characterisation of a novel dual-control toad switch
DESCRIPTION
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. Outlines. Introduction - PowerPoint PPT PresentationTRANSCRIPT
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CHARACTERISATION OF CHARACTERISATION OF A NOVEL DUAL-CONTROL TOAD SWITCHA NOVEL DUAL-CONTROL TOAD SWITCH
H Le-Minh, Z Ghassemlooy, and W P NgH Le-Minh, Z Ghassemlooy, and W P Ng
Optical Communications Research GroupOptical Communications Research GroupSchool of Informatics, Engineering & TechnologySchool of Informatics, Engineering & Technology
Northumbria University, Newcastle, UKNorthumbria University, Newcastle, UK
Lancaster, 30/03 – 01/04/2005
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OutlinesOutlines
IntroductionIntroduction
All-optical switchesAll-optical switches
TOAD switch: single & dual controlTOAD switch: single & dual control
Numerical modeling of SOANumerical modeling of SOA
Simulation ResultsSimulation Results
ConclusionsConclusions
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IntroductionIntroduction
To enhance high-capacity optical networkTo enhance high-capacity optical network
– Multiplexing: DWDM and OTDMMultiplexing: DWDM and OTDM» Higher channel capacity (higher aggregate bit rate)Higher channel capacity (higher aggregate bit rate)
– All optical switching: All optical switching: » Optical transparency: removing O-E-O conversionsOptical transparency: removing O-E-O conversions
Need an ultra-fast all-optical switches
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All-Optical SwitchesAll-Optical Switches
Are based on:Are based on:
Nonlinear effect + optical interferometerNonlinear effect + optical interferometer
Configurations:Configurations:» Nonlinear Optical Loop Mirror (NOLM)Nonlinear Optical Loop Mirror (NOLM)
» Terahertz Optical Asymmetric Demultiplexer (TOAD)Terahertz Optical Asymmetric Demultiplexer (TOAD)
» Symmetric Mach-Zehnder (SMZ)Symmetric Mach-Zehnder (SMZ)
» Ultrafast Nonlinear Interferometer (UNI)Ultrafast Nonlinear Interferometer (UNI)
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TOAD SwitchTOAD Switch
• Short fibre loop as the optical interferometer: by the CW & CCW data components
Input Data
Reflected D
ata
CW CCW
SOA
a0o 0.707a0o
0.707a90o
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Tasym
TOAD switchTOAD switch
• Short fibre loop as the optical interferometer: by the CW & CCW data components
• Semiconductor Optical Amplifier (SOA) induces nonlinearity
ttGtGtGtGtG CCWCWCCWCWTOAD cos24
1
tG
tGt
CW
CCWln2
Input Data
Transmitted Data
CW CCW
SOA
Control pulse (CP) saturates SOA
Switching window width is defined by the Tasym
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TOAD switchTOAD 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
1. High inter-channel crosstalk
2. Distorted signal pulse shape
Input Data Control pulse (CP)
Transmitted Data
CW CCW
SOA
Output
(Transmitted)
Input Switched
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TOAD: Asymmetric Switching WindowTOAD: Asymmetric Switching Window
CP
4 3 2 1
1 2 3 4
CW direction
CCW direction
0 x LSOA
LSOA – x
Single CP
1
CW directionNo effected by CP ( fully amplified after exiting SOA
Follows CP ( experience full saturation effect after exiting SOA
Same as pulse (3) if TSOA_recovery >> TSOA
CCW direction
2
3
4
1
This pulse meets CP at x/2 ( experienced saturation effects of SOA segments up to x/2
2Experienced more partial saturation effect than pulse (1)
3Experienced more partial saturation effect than pulses (1), (2)
4
Any pulse following pulse (4) will experience the full saturation effect until SOA carrier density recovers
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TOAD: Asymmetric Switching Window –TOAD: Asymmetric Switching Window –contd.contd.
1
CW directionNo effected by CP ( fully amplified after exiting SOA
Follows CP ( experience full saturation effect after exiting SOA
Same as pulse (3) if TSOA_recovery >> TSOA
CCW direction
2
3
4
1
This pulse meets CP at x/2 ( experienced saturation effects of SOA segments up to x/2
2Experienced more partial saturation effect than pulse (1)
3Experienced more partial saturation effect than pulses (1), (2)
4
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
CP
4 3 2 1
1 2 3 4
CW direction
CCW direction
0 x LSOA
LSOA – x
Single CP
GCW(t)
GCCW(t)
Gain
Time
Tasym
SW
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TOAD: Symmetric Switching WindowTOAD: Symmetric Switching Window
• Cascading two TOAD switches (Prucnal’02)
• Using dual-control in single TOAD switch
SW1SW2
Input Data
CP CCW
Transmitted Data
CW CCW
SOA
CP
CW
• 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 TOAD: Symmetric Switching Window with Dual Control PulsesControl Pulses
CW direction
1Pulses before (1) do not meet CPCCW ( experience full amplification
2 Partial saturation by CPCCW
3 More partial saturation by CPCCW
4
If x<LSOA/2, affected by CPCW
( saturated by segments up to LSOA/2
If x>LSOA/2, segments from LSOA/2 to LSOA are further saturated by CPCW and CPCCW
5Pulses after (5) experience full double saturation of SOA when all CPs exit
CCW direction
CPCW
4 3 2
1 3 4 5
CW direction
CCW direction
0 LSOA
1.5LSOA
Dual-CP
CPCCW
1
x LSOA – x
LSOA + x
- x
5
- LSOA/2
2
The effects on CCW data pulses are exactly same as in CW direction!
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TOAD: Symmetric Switching Window with Dual TOAD: Symmetric Switching Window with Dual Control PulsesControl Pulses
CW direction
1Pulses before (1) do not meet CPCCW ( experience full amplification
2 Partial saturation by CPCCW
3 More partial saturation by CPCCW
4
If x<LSOA/2, affected by CPCW
( saturated by segments up to LSOA/2
If x>LSOA/2, segments from LSOA/2 to LSOA are further saturated by CPCW and CPCCW
5Pulses after (5) experience full double saturation of SOA when all CPs exit
CCW direction
The effects on CCW data pulses are exactly the same as in CW direction!
CPCW
4 3 2
1 3 4 5
CW direction
CCW direction
0 LSOA
1.5LSOA
Dual-CP
CPCCW
1
x LSOA – x
LSOA + x
- x
5
- LSOA/2
2
Gain
GCW(t)
GCCW(t)Time
SWTasym
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Modeling of SOAModeling of SOA
( )( ) ( )( ) ( )
( ) ( ) ( )
11
1
, ,,,
, , ,
m T tot mmem
SOA e SOA p
m m m
g N k t N P k tN k tIN k t t
qV A E
N k t N k t N k t
t--
-
é ùG -ê úD = - - Dê ú
ê úê úë û
= +D
k
k - 1 k +
1
( ) ( ) ( )( )( ) ( ) ( )( )
( ) ( ) ( )
1 1
1 1
, 1, exp 1,
, 1, exp 1,
, , ,
cw m cw m m T
ccw m ccw m m T
tot m cw m ccw m
P k t P k t g N k t N L
P k t P k t g N k t N L
P k t P k t P k t
- -
- -
é ù= - G - - Dê úë û
é ù= + G + - Dê úë û
= +
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 ISimulation Results I
Dual control: create the steep transitions in the temporal gain profiles ( help to create the steep switching window edges
Gain profiles and switching windows
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Simulation Results IISimulation Results II
Carrier density in SOA when single control pulse going through
Time angle
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Simulation Results IIISimulation Results III
SOA carrier density with both control pulses propagating within the SOA
Time angle
Single control
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Simulation Results IVSimulation Results IV
Dual control: induce less inter-channel crosstalk and less pulse-shape distortion of switched pulse
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ConclusionsConclusions
Using dual-control pulses in a TOAD Using dual-control pulses in a TOAD configuration symmetric switching window configuration symmetric switching window profile is obtainedprofile is obtained
Inter-channel crosstalk and distortion of Inter-channel crosstalk and distortion of switched pulse are reducedswitched pulse are reduced
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Thank you.Thank you.
Question please?Question please?