Abstract

For asynchronous sampled systems such as Polarization Division Multiplexed Quadrature Phase Shift Keying, (PDM-QPSK), phase and frequency of the sampling clock is typically not synchronized to the data symbols. Therefore, timing adjustment, so called clock recovery and interpolation, must be performed in digital domain prior to signal demodulation in order to avoid cycle slips. For the first time, the impact of first order PMD, (DGD), is experimentally investigated and quantified for 112 Gb/s PDM-QPSK signal. We experimentally show that the combined effect of polarization mixing and first order PMD can significantly affect the performance of the timing error detector gain, even for moderate values leading to system outage. We propose and experimentally demonstrate a novel digital adaptive timing error detector is robust to polarization mixing and DGD. The proposed timing error detector algorithm combines the Gardner timing error detector algorithm with an adaptive structure based on gradient method.

© 2011 OSA

Full Article  |  PDF Article

References

  • View by:
  • |
  • |
  • |

  1. M. Kuschnerov, F. N. Hauske, K. Piyawanno, B. Spinnler, M. S. Alfiad, A. Napoli, and B. Lankl, “DSP for coherent single-carrier receivers,” J. Lightwave Technol. 27(16), 3614–3622 (2009).
    [CrossRef]
  2. C. R. S. Fludger, T. Duthel, D. van den Borne, C. Schulien, E.-D. Schmidt, T. Wuth, J. Geyer, E. De Man, Khoe Giok-Djan, and H. de Waardt, “Coherent Equalization and POLMUX-RZ-DQPSK for Robust 100-GE Transmission,” J. Lightwave Technol. 26(1), 64–72 (2008).
    [CrossRef]
  3. S. J. Savory, “Digital filters for coherent optical receivers,” Opt. Express 16(2), 804–817 (2008).
    [CrossRef] [PubMed]
  4. G. Charlet, J. Renaudier, H. Mardoyan, P. Tran, O. B. Pardo, F. Verluise, M. Achouche, A. Boutin, F. Blache, J.-Y. Dupuy, and S. Bigo, “Transmission of 16.4-bit/s Capacity Over 2550 km Using PDM QPSK Modulation Format and Coherent Receiver,” J. Lightwave Technol. 27(3), 153–157 (2009).
    [CrossRef]
  5. F. M. Gardner, “Interpolation in digital modems. I. Fundamentals,” IEEE Trans. Commun. 41(3), 501–507 (1993).
    [CrossRef]
  6. L. Erup, F. M. Gardner, and R. A. Harris, “Interpolation in Digital Modems – Part II: Implementation and Performance,” IEEE Trans. Commun. 41(6), 998–1008 (1993).
    [CrossRef]
  7. H. Meyr, M. Moeneclaey, and S. A. Fechtel, Digital communication receivers (John Wiley & Sons, 1998)
  8. M. Floyd, Gardner, Phaselock techniques (John Wiley & Sons, 1998)
  9. F. M. Gardner, “A BPSK/QPSK timing-error detector for sampled receivers,” IEEE Trans. Commun. 34(5), 423–429 (1986).
    [CrossRef]
  10. D. Zibar, A. Binaciotto, Z. Wang, A. Napoli, and B. Spinnler, “Analysis and Dimensioning of Fully Digital Clock Recovery for 112 Gb/s Coherent Polmux QPSK Systems” In Proceedings of Conference on Optical Communication (ECOC) 2009, Vienna, Austria, paper 7.3.4, 2009.
  11. F. N. Hauske, N. Stojanovic, C. Xie, and M. Chen, “Impact of optical channel distortions to digital timing recovery in digital coherent transmission systems,” in Proceedings of International Conference on Transparent Optical Networks (ICTON), We.D1.4, 2010.
  12. C. Hebebrand, A. Napoli, A. Bianciotto, S. Calabro, B. Spinnler, and W. Rosenkranz, “Digital clock recovery with adaptive loop gain to overcome channel impairments in 112 Gbit/s CP-QPSK Receivers,” in Proceedings of European Conference on Optical Communication, ECOC, poster P3.08 (2010)
  13. H. Sun and K.-T. Wu, “A novel dispersion and PMD tolerant clock phase detector for coherent transmission systems,” in Proceedings of Optical Fibre Communication Conference (OFC), OMJ4, 2011.

2009 (2)

2008 (2)

1993 (2)

F. M. Gardner, “Interpolation in digital modems. I. Fundamentals,” IEEE Trans. Commun. 41(3), 501–507 (1993).
[CrossRef]

L. Erup, F. M. Gardner, and R. A. Harris, “Interpolation in Digital Modems – Part II: Implementation and Performance,” IEEE Trans. Commun. 41(6), 998–1008 (1993).
[CrossRef]

1986 (1)

F. M. Gardner, “A BPSK/QPSK timing-error detector for sampled receivers,” IEEE Trans. Commun. 34(5), 423–429 (1986).
[CrossRef]

Achouche, M.

Alfiad, M. S.

Bigo, S.

Blache, F.

Boutin, A.

Charlet, G.

De Man, E.

de Waardt, H.

Dupuy, J.-Y.

Duthel, T.

Erup, L.

L. Erup, F. M. Gardner, and R. A. Harris, “Interpolation in Digital Modems – Part II: Implementation and Performance,” IEEE Trans. Commun. 41(6), 998–1008 (1993).
[CrossRef]

Fludger, C. R. S.

Gardner, F. M.

L. Erup, F. M. Gardner, and R. A. Harris, “Interpolation in Digital Modems – Part II: Implementation and Performance,” IEEE Trans. Commun. 41(6), 998–1008 (1993).
[CrossRef]

F. M. Gardner, “Interpolation in digital modems. I. Fundamentals,” IEEE Trans. Commun. 41(3), 501–507 (1993).
[CrossRef]

F. M. Gardner, “A BPSK/QPSK timing-error detector for sampled receivers,” IEEE Trans. Commun. 34(5), 423–429 (1986).
[CrossRef]

Geyer, J.

Harris, R. A.

L. Erup, F. M. Gardner, and R. A. Harris, “Interpolation in Digital Modems – Part II: Implementation and Performance,” IEEE Trans. Commun. 41(6), 998–1008 (1993).
[CrossRef]

Hauske, F. N.

Khoe Giok-Djan,

Kuschnerov, M.

Lankl, B.

Mardoyan, H.

Napoli, A.

Pardo, O. B.

Piyawanno, K.

Renaudier, J.

Savory, S. J.

Schmidt, E.-D.

Schulien, C.

Spinnler, B.

Tran, P.

van den Borne, D.

Verluise, F.

Wuth, T.

IEEE Trans. Commun. (3)

F. M. Gardner, “Interpolation in digital modems. I. Fundamentals,” IEEE Trans. Commun. 41(3), 501–507 (1993).
[CrossRef]

L. Erup, F. M. Gardner, and R. A. Harris, “Interpolation in Digital Modems – Part II: Implementation and Performance,” IEEE Trans. Commun. 41(6), 998–1008 (1993).
[CrossRef]

F. M. Gardner, “A BPSK/QPSK timing-error detector for sampled receivers,” IEEE Trans. Commun. 34(5), 423–429 (1986).
[CrossRef]

J. Lightwave Technol. (3)

Opt. Express (1)

Other (6)

D. Zibar, A. Binaciotto, Z. Wang, A. Napoli, and B. Spinnler, “Analysis and Dimensioning of Fully Digital Clock Recovery for 112 Gb/s Coherent Polmux QPSK Systems” In Proceedings of Conference on Optical Communication (ECOC) 2009, Vienna, Austria, paper 7.3.4, 2009.

F. N. Hauske, N. Stojanovic, C. Xie, and M. Chen, “Impact of optical channel distortions to digital timing recovery in digital coherent transmission systems,” in Proceedings of International Conference on Transparent Optical Networks (ICTON), We.D1.4, 2010.

C. Hebebrand, A. Napoli, A. Bianciotto, S. Calabro, B. Spinnler, and W. Rosenkranz, “Digital clock recovery with adaptive loop gain to overcome channel impairments in 112 Gbit/s CP-QPSK Receivers,” in Proceedings of European Conference on Optical Communication, ECOC, poster P3.08 (2010)

H. Sun and K.-T. Wu, “A novel dispersion and PMD tolerant clock phase detector for coherent transmission systems,” in Proceedings of Optical Fibre Communication Conference (OFC), OMJ4, 2011.

H. Meyr, M. Moeneclaey, and S. A. Fechtel, Digital communication receivers (John Wiley & Sons, 1998)

M. Floyd, Gardner, Phaselock techniques (John Wiley & Sons, 1998)

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (8)

Fig. 1
Fig. 1

General outline of the experimental set-up for 112 Gb/s PDM-QPSK system.

Fig. 2
Fig. 2

(a) Clock recovery and the interpolation module. (b) Clock recovery and interpolation module employing an adaptive timing error detector.

Fig. 3
Fig. 3

Normalized timing error detector gain, Kd, as a function of polarization rotation angle for the DGD of 0.5Tsym.

Fig. 4(a)
Fig. 4(a)

Histogram depicting the number of failures as the DGD is varied from 0 to 107% of Tsym. 3.2 Adaptive timing error detector

Fig. 4(b)
Fig. 4(b)

An adaptive timing error detector scheme. W(z) is a digital loop filter.

Fig. 5
Fig. 5

(a) Normalized Gardner timing error detector gain Kd as a function of α for the open loop configuration of. (b) Simulation data: Normalized Gardner timing error detector gain, Kd, as a function of number of iterations for α ranging from 22.5° to 90° after applying the adaptive structure in Fig. 4.

Fig. 6
Fig. 6

Normalized Gardner timing error detector gain Kd as a function of number of iterations for the selected values of the length of the sequence Nseq.

Fig. 7
Fig. 7

Experimental data: Normalized Gardner timing error detector gain, Kd, as a function of number of iterations for polarization rotation angle ranging from 0 to 90° after applying the adaptive structure in Fig. 4. The DGD is 50% of Tsym

Equations (17)

Equations on this page are rendered with MathJax. Learn more.

y(n)= V xi (n2){ V xi (n3) V xi (n1) }+ V xq (n2){ V xi (n3) V xi (n1) }
K d = 1 N seq n= N seq /2 N seq /2 y(n)
V xi (n)=a(n)cos(α)b(n)sin(α)
V yi (n)=a(n)sin(α)+b(n)cos(α)
V xq (n)=c(n)cos(α)d(n)sin(α)
V yq (n)=c(n)sin(α)+d(n)cos(α)
a(n)= x h,i (n)cos(φ(n)) x h,q (n)sin(φ(n))
b(n)= x v,i (nΔ T DGD )cos(φ(n)) x v,q (nΔ T DGD )sin(φ(n))
c(n)= x h,i (n)sin(φ(n))+ x h,q (n)cos(φ(n))
d(n)= x v,i (nΔ T DGD )sin(φ(n))+ x v,q (nΔ T DGD )cos(φ(n))
V xi rec (n)= V xi (n)cos(α)+ V yi (n)sin(α)=a(n)
V xq rec (n)= V xq (n)cos(α)+ V yq (n)sin(α)=c(n)
V yi rec (n)= V xi (n)sin(α)+ V yi (n)cos(α)=b(n)
V yq rec (n)= V xq (n)sin(α)+ V yq (n)cos(α)=d(n)
J= argmax α{ 0;π } { K d (α) }
α est (n+1)= α est (n) 1 2 μ d K d dα
d K d d α est ={ 1 N seq n=- N seq /2 N seq /2 a(n-2){ a(n-3)-a(n-1) }-b(n-2){ b(n-3)-b(n-1) } } ×sin(2(α- α est ))

Metrics