## Energy-efficient 0.26-Tb/s coherent-optical OFDM transmission using photonic-integrated all-optical discrete Fourier transform |

Optics Express, Vol. 20, Issue 2, pp. 896-904 (2012)

http://dx.doi.org/10.1364/OE.20.000896

Acrobat PDF (1158 KB)

### Abstract

We propose a novel energy-efficient coherent-optical OFDM transmission scheme based on hybrid optical-electronic signal processing. We demonstrate transmission of a 0.26-Tb/s OFDM superchannel, consisting of 13 x 20-Gb/s polarization-multiplexed QPSK subcarrier channels, over 400-km standard single-mode fiber (SSMF) with BER less than 6.3x10^{−4} using all-optical Fourier transform processing and electronic 7-tap blind digital equalization per subchannel. We further explore long-haul transmission over up to 960 km SSMF and show that the electronic signal processing is capable of compensating chromatic dispersion up to 16,000 ps/nm using only 15 taps per subchannel, even in the presence of strong inter-carrier interference.

© 2012 OSA

## 1. Introduction

1. B. Spinnler, “Equalizer design and complexity for digital coherent receivers,” IEEE J. Sel. Top. Quantum Electron. **16**(5), 1180–1192 (2010). [CrossRef]

5. D. Hillerkuss, R. Schmogrow, T. Schellinger, M. Jordan, M. Winter, G. Huber, T. Vallaitis, R. Bonk, P. Kleinow, F. Frey, M. Roeger, S. Koenig, A. Ludwig, A. Marculescu, J. Li, M. Hoh, M. Dreschmann, J. Meyer, S. Ben Ezra, N. Narkiss, B. Nebendahl, F. Parmigiani, P. Petropoulos, B. Resan, A. Oehler, K. Weingarten, T. Ellermeyer, J. Lutz, M. Moeller, M. Huebner, J. Becker, C. Koos, W. Freude, and J. Leuthold, “26 Tbit s-1 line-rate super-channel transmission utilizing all-optical fast Fourier transform processing,” Nat. Photonics **5**(6), 364–371 (2011). [CrossRef]

*non-coherent*reception of 35-Gb/s (7 x 5 Gb/s NRZ-OOK) data having near-unity spectral efficiency with 1-dB dispersion margin of ~1000 ps/nm [6

6. I. Kang, M. Rasras, X. Liu, S. Chandrasekhar, M. Cappuzzo, L. T. Gomez, Y. F. Chen, L. Buhl, S. Cabot, and J. Jaques, “All-optical OFDM transmission of 7 x 5-Gb/s data over 84-km standard single-mode fiber without dispersion compensation and time gating using a photonic-integrated optical DFT device,” Opt. Express **19**(10), 9111–9117 (2011). [CrossRef] [PubMed]

7. I Kang, S. Chandrasekhar, M. Rasras, X. Liu, M. Cappuzzo, L. Gomez, Y. Chen, L. Buhl, S. Cabot, and J. Jaques, “Transmission of 35-Gb/s all-optical OFDM signal over an all-EDFA 1980-km recirculating loop consisting of SSMF and DCF without using tunable dispersion compensation,” ECOC 2011, Th.11.B.11 (2011).

1. B. Spinnler, “Equalizer design and complexity for digital coherent receivers,” IEEE J. Sel. Top. Quantum Electron. **16**(5), 1180–1192 (2010). [CrossRef]

8. M. Kuschnerov, F. N. Hauske, K. Piyawanno, B. Spinnler, M. S. Alfiad, A. Napoli, and B. Lankl, “DSP for coherent single-carrier receivers,” J. Lightwave Technol. **27**(16), 3614–3622 (2009). [CrossRef]

^{−4}without using any

*optical*dispersion compensation. We achieve this using only 7 taps per subchannel with fractional spacing (1/3 of the symbol period) in the presence of CD and strong ICI from neighboring OFDM subchannels. We further show that CD up to 16,000 ps/nm can be compensated using the hybrid method needing 15 taps per subchannel. We note that we do not employ a time-gating optical modulator to suppress ICI and we only require devices having electronic bandwidth less than 16 GHz, which contribute to additional energy savings.

## 2. Experimental procedure

*E*[11]:where N is the number of subcarriers and

_{n}*τ*(

*=*symbol period

*/N*) is the temporal delay. Thus, all-optical DFT can be implemented using essentially passive components comprising optical delay lines with incremental temporal delay of

*τ*and optical phase shifters for adjusting the optical phases of the delay lines. The simplest example of all-optical DFT was implemented using an asymmetric Mach-Zehnder interferometer (AMZI) for N = 2 [2, 3]. Cascaded AMZIs can be used to demultiplex subchannels when N = 2

^{M}for a positive integer M [5

5. D. Hillerkuss, R. Schmogrow, T. Schellinger, M. Jordan, M. Winter, G. Huber, T. Vallaitis, R. Bonk, P. Kleinow, F. Frey, M. Roeger, S. Koenig, A. Ludwig, A. Marculescu, J. Li, M. Hoh, M. Dreschmann, J. Meyer, S. Ben Ezra, N. Narkiss, B. Nebendahl, F. Parmigiani, P. Petropoulos, B. Resan, A. Oehler, K. Weingarten, T. Ellermeyer, J. Lutz, M. Moeller, M. Huebner, J. Becker, C. Koos, W. Freude, and J. Leuthold, “26 Tbit s-1 line-rate super-channel transmission utilizing all-optical fast Fourier transform processing,” Nat. Photonics **5**(6), 364–371 (2011). [CrossRef]

12. N. Takato, T. Kominato, A. Sugita, K. Jinguji, H. Toba, and M. Kawachi, “Silica-based integrated optic Mach-Zehnder multi/demultiplexer family with channel spacing of 0.01-250 nm,” IEEE J. Sel. Areas Comm. **8**(6), 1120–1127 (1990). [CrossRef]

13. B. H. Verbeek, C. H. Henry, N. A. Olsson, K. J. Orlowsky, R. F. Kazarinov, and B. H. Johnson, “Integrated four-channel Mach-Zehnder multi/demultiplexer fabricated with phosphorous doped SiO2 waveguides on Si,” J. Lightwave Technol. **6**(6), 1011–1015 (1988). [CrossRef]

14. K. Lee, C. T. Thai, and J. K. Rhee, “All optical discrete Fourier transform processor for 100 Gbps OFDM transmission,” Opt. Express **16**(6), 4023–4028 (2008). [CrossRef] [PubMed]

15. A. J. Lowery, “Design of Arrayed-Waveguide Grating Routers for use as optical OFDM demultiplexers,” Opt. Express **18**(13), 14129–14143 (2010). [CrossRef] [PubMed]

16. M. Kang, M. Rasras, M. Dinu, M. Cappuzzo, L. T. Gomez, Y. F. Chen, L. Buhl, S. Cabot, A. Wong-Foy, S. S. Patel, C. R. Giles, N. Dutta, J. Jaques, and A. Piccirilli, “All-optical byte recognition for 40-Gb/s phase-shift-keyed transmission using a planar-lightwave-circuit passive correlator,” IEEE Photon. Technol. Lett. **20**(12), 1024–1026 (2008). [CrossRef]

6. I. Kang, M. Rasras, X. Liu, S. Chandrasekhar, M. Cappuzzo, L. T. Gomez, Y. F. Chen, L. Buhl, S. Cabot, and J. Jaques, “All-optical OFDM transmission of 7 x 5-Gb/s data over 84-km standard single-mode fiber without dispersion compensation and time gating using a photonic-integrated optical DFT device,” Opt. Express **19**(10), 9111–9117 (2011). [CrossRef] [PubMed]

17. S. J. Savory, “Digital coherent optical receivers: algorithms and subsystems,” IEEE J. Sel. Top. Quantum Electron. **16**(5), 1164–1179 (2010). [CrossRef]

## 3. Transmission results

*direct*detection for back-to-back transmission (Fig. 4(a) ) and for 400-km transmission (Fig. 4(b)). With these direct-detected eye diagrams, the impact of ICI is easy to visualize: the b-t-b eye diagram clearly shows the temporal windows of inter-(sub)carrier interference (ICI)-free zone amidst strong ICI elsewhere. However, such an ICI-free zone is not found for the case of 400-km transmission. There are two causes for the degradation of the eye diagram: first, the disappearance of the ICI-suppressed temporal windows is in large part caused by the bit-misalignment of the subchannels due to the group velocity dispersion of the fiber. Note that the temporal bit alignment is the necessary condition for satisfying the orthogonality among the subcarrier channels in OFDM signal reception [11]. In addition, temporal broadening and chirp induced by CD further degrades the signal quality by inter-symbol interference (ISI).

^{−4}after signal processing using 7-tap equalization. Our implementation is distinguished from the previous all-optical OFDM demonstrations in two aspects: first, we do not employ optical dispersion compensation. Precise control of CD/PMD compensation introduces increasing complexity as the modulation speed of the subcarriers is increased. As a result, the complexity, optical loss, and extra power consumption associated with tunable CD/PMD compensation is avoided. Second, no optical gating is necessary. In fact, it would be extremely challenging to implement time-gating to isolate the ICI-free region without precise dispersion compensation as is evident from the eye diagram in Fig. 4(b). Hence, the complications arising from having to use a time-gating modulator per each subchannel, such as clock recovery per subchannel, optical loss, energy consumption for driving the temporal modulators, can be entirely bypassed.

18. E. Ip and J. Kahn, “Digital equalization of chromatic dispersion and polarization mode dispersion,” J. Lightwave Technol. **25**(8), 2033–2043 (2007). [CrossRef]

*single*polarization-diversity coherent receiver. Second, the number of taps required for CD/PMD compensation is much reduced. If we consider transmission of signal with 65-GHz spectral content over 1,000-km SSMF, all-electronic signal processing would require at least ~1,000 taps for frequency domain equalization for fixed CD alone with additional signal processing for dynamic equalization of PMD and time-varying residual CD [1

1. B. Spinnler, “Equalizer design and complexity for digital coherent receivers,” IEEE J. Sel. Top. Quantum Electron. **16**(5), 1180–1192 (2010). [CrossRef]

**16**(5), 1180–1192 (2010). [CrossRef]

19. R. Nagarajan, D. Lambert, M. Kato, V. Lal, G. Goldfarb, J. Rahn, M. Kuntz, J. Pleumeekers, A. Dentai, H.-S. Tsai, R. Malendevich, M. Missey, K.-T. Wu, H. Sun, J. McNicol, J. Tang, J. Zhang, T. Butrie, A. Nilsson, M. Reffle, F. Kish, and D. Welch, *“*10 Channel, 100Gbit/s per channel, dual polarization, coherent QPSK, monolithic InP receiver photonic integrated circuit,” in Proceedings of OFC/NFOEC 2011, post-deadline paper OML7 (2011*).*

## 4. Summary

## Acknowledgments

## References and links

1. | B. Spinnler, “Equalizer design and complexity for digital coherent receivers,” IEEE J. Sel. Top. Quantum Electron. |

2. | H. Sanjoh, E. Yamada, and Y. Yoshikuni, “Optical orthogonal frequency division multiplexing using frequency/time domain filtering for high spectral efficency up to 1bit/s/Hz,” in Proceedings of OFC 2002, paper ThD1 (2002). |

3. | H. Sano, H. Masuda, E. Yoshida, T. Kobayashi, E. Yamada, Y. Miyamoto, F. Inuzuka, Y. Hibino, Y. Takatori, K. Hagimoto, T. Yamada, and Y. Sakamaki, “30x100-Gb/s all-optical OFDM transmission over 1300 km SMF with 10 ROADM nodes,” in Proceedings of ECOC 2007, PDS 1.7 (2007). |

4. | K. Takiguchi, T. Kitoh, A. Mori, M. Ogima, and H. Takahashi, “Integrated-optic OFDM demultiplexer using slab star coupler-based optical DFT circuit,” in proceedings of ECOC 2010, PD1.4 (2010). |

5. | D. Hillerkuss, R. Schmogrow, T. Schellinger, M. Jordan, M. Winter, G. Huber, T. Vallaitis, R. Bonk, P. Kleinow, F. Frey, M. Roeger, S. Koenig, A. Ludwig, A. Marculescu, J. Li, M. Hoh, M. Dreschmann, J. Meyer, S. Ben Ezra, N. Narkiss, B. Nebendahl, F. Parmigiani, P. Petropoulos, B. Resan, A. Oehler, K. Weingarten, T. Ellermeyer, J. Lutz, M. Moeller, M. Huebner, J. Becker, C. Koos, W. Freude, and J. Leuthold, “26 Tbit s-1 line-rate super-channel transmission utilizing all-optical fast Fourier transform processing,” Nat. Photonics |

6. | I. Kang, M. Rasras, X. Liu, S. Chandrasekhar, M. Cappuzzo, L. T. Gomez, Y. F. Chen, L. Buhl, S. Cabot, and J. Jaques, “All-optical OFDM transmission of 7 x 5-Gb/s data over 84-km standard single-mode fiber without dispersion compensation and time gating using a photonic-integrated optical DFT device,” Opt. Express |

7. | I Kang, S. Chandrasekhar, M. Rasras, X. Liu, M. Cappuzzo, L. Gomez, Y. Chen, L. Buhl, S. Cabot, and J. Jaques, “Transmission of 35-Gb/s all-optical OFDM signal over an all-EDFA 1980-km recirculating loop consisting of SSMF and DCF without using tunable dispersion compensation,” ECOC 2011, Th.11.B.11 (2011). |

8. | M. Kuschnerov, F. N. Hauske, K. Piyawanno, B. Spinnler, M. S. Alfiad, A. Napoli, and B. Lankl, “DSP for coherent single-carrier receivers,” J. Lightwave Technol. |

9. | S. Chandrasekhar, X. Liu, B. Zhu, and D. W. Pekham, “Transmission of a 1.2-Tb/s 24-Carrier no-guard-interval coherent OFDM superchannel over 7200-km of ultra-large-area fiber,” ECOC '09, PDP 2.6 (2009). |

10. | T. Healy, F. C. Garcia Gunning, A. D. Ellis, and J. D. Bull, “Multi-wavelength source using low drive-voltage amplitude modulators for optical communications,” Opt. Express |

11. | W. Shieh, I. Djordjevic, OFDM for Optical Communications, (Academic Press, 2010). |

12. | N. Takato, T. Kominato, A. Sugita, K. Jinguji, H. Toba, and M. Kawachi, “Silica-based integrated optic Mach-Zehnder multi/demultiplexer family with channel spacing of 0.01-250 nm,” IEEE J. Sel. Areas Comm. |

13. | B. H. Verbeek, C. H. Henry, N. A. Olsson, K. J. Orlowsky, R. F. Kazarinov, and B. H. Johnson, “Integrated four-channel Mach-Zehnder multi/demultiplexer fabricated with phosphorous doped SiO2 waveguides on Si,” J. Lightwave Technol. |

14. | K. Lee, C. T. Thai, and J. K. Rhee, “All optical discrete Fourier transform processor for 100 Gbps OFDM transmission,” Opt. Express |

15. | A. J. Lowery, “Design of Arrayed-Waveguide Grating Routers for use as optical OFDM demultiplexers,” Opt. Express |

16. | M. Kang, M. Rasras, M. Dinu, M. Cappuzzo, L. T. Gomez, Y. F. Chen, L. Buhl, S. Cabot, A. Wong-Foy, S. S. Patel, C. R. Giles, N. Dutta, J. Jaques, and A. Piccirilli, “All-optical byte recognition for 40-Gb/s phase-shift-keyed transmission using a planar-lightwave-circuit passive correlator,” IEEE Photon. Technol. Lett. |

17. | S. J. Savory, “Digital coherent optical receivers: algorithms and subsystems,” IEEE J. Sel. Top. Quantum Electron. |

18. | E. Ip and J. Kahn, “Digital equalization of chromatic dispersion and polarization mode dispersion,” J. Lightwave Technol. |

19. | R. Nagarajan, D. Lambert, M. Kato, V. Lal, G. Goldfarb, J. Rahn, M. Kuntz, J. Pleumeekers, A. Dentai, H.-S. Tsai, R. Malendevich, M. Missey, K.-T. Wu, H. Sun, J. McNicol, J. Tang, J. Zhang, T. Butrie, A. Nilsson, M. Reffle, F. Kish, and D. Welch, |

**OCIS Codes**

(060.0060) Fiber optics and optical communications : Fiber optics and optical communications

(060.1660) Fiber optics and optical communications : Coherent communications

(250.3140) Optoelectronics : Integrated optoelectronic circuits

**ToC Category:**

Fiber Optics and Optical Communications

**History**

Original Manuscript: November 3, 2011

Revised Manuscript: December 3, 2011

Manuscript Accepted: December 4, 2011

Published: January 4, 2012

**Citation**

I. Kang, X. Liu, S. Chandrasekhar, M. Rasras, H. Jung, M. Cappuzzo, L. T. Gomez, Y. F. Chen, L. Buhl, S. Cabot, and J. Jaques, "Energy-efficient 0.26-Tb/s coherent-optical OFDM transmission using photonic-integrated all-optical discrete Fourier transform," Opt. Express **20**, 896-904 (2012)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-2-896

Sort: Year | Journal | Reset

### References

- B. Spinnler, “Equalizer design and complexity for digital coherent receivers,” IEEE J. Sel. Top. Quantum Electron.16(5), 1180–1192 (2010). [CrossRef]
- H. Sanjoh, E. Yamada, and Y. Yoshikuni, “Optical orthogonal frequency division multiplexing using frequency/time domain filtering for high spectral efficency up to 1bit/s/Hz,” in Proceedings of OFC 2002, paper ThD1 (2002).
- H. Sano, H. Masuda, E. Yoshida, T. Kobayashi, E. Yamada, Y. Miyamoto, F. Inuzuka, Y. Hibino, Y. Takatori, K. Hagimoto, T. Yamada, and Y. Sakamaki, “30x100-Gb/s all-optical OFDM transmission over 1300 km SMF with 10 ROADM nodes,” in Proceedings of ECOC 2007, PDS 1.7 (2007).
- K. Takiguchi, T. Kitoh, A. Mori, M. Ogima, and H. Takahashi, “Integrated-optic OFDM demultiplexer using slab star coupler-based optical DFT circuit,” in proceedings of ECOC 2010, PD1.4 (2010).
- D. Hillerkuss, R. Schmogrow, T. Schellinger, M. Jordan, M. Winter, G. Huber, T. Vallaitis, R. Bonk, P. Kleinow, F. Frey, M. Roeger, S. Koenig, A. Ludwig, A. Marculescu, J. Li, M. Hoh, M. Dreschmann, J. Meyer, S. Ben Ezra, N. Narkiss, B. Nebendahl, F. Parmigiani, P. Petropoulos, B. Resan, A. Oehler, K. Weingarten, T. Ellermeyer, J. Lutz, M. Moeller, M. Huebner, J. Becker, C. Koos, W. Freude, and J. Leuthold, “26 Tbit s-1 line-rate super-channel transmission utilizing all-optical fast Fourier transform processing,” Nat. Photonics5(6), 364–371 (2011). [CrossRef]
- I. Kang, M. Rasras, X. Liu, S. Chandrasekhar, M. Cappuzzo, L. T. Gomez, Y. F. Chen, L. Buhl, S. Cabot, and J. Jaques, “All-optical OFDM transmission of 7 x 5-Gb/s data over 84-km standard single-mode fiber without dispersion compensation and time gating using a photonic-integrated optical DFT device,” Opt. Express19(10), 9111–9117 (2011). [CrossRef] [PubMed]
- I Kang, S. Chandrasekhar, M. Rasras, X. Liu, M. Cappuzzo, L. Gomez, Y. Chen, L. Buhl, S. Cabot, and J. Jaques, “Transmission of 35-Gb/s all-optical OFDM signal over an all-EDFA 1980-km recirculating loop consisting of SSMF and DCF without using tunable dispersion compensation,” ECOC 2011, Th.11.B.11 (2011).
- M. Kuschnerov, F. N. Hauske, K. Piyawanno, B. Spinnler, M. S. Alfiad, A. Napoli, and B. Lankl, “DSP for coherent single-carrier receivers,” J. Lightwave Technol.27(16), 3614–3622 (2009). [CrossRef]
- S. Chandrasekhar, X. Liu, B. Zhu, and D. W. Pekham, “Transmission of a 1.2-Tb/s 24-Carrier no-guard-interval coherent OFDM superchannel over 7200-km of ultra-large-area fiber,” ECOC '09, PDP 2.6 (2009).
- T. Healy, F. C. Garcia Gunning, A. D. Ellis, and J. D. Bull, “Multi-wavelength source using low drive-voltage amplitude modulators for optical communications,” Opt. Express15(6), 2981–2986 (2007). [CrossRef] [PubMed]
- W. Shieh, I. Djordjevic, OFDM for Optical Communications, (Academic Press, 2010).
- N. Takato, T. Kominato, A. Sugita, K. Jinguji, H. Toba, and M. Kawachi, “Silica-based integrated optic Mach-Zehnder multi/demultiplexer family with channel spacing of 0.01-250 nm,” IEEE J. Sel. Areas Comm.8(6), 1120–1127 (1990). [CrossRef]
- B. H. Verbeek, C. H. Henry, N. A. Olsson, K. J. Orlowsky, R. F. Kazarinov, and B. H. Johnson, “Integrated four-channel Mach-Zehnder multi/demultiplexer fabricated with phosphorous doped SiO2 waveguides on Si,” J. Lightwave Technol.6(6), 1011–1015 (1988). [CrossRef]
- K. Lee, C. T. Thai, and J. K. Rhee, “All optical discrete Fourier transform processor for 100 Gbps OFDM transmission,” Opt. Express16(6), 4023–4028 (2008). [CrossRef] [PubMed]
- A. J. Lowery, “Design of Arrayed-Waveguide Grating Routers for use as optical OFDM demultiplexers,” Opt. Express18(13), 14129–14143 (2010). [CrossRef] [PubMed]
- M. Kang, M. Rasras, M. Dinu, M. Cappuzzo, L. T. Gomez, Y. F. Chen, L. Buhl, S. Cabot, A. Wong-Foy, S. S. Patel, C. R. Giles, N. Dutta, J. Jaques, and A. Piccirilli, “All-optical byte recognition for 40-Gb/s phase-shift-keyed transmission using a planar-lightwave-circuit passive correlator,” IEEE Photon. Technol. Lett.20(12), 1024–1026 (2008). [CrossRef]
- S. J. Savory, “Digital coherent optical receivers: algorithms and subsystems,” IEEE J. Sel. Top. Quantum Electron.16(5), 1164–1179 (2010). [CrossRef]
- E. Ip and J. Kahn, “Digital equalization of chromatic dispersion and polarization mode dispersion,” J. Lightwave Technol.25(8), 2033–2043 (2007). [CrossRef]
- R. Nagarajan, D. Lambert, M. Kato, V. Lal, G. Goldfarb, J. Rahn, M. Kuntz, J. Pleumeekers, A. Dentai, H.-S. Tsai, R. Malendevich, M. Missey, K.-T. Wu, H. Sun, J. McNicol, J. Tang, J. Zhang, T. Butrie, A. Nilsson, M. Reffle, F. Kish, and D. Welch, “10 Channel, 100Gbit/s per channel, dual polarization, coherent QPSK, monolithic InP receiver photonic integrated circuit,” in Proceedings of OFC/NFOEC 2011, post-deadline paper OML7 (2011).

## Cited By |
Alert me when this paper is cited |

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.

« Previous Article | Next Article »

OSA is a member of CrossRef.