## All-optical OFDM transmitter design using AWGRs and low-bandwidth modulators |

Optics Express, Vol. 19, Issue 17, pp. 15696-15704 (2011)

http://dx.doi.org/10.1364/OE.19.015696

Acrobat PDF (960 KB)

### Abstract

An Arrayed-Waveguide Grating Router (AWGR) can be used as a demultiplexer for an optical OFDM system, as it provides both the serial-to-parallel converter and the optical Fourier transform (FT) in one component. Because an inverse FT is topologically identical to a Fourier transform, the AWGR can also be used as a FT in an OFDM transmitter. In most all-optical OFDM systems the optical modulators are fed with CW tones; however, the subcarriers (SC) will only be perfectly orthogonal if the bandwidth of the data modulators is similar to the total bandwidth of all subcarriers. Using simulations, this paper investigates the reduction in modulator bandwidth that could be achieved if the modulators are placed before an AWGR designed as a FT. This arrangement also allows the complex (IQ) modulators to be replaced with simpler and more-compact phase modulators. We show that these design improvements enable 7.5-GHz bandwidth modulators to be used in a 4 × 10 Gsymbol/s (80 Gbit/s) per polarization per wavelength system.

© 2011 OSA

## 1. Introduction

2. L. B. Du and A. J. Lowery, “Optimizing the subcarrier granularity of coherent optical communications systems,” Opt. Express **19**(9), 8079–8084 (2011). [CrossRef] [PubMed]

1. A. Sano, E. Yamada, H. Masuda, E. Yamazaki, T. Kobayashi, E. Yoshida, Y. Miyamoto, R. Kudo, K. Ishihara, and Y. Takatori, “No-guard-interval coherent optical OFDM for 100-Gb/s long-haul WDM transmission,” J. Lightwave Technol. **27**(16), 3705–3713 (2009). [CrossRef]

4. D. Hillerkuss, T. Schellinger, R. Schmogrow, M. Winter, T. Vallaitis, R. Bonk, A. Marculescu, J. Li, M. Dreschmann, J. Meyer, S. Ben Ezra, N. Narkiss, B. Nebendahl, F. Parmigiani, P. Petropoulos, B. Resan, K. Weingarten, T. Ellermeyer, J. Lutz, M. Moller, M. Huebner, J. Becker, C. Koos, W. Freude, and J. Leuthold, “Single source optical OFDM transmitter and optical FFT receiver demonstrated at line rates of 5.4 and 10.8 Tbit/s,” in *Conference on Optical Fiber Communication (OFC)* (San Diego, CA, 2010), paper PDPC1.

5. A. J. Lowery, “Design of arrayed-waveguide grating routers for use as optical OFDM demultiplexers,” Opt. Express **18**(13), 14129–14143 (2010). [CrossRef] [PubMed]

6. S. Chandrasekhar and X. Liu, “Experimental investigation on the performance of closely spaced multi-carrier PDM-QPSK with digital coherent detection,” Opt. Express **17**(24), 21350–21361 (2009). [CrossRef] [PubMed]

*T*. This means that the pulses from the AWGR into a given modulator must linearly increase or decrease in phase, with respect to the phase of the centre wavelength of the MLL, at a rate of (2π

_{symbol}*m/T*), where

_{symbol}*m*is an integer denoting an output of the AWGR. As shown in Fig. 1 Scheme 1, the subsequent modulation must not destroy this linear increase, that is, it must add the same phase shift (

*Δθ*) to each pulse within with a single OFDM symbol. This constraint means that the modulators must change their phase rapidly between the OFDM symbols, after the last pulse of one symbol and before the first pulse of the next [5

5. A. J. Lowery, “Design of arrayed-waveguide grating routers for use as optical OFDM demultiplexers,” Opt. Express **18**(13), 14129–14143 (2010). [CrossRef] [PubMed]

8. E. Yamada, A. Sano, H. Masuda, E. Yamazaki, T. Kobayashi, E. Yoshida, K. Yonenaga, Y. Miyamoto, K. Ishihara, Y. Takatori, T. Yamada, and H. Yamazaki, “1 Tbit/s (111 Gbit/s/ch x 10 ch) no-guard-interval CO-OFDM transmission over 2100 km DSF,” Electron. Lett. **44**(24), 1417–1418 (2008). [CrossRef]

9. E. Yamada, A. Sano, H. Masuda, T. Kobayashi, E. Yoshida, Y. Miyamoto, Y. Hibino, K. Ishihara, Y. Takatori, K. Okada, K. Hagimoto, T. Yamada, and H. Yamazaki, “Novel no-guard-interval PDM CO-OFDM transmission in 4.1 Tb/s (55x88.8-Gb/s) DWDM link over 800 km SMF including 50-GHz spaced ROADM nodes,” in *Conference on Optical Fiber Communication (OFC)* (San Diego, CA, 2008), paper PDP8.

10. Z. Wang, K. S. Kravtsov, Y.-K. Huang, and P. R. Prucnal, “Optical FFT/IFFT circuit realization using arrayed waveguide gratings and the applications in all-optical OFDM system,” Opt. Express **19**(5), 4501–4512 (2011). [CrossRef] [PubMed]

5. A. J. Lowery, “Design of arrayed-waveguide grating routers for use as optical OFDM demultiplexers,” Opt. Express **18**(13), 14129–14143 (2010). [CrossRef] [PubMed]

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

*et al.*[12

12. Y.-K. Huang, D. Qian, R. E. Saperstein, P. N. Ji, N. Cvijetic, L. Xu, and T. Wang, “Dual-polarization 2x2 IFFT/FFT optical signal processing for 100-Gb/s QPSK-PDM all-optical OFDM,” in *Conference on Optical Fiber Communication (OFC)* (Optical Society of America, San Diego, CA, 2009), paper OTuM4.

*et al.*[10

10. Z. Wang, K. S. Kravtsov, Y.-K. Huang, and P. R. Prucnal, “Optical FFT/IFFT circuit realization using arrayed waveguide gratings and the applications in all-optical OFDM system,” Opt. Express **19**(5), 4501–4512 (2011). [CrossRef] [PubMed]

*et al.*used phase modulators in their implementation of Scheme 2 [12

12. Y.-K. Huang, D. Qian, R. E. Saperstein, P. N. Ji, N. Cvijetic, L. Xu, and T. Wang, “Dual-polarization 2x2 IFFT/FFT optical signal processing for 100-Gb/s QPSK-PDM all-optical OFDM,” in *Conference on Optical Fiber Communication (OFC)* (Optical Society of America, San Diego, CA, 2009), paper OTuM4.

## 2. AWGR design for scheme 2

13. A. J. Lowery and J. Armstrong, “Orthogonal-frequency-division multiplexing for dispersion compensation of long-haul optical systems,” Opt. Express **14**(6), 2079–2084 (2006). [CrossRef] [PubMed]

14. W. Shieh and C. Athaudage, “Coherent optical orthogonal frequency division multiplexing,” Electron. Lett. **42**(10), 587–588 (2006). [CrossRef]

15. K. Takiguchi, T. Kitoh, A. Mori, M. Oguma, and H. Takahashi, “Optical orthogonal frequency division multiplexing demultiplexer using slab star coupler-based optical discrete Fourier transform circuit,” Opt. Lett. **36**(7), 1140–1142 (2011). [CrossRef] [PubMed]

*m*) and the particular output waveguide (

*n*) connected to it. Thus each grating waveguide receives a phase-weighted combination of the outputs of the four modulators, which implements a FT [5

**18**(13), 14129–14143 (2010). [CrossRef] [PubMed]

10. Z. Wang, K. S. Kravtsov, Y.-K. Huang, and P. R. Prucnal, “Optical FFT/IFFT circuit realization using arrayed waveguide gratings and the applications in all-optical OFDM system,” Opt. Express **19**(5), 4501–4512 (2011). [CrossRef] [PubMed]

*sinc*spectrum if the pulses are short enough. The use of eight grating waveguides for a four-subcarrier transmitter is a deliberate design choice, as the free-spectral-range (FSR) of the AWGR will be almost twice as wide as the main lobe of the OFDM spectrum. This means that the spectral images of the OFDM subcarriers will fall well away from the required lobe, so can be removed with conventional optical filters with relatively-wide pass-band to stop-band transitions, as will be shown later by simulation.

## 3. Simulation setup

6. S. Chandrasekhar and X. Liu, “Experimental investigation on the performance of closely spaced multi-carrier PDM-QPSK with digital coherent detection,” Opt. Express **17**(24), 21350–21361 (2009). [CrossRef] [PubMed]

**18**(13), 14129–14143 (2010). [CrossRef] [PubMed]

*Q*, was assessed from the Cartesian mean and the variance of 1024 constellation points [16

16. A. J. Lowery, L. B. Du, and J. Armstrong, “Performance of optical OFDM in ultralong-haul WDM lightwave systems,” J. Lightwave Technol. **25**(1), 131–138 (2007). [CrossRef]

*Q*of 9.8 dB translates to a bit error ratio of 10

^{−3}, assuming Gaussian statistics.

## 4. Simulation results

### 4.1 System using an AWGR after the complex optical modulators (scheme 2)

*Q*of the best (Subcarrier 2) and worst (Subcarrier 4) subcarriers in a noiseless system, versus the electrical bandwidth of the complex optical modulators for the four pulse widths. Because these are back to back results, some margin is required for other systems impairments including optical amplifier noise; thus, the back-to-back signal quality should be at least 15 dB for the transmitter to be useful. The shortest MLL pulses give the best performance at all bandwidths, for both the best (2nd) and worst (4th) SCs. Thus, 7.5-GHz bandwidth modulators could be used to give a

*Q*more than 19 dB.

*Q*becomes limited by ICI, because the 50 GHz optical bandpass filter cuts the tails of the subcarrier’s spectra, so the subcarriers are no longer orthogonal. This was first confirmed by simulating a single carrier to remove the possibility of ICI: the

*Q*increased to over 30 dB. The

*Q*was also increased to over 30-dB with all subcarriers active by widening the bandwidth of the optical filter to 80 GHz and using 5 ps pulses. For longer MLL pulses, the 4th subcarrier receives less power due to the limited spectral width of the MLL, and so is most affected by ICI from its neighbors, thus has the lowest signal quality. This was confirmed by monitoring the

*Q*of the 1st subcarrier, which is higher than the 4th, because it is closer to the centre frequency of the MLL.

### 4.2 Placing the AWGR before the optical modulators (scheme 1)

*sinc-*spectrum, if the transitions are short. The results show that the modulators require bandwidths of at least 15 GHz to approach an acceptable performance. This is equivalent to 30-GHz of optical modulation bandwidth, because the modulators modulate both lower- and upper-sidebands onto their optical inputs. Subcarrier 4 also has a higher penalty than in Scheme 2, even for the shorter pulsewdths, limiting its maximum

*Q*to 2-dB less than in Scheme 2.

### 4.3 Use of phase modulators to replace the complex (IQ) modulators (scheme 2)

*et al.*[12

12. Y.-K. Huang, D. Qian, R. E. Saperstein, P. N. Ji, N. Cvijetic, L. Xu, and T. Wang, “Dual-polarization 2x2 IFFT/FFT optical signal processing for 100-Gb/s QPSK-PDM all-optical OFDM,” in *Conference on Optical Fiber Communication (OFC)* (Optical Society of America, San Diego, CA, 2009), paper OTuM4.

## 5. Discussion

19. A. D. Ellis and F. C. G. Gunning, “Spectral density enhancement using coherent WDM,” IEEE Photon. Technol. Lett. **17**(2), 504–506 (2005). [CrossRef]

20. P. Frascella, N. Mac Suibhne, F. C. G. Gunning, S. K. Ibrahim, P. Gunning, and A. D. Ellis, “Unrepeatered field transmission of 2 Tbit/s multi-banded coherent WDM over 124 km of installed SMF,” Opt. Express **18**(24), 24745–24752 (2010). [CrossRef] [PubMed]

21. H. Masuda, E. Yamazaki, A. Sano, T. Yoshimatsu, T. Kobayashi, E. Yoshida, Y. Miyamoto, S. Matsuoka, Y. Takatori, M. Mizoguchi, K. Okada, K. Hagimoto, T. Yamada, and S. Kamei, “13.5-Tb/s (135 x 111-Gb/s/ch) no-guard-interval coherent OFDM transmission over 6,248 km using SNR maximized second-order DRA in the extended L-band,” in in *Conference on Optical Fiber Communication (OFC)* (San Diego, CA, 2009), paper PDPB5.

22. S. K. Ibrahim, J. Zhao, F. C. Garcia Gunning, P. Frascella, F. H. Peters, and A. D. Ellis, “Towards a practical implementation of coherent WDM: analytical, numerical and experimental studies,” IEEE Photon. J. **2**(5), 833–847 (2010). [CrossRef]

## 6. Conclusion

## Acknowledgments

## References and links

1. | A. Sano, E. Yamada, H. Masuda, E. Yamazaki, T. Kobayashi, E. Yoshida, Y. Miyamoto, R. Kudo, K. Ishihara, and Y. Takatori, “No-guard-interval coherent optical OFDM for 100-Gb/s long-haul WDM transmission,” J. Lightwave Technol. |

2. | L. B. Du and A. J. Lowery, “Optimizing the subcarrier granularity of coherent optical communications systems,” Opt. Express |

3. | A. D. Ellis, A. K. Mishra, P. Frascella, I. Tomkos, S. K. Ibrahim, J. Zhao, and F. C. G. Gunning, “Adaptive modulation schemes,” in |

4. | D. Hillerkuss, T. Schellinger, R. Schmogrow, M. Winter, T. Vallaitis, R. Bonk, A. Marculescu, J. Li, M. Dreschmann, J. Meyer, S. Ben Ezra, N. Narkiss, B. Nebendahl, F. Parmigiani, P. Petropoulos, B. Resan, K. Weingarten, T. Ellermeyer, J. Lutz, M. Moller, M. Huebner, J. Becker, C. Koos, W. Freude, and J. Leuthold, “Single source optical OFDM transmitter and optical FFT receiver demonstrated at line rates of 5.4 and 10.8 Tbit/s,” in |

5. | A. J. Lowery, “Design of arrayed-waveguide grating routers for use as optical OFDM demultiplexers,” Opt. Express |

6. | S. Chandrasekhar and X. Liu, “Experimental investigation on the performance of closely spaced multi-carrier PDM-QPSK with digital coherent detection,” Opt. Express |

7. | J. G. Proakis and M. Salehi, |

8. | E. Yamada, A. Sano, H. Masuda, E. Yamazaki, T. Kobayashi, E. Yoshida, K. Yonenaga, Y. Miyamoto, K. Ishihara, Y. Takatori, T. Yamada, and H. Yamazaki, “1 Tbit/s (111 Gbit/s/ch x 10 ch) no-guard-interval CO-OFDM transmission over 2100 km DSF,” Electron. Lett. |

9. | E. Yamada, A. Sano, H. Masuda, T. Kobayashi, E. Yoshida, Y. Miyamoto, Y. Hibino, K. Ishihara, Y. Takatori, K. Okada, K. Hagimoto, T. Yamada, and H. Yamazaki, “Novel no-guard-interval PDM CO-OFDM transmission in 4.1 Tb/s (55x88.8-Gb/s) DWDM link over 800 km SMF including 50-GHz spaced ROADM nodes,” in |

10. | Z. Wang, K. S. Kravtsov, Y.-K. Huang, and P. R. Prucnal, “Optical FFT/IFFT circuit realization using arrayed waveguide gratings and the applications in all-optical OFDM system,” Opt. Express |

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

12. | Y.-K. Huang, D. Qian, R. E. Saperstein, P. N. Ji, N. Cvijetic, L. Xu, and T. Wang, “Dual-polarization 2x2 IFFT/FFT optical signal processing for 100-Gb/s QPSK-PDM all-optical OFDM,” in |

13. | A. J. Lowery and J. Armstrong, “Orthogonal-frequency-division multiplexing for dispersion compensation of long-haul optical systems,” Opt. Express |

14. | W. Shieh and C. Athaudage, “Coherent optical orthogonal frequency division multiplexing,” Electron. Lett. |

15. | K. Takiguchi, T. Kitoh, A. Mori, M. Oguma, and H. Takahashi, “Optical orthogonal frequency division multiplexing demultiplexer using slab star coupler-based optical discrete Fourier transform circuit,” Opt. Lett. |

16. | A. J. Lowery, L. B. Du, and J. Armstrong, “Performance of optical OFDM in ultralong-haul WDM lightwave systems,” J. Lightwave Technol. |

17. | D. Qian, M.-F. Huang, E. Ip, Y.-K. Huang, Y. Shao, J. Hu, and T. Wang, “101.7-Tb/s (370 x 294-Gb/s) PDM-128QAM-OFDM transmission over 3 x 55-km SSMF using pilot-based phase noise mitigation,” in |

18. | 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 line-rate super-channel transmission utilizing all-optical fast Fourier transform processing,” Nat. Photonics |

19. | A. D. Ellis and F. C. G. Gunning, “Spectral density enhancement using coherent WDM,” IEEE Photon. Technol. Lett. |

20. | P. Frascella, N. Mac Suibhne, F. C. G. Gunning, S. K. Ibrahim, P. Gunning, and A. D. Ellis, “Unrepeatered field transmission of 2 Tbit/s multi-banded coherent WDM over 124 km of installed SMF,” Opt. Express |

21. | H. Masuda, E. Yamazaki, A. Sano, T. Yoshimatsu, T. Kobayashi, E. Yoshida, Y. Miyamoto, S. Matsuoka, Y. Takatori, M. Mizoguchi, K. Okada, K. Hagimoto, T. Yamada, and S. Kamei, “13.5-Tb/s (135 x 111-Gb/s/ch) no-guard-interval coherent OFDM transmission over 6,248 km using SNR maximized second-order DRA in the extended L-band,” in in |

22. | S. K. Ibrahim, J. Zhao, F. C. Garcia Gunning, P. Frascella, F. H. Peters, and A. D. Ellis, “Towards a practical implementation of coherent WDM: analytical, numerical and experimental studies,” IEEE Photon. J. |

**OCIS Codes**

(050.1950) Diffraction and gratings : Diffraction gratings

(060.1660) Fiber optics and optical communications : Coherent communications

(060.2330) Fiber optics and optical communications : Fiber optics communications

(060.4080) Fiber optics and optical communications : Modulation

(060.4230) Fiber optics and optical communications : Multiplexing

(080.1238) Geometric optics : Array waveguide devices

**ToC Category:**

Fiber Optics and Optical Communications

**History**

Original Manuscript: May 24, 2011

Revised Manuscript: June 22, 2011

Manuscript Accepted: July 12, 2011

Published: August 1, 2011

**Citation**

Arthur James Lowery and Liang Du, "All-optical OFDM transmitter design using AWGRs and low-bandwidth modulators," Opt. Express **19**, 15696-15704 (2011)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-17-15696

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### References

- A. Sano, E. Yamada, H. Masuda, E. Yamazaki, T. Kobayashi, E. Yoshida, Y. Miyamoto, R. Kudo, K. Ishihara, and Y. Takatori, “No-guard-interval coherent optical OFDM for 100-Gb/s long-haul WDM transmission,” J. Lightwave Technol. 27(16), 3705–3713 (2009). [CrossRef]
- L. B. Du and A. J. Lowery, “Optimizing the subcarrier granularity of coherent optical communications systems,” Opt. Express 19(9), 8079–8084 (2011). [CrossRef] [PubMed]
- A. D. Ellis, A. K. Mishra, P. Frascella, I. Tomkos, S. K. Ibrahim, J. Zhao, and F. C. G. Gunning, “Adaptive modulation schemes,” in Summer Topical Meeting, 2009, LEOSST '09, IEEE/LEOS (2009), pp. 141–142.
- D. Hillerkuss, T. Schellinger, R. Schmogrow, M. Winter, T. Vallaitis, R. Bonk, A. Marculescu, J. Li, M. Dreschmann, J. Meyer, S. Ben Ezra, N. Narkiss, B. Nebendahl, F. Parmigiani, P. Petropoulos, B. Resan, K. Weingarten, T. Ellermeyer, J. Lutz, M. Moller, M. Huebner, J. Becker, C. Koos, W. Freude, and J. Leuthold, “Single source optical OFDM transmitter and optical FFT receiver demonstrated at line rates of 5.4 and 10.8 Tbit/s,” in Conference on Optical Fiber Communication (OFC) (San Diego, CA, 2010), paper PDPC1.
- A. J. Lowery, “Design of arrayed-waveguide grating routers for use as optical OFDM demultiplexers,” Opt. Express 18(13), 14129–14143 (2010). [CrossRef] [PubMed]
- S. Chandrasekhar and X. Liu, “Experimental investigation on the performance of closely spaced multi-carrier PDM-QPSK with digital coherent detection,” Opt. Express 17(24), 21350–21361 (2009). [CrossRef] [PubMed]
- J. G. Proakis and M. Salehi, Essentials of Communications Systems Engineering (Prentice Hall, 2005).
- E. Yamada, A. Sano, H. Masuda, E. Yamazaki, T. Kobayashi, E. Yoshida, K. Yonenaga, Y. Miyamoto, K. Ishihara, Y. Takatori, T. Yamada, and H. Yamazaki, “1 Tbit/s (111 Gbit/s/ch x 10 ch) no-guard-interval CO-OFDM transmission over 2100 km DSF,” Electron. Lett. 44(24), 1417–1418 (2008). [CrossRef]
- E. Yamada, A. Sano, H. Masuda, T. Kobayashi, E. Yoshida, Y. Miyamoto, Y. Hibino, K. Ishihara, Y. Takatori, K. Okada, K. Hagimoto, T. Yamada, and H. Yamazaki, “Novel no-guard-interval PDM CO-OFDM transmission in 4.1 Tb/s (55x88.8-Gb/s) DWDM link over 800 km SMF including 50-GHz spaced ROADM nodes,” in Conference on Optical Fiber Communication (OFC) (San Diego, CA, 2008), paper PDP8.
- Z. Wang, K. S. Kravtsov, Y.-K. Huang, and P. R. Prucnal, “Optical FFT/IFFT circuit realization using arrayed waveguide gratings and the applications in all-optical OFDM system,” Opt. Express 19(5), 4501–4512 (2011). [CrossRef] [PubMed]
- K. Lee, C. T. D. Thai, and J.-K. K. Rhee, “All optical discrete Fourier transform processor for 100 Gbps OFDM transmission,” Opt. Express 16(6), 4023–4028 (2008). [CrossRef] [PubMed]
- Y.-K. Huang, D. Qian, R. E. Saperstein, P. N. Ji, N. Cvijetic, L. Xu, and T. Wang, “Dual-polarization 2x2 IFFT/FFT optical signal processing for 100-Gb/s QPSK-PDM all-optical OFDM,” in Conference on Optical Fiber Communication (OFC) (Optical Society of America, San Diego, CA, 2009), paper OTuM4.
- A. J. Lowery and J. Armstrong, “Orthogonal-frequency-division multiplexing for dispersion compensation of long-haul optical systems,” Opt. Express 14(6), 2079–2084 (2006). [CrossRef] [PubMed]
- W. Shieh and C. Athaudage, “Coherent optical orthogonal frequency division multiplexing,” Electron. Lett. 42(10), 587–588 (2006). [CrossRef]
- K. Takiguchi, T. Kitoh, A. Mori, M. Oguma, and H. Takahashi, “Optical orthogonal frequency division multiplexing demultiplexer using slab star coupler-based optical discrete Fourier transform circuit,” Opt. Lett. 36(7), 1140–1142 (2011). [CrossRef] [PubMed]
- A. J. Lowery, L. B. Du, and J. Armstrong, “Performance of optical OFDM in ultralong-haul WDM lightwave systems,” J. Lightwave Technol. 25(1), 131–138 (2007). [CrossRef]
- D. Qian, M.-F. Huang, E. Ip, Y.-K. Huang, Y. Shao, J. Hu, and T. Wang, “101.7-Tb/s (370 x 294-Gb/s) PDM-128QAM-OFDM transmission over 3 x 55-km SSMF using pilot-based phase noise mitigation,” in Conference on Optical Fiber Communication (OFC) (Los Angeles, CA, 2011), paper PDPB5.
- 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 line-rate super-channel transmission utilizing all-optical fast Fourier transform processing,” Nat. Photonics 5(6), 364–371 (2011). [CrossRef]
- A. D. Ellis and F. C. G. Gunning, “Spectral density enhancement using coherent WDM,” IEEE Photon. Technol. Lett. 17(2), 504–506 (2005). [CrossRef]
- P. Frascella, N. Mac Suibhne, F. C. G. Gunning, S. K. Ibrahim, P. Gunning, and A. D. Ellis, “Unrepeatered field transmission of 2 Tbit/s multi-banded coherent WDM over 124 km of installed SMF,” Opt. Express 18(24), 24745–24752 (2010). [CrossRef] [PubMed]
- H. Masuda, E. Yamazaki, A. Sano, T. Yoshimatsu, T. Kobayashi, E. Yoshida, Y. Miyamoto, S. Matsuoka, Y. Takatori, M. Mizoguchi, K. Okada, K. Hagimoto, T. Yamada, and S. Kamei, “13.5-Tb/s (135 x 111-Gb/s/ch) no-guard-interval coherent OFDM transmission over 6,248 km using SNR maximized second-order DRA in the extended L-band,” in in Conference on Optical Fiber Communication (OFC) (San Diego, CA, 2009), paper PDPB5.
- S. K. Ibrahim, J. Zhao, F. C. Garcia Gunning, P. Frascella, F. H. Peters, and A. D. Ellis, “Towards a practical implementation of coherent WDM: analytical, numerical and experimental studies,” IEEE Photon. J. 2(5), 833–847 (2010). [CrossRef]

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