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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 20, Iss. 17 — Aug. 13, 2012
  • pp: 19088–19095
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Scrambled coherent superposition for enhanced optical fiber communication in the nonlinear transmission regime

Xiang Liu, S. Chandrasekhar, P. J. Winzer, A. R. Chraplyvy, R. W. Tkach, B. Zhu, T. F. Taunay, M. Fishteyn, and D. J. DiGiovanni  »View Author Affiliations


Optics Express, Vol. 20, Issue 17, pp. 19088-19095 (2012)
http://dx.doi.org/10.1364/OE.20.019088


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Abstract

Coherent superposition of light waves has long been used in various fields of science, and recent advances in digital coherent detection and space-division multiplexing have enabled the coherent superposition of information-carrying optical signals to achieve better communication fidelity on amplified-spontaneous-noise limited communication links. However, fiber nonlinearity introduces highly correlated distortions on identical signals and diminishes the benefit of coherent superposition in nonlinear transmission regime. Here we experimentally demonstrate that through coordinated scrambling of signal constellations at the transmitter, together with appropriate unscrambling at the receiver, the full benefit of coherent superposition is retained in the nonlinear transmission regime of a space-diversity fiber link based on an innovatively engineered multi-core fiber. This scrambled coherent superposition may provide the flexibility of trading communication capacity for performance in future optical fiber networks, and may open new possibilities in high-performance and secure optical communications.

© 2012 OSA

1. Introduction

Modern optical fiber communication has become the backbone of the internet era, thanks to breakthroughs such as low-loss optical fiber, the erbium-doped fiber amplifier, and wavelength-division multiplexing (WDM). As internet communication demands continue to increase exponentially, the once thought unlimited fiber bandwidth is facing a “capacity crunch”. To sustain the growth of communication capacity, spectrally efficient modulation formats such as polarization-division multiplexed (PDM) quadrature phase shift keying (QPSK) have recently been introduced to optical fiber communications [1

1. P. J. Winzer and R.-J. Essiambre, “Advanced optical modulation formats,” Proc. IEEE 94(5), 952–985 (2006). [CrossRef]

, 2

2. S. J. Savory, “Digital coherent optical receivers: algorithms and subsystems,” IEEE J. Sel. Top. Quantum Electron. 16(5), 1164–1179 (2010). [CrossRef]

]. The success of these phase-encoded signals is based on digital coherent detection which allows for the full recovery of the E-field of the optical signal. To further increase the fiber communication capacity, space-division multiplexing (SDM) is considered a promising new technology [3

3. A. R. Chraplyvy, “The coming capacity crunch,” in Proceedings of the2009European Conference on Optical Communication (Vienna, Austria), Plenary Talk.

6

6. G. Li and X. Liu, “Focus issue: Space multiplexed optical transmission,” Opt. Express 19(17), 16574–16575 (2011). [CrossRef] [PubMed]

]. Record per-fiber capacities of 112 Tb/s [7

7. B. Zhu, T. F. Taunay, M. Fishteyn, X. Liu, S. Chandrasekhar, M. F. Yan, J. M. Fini, E. M. Monberg, and F. V. Dimarcello, “112-Tb/s Space-division multiplexed DWDM transmission with 14-b/s/Hz aggregate spectral efficiency over a 76.8-km seven-core fiber,” Opt. Express 19(17), 16665–16671 (2011). [CrossRef] [PubMed]

] and 305 Tb/s [8

8. J. Sakaguchi, B. J. Puttnam, W. Klaus, Y. Awaji, N. Wada, A. Kanno, T. Kawanishi, K. Imamura, H. Inaba, K. Mukasa, R. Sugizaki, T. Kobayashi, and M. Watanabe, “19-core fiber transmission of 19x100x172-Gb/s SDM-WDM-PDM-QPSK signals at 305Tb/s,” in Proceedings of the 2012 Optical Fiber Communication Conference (Optical Society of America, Washington, DC, 2012), PDP5C.1.

] have been demonstrated using SDM in multi-core fiber (MCF). An aggregate spectral-efficiency-distance-product of 40,320 km⋅b/s/Hz [9

9. S. Chandrasekhar, A. H. Gnauck, X. Liu, P. J. Winzer, Y. Pan, E. C. Burrows, T. F. Taunay, B. Zhu, M. Fishteyn, M. F. Yan, J. M. Fini, E. M. Monberg, and F. V. Dimarcello, “WDM/SDM transmission of 10 x 128-Gb/s PDM-QPSK over 2688-km 7-core fiber with a per-fiber net aggregate spectral-efficiency distance product of 40,320 km·b/s/Hz,” Opt. Express 20(2), 706–711 (2012). [CrossRef] [PubMed]

] and an intrachannel spectral-efficiency of 60 b/s/Hz [10

10. X. Liu, S. Chandrasekhar, X. Chen, P. J. Winzer, Y. Pan, T. F. Taunay, B. Zhu, M. Fishteyn, M. F. Yan, J. M. Fini, E. M. Monberg, and F. V. Dimarcello, “1.12-Tb/s 32-QAM-OFDM superchannel with 8.6-b/s/Hz intrachannel spectral efficiency and space-division multiplexed transmission with 60-b/s/Hz aggregate spectral efficiency,” Opt. Express 19(26), B958–B964 (2011). [CrossRef] [PubMed]

] have also been experimentally demonstrated using a single MCF.

2. Principle of scrambled coherent superposition

3. Correlation and de-correlation of nonlinear distortions

To emulate the scrambling, seven signals EnTX(where n = 1,2…7) are delayed copies of an original signal, which is encoded with a pseudo random bit sequence (PRBS) of length 215-1 The delays are introduced at the transmitter through different optical delays, and known at the receiver through offline signal processing. Note that the scrambling functions can be short PRBSs. In this work, the scrambling functions are simply the delayed signal fields divided by the original signal field E0. These signals are space-diversified and transmitted over a 76.8-km seven-core fiber in a re-circulating loop configuration. In practice, the outputs of the MCF need to measured simultaneously. Due to the limited experimental resource in this proof-of-concept experiment, we use one coherent receiver to measure the outputs sequentially and store their E-fields. We then process the stored E-fields in an offline digital signal processor. The optical fields of all the received signals are first processed individually to compensate for the channel response and the frequency and phase offsets between the transmit laser and the receiver’s local oscillator laser. The recovered signal fields of all the SDM signals EnRXare then unscrambled, through division by their corresponding scrambling functions (or keys) Sn, before being synchronized, phase-aligned [12

12. X. Liu, S. Chandrasekhar, A. H. Gnauck, P. J. Winzer, A. R. Chraplyvy, B. Zhu, T. Taunay, and M. Fishteyn, “Performance improvement of space-division multiplexed 128-Gb/s PDM-QPSK signals by constructive superposition in a single-input-multiple-output configuration,” in Proceedings of the 2012 Optical Fiber Communication Conference (Optical Society of America, Washington, DC, 2012), OTu1D3.

], and coherently superimposed to obtain a reconstructed version of the original signal, ESCS, which is expected to have improved fidelity compared to that obtained with DCS, EDCS (Fig. 1(g)), as will be shown later. The number of superposed signals (m) can be varied as desired.

To illustrate the potential benefit of the constellation scrambling in coherent superposition, we assume that three signals are superimposed in a transmission system where the variance of the ASE noise induced linear distortions (σL2) equals that of the nonlinear distortions (σNL2) for each signal. In the case of DCS (Fig. 2(d)), the ASE-noise contribution to the final signal variance (σAll2) is reduced by a factor of three as the noises add incoherently and the signals add coherently, but the nonlinearity contribution to σAll2remains the same as both signals and nonlinear distortions are highly correlated. On the other hand, in the case of SCS (Fig. 2(e)), both the ASE-noise contribution and the nonlinearity contribution are reduced by a factor of three as the nonlinear distortions also add incoherently. The final signal variance after SCS is thus half of that after DCS, showing the benefit of the constellation scrambling in achieving the full potential of coherent superposition.

4. Theoretical performance gain

5. Experimental setup and results

6. Discussion and conclusion

References and links

1.

P. J. Winzer and R.-J. Essiambre, “Advanced optical modulation formats,” Proc. IEEE 94(5), 952–985 (2006). [CrossRef]

2.

S. J. Savory, “Digital coherent optical receivers: algorithms and subsystems,” IEEE J. Sel. Top. Quantum Electron. 16(5), 1164–1179 (2010). [CrossRef]

3.

A. R. Chraplyvy, “The coming capacity crunch,” in Proceedings of the2009European Conference on Optical Communication (Vienna, Austria), Plenary Talk.

4.

D. J. Richardson, “Applied physics. Filling the light pipe,” Science 330(6002), 327–328 (2010). [CrossRef] [PubMed]

5.

M. Nakazawa, “Giant leaps in optical communication technologies towards 2030 and beyond,” in Proceedings of the2010European Conference on Optical Communication (Turin, Italy), Plenary Talk.

6.

G. Li and X. Liu, “Focus issue: Space multiplexed optical transmission,” Opt. Express 19(17), 16574–16575 (2011). [CrossRef] [PubMed]

7.

B. Zhu, T. F. Taunay, M. Fishteyn, X. Liu, S. Chandrasekhar, M. F. Yan, J. M. Fini, E. M. Monberg, and F. V. Dimarcello, “112-Tb/s Space-division multiplexed DWDM transmission with 14-b/s/Hz aggregate spectral efficiency over a 76.8-km seven-core fiber,” Opt. Express 19(17), 16665–16671 (2011). [CrossRef] [PubMed]

8.

J. Sakaguchi, B. J. Puttnam, W. Klaus, Y. Awaji, N. Wada, A. Kanno, T. Kawanishi, K. Imamura, H. Inaba, K. Mukasa, R. Sugizaki, T. Kobayashi, and M. Watanabe, “19-core fiber transmission of 19x100x172-Gb/s SDM-WDM-PDM-QPSK signals at 305Tb/s,” in Proceedings of the 2012 Optical Fiber Communication Conference (Optical Society of America, Washington, DC, 2012), PDP5C.1.

9.

S. Chandrasekhar, A. H. Gnauck, X. Liu, P. J. Winzer, Y. Pan, E. C. Burrows, T. F. Taunay, B. Zhu, M. Fishteyn, M. F. Yan, J. M. Fini, E. M. Monberg, and F. V. Dimarcello, “WDM/SDM transmission of 10 x 128-Gb/s PDM-QPSK over 2688-km 7-core fiber with a per-fiber net aggregate spectral-efficiency distance product of 40,320 km·b/s/Hz,” Opt. Express 20(2), 706–711 (2012). [CrossRef] [PubMed]

10.

X. Liu, S. Chandrasekhar, X. Chen, P. J. Winzer, Y. Pan, T. F. Taunay, B. Zhu, M. Fishteyn, M. F. Yan, J. M. Fini, E. M. Monberg, and F. V. Dimarcello, “1.12-Tb/s 32-QAM-OFDM superchannel with 8.6-b/s/Hz intrachannel spectral efficiency and space-division multiplexed transmission with 60-b/s/Hz aggregate spectral efficiency,” Opt. Express 19(26), B958–B964 (2011). [CrossRef] [PubMed]

11.

T. Young, “Experimental demonstration of the general law of the interference of light,” Philos. Trans. R. Soc. Lond. 94, 1-16.(1804).

12.

X. Liu, S. Chandrasekhar, A. H. Gnauck, P. J. Winzer, A. R. Chraplyvy, B. Zhu, T. Taunay, and M. Fishteyn, “Performance improvement of space-division multiplexed 128-Gb/s PDM-QPSK signals by constructive superposition in a single-input-multiple-output configuration,” in Proceedings of the 2012 Optical Fiber Communication Conference (Optical Society of America, Washington, DC, 2012), OTu1D3.

13.

G. J. Foschini, “Layered space-time architecture for wireless communication in a fading environment when using multi-element antennas,” Bell Labs Tech. J. 1(2), 41–59 (1996). [CrossRef]

14.

H. R. Stuart, “Dispersive multiplexing in multimode optical fiber,” Science 289(5477), 281–283 (2000). [CrossRef] [PubMed]

15.

S. Naderi Shahi and S. Kumar, “Reduction of nonlinear impairments in fiber transmission system using fiber diversity,” in Proceedings of the 2011 OSA Summer Topical Meeting on Signal Processing in Photonic Communications (Toronto, Canada), SPWA3.

16.

C. E. Shannon, “A mathematical theory of communication,” Bell Syst. Tech. J. 27, 379–423 (1948).

17.

P. P. Mitra and J. B. Stark, “Nonlinear limits to the information capacity of optical fibre communications,” Nature 411(6841), 1027–1030 (2001). [CrossRef] [PubMed]

18.

R.-J. Essiambre, G. J. Foschini, G. Kramer, and P. J. Winzer, “Capacity limits of information transport in fiber-optic networks,” Phys. Rev. Lett. 101(16), 163901 (2008). [CrossRef] [PubMed]

19.

W. Shieh and X. Chen, “Information spectral efficiency and launch power density limits due to fiber nonlinearity for coherent optical OFDM system,” IEEE Photon. J. 3(2), 158–173 (2011). [CrossRef]

20.

R. W. Tkach, A. R. Chraplyvy, F. Forghieri, A. H. Gnauck, and R. M. Derosier, “Four-photon mixing and high speed WDM systems,” J. Lightwave Technol. 13(5), 841–849 (1995). [CrossRef]

21.

A. Mecozzi, C. B. Clausen, M. Shtaif, S.-G. Park, and A. H. Gnauck, “Cancellation of timing and amplitude jitter in symmetric links using highly dispersed pulses,” IEEE Photon. Technol. Lett. 13(5), 445–447 (2001). [CrossRef]

22.

G. P. Agrawal, Nonlinear Fiber Optics (Academic Press 2007).

23.

A. Carena, G. Bosco, G. V. Curri, P. Poggiolini, M. Tapia Taiba, and F. Forghieri, “Statistical characterization of PM-QPSK signals after propagation in uncompensated fiber links,” in Proceedings of the 2010 European Conference on Optical Communication (Turin, Italy), P4.07.

24.

D. M. Millar, S. Makovejs, V. Mikhailov, R. I. Killey, P. Bayvel, and S. J. Savory, “Experimental comparison of nonlinear compensation in long-haul PDM-QPSK transmission at 42.7 and 85.4 Gb/s,” in Proceedings of the 2009 European Conference on Optical Communication (Vienna, Austria), paper 9.4.4.

25.

X. Liu, S. Chandrasekhar, A. H. Gnauck, P. J. Winzer, S. Randel, S. Corteselli, B. Zhu, T. Taunay, and M. Fishteyn, “Digital coherent superposition for performance improvement of spatially multiplexed 676-Gb/s OFDM-16QAM superchannels,”in Proceedings of the 2012 European Conference on Optical Communication (Amsterdam, Netherlands), paper Tu.3.C.2 (2012).

26.

A. K. Ekert, “Quantum cryptography based on Bell’s theorem,” Phys. Rev. Lett. 67(6), 661–663 (1991). [CrossRef] [PubMed]

27.

H.-K. Lo and H. F. Chau, “Unconditional security of quantum key distribution over arbitrarily long distances,” Science 283(5410), 2050–2056 (1999). [CrossRef] [PubMed]

28.

H. Takesue, S. W. Nam, Q. Zhang, R. H. Hadfield, T. Honjo, K. Tamaki, and Y. Yamamoto, “Quantum key distribution over 40 dB channel loss using superconducting single photon detectors,” Nat. Photonics 1(6), 343–348 (2007). [CrossRef]

OCIS Codes
(060.1660) Fiber optics and optical communications : Coherent communications
(060.2330) Fiber optics and optical communications : Fiber optics communications
(060.4230) Fiber optics and optical communications : Multiplexing

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: June 18, 2012
Revised Manuscript: July 30, 2012
Manuscript Accepted: August 1, 2012
Published: August 3, 2012

Citation
Xiang Liu, S. Chandrasekhar, P. J. Winzer, A. R. Chraplyvy, R. W. Tkach, B. Zhu, T. F. Taunay, M. Fishteyn, and D. J. DiGiovanni, "Scrambled coherent superposition for enhanced optical fiber communication in the nonlinear transmission regime," Opt. Express 20, 19088-19095 (2012)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-17-19088


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References

  1. P. J. Winzer and R.-J. Essiambre, “Advanced optical modulation formats,” Proc. IEEE94(5), 952–985 (2006). [CrossRef]
  2. S. J. Savory, “Digital coherent optical receivers: algorithms and subsystems,” IEEE J. Sel. Top. Quantum Electron.16(5), 1164–1179 (2010). [CrossRef]
  3. A. R. Chraplyvy, “The coming capacity crunch,” in Proceedings of the2009European Conference on Optical Communication (Vienna, Austria), Plenary Talk.
  4. D. J. Richardson, “Applied physics. Filling the light pipe,” Science330(6002), 327–328 (2010). [CrossRef] [PubMed]
  5. M. Nakazawa, “Giant leaps in optical communication technologies towards 2030 and beyond,” in Proceedings of the2010European Conference on Optical Communication (Turin, Italy), Plenary Talk.
  6. G. Li and X. Liu, “Focus issue: Space multiplexed optical transmission,” Opt. Express19(17), 16574–16575 (2011). [CrossRef] [PubMed]
  7. B. Zhu, T. F. Taunay, M. Fishteyn, X. Liu, S. Chandrasekhar, M. F. Yan, J. M. Fini, E. M. Monberg, and F. V. Dimarcello, “112-Tb/s Space-division multiplexed DWDM transmission with 14-b/s/Hz aggregate spectral efficiency over a 76.8-km seven-core fiber,” Opt. Express19(17), 16665–16671 (2011). [CrossRef] [PubMed]
  8. J. Sakaguchi, B. J. Puttnam, W. Klaus, Y. Awaji, N. Wada, A. Kanno, T. Kawanishi, K. Imamura, H. Inaba, K. Mukasa, R. Sugizaki, T. Kobayashi, and M. Watanabe, “19-core fiber transmission of 19x100x172-Gb/s SDM-WDM-PDM-QPSK signals at 305Tb/s,” in Proceedings of the 2012 Optical Fiber Communication Conference (Optical Society of America, Washington, DC, 2012), PDP5C.1.
  9. S. Chandrasekhar, A. H. Gnauck, X. Liu, P. J. Winzer, Y. Pan, E. C. Burrows, T. F. Taunay, B. Zhu, M. Fishteyn, M. F. Yan, J. M. Fini, E. M. Monberg, and F. V. Dimarcello, “WDM/SDM transmission of 10 x 128-Gb/s PDM-QPSK over 2688-km 7-core fiber with a per-fiber net aggregate spectral-efficiency distance product of 40,320 km·b/s/Hz,” Opt. Express20(2), 706–711 (2012). [CrossRef] [PubMed]
  10. X. Liu, S. Chandrasekhar, X. Chen, P. J. Winzer, Y. Pan, T. F. Taunay, B. Zhu, M. Fishteyn, M. F. Yan, J. M. Fini, E. M. Monberg, and F. V. Dimarcello, “1.12-Tb/s 32-QAM-OFDM superchannel with 8.6-b/s/Hz intrachannel spectral efficiency and space-division multiplexed transmission with 60-b/s/Hz aggregate spectral efficiency,” Opt. Express19(26), B958–B964 (2011). [CrossRef] [PubMed]
  11. T. Young, “Experimental demonstration of the general law of the interference of light,” Philos. Trans. R. Soc. Lond.94, 1-16.(1804).
  12. X. Liu, S. Chandrasekhar, A. H. Gnauck, P. J. Winzer, A. R. Chraplyvy, B. Zhu, T. Taunay, and M. Fishteyn, “Performance improvement of space-division multiplexed 128-Gb/s PDM-QPSK signals by constructive superposition in a single-input-multiple-output configuration,” in Proceedings of the 2012 Optical Fiber Communication Conference (Optical Society of America, Washington, DC, 2012), OTu1D3.
  13. G. J. Foschini, “Layered space-time architecture for wireless communication in a fading environment when using multi-element antennas,” Bell Labs Tech. J.1(2), 41–59 (1996). [CrossRef]
  14. H. R. Stuart, “Dispersive multiplexing in multimode optical fiber,” Science289(5477), 281–283 (2000). [CrossRef] [PubMed]
  15. S. Naderi Shahi and S. Kumar, “Reduction of nonlinear impairments in fiber transmission system using fiber diversity,” in Proceedings of the 2011 OSA Summer Topical Meeting on Signal Processing in Photonic Communications (Toronto, Canada), SPWA3.
  16. C. E. Shannon, “A mathematical theory of communication,” Bell Syst. Tech. J.27, 379–423 (1948).
  17. P. P. Mitra and J. B. Stark, “Nonlinear limits to the information capacity of optical fibre communications,” Nature411(6841), 1027–1030 (2001). [CrossRef] [PubMed]
  18. R.-J. Essiambre, G. J. Foschini, G. Kramer, and P. J. Winzer, “Capacity limits of information transport in fiber-optic networks,” Phys. Rev. Lett.101(16), 163901 (2008). [CrossRef] [PubMed]
  19. W. Shieh and X. Chen, “Information spectral efficiency and launch power density limits due to fiber nonlinearity for coherent optical OFDM system,” IEEE Photon. J.3(2), 158–173 (2011). [CrossRef]
  20. R. W. Tkach, A. R. Chraplyvy, F. Forghieri, A. H. Gnauck, and R. M. Derosier, “Four-photon mixing and high speed WDM systems,” J. Lightwave Technol.13(5), 841–849 (1995). [CrossRef]
  21. A. Mecozzi, C. B. Clausen, M. Shtaif, S.-G. Park, and A. H. Gnauck, “Cancellation of timing and amplitude jitter in symmetric links using highly dispersed pulses,” IEEE Photon. Technol. Lett.13(5), 445–447 (2001). [CrossRef]
  22. G. P. Agrawal, Nonlinear Fiber Optics (Academic Press 2007).
  23. A. Carena, G. Bosco, G. V. Curri, P. Poggiolini, M. Tapia Taiba, and F. Forghieri, “Statistical characterization of PM-QPSK signals after propagation in uncompensated fiber links,” in Proceedings of the 2010 European Conference on Optical Communication (Turin, Italy), P4.07.
  24. D. M. Millar, S. Makovejs, V. Mikhailov, R. I. Killey, P. Bayvel, and S. J. Savory, “Experimental comparison of nonlinear compensation in long-haul PDM-QPSK transmission at 42.7 and 85.4 Gb/s,” in Proceedings of the 2009 European Conference on Optical Communication (Vienna, Austria), paper 9.4.4.
  25. X. Liu, S. Chandrasekhar, A. H. Gnauck, P. J. Winzer, S. Randel, S. Corteselli, B. Zhu, T. Taunay, and M. Fishteyn, “Digital coherent superposition for performance improvement of spatially multiplexed 676-Gb/s OFDM-16QAM superchannels,”in Proceedings of the 2012 European Conference on Optical Communication (Amsterdam, Netherlands), paper Tu.3.C.2 (2012).
  26. A. K. Ekert, “Quantum cryptography based on Bell’s theorem,” Phys. Rev. Lett.67(6), 661–663 (1991). [CrossRef] [PubMed]
  27. H.-K. Lo and H. F. Chau, “Unconditional security of quantum key distribution over arbitrarily long distances,” Science283(5410), 2050–2056 (1999). [CrossRef] [PubMed]
  28. H. Takesue, S. W. Nam, Q. Zhang, R. H. Hadfield, T. Honjo, K. Tamaki, and Y. Yamamoto, “Quantum key distribution over 40 dB channel loss using superconducting single photon detectors,” Nat. Photonics1(6), 343–348 (2007). [CrossRef]

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