WOCC-2005

High Performance, Low Cost PIN, APD Receivers in Fiber Optical Networks and FTTx Applications

Hui Nie4/23/2005

WOCC-2005

Receiver Applications

Long-Haul Backbone

MetropolitanBackbone

Metropolitan Access

EnterpriseAccess

Back Bone Core Nodes LR and VLR Interface Cards

Metro Transport Line Cards

Metro Access Line

Cards (ADMs)

Transceivers

Transponders

OXCs

FTTx Applications/Demands also heating up!

WOCC-2005

Photodetectors and Optical Receivers

IntroductionPhotodetectors Technologies

OverviewsPIN PhotodiodesAvalanche Photodiodes (APDs)APD Design Trade-offs

Photoreceivers TechnologiesOverviewsHigh Performance MSA Compliant Receivers & ROSAs

PIN, APD ROSA in FTTx Applications

WOCC-2005

Photodiodes Technologies

Overview

PINs

APDs

Etch-Regrowth Planar SACM APDs

Buried-Mesa APDs w/ Regrowth Guard RingResonant-Cavity APD w/ Thin Multiplication Layer

Wafer-Fused SHIP APD

InGaAlAs/InAlAs Superlattice APDWaveguide APD

Transit Time Bandwidth

RC Time Bandwidth

Surface-Illuminated PINsWaveguide PINsTraveling-Wave PINs

WOCC-2005

Photoreceiver Sensitivities v.s. Bit-Rate

Bit Rate (Gbit/s)0.1 1 2.5 10 20 40

Sens

itivi

ty @

BER

=10-

9 (d

Bm

)

-50

-40

-30

-20

-10 PIN OEICPIN HybridEDFA PreampAPD HybridQuantum Limit

WOCC-2005

-50

-40

-30

-20

-10

0

0 20 40 60 80 100 120 140

Transmission Length (km)

Rec

eive

d Po

wer

(dB

m)

1.3m 1.5m

0.25dB/km

0.3 dB/km

0.4 dB/km0.6 dB/km EDFA+PIN

APD+Amp. (+EDC)

PIN+Amp.

10 Gb/s Receivers Sys.

Dispersionlimit

Receiver Systems & Applications (10Gb/s Systems)

WOCC-2005

Industry Standard Top-illuminated Planar PIN

InP Substrate n++InP Buffer layer n -

InGaAs Absorption

Cap Layer Zn Diffused p+

p+ Metal Contact

Bonding pad

SiNx

AR coating

Dielectric coating

WOCC-2005

High-Speed Surface-illuminated Mesa PINs

Light Input

SiNx Coating

InP:Fe Substrate

n InP

p InP

i InGaAsPMGI

n-Metal

Metal ReflectorAlloyed p-Metal

Air-BridgedMetal

InGaAs/InP Graded Double Heterostructure p-i-n Superlattice Interface Grading Small Mesa Size

WOCC-2005

Waveguide Photodetectors (WGPDs)

Side-IlluminationOptimize Bandwidth and QE IndependentlyMultimode Ridge WaveguideMicro-Lenses Fiber Coupling, Small Spot SizeExternal QE>70%Bandwidth>100GHCan be integrated OEIC Photoreceiver

p+ InPp+ InGaAsPi InGaAs -0.2 mn+ InGaAsPn+ InPpolyimide

WOCC-2005

Traveling-Wave Photodetectors (TWPDs)

Electrical Waveguide Concomitant with Optical WaveguideMatch Between Electrical Wave and Optical Wave (50)Eliminate RC Time Tradeoff Higher Saturation PowerBandwidth=172 GHz, QE~40%Small Geometry w=1 m

1 m

WOCC-2005

Multiplication Process Enhance Performance

Multiplication region

Distance

Tim

e

p+ n+i

+

Injected electron

Electric field

Secondaryhole

Primary andSecondary electron

x

E(k)

+

+

Gain process will slow down transit-time!

Figure of Merit: Gain-Bandwidth Product

High Electrical Field near avalanche breakdown!

WOCC-2005

APD Photocurrent & Gain vs. Temperature

1.E-07

1.E-06

1.E-05

1.E-04

0 10 20 30 40 50 60 70Reverse Voltage, volt

Curr

ent,

A

1

2

3

4

5

6

7

8

9

10

11

12

13

Gai

n

n40C n20C 0C 25C 50C 85C M_40C M_20C M0C M25C M50C M85C

WOCC-2005

Receiver Sensitivity vs. APD Gain, TIA noise

-36

-34

-32

-30

-28

-26

-24

1 5 9 13 17 21 25 29APD Gain

Rec

eive

r Sen

sitiv

ty (d

Bm

)

Sen(120nA)Sen(250nA)Sen(350nA)Optimum-M

Locus of Optimum APD gain

APD Noise < TIA Noise APD Noise > TIA Noise

How does APD Enhance Rx Sensitivity?

WOCC-2005

Planar Separate Absorption, Multiplication (SAM) APD Structure

n+ InP Buffer

n- InGaAs abs. layer

n- InGaAsP layer

n+ InP Sub.

n+ InP Multi.

n- InP cap layer

AR coating

n-metal

p-metal

SiNx layer

P+ Diffusion

Guard Ring

WOCC-2005

Planar SACM/SACGM APD

InGaAs/InP Two-step MOCVDPlanar Structure Etch and Regrowth Charge and Multiplication RegionDiffusion controlled Multiplication Layer (single Diffusion or Well Etching-Diffusion) Xd ~ 0.2-0.4 mGB product = 122 GHzNoise Ratio k~0.45No Implant

n-Metal AR SiO2

p+ InP

n- InP Multiplicationn InP ChargeGrading Layer

n InGaAs

n- InGaAs Absorption

n- InP Buffern+ InP Substrate

Xd

Xj

tInGaAs

tmesatcharge

tBuffer

WOCC-2005

Resonant-Cavity InGaAs/InAlAS SACM APD

Resonant-Cavity StructureHigh QE ~ 75%Mesa IsolatedSACM ConfigurationThin InAlAs Multiplication Region (200 nm)Lower Noise k ~ 0.18Bandwidth>20 GHzHigh Gain-Bandwidth Product

Polyimide

n+ InAlAs/InGaAs DBR

h

Probe Metal

n+ InP Buffer Layer

Semi-Insulating InP Substrate

Metal RingContact

Dielectric DBR

InGaAs Cap Ring Contact

APD Active Region

n+ InAlAs

200 nm InAlAs Multiplication

60 nm InGaAs Abs. Layer

p+ InAlAs

150 nm p-InAlAs Charge

50 nm InAlAs Spacer

50 nm InAlAs Spacer

WOCC-2005

Wafer-Fused SHIP APDSilicon HeterointerfacePhotodetector (SHIP)

Wafer-Fused SiMultiplication Region

Mesa Isolated (20-30 m)

Backside Illumination

Bandwidth= 13 GHz

GainxBandwidth= 315 GHz

Reliability Issue

Au/Zn Contact

PMGI

p+ InGaAsn- InGaAs

p-type Implant

Bonding Interface

n-type Si Substrate

WOCC-2005

Buried Mesa APD with Regrown Guard-Ring

Mesa Etch and Regrowth Isolation Layer (Patented)No Diffused Junctions and Multiple Implanted GRsRegrowth p-InP Guard Ring + Implanted Guard RingBandwidth< 4GHz for OC-48 Applications (2.5 GHz)GB Product=37 GHzSensitivity= -33 dBmExcess Noise Factor=0.4

P+-InP

n-InP Mulutplication

InGaAsP

i-InGaAs

n-InP

Regrownp-InP

Proton ImplantIsolation

WOCC-2005

Planar InGaAlAs/InAlAs MQW APD

Ti Implanted Guard-RingAR Coating

p-contact

Sn Bump

n+ InAlAs Cap

InGaAlAs/InAlAsSuperlattice

p+ InPField Buffer

P- InGaAsp+ InPSI-InP Substrate

Zn DiffusedRegion

SI InP SubstrateInverted Mesa JunctionTi Implanted Guard-Ring to Decrease p-concentration of Field-Buffer Layer Dark Current Increase Due to Implantation SiNX Passivationp+ Zn Diffusion IsolationContact Metal DepositionFlip-Chip BondingCd=0.15pF, Cp=0.06pFRL=25 to achieve Bandwidth=15.2GHzId=0.36A@ M=10GB Product = 120GHz

WOCC-2005

Waveguide APD

Multimode Waveguide StructureMesa Etch and SiNx PassivationInAlAs/InAlGaAs MWQ Multiplication Layer ~0.25 mInGaAs Abs. Layer ~ 0.3 mTop and Bottom InAlGaAs Cladding Layer ~ 0.8 mBandwidth= 20 GHzGB Product= 160 GHzLarge Dark Current

1 A @ 90% VBEdge Coupled w/ Lensed Fiber (3 m Spot Size)

20 m

p+ InAlGaAs

n-MetalInAlGaAs

InAlAs/InAlGaAs MQW

n+ InAlGaAs

InP Substrate

SiNx

6 mp-Metal

WOCC-2005

Real-World APD Device Specifications

Quantum Efficiency, ResponsivityGain characteristicsBandwidth @ M=10,12 when PIN is low (Sensitivity)Bandwidth @ M< 4 when PIN is high (Overload)Primary Dark CurrentExcess Noise FactorCapacitanceBreakdown Voltage

WOCC-2005

Performance of APD comes with price!

Trade-off 1: Bandwidth~ Responsivity InGaAs Absorption Layer Thickness

Trade-off 2: RC Bandwidth ~ Transit Time BandwidthInGaAs, InP layer thicknessDevice geometry

Trade-off 3: BW@ M~10 ~ BW@ M~3Multiplication layer dopingDiffusion junction depth control (Ehet control)

Trade-off 4: Breakdown Voltage ~ Thickness, DopingInGaAs, InP layer thicknessMultiplication layer doping

WOCC-2005

APD Design- Balance between Trade-offsAPD Bandwidth vs. Gain

1

10

1 10 100

Gain

3 dB

Ban

dwid

th (G

Hz)

WOCC-2005

TriQuint APD Chips

Over than 15 years of design and volume manufacturing APDs used

in commercial communication systems (AT&T Bell Labs -> Lucent ->

Agere -> TriQuint -> CyOptics?)

High quality, high yield and low cost MOCVD epi

Reliability proven with > 5000 hrs aging and >15 years of field use

High-speed automated wafer level electrical and optical probing

systems

Receiver performance demonstrated with high performance APD

chips

WOCC-2005

Failure Rates vs. Activation Energy

Failure Rate vs. Ea

0.1

1

10

100

1000

0.4 0.5 0.6 0.7 0.8 0.9 1Activation Energy, eV

Proj

ecte

d Fa

ilure

Rat

e,

FIT

MOCVD APD

With the estimated Ea of 0.96 eV, these devices have very small FIT (< 1 FIT).

With >5000 hrsaccelerated aging test, activation energy is extracted.

WOCC-2005

TriQuint Receiver Product Family

Traditional butterfly package receiver

MSA small-form-factor surface-mounted Receiver

Ceramic packaged ROSA

TO-can based ROSA

WOCC-2005

APD & PIN MSA Receivers

Key AdvantagesMSA Small Form Factor

Surface Mount

High Sensitivity & Overload

R195A typical 26 dBm, -3dBm

R195P typical 19 dBm, +1 dBm

Small Group Delay Variations

Good Linearity

700mV Output Voltage Swing

Excellent OSNR Performance

WOCC-2005

MSA APD Receivers

-26 dBm, M=10 9.953 Gb/s, 1550 nm, 2E31 1 PRBS

Eye

-3 dBm, M=3

BER

TriQuint R195A BER vs. Temperature @ 9.95Gb/s

0.08 6

0.1 8 6

0.2 8 6

0.3 8 6

0.4 8 6

0.5 8 6

-32 -30 -28 -26 -24 -22 -20Power (dBm)

BER

T= 0 C

T= 25 C

T= 50 C

T= 70 C

10-12

10-4

10-8

10-6

10-10

< 1.0 dB Penalty from 25C to 70C

WOCC-2005

10G APD Receiver OSNR Performance

Tx

9.95328 Gb/sM

Attn.EDFA

Attn.M

R195ARxBERT

OSABPF

LM(Vth Adjust)

R195A BER at 18dBm OSNR (Vth optimized)

0 .0 8 6

0 .1 8 6

0 .2 8 6

0 .3 8 6

0 .4 8 6

0 .5 8 6

-22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0

Power (dBm)

BER

unit 1, opt. -20dBmunit 2, opt. -20dBmunit 3, opt. -20dBmunit 4, opt. -20dBmunit 5, opt. -20dBm

10-12

10-4

10-8

10-6

10-10

WOCC-2005

BER vs. Vpd over Temperature

* For each temperature the optical power was adjusted to obtain a BER in the range of 4e-11 to 9e-11.

TriQuint R195A BER vs. Vapd, 9.95Gb/s, T=0, 25, 50, 70 OC

0.08 6

0.1 8 6

0.2 8 6

0.3 8 6

0.4 8 6

0.5 8 6

20 21 22 23 24 25 26 27 28 29 30 31 32Vapd (V)

BER

T= 0 C

T= 25 C

T= 50 C

T= 70 C10-12

10-4

10-8

10-6

10-10

WOCC-2005

Next Generation MSA Receiver & ROSA

-28 dBm, M=9 9.953 Gb/s, 1550 nm, 2E31 1 PRBS

Eye

+1 dBm, M=3

BER

-32 -30 -28 -26 -24 -22 -20

Power (dBm)

BER

10-12

10-4

10-8

10-6

10-10

7/4/2005 32WOCC-2005

Fiber Transmission Experiments

100 km

(a)

(b)

0 km

Eye diagrams back-to-back, and after 100 km transmission. (a) Optical. (b) Electrical.

7/4/2005 33WOCC-2005

Path Penalty after 100 km Fiber

Receiver Sensitivity vs. APD Vpd (B/B, 100Km)

-30-29.5

-29-28.5

-28-27.5

-27-26.5

-26-25.5

-25-24.5

-24

24 24.5 25 25.5 26 26.5 27 27.5 28 28.5 29 29.5 30 30.5 31 31.5 32

APD Bias (Volt)

Rec

eive

r Sen

sitiv

ty (d

Bm

)

00.2

0.40.60.8

11.21.4

1.61.82

2.22.4

Path

Pen

alty

100

km F

iber

(dB

)

B2B

100Km

WOCC-2005

PIN & APD ROSAs

Low cost, high performanceXMD compatible3.3V TIADetector on carrier

TIATIA

APD flip-chip On carrier

APD flip-chip On carrier

WOCC-2005

100k

1M

10M

100M

1G

622MB-PON

G/GE-PON

ADSL

2000 20011998

Speed(bit/s)

final

final

IEEE802.3

FSAN

FSAN,ITU-T

2003

155MB-PON

100M-MC

GbE-MC

10M-MC

SS)SS)

STMPON

Under d

evelop

ment

Com

mer

cial

prod

uct

G-PONGigabit-PONFSANGE-PON:GigaEthernet-PONIEEE802.3

FSAN

Advancement in AccessAdvancement in Access

Under r

esearc

h

WDM-PON

WOCC-2005

PON (Passive Optical Network)A single, shared optical fiber serving 32 customers.

Passive because no active electronics in access network, except for the end points.

Med-SmallOffice

Residential

Circuit/PacketSwitch

Optical LineTerminal (OLT)

EthernetN x POTS

OpticalNetworkTerminal

(ONT)

ONT

ONTCentralOffice

Splitter

FTTP Architecture

1550 nm broadcast

1490nm data

1310 nm data

WOCC-2005

Market: North America: 1-2M home for 2005Verizon: About 150k Subscribers, 1M home passed. Plan to add 2M home by 2005SBC: Field trial on 2004, and plan add 300K home on 2005

Japan: 2-3M homes for 2005NTT: Plan spend $48B for 30M subscribers by 2010, add 1-2M subscribers on 2005Yahoo BB: Strong competitor with 2M subscribers in 2005 plan

Korea: Plan to add 10M subscribers by 2007, but no detail plan yetChina: Still on earlier stage of deployment, a lot of trialsEurope: About 400K Subscribers, not high level growth can see in the near future

Equipment:Optical Network Terminal (ONT):

1310 DFB or 1310nm FP for upstream 1490nm PD 1550nm analog detector for receiver

Optical Line Terminal (OLT):1490nm DFB for downstream data transmissionAPD for receiving

Cost, cost and cost while not sacrificing performance!

FTTP Market

1310nm FP, DFB or1490nm DFB

1.25G APD or PIN

WOCC-2005

EPON & GPON Requirements

EPON & GPON Different RequirementsPIN mostly in ONT sideAPD mostly used in OLT sideAPD will be more common due to split ratio increases

1000BASE-PX10 1000BASE-PX20 G.984.2Distance 10 Km 10 Km 20 Km

Attn Range 5-20dB@ upstream

5-20dB@ upstream

Class A: 5-20dBClass B: 10-25dBClass C: 15-30dB

OutputPower

ONT: -1 ~ +4 dBmOLT: -3 ~ +2 dBm

ONT: -1 ~ +4 dBmOLT: +2 ~ +7 dBm

ONT: -2 ~ +3 dBm @ ClassBOLT: +1 ~ +6 dBm @ ClassB

ReceivePower

ONT: -24 ~ -3 dBmOLT: -24 ~ +1 dBm

ONT: -24 ~ -3 dBmOLT: -27 ~ -6 dBm

ONT: -25 ~ -4 dBm @ ClassBOLT: -28 ~ -7 dBm @ ClassB

EPON(IEEE 803.2ah)

GPON(ITU-T)