ECEN689: Special Topics in Optical Interconnects Circuits ...spalermo/ecen689_oi/lecture11_ee689_rrm_tx.pdfECEN689: Special Topics in Optical Interconnects Circuits and Systems Spring

Sam PalermoAnalog & Mixed-Signal Center

Texas A&M University

Lecture 11: Ring Resonator Modulator Transmitters

ECEN689: Special Topics in Optical Interconnects Circuits and Systems

Spring 2016

Announcements

• Exam2 is on Apr. 28 • 2:20-3:45PM (10 extra minutes)• Closed book w/ one standard note sheet• 8.5”x11” front & back• Bring your calculator• Comprehensive, but will focus primarily on

Lecture 5 and beyond

2

Agenda

• WDM Optical Interconnect Motivation

• Silicon Photonic Modulators

• Carrier-Injection Ring Resonator Modulators

• Carrier-Depletion Ring Resonator Modulators

3

Wavelength-Division Multiplexing (WDM) Optical Interconnects

4

• Optical interconnects remove many channel limitations• WDM allows for multiple high-bandwidth (10+Gb/s)

signals to be packed onto one optical channel

[Young JSSC 2010]

Next-Generation 100G Interconnects

5

LinkDistance

TransceiverType

# of I/O Ports(25Gb/s NRZ)

0.5m Electrical PCB Trace × 41m Electrical Backplane × 4

10m Electrical Cu Cable × 4100m VCSEL MMF × 41km MZI / EAM SMF × 4

> 10km MZI / EAM SMF × 4

[Google Datacenter]

Next-Generation 100G Interconnects

6

LinkDistance

TransceiverType

# of I/O Ports(25Gb/s NRZ)

0.5m Electrical PCB Trace × 41m Electrical Backplane × 4

10m

Ring ModulatorWDM SMF × 1

100m1km

> 10km

[Google Datacenter]

Ring Resonator Filter

• Ring resonators display a high-Q notch filter response at the through port and a band-pass response at the drop port

• This response repeats over a free spectral range (FSR)

7

Ring-Resonator Modulator (RRM)

• Refractive devices which modulate by changing the interference light coupled into the ring with the waveguide light

• Devices are relatively small (ring diameters < 20m) and can be treated as lumped capacitance loads (~10fF)

• Devices can be used in WDM systems to selectively modulate an individual wavelength or as a “drop” filter at receivers

8

[Young ISSCC 2009]

Wavelength Division Multiplexing w/ Ring Resonators

• Ring resonators can act as both modulators and add/drop filters to steer light to receivers or switch light to different waveguides

• Potential to pack >100 waveguides, each modulated at more than 10Gb/s on a single on-chip waveguide with width <1m (pitch ~4m)

9

[Rabus]

WDM Photonic Transceiver

10

• High bandwidth density by combining multi-channels on a single waveguide via wavelength division multiplexing

Agenda





11

Plasma Dispersion Effect

• The change in refractive index and optical absorption coefficient is induced by free carriers in a semiconductor

N n i N: complex index of refractionn: electro-refraction: electro-absorption

1550 nm

1310 nm 0.822 181.31 6.2 10 6.0 10m e hn n n

18 18 1

1.31 6.0 10 4.0 10 [ ] m e hn n cm

0.822 181.55 8.8 10 8.5 10m e hn N N

18 18 1

1.55 8.5 10 6.0 10 [ ]m e hN N cm

12∆Ne: electrons density∆Nh: holes density

Silicon Photonic Modulators

• Carrier Accumulation• Carrier Injection• Carrier Depletion

13

Figure of Merit Carrier Accumulation

CarrierInjection

Carrier Depletion

Modulation Bandwidth High Low High

Extinction Ratio (ER) Small Large Small

Modulation Efficiency High High Low

Insertion Loss High Low High

+-+ -+ -+ -

+--+

n++ p++

Contact Contact

BOXn++ p++

Contact Contact

BOX

Si n+ p+n++ p++

Contact Contact

BOX

• Electrooptic-polymermodulators have alsobeen developed

• Mach Zehnder Modulator• Microring Modulator

MZM vs Microring Modulators

Figure of Merit Mach Zehnder Microring

Footprint Large Small

Extinction Ratio (ER) Small Large

Insertion Loss High Low

Wavelength Sensitivity Low High

+-

+ -+-+-

14

p+n+

p+n+

n+

p+

Agenda



• Carrier-Injection Ring Resonator Modulators• Device Operation and Modeling• High-Speed Driver• Wavelength Stabilization Loop


15

Carrier-Injection Microring Modulator

16

• Ring waveguide is doped as a PIN junction

• Forward-bias voltage injects carriers, changing refractive index for optical modulation via the free carrier plasma dispersion effect

C-I Ring Modulator Speed Limitations

• Speed is limited by long minority carrier lifetimes• Pre-emphasis signaling significantly improves data rates

17

Input

p+ doped

n+ doped

n+ doped

Outputn+ p+Si

V

Waveguide

w/ Pre-emphasis

Simple NRZ 8Gb/s

8Gb/s

Carrier-Injection Ring Modulator Modeling

• Previous Related Modeling Work• P-I-N diode model (only electrical dynamics)• Ring resonator model (only optical dynamics)• Carrier-injection ring modulator model (lack accurate

large-signal behavior)

• Carrier-Injection Ring Modulator Model• Capture nonlinear electrical and optical dynamics

18

[Strollo TPE 1997]

[Smy JOSA B 2011]

[Binhao Wang, Cheng Li, Chin-Hui Chen, Kunzhi Yu, Marco Fiorentino, Raymond Beausoleil, and Samuel Palermo, “Compact Verilog-A Modeling of Carrier-Injection Microring Modulators for Optical Interconnect Transceiver Circuitry Design,” accepted in Journal of Lightwave Technology]

[Binhao Wang, Cheng Li, Chin-Hui Chen, Kunzhi Yu, Marco Fiorentino, Raymond Beausoleil, and Samuel Palermo, “Compact Verilog-A Modeling of Silicon Carrier-Injection Ring Modulators,” IEEE Optical Interconnects Conference (OIC), 2015]

[Cheng Li, Chin-Hui Chen, Binhao Wang, Samuel Palermo, Marco Fiorentino, and Raymond Beausoleil, “Design of an Energy-Efficient Silicon Microring Resonator-Based Photonic Transmitter,” IEEE Design & Test of Computers, 31, 46-54, 2014]

[Cheng Li, Rui Bai, Ayman Shafik, Ehsan Zhian Tabasy, Binhao Wang, Geng Tang, Chao Ma, Chin-Hui Chen, Zhen Peng, Marco Fiorentino, Raymond Beausoleil, Patrick Chiang, and Samuel Palermo, “Silicon Photonic Transceiver Circuits with Microring Resonator Bias-Based Wavelength Stabilization in 65-nm CMOS,” IEEE Journal of Solid-State Circuits (JSSC), 49, 1419-1436, 2014]

[Xu OE 2007, Wu OE 2015]

Model Flow Chart

19

Driving Voltage

Current Response

P+ N- N+

p-i-n diode SPICE model Carrier

Concentration0( )

t

totalQ I t dt q

totalQ freeQ

c RCC

R

0.822 181.31 6.2 10 6.0 10m e hn n n

18 18 11.31 6.0 10 4.0 10 [ ]m e hn n cm

Index and Loss Changes

Plasma dispersion effect

Input

p+ doped

n+ doped

n+ doped

Outputn+ p+Si

V

Waveguide

Optical Power

Dynamic ring resonator model

4

1 11

expnn

n m

E tT t a t j t m

E

input1E

output4E

2E3E

a

Electrical Modeling - PIN Dynamics

• I-V dynamics are based on a moment-matching approximation of the ambipolar diffusion equation

20

[Strollo TPE 1997]

H0 GE G3

Repi

Rlim Gmod

Gpin

Ej Dj

1 5 9 13 17

0

7T

0

11T

0

15T

0

19T

5 9 13 17

10 20

1112

VS2

VS1Anode Cathode

+-

+-

intrinsic region junctions1 0SV

mod 2 2 3111,12 AM AM

M M

L LG V V V VV V

P+ N- N+

VepiVp Vn

IIepi

Ir

Rc Rc

I Iepi

V1 V2 V3

pin epi p n epi jV V V V V V (10,12) (12,20)c epi j cV V V V V V V

1 0( ) 1j TE NVS SI V q I e

0 1 0( )SH I V q pin epi EI G I G

20r E EI G q I

2

03 3 1

3HI j

PT SC

P VTG VV R I

epi rI I I (12,20)j jE V V

Parameters initialization based on an empirical range

Estimation of RC, PHI, IS, N, IE, VM, RLIM and REPI parameters by fitting DC measurement

Estimation of T0, τ, LAM, VPT and RSC parameters by fitting transient measurement

Delivery of the parameter set













Parameter Unit Description ValueRc Ω Contact resistance 50

IS A Saturation current 5.78 1014

N - Emission coefficient 1.46

PHI V Build-in voltage 0.7

T0 s Transit time 1.04610-10

IE A Emitter recombination knee current 1.010-3

VM V High-injection voltage drop on the base 0.12

Rlim Ω Carrier-scattering series resistance 1.810-3

LAM - Forward-recovery coefficient 0.03

τ s Carriers Lifetime in the base 1.010-9

Repi Ω Base region resistance 300

VPT V Reverse-recovery coefficient 10

RSC Ω Reverse-recovery coefficient 18

Parameter Unit Description RangeRc Ω Contact resistance 20 - 100

IS A Saturation current 1 1014 - 1 1012

N - Emission coefficient 1 - 2

PHI V Build-in voltage 0.5 - 1

T0 s Transit time 110-10 - 110-9

IE A Emitter recombination knee current 1.010-4 - 1.010-2

VM V High-injection voltage drop on the base 0 – 0.5

Rlim Ω Carrier-scattering series resistance 110-3 - 310-3

LAM - Forward-recovery coefficient 0 – 0.1

τ s Carriers Lifetime in the base 1.010-10 - 1.010-8

Repi Ω Base region resistance 1102 - 1103

VPT V Reverse-recovery coefficient 5 - 20

RSC Ω Reverse-recovery coefficient 1- 100

Electrical Modeling - Parameter Extraction

21

10Gb/s 0101… excitation

Optical Modeling - Carrier Dynamics

• Carrier Concentration

0

/t

Q I t dt q total free remain recombineI t I t I t I t

total free remain recombineQ t Q t Q t Q t

0.822 181.31 6.2 10 6.0 10m e hn n n

18 18 1

1.31 6.0 10 4.0 10 [ ] m e hn n cm22

High pass filter

The time constant is equal to the carrier lifetime

totalQ freeQ

c RC

CR

10Gb/s 0101… excitation

• Index and Loss Changes

Optical Modeling - Optical Dynamics

• Consider the ring’s cumulative phase shift• Capture non-linear optical dynamics

1E 4E

2E 3E

a

4

1 11

expnn

n m

E tT t a t j t m

E

1

exp

exp

1 exp

n

n

T t a t jn t

a t j t

a t j t

2efft n t L

where

23

2 2 1 [Loannidis OL 1988]


• Parameter Extraction

Parameter Unit Description Value

σ - Transmission coefficient 0.9944

a - Loss coefficient 0.9931

neff - Effective index 2.5188

r µm Ring radius 5

24

• Large extinction ratio (ER) ~20dB• High modulation efficiency ~560pm/V

• Ring modulator under test

• 8Gb/s eye diagrams with simple NRZ signal

VoltageSwing DC Bias

Simple NRZ Signaling

1.7V

2V

25-0.3V

0.7V

Parameter Description

Coupling waveguide 350nm (W), 250nm (H), 50nm (slab)

Ring waveguide 450nm (W), 250nm (H), 50nm (slab)

Gap 250nm

Radius 5um

P+ doping BF2+, 5e14 cm-2, 10 KeV, Tilt 8°, Twist 27°

N+ doping As, 5e14 cm-2, 10 KeV, Tilt 8°, Twist 27°

• Pre-emphasis NRZ signal generation

• Proposed model utilized to study the impact of key pre-emphasis parameters• Pulse duration• Pulse depth• DC bias

Pre-Emphasis Signaling

26

Pattern Generator

data

data Combiner MicroringModulatorDelay

Pre-Emphasis Optimization - Duration

• Pulse Duration • Pulse Depth = 0.8V • DC Bias = 0.7V

80ps40ps

27

• 40ps pulse duration allows the eye to partially open• 80ps pulse duration provides optimal eye opening

Duration

Depth


2V

1.7V

0.9V

0.5V

-0.3V

0.7V

Pre-Emphasis Optimization - Depth

0.9V 0.8V 0.7V

28

• Pulse Duration = 80ps • Pulse Depth• DC Bias = 0.7V

• 0.9V pulse depth results in low amount of charge for logic “1”• 0.7V pulse depth produces excessive charge for logic “1”

80ps

Duration

Depth


2V

1.7V

-0.3V

0.7V

Pre-Emphasis Optimization - DC Bias

0.75V 0.7V 0.65V

29

• Pulse Duration = 80ps • Pulse Depth = 0.8 V • DC Bias

• 0.75V DC bias produces excessive charge for logic “1”• 0.65V DC bias results in slower carrier injection for logic “1”

80ps

Duration

Depth


2V

Co-Simulation with CMOS Driver

• Hybrid-integrated CMOS and silicon photonics prototype• Optical transmitter co-simulation schematic• Asymmetric pulse duration pre-emphasis setting• 9Gb/s measured and co-simulated eye diagrams 30

1.45V

1.15V

-0.55V

-0.05V2V

70ps

50ps

0.55V

DAC

Driver500pH

500pH

40fF 40fF

40fF 40fF

PIN RingModulator

Cathode

Anode

High-Swing Pre-Emphasis Driver

31

• Dual-edge pre-emphasis with pulse width controlled by tunable delay cells (30ps~60ps)

• Cascode output stage used to meet high modulation swing requirement

[C. Li JSSC 2014]

Optical Transmitter Assembly

32

Electrical Eye (9Gbps, with Pre-emphasis)

Electrical Eye (9Gbps, w/o Pre-emphasis)

Optical Eye (9Gbps, with Pre-emphasis)

Closed Optical Eye (9Gbps, w/o Pre-emphasis)

* C. Li et. al. IEEE Design & Test, 2014

480fJ/bit

• GP 65nm CMOS 5-channel TX prototype• 130nm SOI carrier-injection ring resonator modulators

Resonant Wavelength Sensitivity

33

• Ring’s resonance wavelength is sensitive to fabrication variations and temperature fluctuations

• Requires tuning schemes to compensate wavelength drifts

Extinction Ratio Impact• Ring devices resonance wavelength can shift

with fabrication and temperature variations• Tuning schemes necessary to stabilize

resonance wavelength

Before Tuning After Tuning

Bias vs Thermal Tuning

35

Bias Tuning Thermal TuningSpeed Fast (~µs) Slow (~ms)

Direction Blue shift Red shiftPower Low HighRange Narrow WideThermal Tuning

Bias Tuning 1311.4 1311.6 1311.8 1312 1312.2-20

-15

-10

-5

0

5

Wavelength (nm)

Opt

ical

Tra

nsm

issi

on (d

B)

Ring Spectrum vs Bias Voltage

Automatic Tuning Loop

36

• Automatic tuning loop sets ring output power to a DAC-generated reference level corresponding to the ring’s resonance point

• Also applicable for thermal tuning

[C. Li JSSC 2014]

Static Tuning Mode37 of 36

Dynamic Tuning Mode• Lock to average power

0 1 2 3 40

2

4

6

8

10

12

Wavelength Shift (Normalized to 0/2Q)

Extin

ctio

n R

atio

(dB

)

Maximum Extention Ratio (Static tuning)Achieved Extinction Ratio (Modulated data)

• ∆ λshift ≥ FWHM to guarantee ER

Bias-Based Tuning Measurements

39

• Extinction ratio dramatically improved after bias-based tuning

• 340W for a tuning range of 0.28nm

Agenda




• Carrier-Depletion Ring Resonator Modulators• Device Operation and Modeling• High-Speed Driver• Wavelength Stabilization Loop

40

Carrier-Depletion Ring Modulator Challenge I: Output Swing & Biasing

41

• High-speed depletion-mode ring modulator requires: Large swing: >4V Negative DC-bias: -2V

ISSCC2013 This Work

Ring Type Injection Depletion

Doping Profile PIN Lateral

PNQ 8000 5000

Tunability(pm/V) 350 25

Data Rate 9Gb/s 25Gb/s

Swing for>7dB ER < 2Vpp > 4Vpp

1552 1552.6-15

-10

-5

0

- 4V Bias

0V Bias

~8dB ER w/4V Swing

Measured Ring Modulator Spectrum

Opt

ical

Tra

nsm

issi

on

(dB

)1552.2 1552.4

Wavelength (nm)

Carrier-Depletion Ring Modulator Challenge II: Nonlinear Dynamics

42

• Dynamic change of neff → unequal rise/fall times• Asymmetric equalization for non-linearity cancellation

Cathode

Anode

Depletion Ring E-O Model

PhotonLifetime Dynamic

Ring-Index

Change

OutputPower

-80 -60 -40 -20 0 20 40 60 800

0.2

0.4

0.6

0.8

1

Time (ps)

Nor

mal

ized

Out

put P

ower

Simulated 25Gb/s Optical Eye Diagram

-15

0

Falling Edge dneff > 0

Pow

er (d

B)

-15

0

Rising Edge dneff < 0

Pow

er (d

B)

0V - 4V 0V - 4V

Carrier-Depletion Ring Modulator Modeling

• Previous Related Modeling Work• Ring resonator model (only optical dynamics)• Carrier-depletion ring modulator model (lack electrical dynamics)

• Carrier-Depletion Ring Modulator Model• Capture nonlinear electrical and optical dynamics

43

[Smy JOSA B 2011]

[Zhang JSTQE 2010, Buckwalter JSSC 2012, Ban OIC 2015]

[Ashkan Roashan-Zamir, Binhao Wang, Shashank Telaprolu, Kunzhi Yu, Cheng Li, M. Ashkan Seyedi, Marco Fiorentino, Raymond Beausoleil, and Samuel Palermo, “A 40Gb/s PAM4 Silicon Microring Resonator Modulator Transmitter in 65nm CMOS,” accepted in IEEE Optical Interconnects Conference (OIC), 2016]

[Hao Li, Zhe Xuan, Cheng Li, Alex Titriku, Kunzhi Yu, Binhao Wang, Nan Qi, Ayman Shafik, Marco Fiorentino, Michael Hochberg, Samuel Palermo, and Patrick Yin Chiang, “A 25Gb/s, 4.4V Swing, AC-Coupled Ring Modulator-Based WDM Transmitter with Wavelength Stabilization in 65nm CMOS,” IEEE Journal of Solid-State Circuits (JSSC), 50, 3145-3159, 2015]

[Hao Li, Zhe Xuan, Cheng Li, Alex Titriku, Kunzhi Yu, Binhao Wang, Nan Qi, Ayman Shafik, Marco Fiorentino, Michael Hochberg, Samuel Palermo, and Patrick Yin Chiang, “A 25Gb/s, 4.4V Swing, AC-Coupled, Si-Photonic Microring Transmitter with 2-Tap Asymmetric FFE and Dynamic Thermal Tuning in 65nm CMOS,” IEEE International Solid-State Circuits Conference (ISSCC), 2015]

44

Carrier-Depletion Ring Modulator Model

n+ p+n++ p++

Contact Contact

BOX

500nm

950nm 950nm130nm

90nm

Cathode

Anode

∆n = F2(VPN)∆α = F3(VPN)

RN

RP

CPN = F1(VPN)

CSUB

CSUB

RSUB

RSUB

VN

VP

Ring Resonator Dynamics

Input Output

• Lumerical

• Polynomial Curve Fitting

45

Electrical Modeling - Parameter Extraction

2 3 40 1 2 3 4f V a aV a V a V a V

Parameter Unit a0 a1 a2 a3 a4

∆neff - -4.3107 7.3105 8.0106 1.1106 5.2108

∆α dB/cm 0.01 1.5 0.17 -2.3102 1.0103

C fF/μm 0.71 -0.14 5.5102 -1.2102 1.0103

46


0

1 1 12 iA cj A j St

o iS S j A

1 1 1c l where

input outputiS oS

t

t

2 2 2 2g cv R

0 02 n n R m

02 0.751 Rl gv e

• Capture non-linear optical dynamics• Require less memory and computation time

[Little JLT 1997]

47


Parameter Unit Description Value

τ ps Amplitude decay time 9.07

κ - Coupling ratio 0.188

m - Mode number 28

r µm Ring radius 7.5

• Parameter Extraction

• Extinction ratio (ER) ~10dB• Modulation efficiency ~25pm/V

Co-Simulation with CMOS Driver

• Optical transmitter prototype assembly• Optical transmitter co-simulation schematic

48

500pH

500pH

40fF 40fF

40fF 40fF

PN RingModulator

Cathode

Anode

Wire Bonding

Differential High Swing Transmitter

2-Tap FFE Driver

2-Tap FFE Driver

Measured and Co-Simulated 25Gb/s Eye Diagrams

• Asymmetrical ISI is due to the device nonlinearity• It is compensated by an optimized nonlinear equalizer

49

Proposed AC-Coupled Differential Driver

50

• CC = 3pF → 4.4V differential swing

• ZS < 30Ω to minimize low-pass attenuation

• High-pass cut-off: < 10MHz

Simulated AC-Response of Output Passive Network

106 107 108 109 1010 10110

1

2

3

4

5

6

7

Frequency (Hz)O

utpu

t Sw

ing

(V)

ZS = 15Ω, CS = 150fFZS = 30Ω, CS = 75fF ZS = 60Ω, CS = 30fF

Parameters ValueCCRB

CPAD1LWIRECPAD2

RNRPCPN

3pF40kΩ 70fF

500pH30fF20Ω30Ω25fF

ZS

2×VDD

ZS

2×VDD

Lwire

Lwire

Cathode DC-Bias

Cathode

AnodeDC-Bias

CC

CC

RB

RB Rdamping

Rdamping

CPAD1

CPAD1

CPAD2

CPAD2

Rsub

Rsub

Csub

Rn

Rp

Cpn

~4×VDD Swing

Anode

RingModulator

CS

CS

[H. Li ISSCC 2015]

Conventional Segmented Output Driver

• Cascode transistors suffer VDS overstress

• Large parasitic capacitance due to segmented design

0 1 2 3 4-1

-0.5

0

0.5

1

1.5

2

V DS

(V)

Time (ns)

Simulated VDS

1.7V VDS Overstress

Main Cursor

2.4V

0V

2.4V

VDS

VDS

Segmented Output Stage×4

Post Cursor

Main Cursor

Post Cursor

Main Cursor

Post Cursor

Main Cursor

Post Cursor

SEL

SEL

SELB

SELB 0V

Main Cursor

PostCursor

‘1’ LevelFFE

Control

PostCursor

MainCursor

× 1× 2

× 4× 8

Merged Output Stage

2.4V

0V

1.2V

1.2V

‘0’ LevelFFE

Control

‘0’ LevelImpedance

Control

‘1’ LevelImpedance

Control

Proposed 2-Tap FFE Output Driver

52

• Merged cascode transistors

• No VDS overstress

• Reduced parasitics and area

• Independent ‘1’-Level and ‘0’-Level FFE coefficients

Transmitter Architecture

2.4V2-Tap FFEDriver

27-1PRBSGen.

4:1

2.4V2-Tap FFEDriver

Cathode DC-Bias

Anode DC-Bias

TX<1:5>

12.5GHzClockInput

OpenDrain

4:1

4:1

4:1

Tap0

Tap0b

Tap1

Tap1b

8:4

CML-to-CMOS &Clock Buffers

Tap0HTap0LTap1HTap1L

Tap0bHTap0bLTap1bHTap1bLFixed

Pattern

Clk<1> Clk<2> Clk<3> Clk<4> Clk<5>

1.2V DVDD 2.4V/1.2V DVDD

1.2VCVDD

Level Shifter & Pre Driver

8

4

4

4

4

88

8

FFE Control

8 Sel.

1.2VCVDD

25Gb/s 8:1 CMOS Serializer

• Quadrature quarter-rate architecture eliminates high-speed retiming before final 2:1 MUX

÷2

FF

FF

FF

FF

6.25GHz Quad. CLKs

DEVEN

DODD

DOUT

12.5GHz

2:1

÷22:1

÷22:1

÷22:1

÷2

0º

180º

90º

270º

D0D4

D1D5

D2D6

D3D7

FF

FF

25Gb/s 8:1 CMOS Serializer

• Tri-state inverter-based 2:1 MUX for fast edge rate

1X 2X

2X1X

2X

CLKB

CLK

DEVENDODD

-80 -60 -40 -20 0 20 40 60 80

0

0.5

1

Time (ps)A

mpl

itude

(V)

Pass-Gate MUX

Tri-State MUX

1.5Simulated 25Gb/s DOUT

DOUT

Heterogeneous Integration

56

• Hybrid CMOS-Photonic packaging (<0.5mm bond-wires)

• Stable optical coupling using vertically-attached fibers

25Gb/s Optical Measurement

57

MRM-1, FFE Off, 4.4V Swing QF=4.4, ER=5.3dB

MRM-1, FFE On, 4.4V SwingQF=8.4, ER=6.8dB

500µW 16ps500µW

16ps

Test Channel 1 w/o FFE

Test Channel 1 w/ Asymmetric FFE

Challenge III: Wavelength Stability

• Modulation efficiency depends strongly on wavelength• ER degradation due to temperature fluctuation• Closed-loop control is necessary for robust operation

Average Power Thermal Stabilization

Thermal Tuning Algorithm

Thermal Tuning Algorithm

Thermal Tuning Test

Thermal Tuning Test

Dynamic Thermal Tracking Test

Dynamic Thermal Tracking Test

Documents

ECEN689: Special Topics in Optical Interconnects Circuits ...spalermo/ecen689_oi/lecture11_ee689_rrm_tx.pdfECEN689: Special Topics in Optical Interconnects Circuits and Systems Spring