Abstract

We propose a decision-aided algorithm to compensate the sampling frequency offset (SFO) between the transmitter and receiver for reduced-guard-interval (RGI) coherent optical (CO) OFDM systems. In this paper, we first derive the cyclic prefix (CP) requirement for preventing OFDM symbols from SFO induced inter-symbol interference (ISI). Then we propose a new decision-aided SFO compensation (DA-SFOC) algorithm, which shows a high SFO tolerance and reduces the CP requirement. The performance of DA-SFOC is numerically investigated for various situations. Finally, the proposed algorithm is verified in a single channel 28 Gbaud polarization division multiplexing (PDM) RGI CO-OFDM experiment with QPSK, 8 QAM and 16 QAM modulation formats, respectively. Both numerical and experimental results show that the proposed DA-SFOC method is highly robust against the standard SFO in optical fiber transmission.

© 2014 Optical Society of America

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References

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    [Crossref]
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    [Crossref]
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    [Crossref]
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    [Crossref]
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    [Crossref]
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    [Crossref]
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    [Crossref] [PubMed]
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    [Crossref]
  14. W. Wang, Q. Zhuge, Y. Gao, M. Qiu, M. Morsy-Osman, M. Chagnon, X. Xu, and D. V. Plant, “Low overhead and nonlinear-tolerant adaptive zero-guard-interval CO-OFDM,” Opt. Express 22(15), 17810–17822 (2014).
    [Crossref] [PubMed]
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    [Crossref]

2014 (1)

2013 (1)

2011 (4)

2008 (3)

Buchali, F.

Chagnon, M.

Chandrasekhar, S.

Du, L. B.

A. J. Lowery and L. B. Du, “Optical orthogonal division multiplexing for long haul optical communications: A review of the last five years,” Opt. Fiber Technol. 17(5), 421–438 (2011).
[Crossref]

Gao, Y.

Gnauck, A. H.

Jansen, S. L.

Liu, X.

Lowery, A. J.

A. J. Lowery and L. B. Du, “Optical orthogonal division multiplexing for long haul optical communications: A review of the last five years,” Opt. Fiber Technol. 17(5), 421–438 (2011).
[Crossref]

Ma, Y.

Morita, I.

Morsy-Osman, M.

Peckham, D. W.

Plant, D. V.

Qiu, K.

Qiu, M.

Schenk, T. C.

Shieh, W.

Tanaka, H.

Wang, W.

Winzer, P. J.

Xu, X.

Yang, Q.

Yi, X.

Zhu, B.

Zhuge, Q.

J. Lightwave Technol. (3)

J. Opt. Netw. (2)

Opt. Express (3)

Opt. Fiber Technol. (1)

A. J. Lowery and L. B. Du, “Optical orthogonal division multiplexing for long haul optical communications: A review of the last five years,” Opt. Fiber Technol. 17(5), 421–438 (2011).
[Crossref]

Other (6)

Q. Zhuge, B. Chatelain, and D. V. Plant, “Comparison of intra-channel nonlinearity tolerance between reduced-guard-interval CO-OFDM systems and nyquist single carrier systems,” in Proc. OFC’12, paper OTh1B.3 (2012).
[Crossref]

M. Sliskovic, “Carrier and sampling frequency offset estimation and correction in multicarrier systems,” in IEEE Global Telecommunications Conference,2001. GLOBECOM ’01 (IEEE, 2001), Vol.1, pp. 285–289.
[Crossref]

Y. Chen, S. Adhikari, N. Hanik, and S. L. Jansen, “Pilot-aided sampling frequency offset compensation for coherent optical OFDM,” in Proc. OFC’12, paper OTh4C (2012).
[Crossref]

S. K. Mitra, Digital Signal Processing: A Computer Based Approach, 4th ed. (McGraw Hill, 2011).

J. F. Kenney and E. S. Keeping, Mathematics of Statistics, 3rd ed. (Princeton, 1962).

M. Morsy-Osman, M. Chagnon, Q. Zhuge, X. Xu, and D. V. Plant, “Non-data-aided feedforward timing recovery for flexible transceivers employing PDM-MQAM modulations,” in Proc. OFC’14, paper W3B.4 (2014).
[Crossref]

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Figures (10)

Fig. 1
Fig. 1 Sample dislocations due to SFO. Green dots: correct sample positions. Black arrows: actual sample positions of OFDM symbol 1 because of SFO. Blue arrows: actual sample positions of OFDM symbol 2 because of SFO. DFT: discrete-Fourier-transform
Fig. 2
Fig. 2 Required CP overhead versus SFO. FL = 100
Fig. 3
Fig. 3 Block diagram of RGI CO-OFDM system with DA-SFOC. S/P: serial to parallel. P/S: parallel to serial. Mod.: modulation. Sync.: synchronization. Demod.: demodulation
Fig. 4
Fig. 4 OSNR penalty @ BER = 3.8e-3 vs. SFO for QPSK format. Solid lines: DA-SFOC. Dashed lines: PS-SFOC with perfect estimation
Fig. 5
Fig. 5 OSNR penalty @ BER = 3.8e-3 vs. SFO. (a) 8 QAM. (b) 16QAM. Solid lines: DA-SFOC. Dashed lines: PS-SFOC with perfect estimation
Fig. 6
Fig. 6 OSNR penalty @ BER = 3.8e-3 vs. OFDM symbol size
Fig. 7
Fig. 7 Experimental setup. PC: polarization controller. PBS/PBC: polarization beam splitter/combiner. ECL: external cavity laser. ODL: optical delay line. SW: switch.
Fig. 8
Fig. 8 Experimental result for QPSK. (a) Recovered constellation w/o DA-SFOC @ 200 ppm, OSNR = 14 dB. (b) BER vs. Received OSNR. (c) Recovered constellation with DA-SFOC @ 200 ppm, OSNR = 14 dB.
Fig. 9
Fig. 9 Experimental result for 8-QAM. (a) Recovered constellation w/o DA-SFOC @ 200 ppm, OSNR = 18 dB. (b) BER vs. Received OSNR. (c) Recovered constellation with DA-SFOC @ 200 ppm, OSNR = 18 dB.
Fig. 10
Fig. 10 Experimental result for 16-QAM. (a) Recovered constellation w/o DA-SFOC @ 200 ppm, OSNR = 24 dB. (b) BER vs. Received OSNR. (c) Recovered constellation with DA-SFOC @ 200 ppm, OSNR = 24 dB.

Equations (8)

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r ki = s ki h k e j ϕ i e j2πki ε s + η ki + n ki
ε s = Δf f s
| ε s |×( N DFT + N CP )×FL 1 2 × N CP
N CP 2×| ε s |× N DFT ×FL 12×| ε s |×FL
ϕ SFO ki = 1 min( k ' max ,k+m )max( k ' min ,km )+1 k'=km k+m arg( r k'( i1 ) CPE s ^ k'( i1 ) * )
s ^ ki =Decision( r ki e j i i1 ϕ SFO ki )(i N TS +1)
g[<n n 0 > N ] DFT G[k]exp( 2πk n 0 N )
ϕ SFO k = 2πn N k

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