An Ultrafast with High Contrast Ratio 12 All-optical Switch based on Tri-arm Mach-

Zehnder Employing All-optical Flip-flop

An Ultrafast with High Contrast Ratio 12 All-optical Switch based on Tri-arm Mach-

Zehnder Employing All-optical Flip-flop

H. Le Minh, Z. Ghassemlooy and W. P. NgOptical Communications Research Group

NCRLab, School of CEIS,

Northumbria University, Newcastle, UK

IEEEIEEE ICC 2007 Glasgow, 24-28 June 2007 ICC 2007 Glasgow, 24-28 June 2007

IEEE ICC 07, UK

Presentation OutlinePresentation Outline

1. Optical switches

2. SMZ and Contrast Ratio

3. Tri-arm Mach-Zehnder

4. All-optical flip-flop

5. Results

6. Summary

IEEE ICC 07, UK

IntroductionIntroduction

Edge Router (Ingress/Egress) with 4-bit address XXXX

Core Router

1011

1010 0110

0111

Client Network

Client Network

1001

XXXX

Low-speed packet

Low-speed packet

High-speed packet

Core Network

Optical transparency

• High Bit Rate

• High Throughput

SolutionSolutionUltrafastUltrafast

Switching!Switching!

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Optical SwitchesOptical Switches

MEMSMEMS** (Lucent Tech.)(Lucent Tech.) BubblesBubbles** (Agilent)(Agilent)

TOADTOAD** (Princeton)(Princeton)

SMZSMZ** (Japan)(Japan)

1. Overview1. Overview

Cat.1Cat.1

Large scale (> 1616)

Slow response (s-ms)

Non-optically controlled

Cat.2Cat.2

Small scale (22)

Fast response (fs-ps)

Full-optically controlled• Crosstalk

• Contrast

* Sources: Internet articles & websites

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Symmetric Mach-Zehnder (SMZ)Symmetric Mach-Zehnder (SMZ)

CP1

SOA1

SOA2 CP2

Input Output 1

Output 2

CI CO 0

90

0

9090

00

90

+180+180+180

+180

0

180

0

180180

00

180

+180+180+180

+180

90

90

90

9090

9090

90

+180+180+180

+180

IEEE ICC 07, UK

Symmetric Mach-Zehnder (SMZ)Symmetric Mach-Zehnder (SMZ)

Ideally, all non-target switched signals are zero

CP1

SOA1

SOA2 CP2

Input Output 1

Output 2

CI CO

Non-target Target

ttGtGtGtGtSW 2,121211 cos28

1

ttGtGtGtGtSW 2,121212 cos28

1

tG

tGt LEF

2

12,1 ln

2

1

Practically, non-zero non-target switched signals will penalty the contrast ratio

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SMZ – Contrast RatioSMZ – Contrast Ratio

Switching Contrast Ratios

OP1

OP2

0 5 10 15 20 25 30 35 40-30

-20

-10

0

10

20

30

Power of control signals (dBm)C

Rs

(dB

)

Inter-output CR of OP1/OP

2

Inter-channel CR of OP1

Inter-channel CR of OP2

0 5 10 15 20 25 30 35 40-30

-20

-10

0

10

20

30

Power of control signals (dBm)C

Rs

(dB

)

Inter-output CR of OP1/OP

2

Inter-channel CR of OP1

Inter-channel CR of OP2

A1

A0

B1

B0

Inter-channel CR = A1/A0 , B1/B0

Inter-output CR = A1/B0 , B1/A0

tG

tGt LEF

2

12,1 ln

2

1

SMZ: achieve exact for high CR at OP2

TaMZTaMZ(no need (no need ))

: SOA linewidth enhancement

G1,2: Gain profile in arm 1, 2

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Tri-arm Mach-Zehnder (TaMZ)Tri-arm Mach-Zehnder (TaMZ)

Bias + CS1

SOA1

Ein

SOA2

Broadcast + CS2

Input

Output 1

Output 2

CS1

SOA3

Eo_1

Eo_2

22 coupler 21 combiner 12 splitter 3-dB attenuator

EU

EC

EL

SI0

CI1

CI2

CO1

CO2

Upper interferometer

Lower interferometer

Input

CS1

CS2

Output 2

Output 1

TSW

Bias

CS1 and CS2

Broadcast

Output 1

Output 2

Switching Mode

Broadcast Mode

CS0

2,121121122

1212

111 cos28

1 GGKKGKGKSW

3,223222122223

2212 cos2

8

1 GGKKGKGKSW

No need = for switching!

CS2

Opt. Bias

Input

Output 2

Output 1

Opt. Broadcast

AOFF

CS1

CS0

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All-Optical Flip-FlopAll-Optical Flip-Flop

CW

:(1 –)

Q

FBL

TFBL

SET

RESET

SOA1

SOA2

Optical delay

Attenuator

Polarization Beam Splitter (PBS)

Polarization Controller (PC)

TSW

PCW

St

Rt

PFBL

TFBL

CS0 CS1

AOFF

CS2

Opt. Bias

Input

Output 2

Output 1

Opt. Broadcast

AOFF

CS1

CS0

SMZ-based AOFF

1- Ultrafast (ps-response)2- Multiple control pulses to neglect the FBL

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AOFF OperationAOFF Operation

SET

RESET

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AOFF OperationAOFF Operation

SET

RESET

Leading ripple

Trailing ripple

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VPI Simulation ParametersVPI Simulation Parameters

TABLE I SOA PARAMETERSParameters ValuesInitial gain 24 dBLaser chip length 0.510-3 mActive region width 2.510-6 mActive region thickness 0.0410-6 mSpontaneous emission factor – nsp 2 (NF = 6 dB)SCH confinement factor – 0.56Linewidth enhancement factor – LEF 3.0Initial carrier density 11024 m-3

Transparency carrier density 1.51024 m-3

Group effective index 3.7DC bias current 0.15 A

TABLE II SIMULATION PARAMETERSParameters ValuesInput data bit rate 100 Gbit/sInput date pulse power 0 dBmOptical wavelength 1554 nmOptical pulse width – FWHM 2 psPacket length 2 ns (200 bits)Packet guard band 1.5 nsSwitching window width – TSW 5.5 nsAverage optical continuous wave bias signal – 3 dBmAverage broadcast signal – 6 dBmCS0 pulse peak-power 33 dBmCS1 power 11.7 dBmCS1 factor – 0.98CS2 pulse peak-power 25 dBmAOFF splitting factor – 0.125AOFF PCW 0 dBmAOFF feedback loop delay – TFBL 0.2 ns

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TaMZ Contrast Ratio ResultsTaMZ Contrast Ratio Results

Carrier density of SOA1

Carrier density of SOA2

Carrier density of SOA3

Input

CS0/CS2

CS1 (AOFF Q)

Broadcast signal

Output 1

Output 2

CS0 CS2

Achieved CRs

0 5 10 15 20 25 30 35-10

-5

0

5

10

15

20

25

30

Power of CP1 (dBm)

Con

tras

t rat

ios

(dB

)

CROP12

CROP21

CRCH1

CRCH2

• High CR: ~ 20 dB

• Large input power range

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TaMZ Stability (1)TaMZ Stability (1)

0.35 0.4 0.45 0.5 0.55 0.6 0.6510

15

20

25

30

35

40

Coupling factor of CI1

Con

tras

t ra

tios

(dB

)

CROP12

CROP21

Theoretical CROP12

Theoretical CROP21

CRCH1

CRCH2

Input Imbalance

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TaMZ Stability (2)TaMZ Stability (2)Output Imbalance

0.35 0.4 0.45 0.5 0.55 0.6 0.6510

15

20

25

30

35

40

Coupling factor of CO1

Con

tras

t ra

tios

(dB

)

CROP12

CROP21

Theoretical CROP21

CRCH1

CRCH2

Fluctuation in output coupling ratio induce less CR degrading in comparison to input coupling ratio

IEEE ICC 07, UK

SummarySummary

• SMZ and TaMZ are ultrafast switches, however, TaMZ offers better switching contrast ratio (~ 20 dB) in a much larger input power range

• TaMZ switch provides the blocking and broadcasting capabilities

• Compact size (possibly integrated)

IEEE ICC 07, UK

Thank you!