Abstract

A novel digital receiver architecture for coherent heterodyne-detected optical signals is presented. It demonstrates the application of bandpass sampling in an optical communications context, to overcome the high sampling rate requirement of conventional receivers (more than twice the signal bandwidth). The concept is targeted for WDM coherent optical access networks, where applying heterodyne detection constitutes a promising approach to reducing optical hardware complexity. The validity of the concept is experimentally assessed in a 76 km WDM-PON scenario, where the developed DSP achieves a 50% ADC rate reduction with penalty-free operation.

© 2012 OSA

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References

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  1. H. Rohde, S. Smolorz, J. S. Wey, and E. Gottwald, “Coherent Optical Access Networks,” in proceedings of Optical Fiber Communication Conference (OFC), OSA Technical Digest (Optical Society of America, 2011), paper OTuB1.
  2. C. E. Shannon, “Communication in the presence of noise,” Proc. Inst. Radio Eng.37, 10–21 (1949).
  3. J. Proakis and D. Manolakis, Digital Signal Processing, (Pearson Prentice Hall 2007).
  4. S. Dris, P. Bakopoulos, I. Lazarou, B. Schrenk, and H. Avramopoulos, “Low-Complexity DSP Using Undersampling for Heterodyne Receivers in Coherent Passive Optical Access Networks,” in European Conference and Exhibition on Optical Communication, OSA Technical Digest (online) (Optical Society of America, 2012), paper We.3.A.4.
  5. S. Smolorz, E. Gottwald, H. Rohde, D. Smith, and A. Poustie, “Demonstration of a Coherent UDWDM-PON with Real-Time Processing,” in proceedings of Optical Fiber Communication Conference (OFC), OSA Technical Digest (Optical Society of America, 2011), paper PDP4.
  6. R. Lyons, Understanding DSP, (Prentice Hall PTR 2001).
  7. R. G. Vaughan, N. L. Scott, and D. Rod White, “The theory of bandpass sampling,” IEEE Trans. Signal Process.39(9), 1973–1984 (1991).
    [CrossRef]
  8. A. Leven, N. Kaneda, U.-V. Koc, and Y.-K. Chen, “Frequency Estimation in Intradyne Reception,” IEEE Photon. Technol. Lett.19(6), 366–368 (2007).
    [CrossRef]
  9. E. Ip and J. M. Kahn, “Feedforward Carrier Recovery for Coherent Optical Communications,” J. Lightwave Technol.25,2675–2692 (2007).

2007 (2)

A. Leven, N. Kaneda, U.-V. Koc, and Y.-K. Chen, “Frequency Estimation in Intradyne Reception,” IEEE Photon. Technol. Lett.19(6), 366–368 (2007).
[CrossRef]

E. Ip and J. M. Kahn, “Feedforward Carrier Recovery for Coherent Optical Communications,” J. Lightwave Technol.25,2675–2692 (2007).

1991 (1)

R. G. Vaughan, N. L. Scott, and D. Rod White, “The theory of bandpass sampling,” IEEE Trans. Signal Process.39(9), 1973–1984 (1991).
[CrossRef]

1949 (1)

C. E. Shannon, “Communication in the presence of noise,” Proc. Inst. Radio Eng.37, 10–21 (1949).

Chen, Y.-K.

A. Leven, N. Kaneda, U.-V. Koc, and Y.-K. Chen, “Frequency Estimation in Intradyne Reception,” IEEE Photon. Technol. Lett.19(6), 366–368 (2007).
[CrossRef]

Ip, E.

E. Ip and J. M. Kahn, “Feedforward Carrier Recovery for Coherent Optical Communications,” J. Lightwave Technol.25,2675–2692 (2007).

Kahn, J. M.

E. Ip and J. M. Kahn, “Feedforward Carrier Recovery for Coherent Optical Communications,” J. Lightwave Technol.25,2675–2692 (2007).

Kaneda, N.

A. Leven, N. Kaneda, U.-V. Koc, and Y.-K. Chen, “Frequency Estimation in Intradyne Reception,” IEEE Photon. Technol. Lett.19(6), 366–368 (2007).
[CrossRef]

Koc, U.-V.

A. Leven, N. Kaneda, U.-V. Koc, and Y.-K. Chen, “Frequency Estimation in Intradyne Reception,” IEEE Photon. Technol. Lett.19(6), 366–368 (2007).
[CrossRef]

Leven, A.

A. Leven, N. Kaneda, U.-V. Koc, and Y.-K. Chen, “Frequency Estimation in Intradyne Reception,” IEEE Photon. Technol. Lett.19(6), 366–368 (2007).
[CrossRef]

Rod White, D.

R. G. Vaughan, N. L. Scott, and D. Rod White, “The theory of bandpass sampling,” IEEE Trans. Signal Process.39(9), 1973–1984 (1991).
[CrossRef]

Scott, N. L.

R. G. Vaughan, N. L. Scott, and D. Rod White, “The theory of bandpass sampling,” IEEE Trans. Signal Process.39(9), 1973–1984 (1991).
[CrossRef]

Shannon, C. E.

C. E. Shannon, “Communication in the presence of noise,” Proc. Inst. Radio Eng.37, 10–21 (1949).

Vaughan, R. G.

R. G. Vaughan, N. L. Scott, and D. Rod White, “The theory of bandpass sampling,” IEEE Trans. Signal Process.39(9), 1973–1984 (1991).
[CrossRef]

IEEE Photon. Technol. Lett. (1)

A. Leven, N. Kaneda, U.-V. Koc, and Y.-K. Chen, “Frequency Estimation in Intradyne Reception,” IEEE Photon. Technol. Lett.19(6), 366–368 (2007).
[CrossRef]

IEEE Trans. Signal Process. (1)

R. G. Vaughan, N. L. Scott, and D. Rod White, “The theory of bandpass sampling,” IEEE Trans. Signal Process.39(9), 1973–1984 (1991).
[CrossRef]

J. Lightwave Technol. (1)

E. Ip and J. M. Kahn, “Feedforward Carrier Recovery for Coherent Optical Communications,” J. Lightwave Technol.25,2675–2692 (2007).

Proc. Inst. Radio Eng. (1)

C. E. Shannon, “Communication in the presence of noise,” Proc. Inst. Radio Eng.37, 10–21 (1949).

Other (5)

J. Proakis and D. Manolakis, Digital Signal Processing, (Pearson Prentice Hall 2007).

S. Dris, P. Bakopoulos, I. Lazarou, B. Schrenk, and H. Avramopoulos, “Low-Complexity DSP Using Undersampling for Heterodyne Receivers in Coherent Passive Optical Access Networks,” in European Conference and Exhibition on Optical Communication, OSA Technical Digest (online) (Optical Society of America, 2012), paper We.3.A.4.

S. Smolorz, E. Gottwald, H. Rohde, D. Smith, and A. Poustie, “Demonstration of a Coherent UDWDM-PON with Real-Time Processing,” in proceedings of Optical Fiber Communication Conference (OFC), OSA Technical Digest (Optical Society of America, 2011), paper PDP4.

R. Lyons, Understanding DSP, (Prentice Hall PTR 2001).

H. Rohde, S. Smolorz, J. S. Wey, and E. Gottwald, “Coherent Optical Access Networks,” in proceedings of Optical Fiber Communication Conference (OFC), OSA Technical Digest (Optical Society of America, 2011), paper OTuB1.

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Figures (11)

Fig. 1
Fig. 1

Illustrating how the downstream signal is allocated to a wavelength further away from the upstream, in order to avoid the effects of Rayleigh backscattering.

Fig. 2
Fig. 2

Illustrating spectral replications in the digital frequency domain arising from bandpass sampling of an analog signal.

Fig. 3
Fig. 3

Regions of acceptable sampling rates (white), normalized to the signal bandwidth, from Eq. (3).

Fig. 4
Fig. 4

Proposed DSP for the coherent optical heterodyne receiver using bandpass sampling.

Fig. 5
Fig. 5

(a) The received signal in the time domain, oversampled at 50 GSa/s (blue dotted line) and bandpass sampled at 12.5 GSa/s (red circles). Corresponding spectra of the oversampled (b) and bandpass sampled (c) signal.

Fig. 6
Fig. 6

Evolution of the received signal in the receiver DSP, shown in IQ histogram plots: (a) After the Hilbert DDC. (b) Sampling point selection and decimation to the symbol rate. (c) Removal of the exponential term in Eq. (4). (d) Final constellation after frequency offset and carrier phase estimation.

Fig. 7
Fig. 7

Long-reach coherent PON layout for the evaluation of sub-Nyquistbandpass sampling.

Fig. 8
Fig. 8

(a) BER and (b) - (e) eye diagrams of the received DS after 76 km transmission for different wavelength detuning of the US and different sampling rates at the ONU receiver. (b) no US, (c) 4.5 GHz US, (d) 9.3 GHz US oversampled, (e) 9.3 GHz undersampled.

Fig. 9
Fig. 9

Received DS and RB at the ONU for (a) 4.5 GHz and (b) 9.3 GHz detuning of the US.

Fig. 10
Fig. 10

Acquired heterodyne spectra for 9.3 GHz detuning (IF) using 50 GSa/s (a) and 12.5 GSa/s (b) sampling rate. Undersampling causes downconversion of the heterodyne signal.

Fig. 11
Fig. 11

Close-up of Fig. 3 (m = 1), showing the chosen operating point.

Equations (4)

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2 f c B m f s 2 f c +B m+1
f L =2 f c B=2( f c B/2) f U =2 f c +B=2( f c +B/2)
2 f L m f U f U B f s B 2 (m+1) f U B
[ I(n T s )+jQ(n T s ) ]exp(j ω c2 n T s )

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