Abstract

Coherent optical OFDM systems employ DAC at the transmitters and ADC at the receivers. The sample frequencies of DAC and ADC in such systems need to be synchronized, especially in the context of high-speed transmissions. This paper presents a channel model including the effect of the sample frequency offset, which adds an additional phase shift proportional to the subcarrier index. The sample frequency offset monitoring and the compensation method are discussed and verified in experiment. It is expected that the synchronization can be achieved by feeding the monitoring result back to the receiver oscillator.

© 2011 OSA

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References

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  1. W. Shieh and C. Athaudage, “Coherent optical orthogonal frequency division multiplexing,” Electron. Lett. 42(10), 587–589 (2006).
    [CrossRef]
  2. W. Shieh, X. Yi, and Y. Tang, “Transmission experiment of multi-gigabit coherent optical OFDM systems over 1000km SSMF fibre,” Electron. Lett. 43(3), 183–184 (2007).
    [CrossRef]
  3. S. L. Jansen, I. Morita, T. C. W. Schenk, N. Takeda, and H. Tanaka, “Coherent optical 25.8-Gb/s OFDM transmission over 4160-km SSMF,” J. Lightwave Technol. 26(1), 6–15 (2008).
    [CrossRef]
  4. Y. Ma, Q. Yang, Y. Tang, S. Chen, and W. Shieh, “1-Tb/s single-channel coherent optical OFDM transmission with orthogonal-band multiplexing and subwavelength bandwidth access,” J. Lightwave Technol. 28(4), 308–315 (2010).
    [CrossRef]
  5. X. Liu, S. Chandrasekhar, P. J. Winzer, S. Draving, J. Evangelista, N. Hoffman, B. Zhu, and D. W. Peckham, “Single coherent detection of a 606-Gb/s CO-OFDM signal with 32-QAM subcarrier modulation using 4x80-Gsamples/s ADCs,” in 36th European Conference and Exhibition onOptical Communication (ECOC), 2010 (2010), pp. 1–3.
  6. M. Sliskovic, “Sampling frequency offset estimation and correction in OFDM systems,” in The 8th IEEE International Conference on Electronics, Circuits and Systems, 2001 (ICECS 2001) (IEEE, 2001), Vol 1, pp. 437–440.
  7. 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.
  8. R. Dischler, A. Klekamp, F. Buchali, W. Idler, E. Lach, A. Schippel, M. Schneiders, S. Vorbeck, and R.-P. Braun, "Transmission of 3x253-Gb/s OFDM-superchannels over 764km field deployed single mode fibers," in National Fiber Optic Engineers Conference, OSA Technical Digest (CD) (Optical Society of America, 2010), paper PDPD2.
  9. R. P. Giddings and J. M. Tang, "World-first experimental demonstration of synchronous clock recovery in an 11.25Gb/s real-time end-to-end optical OFDM system using directly modulated DFBs," in Optical Fiber Communication Conference, OSA Technical Digest (CD) (Optical Society of America, 2011), paper OMS4.
  10. R. P. Giddings and J. M. Tang, “Experimental demonstration and optimisation of a synchronous clock recovery technique for real-time end-to-end optical OFDM transmission at 11.25Gb/s over 25km SSMF,” Opt. Express 19(3), 2831–2845 (2011).
    [CrossRef] [PubMed]
  11. X. Yi, W. Shieh, and Y. Ma, “Phase noise effects on high spectral efficiency coherent optical OFDM transmission,” J. Lightwave Technol. 26(10), 1309–1316 (2008).
    [CrossRef]
  12. X. Yi, W. Shieh, and Y. Tang, “Phase estimation for coherent optical OFDM,” IEEE Photon. Technol. Lett. 19(12), 919–921 (2007).
    [CrossRef]
  13. W. Shieh, X. Yi, Y. Ma, and Y. Tang, “Theoretical and experimental study on PMD-supported transmission using polarization diversity in coherent optical OFDM systems,” Opt. Express 15(16), 9936–9947 (2007).
    [CrossRef] [PubMed]

2011 (1)

2010 (1)

2008 (2)

2007 (3)

W. Shieh, X. Yi, and Y. Tang, “Transmission experiment of multi-gigabit coherent optical OFDM systems over 1000km SSMF fibre,” Electron. Lett. 43(3), 183–184 (2007).
[CrossRef]

X. Yi, W. Shieh, and Y. Tang, “Phase estimation for coherent optical OFDM,” IEEE Photon. Technol. Lett. 19(12), 919–921 (2007).
[CrossRef]

W. Shieh, X. Yi, Y. Ma, and Y. Tang, “Theoretical and experimental study on PMD-supported transmission using polarization diversity in coherent optical OFDM systems,” Opt. Express 15(16), 9936–9947 (2007).
[CrossRef] [PubMed]

2006 (1)

W. Shieh and C. Athaudage, “Coherent optical orthogonal frequency division multiplexing,” Electron. Lett. 42(10), 587–589 (2006).
[CrossRef]

Athaudage, C.

W. Shieh and C. Athaudage, “Coherent optical orthogonal frequency division multiplexing,” Electron. Lett. 42(10), 587–589 (2006).
[CrossRef]

Chen, S.

Giddings, R. P.

Jansen, S. L.

Ma, Y.

Morita, I.

Schenk, T. C. W.

Shieh, W.

Takeda, N.

Tanaka, H.

Tang, J. M.

Tang, Y.

Yang, Q.

Yi, X.

X. Yi, W. Shieh, and Y. Ma, “Phase noise effects on high spectral efficiency coherent optical OFDM transmission,” J. Lightwave Technol. 26(10), 1309–1316 (2008).
[CrossRef]

W. Shieh, X. Yi, and Y. Tang, “Transmission experiment of multi-gigabit coherent optical OFDM systems over 1000km SSMF fibre,” Electron. Lett. 43(3), 183–184 (2007).
[CrossRef]

X. Yi, W. Shieh, and Y. Tang, “Phase estimation for coherent optical OFDM,” IEEE Photon. Technol. Lett. 19(12), 919–921 (2007).
[CrossRef]

W. Shieh, X. Yi, Y. Ma, and Y. Tang, “Theoretical and experimental study on PMD-supported transmission using polarization diversity in coherent optical OFDM systems,” Opt. Express 15(16), 9936–9947 (2007).
[CrossRef] [PubMed]

Electron. Lett. (2)

W. Shieh and C. Athaudage, “Coherent optical orthogonal frequency division multiplexing,” Electron. Lett. 42(10), 587–589 (2006).
[CrossRef]

W. Shieh, X. Yi, and Y. Tang, “Transmission experiment of multi-gigabit coherent optical OFDM systems over 1000km SSMF fibre,” Electron. Lett. 43(3), 183–184 (2007).
[CrossRef]

IEEE Photon. Technol. Lett. (1)

X. Yi, W. Shieh, and Y. Tang, “Phase estimation for coherent optical OFDM,” IEEE Photon. Technol. Lett. 19(12), 919–921 (2007).
[CrossRef]

J. Lightwave Technol. (3)

Opt. Express (2)

Other (5)

X. Liu, S. Chandrasekhar, P. J. Winzer, S. Draving, J. Evangelista, N. Hoffman, B. Zhu, and D. W. Peckham, “Single coherent detection of a 606-Gb/s CO-OFDM signal with 32-QAM subcarrier modulation using 4x80-Gsamples/s ADCs,” in 36th European Conference and Exhibition onOptical Communication (ECOC), 2010 (2010), pp. 1–3.

M. Sliskovic, “Sampling frequency offset estimation and correction in OFDM systems,” in The 8th IEEE International Conference on Electronics, Circuits and Systems, 2001 (ICECS 2001) (IEEE, 2001), Vol 1, pp. 437–440.

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.

R. Dischler, A. Klekamp, F. Buchali, W. Idler, E. Lach, A. Schippel, M. Schneiders, S. Vorbeck, and R.-P. Braun, "Transmission of 3x253-Gb/s OFDM-superchannels over 764km field deployed single mode fibers," in National Fiber Optic Engineers Conference, OSA Technical Digest (CD) (Optical Society of America, 2010), paper PDPD2.

R. P. Giddings and J. M. Tang, "World-first experimental demonstration of synchronous clock recovery in an 11.25Gb/s real-time end-to-end optical OFDM system using directly modulated DFBs," in Optical Fiber Communication Conference, OSA Technical Digest (CD) (Optical Society of America, 2011), paper OMS4.

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Figures (5)

Fig. 1
Fig. 1

SNR degradation across the subcarriers, caused by the SFO in an electrical back-to-back setup. The dash lines are for the positive SFO and the solid lines for the negative SFO. The inset constellations are for two subcarriers with indices of −10 and 0, respectively.

Fig. 2
Fig. 2

Experimental setup.DMZ: dual Mach-Zehnder modulator, EDFA: erbium-doped fiber amplifier, PC: polarization controller.

Fig. 3
Fig. 3

Phase evolution of the 8 pilot subcarriers without the SFO compensation. The SFO is −1 MHz.

Fig. 4
Fig. 4

SNR distribution with or without the SFO compensation in an optical back-to-back setup. The SFO is −1 MHz.

Fig. 5
Fig. 5

BER results with the SFO compensation after the optical transmission. The inset constellation is with −1-MHz SFO.

Tables (1)

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Table 1 SFO monitoring results relative to 10 Gs/s.

Equations (6)

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ϕ i k = 2 π i k Δ f f s ,
y i k = x i k h k exp ( j Φ i + j ϕ i k ) + n i k ,
ϕ ¯ k = 2 π k Δ f f s = E i { arg ( y i k x i k ) arg ( y ( i 1 ) k x ( i 1 ) k ) } ,
Δ f = f s 2 π k E i { arg ( y i k x i k ) arg ( y ( i 1 ) k x ( i 1 ) k ) } ,
Φ ¯ i = E k { arg ( y i k x i k ) } ,
x ¯ i k = y i k exp ( j Φ ¯ i j ϕ ¯ i k ) h ¯ k * | h ¯ k | 2 ,

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