Transcript MEMS Optical Switches - Electrical and Computer Engineering

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 configuration
N2 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-1000
2000
How to fabricate
MEMS process
How to design
 Paraxial Gaussian
beam model
 Optimize beam size
W0, Given separation
between mirror arrays
ZR 
w0

2
 z 
 z 

w( z )  w0 1     w0 1  
z

w
 R
 0
 z 
w0( opt )   
 
1
2
2
Actuating Mechanism (I)
Electrostatic
– mirrors are tilted by electrostatic force
between opposite charged plates
Actuating Mechanism (II)
Electromagnetic
attraction between electromagnets with
different polarity
Actuating Mechanism (II)
Scratch Drive Actuators (SDAs)
mecromachining scheme
Actuating Mechanism Comparison
Actuating
Mechanisms
Electrostatic
Advantages
Disadvantages
Well understood Nonlinearity in forceGood repeatability voltage relationship,
High driving voltages.
Electromagnetic
Large force
Shielding magnetic
High linearity
devices
Low driving
Reliability to be
voltages
proved
Scratch Drive
No holdup voltage
(N/A)
Actuator(SDA)
required
Movement in
small steps (10nm)
Performance and Challenges
 Switching speed
submicrosecond
 Scalability
512  512
 Insertion Loss
3-7 dB
 Power dissipation
less 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.