Abstract

We experimentally demonstrate the impact of equalization-enhanced phase noise (EEPN) on the performance of 56 Gbaud dual-polarization (DP) QPSK long haul transmission systems. Although EEPN adds additional noise to the received symbols, we show that this reduces the phase variance introduced by the LO laser, and therefore should be considered when designing the carrier phase recovery (CPR) algorithms and estimating system performance. Further, we experimentally demonstrate the performance degradation caused by EEPN when a LO laser with a large linewidth is used at the receiver. When using a 2.6 MHz linewidth distributed feedback (DFB) laser instead of a ~100 kHz linewidth external-cavity laser (ECL) as a LO, the transmission distance is reduced from 4160 km to 2640 km due to EEPN. We also confirm the reduction of the phase variance of the received symbols for longer transmission distances showing its impact on the CPR algorithm optimization when a DFB laser is used at the receiver. Finally, the relationship between the EEPN-induced penalty versus the signal baud rate and the LO laser linewidth is experimentally evaluated, and numerically validated by simulations.

© 2012 OSA

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References

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    [CrossRef]

2011

2010

2009

2008

Al Amin, A.

Chen, X.

Colavolpe, G.

Foggi, T.

Forestieri, E.

Ho, K.-P.

Hoffmann, S.

Lau, A. P. T.

Noe, R.

Pfau, T.

Secondini, M.

Shen, T. S. R.

Shieh, W.

Taylor, M. G.

J. Lightwave Technol.

Opt. Express

Other

S. Oda, C. Ohshima, T. Tanaka, T. Tanimura, H. Nakashima, N. Koizumi, T. Hoshida, H. Zhang, Z. Tao, and J. C. Rasmussen, “Interplay between local oscillator phase noise and electrical chromatic dispersion compensation in digital coherent transmission system,” in Proc. ECOC'10, Paper. Mo.1.C.2.

M. Salsi, O. Bertran-Pardo, J. Renaudier, W. Idler, H. Mardoyan, P. Tran, G. Charlet, and S. Bigo, “WDM 200Gb/s single-carrier PDM-QPSK transmission over 12,000km,” in Proc. ECOC'11, Paper. Th.13.C.5.

P. J. Winzer, A. H. Gnauck, G. Raybon, M. Schnecker, and P. J. Pupalaikis, “56-Gbaud PDM-QPSK: coherent detection and 2,500-km transmission,” in Proc. ECOC'09, Paper. PD2.7.

C. Xie, “Local oscillator phase noise induced penalties in optical coherent detection systems using electronic chromatic dispersion compensation,” in Proc. OFC'09, Paper. OMT4.

Q. Zhuge, B. Châtelain, C. Chen, and D. V. Plant, “Mitigation of equalization-enhanced phase noise using reduced-guard-interval CO-OFDM,” in Proc. ECOC'11 Paper. Th.11.B.5.

Q. Zhuge, M. E. Pasandi, X. Xu, B. Châtelain, Z. Pan, M. Osman, and D. V. Plant, “Linewidth-tolerant low complexity pilot-aided carrier phase recovery for M-QAM using superscalar parallelization,” in Proc. OFC'12, Paper. OTu2G.2.

K. Kikuchi and K. Igarashi, “Characterization of semiconductor-laser phase noise with digital coherent receivers,” in Proc. OFC'11, Paper. OML3.

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Figures (7)

Fig. 1
Fig. 1

The origin of EEPN.

Fig. 2
Fig. 2

The effects of the EEPN on 56 Gbaud QPSK signals in simulation. (a) The phase of the received symbols before CPR. The constellations after CPR for (b) back-to-back case and (c) 4160 km transmission distance.

Fig. 3
Fig. 3

Experimental setup. Inset: optical eye diagram of the 56 Gbaud QPSK signal. PBC/PBS: polarization beam combiner/splitter. PC: polarization controller. SW: switch.

Fig. 4
Fig. 4

Measured back-to-back BER vs. the OSNR (measured over a 0.1 nm resolution).

Fig. 5
Fig. 5

Measured Q-factor versus transmission distance.

Fig. 6
Fig. 6

(a) Estimated linewidth versus transmission distance and (b) Q-factor versus CPR filter length at 4160 km distance with different lasers at the two ends.

Fig. 7
Fig. 7

Q-factor penalty of an ECL/DFB system (with respect to ECL/ECL) at 4160 km distance versus: (a) the baud rate and (b) the LO laser linewidth.

Equations (2)

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r(t)={ [ s(t) e j ϕ t (t) ] h CD (t) e j ϕ r (t) } h E (t) ,
r k = c k e jϕ[k] + n EEPN ,

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