Abstract

We propose a spectrally slicing-and-synthesizing coherent optical spectrum analyzer to measure complex field waveforms of quadrature amplitude modulation (QAM) optical signals with ultralong periods. The optical spectrum of a measured optical signal is divided into multiple narrowband spectral components, called slices. The slices are sequentially measured using low-speed coherent detection. After phase noise suppression and frequency fluctuation compensation on each slice, the measured slices are synthesized to recover the original signal spectrum. Our numerical and experimental results confirm that the proposed method can overcome the limitation of the measurement bandwidth because the signal spectrum can synthesize more than 100 slices. We experimentally demonstrate complex field measurements of 16QAM optical signals. Our method can measure high-speed optical complex field waveforms with no bandwidth limitation.

© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

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References

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  1. K. Roberts, M. O’Sullivan, K.-T. Wu, H. Sun, A. Awadalla, D. J. Krause, and C. Laperle, “Performance of Dual-Polarization QPSK for Optical Transport Systems,” J. Lightwave Technol. 27(16), 3546–3559 (2009).
    [Crossref]
  2. K. Kikuchi, “Fundamentals of Coherent Optical Fiber Communications,” J. Lightwave Technol. 34(1), 157–179 (2016).
    [Crossref]
  3. F. N. Hauske, M. Kuschnerov, B. Spinnler, and B. Lankl, “Optical Performance Monitoring in Digital Coherent Receivers,” J. Lightwave Technol. 27(16), 3623–3631 (2009).
    [Crossref]
  4. K. Okamoto and F. Ito, “Nearly Shot-Noise-Limited Performance of Dual-Channel Linear Sampling for Ultrafast DPSK Signals,” IEEE J. Quantum Electron. 45(6), 711–719 (2009).
    [Crossref]
  5. K. Kikuchi and S. Y. Set, “Proposal of Optical-Sampling-Based Constellation Monitor for DP-QPSK Signals,” OECC2013, TuR2-1 (2013).
  6. K. Igarashi and N. Urakawa, “Constellation Monitor of QPSK Optical Signals Based on Spectrally-sliced Coherent Optical Spectrum Analyzers,” OECC2019, ThC2-4 (2019).
  7. Y. Kawabata, N. Urakawa, K. Kinoshita, and K. Igarashi, “Spectrally Slicing Coherent Optical Spectrum Analyzer for Measuring Complex Field Waveforms of Optical QAM Signals,” OFC2020, W4A.1 (2020).

2016 (1)

2009 (3)

Awadalla, A.

Hauske, F. N.

Igarashi, K.

Y. Kawabata, N. Urakawa, K. Kinoshita, and K. Igarashi, “Spectrally Slicing Coherent Optical Spectrum Analyzer for Measuring Complex Field Waveforms of Optical QAM Signals,” OFC2020, W4A.1 (2020).

K. Igarashi and N. Urakawa, “Constellation Monitor of QPSK Optical Signals Based on Spectrally-sliced Coherent Optical Spectrum Analyzers,” OECC2019, ThC2-4 (2019).

Ito, F.

K. Okamoto and F. Ito, “Nearly Shot-Noise-Limited Performance of Dual-Channel Linear Sampling for Ultrafast DPSK Signals,” IEEE J. Quantum Electron. 45(6), 711–719 (2009).
[Crossref]

Kawabata, Y.

Y. Kawabata, N. Urakawa, K. Kinoshita, and K. Igarashi, “Spectrally Slicing Coherent Optical Spectrum Analyzer for Measuring Complex Field Waveforms of Optical QAM Signals,” OFC2020, W4A.1 (2020).

Kikuchi, K.

K. Kikuchi, “Fundamentals of Coherent Optical Fiber Communications,” J. Lightwave Technol. 34(1), 157–179 (2016).
[Crossref]

K. Kikuchi and S. Y. Set, “Proposal of Optical-Sampling-Based Constellation Monitor for DP-QPSK Signals,” OECC2013, TuR2-1 (2013).

Kinoshita, K.

Y. Kawabata, N. Urakawa, K. Kinoshita, and K. Igarashi, “Spectrally Slicing Coherent Optical Spectrum Analyzer for Measuring Complex Field Waveforms of Optical QAM Signals,” OFC2020, W4A.1 (2020).

Krause, D. J.

Kuschnerov, M.

Lankl, B.

Laperle, C.

O’Sullivan, M.

Okamoto, K.

K. Okamoto and F. Ito, “Nearly Shot-Noise-Limited Performance of Dual-Channel Linear Sampling for Ultrafast DPSK Signals,” IEEE J. Quantum Electron. 45(6), 711–719 (2009).
[Crossref]

Roberts, K.

Set, S. Y.

K. Kikuchi and S. Y. Set, “Proposal of Optical-Sampling-Based Constellation Monitor for DP-QPSK Signals,” OECC2013, TuR2-1 (2013).

Spinnler, B.

Sun, H.

Urakawa, N.

K. Igarashi and N. Urakawa, “Constellation Monitor of QPSK Optical Signals Based on Spectrally-sliced Coherent Optical Spectrum Analyzers,” OECC2019, ThC2-4 (2019).

Y. Kawabata, N. Urakawa, K. Kinoshita, and K. Igarashi, “Spectrally Slicing Coherent Optical Spectrum Analyzer for Measuring Complex Field Waveforms of Optical QAM Signals,” OFC2020, W4A.1 (2020).

Wu, K.-T.

IEEE J. Quantum Electron. (1)

K. Okamoto and F. Ito, “Nearly Shot-Noise-Limited Performance of Dual-Channel Linear Sampling for Ultrafast DPSK Signals,” IEEE J. Quantum Electron. 45(6), 711–719 (2009).
[Crossref]

J. Lightwave Technol. (3)

Other (3)

K. Kikuchi and S. Y. Set, “Proposal of Optical-Sampling-Based Constellation Monitor for DP-QPSK Signals,” OECC2013, TuR2-1 (2013).

K. Igarashi and N. Urakawa, “Constellation Monitor of QPSK Optical Signals Based on Spectrally-sliced Coherent Optical Spectrum Analyzers,” OECC2019, ThC2-4 (2019).

Y. Kawabata, N. Urakawa, K. Kinoshita, and K. Igarashi, “Spectrally Slicing Coherent Optical Spectrum Analyzer for Measuring Complex Field Waveforms of Optical QAM Signals,” OFC2020, W4A.1 (2020).

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Figures (13)

Fig. 1.
Fig. 1. Configuration of spectrally slicing-and-synthesizing coherent OSA.
Fig. 2.
Fig. 2. Concept of spectrally slicing-and-synthesizing measurement.
Fig. 3.
Fig. 3. DSP for synthesizing multiple slices.
Fig. 4.
Fig. 4. DSP for suppressing phase noise.
Fig. 5.
Fig. 5. DSP for the frequency offset compensation and slice synthesis.
Fig. 6.
Fig. 6. Simulation model for performance evaluation of our method.
Fig. 7.
Fig. 7. Calculated dependences of symbol fluctuation variance in the presence of timing jitter on (a) the slice number K and (b) variance of timing jitter normalized by the symbol period, τ·B.
Fig. 8.
Fig. 8. Calculated dependences of symbol fluctuation variance due to phase noise on (a) the slice number K and (b) the spectral linewidth δf.
Fig. 9.
Fig. 9. Experimental setup for measuring complex field waveforms of QAM optical signals using our method.
Fig. 10.
Fig. 10. (a) Recovered constellation diagrams of 12.5-Gbaud QPSK signals with the slice number K = 3, 6, 16, 32, 63, and 126. (b) Measured dependence of the symbol fluctuation variance on the slice number K.
Fig. 11.
Fig. 11. Measured constellation diagrams using (a) the broadband self-dye coherent receiver and (b) our method. (c) Our method when optical IQ modulation is not optimized.
Fig. 12.
Fig. 12. Measured spectral waveforms of 16QAM optical signals using (a) our method with the slice number K = 41 and (b) the broadband self-dyne coherent receiver. (c) Real and imaginary parts of temporal waveforms of 16QAM optical signals. Red lines: measured data, Blue lines: AWG data for optical IQ modulation.
Fig. 13.
Fig. 13. Measured constellation diagrams using (a) our method and (b) broadband self-dyne coherent receiver.

Equations (1)

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K W Δ f LO + 1 ,