H' LeMinh, Z' Ghassemlooy, W'P' Ng' and R' Ngah

1
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
2
Outlines

• Introduction
• All-optical switches
• TOAD switch
• Simulation Results
• Conclusions

3
Introduction

• How to enhance high-capacity optical network?

4
Introduction

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

5
Introduction

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

6
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

7
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

8
All-optical Switches

• Mechanism
• Exploiting the combination of destructive
  interferences introduced by nonlinearity element
  to switch/demultiplex target data

9
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)

10
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)

11
All-optical Switches NOLM

• Nonlinear Optical Loop Mirror (NOLM)

• Long fibre loop to induce the nonlinearity
• Non-integrated capability
• High control pulse (CP) energy

12
All-optical Switches TOAD

• Terahertz Optical Asymmetric Demultiplexer
  (TOAD)

• 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

13
All-optical Switches TOAD

• Terahertz Optical Asymmetric Demultiplexer
  (TOAD)

• 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

14
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

15
TOAD Single Control Pulse

• Effects data CW and CCW components passing
  through SOA
• Case 1 No CP

Data propagating in SOA experience partial-gain
amplification
16
TOAD Single Control Pulse
Effects data CW and CCW components passing
through SOA Case 1 No CP
Data propagating in SOA experience partial-gain
amplification
After passing full-length SOA, data experience
full-gain amplification
17
TOAD Single Control Pulse

• Case 2 With CP applied to the SOA in CW direction

18
TOAD Single Control Pulse
Case 2 With CP applied to the SOA in CW direction
Data will experience full-gain amplification
prior to CP being applied
19
TOAD Single Control Pulse
Case 2 With CP applied to the SOA in CW direction
Data will experience full-gain amplification
prior to CP being applied
Data seeing saturated part of SOA will experience
partial saturation
20
TOAD Single Control Pulse
Case 2 With CP applied to the SOA in CW direction
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
21
TOAD Single Control Pulse

• Case 3 CP exited the SOA

Part of transitional period 2TSOA is partly
saturated
22
TOAD Single Control Pulse
Case 3 CP exited the SOA
Part of transitional period 2TSOA is partly
saturated
Full saturation
23
TOAD Single Control Pulse
Case 3 CP exited the SOA
Different transitional effects on CW CCW
Different effects on CW CCW
24
TOAD Single Control Pulse
Case 3 CP exited the SOA
2TSOA
25
TOAD Single Control Pulse
Case 3 CP exited the SOA
2TSOA
? Dependent on the SOA length
26
TOAD Single Control Pulse
Case 3 CP exited the SOA
2TSOA
Issues Triangle CW CCW gain-profiles. Thus
Asymmetric switching window!
27
TOAD Dual Control Pulses

• Both control pulses simultaneously excite SOA
  from both directions.

• Lower inter-channel crosstalk
• Symmetrical switching window profile

28
TOAD Dual Control Pulses

• Case 1 CP1 and CP2 entering SOA

29
TOAD Dual Control Pulses
Case 1 CP1 and CP2 entering SOA
CCW data counter-propagate with CP1 will receive
partial saturation
CCW data co-propagate with CP2 will receive full
saturation
30
TOAD Dual Control Pulses
Case 1 CP1 and CP2 entering SOA
Similar effects on CW
Similar effects on CW CCW
31
TOAD Dual Control Pulses

• Case 2 CP1 and CP2 passing each other within the
  SOA

At the kth segment of the SOA, where CP2 arrives
32
TOAD Dual Control Pulses
Case 2 CP1 and CP2 passing each other within the
SOA
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

33
TOAD Dual Control Pulses
Case 2 CP1 and CP2 passing each other within the
SOA
34
TOAD Dual Control Pulses
Case 2 CP1 and CP2 passing each other within the
SOA
Segment kth may have more gain saturation
35
TOAD Dual Control Pulses
Case 3 CP1 and CP2 exit the SOA

G

0
(
A
)

CW

or
CCW

(
B
)

gain
-

profile

(
C
)

(
D
)


G
SAT
Time

Part of TSOA CCW has partial saturation (A)
36
TOAD Dual Control Pulses
Case 3 CP1 and CP2 exit the SOA

G

0
(
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)
37
TOAD Dual Control Pulses
Case 3 CP1 and CP2 exit the SOA

G

0
(
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)
38
TOAD Dual Control Pulses
Case 3 CP1 and CP2 exit the SOA

G

0
(
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)
39
TOAD Dual Control Pulses
Case 3 CP1 and CP2 exit the SOA



CW



CCW

gain
-

profiles





Time

Steep CW CCW gain-profiles ? Symmetric
switching window
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Simulation Results
 

• Main parameters

41
Simulation Results Switching window

• Gain profiles and corresponding TOAD switching
  window

Improved switching window by using dual control
pulses
42
Simulation Results Multiple Switching Windows

• Dual control pulses
• Constant CP power
• Variable Tasym
• TSOA 6ps

Need optimum power of CPs for each switching
interval
43
Simulation Results Imperfect dual controls

• Different power ratio of CP2/CP1
• Tasym 2ps

Impairment of CP1s and CP2s power ? Asymmetric
switching window
44
Simulation Results Imperfect dual controls

• CP2 arrives late in comparison with CP1
• Tasym 2ps
• TSOA 6ps

Impairment of CP1s and CP2s arrivals ?
Severely bad switching window profiles
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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

46
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

47
Thank you

• Thank you!

48
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