## On-chip CMOS-compatible optical signal processor |

Optics Express, Vol. 20, Issue 12, pp. 13560-13565 (2012)

http://dx.doi.org/10.1364/OE.20.013560

Acrobat PDF (1595 KB)

### Abstract

We propose and demonstrate an optical signal processor performing matrix-vector multiplication, which is composed of laser-modulator array, multiplexer, splitter, microring modulator matrix and photodetector array. 8 × 10^{7} multiplications and accumulations (MACs) per second is implemented at the clock at a clock frequency of 10 MHz. All functional units can be ultimately monolithically integrated on a chip with the development of silicon photonics and an efficient high-performance computing system is expected in the future.

© 2012 OSA

## 1. Introduction

1. B. Razavi, “Prospects of CMOS technology for high-speed optical communication circuits,” IEEE J. Solid-state Circuits **2**(9), 1135–1145 (2002). [CrossRef]

2. D. A. B. Miller, “Device requirements for optical interconnects to silicon chips,” Proc. IEEE **97**(7), 1166–1185 (2009). [CrossRef]

3. M. Haurylau, G. Chen, H. Chen, J. Zhang, N. A. Nelson, D. H. Albonesi, E. G. Friedman, and P. M. Fauchet, “On-chip optical interconnect roadmap: challenges and critical directions,” IEEE J. Sel. Top. Quantum Electron. **12**(6), 1699–1705 (2006). [CrossRef]

4. H. J. Caulfield and S. Dolev, “Why future supercomputing requires optics,” Nat. Photonics **4**(5), 261–263 (2010). [CrossRef]

5. T. Barwicz, H. Byun, F. Gan, C. W. Holzwarth, M. A. Popovic, P. T. Rakich, M. R. Watts, E. P. Ippen, F. X. Kartner, H. I. Smith, J. S. Orcutt, R. J. Ram, V. Stojanovic, O. O. Olubuyide, J. L. Hoyt, S. Spector, M. Geis, M. Grein, T. Lyszczarz, and J. U. Yoon, “Silicon photonics for compact, energy-efficient interconnects [Invited],” J. Opt. Netw. **6**(1), 63–73 (2007). [CrossRef]

6. J. Ahn, M. Fiorentino, R. Beausoleil, N. Binkert, A. Davis, D. Fattal, N. Jouppi, M. McLaren, C. Santori, R. Schreiber, S. Spillane, D. Vantrease, and Q. Xu, “Devices and architectures for photonic chip-scale integration,” Appl. Phys., A Mater. Sci. Process. **95**(4), 989–997 (2009). [CrossRef]

7. D. A. B. Miller, “Are optical transistors the logical next step,” Nat. Photonics **4**(1), 3–5 (2010). [CrossRef]

8. Q. Xu and R. Soref, “Reconfigurable optical directed-logic circuits using microresonator-based optical switches,” Opt. Express **19**(6), 5244–5259 (2011). [CrossRef] [PubMed]

9. R. S. Tucker and J. L. Riding, “Optical ring-resonator random-access memories,” J. Lightwave Technol. **26**(3), 320–328 (2008). [CrossRef]

^{7}multiplications and accumulations (MACs) per second is implemented by such an on-chip microring modulator matrix and off-chip laser-modulator array, multiplexer and photodetector. The significant progress in integrated optoelectronics makes it possible to integrate all required functional optical devices and even the driving and controlling circuits on the same chip [14

14. D. Liang and J. E. Bowers, “Recent progress in lasers on silicon,” Nat. Photonics **4**(8), 511–517 (2010). [CrossRef]

16. J. Michel, J. Liu, and L. C. Kimerling, “High-performance Ge-on-Si photodetector,” Nat. Photonics **4**(8), 527–534 (2010). [CrossRef]

^{14}MAC/s.

## 2. Design and fabrication

20. J. W. Goodman, A. R. Dias, and L. M. Woody, “Fully parallel, high-speed incoherent optical method for performing discrete Fourier transforms,” Opt. Lett. **2**(1), 1–3 (1978). [CrossRef] [PubMed]

23. R. Q. Ji, L. Yang, L. Zhang, Y. H. Tian, J. F. Ding, H. T. Chen, Y. Y. Lu, P. Zhou, and W. W. Zhu, “Five-port optical router for photonic networks-on-chip,” Opt. Express **19**(21), 20258–20268 (2011). [CrossRef] [PubMed]

20. J. W. Goodman, A. R. Dias, and L. M. Woody, “Fully parallel, high-speed incoherent optical method for performing discrete Fourier transforms,” Opt. Lett. **2**(1), 1–3 (1978). [CrossRef] [PubMed]

*M*×

*N*matrix

**and an**

*A**N*×

*1*vector

**is shown in Fig. 1 . The elements of the vector**

*B***are represented by the output optical power of the**

*B**N*optical signals with

*N*different wavelengths (

*λ*

_{1},

*λ*

_{2}, …,

*λ*

_{N}), which can be generated by

*N*externally or directly modulated laser diodes. The

*N*optical signals are multiplexed to one common waveguide by a multiplexer and then projected parallel on

*M*rows of modulators by a

*1*×

*M*optical splitter. The element

*a*

_{ij}of the matrix

**is represented by the transmissivity of the microring modulator located at the**

*A**i*

^{th}row and the

*j*

^{th}column of the microring modulator matrix. Note that each microring modulator located at the same row only manipulates the optical signal with a specific wavelength. All the

*M*×

*N*multiplication processes are carried out when the

*M*×

*N*optical pulses pass through the microring modulator matrix. Each of the

*M*accumulation processes is carried out when the

*N*optical signals with different wavelengths in a row of the microring modulator matrix are guided to the common output waveguide. The elements of the result vector

**are represented by the**

*C**M*optical powers detected by the photodetector array.

24. Q. Xu, B. Schmidt, S. Pradhan, and M. Lipson, “Micrometre-scale silicon electro-optic modulator,” Nature **435**(7040), 325–327 (2005). [CrossRef] [PubMed]

25. Q. Xu, D. Fattal, and R. G. Beausoleil, “Silicon microring resonators with 1.5-microm radius,” Opt. Express **16**(6), 4309–4315 (2008). [CrossRef] [PubMed]

**. Then the four optical signals are multiplexed and coupled into the bus waveguide of the cascaded microring modulators by a lensed fiber. Since the waveguides are polarization-dependent, each wavelength channel is controlled independently by a polarization controller before they are multiplexed to a fiber. Eight parallel electrical driving signals are generated by four synchronized two-channel arbitrary function generators (Tektronix AFG3102). Four signals are parallel applied to the MZI modulators to generate the optical vector (**

*B***= (**

*B**b*

_{1},

*b*

_{2},

*b*

_{3},

*b*

_{4})’), and the other four signals representing the first row of matrix

**(**

*A***= (**

*A*_{1}*a*

_{11},

*a*

_{12},

*a*

_{13},

*a*

_{14})) are parallel applied to the cascaded microring modulators. The optical signals ejected from the chip are amplified by an erbium-doped fiber amplifier and filtered by an optical band-pass filter. Finally, the optical power, representing the inner product of vector

**and vector**

*A*_{1}**, is detected by a photodetector. The waveforms are recorded by a multichannel oscilloscope. Note that the microring modulator works well at the speed of 500 Mb/s with direct driving signal. Limited by the experimental conditions, the demo system is characterized at 10MHz. Figure 4 shows the waveforms of the eight driving signals and the final result of a vector-vector multiplication. The tested waveforms show that the multiplication of vector**

*B*

*A*_{1}with vector

**with the speed of 10**

*B*^{8}MAC/s is performed correctly at a clock frequency of 10 MHz.

## 3. Discussion

## 4. Conclusion

^{7}multiplications and accumulations (MACs) per second is implemented at the clock at a clock frequency of 10 MHz. All functional units can be ultimately monolithically integrated on a chip with the development of silicon photonics and an efficient high-performance computing system is expected in the future.

## Acknowledgments

## References and links

1. | B. Razavi, “Prospects of CMOS technology for high-speed optical communication circuits,” IEEE J. Solid-state Circuits |

2. | D. A. B. Miller, “Device requirements for optical interconnects to silicon chips,” Proc. IEEE |

3. | M. Haurylau, G. Chen, H. Chen, J. Zhang, N. A. Nelson, D. H. Albonesi, E. G. Friedman, and P. M. Fauchet, “On-chip optical interconnect roadmap: challenges and critical directions,” IEEE J. Sel. Top. Quantum Electron. |

4. | H. J. Caulfield and S. Dolev, “Why future supercomputing requires optics,” Nat. Photonics |

5. | T. Barwicz, H. Byun, F. Gan, C. W. Holzwarth, M. A. Popovic, P. T. Rakich, M. R. Watts, E. P. Ippen, F. X. Kartner, H. I. Smith, J. S. Orcutt, R. J. Ram, V. Stojanovic, O. O. Olubuyide, J. L. Hoyt, S. Spector, M. Geis, M. Grein, T. Lyszczarz, and J. U. Yoon, “Silicon photonics for compact, energy-efficient interconnects [Invited],” J. Opt. Netw. |

6. | J. Ahn, M. Fiorentino, R. Beausoleil, N. Binkert, A. Davis, D. Fattal, N. Jouppi, M. McLaren, C. Santori, R. Schreiber, S. Spillane, D. Vantrease, and Q. Xu, “Devices and architectures for photonic chip-scale integration,” Appl. Phys., A Mater. Sci. Process. |

7. | D. A. B. Miller, “Are optical transistors the logical next step,” Nat. Photonics |

8. | Q. Xu and R. Soref, “Reconfigurable optical directed-logic circuits using microresonator-based optical switches,” Opt. Express |

9. | R. S. Tucker and J. L. Riding, “Optical ring-resonator random-access memories,” J. Lightwave Technol. |

10. | L. Zhang, M. Geng, L. Yang, L. Jia, H. Tian, P. Chen, T. Wang, and Y. Liu, “A silicon-based integrated optical vector-matrix multiplier,” CN patent #2011/10116741.0. |

11. | M. Ferrera, Y. Park, L. Razzari, B. E. Little, S. T. Chu, R. Morandotti, D. J. Moss, and J. Azaña, “On-chip CMOS-compatible all-optical integrator,” Nat. Commun |

12. | L. Zhang, R. Ji, Y. Tian, L. Yang, P. Zhou, Y. Lu, W. Zhu, Y. Liu, L. Jia, Q. Fang, and M. Yu, “Simultaneous implementation of XOR and XNOR operations using a directed logic circuit based on two microring resonators,” Opt. Express |

13. | M. R. Watts, “Integrated optic vector-matrix multiplier,” US patent #2011/8027587B1. |

14. | D. Liang and J. E. Bowers, “Recent progress in lasers on silicon,” Nat. Photonics |

15. | G. T. Reed, G. Mashanovich, F. T. Gardes, and D. J. Thomson, “silicon optical modulator,” Nat. Photonics |

16. | J. Michel, J. Liu, and L. C. Kimerling, “High-performance Ge-on-Si photodetector,” Nat. Photonics |

17. | R. C. Gonzalez and R. E. Wood, |

18. | M. A. Richards, |

19. | S. Betti, G. D. Marchis, and E. Iannone, |

20. | J. W. Goodman, A. R. Dias, and L. M. Woody, “Fully parallel, high-speed incoherent optical method for performing discrete Fourier transforms,” Opt. Lett. |

21. | |

22. | D. E. Tamir, N. T. Shaked, P. J. Wilson, and S. Dolev, “High-speed and low-power electro-optical DSP coprocessor,” J. Opt. Soc. Am. A |

23. | R. Q. Ji, L. Yang, L. Zhang, Y. H. Tian, J. F. Ding, H. T. Chen, Y. Y. Lu, P. Zhou, and W. W. Zhu, “Five-port optical router for photonic networks-on-chip,” Opt. Express |

24. | Q. Xu, B. Schmidt, S. Pradhan, and M. Lipson, “Micrometre-scale silicon electro-optic modulator,” Nature |

25. | Q. Xu, D. Fattal, and R. G. Beausoleil, “Silicon microring resonators with 1.5-microm radius,” Opt. Express |

26. | X. Xiao, H. Xu, X. Li, Y. Hu, K. Xiong, Z. Li, T. Chu, Y. Yu, and J. Yu, “25 Gbit/s silicon microring modulator based on misalignment-tolerant interleaved PN junctions,” Opt. Express |

27. | J. Liu, X. Sun, R. Camacho-Aguilera, L. C. Kimerling, and J. Michel, “Ge-on-Si laser operating at room temperature,” Opt. Lett. |

28. | H. Park, A. Fang, S. Kodama, and J. Bowers, “Hybrid silicon evanescent laser fabricated with a silicon waveguide and III-V offset quantum wells,” Opt. Express |

**OCIS Codes**

(130.3120) Integrated optics : Integrated optics devices

(200.4740) Optics in computing : Optical processing

(200.4960) Optics in computing : Parallel processing

(230.5750) Optical devices : Resonators

**ToC Category:**

Integrated Optics

**History**

Original Manuscript: March 29, 2012

Revised Manuscript: May 18, 2012

Manuscript Accepted: May 24, 2012

Published: June 1, 2012

**Citation**

Lin Yang, Ruiqiang Ji, Lei Zhang, Jianfeng Ding, and Qianfan Xu, "On-chip CMOS-compatible optical signal processor," Opt. Express **20**, 13560-13565 (2012)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-12-13560

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### References

- B. Razavi, “Prospects of CMOS technology for high-speed optical communication circuits,” IEEE J. Solid-state Circuits2(9), 1135–1145 (2002). [CrossRef]
- D. A. B. Miller, “Device requirements for optical interconnects to silicon chips,” Proc. IEEE97(7), 1166–1185 (2009). [CrossRef]
- M. Haurylau, G. Chen, H. Chen, J. Zhang, N. A. Nelson, D. H. Albonesi, E. G. Friedman, and P. M. Fauchet, “On-chip optical interconnect roadmap: challenges and critical directions,” IEEE J. Sel. Top. Quantum Electron.12(6), 1699–1705 (2006). [CrossRef]
- H. J. Caulfield and S. Dolev, “Why future supercomputing requires optics,” Nat. Photonics4(5), 261–263 (2010). [CrossRef]
- T. Barwicz, H. Byun, F. Gan, C. W. Holzwarth, M. A. Popovic, P. T. Rakich, M. R. Watts, E. P. Ippen, F. X. Kartner, H. I. Smith, J. S. Orcutt, R. J. Ram, V. Stojanovic, O. O. Olubuyide, J. L. Hoyt, S. Spector, M. Geis, M. Grein, T. Lyszczarz, and J. U. Yoon, “Silicon photonics for compact, energy-efficient interconnects [Invited],” J. Opt. Netw.6(1), 63–73 (2007). [CrossRef]
- J. Ahn, M. Fiorentino, R. Beausoleil, N. Binkert, A. Davis, D. Fattal, N. Jouppi, M. McLaren, C. Santori, R. Schreiber, S. Spillane, D. Vantrease, and Q. Xu, “Devices and architectures for photonic chip-scale integration,” Appl. Phys., A Mater. Sci. Process.95(4), 989–997 (2009). [CrossRef]
- D. A. B. Miller, “Are optical transistors the logical next step,” Nat. Photonics4(1), 3–5 (2010). [CrossRef]
- Q. Xu and R. Soref, “Reconfigurable optical directed-logic circuits using microresonator-based optical switches,” Opt. Express19(6), 5244–5259 (2011). [CrossRef] [PubMed]
- R. S. Tucker and J. L. Riding, “Optical ring-resonator random-access memories,” J. Lightwave Technol.26(3), 320–328 (2008). [CrossRef]
- L. Zhang, M. Geng, L. Yang, L. Jia, H. Tian, P. Chen, T. Wang, and Y. Liu, “A silicon-based integrated optical vector-matrix multiplier,” CN patent #2011/10116741.0.
- M. Ferrera, Y. Park, L. Razzari, B. E. Little, S. T. Chu, R. Morandotti, D. J. Moss, and J. Azaña, “On-chip CMOS-compatible all-optical integrator,” Nat. Commun1(3), 29 (2010). [CrossRef] [PubMed]
- L. Zhang, R. Ji, Y. Tian, L. Yang, P. Zhou, Y. Lu, W. Zhu, Y. Liu, L. Jia, Q. Fang, and M. Yu, “Simultaneous implementation of XOR and XNOR operations using a directed logic circuit based on two microring resonators,” Opt. Express19(7), 6524–6540 (2011). [CrossRef] [PubMed]
- M. R. Watts, “Integrated optic vector-matrix multiplier,” US patent #2011/8027587B1.
- D. Liang and J. E. Bowers, “Recent progress in lasers on silicon,” Nat. Photonics4(8), 511–517 (2010). [CrossRef]
- G. T. Reed, G. Mashanovich, F. T. Gardes, and D. J. Thomson, “silicon optical modulator,” Nat. Photonics4(8), 518–526 (2010). [CrossRef]
- J. Michel, J. Liu, and L. C. Kimerling, “High-performance Ge-on-Si photodetector,” Nat. Photonics4(8), 527–534 (2010). [CrossRef]
- R. C. Gonzalez and R. E. Wood, Digital Image Processing (Prentice Hall, 2007).
- M. A. Richards, Fundamentals of Radar Signal Processing (McGraw-Hill, 2005).
- S. Betti, G. D. Marchis, and E. Iannone, Coherent Optical Communications Systems (Wiley, 1995).
- J. W. Goodman, A. R. Dias, and L. M. Woody, “Fully parallel, high-speed incoherent optical method for performing discrete Fourier transforms,” Opt. Lett.2(1), 1–3 (1978). [CrossRef] [PubMed]
- http://www.thirdwave.de/3w/tech/optical/EnLight256.pdf .
- D. E. Tamir, N. T. Shaked, P. J. Wilson, and S. Dolev, “High-speed and low-power electro-optical DSP coprocessor,” J. Opt. Soc. Am. A26(8), A11–A20 (2009). [CrossRef] [PubMed]
- R. Q. Ji, L. Yang, L. Zhang, Y. H. Tian, J. F. Ding, H. T. Chen, Y. Y. Lu, P. Zhou, and W. W. Zhu, “Five-port optical router for photonic networks-on-chip,” Opt. Express19(21), 20258–20268 (2011). [CrossRef] [PubMed]
- Q. Xu, B. Schmidt, S. Pradhan, and M. Lipson, “Micrometre-scale silicon electro-optic modulator,” Nature435(7040), 325–327 (2005). [CrossRef] [PubMed]
- Q. Xu, D. Fattal, and R. G. Beausoleil, “Silicon microring resonators with 1.5-microm radius,” Opt. Express16(6), 4309–4315 (2008). [CrossRef] [PubMed]
- X. Xiao, H. Xu, X. Li, Y. Hu, K. Xiong, Z. Li, T. Chu, Y. Yu, and J. Yu, “25 Gbit/s silicon microring modulator based on misalignment-tolerant interleaved PN junctions,” Opt. Express20(3), 2507–2515 (2012). [CrossRef] [PubMed]
- J. Liu, X. Sun, R. Camacho-Aguilera, L. C. Kimerling, and J. Michel, “Ge-on-Si laser operating at room temperature,” Opt. Lett.35(5), 679–681 (2010). [CrossRef] [PubMed]
- H. Park, A. Fang, S. Kodama, and J. Bowers, “Hybrid silicon evanescent laser fabricated with a silicon waveguide and III-V offset quantum wells,” Opt. Express13(23), 9460–9464 (2005). [CrossRef] [PubMed]

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