## Mitigation of Rayleigh backscattering in 10-Gb/s downstream and 2.5-Gb/s upstream DWDM 100-km long-reach PONs |

Optics Express, Vol. 19, Issue 6, pp. 4970-4976 (2011)

http://dx.doi.org/10.1364/OE.19.004970

Acrobat PDF (928 KB)

### Abstract

Long-reach passive optical network (LR-PON) is considered as a promising technology towards higher capacity and extended coverage optical system. We propose and demonstrate a LR-PON with the capability of Rayleigh backscattering (RB) noise mitigation. By using the upstream signal wavelength-transition generated by a dual-parallel Mach-Zehnder modulator (DP-MZM) based colorless optical networking unit (ONU), the spectral overlap among the upstream signal and the RB noises can be minimized. Hence, due to the achievement of effective RB mitigation, a 100 km LR-PON with a high split-ratio of 512 is demonstrated using 10 Gb/s non-return-to-zero (NRZ) downstream and 2.5 Gb/s NRZ upstream signals. Detail analysis of the wavelength-transition generation is presented.

© 2011 OSA

## 1. Introduction

1. I. Van de Voorde, C. M. Martin, J. Vandewege, and X. Z. Oiu, “The SuperPON demonstrator: an exploration of possible evolution paths for optical access networks,” IEEE Commun. Mag. **38**(2), 74–82 (2000). [CrossRef]

8. C. W. Chow, G. Talli, and P. D. Townsend, “Rayleigh noise reduction in 10-Gb/s DWDM-PONs by wavelength detuning and phase-modulation-induced spectral broadening,” IEEE Photon. Technol. Lett. **19**(6), 423–425 (2007). [CrossRef]

9. Z. Li, Y. Dong, Y. Wang, and C. Lu, “A novel PSK—Manchester modulation format in 10-Gb/s passive optical network system with high tolerance to beat interference noise,” IEEE Photon. Technol. Lett. **17**(5), 1118–1120 (2005). [CrossRef]

## 2. RB noise sources in the carrier-distributed LR-PON

## 3. Principle of wavelength-translation generated by a DP-MZM

_{s}(10 GHz) via a radio-frequency (RF) mixer. It was then split into two paths by a 90° hybrid power-splitter and drove the DP-MZM in-phase and quadrature-phase at the upper MZM

_{1}and the lower MZM

_{2}respectively. We can consider each MZM consists of 2 phase modulators arranged in a MZ structure. The output E-field for the upper arm in the MZM

_{1}is shown in Eq. (1).where

*ω*and

_{0}*Δφ*are angular frequency and phase difference induced by the applied voltage to the phase modulator respectively. In order to simplify the analysis, we assume the applied electrical signal is sinusoidal with amplitude and frequency of

*m*and

*ω*respectively. Hence, the voltage induced phase change to the upper phase modulator in MZM

_{RF}_{1}is shown in Eq. (2).By substituting Eq. (2) into Eq. (1), we have Eq. (3).

*J*is the Bessel function. By using the Bessel function identifies in [10], we then expand Eq. (3) and neglect the higher order (

_{n}(m)*n*≥ 4) terms since their values are small. The output E-field becomes Eq. (4).

_{1}is opposite to that of the upper phase modulator, the phase shift is negative as shown in Eq. (5).By substituting Eq. (5) into Eq. (1), we have Eq. (6).

*n*≥ 4) terms can be neglected.

_{1}is V

_{π}, the Bessel terms in Eq. (7) will rotate by π, as shown in Fig. 2(c). Finally, Fig. 2(d) presents the combined output of MZM

_{1}.

_{2}, since the applied electrical signal is π/2 phase-shifted by the 90° power splitter, the voltage-induced phase change to the upper phase modulator is shown in Eq. (8).

_{2}(Fig. 2(e)) is shown in Eq. (9).

_{2}is opposite to that of its upper phase modulator, the phase shift is shown in Eq. (10).

_{2}is V

_{π}, the Bessel terms in Eq. (11) will rotate by π, as shown in Fig. 2(g). Figure 2(h) shows the combined output of MZM

_{2}.

_{3}of the DP-MZM is V

_{π}/2, the Bessel terms shown in Fig. 2(h) will rotate clockwise by π/2, and will become Fig. 2(i). Hence, by combining the signal outputs from MZM

_{1}and MZM

_{2}, we can observe a single sideband signal with suppressed carrier (at

*ω*), as shown in Fig. 2(j). Although frequency component at

_{0}-ω_{RF}*ω*also appears, however its magnitude is small and can be neglected.

_{0}+ 3ω_{RF}## 4. Network experiment

^{31}-1 in-phase and quadrature-phase respectively as described in section 3. Semiconductor based modulator could be more practical in real network implementation [11

11. O. Leclerc, P. Brindel, D. Rouvillain, E. Pincemin, B. Dany, E. Desurvire, C. Duchet, E. Boucherez, and S. Bouchoule, “40 Gbit/s polarization-insensitive and wavelength-independent InP Mach-Zehnder modulator for all-optical regeneration,” Electron. Lett. **35**(9), 730–732 (1999). [CrossRef]

^{−7}. BER cannot be measured at split-ratio of 512 at the conventional NRZ case due to the nearly complete eye-closure (inset of Fig. 4(b)). Figure 4(c) shows the BER of the downstream 10 Gb/s (up to 512 splits) NRZ signal, with the eye-diagram after 100 km SMF.

## 5. Conclusion

## Acknowledgements

## References and links

1. | I. Van de Voorde, C. M. Martin, J. Vandewege, and X. Z. Oiu, “The SuperPON demonstrator: an exploration of possible evolution paths for optical access networks,” IEEE Commun. Mag. |

2. | D. B. Payne and R. P. Davey, “The Future of fiber access systems,” BT Technol. J. |

3. | G. Talli, C. W. Chow, E. K. MacHale, and P. D. Townsend, “Rayleigh noise mitigation in long-reach hybrid DWDM-TDM PONs,” J. Opt. Netw. |

4. | I. T. Monroy, F. Öhman, K. Yvind, R. Kjaer, C. Peucheret, A. M. J. Koonen, and P. Jeppesen, “85 km long reach PON system using a reflective SOA-EA modulator and distributed Raman fiber amplification,” Proc. LEOS Annual Meeting, Paper WEE4 (2006). |

5. | C. W. Chow, C. H. Yeh, C. H. Wang, F. Y. Shih, C. L. Pan, and S. Chi, “WDM extended reach passive optical networks using OFDM-QAM,” Opt. Express |

6. | C. H. Wang, C. W. Chow, C. H. Yeh, C. L. Wu, S. Chi, and C. Lin, “Rayleigh noise mitigation using single sideband modulation generated by a dual-parallel MZM for carrier distributed PON,” IEEE Photon. Technol. Lett. |

7. | C. W. Chow, and C. H. Yeh, “Long-reach WDM PONs,” Proc. IEEE Photonics Society Annual Meeting, Invited Talk WA1 (2010). |

8. | C. W. Chow, G. Talli, and P. D. Townsend, “Rayleigh noise reduction in 10-Gb/s DWDM-PONs by wavelength detuning and phase-modulation-induced spectral broadening,” IEEE Photon. Technol. Lett. |

9. | Z. Li, Y. Dong, Y. Wang, and C. Lu, “A novel PSK—Manchester modulation format in 10-Gb/s passive optical network system with high tolerance to beat interference noise,” IEEE Photon. Technol. Lett. |

10. | M. T. Abuelma’atti, “Large signal analysis of the Mach-Zehnder modulator with variable bias,” Proc. Natl. Sci. Counc. ROC(A) |

11. | O. Leclerc, P. Brindel, D. Rouvillain, E. Pincemin, B. Dany, E. Desurvire, C. Duchet, E. Boucherez, and S. Bouchoule, “40 Gbit/s polarization-insensitive and wavelength-independent InP Mach-Zehnder modulator for all-optical regeneration,” Electron. Lett. |

**OCIS Codes**

(060.0060) Fiber optics and optical communications : Fiber optics and optical communications

(060.2360) Fiber optics and optical communications : Fiber optics links and subsystems

**ToC Category:**

Fiber Optics and Optical Communications

**History**

Original Manuscript: January 12, 2011

Revised Manuscript: February 7, 2011

Manuscript Accepted: February 7, 2011

Published: March 1, 2011

**Citation**

C. W. Chow and C. H. Yeh, "Mitigation of Rayleigh backscattering in 10-Gb/s downstream and 2.5-Gb/s upstream DWDM 100-km long-reach PONs," Opt. Express **19**, 4970-4976 (2011)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-6-4970

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### References

- I. Van de Voorde, C. M. Martin, J. Vandewege, and X. Z. Oiu, “The SuperPON demonstrator: an exploration of possible evolution paths for optical access networks,” IEEE Commun. Mag. 38(2), 74–82 (2000). [CrossRef]
- D. B. Payne and R. P. Davey, “The Future of fiber access systems,” BT Technol. J. 20(4), 104–114 (2002). [CrossRef]
- G. Talli, C. W. Chow, E. K. MacHale, and P. D. Townsend, “Rayleigh noise mitigation in long-reach hybrid DWDM-TDM PONs,” J. Opt. Netw. 6(6), 765–776 (2007). [CrossRef]
- I. T. Monroy, F. Öhman, K. Yvind, R. Kjaer, C. Peucheret, A. M. J. Koonen, and P. Jeppesen, “85 km long reach PON system using a reflective SOA-EA modulator and distributed Raman fiber amplification,” Proc. LEOS Annual Meeting, Paper WEE4 (2006).
- C. W. Chow, C. H. Yeh, C. H. Wang, F. Y. Shih, C. L. Pan, and S. Chi, “WDM extended reach passive optical networks using OFDM-QAM,” Opt. Express 16(16), 12096–12101 (2008). [CrossRef] [PubMed]
- C. H. Wang, C. W. Chow, C. H. Yeh, C. L. Wu, S. Chi, and C. Lin, “Rayleigh noise mitigation using single sideband modulation generated by a dual-parallel MZM for carrier distributed PON,” IEEE Photon. Technol. Lett. 22(11), 820–822 (2010). [CrossRef]
- C. W. Chow, and C. H. Yeh, “Long-reach WDM PONs,” Proc. IEEE Photonics Society Annual Meeting, Invited Talk WA1 (2010).
- C. W. Chow, G. Talli, and P. D. Townsend, “Rayleigh noise reduction in 10-Gb/s DWDM-PONs by wavelength detuning and phase-modulation-induced spectral broadening,” IEEE Photon. Technol. Lett. 19(6), 423–425 (2007). [CrossRef]
- Z. Li, Y. Dong, Y. Wang, and C. Lu, “A novel PSK—Manchester modulation format in 10-Gb/s passive optical network system with high tolerance to beat interference noise,” IEEE Photon. Technol. Lett. 17(5), 1118–1120 (2005). [CrossRef]
- M. T. Abuelma’atti, “Large signal analysis of the Mach-Zehnder modulator with variable bias,” Proc. Natl. Sci. Counc. ROC(A) 25, 254–258 (2001).
- O. Leclerc, P. Brindel, D. Rouvillain, E. Pincemin, B. Dany, E. Desurvire, C. Duchet, E. Boucherez, and S. Bouchoule, “40 Gbit/s polarization-insensitive and wavelength-independent InP Mach-Zehnder modulator for all-optical regeneration,” Electron. Lett. 35(9), 730–732 (1999). [CrossRef]

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