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

Outlines Introduction All-optical switches TOAD switch Simulation Results Conclusions

Introduction How to enhance high-capacity optical network?

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

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

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

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

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

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) …

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) …

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

All-optical Switches: TOAD Terahertz Optical Asymmetric Demultiplexer (TOAD) CP SOA 50:50 CWCCW Input portOutput port Reflected port Fibre loop Data in Reflected data Switched data 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

All-optical Switches: TOAD Terahertz Optical Asymmetric Demultiplexer (TOAD) CP SOA 50:50 CWCCW Input portOutput port Reflected port Fibre loop Data in Reflected data Switched data 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

TOAD: Switching Window Profile It mainly depends on the gains and phase as: G CW (t) and G CCW (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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Simulation Results Main parameters ParametersValues SOA length 500  m SOA spontaneous lifetime100 ps SOA confinement factor0.3 SOA transparent carrier density10 24 m -3 SOA line-width enhancement4 SOA active area3x m 2 SOA differential gain2x m 2 Number of SOA segments100 Control pulse width (FWHM)1 ps Single control pulse power (P CP )1 W Dual control pulse power (P CP1 = P CP2 )0.5 W per CP Asymmetric SOA placement T asym 2 ps

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

Simulation Results: Multiple Switching Windows Dual control pulses Constant CP power Variable T asym T SOA = 6ps Need optimum power of CPs for each switching interval

Simulation Results: Imperfect dual controls Different power ratio of CP2/CP1 T asym = 2ps Impairment of CP1’s and CP2’s power  Asymmetric switching window

Simulation Results: Imperfect dual controls Impairment of CP1’s and CP2’s arrivals  Severely bad switching window profiles CP2 arrives late in comparison with CP1 T asym = 2ps T SOA = 6ps

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

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

Thank you Thank you!

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 , 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 , 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 , 1998