modeling free space optoelectronic systems using ptolemy · overview chatoyant is a computer aided...

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Modeling Free Space OptoelectronicSystems Using Ptolemy

☛ Funding: National Science Foundation- MIP-9421777

Steven P. Levitan Philippe J. MarchandDonald M. Chiarulli Chi Fan

Tim P. Kurzweg Fredrick B. McCormickMark A. Rempel

Departments ofElectrical Engineering &

Computer Science

Department of Electrical &Computer Engineering

[email protected] [email protected]

http://kona.ee.pitt.edu/steve http://soliton.ucsd.edu

University of Pittsburgh University of California, San Diego

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Overview

Chatoyant is a computer aided design tool for the design ofFree Space Optoelectronic Information processing (FSOI) Systems.

✵ Simulation - Analysis - Synthesis - Interface

☛ Enable the modeling of FSOI systems without costlyprototyping

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Laser Source

SpotGenerator

detectordriverdigitallens lens lens lens arrraylogic electronics

digitallogicelectronics

receiverSLM

modulatorarray

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Outline

1. Free space optoelectronic information processing systems2. Design Issues3. Approach/Method4. Signal and Component Models

5. Chatoyant: System Modeling

6. Simulations using Ptolemy7. Conclusions

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What’s the Problem?(in O/E systems)

☛ O/E information processing systems are hard to design✵ Heterogeneous systems✵ Expensive to prototype ($’s and time)

☛ Hard to simulate✵ Systems cross technology boundaries✵ optical - mechanical - electronic, more

☛ Solution:✵ System level prototyping environment✵ Heterogeneous tool integration✵ 1st order - trade offs (architecture vs. technology)✵ Interface to “point tools” for details

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“System 5” Photo

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“System 5” Physical Design

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“System 5” Optical Design

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“System 5” Functional Design

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“System 5” Electrical Design

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Design Issues

☛ How do these interact?

☛ How do we evaluate designs to perform architectural vs.technological (vs. cost, speed, power, etc.) trade-offs?

ElectronicsOpto-

electronicsOptics

PackagingMechanics

Thermal

Functionalmodels

Analyticmodels

Imageformation

Area, Volume Power density

Logic, Timing Gaussianbeampropagation

1st orderlayout

1st orderthermalexpansion

Circuit Physicalmodels, Datafitting

Ray tracing,Diffractionanalysis

Tolerancing Finiteelementanalysis

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Requirements for an O/E CAD System

☛ Support heterogeneous implementation domains

✵ Analog/digital electronics✵ Optoelectronics✵ Free space optics✵ Physical 3D layout✵ Thermal/power analysis

☛ Support multiple design levels

✵ Functional - high level✵ Signal - mid level✵ Physical - low level

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Approach

☛ Build a system level modeling tool to predict performanceand analyze technology vs. architecture trade-offs

✵ Develop 1st order analytical models for optoelectroniccomponents (drivers, transmitters, lenses, detectors,receivers, etc.)

✵ Develop and integrate numerical/physical models foroptoelectronic devices (VCSELs, Modulators, etc.)

✵ Develop a hierarchical & modular software tool usingPtolemy engine

✵ Provide interfaces to existing tools (Spice, Code V, etc.)✵ Integrate mechanical tolerancing and packaging models

as the technology evolves

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Chatoyant

☛ System level modeling tool✵ Models for signals✵ Models for components

☛ Predict system performance✵ Speed, power, weight, volume, cost, error-rate

☛ Understand and analyze trade-offs✵ Perform optimizations✵ Synthesize optics

☛ Interface to/from “point” tools (e.g., Code V)

☛ Provides a balance between accuracy and speed

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Chatoyant Stars in Ptolemy

Modulators Detectors Lenses Lenslets

Area Detector Size Focal Length Focal Length

Spacing Detector Spacing Diameter Diameter

Lambda Distance Distance Distance

Spotsize x, y offsets x, y offsets x, y offsets

Filename Radius of Integration Spacing

Gauss/Ray R, C, A Number

XMgraph

XscopeIdealLensArray PowerGridVCSEL

ModArray Lens DetectArray

ModArray

output

output1noisechannel TkPlot

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Modulators*

Pabs modeled with Lorentzian lineshape

* C. Fan, et. al. “Digital free-space optical interconnections: a comparison of transmitter technologies”, Applied Optics 34(7) pp.3103-3115, 10 June 1995.

Modulator Input -100MHz

Set 0

Y

-9X x 100.00

2.00

4.00

6.00

8.00

10.00

0.00 20.00 40.00 60.00 80.00 100.00 120.00

Driver

Poptic

Pin

Vmod

∆VPabs

Modulator Output - 100MHz

µW

-9X x 10

780800820840860880900

0 20 40 60 80 100 120

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 1 2 3 4 5 6 7 8 9 10

10v

0v

Incident Power (mW)

Abs

orbe

d P

ower

(mW

)

Pabs V( )Pink V( )

1Pin

A I⋅ s V( )-----------------------+

--------------------------------= Prefl Pin Pabs–=

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Vertical Cavity Surface EmittingLasers(VCSEL)

Driver

Poptic

∆P

0

2

4

6

8

10

12

14

16

0 5 10 15 20 25 30 35 40 45 50

Out

put P

ower

(mW

)

Input Power(mW)

2.5V

4V

Pout

ηLI Vt⁄1 ηLI Vt⁄–( )

--------------------------------- Pin ItVt–( )=

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MQW/PIN Photo-diode Receiverswith Transimpedance Amplifiers*

* A.V. Krishnamoorthy et.al. IEEE Photonics Technology Letters, 7(11), Nov 1995

time

0.0 20.0 40.0 60.0 80.0 100.0

nS

-1.0

0.0

1.0

2.0

3.0

4.0

5.0

6.0

V v(100) v(102) v(106) v(109)

Stage1Ip

Poptic VDD

Stage2 Stage3a b c d

ab

c

d

Cp

Rf

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Ptolemy Simulations: 4f system

ModArray Lens Lens PowerGrid

f=.01m 2f=.01m f=.01m

Driver

Poptic

Pin

Vdd

∆VPabs

Ip

∆Vo

Poptic

Vdd

Amp

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Gaussian Beams(good approximation for lasers)

Intensity - radial symmetry, propagation in z:

Waist size:

Rayleigh Range (~ depth of focus):

z

xy

I0

W0I r z,( ) Io

W0W z( )-------------

2 2r2

W2

z( )----------------–exp=

W z( ) W0 1zz0-----

2+

1 2⁄=

z0

πW02

λ------------=

2z0

zW0

√2W0

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Optical Power Simulations

20µm spotModulators (µW)

10µm Detectors 20µm Detectors 35mm Detectors

771 771 906 360 422 422 703 826 826 771 905 905

771 906 906 422 422 360 826 826 703 905 905 771

906 906 771 422 360 360 826 703 703 905 771 771

40µ(modulator volts) (integrate intensity)

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Dynamic Performance Analysis

Lens Lens DetectArray XMgraph

Xscope

ModArray

output

output1

XMgraph

f=.01m 2f=.01m f=.01m

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Time Domain Analysis

☛ Method used for dynamic response of each of the modulesin the system.✵ Example: transfer function for single stage

transimpedance amplifier:

✵ Convert to time domain✵ Number of points in piece-wise linear approximation is

user defined variable

Vo s( )R f

1R f C

A-----------

s+

----------------------------- Poptic s( )⋅=

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Dynamic Simulations at 100 / 300 MHz


-9X x 10

780800820840860880900

0 20 40 60 80 100 120


µW

-9X x 10

780800820840860880900

0 10 20 30 40

Detector Output - 100MHz

V

-9X x 10

3.103.203.303.403.50

0 20 40 60 80 100 120

Detector Output - 300MHz

V

-9X x 10

3.103.203.303.403.50

0 10 20 30 40

Eye Diagram - 100MHz

V

-9X x 10

3.103.203.303.403.50

0 2 4 6 8 10


V

-9X x 10

3.10

3.20

3.30

3.40

3.50

0.0 0.5 1.0 1.5 2.0 2.5 3.0

µW

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5µm Detectors On-center v.s. 20µmDetectors Off-center

20µm Modulators 5µm Detectors Misaligned Lens

771 771 906 113 133 133 193 227 227

771 906 906 133 133 113 227 227 193

906 906 771 133 113 113 227 193 193


mV

-9X x 10760780800820840860880

0.0 0.5 1.0 1.5 2.0 2.5 3.0


V

-9X x 101.30

1.35

1.40

1.45

1.50

0.0 0.5 1.0 1.5 2.0 2.5 3.0

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VCSELs

20µm Source Power (mW) 35µm Detectors(mW) 20µm Detectors(mW)

50 50 10 14.20 1.58 1.58 12.95 1.44 1.44

50 10 10 1.58 1.58 14.20 1.44 1.44 12.95

10 10 50 1.58 14.20 14.20 1.44 12.95 12.95

VCSEL Output - 100MHz

mW

-9X x 102468

101214

0 20 40 60 80 100 120

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Gaussian Beam Clipping by a CircularAperture: Diffractive Effects

Power loss related to the size of the aperture:

ratio of diameter of aperture to waist size at aperture:

kW0

Z0

Z

Pnew P 1 e2k2

––

=

k Dapt 2Wapt( )⁄=

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Effective Waist and Resultant IntensityDue to clipping

1.0 1.5 2.0 2.50.7

0.8

0.9

1.0

1.1

1.2 P5 P10 P30

EF

FE

CT

IVE

WA

IST

K VALUES

1.0 1.5 2.0 2.50.5

1.0

1.5

2.0

2.5 PI5 PI10 PI30

EF

FE

CT

IVE

IN

TE

NS

ITY

K VALUES

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Conclusions

☛ Optoelectronic devices and integration technologies areavailable now

☛ Tools are necessary to enable the transition from devices tosystems without costly and time consuming physicalprototypes.

☛ A system level tool provides for performance analysis,with extensions to/from “point tools”

☛ Interactions with industry device and system designers iscritical

modeling free space optoelectronic systems using ptolemy · overview chatoyant is a computer aided...

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