OPTICAL SWITCHING

1. MOHD NAZIR SHAKEEL
Optical Switches

2. Introduction
 In a MEMS optical switch, a micro-mirror is used
to reflect a light beam.
 The direction in which the light beam is reflected
can be changed by rotating the mirror to different
angles, allowing the input light to be connected to
any output port.
 This type of optical switch has been realized for
the first time through the fusion of various
techniques such as micro-machining techniques
for fabricating the mirror, optical design
techniques for achieving low-loss optical
connections, and control techniques for
positioning the mirror accurately.

3. What are the features?
 Can switch optical signals without converting
them into electrical signals.
 Allows compact low-loss switches to be formed
on any scale.
 Switching can be performed in 10-30 msec.

4. What can it do?
 Since this device can switch large numbers of
optical signals simultaneously, it can be used as a
trunk switch for handling large amounts of
traffic, and as a switch in large urban
communication networks.

5. 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

6. Optical switches
 What are the options
(From Tellium Inc)

7. MEMS Optical Switches
 What is MEMS
 Micro-Electro-Mechanical System
 What is MEMS optical switches
 Steerable micro mirror array to direct optical light
from input port to its destination port.
 System-in-a-chip

8. 2D MEMS Switches
 Mirrors have only 2 positions (cross or bar)
 Crossbar configuration
 N2 mirrors

9. 3D MEMS Switches
 Mirrors can be
tilted to any angles
 N or 2N mirrors
accomplishing
non-block
switching
 Good scalability

10. How to fabricate
 MEMS process

11. Actuating Mechanism (I)
 Electrostatic
mirrors are tilted by electrostatic force
between opposite charged plates

12. Actuating Mechanism (II)
 Electromagnetic
attraction between electromagnets with
different polarity

13. Actuating Mechanism (III)
 Scratch Drive Actuators (SDAs)
mecromachining scheme

14. 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)

15. Performance
 Switching speed
sub microsecond
 Scalability
512 512
 Insertion Loss
3-7 dB
 Power dissipation
less than electrical switch core

16. Challenges
? Controllability
? Reliability
? Manufacturability
? Serviceability
? Standardization

17. 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.