MEMS Wavelength Add/Drop SwitchJoseph Ford, James Walker, Vladimir Aksyuk, David Bishop

References: J. Ford, V. Aksyuk, D. Bishop and J. Walker, “Wavelength add/drop switching using tilting micromirrors”Journal of Lightwave Technology 17(5) p.904-911, 1999 (first presented as post-deadline paper PD2.3 at the 1997 LEOS Annual Meeting)

See also US patents #6,204,946 and #6,307,657

Switching in Dense Wavelength-Multiplexed Ring Networks

Cost: $750k for transponders alone (~ $40k/channel at OC-48)

Demultiplex, detect, and regenerate all wavelengths

- deMUX - MUXe - deMUX

Electronicswitch fabricwith local I/O

R T

R T

R T

R T

e - MUX

Conclusion: “Run away!”

Value: Sub-wavelength grooming flexibility and full 3R regeneration

Head-on approach: demultiplex into electronic switch fabric

Combine wavelength multiplexing and switching into a transparent optical component

Instead: MEMS wavelength-selective add/drop switching

Cost: Integration means less flexibility (channel count and pitch)

Value: Cuts network build-out expense (first installed cost) & overall insertion loss

T

R

deMUX / switch / reMUX

Dropped channels

Added channels

MEMS = Micro-Electro-Mechanical Systems

• Surface Micromachining• LIGA (electroforming)• Deep Reactive Ion Etching

• Electrostatic attraction• Electromagnetic force• Electrostriction• Resistive heating

Photos courtesySandia National Labs

… manufactured using technology created for VLSI electronics

to build micron-scale devices “released” by selective etching

…& electrically controlled by

MEMS digital tilt-mirror switch

Device: Surface micromachined in “MUMPS”3-layers of polysilicon structure, (silicon nitride sacrificial layers)50nm Gold on 3nm Chrome mirror

Switches: 30 x 50 micron mirrors +/- 5o (+/- 10o optical)

Free-space wavelength multiplexing

Ford, Walker, Goossen & Neilson, European Conf. On Optical Commun.. 1999

Package performance3.7 dB loss, 0.1 dB PDL (incl. optical circulator)100 nm spectral range (5 mm active area)Custom achromatic lens (athermal lens & kovar mechanics)

I/O Fiber(to circulator)

Electrical I/O

Lens and /4f = 50mm

MicromechanicalSwitch Array

Grating in tip/tilt mount600 lp/mm, 43o blaze angle

Gold-coated epoxy on Zerudur substrate

Digital MEMS mirror switchingV

olt

ag

e

Time

Vrms

In

V2

DropIn Pass

V1

Drive waveform 20 V rms from 300 KHz sine (to avoid electrostatic charging)

Switch response 20 microseconds (digital envelope on 300 KHz sine)~2 microseconds (optimized drive waveform)

Prototype free-space optics package

600 lp/mm grating

MEMSSwitchArray

f = 25 mm lens

/4 plate

f = 50 mm lens

Pupil division optics separates I/O beams Light is either back-reflected or separated 2x magnification onto device plane

Total insertion loss: 4 dB Resolution 16 channels @ 200 GHz (1.6 nm)

19 alignment knobs!

DROPADD

In

V2

OutIn Back

V1

OUT

IN

DROP

ADD

IN PASS

2x2 add/drop switch configuration

Optical circulators create 4 distinct ports from two I/O fibers

IN PASS In Pass

V1

InAdd

V2

DropPass

Add/drop switch performance

Pass Mix

-45

-35

-25

-15

-5

1531 1557Wavelength (200 GHz grid)

Pass Mix

-45

-35

-25

-15

-5

1531 1557Wavelength (200 GHz grid)

Pass: 5 dB loss, 30 dB contrast Add/Drop: 7 dB loss, 30 dB contrast

2002 European Conference on Optical Communications, Paper 2.3.1

MEMS tilt-mirror add/drop switches now in development… although not at Lucent or their spinoff Agere!

Network Photonics “CrossWave 1-D MEMS” Switch

www.networkphotonics.com/whitepapers/index.html

JDS Uniphase MWS 1x4 add/drop switch