Abstract

In order to adapt to the dynamics in the future optical networks, we propose a flexible high-order QAM transmitter using a tandem in-phase/quadrature (IQ) modulators to synthesize different high-order quadrature amplitude modulation (QAM) formats, such as 16QAM, 32 or 36QAM and 64QAM. To generate high-order QAMs, an offset-QAM is firstly generated using an IQ modulator driven by electronics with reduced modulation-level, and then mapped to other quadrants through another following IQ modulator configured as a standard quadrature phase-shift keying (QPSK) modulator. All of the embedded sub-Mach-Zehnder modulators are operated in push-pull configurations to avoid introducing excess phase chirp. In contrast with the schemes based on a single IQ modulator driven by multilevel electronics or a highly-integrated parallel modulator, by deploying commercially-available optical modulators and driving electronics with reduced modulation-level, the transmitter complexity in optics and electronics is well-balanced. In the case of generating optical 64QAM, different from another tandem scheme deploying dual-drive IQ modulator driven by independent four binary streams, less phase chirp is observed in our proposed scheme, and comparable implementation penalty is obtained even without applying additional specific compensation algorithm in the coherent receiver. Moreover, thanks to the tandem structure and the deployment of QPSK modulator, the obtained high-order QAM is naturally differentially coded, which is helpful to solve the phase ambiguity at coherent receiver. We experimentally demonstrate the generations of these high-order QAMs including 16QAM, 32/36QAM and 64QAM, and confirm the error-free operations with comparable BER performance to the “electrical” approach based on a single IQ modulator.

© 2013 OSA

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References

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  1. A. H. Gnauck, P. Winzer, A. Konczykowska, F. Jorge, J. Dupuy, M. Riet, G. Charlet, B. Zhu, and D. W. Peckham, “Generation and transmission of 21.4-Gbaud PDM 64-QAM using a high-power DAC driving a single I/Q modulator,” in National Fiber Optic Engineers Conference, OSA Technical Digest (CD) (Optical Society of America, 2012), paper PDPB2.
    [CrossRef]
  2. W. Peng, H. Takahashi, T. Tsuritani, and I. Morita, “DAC-free generation and 320-km transmission of 11.2-GBd PDM-64QAM using a single I/Q modulator,” in European Conference and Exhibition on Optical Communication, OSA Technical Digest (Optical Society of America, 2012), paper We.1.C.3.
  3. A. Sano, T. Kobayashi, K. Ishihara, H. Masuda, S. Yamamoto, K. Mori, E. Yamazaki, E. Yoshida, Y. Miyamoto, T. Yamada, and H. Yamazaki, “240-Gb/s polarization-multiplexed 64-QAM modulation and blind detection using PLC-LN hybrid integrated modulator and digital coherent receiver,” in Proc. of ECOC 2009, Vienna (Austria), Sept. 2009, post-deadline paper PD2.4.
  4. H. Y. Choi, T. Tsuritani, and I. Morita, “Optical transmitter for 320-Gb/s PDM-RZ-16QAM generation using electrical binary drive signals,” Opt. Express20(27), 28772–28778 (2012).
    [CrossRef] [PubMed]
  5. X. Zhou, J. Yu, M.-F. Huang, Y. Shao, T. Wang, P. Magill, M. Cvijetic, L. Nelson, M. Birk, G. Zhang, S. Ten, H. B. Matthew, and S. K. Mishra, “Transmission of 32-Tb/s capacity over 580 km using RZ-shaped PDM-8QAM modulation format and cascaded multimodulus blind equalization algorithm,” J. Lightwave Technol.28(4), 456–465 (2010).
    [CrossRef]
  6. G.-W. Lu, M. Sköld, P. Johannisson, J. Zhao, M. Sjödin, H. Sunnerud, M. Westlund, A. Ellis, and P. A. Andrekson, “40-Gbaud 16-QAM transmitter using tandem IQ modulators with binary driving electronic signals,” Opt. Express18(22), 23062–23069 (2010).
    [CrossRef] [PubMed]
  7. G. Lu, T. Sakamoto, and T. Kawanishi, “Reconfigurable optical 8-ary transmitter based on arbitrary 2-QAM for generating 8PSK and 8QAM,” in Optical Fiber Communication Conference, OSA Technical Digest (Optical Society of America, 2012), paper JTh2A.22.
  8. T. Sakamoto and A. Chiba, “Coherent synthesis of optical multilevel signals by electrooptic digital-to-analog conversion using multiparallel modulator,” IEEE J. Sel. Top. Quantum Electron.16(5), 1140–1149 (2010).
    [CrossRef]
  9. H. Y. Choi, T. Tsuritani, H. Takahashi, W.-R. Peng, and I. Morita, “Generation and detection of 240-Gb/s PDM-64QAM using optical binary synthesizing approach and phase-folded decision-directed equalization,” Opt. Express20(25), 27933–27940 (2012).
    [CrossRef] [PubMed]
  10. X. Zhou, J. Yu, M. Huang, Y. Shao, T. Wang, L. Nelson, P. Magill, M. Birk, P. I. Borel, D. W. Peckham, and R. Lingle, “64-Tb/s (640x107-Gb/s) PDM-36QAM transmission over 320km using both pre- and post-transmission digital equalization,” in National Fiber Optic Engineers Conference, OSA Technical Digest (CD) (Optical Society of America, 2010), paper PDPB9.
  11. X. Zhou, L. E. Nelson, P. Magill, B. Zhu, and D. W. Peckham, “8x450-Gb/s,50-GHz-spaced,PDM-32QAM transmission over 400km and one 50GHz-grid ROADM,” in National Fiber Optic Engineers Conference, OSA Technical Digest (CD) (Optical Society of America, 2011), paper PDPB3.

2012 (2)

2010 (3)

Andrekson, P. A.

Birk, M.

Chiba, A.

T. Sakamoto and A. Chiba, “Coherent synthesis of optical multilevel signals by electrooptic digital-to-analog conversion using multiparallel modulator,” IEEE J. Sel. Top. Quantum Electron.16(5), 1140–1149 (2010).
[CrossRef]

Choi, H. Y.

Cvijetic, M.

Ellis, A.

Huang, M.-F.

Johannisson, P.

Lu, G.-W.

Magill, P.

Matthew, H. B.

Mishra, S. K.

Morita, I.

Nelson, L.

Peng, W.-R.

Sakamoto, T.

T. Sakamoto and A. Chiba, “Coherent synthesis of optical multilevel signals by electrooptic digital-to-analog conversion using multiparallel modulator,” IEEE J. Sel. Top. Quantum Electron.16(5), 1140–1149 (2010).
[CrossRef]

Shao, Y.

Sjödin, M.

Sköld, M.

Sunnerud, H.

Takahashi, H.

Ten, S.

Tsuritani, T.

Wang, T.

Westlund, M.

Yu, J.

Zhang, G.

Zhao, J.

Zhou, X.

IEEE J. Sel. Top. Quantum Electron. (1)

T. Sakamoto and A. Chiba, “Coherent synthesis of optical multilevel signals by electrooptic digital-to-analog conversion using multiparallel modulator,” IEEE J. Sel. Top. Quantum Electron.16(5), 1140–1149 (2010).
[CrossRef]

J. Lightwave Technol. (1)

Opt. Express (3)

Other (6)

A. H. Gnauck, P. Winzer, A. Konczykowska, F. Jorge, J. Dupuy, M. Riet, G. Charlet, B. Zhu, and D. W. Peckham, “Generation and transmission of 21.4-Gbaud PDM 64-QAM using a high-power DAC driving a single I/Q modulator,” in National Fiber Optic Engineers Conference, OSA Technical Digest (CD) (Optical Society of America, 2012), paper PDPB2.
[CrossRef]

W. Peng, H. Takahashi, T. Tsuritani, and I. Morita, “DAC-free generation and 320-km transmission of 11.2-GBd PDM-64QAM using a single I/Q modulator,” in European Conference and Exhibition on Optical Communication, OSA Technical Digest (Optical Society of America, 2012), paper We.1.C.3.

A. Sano, T. Kobayashi, K. Ishihara, H. Masuda, S. Yamamoto, K. Mori, E. Yamazaki, E. Yoshida, Y. Miyamoto, T. Yamada, and H. Yamazaki, “240-Gb/s polarization-multiplexed 64-QAM modulation and blind detection using PLC-LN hybrid integrated modulator and digital coherent receiver,” in Proc. of ECOC 2009, Vienna (Austria), Sept. 2009, post-deadline paper PD2.4.

G. Lu, T. Sakamoto, and T. Kawanishi, “Reconfigurable optical 8-ary transmitter based on arbitrary 2-QAM for generating 8PSK and 8QAM,” in Optical Fiber Communication Conference, OSA Technical Digest (Optical Society of America, 2012), paper JTh2A.22.

X. Zhou, J. Yu, M. Huang, Y. Shao, T. Wang, L. Nelson, P. Magill, M. Birk, P. I. Borel, D. W. Peckham, and R. Lingle, “64-Tb/s (640x107-Gb/s) PDM-36QAM transmission over 320km using both pre- and post-transmission digital equalization,” in National Fiber Optic Engineers Conference, OSA Technical Digest (CD) (Optical Society of America, 2010), paper PDPB9.

X. Zhou, L. E. Nelson, P. Magill, B. Zhu, and D. W. Peckham, “8x450-Gb/s,50-GHz-spaced,PDM-32QAM transmission over 400km and one 50GHz-grid ROADM,” in National Fiber Optic Engineers Conference, OSA Technical Digest (CD) (Optical Society of America, 2011), paper PDPB3.

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Figures (11)

Fig. 1
Fig. 1

Operation principle of the proposed high-order QAM transmitter.

Fig. 2
Fig. 2

64QAM bit to symbol mapping with differential coding from the proposed transmitter.

Fig. 3
Fig. 3

Simulated constellations: (a) offset 16QAM and (b) 64QAM by our proposed scheme, and (c) offset 16QAM and (d) 64 QAM by another tandem scheme driven by binary electronics [9].

Fig. 4
Fig. 4

Experimental setup: (a) our proposed “hybrid”, and (b) “electrical” approach. Inset: optical spectrum of the obtained 64QAM.

Fig. 5
Fig. 5

Measured optical intensity eye-diagrams (top) and corresponding constellations (bottom) for (a) offset-4QAM, (b) standard QPSK, and (c) final 16QAM.

Fig. 6
Fig. 6

Theoretical (solid line) and measured BER curves as a function of OSNR of 16QAM using the proposed “hybrid” scheme (blue squares) and “electrical” scheme based on a single IQ modulator (red circles). Inset: optical intensity eye diagrams of (a) “hybrid” and (b) “electrical” scheme.

Fig. 7
Fig. 7

Measured optical intensity eye diagrams (top) and corresponding constellations (bottom) for (a) offset 8QAM, (b) obtained 32QAM, (c) offset 9QAM, and (c) 36QAM.

Fig. 8
Fig. 8

Theoretical (solid line) and measured BER curves as a function of OSNR of 32QAM using the proposed “hybrid” scheme (blue squares) and “electrical” scheme based on a single IQ modulator (red circles). Inset: optical intensity eye diagrams of (a) “hybrid” and (b) “electrical” scheme.

Fig. 9
Fig. 9

Theoretical (solid line) and measured BER curves as a function of OSNR of 36QAM using the proposed “hybrid” scheme (blue squares) and “electrical” scheme based on a single IQ modulator (red circles). Inset: optical intensity eye diagrams of (a) “hybrid” and (b) “electrical” scheme.

Fig. 10
Fig. 10

Measured optical intensity eye diagrams (top) and corresponding constellations (bottom) for (a) offset 16QAM, and (b) obtained 64QAM.

Fig. 11
Fig. 11

Theoretical (solid line) and measured BER curves as a function of OSNR of 64QAM using the proposed “hybrid” scheme (blue squares). Inset: optical intensity eye diagrams of (a) “hybrid” and (b) “electrical” scheme.

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