Abstract

Transmitter and receiver IQ imbalance causes image interference that degrades performance in high capacity and high spectral efficiency optical orthogonal frequency division multiplexing (OFDM) schemes. Digital compensation is an attractive method to relax component specifications. In this paper we report the details of a hybrid compensation method for IQ imbalance compensation, comprising of orthogonal training symbol-based method for transmitter-side compensation and an iterative image reduction-based method for receiver-side imbalance compensation. We demonstrate performance improvement using the hybrid method in presence of frequency dependent imbalance by both simulation and back-to-back direct detection optical OFDM experiment. We report on the tolerable limit of transmitter IQ imbalance under presence of carrier frequency offset.

© 2010 OSA

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References

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  1. S. L. Jansen, I. Morita, T. C. W. Schenk, and H. Tanaka, “121.9-Gb/s PDM-OFDM transmission with 2 b/s/Hz spectral efficiency over 1,000 km of SSMF,” J. Lightwave Technol. 27(3), 177–188 (2009).
    [CrossRef]
  2. Y. Ma, Q. Yang, Y. Tang, S. Chen, and W. Shieh, “1-Tb/s single-channel coherent optical OFDM transmission over 600-km SSMF fiber with subwavelength bandwidth access,” Opt. Express 17(11), 9421–9427 (2009).
    [CrossRef] [PubMed]
  3. H. Takahashi, A. Al Amin, S. L. Jansen, I. Morita, and H. Tanaka, “Highly spectrally efficient DWDM transmission at 7.0 bit/s/Hz using 8x65.1-Gbit/s coherent PDM-OFDM,” J. Lightwave Technol. 28, 406–414 (2009).
    [CrossRef]
  4. B. J. C. Schmidt, Z. Zan, L. B. Du, and A. J. Lowery, “100 Gbit/s transmission using single band direct‐detection optical OFDM,” in Proceedings of Optical Fiber Commun. Conf., (San Diego, 2009), PDPC3.
  5. D. Qian, N. Cvijetic, J. Hu, and T. Wang, “108Gb/s OFDMA‐PON with polarization multiplexing and direct detection,” in Proceedings of Optical Fiber Commun. Conf., (San Diego, 2009), PDPD5.
  6. B. J. C. Schmidt, A. J. Lowery, and J. Armstrong, “Experimental demonstrations of electronic dispersion compensation for long-haul transmission using direct-detection optical OFDM,” J. Lightwave Technol. 26(1), 196–203 (2008).
    [CrossRef]
  7. M. Valkama, M. Renfors, and V. Koivunen, “Advanced methods for I/Q imbalance compensation in communication receivers,” IEEE Trans. Signal Process. 49(10), 2335–2344 (2001).
    [CrossRef]
  8. T. C. W. Schenk, RF Imperfections in High-rate Wireless Systems, (Springer, 2008), Chapter 5.
  9. W. R. Peng, B. Zhang, and X. Wu, K. M. Feng A. E. Willner and S. Chi, “Experimental demonstration of compensating the I/Q imbalance and bias deviation of the Mach-Zehnder modulator for an RF-tone assisted optical OFDM system,” in Proceedings of Europ. Conf. on Opt. Commun. (Amsterdam, 2008), Mo.4.D.3.
  10. Y. Ma, W. Shieh, and Q. Yang, “Bandwidth-Efficient 21.4 Gb/s Coherent Optical 2×2 MIMO OFDM Transmission,” in Proceedings of Optical Fiber Commun. Conf., (San Diego, 2008), JWA 59.
  11. A. Al Amin, H. Takahashi, S. L. Jansen, I. Morita, and H. Tanaka, “Effect of hybrid IQ imbalance compensation in 27.3-Gbit/s direct-detection OFDM transmission,” in Proceedings of Optical Fiber Commun. Conf., (San Diego, 2009), OTuO2.
  12. Numerical Recipes: The Art of Scientific Computing, Available at: http://www.nr.com .

2009 (3)

2008 (1)

B. J. C. Schmidt, A. J. Lowery, and J. Armstrong, “Experimental demonstrations of electronic dispersion compensation for long-haul transmission using direct-detection optical OFDM,” J. Lightwave Technol. 26(1), 196–203 (2008).
[CrossRef]

2001 (1)

M. Valkama, M. Renfors, and V. Koivunen, “Advanced methods for I/Q imbalance compensation in communication receivers,” IEEE Trans. Signal Process. 49(10), 2335–2344 (2001).
[CrossRef]

Al Amin, A.

Armstrong, J.

B. J. C. Schmidt, A. J. Lowery, and J. Armstrong, “Experimental demonstrations of electronic dispersion compensation for long-haul transmission using direct-detection optical OFDM,” J. Lightwave Technol. 26(1), 196–203 (2008).
[CrossRef]

Chen, S.

Jansen, S. L.

Koivunen, V.

M. Valkama, M. Renfors, and V. Koivunen, “Advanced methods for I/Q imbalance compensation in communication receivers,” IEEE Trans. Signal Process. 49(10), 2335–2344 (2001).
[CrossRef]

Lowery, A. J.

B. J. C. Schmidt, A. J. Lowery, and J. Armstrong, “Experimental demonstrations of electronic dispersion compensation for long-haul transmission using direct-detection optical OFDM,” J. Lightwave Technol. 26(1), 196–203 (2008).
[CrossRef]

Ma, Y.

Morita, I.

Renfors, M.

M. Valkama, M. Renfors, and V. Koivunen, “Advanced methods for I/Q imbalance compensation in communication receivers,” IEEE Trans. Signal Process. 49(10), 2335–2344 (2001).
[CrossRef]

Schenk, T. C. W.

Schmidt, B. J. C.

B. J. C. Schmidt, A. J. Lowery, and J. Armstrong, “Experimental demonstrations of electronic dispersion compensation for long-haul transmission using direct-detection optical OFDM,” J. Lightwave Technol. 26(1), 196–203 (2008).
[CrossRef]

Shieh, W.

Takahashi, H.

Tanaka, H.

Tang, Y.

Valkama, M.

M. Valkama, M. Renfors, and V. Koivunen, “Advanced methods for I/Q imbalance compensation in communication receivers,” IEEE Trans. Signal Process. 49(10), 2335–2344 (2001).
[CrossRef]

Yang, Q.

J. Lightwave Technol. (1)

B. J. C. Schmidt, A. J. Lowery, and J. Armstrong, “Experimental demonstrations of electronic dispersion compensation for long-haul transmission using direct-detection optical OFDM,” J. Lightwave Technol. 26(1), 196–203 (2008).
[CrossRef]

IEEE Trans. Signal Process. (1)

M. Valkama, M. Renfors, and V. Koivunen, “Advanced methods for I/Q imbalance compensation in communication receivers,” IEEE Trans. Signal Process. 49(10), 2335–2344 (2001).
[CrossRef]

J. Lightwave Technol. (2)

Opt. Express (1)

Other (7)

B. J. C. Schmidt, Z. Zan, L. B. Du, and A. J. Lowery, “100 Gbit/s transmission using single band direct‐detection optical OFDM,” in Proceedings of Optical Fiber Commun. Conf., (San Diego, 2009), PDPC3.

D. Qian, N. Cvijetic, J. Hu, and T. Wang, “108Gb/s OFDMA‐PON with polarization multiplexing and direct detection,” in Proceedings of Optical Fiber Commun. Conf., (San Diego, 2009), PDPD5.

T. C. W. Schenk, RF Imperfections in High-rate Wireless Systems, (Springer, 2008), Chapter 5.

W. R. Peng, B. Zhang, and X. Wu, K. M. Feng A. E. Willner and S. Chi, “Experimental demonstration of compensating the I/Q imbalance and bias deviation of the Mach-Zehnder modulator for an RF-tone assisted optical OFDM system,” in Proceedings of Europ. Conf. on Opt. Commun. (Amsterdam, 2008), Mo.4.D.3.

Y. Ma, W. Shieh, and Q. Yang, “Bandwidth-Efficient 21.4 Gb/s Coherent Optical 2×2 MIMO OFDM Transmission,” in Proceedings of Optical Fiber Commun. Conf., (San Diego, 2008), JWA 59.

A. Al Amin, H. Takahashi, S. L. Jansen, I. Morita, and H. Tanaka, “Effect of hybrid IQ imbalance compensation in 27.3-Gbit/s direct-detection OFDM transmission,” in Proceedings of Optical Fiber Commun. Conf., (San Diego, 2009), OTuO2.

Numerical Recipes: The Art of Scientific Computing, Available at: http://www.nr.com .

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Figures (6)

Fig. 1
Fig. 1

Schematic of Tx and Rx in optical OFDM, showing possible IQ imbalance paths its effects. (a) Optical IQ modulator based Tx, (b) RF IQ mixer based upconverter for Tx, (c) coherent optical Rx, (d) Direct detection OFDM Rx with RF down conversion.

Fig. 2
Fig. 2

(a) Mutually orthogonal preamble for Tx IQ compensation, (b) Schematic spectrum showing two input signals for Rx IQ imbalance adjustment, with resultant image bands due to imbalance in the direct conversion receiver, which is minimized by iterative algorithm.

Fig. 3
Fig. 3

Simulation results for Tx-side IQ imbalance compensation with ideal receiver. (a) Comparison of actual amplitude and phase imbalance (assumed to be linearly frequency dependent) with estimation results. OSNR is at 20 dB. (b) Received Es/No for each subcarrier in the case of (a), with and without Tx IQ imbalance compensation. Inset shows constellation for all carriers.

Fig. 4
Fig. 4

Simulated spectrum of LSB (left) and USB (right) OFDM test signal before and after iterative SA-based image minimization for Rx IQ imbalance compensation. Linearly varying amplitude imbalance of 30% (peak) and phase imbalance of 0.37 rad (peak) is assumed.

Fig. 5
Fig. 5

Experimental setup for single-band, 27.3Gbit/s 16QAM DD-OFDM transmission for demonstration of the hybrid IQ imbalance compensation method.

Fig. 6
Fig. 6

Effect of the varying Tx IQ imbalances on the back-to-back DD-OFDM transmission at OSNR of 34 dB for cases of frequency dependent IQ imbalance compensation (Tx/Rx comp) and no IQ compensation (No Tx/Rx comp). Also the case of frequency independent (F.I.) Tx IQ compensation (method of Ref [8].) is demonstrated for comparison. (a) with added amplitude imbalance (phase imbalance minimum). (b) with added phase imbalance (amplitude imbalance minimum). Imbalance values are nominal offset from initial coarse setting. Here each ps of delay corresponds to 0.02 rad phase difference at the highest frequency subcarriers.

Equations (3)

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( x ( k ) x ( k ) ) = ( H ( k ) 0 0 H ( k ) ) ( s ( k ) s ( k ) )
( H ( k ) G 1 ( k ) H ( k ) G 2 ( k ) H ( k ) G 2 ( k ) H ( k ) G 1 ( k ) )
G 1 ( k ) = ( 1 + α ( k ) e j β ( k ) ) / 2 , G 2 ( k ) = ( 1 α ( k ) e j β ( k ) ) / 2

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