## Design studies for ASIC implementations of 28 GS/s optical QPSK- and 16-QAM-OFDM transceivers |

Optics Express, Vol. 19, Issue 21, pp. 20857-20864 (2011)

http://dx.doi.org/10.1364/OE.19.020857

Acrobat PDF (952 KB)

### Abstract

We designed at the register-transfer-level digital signal processing (DSP) circuits for 21.8 Gb/s and 43.7 Gb/s QPSK- and 16-QAM-encoded optical orthogonal frequency division multiplexing (OFDM) transceivers, and carried out synthesis and simulations assessing performance, power consumption and chip area. The aim of the study is to determine the suitability of OFDM technology for low-cost optical interconnects. Power calculations based on synthesis for a 65nm standard-cell library showed that the DSP components of the transceiver (FFTs, equalisation, (de)mapping and clipping/scaling circuits) consume 18.2 mW/Gb/s and 12.8 mW/Gb/s in the case of QPSK and 16-QAM respectively.

© 2011 OSA

## 1. Introduction

1. W. Shieh, X. Yi, Y. Ma, and Q. Yang, “Coherent optical OFDM: has its time come? [Invited],” J. Opt. Netw. **7**(3), 234–255 (2008). [CrossRef]

3. Y. Benlachtar, P. M. Watts, R. Bouziane, P. Milder, D. Rangaraj, A. Cartolano, R. Koutsoyannis, J. C. Hoe, M. Püschel, M. Glick, and R. I. Killey, “Generation of optical OFDM signals using 21.4 GS/s real time digital signal processing,” Opt. Express **17**(20), 17658–17668 (2009). [CrossRef] [PubMed]

5. S. C. J. Lee, F. Breyer, D. Cardenas, S. Randel, and A. M. J. Koonen, “Real-time gigabit DMT transmission over plastic optical fibre,” Electron. Lett. **45**(25), 1342–1343 (2009). [CrossRef]

6. Q. Yang, S. Chen, Y. Ma, and W. Shieh, “Real-time reception of multi-gigabit coherent optical OFDM signals,” Opt. Express **17**(10), 7985–7992 (2009). [CrossRef] [PubMed]

7. N. Kaneda, Q. Yang, X. Liu, S. Chandrasekhar, W. Shieh, and Y. Chen, “Real-Time 2.5 GS/s Coherent Optical Receiver for 53.3-Gb/s Sub-Banded OFDM,” J. Lightwave Technol. **28**(4), 494–501 (2010). [CrossRef]

4. F. Buchali, R. Dischler, A. Klekamp, M. Bernhard, and D. Efinger, “Realization of a real-time 12.1 Gb/s optical OFDM transmitter and its application in a 109 Gb/s transmission system with coherent reception,” in Proc. European Conference on Optical Communication (ECOC), (Vienna, 2009), PD paper 2.1.

3. Y. Benlachtar, P. M. Watts, R. Bouziane, P. Milder, D. Rangaraj, A. Cartolano, R. Koutsoyannis, J. C. Hoe, M. Püschel, M. Glick, and R. I. Killey, “Generation of optical OFDM signals using 21.4 GS/s real time digital signal processing,” Opt. Express **17**(20), 17658–17668 (2009). [CrossRef] [PubMed]

8. Y. Benlachtar, P. M. Watts, R. Bouziane, P. Milder, R. Koutsoyannis, J. C. Hoe, M. Püschel, M. Glick, and R. I. Killey, “21.4 GS/s real-time DSP-based optical OFDM signal generation and transmission over 1600km of uncompensated fibre,” in Proc. European Conference on Optical Communication (ECOC), (Vienna, 2009), PD paper 2.4.

6. Q. Yang, S. Chen, Y. Ma, and W. Shieh, “Real-time reception of multi-gigabit coherent optical OFDM signals,” Opt. Express **17**(10), 7985–7992 (2009). [CrossRef] [PubMed]

7. N. Kaneda, Q. Yang, X. Liu, S. Chandrasekhar, W. Shieh, and Y. Chen, “Real-Time 2.5 GS/s Coherent Optical Receiver for 53.3-Gb/s Sub-Banded OFDM,” J. Lightwave Technol. **28**(4), 494–501 (2010). [CrossRef]

9. R. P. Giddings, X. Q. Jin, H. H. Kee, X. L. Yang, and J. M. Tang, “Real-time implementation of optical OFDM transmitters and receivers for practical end-to-end optical transmission systems,” Electron. Lett. **45**(15), 800–802 (2009). [CrossRef]

10. X. Q. Jin, R. P. Giddings, and J. M. Tang, “Real-time transmission of 3 Gb/s 16-QAM encoded optical OFDM signals over 75 km SMFs with negative power penalties,” Opt. Express **17**(17), 14574–14585 (2009). [CrossRef] [PubMed]

11. R. P. Giddings, X. Q. Jin, and J. M. Tang, “First experimental demonstration of 6Gb/s real-time optical OFDM transceivers incorporating channel estimation and variable power loading,” Opt. Express **17**(22), 19727–19738 (2009). [CrossRef] [PubMed]

12. R. P. Giddings, X. Q. Jin, E. Hugues-Salas, E. Giacoumidis, J. L. Wei, and J. M. Tang, “Experimental demonstration of a record high 11.25Gb/s real-time optical OFDM transceiver supporting 25km SMF end-to-end transmission in simple IMDD systems,” Opt. Express **18**(6), 5541–5555 (2010). [CrossRef] [PubMed]

14. R. Bouziane, P. Milder, R. Koutsoyannis, Y. Benlachtar, C. R. Berger, J. C. Hoe, M. Püschel, M. Glick, and R. I. Killey, “Design Studies for an ASIC Implementation of an Optical OFDM Transceiver”, in Proc. European Conference on Optical Communications (ECOC), Torino, 19 - 23 September 2010, paper Tu.5.A.4.

15. Synopsys Design Compiler, http://www.synopsys.com/Tools/Implementation/RTLSynthesis/Pages/DCUltra.aspx

## 2. System configuration

*n*-bit 128-point inverse FFT. The system uses the discrete multi-tone (DMT) modulation format [5

5. S. C. J. Lee, F. Breyer, D. Cardenas, S. Randel, and A. M. J. Koonen, “Real-time gigabit DMT transmission over plastic optical fibre,” Electron. Lett. **45**(25), 1342–1343 (2009). [CrossRef]

*p*-bit FFT, following which the data-carrying channels are equalised with 1-tap equalisers and decoded. The DAC and ADC operate at a sampling rate of 28 GS/s and the raw data-rate of the OFDM signal is 21.8 Gb/s for QPSK and 43.7 Gb/s for 16-QAM. Designs with different clock speeds and FFT algorithms are investigated as described in section 4. Other sources of noise besides quantisation noise were neglected. Currently, our transceiver simulations assume synchronisation with a single clock [12

12. R. P. Giddings, X. Q. Jin, E. Hugues-Salas, E. Giacoumidis, J. L. Wei, and J. M. Tang, “Experimental demonstration of a record high 11.25Gb/s real-time optical OFDM transceiver supporting 25km SMF end-to-end transmission in simple IMDD systems,” Opt. Express **18**(6), 5541–5555 (2010). [CrossRef] [PubMed]

## 3. Transmitter and receiver FFT resolution

^{15}de Bruijn sequence as an input stimulus. The inverse FFT in the transmitter used a 10 bit precision for the QPSK modulation format based on results from our previous work [16

16. Y. Benlachtar, P. M. Watts, R. Bouziane, P. Milder, R. Koutsoyannis, J. C. Hoe, M. Püschel, M. Glick, and R. I. Killey, “Real-Time Digital Signal Processing for the Generation of Optical Orthogonal Frequency-Division-Multiplexed Signals,” IEEE J. Sel. Top. Quantum Electron. **16**(5), 1235–1244 (2010). [CrossRef]

_{max}. The EVM is given by [17]:where

*I*and

_{k}*Q*are the components of the

_{k}*k*-th received symbol and

*k*-th ideal symbol.

## 4. ASIC power consumption and area

^{12}fixed point operations per second. The designs that process more samples per cycle have a higher area but are clocked at a lower frequency and thus consume less power. This allows a trade-off between power consumption and area.

15. Synopsys Design Compiler, http://www.synopsys.com/Tools/Implementation/RTLSynthesis/Pages/DCUltra.aspx

## 5. Optical interconnect simulation

## 6. Conclusions

## References and links

1. | W. Shieh, X. Yi, Y. Ma, and Q. Yang, “Coherent optical OFDM: has its time come? [Invited],” J. Opt. Netw. |

2. | B. J. C. Schmidt, Z. Zan, L. B. Du, and A. J. Lowery, “100Gbit/s transmission using single-band direct-detection optical OFDM”, in Proc. Optical Fiber Comm.(OFC), paper PDPC3 (2009). |

3. | Y. Benlachtar, P. M. Watts, R. Bouziane, P. Milder, D. Rangaraj, A. Cartolano, R. Koutsoyannis, J. C. Hoe, M. Püschel, M. Glick, and R. I. Killey, “Generation of optical OFDM signals using 21.4 GS/s real time digital signal processing,” Opt. Express |

4. | F. Buchali, R. Dischler, A. Klekamp, M. Bernhard, and D. Efinger, “Realization of a real-time 12.1 Gb/s optical OFDM transmitter and its application in a 109 Gb/s transmission system with coherent reception,” in Proc. European Conference on Optical Communication (ECOC), (Vienna, 2009), PD paper 2.1. |

5. | S. C. J. Lee, F. Breyer, D. Cardenas, S. Randel, and A. M. J. Koonen, “Real-time gigabit DMT transmission over plastic optical fibre,” Electron. Lett. |

6. | Q. Yang, S. Chen, Y. Ma, and W. Shieh, “Real-time reception of multi-gigabit coherent optical OFDM signals,” Opt. Express |

7. | N. Kaneda, Q. Yang, X. Liu, S. Chandrasekhar, W. Shieh, and Y. Chen, “Real-Time 2.5 GS/s Coherent Optical Receiver for 53.3-Gb/s Sub-Banded OFDM,” J. Lightwave Technol. |

8. | Y. Benlachtar, P. M. Watts, R. Bouziane, P. Milder, R. Koutsoyannis, J. C. Hoe, M. Püschel, M. Glick, and R. I. Killey, “21.4 GS/s real-time DSP-based optical OFDM signal generation and transmission over 1600km of uncompensated fibre,” in Proc. European Conference on Optical Communication (ECOC), (Vienna, 2009), PD paper 2.4. |

9. | R. P. Giddings, X. Q. Jin, H. H. Kee, X. L. Yang, and J. M. Tang, “Real-time implementation of optical OFDM transmitters and receivers for practical end-to-end optical transmission systems,” Electron. Lett. |

10. | X. Q. Jin, R. P. Giddings, and J. M. Tang, “Real-time transmission of 3 Gb/s 16-QAM encoded optical OFDM signals over 75 km SMFs with negative power penalties,” Opt. Express |

11. | R. P. Giddings, X. Q. Jin, and J. M. Tang, “First experimental demonstration of 6Gb/s real-time optical OFDM transceivers incorporating channel estimation and variable power loading,” Opt. Express |

12. | R. P. Giddings, X. Q. Jin, E. Hugues-Salas, E. Giacoumidis, J. L. Wei, and J. M. Tang, “Experimental demonstration of a record high 11.25Gb/s real-time optical OFDM transceiver supporting 25km SMF end-to-end transmission in simple IMDD systems,” Opt. Express |

13. | R. S. Tucker, “The role of optics and electronics in high capacity routers,” IEEE/OSA J. Lightwave Technol. 24–12, 4655–4673 (2006). |

14. | R. Bouziane, P. Milder, R. Koutsoyannis, Y. Benlachtar, C. R. Berger, J. C. Hoe, M. Püschel, M. Glick, and R. I. Killey, “Design Studies for an ASIC Implementation of an Optical OFDM Transceiver”, in Proc. European Conference on Optical Communications (ECOC), Torino, 19 - 23 September 2010, paper Tu.5.A.4. |

15. | Synopsys Design Compiler, http://www.synopsys.com/Tools/Implementation/RTLSynthesis/Pages/DCUltra.aspx |

16. | Y. Benlachtar, P. M. Watts, R. Bouziane, P. Milder, R. Koutsoyannis, J. C. Hoe, M. Püschel, M. Glick, and R. I. Killey, “Real-Time Digital Signal Processing for the Generation of Optical Orthogonal Frequency-Division-Multiplexed Signals,” IEEE J. Sel. Top. Quantum Electron. |

17. | R. A. Shafik, M. S. Rahman, and A. H. M. R. Islam, “On the extended relationships among EVM, BER and SNR as performance metrics,” in Proc. ICECE’06, Bangladesh, Dec. 2006, pp. 408–411. |

18. | P. Milder, F. Franchetti, J. C. Hoe, and M. Püschel, “Formal datapath representation and manipulation for implementing DSP transforms,” in Proc. ACM/IEEE Design Automation Conference (DAC), pp. 385–390, 8–13 June 2008. |

19. | C. Van Loan, Computational Frameworks for the Fast Fourier Transform, SIAM (1992) |

20. | I. Dedic, “56Gs/s ADC: Enabling 100GbE,” in Proc. OFC/NFOEC, 2010, paper OThT6. |

21. | P. Milder, R. Bouziane, R. Koutsoyannis, C. R. Berger, Y. Benlachtar, R. I. Killey, M. Glick, and J. C. Hoe, “Design and Simulation of 25 Gb/s Optical OFDM Transceiver ASICs”, to be presented at European Conference on Optical Communications (ECOC), Geneva, 18 – 22 September 2011. |

**OCIS Codes**

(060.4080) Fiber optics and optical communications : Modulation

(060.4510) Fiber optics and optical communications : Optical communications

**ToC Category:**

Fiber Optics and Optical Communications

**History**

Original Manuscript: May 26, 2011

Revised Manuscript: July 7, 2011

Manuscript Accepted: July 10, 2011

Published: October 5, 2011

**Citation**

Rachid Bouziane, Peter Milder, Robert Koutsoyannis, Yannis Benlachtar, James C. Hoe, Markus Püschel, Madeleine Glick, and Robert I. Killey, "Design studies for ASIC implementations of 28 GS/s optical QPSK- and 16-QAM-OFDM transceivers," Opt. Express **19**, 20857-20864 (2011)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-21-20857

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### References

- W. Shieh, X. Yi, Y. Ma, and Q. Yang, “Coherent optical OFDM: has its time come? [Invited],” J. Opt. Netw.7(3), 234–255 (2008). [CrossRef]
- B. J. C. Schmidt, Z. Zan, L. B. Du, and A. J. Lowery, “100Gbit/s transmission using single-band direct-detection optical OFDM”, in Proc. Optical Fiber Comm.(OFC), paper PDPC3 (2009).
- Y. Benlachtar, P. M. Watts, R. Bouziane, P. Milder, D. Rangaraj, A. Cartolano, R. Koutsoyannis, J. C. Hoe, M. Püschel, M. Glick, and R. I. Killey, “Generation of optical OFDM signals using 21.4 GS/s real time digital signal processing,” Opt. Express17(20), 17658–17668 (2009). [CrossRef] [PubMed]
- F. Buchali, R. Dischler, A. Klekamp, M. Bernhard, and D. Efinger, “Realization of a real-time 12.1 Gb/s optical OFDM transmitter and its application in a 109 Gb/s transmission system with coherent reception,” in Proc. European Conference on Optical Communication (ECOC), (Vienna, 2009), PD paper 2.1.
- S. C. J. Lee, F. Breyer, D. Cardenas, S. Randel, and A. M. J. Koonen, “Real-time gigabit DMT transmission over plastic optical fibre,” Electron. Lett.45(25), 1342–1343 (2009). [CrossRef]
- Q. Yang, S. Chen, Y. Ma, and W. Shieh, “Real-time reception of multi-gigabit coherent optical OFDM signals,” Opt. Express17(10), 7985–7992 (2009). [CrossRef] [PubMed]
- N. Kaneda, Q. Yang, X. Liu, S. Chandrasekhar, W. Shieh, and Y. Chen, “Real-Time 2.5 GS/s Coherent Optical Receiver for 53.3-Gb/s Sub-Banded OFDM,” J. Lightwave Technol.28(4), 494–501 (2010). [CrossRef]
- Y. Benlachtar, P. M. Watts, R. Bouziane, P. Milder, R. Koutsoyannis, J. C. Hoe, M. Püschel, M. Glick, and R. I. Killey, “21.4 GS/s real-time DSP-based optical OFDM signal generation and transmission over 1600km of uncompensated fibre,” in Proc. European Conference on Optical Communication (ECOC), (Vienna, 2009), PD paper 2.4.
- R. P. Giddings, X. Q. Jin, H. H. Kee, X. L. Yang, and J. M. Tang, “Real-time implementation of optical OFDM transmitters and receivers for practical end-to-end optical transmission systems,” Electron. Lett.45(15), 800–802 (2009). [CrossRef]
- X. Q. Jin, R. P. Giddings, and J. M. Tang, “Real-time transmission of 3 Gb/s 16-QAM encoded optical OFDM signals over 75 km SMFs with negative power penalties,” Opt. Express17(17), 14574–14585 (2009). [CrossRef] [PubMed]
- R. P. Giddings, X. Q. Jin, and J. M. Tang, “First experimental demonstration of 6Gb/s real-time optical OFDM transceivers incorporating channel estimation and variable power loading,” Opt. Express17(22), 19727–19738 (2009). [CrossRef] [PubMed]
- R. P. Giddings, X. Q. Jin, E. Hugues-Salas, E. Giacoumidis, J. L. Wei, and J. M. Tang, “Experimental demonstration of a record high 11.25Gb/s real-time optical OFDM transceiver supporting 25km SMF end-to-end transmission in simple IMDD systems,” Opt. Express18(6), 5541–5555 (2010). [CrossRef] [PubMed]
- R. S. Tucker, “The role of optics and electronics in high capacity routers,” IEEE/OSA J. Lightwave Technol. 24–12, 4655–4673 (2006).
- R. Bouziane, P. Milder, R. Koutsoyannis, Y. Benlachtar, C. R. Berger, J. C. Hoe, M. Püschel, M. Glick, and R. I. Killey, “Design Studies for an ASIC Implementation of an Optical OFDM Transceiver”, in Proc. European Conference on Optical Communications (ECOC), Torino, 19 - 23 September 2010, paper Tu.5.A.4.
- Synopsys Design Compiler, http://www.synopsys.com/Tools/Implementation/RTLSynthesis/Pages/DCUltra.aspx
- Y. Benlachtar, P. M. Watts, R. Bouziane, P. Milder, R. Koutsoyannis, J. C. Hoe, M. Püschel, M. Glick, and R. I. Killey, “Real-Time Digital Signal Processing for the Generation of Optical Orthogonal Frequency-Division-Multiplexed Signals,” IEEE J. Sel. Top. Quantum Electron.16(5), 1235–1244 (2010). [CrossRef]
- R. A. Shafik, M. S. Rahman, and A. H. M. R. Islam, “On the extended relationships among EVM, BER and SNR as performance metrics,” in Proc. ICECE’06, Bangladesh, Dec. 2006, pp. 408–411.
- P. Milder, F. Franchetti, J. C. Hoe, and M. Püschel, “Formal datapath representation and manipulation for implementing DSP transforms,” in Proc. ACM/IEEE Design Automation Conference (DAC), pp. 385–390, 8–13 June 2008.
- C. Van Loan, Computational Frameworks for the Fast Fourier Transform, SIAM (1992)
- I. Dedic, “56Gs/s ADC: Enabling 100GbE,” in Proc. OFC/NFOEC, 2010, paper OThT6.
- P. Milder, R. Bouziane, R. Koutsoyannis, C. R. Berger, Y. Benlachtar, R. I. Killey, M. Glick, and J. C. Hoe, “Design and Simulation of 25 Gb/s Optical OFDM Transceiver ASICs”, to be presented at European Conference on Optical Communications (ECOC), Geneva, 18 – 22 September 2011.

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