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H. Le-Minh, Z. Ghassemlooy, W.P. Ng. and R. Ngah Optical Communication Research Group

TOAD Switch with Symmetric Switching Window. H. Le-Minh, Z. Ghassemlooy, W.P. Ng. and R. Ngah Optical Communication Research Group School of Engineering & Technology Northumbria University, Newcastle, UK http://soe.unn.ac.uk/ocr/. London Communications Symposium 2004, Sept. 13 th – 14 th.

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H. Le-Minh, Z. Ghassemlooy, W.P. Ng. and R. Ngah Optical Communication Research Group

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  1. TOAD Switch with Symmetric Switching Window H. Le-Minh, Z. Ghassemlooy, W.P. Ng. and R. Ngah Optical Communication Research Group School of Engineering & Technology Northumbria University, Newcastle, UK http://soe.unn.ac.uk/ocr/ London Communications Symposium 2004, Sept. 13th – 14th

  2. Outlines • Introduction • All-optical switches • TOAD switch • Simulation Results • Conclusions

  3. Introduction • How to enhance high-capacity optical network?

  4. Introduction • How to enhance high-capacity optical network? • Multiplexing • Wavelength Division Multiplexing (WDM) • Time Division Multiplexing (TDM)

  5. Introduction • How to enhance high-capacity optical network? • Multiplexing • Wavelength Division Multiplexing (WDM) • Time Division Multiplexing (TDM) • Removing the O/E/O conversions bottleneck

  6. Introduction • How to enhance high-capacity optical network? • Multiplexing • Wavelength Division Multiplexing (WDM) • Time Division Multiplexing (TDM) • Removing the O/E/O conversions bottleneck • All optical processing

  7. Introduction • How to enhance high-capacity optical network? • Multiplexing • Wavelength Division Multiplexing (WDM) • Time Division Multiplexing (TDM) • Removing the O/E/O conversions bottleneck • All optical processing: e.g. OTDM + all-optical switch

  8. All-optical Switches • Mechanism: Exploiting the combination of destructive interferences introduced by nonlinearity element to switch/demultiplex target data

  9. All-optical Switches • Mechanism: Exploiting the combination of destructive interferences introduced by nonlinearity element to switch/demultiplex target data • Configurations: • Loop • Nonlinear Optical Loop Mirror (NOLM) • Semiconductor Laser Amplifier in a Loop Mirror (SLALOM) • Terahertz Optical Asymmetric Demultiplexer (TOAD) • Others • Ultrafast Nonlinear Interferometer (UNI) • Symmetric Mach-Zehnder (SMZ) • …

  10. All-optical Switches • Mechanism: Exploiting the combination of destructive interferences introduced by nonlinearity element to switch/demultiplex target data • Configurations: • Loop • Nonlinear Optical Loop Mirror (NOLM) • Semiconductor Laser Amplifier in a Loop Mirror (SLALOM) • Terahertz Optical Asymmetric Demultiplexer (TOAD) • Others • Ultrafast Nonlinear Interferometer (UNI) • Symmetric Mach-Zehnder (SMZ) • …

  11. Long loop CW CCW CP 50:50 Input port Output port Switched data Data in Reflected port Reflected data All-optical Switches: NOLM Nonlinear Optical Loop Mirror (NOLM) • Long fibre loop to induce the nonlinearity • Non-integrated capability • High control pulse (CP) energy

  12. SOA Fibre loop CW CCW CP 50:50 Input port Output port Switched data Data in Reflected port Reflected data All-optical Switches: TOAD Terahertz Optical Asymmetric Demultiplexer (TOAD) • Introduced by P. Prucnal (1993) • Only Semiconductor Optical Amplifier (SOA) induces nonlinearity • Possible to integrate in chip • Low control pulse (CP) energy • High inter-channel crosstalk • Asymmetrical switching window profile

  13. SOA Fibre loop CW CCW CP 50:50 Input port Output port Switched data Data in Reflected port Reflected data All-optical Switches: TOAD Terahertz Optical Asymmetric Demultiplexer (TOAD) • Introduced by P. Prucnal (1993) • Only Semiconductor Optical Amplifier (SOA) induces nonlinearity • Possible to integrate in chip • Low control pulse (CP) energy • High inter-channel crosstalk • Asymmetrical switching window profile

  14. TOAD: Switching Window Profile It mainly depends on the gains and phase as: • GCW(t) and GCCW(t) are the temporal gain-profiles of CW and CCW data components • (t) is the temporal phase difference between CW and CCW components •  is the linewidth enhancement factor

  15. SOA CW CCW Partly amplified SOA Fibre loop CW CCW CP 50:50 Input port Output port Switched data Data in Reflected port Reflected data TOAD: Single Control Pulse Effects data CW and CCW components passing through SOA Case 1: No CP Data propagating in SOA experience partial-gain amplification

  16. SOA CW SOA CCW CW CCW Partly amplified Fully amplified TOAD: Single Control Pulse Effects data CW and CCW components passing through SOA Case 1: No CP Data propagating in SOA experience partial-gain amplification After passing full-length SOA, data experience full-gain amplification

  17. SOA CW CCW Partly amplified Fully amplified TOAD: Single Control Pulse Case 2: With CP applied to the SOA in CW direction

  18. SOA SOA CW CW CCW CCW Co-propagating saturation (Will experience full saturation when data exits SOA) Partly amplified Counter-propagating saturation (Will not experience full saturation when data exits SOA) Fully amplified TOAD: Single Control Pulse Case 2: With CP applied to the SOA in CW direction Data will experience full-gain amplification prior to CP being applied

  19. SOA SOA CW CW CCW CCW Co-propagating saturation (Will experience full saturation when data exits SOA) Partly amplified Counter-propagating saturation (Will not experience full saturation when data exits SOA) Fully amplified TOAD: Single Control Pulse Case 2: With CP applied to the SOA in CW direction Data will experience full-gain amplification prior to CP being applied Data seeing saturated part of SOA will experience partial saturation

  20. SOA CW CCW Co-propagating saturation (Will experience full saturation when data exits SOA) Partly amplified Counter-propagating saturation (Will not experience full saturation when data exits SOA) Fully amplified TOAD: Single Control Pulse Case 2: With CP applied to the SOA in CW direction SOA CW CCW More saturation Data well before entering of CP to SOA will experience full-gain amplification Data seeing saturated part of SOA will experience partial saturation

  21. SOA CW CCW Fully amplified Co-propagating saturation Fully saturated Counter-propagating saturation TOAD: Single Control Pulse Case 3: CP exited the SOA Part of transitional period 2TSOA is partly saturated

  22. SOA CW CCW Fully amplified Co-propagating saturation Fully saturated Counter-propagating saturation TOAD: Single Control Pulse Case 3: CP exited the SOA Part of transitional period 2TSOA is partly saturated Full saturation

  23. SOA CW CCW Fully amplified Co-propagating saturation Fully saturated Counter-propagating saturation TOAD: Single Control Pulse Case 3: CP exited the SOA Different transitional effects on CW & CCW Different effects on CW & CCW

  24. SOA CW CCW Fully amplified Co-propagating saturation Fully saturated Counter-propagating saturation TOAD: Single Control Pulse Case 3: CP exited the SOA 2TSOA

  25. SOA CW CCW TOAD: Single Control Pulse Case 3: CP exited the SOA 2TSOA Dependent on the SOA length

  26. SOA CW CCW TOAD: Single Control Pulse Case 3: CP exited the SOA 2TSOA Issues: Triangle CW & CCW gain-profiles. Thus Asymmetric switching window!

  27. TOAD: Dual Control Pulses Both control pulses simultaneously excite SOA from both directions. • Lower inter-channel crosstalk • Symmetrical switching window profile

  28. SOA CW CCW CP1 CP2 Partly amplified Fully amplified TOAD: Dual Control Pulses Case 1: CP1 and CP2 entering SOA

  29. SOA SOA CW CW CCW CCW CP1 CP1 CP2 CP2 Partly amplified Co-propagating saturation Fully amplified Counter-propagating saturation TOAD: Dual Control Pulses Case 1: CP1 and CP2 entering SOA CCW data counter-propagate with CP1 will receive partial saturation CCW data co-propagate with CP2 will receive full saturation

  30. SOA SOA CW CW CCW CCW CP1 CP1 CP2 CP2 Partly amplified Co-propagating saturation Fully amplified Counter-propagating saturation TOAD: Dual Control Pulses Case 1: CP1 and CP2 entering SOA Similar effects on CW & CCW Similar effects on CW

  31. SOA CW CCW CP2 CP1 Co-propagating saturation Fully amplified Counter-propagating saturation TOAD: Dual Control Pulses Case 2: CP1 and CP2 passing each other within the SOA At the kth segment of the SOA, where CP2 arrives

  32. SOA CW CCW CP2 CP1 Co-propagating saturation Fully amplified Counter-propagating saturation TOAD: Dual Control Pulses Case 2: CP1 and CP2 passing each other within the SOA At the kth segment of the SOA, where CP2 arrives • CP1 saturates the kth segment and leaves • The segment-gain begins recovering after CP1 exited • With the arrival of CP2, the kth segment is forced into saturation

  33. SOA SOA CW CW CCW CCW CP2 CP2 CP1 CP1 Co-propagating saturation Fully amplified Counter-propagating saturation TOAD: Dual Control Pulses Case 2: CP1 and CP2 passing each other within the SOA

  34. SOA SOA CW CW CCW CCW CP2 CP2 CP1 CP1 Co-propagating saturation Fully amplified Counter-propagating saturation TOAD: Dual Control Pulses Case 2: CP1 and CP2 passing each other within the SOA Segment kth may have more gain saturation

  35. SOA CW CCW CP2 CP1 Fullly amplified Co-propagating saturation Fully saturated Counter-propagating saturation TOAD: Dual Control Pulses Case 3: CP1 and CP2 exit the SOA G 0 A ( ) CW or CCW B ( ) gain - profile C D ( ) ( ) G SAT Time Part of TSOA CCW has partial saturation (A)

  36. SOA CW CCW CP2 CP1 Fullly amplified Co-propagating saturation Fully saturated Counter-propagating saturation TOAD: Dual Control Pulses Case 3: CP1 and CP2 exit the SOA G 0 A ( ) CW or CCW B ( ) gain - profile C D ( ) ( ) G SAT Time Part of TSOA CCW has partial saturation + deeper saturation (C) Part of TSOA CCW has partial saturation (A)

  37. SOA CW CCW CP2 CP1 Fullly amplified Co-propagating saturation Fully saturated Counter-propagating saturation TOAD: Dual Control Pulses Case 3: CP1 and CP2 exit the SOA G 0 A ( ) CW or CCW B ( ) gain - profile C D ( ) ( ) G SAT Time Part of TSOA CCW has partial saturation + deeper saturation (C) Part of TSOA CCW has partial saturation (A) Steep transitional region (B)

  38. SOA CW CCW CP2 CP1 Fullly amplified Co-propagating saturation Fully saturated Counter-propagating saturation TOAD: Dual Control Pulses Case 3: CP1 and CP2 exit the SOA G 0 A ( ) CW or CCW B ( ) gain - profile C D ( ) ( ) G SAT Time Part of TSOA CCW has partial saturation + deeper saturation (C) Part of TSOA CCW has partial saturation (A) Then full saturation (D) Steep transitional region (B)

  39. SOA CW CCW CP2 CP1 Fullly amplified Co-propagating saturation Fully saturated Counter-propagating saturation TOAD: Dual Control Pulses Case 3: CP1 and CP2 exit the SOA CW & CCW gain - profiles Time Steep CW & CCW gain-profiles Symmetric switching window

  40. Parameters Values SOA length 500 m SOA spontaneous lifetime 100 ps SOA confinement factor 0.3 SOA transparent carrier density 1024 m-3 SOA line-width enhancement 4 SOA active area 3x10-13 m2 SOA differential gain 2x10-20 m2 Number of SOA segments 100 Control pulse width (FWHM) 1 ps Single control pulse power (PCP) 1 W Dual control pulse power (PCP1= PCP2) 0.5 W per CP Asymmetric SOA placement Tasym 2 ps Simulation Results Main parameters

  41. Simulation Results: Switching window Gain profiles and corresponding TOAD switching window Improved switching window by using dual control pulses

  42. Simulation Results: Multiple Switching Windows • Dual control pulses • Constant CP power • Variable Tasym • TSOA = 6ps Need optimum power of CPs for each switching interval

  43. Simulation Results: Imperfect dual controls • Different power ratio of CP2/CP1 • Tasym = 2ps Impairment of CP1’s and CP2’s power  Asymmetric switching window

  44. CP2 arrives late in comparison with CP1 Tasym = 2ps TSOA = 6ps Simulation Results: Imperfect dual controls Impairment of CP1’s and CP2’s arrivals  Severely bad switching window profiles

  45. Conclusions: TOAD with dual controls • Achieved narrow and symmetric switching window, which will result in reduced crosstalk. • The switching window is independent of the SOA length, and only depends on the SOA offset • Promising all-optical switch for future ultra-fast photonic networks

  46. Acknowledgments • The authors would like to thank the Northumbria University for sponsoring this research • Thanks also for my supervisor team for guiding the research and contributing helpful discussions

  47. Thank you Thank you!

  48. References [1] J. P. Sokoloff, P. R. Prucnal, I. Glesk, and M. Kane, “A Terahertz optical asymmetric demultiplexer (TOAD)”, IEEE Photon. Technol. Lett., 5 (7), pp.787-790, 1993 [2] M. Eiselt, W. Pieper, and H. G. Weber, ”SLALOM: Semiconductor Laser Amplifier in a Loop Mirror”, IEEE J. Light. Tech. 13 (10), pp. 2099-2112, 1995 [3] G. Swift, Z. Ghassemlooy, A. K. Ray, and J. R. Travis, “Modelling of semiconductor laser amplifier for the terahertz optical asymmetric demultiplexer”, IEE Proc. Circ. Devi. Syst. 145 (2), pp. 61-65, 1998

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