MEMS Optical Switches

Xiaobo Hou

ECEE 641

March. 13, 2003

Introduction

Why optical switches– Explosive network traffic– Rapidly growing data rate and port count– Bottleneck due to conventional OEO switches

(bandwidth, bit error rate and capacity mismatch)

– Cost effective• Competition is in the

high date rate range

Optical switches

What are the options

(From Tellium Inc)

MEMS Optical Switches

What is MEMS– Micro-Electro-Mechanical System

What is MEMS optical switches– Steerable micromirror array to direct optical

light from input port to its destination port.

– System-in-a-chip

2D MEMS Switches

Mirrors have only 2 positions (cross or bar)

Crossbar configurationN2 mirrors

3D MEMS Switches

Mirrors can be tilted to any angles

N or 2N mirrors accomplishing non-block switching

Good scalability

3D switch examples

Lucent WaveStar LambdaRouter, 1999

Nortel X-10002000

How to fabricate

MEMS process

How to design

Paraxial Gaussian beam model

Optimize beam size W0, Given separation between mirror arrays

0w

Z R

2

00

2

0 11)(

w

zw

z

zwzw

R

2

1

)(0

z

w opt

Actuating Mechanism (I)

Electrostatic– mirrors are tilted by electrostatic force

between opposite charged plates

Actuating Mechanism (II)

Electromagneticattraction between electromagnets with different polarity

Actuating Mechanism (II)

Scratch Drive Actuators (SDAs)mecromachining scheme

Actuating Mechanism Comparison

Actuating Mechanisms

Advantages Disadvantages

Electrostatic Well understood Good repeatability

Nonlinearity in force-voltage relationship,

High driving voltages. Electromagnetic Large force

High linearity Low driving

voltages

Shielding magnetic devices

Reliability to be proved

Scratch Drive Actuator(SDA)

No holdup voltage required

Movement in small steps (10nm)

(N/A)

Performance and Challenges

Switching speedsubmicrosecond

Scalability512 512

Insertion Loss3-7 dB

Power dissipationless than electrical switch core

? Controllability? Reliability? Manufactuability? Serviceability? standardization

Conclusion

MEMS optical switches are currently dominant and promising in the future

Open question to switch speed:what is the ultimate requirement?

ALL-optical?

Not yet.