Abstract

Symbol synchronization constitutes a major component in optical OFDM transceivers. In this paper, we propose reducing the complexity of a blind symbol synchronization technique for direct detection OFDM receivers based on virtual subcarriers by optimizing the number and location of the virtual subcarriers. Compared to the system design in our previous study, this new technique offers a reduction of 92% in the number of virtual subcarriers (from 26 to 2 in a system with 50 data carrying subchannels) resulting in significant savings in complexity with a minimal penalty. Moreover, it offers an increase in the system capacity as more subcarriers can be used to transmit data. The technique was assessed experimentally using a transmission system of direct detection 16-QAM optical OFDM operating at a data rate of 30.65 Gb/s over 23.3 km SSMF with BER of 10−3. Negligible penalty was observed at high received powers. However, at low received powers, the number of averaging symbols had to be increased in order to improve the robustness of the method.

© 2015 Optical Society of America

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References

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  1. R. Giddings, “Real-time digital signal processing for optical OFDM-based future optical access networks,” J. Lightwave Technol. 32(4), 553–570 (2014).
    [Crossref]
  2. Y. Benlachtar, R. Bouziane, R. I. Killey, C. Berger, P. A. Milder, R. Koutsoyannis, J. C. Hoe, M. Püschel, and M. Glick, “Optical OFDM for the data center,” in Proc. International Conference on Transparent Optical Networks (ICTON2010), paper We.A4.3.
    [Crossref]
  3. T. M. Schmidl and D. C. Cox, “Robust frequency and timing synchronization for OFDM,” IEEE Trans. Commun. 45(12), 1613–1621 (1997).
    [Crossref]
  4. R. P. Giddings and J. M. Tang, “Real-Time experimental demonstration of a versatile optical OFDM symbol synchronization technique using low-power DC offset signaling,” in Proc. European Conference and Exhibition on Optical Communication (ECOC2011), paper We.9.A.3.
  5. R. Bouziane, Y. Benlachtar, and R. I. Killey, “Frequency-based frame synchronization for high-speed optical OFDM,” in Proc. Photonics in Switching Conference (PS2012), paper Th-S15–O12.
  6. R. Bouziane, R. Schmogrow, D. Hillerkuss, P. A. Milder, C. Koos, W. Freude, J. Leuthold, P. Bayvel, and R. I. Killey, “Generation and transmission of 85.4 Gb/s real-time 16QAM coherent optical OFDM signals over 400 km SSMF with preamble-less reception,” Opt. Express 20(19), 21612–21617 (2012).
    [Crossref] [PubMed]
  7. R. Bouziane, P. A. Milder, S. Kilmurray, B. C. Thomsen, S. Pachnicke, P. Bayvel, and R. I. Killey, “Blind symbol synchronization in direct-detection optical OFDM using virtual subcarriers,” in Proc. Optical Fiber Communication Conference, OSA Technical Digest (Optical Society of America, 2014), paper Th3K.5.
    [Crossref]
  8. R. Bouziane, P. A. Milder, S. Erkılınç, L. Galdino, S. Kilmurray, B. C. Thomsen, P. Bayvel, and R. I. Killey, “Experimental demonstration of 30 Gb/s direct-detection optical OFDM transmission with blind symbol synchronisation using virtual subcarriers,” Opt. Express 22(4), 4342–4348 (2014).
    [Crossref] [PubMed]
  9. H. Liu and U. Tureli, “A high-efficiency carrier estimator for OFDM communications,” IEEE Commun. Lett. 2(4), 104–106 (1998).
    [Crossref]
  10. U. Tureli, H. Liu, and M. D. Zoltowski, “OFDM blind carrier offset estimation: ESPRIT,” IEEE Trans. Commun. 48(9), 1459–1461 (2000).
    [Crossref]
  11. X. Ma, C. Tepedelenlioglu, G. B. Giannakis, and S. Barbarossa, “Non-data-aided carrier offset estimators for OFDM with null subcarriers: identifiability, algorithms, and performance,” IEEE J. Sel. Areas Comm. 19(12), 2504–2515 (2001).
    [Crossref]
  12. D. Huang and K. B. Letaief, “Carrier frequency offset estimation for OFDM systems using null sub-carriers,” IEEE Trans. Commun. 54(5), 813–823 (2006).
    [Crossref]
  13. R. Bouziane, “OFDM symbol synchronization with reduced complexity based on virtual subcarriers,” in Proc. IEEE Photonics Conference2014, paper MG3.3.
  14. N. Kaneda, Y. Qi, L. Xiang, S. Chandrasekhar, W. Shieh, and Y. Chen, “Real-time 2.5 GS/s coherent optical receiver for 53.3-Gb/s sub-banded OFDM,” J. Lightwave Technol. 28(4), 494–501 (2010).
    [Crossref]
  15. G. Goertzel, “An algorithm for the evaluation of finite trigonometric series,” Am. Math. Mon. 65(1), 34–35 (1958).
    [Crossref]

2014 (2)

2012 (1)

2010 (1)

2006 (1)

D. Huang and K. B. Letaief, “Carrier frequency offset estimation for OFDM systems using null sub-carriers,” IEEE Trans. Commun. 54(5), 813–823 (2006).
[Crossref]

2001 (1)

X. Ma, C. Tepedelenlioglu, G. B. Giannakis, and S. Barbarossa, “Non-data-aided carrier offset estimators for OFDM with null subcarriers: identifiability, algorithms, and performance,” IEEE J. Sel. Areas Comm. 19(12), 2504–2515 (2001).
[Crossref]

2000 (1)

U. Tureli, H. Liu, and M. D. Zoltowski, “OFDM blind carrier offset estimation: ESPRIT,” IEEE Trans. Commun. 48(9), 1459–1461 (2000).
[Crossref]

1998 (1)

H. Liu and U. Tureli, “A high-efficiency carrier estimator for OFDM communications,” IEEE Commun. Lett. 2(4), 104–106 (1998).
[Crossref]

1997 (1)

T. M. Schmidl and D. C. Cox, “Robust frequency and timing synchronization for OFDM,” IEEE Trans. Commun. 45(12), 1613–1621 (1997).
[Crossref]

1958 (1)

G. Goertzel, “An algorithm for the evaluation of finite trigonometric series,” Am. Math. Mon. 65(1), 34–35 (1958).
[Crossref]

Barbarossa, S.

X. Ma, C. Tepedelenlioglu, G. B. Giannakis, and S. Barbarossa, “Non-data-aided carrier offset estimators for OFDM with null subcarriers: identifiability, algorithms, and performance,” IEEE J. Sel. Areas Comm. 19(12), 2504–2515 (2001).
[Crossref]

Bayvel, P.

Bouziane, R.

Chandrasekhar, S.

Chen, Y.

Cox, D. C.

T. M. Schmidl and D. C. Cox, “Robust frequency and timing synchronization for OFDM,” IEEE Trans. Commun. 45(12), 1613–1621 (1997).
[Crossref]

Erkilinç, S.

Freude, W.

Galdino, L.

Giannakis, G. B.

X. Ma, C. Tepedelenlioglu, G. B. Giannakis, and S. Barbarossa, “Non-data-aided carrier offset estimators for OFDM with null subcarriers: identifiability, algorithms, and performance,” IEEE J. Sel. Areas Comm. 19(12), 2504–2515 (2001).
[Crossref]

Giddings, R.

Goertzel, G.

G. Goertzel, “An algorithm for the evaluation of finite trigonometric series,” Am. Math. Mon. 65(1), 34–35 (1958).
[Crossref]

Hillerkuss, D.

Huang, D.

D. Huang and K. B. Letaief, “Carrier frequency offset estimation for OFDM systems using null sub-carriers,” IEEE Trans. Commun. 54(5), 813–823 (2006).
[Crossref]

Kaneda, N.

Killey, R. I.

Kilmurray, S.

Koos, C.

Letaief, K. B.

D. Huang and K. B. Letaief, “Carrier frequency offset estimation for OFDM systems using null sub-carriers,” IEEE Trans. Commun. 54(5), 813–823 (2006).
[Crossref]

Leuthold, J.

Liu, H.

U. Tureli, H. Liu, and M. D. Zoltowski, “OFDM blind carrier offset estimation: ESPRIT,” IEEE Trans. Commun. 48(9), 1459–1461 (2000).
[Crossref]

H. Liu and U. Tureli, “A high-efficiency carrier estimator for OFDM communications,” IEEE Commun. Lett. 2(4), 104–106 (1998).
[Crossref]

Ma, X.

X. Ma, C. Tepedelenlioglu, G. B. Giannakis, and S. Barbarossa, “Non-data-aided carrier offset estimators for OFDM with null subcarriers: identifiability, algorithms, and performance,” IEEE J. Sel. Areas Comm. 19(12), 2504–2515 (2001).
[Crossref]

Milder, P. A.

Qi, Y.

Schmidl, T. M.

T. M. Schmidl and D. C. Cox, “Robust frequency and timing synchronization for OFDM,” IEEE Trans. Commun. 45(12), 1613–1621 (1997).
[Crossref]

Schmogrow, R.

Shieh, W.

Tepedelenlioglu, C.

X. Ma, C. Tepedelenlioglu, G. B. Giannakis, and S. Barbarossa, “Non-data-aided carrier offset estimators for OFDM with null subcarriers: identifiability, algorithms, and performance,” IEEE J. Sel. Areas Comm. 19(12), 2504–2515 (2001).
[Crossref]

Thomsen, B. C.

Tureli, U.

U. Tureli, H. Liu, and M. D. Zoltowski, “OFDM blind carrier offset estimation: ESPRIT,” IEEE Trans. Commun. 48(9), 1459–1461 (2000).
[Crossref]

H. Liu and U. Tureli, “A high-efficiency carrier estimator for OFDM communications,” IEEE Commun. Lett. 2(4), 104–106 (1998).
[Crossref]

Xiang, L.

Zoltowski, M. D.

U. Tureli, H. Liu, and M. D. Zoltowski, “OFDM blind carrier offset estimation: ESPRIT,” IEEE Trans. Commun. 48(9), 1459–1461 (2000).
[Crossref]

Am. Math. Mon. (1)

G. Goertzel, “An algorithm for the evaluation of finite trigonometric series,” Am. Math. Mon. 65(1), 34–35 (1958).
[Crossref]

IEEE Commun. Lett. (1)

H. Liu and U. Tureli, “A high-efficiency carrier estimator for OFDM communications,” IEEE Commun. Lett. 2(4), 104–106 (1998).
[Crossref]

IEEE J. Sel. Areas Comm. (1)

X. Ma, C. Tepedelenlioglu, G. B. Giannakis, and S. Barbarossa, “Non-data-aided carrier offset estimators for OFDM with null subcarriers: identifiability, algorithms, and performance,” IEEE J. Sel. Areas Comm. 19(12), 2504–2515 (2001).
[Crossref]

IEEE Trans. Commun. (3)

D. Huang and K. B. Letaief, “Carrier frequency offset estimation for OFDM systems using null sub-carriers,” IEEE Trans. Commun. 54(5), 813–823 (2006).
[Crossref]

U. Tureli, H. Liu, and M. D. Zoltowski, “OFDM blind carrier offset estimation: ESPRIT,” IEEE Trans. Commun. 48(9), 1459–1461 (2000).
[Crossref]

T. M. Schmidl and D. C. Cox, “Robust frequency and timing synchronization for OFDM,” IEEE Trans. Commun. 45(12), 1613–1621 (1997).
[Crossref]

J. Lightwave Technol. (2)

Opt. Express (2)

Other (5)

Y. Benlachtar, R. Bouziane, R. I. Killey, C. Berger, P. A. Milder, R. Koutsoyannis, J. C. Hoe, M. Püschel, and M. Glick, “Optical OFDM for the data center,” in Proc. International Conference on Transparent Optical Networks (ICTON2010), paper We.A4.3.
[Crossref]

R. P. Giddings and J. M. Tang, “Real-Time experimental demonstration of a versatile optical OFDM symbol synchronization technique using low-power DC offset signaling,” in Proc. European Conference and Exhibition on Optical Communication (ECOC2011), paper We.9.A.3.

R. Bouziane, Y. Benlachtar, and R. I. Killey, “Frequency-based frame synchronization for high-speed optical OFDM,” in Proc. Photonics in Switching Conference (PS2012), paper Th-S15–O12.

R. Bouziane, “OFDM symbol synchronization with reduced complexity based on virtual subcarriers,” in Proc. IEEE Photonics Conference2014, paper MG3.3.

R. Bouziane, P. A. Milder, S. Kilmurray, B. C. Thomsen, S. Pachnicke, P. Bayvel, and R. I. Killey, “Blind symbol synchronization in direct-detection optical OFDM using virtual subcarriers,” in Proc. Optical Fiber Communication Conference, OSA Technical Digest (Optical Society of America, 2014), paper Th3K.5.
[Crossref]

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Figures (10)

Fig. 1
Fig. 1 Block diagram of the main DSP blocks in OFDM transceivers (a) transmitter, (b) receiver (CP: Cyclic prefix, synch.: synchronization).
Fig. 2
Fig. 2 Illustration of the window alignment of the receiver FFT with the transmitter IFFT for different values of misalignment ∆t = 0 and ∆t = 2 samples.
Fig. 3
Fig. 3 Relationship between the symbol timing offset and the power of virtual subcarriers, Pvsc, (a) power of each subcarrier in a single OFDM symbol for two values of misalignment, ∆(t), (b) Power profile of VSCs (Pvsc versus all possible symbol offsets) using 100 averaging symbols, the correct symbol offset is 116 samples where the trough is located.
Fig. 4
Fig. 4 Block diagram of the transmitter DSP.
Fig. 5
Fig. 5 Experimental system setup. VOA: variable optical attenuator, EDFA: erbium-doped fiber amplifier, Rx: receiver.
Fig. 6
Fig. 6 OFDM symbol structure with the optimized locations of the two VSCs used in symbol synchronization (all data subcarriers are assumed to have the same power for clarity purposes).
Fig. 7
Fig. 7 Power of virtual subcarriers versus symbol offset in the back-to-back case with 2 dBm received optical power and different numbers of averaging symbols (a) 2 VSCs and 200 averaging symbols, (b) 26 VSCs and 200 averaging symbols, (c) 2 VSCs for a range of averaging symbols, (d) 26 VSCs for a range of averaging symbols, (e) constellation diagram of the received signal.
Fig. 8
Fig. 8 Performance comparison between the S&C algorithm, the synchronization algorithm using 26 VSCs and the proposed method of 2 VSCs in the optical back-to-back configuration using different numbers of averaging symbols: (a) 200, (b) 100, (c) 50, (d) 20, (e) 10. (f) Minimum received power to match the performance of the previously reported method (using 26 VSCs) vs. number of averaging symbols.
Fig. 9
Fig. 9 Performance comparison between the S&C algorithm, the synchronization algorithm using 26 VSCs and the proposed method of 2 VSCs in the transmission over 23.3 km SSMF configuration using different numbers of averaging symbols: (a) 200, (b) 100, (c) 50, (d) 20, (e) 10. (f) Minimum received power to match the performance of the previously reported method (using 26 VSCs) vs. number of averaging symbols.
Fig. 10
Fig. 10 Block diagram of the synchronization circuit.

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