CHARACTERISATION OF A NOVEL DUALCONTROL TOAD SWITCH - PowerPoint PPT Presentation

Title: CHARACTERISATION OF A NOVEL DUALCONTROL TOAD SWITCH


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CHARACTERISATION OF A NOVEL DUAL-CONTROL TOAD
SWITCH

• H Le-Minh, Z Ghassemlooy, and W P Ng
• Optical Communications Research Group
• School of Informatics, Engineering Technology
• Northumbria University, Newcastle, UK

Lancaster, 30/03 01/04/2005
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Outlines

• Introduction
• All-optical switches
• TOAD switch single dual control
• Numerical modeling of SOA
• Simulation Results
• Conclusions

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Introduction

• To enhance high-capacity optical network
• Multiplexing DWDM and OTDM
• Higher channel capacity (higher aggregate bit
  rate)
• All optical switching
• Optical transparency removing O-E-O conversions

Need an ultra-fast all-optical switches
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All-Optical Switches

• Are based on
• Nonlinear effect optical interferometer
• Configurations
• Nonlinear Optical Loop Mirror (NOLM)
• Terahertz Optical Asymmetric Demultiplexer (TOAD)
• Symmetric Mach-Zehnder (SMZ)
• Ultrafast Nonlinear Interferometer (UNI)

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TOAD Switch

• Short fibre loop as the optical interferometer
  by the CW CCW data components

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TOAD switch

• Short fibre loop as the optical interferometer
  by the CW CCW data components
• Semiconductor Optical Amplifier (SOA) induces
  nonlinearity

Switching window width is defined by the Tasym
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TOAD switch

• Short fibre loop (1 m) used as the optical
  interferometer by the CW CCW data components
• Semiconductor Optical Amplifier (SOA) induces
  nonlinearity
• Advantages
• Possible to integrate in chip
• Low control pulse (CP) energy
• Disadvantages
• Asymmetric switching window
• High inter-channel crosstalk
• Distorted signal pulse shape

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TOAD Asymmetric Switching Window
x
Single CP
CW direction
0
LSOA
No effected by CP ( fully amplified after exiting
SOA
Follows CP ( experience full saturation effect
after exiting SOA
Same as pulse (3) if TSOA_recovery gtgt TSOA
CCW direction
CW direction
2
4
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1
This pulse meets CP at x/2 ( experienced
saturation effects of SOA segments up to x/2
LSOA x
Experienced more partial saturation effect than
pulse (1)
CCW direction
2
4
1
3
Experienced more partial saturation effect than
pulses (1), (2)
Any pulse following pulse (4) will experience the
full saturation effect until SOA carrier density
recovers
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TOAD Asymmetric Switching Window contd.
CW direction
No effected by CP ( fully amplified after exiting
SOA
Follows CP ( experience full saturation effect
after exiting SOA
Same as pulse (3) if TSOA_recovery gtgt TSOA
CCW direction
This pulse meets CP at x/2 ( experienced
saturation effects of SOA segments up to x/2
Experienced more partial saturation effect than
pulse (1)
Experienced more partial saturation effect than
pulses (1), (2)
Any pulse following pulse (4) will experience the
full saturation effect until SOA carrier density
recovers
Reason Difference of CW and CCW gain profiles
and not steep
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TOAD Symmetric Switching Window

• Cascading two TOAD switches (Prucnal02)
• Using dual-control in single TOAD switch

• CPCW and CPCCW are identical
• CPCW and CPCCW are simultaneously applied to the
  SOA
• Therefore, CW and CCW data components will
  experience the same amplification saturation
  effects
• (GCW(t) and GCCW(t) are the same but delayed

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TOAD Symmetric Switching Window with Dual
Control Pulses
CW direction
Pulses before (1) do not meet CPCCW ( experience
full amplification
Partial saturation by CPCCW
More partial saturation by CPCCW
If xltLSOA/2, affected by CPCW ( saturated by
segments up to LSOA/2 If xgtLSOA/2, segments from
LSOA/2 to LSOA are further saturated by CPCW and
CPCCW
Pulses after (5) experience full double
saturation of SOA when all CPs exit
CCW direction
The effects on CCW data pulses are exactly same
as in CW direction!
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TOAD Symmetric Switching Window with Dual
Control Pulses
CW direction
Pulses before (1) do not meet CPCCW ( experience
full amplification
Partial saturation by CPCCW
More partial saturation by CPCCW
If xltLSOA/2, affected by CPCW ( saturated by
segments up to LSOA/2 If xgtLSOA/2, segments from
LSOA/2 to LSOA are further saturated by CPCW and
CPCCW
Pulses after (5) experience full double
saturation of SOA when all CPs exit
Gain
CCW direction
The effects on CCW data pulses are exactly the
same as in CW direction!
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Modeling of SOA
1. SOA is divided into a number of small segments
2. At each segment, e.g. kth, the arriving powers
are from CW CCW directions
3. The carrier density at each segment is
consequently updated by
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Simulation Results I
Gain profiles and switching windows
Dual control create the steep transitions in the
temporal gain profiles ( help to create the steep
switching window edges
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Simulation Results II
Carrier density in SOA when single control pulse
going through
Time angle
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Simulation Results III
SOA carrier density with both control pulses
propagating within the SOA
Single control
Time angle
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Simulation Results IV
Dual control induce less inter-channel crosstalk
and less pulse-shape distortion of switched pulse
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Conclusions

• Using dual-control pulses in a TOAD configuration
  symmetric switching window profile is obtained
• Inter-channel crosstalk and distortion of
  switched pulse are reduced

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• Thank you.
• Question please?