The Case for All-Optical Signal Processing in Next-Generation Photonic Networks

1. The Case for All-Optical Signal Processing in Next-Generation Photonic Networks Lawrence R. Chen Photonic Systems Group Department of Electrical and Computer Engineering McGill University Montreal, Quebec, Canada lawrence.chen@mcgill.ca

2. Acknowledgements Dr. Pegah Seddighian, Xing Hua (Tommy Cai), Prof. Martin Rochette Prof. Juan Hern�ndez-Cordero, UNAM-Mexico Financial support: Natural Sciences and Engineering Research Council of Canada Canadian Institute for Photonic Innovations

3. General Motivation Bandwidth demand

4. Short Pulse Optical Sources Services, Network evolution

5. Signal Processing Electrical Optical

6. Electrical Signal Processing Diagram of general approach

7. Nortel ASIC Example of chip from Nortel

8. Optical Signal Processing What can it offer? Multi-channel operation Multi-functionality

9. Tunable Optical Delays

10. Motivation

11. Multi-Channel Delay usinga Single Delay Element Objectives: Transparency to modulation format and bit rate No delay dependency or power penalty to the presence of other channel (no cross-talk) Approach: Dual-channel operation based on the conversion-dispersion method

12. Conversion-Dispersion Conversion: based on FWM in a length of HNLF Transparent to modulation format and data rate of input signal (e.g., NRZ, RZ, DPSK) Dispersion: based on a linearly chirped fiber Bragg grating Compact Can always use a length of dispersive fiber (e.g., DCF)

13. Experimental Setup

14. Experimental Results NRZ delayed signal at 10 Gb/s Up to 400 ps delay achieved by tuning the pump for 3 nm

15. Experimental Results 10 Gb/s 231-1 PRBS

16. Experimental Results 10 Gb/s 231-1 PRBS

17. Experimental Results 10 Gb/s 231-1 PRBS

18. Multi-FunctionalTunable Optical Delay Objective: Develop approach for tunable optical delay and signal regeneration Reduce amplitude noise for DPSK signals Approach: Exploit regenerative properties of four-wave mixing in semiconductor optical amplifiers

19. Experimental Setup

20. Experimental Results

21. All-Optical Clock Recovery

22. Clock Recovery Often overlooked function in any optical transciever or optical regenerator Necessary to provide a synchronization signal for sampling, switching, and 3R regeneration

23. Approaches Electronic: fast photodetection followed by electronic clock recovery circuit (i.e., phase lock loop and a VCO) Optical: spectral filtering, self-pulsating semiconductor lasers, fiber lasers, optical nonlinearities Hybrid

24. Clock Recovery Flexible and robust High-speed: capable of operating on payloads at 10 Gb/s and beyond Conventional or burst-mode operation: suitable for circuit-switched or packet-switched transmission High tolerance: to variability in power levels of input signals or density of logical 0 data bits Low timing jitter Many of these features can be achieved with all-optical clock recovery

25. All-Optical Clock Recovery Additional considerations Modulation format: NRZ, RZ, DPSK, etc. Polarization Multi-channel operation, i.e., can the same device process multiple channels simultaneously? Sub-harmonic clock recovery for ultrahigh (e.g., beyond 40 Gb/s) payloads

26. Two Approaches Purely passive approach using optical fiber or fiber-based components Temporal Talbot effect Active approach based on a fiber laser Mode-locking using optical nonlinearities

27. Infinite periodic input pulse train propagating through 1st order dispersive medium Individual pulses broaden, overlap, and interfere with each other For specific values of dispersion, interference results in imaged pulses (with same frequency as input or multiplied frequency) Temporal Talbot Effect

28. What happens if we use a finite duration pulse train? Temporal Talbot Effect

29. Temporal Talbot Effect Integer self-imaging with finite pulse trains Effect persists even after input pulse train ends (characterize by the number of pulses nd that it takes for the output amplitude to pass from 90% to 10%)

30. Memory/Buffering with the Temporal Talbot Effect Regular pulse train generation from a PRBS

31. Experimental Demonstration

32. Results No baseline in output All bit slots contain pulses RF baseline drops Some amplitude fluctuations (can be reduced using power limiter)

33. Multi-Channel Clock Recovery

34. Results

35. Reducing the Footprint

36. Results

37. Results

38. Cock Recovery using the Temporal Talbot Effect Talbot effect can generate �missing� pulses Passive Follows the input repetition rate Implementation choice (fiber or gratings) Multi-wavelength operation is possible References D. Pudo, M. Depa, L. R. Chen, M. Ibsen, and D. J. Richardson, "Temporal-Talbot effect based all-optical clock recovery using Bragg gratings," Conference on Lasers and Electro-Optics Europe, Munich, Germany, 2007 D. Pudo, M. Depa, and L. R. Chen, "Single and multi-wavelength all-optical clock recovery in single mode fiber using the temporal Talbot effect," IEEE/OSA J. of Lightwave Technol., 25, 10, pp. 2898-2903, 2008