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 Active 2002 , ISVR Univ. of Southampton UK

Outlines All-optical switches TOAD switch Simulation Results Introduction All-optical switches TOAD switch Simulation Results Conclusions Active 2002 , ISVR Univ. of Southampton UK

Introduction How to enhance high-capacity optical network? Active 2002 , ISVR Univ. of Southampton UK

Introduction How to enhance high-capacity optical network? Multiplexing Wavelength Division Multiplexing (WDM) Time Division Multiplexing (TDM) Active 2002 , ISVR Univ. of Southampton UK

Introduction How to enhance high-capacity optical network? Multiplexing Wavelength Division Multiplexing (WDM) Time Division Multiplexing (TDM) Removing the O/E/O conversions bottleneck Active 2002 , ISVR Univ. of Southampton UK

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 Active 2002 , ISVR Univ. of Southampton UK

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 Active 2002 , ISVR Univ. of Southampton UK

All-optical Switches Mechanism: Exploiting the combination of destructive interferences introduced by nonlinearity element to switch/demultiplex target data Active 2002 , ISVR Univ. of Southampton UK

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) … Active 2002 , ISVR Univ. of Southampton UK

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) … Active 2002 , ISVR Univ. of Southampton UK

All-optical Switches: NOLM Nonlinear Optical Loop Mirror (NOLM) CP 50:50 CW CCW Input port Output 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 CW CCW Input port Output 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 CW CCW Input port Output 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: 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

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

TOAD: Single Control Pulse Effects data CW and CCW components passing through SOA Case 1: No CP 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 amplified Fully amplified

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 Case 2: With CP applied to the SOA in CW direction SOA CW CCW SOA CW CCW Data will experience full-gain amplification prior to CP being applied 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 2: With CP applied to the SOA in CW direction 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 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 2: With CP applied to the SOA in CW direction SOA CW CCW 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 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 2TSOA is partly saturated

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 2TSOA is partly saturated Full saturation

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

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

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

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

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 Case 1: CP1 and CP2 entering SOA SOA CW CCW CP1 CP2 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 Partly amplified Fully amplified Co-propagating saturation Counter-propagating saturation

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

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

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

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

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

TOAD: Dual Control Pulses Case 3: CP1 and CP2 exit the SOA SOA CW CCW CP1 CP2 G ( 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) Fullly amplified Fully saturated Co-propagating saturation Counter-propagating saturation

TOAD: Dual Control Pulses Case 3: CP1 and CP2 exit the SOA SOA CW CCW CP1 CP2 G ( 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) Fullly amplified Fully saturated Co-propagating saturation Counter-propagating saturation

TOAD: Dual Control Pulses Case 3: CP1 and CP2 exit the SOA SOA CW CCW CP1 CP2 G ( 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) Fullly amplified Fully saturated Co-propagating saturation Counter-propagating saturation

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

Simulation Results Main parameters Parameters Values SOA length 500 m   Simulation Results Main parameters 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: Switching window Gain profiles and corresponding TOAD switching window Improved switching window by using dual control pulses

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

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

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

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.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