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Optics Express

Optics Express

  • Editor: Michael Duncan
  • Vol. 14, Iss. 24 — Nov. 27, 2006
  • pp: 11520–11527
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Experimental measurements of uncompensated reach increase from MLSE-EDC with regard to measurement BER and modulation format

John D. Downie, Michael Sauer, and Jason Hurley  »View Author Affiliations


Optics Express, Vol. 14, Issue 24, pp. 11520-11527 (2006)
http://dx.doi.org/10.1364/OE.14.011520


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Abstract

Comprehensive experimental measurement data are presented comparing the performance of an optical receiver with MLSE-EDC technology against a standard receiver for signals with uncompensated chromatic dispersion. Signals with the NRZ and duobinary modulation formats are investigated. We find that the MLSE-EDC technology provides greater uncompensated reach advantage for both formats as the allowable measured BER is increased, demonstrating the EDC technology has greatest effect and application in conjunction with strong forward error correction. We also measure signal quality vs. dispersion with constant OSNR and draw similar conclusions along with further insights into the application space of the EDC technology for both modulation formats.

© 2006 Optical Society of America

1. Introduction

2. Experimental configuration

Fig. 1. Experimental set-up for measurement of MLSE-EDC effectiveness against signal distortion caused by chromatic dispersion.

Two different commercially available photoreceivers were used in the system experiments for comparison. One receiver (Rx) was a standard photoreceiver with a PIN photodetector, trans-impedance amplifier, and associated clock and data recovery circuitry. The second Rx was from the same manufacturer, but had MLSE-EDC circuitry in the back-end electronics. The MLSE Rx 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. Given the general equivalence of the PIN photodetectors used, the two receivers allowed reasonably fair evaluation of the MLSE-EDC technology implemented in the second receiver.

3. Experimental results

In the first set of experiments, the measurement quantity was the required OSNR value of the signal at the receiver in order to achieve a specific BER value. In general, the BER values tested were 10-9, 10-6, 10-4, and 10-3. This was done for various transmission distances over standard single-mode fiber, from 0 km out to the maximum distance measurable. The first modulation format studied was NRZ, and the results comparing the performance of the standard receiver to the MLSE-EDC receiver are shown in Fig. 2. The results clearly show a back-to-back penalty suffered by the MLSE-EDC Rx that is strongly dependent on the measurement BER. For example, for BER=10-9, the back-to-back penalty is over 4 dB. This penalty monotonically decreases with increasing measurement BER, and is less than 1 dB for BER=10-3. We suspect this penalty is likely due to the limited resolution of the A/D converter, and is not necessarily fundamental to the MLSE algorithm. This reasoning may be consistent with the decreasing nature of the penalty as the measurement BER increases. Another observation from the data in Fig. 2 is that the reach advantage offered by the MLSE-EDC is also a function of the measurement BER. In fact, the reach advantage increases with increasing measurement BER, such that the maximum advantage of the MLSE-EDC receiver over the standard receiver occurs for BER=10-3, both in terms of percentage and actual distance advantage.

Fig. 2. Experimental data for NRZ modulation format signals and required OSNR to achieve BER values of a) 10-9, b) 10-6, c) 10-4, and d) 10-3 as a function of uncompensated transmission distance over standard single-mode fiber.

Fig. 3. Experimental data for duobinary modulation format signals and required OSNR to achieve BER values of a) 10-9, b) 10-6, c) 10-4, and d) 10-3 as a function of uncompensated transmission distance over standard single-mode fiber.

The data in Figs. 2 and 3 can be summarized in terms of the reach increase afforded by the MLSE-EDC receiver in comparison to the standard receiver as shown in Fig. 4. In this figure, we present the reach increase obtained for both NRZ and duobinary modulation formats as a function of the measurement BER value. The reach increase is defined at an OSNR penalty level of 5 dB in comparison to the back-to-back value of the standard receiver. The advantage is expressed in terms of both percentage increase and absolute distance increase. As discussed above, both formats experience a larger advantage from the MLSE-EDC receiver for higher measurement BER values.

Fig. 4. Summary of MLSE-EDC receiver reach advantage data as a function of measurement BER expressed in terms of a) percentage, and b) absolute distance.

Fig. 5. Comparison of NRZ and duobinary performance in terms of required OSNR for a BER value of 10-3 for a) the standard receiver, and b) the MLSE-EDC receiver.

Finally, it is interesting and instructive to compare the performance of the standard and MLSE-EDC receivers for these modulation formats in a different way. In another set of experiments, we kept the OSNR of the signals constant, and measured the signal BER as a function of uncompensated transmission distance. The signal Q value was then calculated from the BER data. The OSNR used for all measurements was the maximum possible OSNR achievable at the longest distance tested for a given modulation format. This sort of comparison may represent the expected performance of real systems somewhat more closely and can suggest clearly the range of transmission distances for which the MLSE-EDC technology is essential and necessary.

Fig. 6. Comparison of standard and MLSE-EDC receivers for an NRZ signal as a function of transmission distance with constant OSNR.

Similar experiments were conducted with the duobinary signal and the observed results are shown in Fig. 7. The signal OSNR value for all measurements was about 26 dB. The results are significantly different from the NRZ data and show that the standard receiver provides better performance for all distances out to approximately 240 km. The signal was error-free with the standard receiver for distances between 40 km and 225 km, while the MLSE-EDC receiver provided nominally flat signal quality for all distances out to ~250 km with Q values over that range of 14-15 dB. It was only for transmission beyond 240 km that the MLSE-EDC receiver provided better performance but it did give more than 2 dB improvement in the Q value at 270 km.

Fig. 7. Comparison of standard and MLSE-EDC receivers for a duobinary signal as a function of transmission distance with constant OSNR.

Fig. 8. Comparison of duobinary format with standard receiver against NRZ format with MLSE-EDC receiver as a function of transmission distance with constant OSNR.

4. Summary and conclusion

References and links

1.

G. S. Kanter, A. K. Samal, and A. Gandhi, “Electronic dispersion compensation for extended reach,” Optical Fiber Communication Conference (OFC 2004) (Optical Society of America, Washington, D.C., 2004), paper TuG1.

2.

T. Nielsen and S. Chandrasekhar, “OFC 2004 Workshop on Optical and Electronic Mitigation of Impairments,” J. Lightwave Technol. 23, 131–142 (2005). [CrossRef]

3.

H. Griesser, J.-P. Elbers, C. Fuerst, H. Wernz, and C. Glingener, “Increasing the dispersion tolerance of 10 Gb/s Duobinary Modulation by Electrical Distortion Equalisation,” European Conference on Optical Communications (ECOC 2004), Stockholm, Sweden, paper We4.P.106, (2004).

4.

M. D. Feuer, S,-Y. Huang, S. L. Woodward, O. Coskun, and M. Boroditsky, “Electronic dispersion compensation for a 10-Gb/s link using a directly modulated laser,” IEEE Photon. Technol. Lett. 15, 1788–1790 (2003). [CrossRef]

5.

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).

6.

H. Haunstein and R. Urbansky, “Application of Electronic Equalization and Error Correction in Lightwave Systems,” European Conference on Optical Communications (ECOC 2004), Stockholm, Sweden, paper Th.1.5.1, (2004).

7.

J.-P. Elbers, H. Wernz, H. Griesser, C. Glingener, A. Faerbert, S. Langenbach, N. Stojanovic, C. Dorschky, T. Kupfer, and C. Schulien, “Measurement of the dispersion tolerance of Optical Duobinary with an MLSE-Receiver at 10.7 Gb/s,” Optical Fiber Communication Conference and Exhibition and The National Fiber Optic Engineers Conference on CD-ROM) (Optical Society of America, Washington, D.C., 2005), paper OThJ4. [PubMed]

8.

C. Xia and W. Rosenkranz, “Performance enhancement for Duobinary Modulation through Nonlinear Electrical Equalization,” European Conference on Optical Communications (ECOC 2005), Glasgow, Scotland, paper Tu4.2.31, (2005).

9.

A. Faerbert, “Application of Digital Equalization in Optical Transmission Systems,” Optical Fiber Communication Conference and Exhibition and The National Fiber Optic Engineers Conference on CDROM) (Optical Society of America, Washington, D.C., 2006), paper OTuE5. [CrossRef]

10.

V. Curri, R. Gaudino, A. Napoli, and A. Nespola, “Advantages of using the Electronic Equalization together with innovative modulation formats in dispersion-limited systems,” 2004 IEEE LEOS Annual Meeting Conference Proceedings, paper ThB1, (2004).

11.

A. Price and N. Le Mercier, “Reduced bandwidth optical digital intensity modulation with improved chromatic dispersion tolerance,” Electron. Lett. 31, 58–59 (1995). [CrossRef]

12.

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]

13.

D. Penninckx, M. Chbat, L. Pierre, and J.-P. Thiery, “The Phase-Shaped Binary Transmission (PSBT): A new technique to transmit far beyond the chromatic dispersion limit,” IEEE Photon. Technol. Lett. 9, 259–261 (1997). [CrossRef]

OCIS Codes
(060.2360) Fiber optics and optical communications : Fiber optics links and subsystems
(060.4080) Fiber optics and optical communications : Modulation

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: September 13, 2006
Revised Manuscript: November 9, 2006
Manuscript Accepted: November 14, 2006
Published: November 27, 2006

Citation
John D. Downie, Michael Sauer, and Jason Hurley, "Experimental measurements of uncompensated reach increase from MLSE-EDC with regard to measurement BER and modulation format," Opt. Express 14, 11520-11527 (2006)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-14-24-11520


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References

  1. G. S. Kanter, A. K. Samal, and A. Gandhi, "Electronic dispersion compensation for extended reach," Optical Fiber Communication Conference (OFC 2004) (Optical Society of America, Washington, D.C., 2004), paper TuG1.
  2. T. Nielsen and S. Chandrasekhar, "OFC 2004 Workshop on Optical and Electronic Mitigation of Impairments," J. Lightwave Technol. 23, 131-142 (2005). [CrossRef]
  3. H. Griesser, J.-P. Elbers, C. Fuerst, H. Wernz, and C. Glingener, "Increasing the dispersion tolerance of 10 Gb/s Duobinary Modulation by Electrical Distortion Equalisation," European Conference on Optical Communications (ECOC 2004), Stockholm, Sweden, paper We4.P.106, (2004).
  4. M. D. Feuer, S,-Y. Huang, S. L. Woodward, O. Coskun, and M. Boroditsky, "Electronic dispersion compensation for a 10-Gb/s link using a directly modulated laser," IEEE Photon. Technol. Lett. 15, 1788-1790 (2003). [CrossRef]
  5. 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).
  6. H. Haunstein, and R. Urbansky, "Application of Electronic Equalization and Error Correction in Lightwave Systems," European Conference on Optical Communications (ECOC 2004), Stockholm, Sweden, paper Th.1.5.1, (2004).
  7. J.-P. Elbers, H. Wernz, H. Griesser, C. Glingener, A. Faerbert, S. Langenbach, N. Stojanovic, C. Dorschky, T. Kupfer, and C. Schulien, "Measurement of the dispersion tolerance of Optical Duobinary with an MLSE-Receiver at 10.7 Gb/s," Optical Fiber Communication Conference and Exhibition and The National Fiber Optic Engineers Conference on CD-ROM) (Optical Society of America, Washington, D.C., 2005), paper OThJ4. [PubMed]
  8. C. Xia, and W. Rosenkranz, "Performance enhancement for Duobinary Modulation through Nonlinear Electrical Equalization," European Conference on Optical Communications (ECOC 2005), Glasgow, Scotland, paper Tu4.2.31, (2005).
  9. A. Faerbert, "Application of Digital Equalization in Optical Transmission Systems," Optical Fiber Communication Conference and Exhibition and The National Fiber Optic Engineers Conference on CD-ROM) (Optical Society of America, Washington, D.C., 2006), paper OTuE5. [CrossRef]
  10. V. Curri, R. Gaudino, A. Napoli, and A. Nespola, "Advantages of using the Electronic Equalization together with innovative modulation formats in dispersion-limited systems," 2004 IEEE LEOS Annual Meeting Conference Proceedings, paper ThB1, (2004).
  11. A. Price and N. Le Mercier, "Reduced bandwidth optical digital intensity modulation with improved chromatic dispersion tolerance," Electron. Lett. 31, 58-59 (1995). [CrossRef]
  12. 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]
  13. D. Penninckx, M. Chbat, L. Pierre, and J.-P. Thiery, "The Phase-Shaped Binary Transmission (PSBT): A new technique to transmit far beyond the chromatic dispersion limit," IEEE Photon. Technol. Lett. 9, 259-261 (1997). [CrossRef]

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