Abstract

In coherent optical communication systems, the transmitter usually employs an optical in-phase and quadrature (IQ) modulator to perform electrical-to-optical up-conversion. However, some environmental factors, such as temperature and mechanical stress, strongly influence the stability. To stabilize the quality of the transmitted signal, auto bias control (ABC) is essential to keep modulator in optimum bias. In this paper, we present a novel method of ABC for the optical orthogonal frequency division multiplexing (O-OFDM) signal. In the proposed scheme, a small cosine/sine wave dither signal is added on to the I/Q baseband signal, respectively. Based on the power monitoring of the 1st and 2nd harmonics of the dither signal, the biases of the optical IQ modulator for O-OFDM system can be adjusted very precisely. The simulation and experimental results show good performance on locating the optimum bias voltages for the IQ modulator with high precision.

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References

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  1. G. Li, “Recent advances in coherent optical communication,” Adv. Opt. Photon.1(2), 279–307 (2009).
    [CrossRef]
  2. I. B. Djordjevic and B. Vasic, “Orthogonal frequency division multiplexing for high-speed optical transmission,” Opt. Express14(9), 3767–3775 (2006).
    [CrossRef] [PubMed]
  3. W. Shieh and C. Athaudage, “Coherent optical orthogonal frequency division multiplexing,” Electron. Lett.42(10), 587–589 (2006).
    [CrossRef]
  4. W. Shieh, H. Bao, and Y. Tang, “Coherent optical OFDM: theory and design,” Opt. Express16(2), 841–859 (2008).
    [CrossRef] [PubMed]
  5. T. Sugihara, T. Yoshida, and K. Ishida, “Effect of Modulator Bias Control in the Presence of a Finite Extinction Ratio in DQPSK Pre-equalization Systems,” J. Lightwave Technol.29(15), 2235–2248 (2011).
  6. K. Sekine, C. Hasegawa, N. Kikuchi, and S. Sasaki, “A Novel Bias Control Technique for MZ Modulator with Monitoring Power of Backward Light for Advanced Modulation Formats,” in Proc. of OFC (2007), Paper. OTuH5.
  7. H. Kawakami, E. Yoshida, and Y. Miyamoto, “Asymmetric dithering technique for bias condition monitoring in optical QPSK modulator,” Electron. Lett.46(6), 430–431 (2010).
    [CrossRef]
  8. H. Kawakami, T. Kobayashi, E. Yoshida, and Y. Miyamoto, “Auto bias control technique for optical 16-QAM transmitter with asymmetric bias dithering,” Opt. Express19(26), B308–B312 (2011).
    [CrossRef] [PubMed]
  9. H. Choi, Y. Takushima, H. Y. Choi, J. H. Chang, and Y. C. Chung, “Modulation-Format-Free Bias Control Technique for MZ Modulator Based on Differential Phasor Monitor,” in Proc. of OFC (2011), Paper. JWA033.
  10. P. S. Cho and M. Nazarathy, “Bias control for optical OFDM transmitters,” IEEE Photon. Technol. Lett.22(14), 1030–1032 (2010).
    [CrossRef]
  11. Q. Yang, Y. Ma, and W. Shieh, “107 Gb/s Coherent Optical OFDM Reception Using Orthogonal Band Multiplexing,” in Proc. of OFC (2008), Paper. PDP7.

2011 (2)

2010 (2)

H. Kawakami, E. Yoshida, and Y. Miyamoto, “Asymmetric dithering technique for bias condition monitoring in optical QPSK modulator,” Electron. Lett.46(6), 430–431 (2010).
[CrossRef]

P. S. Cho and M. Nazarathy, “Bias control for optical OFDM transmitters,” IEEE Photon. Technol. Lett.22(14), 1030–1032 (2010).
[CrossRef]

2009 (1)

2008 (1)

2006 (2)

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

I. B. Djordjevic and B. Vasic, “Orthogonal frequency division multiplexing for high-speed optical transmission,” Opt. Express14(9), 3767–3775 (2006).
[CrossRef] [PubMed]

Athaudage, C.

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

Bao, H.

Cho, P. S.

P. S. Cho and M. Nazarathy, “Bias control for optical OFDM transmitters,” IEEE Photon. Technol. Lett.22(14), 1030–1032 (2010).
[CrossRef]

Djordjevic, I. B.

Ishida, K.

Kawakami, H.

H. Kawakami, T. Kobayashi, E. Yoshida, and Y. Miyamoto, “Auto bias control technique for optical 16-QAM transmitter with asymmetric bias dithering,” Opt. Express19(26), B308–B312 (2011).
[CrossRef] [PubMed]

H. Kawakami, E. Yoshida, and Y. Miyamoto, “Asymmetric dithering technique for bias condition monitoring in optical QPSK modulator,” Electron. Lett.46(6), 430–431 (2010).
[CrossRef]

Kobayashi, T.

Li, G.

Miyamoto, Y.

H. Kawakami, T. Kobayashi, E. Yoshida, and Y. Miyamoto, “Auto bias control technique for optical 16-QAM transmitter with asymmetric bias dithering,” Opt. Express19(26), B308–B312 (2011).
[CrossRef] [PubMed]

H. Kawakami, E. Yoshida, and Y. Miyamoto, “Asymmetric dithering technique for bias condition monitoring in optical QPSK modulator,” Electron. Lett.46(6), 430–431 (2010).
[CrossRef]

Nazarathy, M.

P. S. Cho and M. Nazarathy, “Bias control for optical OFDM transmitters,” IEEE Photon. Technol. Lett.22(14), 1030–1032 (2010).
[CrossRef]

Shieh, W.

W. Shieh, H. Bao, and Y. Tang, “Coherent optical OFDM: theory and design,” Opt. Express16(2), 841–859 (2008).
[CrossRef] [PubMed]

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

Sugihara, T.

Tang, Y.

Vasic, B.

Yoshida, E.

H. Kawakami, T. Kobayashi, E. Yoshida, and Y. Miyamoto, “Auto bias control technique for optical 16-QAM transmitter with asymmetric bias dithering,” Opt. Express19(26), B308–B312 (2011).
[CrossRef] [PubMed]

H. Kawakami, E. Yoshida, and Y. Miyamoto, “Asymmetric dithering technique for bias condition monitoring in optical QPSK modulator,” Electron. Lett.46(6), 430–431 (2010).
[CrossRef]

Yoshida, T.

Adv. Opt. Photon. (1)

Electron. Lett. (2)

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

H. Kawakami, E. Yoshida, and Y. Miyamoto, “Asymmetric dithering technique for bias condition monitoring in optical QPSK modulator,” Electron. Lett.46(6), 430–431 (2010).
[CrossRef]

IEEE Photon. Technol. Lett. (1)

P. S. Cho and M. Nazarathy, “Bias control for optical OFDM transmitters,” IEEE Photon. Technol. Lett.22(14), 1030–1032 (2010).
[CrossRef]

J. Lightwave Technol. (1)

Opt. Express (3)

Other (3)

Q. Yang, Y. Ma, and W. Shieh, “107 Gb/s Coherent Optical OFDM Reception Using Orthogonal Band Multiplexing,” in Proc. of OFC (2008), Paper. PDP7.

H. Choi, Y. Takushima, H. Y. Choi, J. H. Chang, and Y. C. Chung, “Modulation-Format-Free Bias Control Technique for MZ Modulator Based on Differential Phasor Monitor,” in Proc. of OFC (2011), Paper. JWA033.

K. Sekine, C. Hasegawa, N. Kikuchi, and S. Sasaki, “A Novel Bias Control Technique for MZ Modulator with Monitoring Power of Backward Light for Advanced Modulation Formats,” in Proc. of OFC (2007), Paper. OTuH5.

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Figures (9)

Fig. 1
Fig. 1

The auto bias control configuration.

Fig. 2
Fig. 2

The relative power as a function of (a)φbias,I and φbias,Q, (b)φbias,I with differentφbias,Q andφIQ.

Fig. 3
Fig. 3

The power of the 2nd harmonic vs.φIQ with differentφbias,I andφbias,Q;

Fig. 4
Fig. 4

The power of (a) the 1st harmonic versusφbias,I andφbias,Q, (b) the 1st harmonic component versusφbias,I.

Fig. 5
Fig. 5

Experimental setup for evaluation the proposed auto bias control technique.

Fig. 6
Fig. 6

The current power as a function of △φbias,I.

Fig. 7
Fig. 7

The 2nd harmonic component power as a function of △φIQ

Fig. 8
Fig. 8

The 1st harmonic power as a function of φbias,I

Fig. 9
Fig. 9

The BER performance of a 10.6 Gb/s OFDM signals with and without dither signal

Equations (9)

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E o = E i 2 [cos( π 2 V I + V bias,I V π )+cos( π 2 V Q + V bias,Q V π ) e j ϕ IQ ]
P o = P i 8 [ 2+cos( ϕ I + ϕ bias,I )+cos( ϕ Q + ϕ bias,Q )+4cos ( ϕ I + ϕ bias,I ) 2 cos ( ϕ Q + ϕ bias,Q ) 2 cos ϕ IQ ]
V bias,I = V π + V drift,I + V dith cos( ω dith t) V bias,Q = V π + V drift,Q + V dith sin( ω dith t)
V I (t)= 2 N sc Re{ c k }cos( 2π f s (k1)t ) V Q (t)= 2 N sc Im{ c k }sin( 2π f s (k1)t )
F 1 =2+cos( ϕ I + ϕ bias,I )+cos( ϕ Q + ϕ bias,Q ) F 2 =4cos( ϕ I + ϕ bias,I 2 )cos( ϕ Q + ϕ bias,Q 2 )cos ϕ IQ
F 1 (t)21+ ( ϕ I + ϕ bias,I +π ) 2 2 1+ ( ϕ Q + ϕ bias,Q +π ) 2 2 = π 2 V π 2 ( V I (t)+ V drift,I + V dith cos(2π f dith t) ) 2 2 + π 2 V π 2 ( V Q (t)+ V drift,Q + V dith sin(2π f dith t) ) 2 2 = π 2 2 V π 2 ( 2 V dith [ V drift,I cos(2π f dith t)+ V drift,Q sin(2π f dith t) ]+ V dith 2 + V drift,I 2 + V drift,Q 2 ) + π 2 2 V π 2 ( V I 2 (t)+ V Q 2 (t)+2 V I (t)( V drift,I + V dith cos(2π f dith t) )+2 V Q (t)( V drift,Q + V dith sin(2π f dith t)) )
F 2 (t)=4sin( ϕ I + ϕ bias,I +π 2 )sin( ϕ Q + ϕ bias,Q +π 2 )cos ϕ IQ 4( ϕ I + ϕ bias,I +π 2 )( ϕ Q + ϕ bias,Q +π 2 )cos ϕ IQ = π 2 ( V I (t)+ V drift,I + V dith cos(2π f dith t) V π V Q (t)+ V drift,Q + V dith sin(2π f dith t) V π )cos ϕ IQ = π 2 V π 2 { V drift,I V drift,Q + V dith [ V drift,Q cos( ω dith t)+ V drift,I sin( ω dith t)]+0.5 V dith 2 cos(2 ω dith t)}cos ϕ IQ + π 2 V π 2 { V I (t) V Q (t)+ V I (t) V dith cos(2π f dith t)+ V I (t) V drift,I + V Q (t) V drift,Q + V Q (t) V dith sin(2π f dith t)}cos ϕ IQ
F 1 (t) π 2 2 V π 2 { V drift,I 2 + V drift,Q 2 + V dith 2 DC harmonic component + 2 V dith [ V drift,I cos(2π f dith t)+ V drift,Q sin(2π f dith t) ] 1 st harmonic component }
F 2 (t) π 2 V π 2 { V dith [ V drift,Q cos(2π f dith t)+ V drift,I sin(2π f dith t) ] 1 st harmonic component + 0.5 V dith 2 cos(4π f dith t) 2 nd harmonic component }cos ϕ IQ

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