OSA's Digital Library

Optics Express

Optics Express

  • Editor: Martijn de Sterke
  • Vol. 16, Iss. 20 — Sep. 29, 2008
  • pp: 15759–15764
« Show journal navigation

10.7 Gb/s uncompensated transmission over a 470 km hybrid fiber link with in-line SOAs using MLSE and duobinary signals

John D. Downie, Jason Hurley, and Yihong Mauro  »View Author Affiliations


Optics Express, Vol. 16, Issue 20, pp. 15759-15764 (2008)
http://dx.doi.org/10.1364/OE.16.015759


View Full Text Article

Acrobat PDF (95 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

We experimentally demonstrate uncompensated 8-channel wavelength division multiplexing (WDM) and single channel transmission at 10.7 Gb/s over a 470 km hybrid fiber link with in-line semiconductor optical amplifiers (SOAs). Two different forms of the duobinary modulation format are investigated and compared. Maximum Likelihood Sequence Estimation (MLSE) receiver technology is found to significantly mitigate nonlinear effects from the SOAs and to enable the long transmission, especially for optical duobinary signals derived from differential phase shift keying (DPSK) signals directly detected after narrowband optical filter demodulation. The MLSE also helps to compensate for a non-optimal Fabry-Perot optical filter demodulator.

© 2008 Optical Society of America

1. Introduction

Semiconductor optical amplifiers (SOAs) have long been attractive as small and potentially low-cost amplification devices for metro and regional network systems. Duobinary modulation formats are generally characterized by high dispersion tolerance which can be exploited to allow simple uncompensated transmission over longer distances that are practical for these networks. The most commonly used form of duobinary is low-pass filtering (LPF) duobinary [1

1. S. Kuwano, K. Yonenaga, and K. Iwashita, “10 Gbit/s Repeaterless Transmission Experiment of Optical Duobinary Modulated Signal,” Electron. Lett. 31, 1359–1361 (1995). [CrossRef]

]. Another variant is optical duobinary which is generated when a transmitted DPSK signal is demodulated with a narrowband optical filter in the receiver [2

2. D. Penninckx, H. Bissessur, P. Brindel, E. Gohin, and F. Bakhti, “Optical differential phase shift keying (DPSK) direct detection considered as a duobinary signal,” European Conference on Optical Communications (ECOC 2001), Amsterdam, The Netherlands, Paper We.P.40, (2001).

]. Moreover, DPSK signals have been shown under some conditions to suppress SOA-induced nonlinear impairments [3

3. P. S. Cho and J. B. Khurgin, “Suppression of cross-gain modulation in SOA using RZ-DPSK modulation format,” IEEE Photon. Technol. Lett. 15, 162–164 (2003). [CrossRef]

,4

4. X. Wei, Y. Su, X. Liu, J. Leuthold, and S. Chandrasekhar, “10-Gb/s RZ-DPSK Transmitter Using a Saturated SOA as a Power Booster and Limiting Amplifier,” IEEE Photon. Technol. Lett. 16, 1582–1584 (2004). [CrossRef]

]. Consequently, the optical duobinary signal format has previously been investigated for WDM transmission over metro and regional systems with in-line SOAs [5

5. A. D’Errico, V. Donzella, G. Contestabile, S. Betti, V. Carrozzo, F. Curti, M. Guglielmucci, and E. Ciaramella, “Field-trial of SOA-based WDM-DPSK 8x10 Gbit/s system over 300km with conventional amplification span,” Electron. Lett. 43, 404–405 (2007). [CrossRef]

,6

6. J. D. Downie, J. Hurley, M. Sauer, S. Raghavan, and S. Lobanov, “Uncompensated WDM transmission of 10.7 Gbit/s directly detected DPSK over 300 km standard single-mode fibre and through 6 SOAs,” European Conference on Optical Communication (ECOC 2007), Berlin, Germany, Paper P076, (2007). [CrossRef]

].

2. Experimental configuration

The transmission system experimental set-up is shown schematically in Fig. 1. Up to eight wavelengths in the 1530–1536 nm range and spaced by 100 GHz were modulated together with a Mach-Zehnder modulator (MZM) in either the DPSK or LPF duobinary format. The bit rate was 10.7 Gb/s and we used a pseudo-random bit sequence (PRBS) of length 231 -1. The channels were first fully de-correlated with 10 km of standard single-mode fiber and then launched into the first span with total launch power controlled by an erbium doped fiber amplifier (EDFA) and variable optical attenuator (VOA). The launch power was varied to determine the optimal condition balancing OSNR and nonlinear impairments.

Fig. 1. Experimental set-up for uncompensated transmission over 470 km hybrid fiber link with 6 SOAs.

Fig. 2. Dispersion tolerance data for LPF duobinary and optical duobinary transmitters measured as the required OSNR to achieve a BER of 1×10-3 with a standard receiver.

Fig. 3. Net link loss as a function of total launch power into first span of the hybrid fiber link

Two commercially available receivers were compared in the system experiments to determine and illustrate the compensation capability of MLSE for SOA-induced nonlinear effects. One was a standard receiver with PIN photodetector, trans-impedance amplifier, and associated clock and data recovery circuitry. The second receiver was from the same manufacturer, but had MLSE-EDC circuitry in the back-end electronics. The MLSE receiver digital equalizer comprises a 3 bit A/D converter operating at up to 25 Gsamples/s and a four-state (memory m=2) Viterbi decoder.

3. Experimental results

Fig. 4. BER values vs. total launch power into first span for optical duobinary signals over 470 km hybrid fiber link. (a) Single channel, (b) WDM system.

For low launch powers in the SOA linear regime, the performance advantage of the MLSE receiver with the optical duobinary signals in both single channel and WDM systems is due to partial compensation of chromatic dispersion and the non-optimal demodulation filter impairments. As the launch power into the first span is increased, the single channel system is limited by SGM from the SOAs with the standard receiver to an optimal launch power of about -2 dBm into the first span. The MLSE receiver can significantly increase the SGM tolerance for the single channel optical duobinary as was also observed earlier [11

11. J. D. Downie and J. Hurley, “Performance of an MLSE-EDC Receiver with SOA-induced Nonlinear Impairments,” IEEE Photon. Technol. Lett. , 20, 1326–1328 (2008). [CrossRef]

], in this case allowing a higher optimal launch power by about 7 dB. For the 8-channel WDM system, the MLSE receiver again significantly alleviates SGM effects which still appear to limit the launch power with the standard receiver. In this case, the MLSE allows a higher optimal launch power by about 5 dB, and the signals are ultimately limited by XGM rather than SGM with the MLSE receiver. For both single channel and WDM systems, the MLSE receiver produces BER values at optimal launch powers more than an order of magnitude lower than the standard receiver.

The same results measured for BER as a function of total launch power into the first span with the LPF duobinary signals are shown in Fig. 5. In this case, we observe that the MLSE receiver allows a higher optimal launch power for the single channel system by about 4–5 dB by mitigating the SGM impairment incurred in the SOAs. For the WDM system, the launch power is mainly limited by XGM for both the standard and MLSE receivers and the MLSE appears to offer only a minor nonlinear advantage of 1-2 dB in optimal total launch power. In this case, the lower BER obtained with the MLSE receiver is largely by virtue of partial dispersion compensation.

Fig. 5. BER values vs. total launch power into first span for LPF duobinary signals over 470 km hybrid fiber link. (a) Single channel, (b) WDM system.

A direct comparison of the WDM systems using the MLSE receiver with the two duobinary formats is shown in Fig. 6. The results in Fig. 6(a) for channel #5 show the optimal total launch power was about 11–12 dBm for both modulation formats, corresponding to OSNR values of about 24 dB. The launch power was mainly limited by cross-channel nonlinear effects in the SOAs, and perhaps partially by nonlinear phase noise for the optical duobinary format [3

3. P. S. Cho and J. B. Khurgin, “Suppression of cross-gain modulation in SOA using RZ-DPSK modulation format,” IEEE Photon. Technol. Lett. 15, 162–164 (2003). [CrossRef]

,4

4. X. Wei, Y. Su, X. Liu, J. Leuthold, and S. Chandrasekhar, “10-Gb/s RZ-DPSK Transmitter Using a Saturated SOA as a Power Booster and Limiting Amplifier,” IEEE Photon. Technol. Lett. 16, 1582–1584 (2004). [CrossRef]

]. These results suggest that any XGM tolerance advantage of DPSK in the back-to-back state may be lost or reversed in the presence of the large uncompensated dispersion of the link. All 8 channels were measured at the optimal launch power levels and the WDM results expressed as Q values are given in Fig. 6(b). Both formats had Q values well above the assumed enhanced FEC threshold with margins of about 3 dB for optical duobinary and 4 dB for LPF duobinary.

Fig. 6. (a) BER vs. total launch power into first span for channel #5 with both WDM systems, (b) Q values for all 8 channels with both formats.

4. Summary and conclusions

References and links

1.

S. Kuwano, K. Yonenaga, and K. Iwashita, “10 Gbit/s Repeaterless Transmission Experiment of Optical Duobinary Modulated Signal,” Electron. Lett. 31, 1359–1361 (1995). [CrossRef]

2.

D. Penninckx, H. Bissessur, P. Brindel, E. Gohin, and F. Bakhti, “Optical differential phase shift keying (DPSK) direct detection considered as a duobinary signal,” European Conference on Optical Communications (ECOC 2001), Amsterdam, The Netherlands, Paper We.P.40, (2001).

3.

P. S. Cho and J. B. Khurgin, “Suppression of cross-gain modulation in SOA using RZ-DPSK modulation format,” IEEE Photon. Technol. Lett. 15, 162–164 (2003). [CrossRef]

4.

X. Wei, Y. Su, X. Liu, J. Leuthold, and S. Chandrasekhar, “10-Gb/s RZ-DPSK Transmitter Using a Saturated SOA as a Power Booster and Limiting Amplifier,” IEEE Photon. Technol. Lett. 16, 1582–1584 (2004). [CrossRef]

5.

A. D’Errico, V. Donzella, G. Contestabile, S. Betti, V. Carrozzo, F. Curti, M. Guglielmucci, and E. Ciaramella, “Field-trial of SOA-based WDM-DPSK 8x10 Gbit/s system over 300km with conventional amplification span,” Electron. Lett. 43, 404–405 (2007). [CrossRef]

6.

J. D. Downie, J. Hurley, M. Sauer, S. Raghavan, and S. Lobanov, “Uncompensated WDM transmission of 10.7 Gbit/s directly detected DPSK over 300 km standard single-mode fibre and through 6 SOAs,” European Conference on Optical Communication (ECOC 2007), Berlin, Germany, Paper P076, (2007). [CrossRef]

7.

J. D. Downie, J. Hurley, and Y. Mauro, “Uncompensated 10.7 Gb/s Transmission over a 470 km Hybrid Fiber Link with In-Line SOAs,” Conference on Lasers and Electro-Optics/Quantum Electrons and Laser Science Conference and Photonic Applications Systems Technologies Technical Digest, (Optical Society of America, Washington, D.C., 2008), Paper CThAA1, (2008). [PubMed]

8.

A. Farbert, S. Langenbach, N. Stojanovic, C. Dorschky, T. Kupfer, C. Schulien, J. P. Elbers, H. Wernz, H. Griesser, and C. Glingener, “Performance of a 10.7 Gb/s Receiver with Digital Equaliser using Maximum Likelihood Sequence Estimation,” European Conference on Optical Communications (ECOC 2004), Stockholm, Sweden, Paper Th4.1.5, (2004).

9.

S. Chandrasekhar and A. H. Gnauck, “Performance of MLSE receiver in a dispersion-managed multispan experiment at 10.7 Gb/s under nonlinear transmission,” IEEE Photon. Technol. Lett. 18, 2448–2450 (2006). [CrossRef]

10.

J. D. Downie, J. Hurley, Y. Mauro, and S. Lobanov, “On the Use of MLSE with Non-Optimal Demodulation Filtering for Optical Duobinary Transmission,” Optical Fiber Communication Conference and Exhibition and The National Fiber Optic Engineers Conference on CD-ROM) (Optical Society of America, Washington, D.C., 2008), paper OTh05 (2008). [PubMed]

11.

J. D. Downie and J. Hurley, “Performance of an MLSE-EDC Receiver with SOA-induced Nonlinear Impairments,” IEEE Photon. Technol. Lett. , 20, 1326–1328 (2008). [CrossRef]

12.

A. Borghesani, N. Fensom, A. Scott, G. Crow, L. Johnston, J. King, L. Rivers, S. Cole, S. Perrin, D. Scrase, G. Bonfrate, A. Ellis, I. Lealman, G. Crouzel, L. How Kee Chun, A. Lupu, E. Mahe, and P. Maigne, “High saturation power (>16.5dBm) and low noise figure (<6dB) semiconductor optical amplifier for C-band operation,” Optical Fiber Communication Conference (OFC 2003) (Optical Society of America, Washington, D.C., 2003), paper ThO1.

OCIS Codes
(060.2330) Fiber optics and optical communications : Fiber optics communications
(060.2360) Fiber optics and optical communications : Fiber optics links and subsystems

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: August 26, 2008
Revised Manuscript: September 15, 2008
Manuscript Accepted: September 15, 2008
Published: September 19, 2008

Citation
John D. Downie, Jason Hurley, and Yihong Mauro, "10.7 Gb/s uncompensated transmission over a 470 km hybrid fiber link with in-line SOAs using MLSE and duobinary signals," Opt. Express 16, 15759-15764 (2008)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-20-15759


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. S. Kuwano, K. Yonenaga, and K. Iwashita, "10 Gbit/s Repeaterless Transmission Experiment of Optical Duobinary Modulated Signal," Electron. Lett. 31, 1359-1361 (1995). [CrossRef]
  2. D. Penninckx, H. Bissessur, P. Brindel, E. Gohin, and F. Bakhti, "Optical differential phase shift keying (DPSK) direct detection considered as a duobinary signal," European Conference on Optical Communications (ECOC 2001), Amsterdam, The Netherlands, Paper We.P.40, (2001).
  3. P. S. Cho and J. B. Khurgin, "Suppression of cross-gain modulation in SOA using RZ-DPSK modulation format," IEEE Photon. Technol. Lett. 15, 162-164 (2003). [CrossRef]
  4. X. Wei, Y. Su, X. Liu, J. Leuthold, and S. Chandrasekhar, "10-Gb/s RZ-DPSK Transmitter Using a Saturated SOA as a Power Booster and Limiting Amplifier," IEEE Photon. Technol. Lett. 16, 1582-1584 (2004). [CrossRef]
  5. A. D???Errico, V. Donzella, G. Contestabile, S. Betti, V. Carrozzo, F. Curti, M. Guglielmucci and E. Ciaramella, "Field-trial of SOA-based WDM-DPSK 8x10 Gbit/s system over 300km with conventional amplification span," Electron. Lett. 43, 404-405 (2007). [CrossRef]
  6. J. D. Downie, J. Hurley, M. Sauer, S. Raghavan, and S. Lobanov, "Uncompensated WDM transmission of 10.7 Gbit/s directly detected DPSK over 300 km standard single-mode fibre and through 6 SOAs," European Conference on Optical Communication (ECOC 2007), Berlin, Germany, Paper P076, (2007). [CrossRef]
  7. J. D. Downie, J. Hurley, and Y. Mauro, "Uncompensated 10.7 Gb/s Transmission over a 470 km Hybrid Fiber Link with In-Line SOAs," Conference on Lasers and Electro-Optics/Quantum Electrons and Laser Science Conference and Photonic Applications Systems Technologies Technical Digest, (Optical Society of America, Washington, D.C., 2008), Paper CThAA1, (2008). [PubMed]
  8. A. Farbert, S. Langenbach, N. Stojanovic, C. Dorschky, T. Kupfer, C. Schulien, J. P. Elbers, H. Wernz, H. Griesser, and C. Glingener, "Performance of a 10.7 Gb/s Receiver with Digital Equaliser using Maximum Likelihood Sequence Estimation," European Conference on Optical Communications (ECOC 2004), Stockholm, Sweden, Paper Th4.1.5, (2004).
  9. S. Chandrasekhar and A. H. Gnauck, "Performance of MLSE receiver in a dispersion-managed multispan experiment at 10.7 Gb/s under nonlinear transmission," IEEE Photon. Technol. Lett. 18, 2448-2450 (2006). [CrossRef]
  10. J. D. Downie, J. Hurley, Y. Mauro, and S. Lobanov, "On the Use of MLSE with Non-Optimal Demodulation Filtering for Optical Duobinary Transmission," Optical Fiber Communication Conference and Exhibition and The National Fiber Optic Engineers Conference on CD-ROM) (Optical Society of America, Washington, D.C., 2008), paper OTh05 (2008). [PubMed]
  11. J. D. Downie and J. Hurley, "Performance of an MLSE-EDC Receiver with SOA-induced Nonlinear Impairments," IEEE Photon. Technol. Lett.,  20, 1326-1328 (2008). [CrossRef]
  12. A. Borghesani, N. Fensom, A. Scott, G. Crow, L. Johnston, J. King, L. Rivers, S. Cole, S. Perrin, D. Scrase, G. Bonfrate, A. Ellis, I. Lealman, G. Crouzel, L. How Kee Chun, A. Lupu, E. Mahe, and P. Maigne, "High saturation power (>16.5dBm) and low noise figure (<6dB) semiconductor optical amplifier for C-band operation," Optical Fiber Communication Conference (OFC 2003) (Optical Society of America, Washington, D.C., 2003), paper ThO1.

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.


« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited