High Speed Mixed Signal IC Design notes set 9 ICs for ... · Demultiplexer and interface with...

ECE145C /218C notes, M. Rodwell, copyrighted 2008

High Speed Mixed Signal IC Designnotes set 9

ICs for Optical Transmission

Mark RodwellUniversity of California, Santa Barbara

[email protected] 805-893-3244, 805-893-3262 fax


ICs for Optical Transmission: topics

Systems:block diagrams, eye diagrams, waveforms

Transmitters:Laser diodes, diode driversOptical modulators, modulator drivers

ReceiversPhotodiodesReceiver block diagrams: AGC and limitingAGC amplifier and detector, SNR constraints on limiting amplifier designLimiting amplifiersTIA: SNR analysis, topologiesDC restoration loopsSNR analysis; Personik Integrals

Timing recoveryPLLs, phase detectors for data steams, frequency locking

Mux and Demuxbasic structures, timing thereof


Digital Optical Fiber Links

demux receiver, er, transmittmux, :link optical of form Typical

nm) @1550 dB/km 0.17 nm, @1310 dB/km 0.3(~ losseslow have fibers Opticaleffect) skin notes; (see sfrequencie highat losses high have esCopper wir

:Motivation

detection (power) Incoherent(On/Off) ModulationIntensity Binary

ion transmissDigital:(2008) operation of ModePrevalent


Typical Signal Format: NRZ Modulation

optical,0optical,1 /ratio Extinctionzero quitenot is "0"for intensity Modulated

sent. 0 vs1 ecommunicat low to / high modulated isIntensity period,bit each In

PP=

sequences possible allfor ctoriesdata traje Representsperiod.bit one modulo time vs. waveformrepresents pattern Eye


Optical Transmitter: Directly Modulated Laser Diode

exceeded. iscurrent d thresholonceslowly only increases voltageforwardat except th

diode,a PN of thoseresemble sticscharacteri V-I diodeLaser

Hzinfrequency optical ,efficiency quantum ))(/( :sholdlaser thre exceeds

current drive noutput whelight in increase sharpa shows Diode

current. drive AC and bias of ionsuperpositby driven is Diode

==

−≅

νη

νη thoptical IIqhP


Laser Diode Characteristics

links. speed-high range-longfor attractive less lasers makes (chirp) modulation h wavelengtUndesired

(2008). bandwidth GHz 25 exceed lasers diodeFew currents. highat increases damping order;-2nd is Response

collapses. saturates, then---increasescurrent bias as increases Bandwidthcurrent. bias upon depends reponse modulation signal-smallLaser

.resistance series ) 10-5(~ smalla withseries in diode ideal anby edapproximat- wellare parameters electricallaser

model,complex morea suggest equations ratelaser Though

Ω


Laser Transmitters

ringing. line control to )( padding series needslikely and longlikely isct Interconne

die. same onnot aredriver &Laser

lasers oldlow thresh modern withneedednot loops DCbackside.laser ongenerally diodeMonitor

bias.laser maintain toloopfeedback DCuses sometimes Form;Basic

0ZRR diodeterm =+


Optical Modulators: EAMs

light. absorbed thengrepresenti resistance parallela but with diode, biased-reversea of that is model cal Electrin.attenuatio optical the variesbias reverse theVarying region. I thein waveguideoptical an

containing junction PINbiased-reverse A :modulators Absorbion-Electro

train.pulse and bias DCcombined withdriven and load, parallel Ohm 50a withloaded is Device

C

control

absorbed

dVdP

hqRν

=/1


Optical Modulators: Electo-optic Modulators

[ ]

[ ] driver.power -high need :modulators Gb/s 40for V 6-4~ is

)/cos(1)2/(intensityoutput changes shift, phase optical induces Voltage

field.- Eapplied th weakly wiesindex vari refractive waveguideOptical: Modulatoroptic-Electro

)2cos(1)2/()(cos );(power opticalOutput

)cos( :intensity field- EopticalOutput recombine. shift, phase relativea paths give , waveguideopticalsplit

:eterInterferom

22

π

ππ

φφ

φ

VVVPP

PPPEPEE

signalinout

ininoutoutout

oout

+=

∆+=∆=∝

∆=


Drivers for Electo-optic Modulators

al.differentior ended-Single HEMTInGaAs/InPor HBTInP

amplifier. ddistributea alwaysNearly :I)(V, drive high and bandwidth high of nCombinatio


Optical Receivers: PIN Photodiodes

DAC

qhqh

Ph

qI optical

/

nm 1550at V 800.0/ nm 1310at V 954.0/

region.-I of onilluminati withdiode biased-Reverse

ε

λνλν

νη

=

====

=

optph Ph

qIνη

=


Optical Receiver; with AGC

bandwidth system decision withinnoise minimize toas soce,interferen lintersymbo zerofor sufficient minimum theis bandwidthFilter *

points timedecisionset to PLL latch M/S voltagein quantize toComparator

signal from DCremove :loop restore or DC coupling AC shown)(Not rate)(bit 75.0~ to from noisebandlimit to*filter pass-Low

power received of range accomodate gain; variable withchainamplifier Linear widebandcurrent, noiseinput low :amplifier anceTransimped

:Functions

+

⋅Bflow


Limiting Optical Receiver

shownnot ; needed restore or DC coupling AConcompensati dispersion accomodatenot does Form

y.sensitivit degradespoint limiting prior to 0.75 exceeding Bandwidthstage. limitingfirst ispoint comparison voltageEffective

limiting. into driven stages more increased, ispower input Asnoise. bandlimits ; of 75%~ bandwidth hasamplifier Each

signals.input stronger for limit amplifiers instead, AGC; Nooperation, speed-highestfor formSimpler

B

B

⋅>


AGC Amplifier: Bipolar

block.upper fromreductioncurrent scompensate

reduced, is gain as DCAdds:oncompensati DCis halfLower

shunt.current variable pair with alDifferenti

:cell AGC basic is halfUpper


AGC Detector: Bipolar

CTIqkTVV

I

bitopeakpeakinout //2/kT/q, nlarger tha much inputsa for that shows lecture) in(work Analysis

. be toall sourcescurrent by forced are BJTs2 thein currents DC

,

0

−−= −


Limiting Amplifier Chain: Bipolar

shown. thanmore stages; TASTIS multiple AnticipateTAS/TIS.or steering-current bemight s /receiverdriversct Interconne

shift.-levelinput Note


Limiting Amplifier Chain: CMOS & NMOS

me.ask feasible; also are forms alDifferenti2/at levels DC ddV


DC Restoration Loop: Instead of AC Coupling

RCAffjf

fjfA

AsRCAsRCA

sRCAsRCAsRC

TTA

sRCATsRCAA

vlowlow

lowv

v

vv

v

vCL

v

vOL

π

β

β

2/ where/1

/

/1/

/1/

11

:Gain Loop-Closed

/ :onTransmissi Loop 1/ :Gain Reverse :Gain Forward

=+

=

+=

+=

+=

===


Why TIA input stage ?

.../)()()2(/4)(

effect)(Miller )1(2/122 +++=

+=

fEEEEinfII

vfinhigh

RfSfSfCRkTfS

ARCf

nnnnininπ

π

smaller) is because noise (more

.../)()()2(/4)(

bandwidth) samefor smaller (need 2/122

R

RfSfSfCRkTfS

RRCf

LEEEEinLII

Linhigh

nnnninin+++=

=

π

π

notes. noise see reader; left to analysis noise TIA Detailed

(BJT) ...2)(4/2)(

(FET) ...)(4/4)(2 ++++=

++++Γ=

bbbexbbmEE

igsmEE

RqIRRkTgkTfS

RRRkTgkTfS

nn

nn


Wideband TIAs: CMOS & NMOS

fRlarger permits gain, voltageloop-openlarger design; rate- Lower:Rightrates.bit highfor very designs widebandgain,-low are designs 2Left


Wideband TIAs: Bipolar

noise. less feasible larger higher rates. moderatefor design bandwidthlower gain,-higher :Right

rates.bit highfor very design widebandgain,-low :Left

→→ fv RA


Wideband TIAs: Output DC Level

accept... can chain TASTIS levels input DChat Consider w). ,V 0 ,( of levelsoutput DChas sequence This φφ −+

damped.badly :shifters-level EFcascaded withDesignsslow. :diodesmany withDesigns

shown. TIAs all withused /arebe can shifters-levelSimilar


Receiver Sensitivity

Bratebit theof 75%~ bandwidth having filters channel assumes This12.0 68.0

rateerror bit uncoded 10for 6SNR :where

Then

)( form theof noiseinput Assumeset. notes subsequenta in derived be willThis

32

33

22

9-

2min

2

≅≅⋅+⋅=

==

⋅⋅=

+=

IIIBbBIaI

Q

IQqhP

bfafS

n

n

II inin

ην


Timing Recovery

data incoming theofperiod pulse average the toVCOa essynchroniz System

D Q

C Q

VCO

3.8 Gb/s

3.8 GHz PLL

decision ckt

DOD /DFD

Data

PLL

data. modulated oinherent treversals phase of tolerant bemust detector Phase


Demultiplexer and interface with timing recovery


Tree demultiplexer

skew. mingprevent ti to required are latches S that M/S/Note

High Speed Mixed Signal IC Design notes set 9 ICs for ... · Demultiplexer and interface with...

Documents

Transcript of High Speed Mixed Signal IC Design notes set 9 ICs for ... · Demultiplexer and interface with...