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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 20, Iss. 26 — Dec. 10, 2012
  • pp: B452–B461
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Mitigation of Rayleigh noise and dispersion in REAM-based WDM-PON using spectrum-shaping codes

Qi Guo and An V. Tran  »View Author Affiliations


Optics Express, Vol. 20, Issue 26, pp. B452-B461 (2012)
http://dx.doi.org/10.1364/OE.20.00B452


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Abstract

This paper presents a novel technique capable of Rayleigh backscattering (RB) mitigation and chromatic dispersion (CD) compensation for wavelength-division-multiplexed passive optical network (WDM-PON). The reduction of the interference caused by RB and CD in the uplink based on reflective electro-absorption modulator (REAM) is realized by the proposed correlative level (CL) coding. We investigate the RB-induced interferometric crosstalk for different fiber lengths. 10 Gb/s and 20 Gb/s transmissions over 70 km and 35 km fiber are demonstrated using the CL codes of dicode and modified duobinary (MD), respectively. Significant improvement in system resilience to backscattered seed light is verified for both dicode and MD coding. MD-coded signal also exhibits considerable robustness against the effects of CD.

© 2012 OSA

1. Introduction

2. Analysis of RB and CD in WDM-PON

3. Principle of correlative level (CL) coding

Since RBcw is the major RB interferer in the REAM-based WDM-PON, this paper only focuses on the RBcw suppression. For this purpose, we first derive the PSD of RBcw, mathematically expressed by the following [21

21. R. K. Staubli and P. Gysel, “Statistical Properties of Single-Mode Fiber Rayleigh Backscattered Intensity and Resulting Detector Current,” IEEE Trans. Commun. 40(6), 1091–1097 (1992). [CrossRef]

]:
S(ω)=Ib2(2πδ(ω)+2ΔωΔω2+ω2)
(7)
where Ib is the RBcw intensity and Δω denotes the laser linewidth. Equation (7) indicates that the bandwidth of RBcw is twice the Δω. Hence the cw interferer that occupies very narrow spectrum can be largely removed by a high-pass filter (HPF) if the signal energy is moved away from DC. This idea can be simply realized by processing the binary message with a DC-balanced code prior to modulation. A group of CL codes that can enable zero DC content have a typical coding transfer function as [22

22. P. Kabal and S. Pasupathy, “Partial response signaling,” IEEE. Trans. Commun. COM 23(9), 921–934 (1975). [CrossRef]

, 23

23. A. Lender, “Correlative digital communication techniques,” IEEE Trans. Commun. Technol. COM 12(4), 128–135 (1964). [CrossRef]

]
H(D)=(1D)(1+D)n
(8)
where D is 1-bit delay. When n equals to 0 and 1, the CL codes are called dicode and MD, respectively, whose spectra are plotted in Fig. 5(a)
Fig. 5 (a) Spectra of 20 Gb/s binary, dicode and MD signals, and diagrams of (b) dicode and (c) MD coding.
and compared with that of binary signal. Figures 5(b) and 5(c) illustrate the procedures of these two CL codes as simple delay-and-subtract lines. Both dicode and MD signals have three levels and can be simply converted back into binary signal by a full-wave rectifier, since the top and bottom levels of these two signals correspond to binary “0” and the middle level corresponds to binary “1”.

Apparently seen from Fig. 5(a), dicode reforms the power distribution of the binary signal by shifting the peak furthest away from DC among all three signals. Compared with mBnB and Manchester codes that also achieve DC null, the advantage of dicode code is zero overhead. MD signal has similar performance with duobinary signal which has found many applications in optical systems owing to its robustness to fiber impairments such as CD [24

24. X. Gu and L. C. Blank, “10 Gb/s unrepeatered three-level optical transmission over 100 km of standard fiber,” Electron. Lett. 29(25), 2209–2211 (1993). [CrossRef]

, 25

25. K. Yonenaga and S. Kuwano, “Dispersion-tolerant optical transmission system using duobinary transmitter and binary receiver,” J. Lightwave Technol. 15(8), 1530–1537 (1997). [CrossRef]

]. MD differs from duobinary in only the additional (1-D) term that forces the DC content to be null. As shown in Fig. 5(a), MD signal has about half the bandwidth of the binary signal. Therefore, besides RB suppression, MD signal is also expected to be tolerant against CD.

4. Experiments and results

The experimental setup to evaluate the upstream performance by dicode and MD coded signals is depicted in Fig. 6
Fig. 6 Experimental setup for transmission studies.
. Seed light at 1550 nm is generated by a DFB laser and launched into a length of SSMF. The output seed power is set to 3 dBm, which is sufficient to cover the link loss for maintaining the performance of SOA-REAM and low enough to avoid the severe degradation induced by Brillouin backscattering. The cw light injected into the SOA-REAM employed at the ONU is modulated by a 215 −1 pseudo-random binary sequence (PRBS) in the formats of NRZ, dicode and MD. The SOA-REAM is biased at 75 mA and −1.5 V with 3 Vpp electrical input. Figures 7 (a)
Fig. 7 Characteristics of SOA-REAM: (a) ASE spectrum and (b) frequency response.
and 7(b) show that the central wavelength of the SOA is 1554 nm and the REAM 3-dB modulation bandwidth is around 20 GHz, respectively. At the OLT side, 10% of the signal is tapped off for monitoring the received optical signal to RB ratio (OSRR). Then the remaining optical power is detected by an 18 GHz photodiode (PD) followed by two types of decision circuit depending on whether the signal is coded. The decision circuit for uncoded binary signal comprises a low-pass filter (LPF) with the bandwidth matched to bit rate to eliminate the out-of-band noise. The Dicode and MD circuits that have the same design use an HPF with cut-off frequency of 200 MHz to filter out the reflection noise without causing serious degradation on the signal. They also consist of a data-rate LPF same with the binary circuit and a full-wave rectifier for decoding the signal. Due to the lack of analog rectifier, signals are captured by a 15 GHz storage oscilloscope at 2 samples/bit with a length of 4 × 106 bits for digital filtering, rectification and bit error rate (BER) calculation. Thus, the receivers for the uncoded and coded signals are the same except the post-detection signal processing.

4.1 Experiments on data rate of 10 Gb/s

4.2 Experiments on data rate of 20 Gb/s

When the bit rate increases to 20 Gb/s, binary, dicode and MD signals are transmitted from the ONU in the experiments to compare their robustness against both fiber dispersion and RB noise. The system performance is evaluated by varying the fiber length from 5 to 35 km. Figure 9
Fig. 9 BER vs. transmission distance for 20 Gb/s uplink.
plots the BERs versus transmission distance, showing that error-free 20 Gb/s transmission over 35 km fiber can be enabled by MD coding with the help of 7% FEC. At BER of 5 × 10−4, the MD transmission achieves about 8 km and 13 km longer reach than the dicode and the binary transmission, respectively. Therefore, MD coding is a better choice for bandwidth-limited channel because it has the smallest bandwidth among these three signals.

5. Conclusions

References and links

1.

P. Healey, P. Townsend, C. Ford, L. Johnston, P. Townley, I. Lealman, L. Rivers, S. Perrin, and R. Moore, “Spectral slicing WDM-PON using wavelength-seeded reflective SOAs,” Electron. Lett. 37(19), 1181–1182 (2001). [CrossRef]

2.

K. M. Choi, J. S. Baik, and C. H. Lee, “Broad-band light source using mutually injected Fabry-Perot laser diodes for WDM-PON,” IEEE Photon. Technol. Lett. 17(12), 2529–2531 (2005). [CrossRef]

3.

E. K. MacHale, G. Talli, P. D. Townsend, A. Borghesani, I. Lealman, D. G. Moodie, and D. W. Smith, “Extended-reach PON employing 10Gbits/s integrated reflective EAM-SOA,” Proc. European Conference on Optical Communication (ECOC), paper Th.2.F.1 (2008).

4.

S. J. Park, G. Y. Kim, T. Park, E. H. Choi, S. H. Oh, Y. S. Baek, K. R. Oh, Y. J. Park, J. U. Shin, and H. K. Sung, “WDM-PON system based on the laser light injected reflective semiconductor optical amplifier,” Proc. European Conference on Optical Communication (ECOC), paper We3.3.6 (2005).

5.

C. Arellano, C. Bock, J. Prat, and K. D. Langer, “RSOA-based Optical Network Units for WDM-PON,” Proc. Optical Fiber Communication (OFC) Conference, paper OTuC1 (2006).

6.

W. Lee, M. Y. Park, S. H. Cho, J. H. Lee, C. Kim, G. Jeong, and B. W. Kim, “Bidirectional WDM-PON based on gain-saturated reflective semiconductor optical amplifiers,” IEEE Photon. Technol. Lett. 17(11), 2460–2462 (2005). [CrossRef]

7.

Q. Guo and A. V. Tran, “Demonstration of 40-Gb/s WDM-PON system using SOA-REAM and equalization,” IEEE Photon. Technol. Lett. 24(11), 951–953 (2012). [CrossRef]

8.

H. S. Kim, D. C. Kim, K. S. Kim, B. S. Choi, and O. K. Kwon, “10.7 Gb/s reflective electroabsorption modulator monolithically integrated with semiconductor optical amplifier for colorless WDM-PON,” Opt. Express 18(22), 23324–23330 (2010). [CrossRef] [PubMed]

9.

G. Girault, L. Bramerie, O. Vaudel, S. Lobo, P. Besnard, M. Joindot, J.-C. Simon, C. Kazmierski, N. Dupuis, A. Garreau, Z. Belfqih, and P. Chanclou, “10 Gbit/s PON demonstration using a REAM-SOA in a bidirectional fiber configuration up to 25 km SMF,” Proc. European Conference on Optical Communication (ECOC), paper P.6.08 (2008).

10.

S. Y. Kim, S. B. Jun, Y. Takushima, E. S. Son, and Y. C. Chung, “Enhanced performance of RSOA-based. WDMPON by using Manchester coding,” J. Opt. Netw. 6(6), 624–630 (2007). [CrossRef]

11.

M. Presi, A. Chiuchiarelli, R. Proietti, P. Choudhury, G. Contestabile, and E. Ciaramella, “Single Feeder Bidirectional WDM-PON with Enhanced Resilience to Rayleigh-Backscattering,” Proc. Optical Fiber Communication (OFC) Conference, paper OThG2 (2010).

12.

K. Y. Cho, A. Murakami, Y. J. Lee, A. Agata, Y. Takushima, and Y. C. Chung, “Demonstration of RSOA-based WDM PON operating at symmetric rate of 1.25 Gb/s with high reflection tolerance,” Proc. Optical Fiber Communication (OFC) Conference, paper OTuH4 (2008).

13.

M. Omella, V. Polo, J. Lazaro, B. Schrenk, and J. Prat, “10 Gb/s RSOA transmission by direct duobinary modulation,” Proc. European Conference on Optical Communication (ECOC), paper Tu.3.E.4 (2008).

14.

K. Y. Cho, Y. Takushima, and Y. C. Chung, “Enhanced chromatic dispersion tolerance of 11 Gbit/s RSOA-based WDM PON using 4-ary PAM signal,” Electron. Lett. 46(22), 1510–1511 (2010). [CrossRef]

15.

Q. Guo and A. V. Tran, “Mitigation of Rayleigh Noise and Dispersion in REAM-based WDM-PON using Partial-Response Signaling” Proc. European Conference on Optical Communication (ECOC), paper We.2.B.4 (2012).

16.

Q. Guo and A. V. Tran, “Level coding technique for a wavelength-division-multiplexed optical access system using a remodulation scheme,” Opt. Lett. 37(19), 4137–4139 (2012). [CrossRef] [PubMed]

17.

Q. Guo and A. Tran, “40 Gb/s Operation of SOA-REAM in Single-Feeder WDM-PON [Invited],” J. Opt. Commun. Netw. 4(11), B77–B84 (2012). [CrossRef]

18.

J. Xu, M. Li, and L. K. Chen, “Rayleigh Noise Reduction in 10-Gb/s Carrier-Distributed WDM-PONs Using In-Band Optical Filtering,” J. Lightwave Technol. 29(24), 3632–3639 (2011). [CrossRef]

19.

C. Arellano, K. Langer, and J. Prat, “Reflections and multiple Rayleigh backscattering in WDM single-fiber loopback access networks,” J. Lightwave Technol. 27(1), 12–18 (2009). [CrossRef]

20.

F. Devaux, Y. Sorel, and J. F. Kerdiles, “Simple measurement of fiber dispersion and of chirp parameter of intensity modulated light emitter,” J. Lightwave Technol. 11(12), 1937–1940 (1993). [CrossRef]

21.

R. K. Staubli and P. Gysel, “Statistical Properties of Single-Mode Fiber Rayleigh Backscattered Intensity and Resulting Detector Current,” IEEE Trans. Commun. 40(6), 1091–1097 (1992). [CrossRef]

22.

P. Kabal and S. Pasupathy, “Partial response signaling,” IEEE. Trans. Commun. COM 23(9), 921–934 (1975). [CrossRef]

23.

A. Lender, “Correlative digital communication techniques,” IEEE Trans. Commun. Technol. COM 12(4), 128–135 (1964). [CrossRef]

24.

X. Gu and L. C. Blank, “10 Gb/s unrepeatered three-level optical transmission over 100 km of standard fiber,” Electron. Lett. 29(25), 2209–2211 (1993). [CrossRef]

25.

K. Yonenaga and S. Kuwano, “Dispersion-tolerant optical transmission system using duobinary transmitter and binary receiver,” J. Lightwave Technol. 15(8), 1530–1537 (1997). [CrossRef]

OCIS Codes
(060.0060) Fiber optics and optical communications : Fiber optics and optical communications
(060.4250) Fiber optics and optical communications : Networks
(010.1350) Atmospheric and oceanic optics : Backscattering

ToC Category:
Access Networks and LAN

History
Original Manuscript: September 18, 2012
Revised Manuscript: November 2, 2012
Manuscript Accepted: November 8, 2012
Published: December 3, 2012

Virtual Issues
European Conference on Optical Communication 2012 (2012) Optics Express

Citation
Qi Guo and An V. Tran, "Mitigation of Rayleigh noise and dispersion in REAM-based WDM-PON using spectrum-shaping codes," Opt. Express 20, B452-B461 (2012)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-26-B452


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References

  1. P. Healey, P. Townsend, C. Ford, L. Johnston, P. Townley, I. Lealman, L. Rivers, S. Perrin, and R. Moore, “Spectral slicing WDM-PON using wavelength-seeded reflective SOAs,” Electron. Lett.37(19), 1181–1182 (2001). [CrossRef]
  2. K. M. Choi, J. S. Baik, and C. H. Lee, “Broad-band light source using mutually injected Fabry-Perot laser diodes for WDM-PON,” IEEE Photon. Technol. Lett.17(12), 2529–2531 (2005). [CrossRef]
  3. E. K. MacHale, G. Talli, P. D. Townsend, A. Borghesani, I. Lealman, D. G. Moodie, and D. W. Smith, “Extended-reach PON employing 10Gbits/s integrated reflective EAM-SOA,” Proc. European Conference on Optical Communication (ECOC), paper Th.2.F.1 (2008).
  4. S. J. Park, G. Y. Kim, T. Park, E. H. Choi, S. H. Oh, Y. S. Baek, K. R. Oh, Y. J. Park, J. U. Shin, and H. K. Sung, “WDM-PON system based on the laser light injected reflective semiconductor optical amplifier,” Proc. European Conference on Optical Communication (ECOC), paper We3.3.6 (2005).
  5. C. Arellano, C. Bock, J. Prat, and K. D. Langer, “RSOA-based Optical Network Units for WDM-PON,” Proc. Optical Fiber Communication (OFC) Conference, paper OTuC1 (2006).
  6. W. Lee, M. Y. Park, S. H. Cho, J. H. Lee, C. Kim, G. Jeong, and B. W. Kim, “Bidirectional WDM-PON based on gain-saturated reflective semiconductor optical amplifiers,” IEEE Photon. Technol. Lett.17(11), 2460–2462 (2005). [CrossRef]
  7. Q. Guo and A. V. Tran, “Demonstration of 40-Gb/s WDM-PON system using SOA-REAM and equalization,” IEEE Photon. Technol. Lett.24(11), 951–953 (2012). [CrossRef]
  8. H. S. Kim, D. C. Kim, K. S. Kim, B. S. Choi, and O. K. Kwon, “10.7 Gb/s reflective electroabsorption modulator monolithically integrated with semiconductor optical amplifier for colorless WDM-PON,” Opt. Express18(22), 23324–23330 (2010). [CrossRef] [PubMed]
  9. G. Girault, L. Bramerie, O. Vaudel, S. Lobo, P. Besnard, M. Joindot, J.-C. Simon, C. Kazmierski, N. Dupuis, A. Garreau, Z. Belfqih, and P. Chanclou, “10 Gbit/s PON demonstration using a REAM-SOA in a bidirectional fiber configuration up to 25 km SMF,” Proc. European Conference on Optical Communication (ECOC), paper P.6.08 (2008).
  10. S. Y. Kim, S. B. Jun, Y. Takushima, E. S. Son, and Y. C. Chung, “Enhanced performance of RSOA-based. WDMPON by using Manchester coding,” J. Opt. Netw.6(6), 624–630 (2007). [CrossRef]
  11. M. Presi, A. Chiuchiarelli, R. Proietti, P. Choudhury, G. Contestabile, and E. Ciaramella, “Single Feeder Bidirectional WDM-PON with Enhanced Resilience to Rayleigh-Backscattering,” Proc. Optical Fiber Communication (OFC) Conference, paper OThG2 (2010).
  12. K. Y. Cho, A. Murakami, Y. J. Lee, A. Agata, Y. Takushima, and Y. C. Chung, “Demonstration of RSOA-based WDM PON operating at symmetric rate of 1.25 Gb/s with high reflection tolerance,” Proc. Optical Fiber Communication (OFC) Conference, paper OTuH4 (2008).
  13. M. Omella, V. Polo, J. Lazaro, B. Schrenk, and J. Prat, “10 Gb/s RSOA transmission by direct duobinary modulation,” Proc. European Conference on Optical Communication (ECOC), paper Tu.3.E.4 (2008).
  14. K. Y. Cho, Y. Takushima, and Y. C. Chung, “Enhanced chromatic dispersion tolerance of 11 Gbit/s RSOA-based WDM PON using 4-ary PAM signal,” Electron. Lett.46(22), 1510–1511 (2010). [CrossRef]
  15. Q. Guo and A. V. Tran, “Mitigation of Rayleigh Noise and Dispersion in REAM-based WDM-PON using Partial-Response Signaling” Proc. European Conference on Optical Communication (ECOC), paper We.2.B.4 (2012).
  16. Q. Guo and A. V. Tran, “Level coding technique for a wavelength-division-multiplexed optical access system using a remodulation scheme,” Opt. Lett.37(19), 4137–4139 (2012). [CrossRef] [PubMed]
  17. Q. Guo and A. Tran, “40 Gb/s Operation of SOA-REAM in Single-Feeder WDM-PON [Invited],” J. Opt. Commun. Netw.4(11), B77–B84 (2012). [CrossRef]
  18. J. Xu, M. Li, and L. K. Chen, “Rayleigh Noise Reduction in 10-Gb/s Carrier-Distributed WDM-PONs Using In-Band Optical Filtering,” J. Lightwave Technol.29(24), 3632–3639 (2011). [CrossRef]
  19. C. Arellano, K. Langer, and J. Prat, “Reflections and multiple Rayleigh backscattering in WDM single-fiber loopback access networks,” J. Lightwave Technol.27(1), 12–18 (2009). [CrossRef]
  20. F. Devaux, Y. Sorel, and J. F. Kerdiles, “Simple measurement of fiber dispersion and of chirp parameter of intensity modulated light emitter,” J. Lightwave Technol.11(12), 1937–1940 (1993). [CrossRef]
  21. R. K. Staubli and P. Gysel, “Statistical Properties of Single-Mode Fiber Rayleigh Backscattered Intensity and Resulting Detector Current,” IEEE Trans. Commun.40(6), 1091–1097 (1992). [CrossRef]
  22. P. Kabal and S. Pasupathy, “Partial response signaling,” IEEE. Trans. Commun. COM23(9), 921–934 (1975). [CrossRef]
  23. A. Lender, “Correlative digital communication techniques,” IEEE Trans. Commun. Technol. COM12(4), 128–135 (1964). [CrossRef]
  24. X. Gu and L. C. Blank, “10 Gb/s unrepeatered three-level optical transmission over 100 km of standard fiber,” Electron. Lett.29(25), 2209–2211 (1993). [CrossRef]
  25. K. Yonenaga and S. Kuwano, “Dispersion-tolerant optical transmission system using duobinary transmitter and binary receiver,” J. Lightwave Technol.15(8), 1530–1537 (1997). [CrossRef]

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