Crosstalk suppression in an alloptical symmetric MachZehnder SMZ switch employing unequal control pu

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Crosstalk suppression in an all-optical symmetric
Mach-Zehnder (SMZ) switch employing un-equal
control pulses

• Hoa Le Minh, Fary Z Ghassemlooy and
• Wai Pang Ng
• Optical Communications Research Group
• Northumbria Communications Research Lab
• Northumbria University, U.K.

International Symposium on Telecommunications,
Sep. 10-12, 2005, Shiraz, Iran
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Contents

• Introduction
• All-optical Switches
• Symmetric Mach Zehnder Switch (SMZ)
• Simulation Results
• Conclusions

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Introduction

• Ultra-high capacity optical network relies on
• Multiplexing DWDM and OTDM
• Higher aggregate bit rate
• Optical transparency
• Removing Opt.-Elec.-Opt. conversions (bottleneck)
  in routing, demultpelxing and processing tasks

The need ultra-fast all-optical switches
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All-optical Switches

• Mechanism
• Exploiting the destructive interferences
  introduced by the non-linearity element (based on
  XPM) to switch/demultiplex target data
• Configurations
• Loop based
• 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)

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All-optical Switches contd.

• I- Nonlinear Optical Loop Mirror (NOLM)

Transmission is

• If ?? ?, then Tx (t) 1 (i.e.100
• transmittance in port 2)

• Polarisation
• Long walk-off time

• Long fibre loop to induce the nonlinearity (but
  weak and not easily controllable)
• High control pulse (CP) power

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All-optical Switches contd.

• II- Terahertz Optical Asymmetric Demultiplexer
  (TOAD)

• Introduced by P. Prucnal (1993)
• Nonlinearity Semiconductor Optical
• Amplifier (SOA)
• Low control pulse (CP) power
• High inter-channel crosstalk
• Asymmetrical switching window profile
• Synchronisation

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SMZ Switch

• An optical interferometer with two identical arms
  
• Semiconductor Optical Amplifier (SOA) induce
  non-linear effect (XPM) on input data signal
• Compact, requiring low optical power

(i) No control pulses
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SMZ Switch With Control
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SMZ Switching Window

• Switching window profile at output port 1

(?LEF SOA linewidth enhancement factor)
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SMZ - Switching Window

• Problem
• The switching window W1(t) will not completely
  close due to the difference of G1(t) and G2(t) in
  the recovery region. This is due to CP1 CP2
  thus setting both SOAs at the same initial
  saturation levels.

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SMZ With Unequal Control Power

• Make CP2 lt CP1 to minimize the recovery gain
  difference.
• Reduction ratio R(dB) CP1(dB) CP2(dB)

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SMZ - Simulation Model
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SMZ - Simulation Parameters
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SMA - Simulation Results

• Inter-channel crosstalk

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SMZ - Simulation Results CP1 CP2
Eye diagram (_at_ BER 10-9)

• Data at output port 1

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SMA - Simulation Results CP2 lt CP1

• R 0.6 dB,
• Reduced interchannel crosstalk
• Improved eye opening, ?improved bit error rate

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SMZ BER Simulation Results
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Conclusions

• Proposed SMZ switch with unequal control pulse
  powers with improved recovery gain profile.
• Simulation model confirmed
• Improved crosstalk characteristic
• Improved optical receiver sensitivity up to 1.7
  dB at BER 10-9
• Reduced total control signal power

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Acknowledgments

• This research project is sponsored by the
  Northumbria University, Newcastle upon Tyne, UK

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• Thank you.