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External Cavity Diode Laser
Tuned with Silicon MEMS
MEMS-Tunable External Cavity Diode Laser
Lenses
Laser
Output
AR-coated
FP Diode
3 mm
Diffraction
Grating
Silicon
Mirror
Balanced
MEMS
Actuator
iolon Microactuators
MEMS Technology
l
Electrostatic comb drive actuator fabricated in
single-crystal silicon by Deep Reactive Ion
Etching (DRIE).
l
High aspect ratio of combs provides high outof-plane stiffness and high actuator force.
l
Lithographically fabricated Si mirror attached
to flexural rotary suspensions is rotated by
applying up to 140 V to the comb drive.
Reliable and Robust Devices
l
Single-crystal Si flexure, no touching or
rubbing parts = no material fatigue
l
> 80 billion device cycles with zero failures
l
Fast, durable, low-cost
Integrated Laser, Wavelength Locker, & Shutter
External Cavity Laser
Laser
Lenses
Diode
Mounted on a common TE cooler
in an 18 pin hermetic package
PM Fiber
Pigtail
Wavelength
Locker
Grating
MEMS
Actuator
Silicon
Mirror
Isolator
Beam
Splitter
Shutter/
VOA
Tunable Laser Servo Block Diagram
SERVO CONTROL
HARDWARE
SHUTTER
CONTROL
WAVELENGTH
CONTROL
MEMS
MIRROR
PHASE
CONTROL
PHASE
ADJUSTER
POWER
CONTROL
LASER
DIODE
POWER MONITOR
OPTICAL
MONITORS
PHASE MONITOR
WAVELENGTH
LOCKER
WAVELENGTH MONITOR
THERMISTOR
TEMP
CONTROL
T.E.
COOLER
MEMS
SHUTTER
TUNED LASER
OUTPUT
10 ms Wavelength Tuning and Locking
Across 100 Channels at 25 GHz
10 ms
188.500 THz
Coarse Wavelength Monitor
(Linear Filter)
190.975 THz
Fine Wavelength Monitor
(Etalon)
Power Monitor
Cavity Length
Adjust
Time (ms)
See Paper MF61
Optical Power (dBm)
200 Channels at 25 GHz, L-band
>20 mW Output Power
Optical Power (dBm)
10
0
-10
-20
10
0
-10
-20
-30
-40
-50
188.75
-30
188.8
188.85
-40
-50
186.5
187
187.5
1607.5 nm
188
188.5
189
189.5
190
Frequency (THz)
190.5
191
191.5
1565.7 nm
188.9
188.95
189
Optical Performance: Power, SMSR, SSE
40 mW (+16 dBm) Fiber Output Power
SMSR = 55 dB
10
0
-10
20
+16 dBm
55 dB
-20
-30
-40
-50
Optical Power (dBm)
Optical Power (dBm)
20
-60
191.30 191.32 191.34 191.36 191.38 191.40
Frequency (THz)
10
SSE = -54 dBc/nm
(0.1 nm RBW)
+16 dBm
0
-10
-20
-30
-40
-50
-60
189
190
191
192
Frequency (THz)
193
Optical Performance: Linewidth
• Instantaneous Linewidth ~ 125 kHz from phase noise spectrum
• Time-Averaged Linewidth ~ 2 MHz due to low-frequency actuator motion
1012
Frequency Deviation Spectrum
Relative RF Power (dB)
Spectral Density (Hz2/Hz)
• SBS Suppression Linewidth ~ 200MHz using 200 kHz current dither
109
106
103
104
105
106
Frequency (Hz)
107
-20
-20
-30
-30
-40
-40
-50
-50
3 µs
25 µs
-60
-60
0
5
10
15
20
-70
-80
0
20
40
60
Frequency (MHz)
80
100
System Performance, MEM-ECL vs. DFB
Nearly identical BER and
transmitted eye diagrams in a
500 km amplified link at 40 Gb/s
Similar DFB-like
eye diagrams and
BER seen at:
2.5 Gb/s
10 Gb/s
40 Gb/s
Link lengths up to
3000 km
Data courtesy of
Lucent Technologies
Environmental Stability and Reliability
Wavelength
Tuning
Temperature
Cycling
Accelerated
Aging
Power (dBm)
13.2
13.1
12.9
12.8
1.0
Frequency
Deviation (GHz)
Power Variation
< ± 0.1 dB
13.0
Sequential locking
to 100 channels
Random locking
to 100 channels
Locked to single
channel at 70 C
0.5
Frequency Error
< ± 0.5 GHz
0.0
-0.5
-1.0
187 188 189 190 191 -10 0 10 20 30 40 50 60 70 0
Laser Frequency
(THz)
Case Temperature
(C)
1000 2000
Time
(hours)
3000
Balanced MEMS Actuator
Mechanically balanced actuator is resistant to
shock and vibration.
Pivoting lever is balance mechanism; similar to a see-saw.
Force
Mass 1
Mirror
Force
Mass 2
Motor
Servo system actively controls laser to ITU wavelength
to further reduce shock and vibration sensitivity.
Lasers exhibit < 2.5 GHz wavelength error with a 35 g
half-sine shock.
Card slams and fan tray insertions produce up to 20 g shock
to an operating line card.
GR468 does not specify operating shock.
Frequency Acceleration Acceleration
(g)
Error (GHz)
(g)
Shock and Vibration Immunity
20
10
0
-10
–20
-30
Card slam produces
up to 20 g shock to an
operating line card
Typical Card Slam
0
-10
-20
-30
-40
2
1
0
-1
-2
35 g Shock
Frequency error < 1 GHz
with 35 g half-sine shock
Frequency Error < 1 GHz
0
1
2
3
4
5
6
Time (ms)
7
8
9
10
Laser Module Power Dissipation
Power Dissipation (Watts)
5
Measured Power Dissipation for
20 mW output at Vcc = 3.3V is:
4
1.75 W at 25 °C
4.4 W at 70 °C
3
2
1
0
-10
0
10
20
30
40
Case Temperature (C)
50
60
70
Power dissipation is nearly
constant over 5 THz tuning range
(no channel-to-channel variation)
iolon Tunable Laser Summary
•
•
•
•
•
•
C-band or L-band
Tuning Range up to 44 nm
25 GHz or 50 GHz Channels
Integrated Wavelength Locker
Tuning Time < 15 ms
Power Dissipation < 4.4 W at 70 C
• Output Power up to 40 mW
• Power Variation < ± 0.25 dB
• Frequency Error < ± 1 GHz
• SMSR > 50 dB
• Linewidth < 200 kHz
• Dither for SBS Suppression
• RIN < -145 dB/Hz to 22 GHz
• Dark Tuning
• Butterfly and control electronics with 40-pin serial
connector in 70×50×13mm module.
• Compliant with OIF (Optical Internetworking Forum)
and Tunable Laser MSA (Multi-Source Agreement)
between iolon, Bookham, GTRAN, Intel, QDI, Santur,
and Vitesse.
• Telcordia Qualified
2.5 Gb/s Directly Modulated
Tunable Laser Transmitter
q Direct modulation at 2.5 Gb/s using a low-capacitance laser
diode in the ECL provides a cost-effective widely tunable
transmitter for metro applications.
q < 2 dB transmission penalty over 250 km at 2.5 Gb/s
q Dynamic chirp is 5X lower than standard DFB due to the
free-space cavity length of the ECL.
q Laser chip length is only 20% of total cavity length.
10G Long Reach LiNbO3 Transponder
300 pin MSA Compliant
Tunable laser supplied by iolon
CMU
Driver
Mux
16:1
FIFO
16 X 6YY*
Mb/s
BiasControl
Circuit
Modulator
Tunable
Laser
9.953 Gb/s
Serial Transmit Data
9.953 Gb/s
Serial Receive Data
TIA
PA
µ-Controller
Jitter
Filter
TxREFCLK
155.52 or
622.08MHz
Rate
Adjust
CDR
DeMux
1:16
RxREFCLK
16 X 6YY*
Mb/s
Full band wavelength (40 nm) tunability
C and L Bands
Tunable Lasers for Optical Networks
q Tunable lasers are network-ready
q Match performance of fixed-wavelength DFBs
q Meet reliability criteria for 99.999% network deployment
q Supplied by multiple vendors under multi-source agreements
q Replacement of fixed-wavelength lasers with tunables is
economically justified today
q Costs of tunable transmitters are increasingly competitive with
costs of fixed-wavelength transmitters
q … In legacy fixed-wavelength networks, for the cost savings of
inventory reduction and sparing.
q … In new wavelength-agile optical networks that provide for
bandwidth re-provisioning, streamlining of traffic patterns, and new
services, creating lower operating costs and higher revenues.
Thank You
For more information …
Demos:
iolon # 4312
Optium # 6114
OIF # 7620
Fiberbyte # 7356
Luna # 4212
Papers:
MF61 – Tunable Laser Frequency
and Mode Control
TuN2 - Tunable Filter