS used for achieving polarization diversity For digital approaches (A, C, E, G), Inside digital I and Q post-processing several basic operations are performed: phase estimation frequency estimation and control data estimation polarization switching combination ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 12 / 27
  • 17. Transceiver comparison Arch. Phase handling Polarization handling Processing Sens. penalty Linewidth tolerance Cost A 90◦ hybrid Switch at CO Digital 3 dB 5 MHz Med./High B 90◦ hybrid Switch at CO Analog 4 dB 5 MHz Med./High C 90◦ hybrid PBS Digital 0 dB 5 MHz Very high D 90◦ hybrid PBS Analog 1 dB 5 MHz Very high E Switch (Scr.) Switch at CO Digital 6 dB 1.8 MHz Medium F Switch (Scr.) Switch at CO Analog 7 dB 1.8 MHz Medium G Switch (Dir.) Switch at CO Digital 6 dB 3.4 MHz Low H Switch (Dir.) Switch at CO Analog 7 dB 3.4 MHz Low I OPLL Switch at CO Analog 4 dB 675 kHz Low Architecture with 90◦ hybrids a PBS and DSP (C): No additional penalty with respect to an ideal system Achieves high linewidth tolerance It is costly because it implies the duplication of many components needed Its cost can be low if novel fabrication techniques are used [15] Direct-drive time-switching (G): High penalty (6 dB) High linewidth tolerance Reduced complexity and cost Requires a fully engineered laser capable to be phase modulated OPLL approach (I): Low complexity Lower linewidth tolerance (675 kHz) Delay associated to the optical path length Local laser should be embedded with the optical reception front-end ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 13 / 27
  • 18. Transceiver comparison Arch. Phase handling Polarization handling Processing Sens. penalty Linewidth tolerance Cost A 90◦ hybrid Switch at CO Digital 3 dB 5 MHz Med./High B 90◦ hybrid Switch at CO Analog 4 dB 5 MHz Med./High C 90◦ hybrid PBS Digital 0 dB 5 MHz Very high D 90◦ hybrid PBS Analog 1 dB 5 MHz Very high E Switch (Scr.) Switch at CO Digital 6 dB 1.8 MHz Medium F Switch (Scr.) Switch at CO Analog 7 dB 1.8 MHz Medium G Switch (Dir.) Switch at CO Digital 6 dB 3.4 MHz Low H Switch (Dir.) Switch at CO Analog 7 dB 3.4 MHz Low I OPLL Switch at CO Analog 4 dB 675 kHz Low Architecture with 90◦ hybrids a PBS and DSP (C): No additional penalty with respect to an ideal system Achieves high linewidth tolerance It is costly because it implies the duplication of many components needed Its cost can be low if novel fabrication techniques are used [15] Direct-drive time-switching (G): High penalty (6 dB) High linewidth tolerance Reduced complexity and cost Requires a fully engineered laser capable to be phase modulated OPLL approach (I): Low complexity Lower linewidth tolerance (675 kHz) Delay associated to the optical path length Local laser should be embedded with the optical reception front-end ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 14 / 27
  • 19. Outline Introduction Transceiver architectures Case studies Conclusions ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 15 / 27
  • 20. Case studies Two cases of future deployment were tested in the laboratory: Subband WDM tree PON, featuring wavelength grooming [16] Ring-tree ultra-dense WDM-PON, with transparent remote nodes [17] Both networks are based on the ultra-dense WDM concept, aiming to give service to a high number of users (around 1000), at very high speed (1 Gb/s) ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 16 / 27
  • 21. Subband WDM tree PON 4 GHz channel spacing and 1 Gb/s data rate 32 channels accommodated in an ITU-T G.694.1 100-GHz D-WDM channel Serve 40 x 32 = 1280 users ⇒ more than 1 Tb/s 25 km fiber spool simulated the access trunk fiber Losses at the AWG were measured to be 6.47 dB 1:32 power splitter, adding 16 dB losses Total network losses were measured to be 27.67 dB 9 dBm optical output power at CO −38.7 dBm of sensitivity (BER=10−9 ) Power budget calculated to be 47.7 dB ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 17 / 27
  • 22. Ring-tree ultra-dense WDM PON Totally passive and transparent Simple and resilient architecture ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 18 / 27
  • 23. Experimental evaluation Network designed to offer connectivity to 1024 users 4-node configuration 8 secondary trees with 1:128 splitting factor 4 GHz channel spacing Three different cases were investigated: RN1, RN2 and RN4 ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 19 / 27
  • 24. Results and discussion BER = 10−9 BER = 10−3 RN1 RN2 RN4 RN1 RN2 RN4 Sensitivity −43 dBm −41.3 dBm - −49.1 dBm −49.3 dBm −49.1 dBm Link Losses 39.4 dB 41 dB 44.2 dB 39.4 dB 41 dB 44.2 dB Power Budget 42.9 dB 41.2 dB - 49 dB 49.2 dB 49 dB In normal operation (BER = 10−9 ), the maximum power budget reached is 41.2 dB arriving to RN2 In resilient mode FEC codes are used to overcome the possible fiber cut Using FEC codes BER = 10−3 is operable and RN4 can be reached, featuring a power budget of 49 dB ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 20 / 27
  • 25. Outline Introduction Transceiver architectures Case studies Conclusions ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 21 / 27
  • 26. Conclusions The overall goal of this study was to find whether homodyne transceivers are affordable or not for upgrading the current standard PONs It was found that they are more power and bandwidth efficient Several transceiver architectures have been proposed and discussed Trade-off between performances and cost is difficult to overcome Time-switched diversity transceiver has been implemented Upgrading of PON architectures has been discussed for implementing full ultra-dense WDM networks Laboratory testbeds have been developed for two network concepts The proposed topologies have been demonstrated to be feasible, achieving transmission of up to 1 Gb/s in links higher than 25 km ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 22 / 27
  • 27. Future lines Some improvements to be achieved, resulting in a step forward: Compact coherent transceiver State of polarization mismatch between local oscillator and received signal Careful design of the modulation formats to be used Full bidirectionality over a single fiber Rayleigh backscattering Light reflections Spectrum management Spectral efficiency maximization Wavelength monitoring, control and stabilization ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 23 / 27
  • 28. Thank you!! Time for questions... ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 24 / 27
  • 29. Bibliography I [1] L. G. Kazovsky. Decision-driven phase-locked loop for optical homodyne receivers: performance analysis and laser linewidth requirements. IEEE / OSA Journal of Lightwave Technology, 3:1238, 1985. [2] S. Norimatsu, K. Iwashita, and K. Sato. Psk optical homodyne detection using external cavity laser diodes in costas loop. IEEE Photonics Technology Letters, 2(5), 1990. [3] L. G. Kazovsky. Balanced phase-locked loops for optical homodyne receivers: performance analysis, design considerations, and laser linewidth requirements. IEEE / OSA Journal of Lightwave Technology, 4:182, 1986. [4] S. Camatel, V. Ferrero, and P. Poggiolini. 2-psk homodyne receiver based on a decision driven architecture and a sub-carrier optical pll. In Proceedings of the Conference on Optical Fiber Communication and the National Fiber Optic Engineers Conference, 2006 (OFC/NFOEC 2006), Anaheim (CA), March 2006. [5] Y. H. Cheng, T. Okoshi, and O. Ishida. Performance analysis and experiment of a homodyne receiver insensitive to both polarization and phase fluctuations. IEEE / OSA Journal of Lightwave Technology, 7:368–374, 1989. [6] M. G. Taylor. Phase estimation methods for optical coherent detection using digital signal processing. IEEE / OSA Journal of Lightwave Technology, 27:901–913, 2009. [7] M. G. Taylor. Accurate digital phase estimation process for coherent detection using a parallel digital processor. In Proceedings of 31th European Conference on Optical Communications (ECOC 2005), Glasgow (Scotland), September 2005. ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 25 / 27
  • 30. Bibliography II [8] R. Noe. Phase noise-tolerant synchronous qpsk/bpsk baseband-type intradyne receiver concept with feedforward carrier recovery. IEEE / OSA Journal of Lightwave Technology, 23(2), 2005. [9] D. Van den Borne, C. R. S. Fludger, T. Duthel, T. Wuth, E. D. Schmidt, C. Schulien, E. Gottwald, G. D. Khoe, and H. de Waardt. Carrier phase estimation for coherent equalization of 43-gb/s polmuxnrz-dqpsk transmission with 10.7-gb/s nrz neighbours. In Proceedings of 33th European Conference on Optical Communications (ECOC 2007), Berlin (Germany), September 2007. [10] M. Seimetz. Laser linewidth limitations for optical systems with high-order modulation employing feed forward digital carrier phase estimation. In Proceedings of the Conference on Optical Fiber Communication and the National Fiber Optic Engineers Conference, 2008 (OFC/NFOEC 2008), San Diego (CA), March 2008. [11] J. M. Fabrega and J. Prat. Homodyne receiver prototype with time-switching phase diversity and feedforward analog processing. OSA Optics Letters, 32(5), 2007. [12] J. M. Fabrega and J. Prat. Experimental investigation of channel crosstalk in a time-switched phase diversity optical homodyne receiver. OSA Optics Letters, 34(4), 2009. [13] A. Ramaswamy, L. A. Johansson, J. Klamkin, C. Sheldon, H. F. Chou, M. J. Rodwel, L. A. Coldren, and J. E. Bowers. Coherent receiver based on a broadband phase-lock loop. In Proceedings of the Conference on Optical Fiber Communication and the National Fiber Optic Engineers Conference, 2007 (OFC/NFOEC 2007), Anaheim (CA), March 2007. [14] J. M. Fabrega and J. Prat. Simple low-cost homodyne receiver. In Proceedings of 33th European Conference on Optical Communications (ECOC 2007), Berlin (Germany), September 2007. ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 26 / 27
  • 31. Bibliography III [15] N. Keil, H. Yao, C. Zawadzki, W. Doldissen, W. Schlaak, M. Mohrle, and D. Schmidt. Polymer as integration platform for low-cost devices in future optical networks. In Proceedings NOC06, Berlin (Germany), July 2006. [16] C. Bock, J. M. Fabrega, and J. Prat. Ultra-dense wdm pon based on homodyne detection and local oscillator reuse for upstream transmission. In Proceedings of 32th European Conference on Optical Communications (ECOC 2006), Cannes (France), September 2006. [17] J. M. Fabrega and J. Prat. Ultra-dense, transparent and resilient ring-tree access network using coupler-based remote nodes and homodyne transceivers. In Proceedings of International Conference on Transparent Optical Networks ICTON’09, Ponta Delgada (Azores, Portugal), July 2009. ` J. Prat, J. M. Fabrega, R. Freund (UPC-HHI) Homodyne UD-WDM PONs June 2010 27 / 27