EE16.468/16.568 Lecture 3Waveguide photonic devices

1. Mach-Zehnder EO modulator

Electro-optic effect, n2 changes with E -fielda1a2

a3

b1b2

50%A Aout

b3n2

n

EE16.468/16.568 Lecture 3Waveguide photonic devices

Switches

High power modulatorsFilters

• Network configuration

• Dynamic routing data traffic

• Provide high-speed data stream for shared users• Reduce noise

2. Optical Switches

EE16.468/16.568 Lecture 3Waveguide photonic devices

Types of Optical Switches

• Hard for switch array

• Hard for alignment

• Reliability issues

1. Micro-electro-mechanical systems (MEMS) Disadvantages:

From Lucent, Bell lab

EE16.468/16.568 Lecture 3Waveguide photonic devices

• Free space based, hard to integration

• Hard for alignment

• Large size

2. Liquid crystal based optical switch Disadvantages:

EE16.468/16.568 Lecture 3Waveguide photonic devices

3. Thermo-optic switch, directional coupler based

• Wavelength sensitive

• Large size for switch array

Disadvantages:

P1

P2P2

P0=1

L

Coupler TO switch

Heater

Heater

Heater

Input waveguide

output waveguides

EE16.468/16.568 Lecture 3Waveguide photonic devices

4. Thermo-optic switch, total internal reflection based

2/n1

n2

,)2

90sin( 21 nn

,12 TdT

dnnn

,/104.1 4 CdT

dn o

EE16.468/16.568 Lecture 3Waveguide photonic devices

Advantages of TIR based thermo-optic switch

• Easy array operation

• Wavelength insensitive

TIR TO switch array

EE16.468/16.568 Lecture 3Waveguide photonic devices

2x2 thermo-optic switch and 8x8 switch arrays

2 optical chips, each with an array of 8x8 optical switches

Input Waveguides

Output WaveguidesElectrode Pads

EE16.468/16.568 Lecture 3Waveguide photonic devices

Device performance

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 20 40 60 80Temperature (°C)

Mon

itor O

utpu

t Input Waveguide

Crossed Waveguide

EE16.468/16.568 Lecture 3Waveguide photonic devices

5. Resonator based EO optical switch

EE16.468/16.568 Lecture 3Waveguide photonic devices

5. Resonator based EO optical switch array

• Easy scale up to NxN arrayt

• Low power consumption, high yield and high reliability

• Very compact size

EE16.468/16.568 Lecture 3Waveguide photonic devices

Wavelength division multiplexing (WDM) technology

EE16.468/16.568 Lecture 3Waveguide photonic devices

Coarse Wavelength-division Multiplexing (CWDM)

Dense Wavelength-division Multiplexing (DWDM)

EE16.468/16.568 Lecture 3Waveguide photonic devices

3. Array waveguide grating (AWG)

EE16.468/16.568 Lecture 3Waveguide photonic devices

3. Array waveguide grating (AWG)

LmLiN

m

LiN

m

eN

Ae

N

Am

)1(12

1

0

1

0 0)()(

L0

L0 +(m-1)L

Center channel

22

LNc

Nc: index in channel

ns

EE16.468/16.568 Lecture 3Waveguide photonic devices

3. Array waveguide grating (AWG)

ndnf

DLN sc 2

'

2

L0

L0 +(m-1)L

Upper one channel:

f DD

d

L0 +(m-1)L – (D/f)(m-1)d

22

c

LN

LNdnf

DLN

Csc

2

'

2sc

dnf

DLN

c

s

fN

nDdL