## Generation of coherent and frequency-lock multi-carriers using cascaded phase modulators and recirculating frequency shifter for Tb/s optical communication |

Optics Express, Vol. 19, Issue 14, pp. 12891-12902 (2011)

http://dx.doi.org/10.1364/OE.19.012891

Acrobat PDF (1414 KB)

### Abstract

We investigate to generate coherent and frequency-lock optical multi-carriers by using cascaded phase modulators and recirculating frequency shifter (RFS) based on an EDFA loop. The phase and amplitude relation of RF signals on two cascaded phase modulators and the impact of EDFA gain are investigated. Experimental results are in good agreement with the theoretical analysis. The performance of 113 coherent and frequency-lock subcarriers with tone-to-noise ratio larger than 26dB and amplitude difference of 5dB obtained after a tilt filter covering totally 22.6nm shows that this scheme is a promising technique for the coming Tb/s optical communication.

© 2011 OSA

## 1. Introduction

1. T. Sakamoto, T. Yamamoto, K. Kurokawa, and S. Tomita, “DWDM transmission in O-band over 24 km PCF using optical frequency comb based multicarrier source,” Electron. Lett. **45**(16), 850–851 (2009). [CrossRef]

5. J. Yu, X. Zhou, M.-F. Huang, D. Qian, P. N. Ji, T. Wang, and P. Magill, “400Gb/s (4 x 100Gb/s) orthogonal PDM-RZ-QPSK DWDM signal transmission over 1040km SMF-28,” Opt. Express **17**(20), 17928–17933 (2009). [CrossRef] [PubMed]

5. J. Yu, X. Zhou, M.-F. Huang, D. Qian, P. N. Ji, T. Wang, and P. Magill, “400Gb/s (4 x 100Gb/s) orthogonal PDM-RZ-QPSK DWDM signal transmission over 1040km SMF-28,” Opt. Express **17**(20), 17928–17933 (2009). [CrossRef] [PubMed]

7. J. Yu, “1.2 Tbit/s orthogonal PDM-RZ-QPSK DWDM signal transmission over 1040 km SMF-28,” Electron. Lett. **46**(11), 775–777 (2010). [CrossRef]

8. B. Zhu, X. Liu, S. Chandrasekhar, D. W. Peckham, and R. Lingle, “Ultra-long-haul transmission of 1.2-Tb/s multicarrier no-guard-interval CO-OFDM superchannel using ultra-large-area fiber,” IEEE Photon. Technol. Lett. **22**(11), 826–828 (2010). [CrossRef]

11. 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 × 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,” OFC. PDPB5, (2009).

1. T. Sakamoto, T. Yamamoto, K. Kurokawa, and S. Tomita, “DWDM transmission in O-band over 24 km PCF using optical frequency comb based multicarrier source,” Electron. Lett. **45**(16), 850–851 (2009). [CrossRef]

5. J. Yu, X. Zhou, M.-F. Huang, D. Qian, P. N. Ji, T. Wang, and P. Magill, “400Gb/s (4 x 100Gb/s) orthogonal PDM-RZ-QPSK DWDM signal transmission over 1040km SMF-28,” Opt. Express **17**(20), 17928–17933 (2009). [CrossRef] [PubMed]

7. J. Yu, “1.2 Tbit/s orthogonal PDM-RZ-QPSK DWDM signal transmission over 1040 km SMF-28,” Electron. Lett. **46**(11), 775–777 (2010). [CrossRef]

12. 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 **15**(6), 2981–2986 (2007). [CrossRef] [PubMed]

3. Y. Ma, Q. Yang, Y. Tang, S. Chen, and W. Shieh, “1-Tb/s single-channel coherent optical OFDM transmission over 600-km SSMF fiber with subwavelength bandwidth access,” Opt. Express **17**(11), 9421–9427 (2009). [CrossRef] [PubMed]

13. J. Li, X. Li, X. Zhang, F. Tian, and L. Xi, “Analysis of the stability and optimizing operation of the single-side-band modulator based on re-circulating frequency shifter used for the T-bit/s optical communication transmission,” Opt. Express **18**(17), 17597–17609 (2010). [CrossRef] [PubMed]

14. A. Bellemare, M. Karasek, M. Rochette, S. LRochelle, and M. Tetu, “Room temperature multifrequency erbium-doped fiber lasers anchored on the ITU frequency grid,” J. Lightwave Technol. **18**(6), 825–831 (2000). [CrossRef]

17. M. A. Mirza and G. Stewart, “Multiwavelength operation of erbium-doped fiber lasers by period filtering and phase modulation,” J. Lightwave Technol. **27**(8), 1034–1044 (2009). [CrossRef]

18. 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. Möller, M. Hübner, 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 10.8Tbit/s,” OFC 2010: PDPC1.

7. J. Yu, “1.2 Tbit/s orthogonal PDM-RZ-QPSK DWDM signal transmission over 1040 km SMF-28,” Electron. Lett. **46**(11), 775–777 (2010). [CrossRef]

**46**(11), 775–777 (2010). [CrossRef]

3. Y. Ma, Q. Yang, Y. Tang, S. Chen, and W. Shieh, “1-Tb/s single-channel coherent optical OFDM transmission over 600-km SSMF fiber with subwavelength bandwidth access,” Opt. Express **17**(11), 9421–9427 (2009). [CrossRef] [PubMed]

13. J. Li, X. Li, X. Zhang, F. Tian, and L. Xi, “Analysis of the stability and optimizing operation of the single-side-band modulator based on re-circulating frequency shifter used for the T-bit/s optical communication transmission,” Opt. Express **18**(17), 17597–17609 (2010). [CrossRef] [PubMed]

13. J. Li, X. Li, X. Zhang, F. Tian, and L. Xi, “Analysis of the stability and optimizing operation of the single-side-band modulator based on re-circulating frequency shifter used for the T-bit/s optical communication transmission,” Opt. Express **18**(17), 17597–17609 (2010). [CrossRef] [PubMed]

14. A. Bellemare, M. Karasek, M. Rochette, S. LRochelle, and M. Tetu, “Room temperature multifrequency erbium-doped fiber lasers anchored on the ITU frequency grid,” J. Lightwave Technol. **18**(6), 825–831 (2000). [CrossRef]

17. M. A. Mirza and G. Stewart, “Multiwavelength operation of erbium-doped fiber lasers by period filtering and phase modulation,” J. Lightwave Technol. **27**(8), 1034–1044 (2009). [CrossRef]

## 2. Principle of multi-carriers generation and theoretical investigation

### 2.1 Analysis of two cascade phase modulators

*n*,

*R*is the modulation index representing the rate of RF signal amplitude to the half-wave voltage

*n*th harmonics optical subcarrier

*R*increases the power transferred to the higher order subcarriers, and increases the number of higher order subcarriers. Also, the flatness of generated subcarriers varies with

*R*. In this way, the maximum number of subcarriers is depended on the modulation index

*R*. Assuming the total number of subcarriers generated is 2

*m + 1*, Eq. (3) can be expressed as followsAccording to the Bessel expansion of the output of Phase modulators, the power of high orders subcarriers drop sharply. As described in Eq. (4), generated subcarriers between the two m

^{th}high order subcarriers are counted.

*R*and the phase deviation on the number of generated subcarriers when

*π*. In this case, the subcarriers amount decreases sharply. It can be explained well with Eq. (6). The number of generated subcarriers mentioned in Fig. 2 and Fig. 3 indicates the amount of subcarriers between the two high order harmonic subcarriers which are 3dB power decline to the maximum power. Assuming the modulation index of two cascaded phase modulator is the same

*R*, the combined modulation index is expressed aswhich is a cosine function of

*π*(−0.45

*π*to 0.45

*π*) as shown in Fig. 3(a). The more detailed variation of calculated power mean square deviation (MSD) representing flatness for generated subcarriers with the modulation index R and phase deviation

*R*which is blue zone in Fig. 3 (b). When

*R*is around 2.1 and phase deviation is around 0.15

*π*, more than 22 subcarriers can be obtained and the tolerance for phase deviation can be more than 0.1

*π*.

### 2.2 The principle of EDFA loop for RFS

14. A. Bellemare, M. Karasek, M. Rochette, S. LRochelle, and M. Tetu, “Room temperature multifrequency erbium-doped fiber lasers anchored on the ITU frequency grid,” J. Lightwave Technol. **18**(6), 825–831 (2000). [CrossRef]

17. M. A. Mirza and G. Stewart, “Multiwavelength operation of erbium-doped fiber lasers by period filtering and phase modulation,” J. Lightwave Technol. **27**(8), 1034–1044 (2009). [CrossRef]

- • There is no comb or period filter in the EDFA loop in our scheme. In [14
**18**(6), 825–831 (2000). [CrossRef]**27**(8), 1034–1044 (2009). [CrossRef] - • In [14
**18**(6), 825–831 (2000). [CrossRef]**27**(8), 1034–1044 (2009). [CrossRef] - • There is no optical injection in [14
**18**(6), 825–831 (2000). [CrossRef]**27**(8), 1034–1044 (2009). [CrossRef]

## 3. Experimental results

*π*where the two RF drive signals are opposite in phase and no subcarriers are generated in 3 dB. It is worth noting that the flatness of generated subcarriers also changes with the phase deviation. The results are in good agreement with the analysis in section 2.1 with Fig. 2 and Fig. 3.

## 4. Conclusion

## Acknowledgments

## References and links

1. | T. Sakamoto, T. Yamamoto, K. Kurokawa, and S. Tomita, “DWDM transmission in O-band over 24 km PCF using optical frequency comb based multicarrier source,” Electron. Lett. |

2. | S. Liu, T. T. Ng, D. J. Richardson, and P. Petropoulos. “An optical frequency comb generator as a broadband pulse source,” OFC. OThG7, (2009). |

3. | Y. Ma, Q. Yang, Y. Tang, S. Chen, and W. Shieh, “1-Tb/s single-channel coherent optical OFDM transmission over 600-km SSMF fiber with subwavelength bandwidth access,” Opt. Express |

4. | S. Chandrasekhar, X. Liu, B. Zhu, and D. Peckham, “Transmission of a 1.2-Tb/s 24-carrier no-guard-interval coherent OFDM superchannel over 7200-km of ultra-large-area fiber,” ECOC. PD2.6, (2009). |

5. | J. Yu, X. Zhou, M.-F. Huang, D. Qian, P. N. Ji, T. Wang, and P. Magill, “400Gb/s (4 x 100Gb/s) orthogonal PDM-RZ-QPSK DWDM signal transmission over 1040km SMF-28,” Opt. Express |

6. | areG. Gavioli, E. Torrengo, G. Bosco, A. Carena, S. J. Savory, F. Forghieri, and P. Poggiolini, “Ultra-narrow-spacing 10-channel 1.12 Tb/s D-wdm long-haul transmission over uncompensated SMF and NZDSF,” IEEE Photon. Technol. Lett. |

7. | J. Yu, “1.2 Tbit/s orthogonal PDM-RZ-QPSK DWDM signal transmission over 1040 km SMF-28,” Electron. Lett. |

8. | B. Zhu, X. Liu, S. Chandrasekhar, D. W. Peckham, and R. Lingle, “Ultra-long-haul transmission of 1.2-Tb/s multicarrier no-guard-interval CO-OFDM superchannel using ultra-large-area fiber,” IEEE Photon. Technol. Lett. |

9. | Y. Tang and W. Shieh, “Coherent optical OFDM transmission up to 1 Tb/s per channel,” J. Lightwave Technol. |

10. | X. Liu, S. Chandrasekhar, B. Zhu, and D. Peckham, “Efficient digital coherent detection of a 1.2-Tb/s 24-carrier no-guard-interval CO-OFDM signal by simultaneously detecting multiple carriers per sampling,” OFC. OWO2, (2010). |

11. | 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 × 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,” OFC. PDPB5, (2009). |

12. | 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 |

13. | J. Li, X. Li, X. Zhang, F. Tian, and L. Xi, “Analysis of the stability and optimizing operation of the single-side-band modulator based on re-circulating frequency shifter used for the T-bit/s optical communication transmission,” Opt. Express |

14. | A. Bellemare, M. Karasek, M. Rochette, S. LRochelle, and M. Tetu, “Room temperature multifrequency erbium-doped fiber lasers anchored on the ITU frequency grid,” J. Lightwave Technol. |

15. | K. Zhou, D. Zhou, F. Dong, and N. Q. Ngo, “Room-temperature multiwavelength erbium-doped fiber ring laser employing sinusoidal phase-modulation feedback,” Opt. Lett. |

16. | J. Yao, J. Yao, Z. Deng, and J. Liu, “Multiwavelength erbium-doped fiber ring laser incorporating an SOA-based phase modulator,” IEEE Photon. Technol. Lett. |

17. | M. A. Mirza and G. Stewart, “Multiwavelength operation of erbium-doped fiber lasers by period filtering and phase modulation,” J. Lightwave Technol. |

18. | 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. Möller, M. Hübner, 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 10.8Tbit/s,” OFC 2010: PDPC1. |

19. | J. Yu, Z. Dong, X. Xiao, Y. Xia, S. Shi, C. Ge, W. Zhou, N. Chi, and Y. Shao, “Generation of 112 coherent multi-carriers and transmission of 10 Tb/s (112x100Gb/s) single optical OFDM superchannel over 640 km SMF,”OFC 2011 PDP (paper accepted). |

**OCIS Codes**

(060.2320) Fiber optics and optical communications : Fiber optics amplifiers and oscillators

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

(060.2630) Fiber optics and optical communications : Frequency modulation

**ToC Category:**

Fiber Optics and Optical Communications

**History**

Original Manuscript: April 18, 2011

Revised Manuscript: June 5, 2011

Manuscript Accepted: June 6, 2011

Published: June 6, 2011

**Citation**

Junwen Zhang, Nan Chi, and Jianjun Yu, "Generation of coherent and frequency-lock multi-carriers using cascaded phase modulators and recirculating frequency shifter for Tb/s optical communication," Opt. Express **19**, 12891-12902 (2011)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-14-12891

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