High Performance, Low Cost PIN, APD Receivers in Fiber Optical ...

High Performance, Low Cost PIN,
APD Receivers in Fiber Optical
Networks and FTTx Applications
Hui Nie
4/23/2005
WOCC-2005

Receiver Applications
•Back Bone Core Nodes LR and VLR Interface Cards
•Metro Transport Line Cards
•Metro Access Line
Cards (ADM’s)
Long-Haul
Backbone
Metropolitan
Backbone
Metropolitan
Access
Enterprise
Access
•Transceivers
•Transponders
•OXCs
• FTTx Applications/Demands also heating up!
WOCC-2005

Photodetectors and Optical Receivers
• Introduction
• Photodetectors Technologies
• Overviews
• PIN Photodiodes
• Avalanche Photodiodes (APDs)
• APD Design Trade-offs
• Photoreceivers Technologies
• Overviews
• High Performance MSA Compliant Receivers & ROSAs
• PIN, APD ROSA in FTTx Applications
WOCC-2005

Photodiodes Technologies
• Overview
Transit Time Bandwidth
RC Time Bandwidth
• PINs
Surface-Illuminated PINs
Waveguide PINs
Traveling-Wave PINs
Etch-Regrowth Planar SACM APDs
• APDs
Buried-Mesa APDs w/ Regrowth Guard Ring
Resonant-Cavity APD w/ Thin Multiplication Layer
Wafer-Fused SHIP APD
InGaAlAs/InAlAs Superlattice APD
Waveguide APD
WOCC-2005

Photoreceiver Sensitivities v.s. Bit-Rate
Sensitivity @ BER=10 -9 (dBm)
-10
-20
-30
-40
-50
PIN OEIC
PIN Hybrid
EDFA Preamp
APD Hybrid
Quantum Limit
0.1 1 2.5 10 20 40
Bit Rate (Gbit/s)
WOCC-2005

Receiver Systems & Applications (10Gb/s Systems)
0
10 Gb/s Receivers Sys.
Received Power (dBm)
-10
-20
-30
-40
0.3 dB/km
PIN+Amp.
0.25dB/km
APD+Amp. (+EDC)
0.6 dB/km
0.4 dB/km
EDFA+PIN
Dispersion
limit
1.3µm
1.5µm
-50
0 20 40 60 80 100 120 140
Transmission Length (km)
WOCC-2005

Industry Standard Top-illuminated Planar PIN
Bonding pad
p+ Metal Contact
Dielectric coating
SiNx
Cap Layer Zn Diffused p+
InGaAs Absorption
InP Buffer layer n -
InP Substrate n++
AR coating
WOCC-2005

High-Speed Surface-illuminated Mesa PINs
• InGaAs/InP Graded Double
Heterostructure p-i-n
• Superlattice Interface Grading
Alloyed p-Metal
Metal Reflector
• Small Mesa Size

Waveguide Photodetectors (WGPDs)
• Side-Illumination
• Optimize Bandwidth and
QE Independently
• Multimode Ridge
Waveguide
• Micro-Lenses Fiber
Coupling, Small Spot Size
• External QE>70%
• Bandwidth>100GH
• Can be integrated OEIC
Photoreceiver
polyimide
p+ InP
p+ InGaAsP
i InGaAs -0.2 µm
n+ InGaAsP
n+ InP
WOCC-2005

Traveling-Wave Photodetectors (TWPDs)
• Electrical Waveguide
Concomitant with Optical
Waveguide
• Match Between Electrical
Wave and Optical Wave (50Ω)
• Eliminate RC Time Tradeoff
• Higher Saturation Power
• Bandwidth=172 GHz, QE~40%
• Small Geometry w=1 µm
1 µm
WOCC-2005

Multiplication Process Enhance Performance
Multiplication region
Distance
p+ i
n+
Electric field
Injected electron
Primary and
Secondary electron
E(k)
+
x
+
+
Secondary
hole
High Electrical Field near
avalanche breakdown!
Time
Gain process will slow down
transit-time!
Figure of Merit:
Gain-Bandwidth Product
WOCC-2005

APD Photocurrent & Gain vs. Temperature
1.E-04
13
12
11
10
1.E-05
9
Current, A
8
7
6
Gain
1.E-06
5
4
3
2
1.E-07
0 10 20 30 40 50 60 70
Reverse Voltage, volt
1
n40C n20C 0C 25C 50C 85C M_40C M_20C M0C M25C M50C M85C
WOCC-2005

How does APD Enhance Rx Sensitivity?
Receiver Sensitivty (dBm)
-24
-26
-28
-30
-32
-34
Receiver Sensitivity vs. APD Gain, TIA noise
APD Noise < TIA Noise
Locus of Optimum APD gain
Sen(120nA)
Sen(250nA)
Sen(350nA)
Optimum-M
APD Noise > TIA Noise
-36
1 5 9 13 17 21 25 29
APD Gain
WOCC-2005

Planar Separate Absorption, Multiplication (SAM) APD Structure
p-metal
SiNx layer
P+ Diffusion
Guard Ring
n- InP cap layer
n+ InP Multi.
n- InGaAsP layer
n- InGaAs abs. layer
n+ InP Buffer
n+ InP Sub.
AR
coating
n-metal
WOCC-2005

Planar SACM/SACGM APD
• InGaAs/InP Two-step
MOCVD
• Planar Structure
• Etch and Regrowth Charge
and Multiplication Region
• Diffusion controlled
Multiplication Layer (single
Diffusion or Well Etching-
Diffusion)
• Xd ~ 0.2-0.4 µm
• GB product = 122 GHz
• Noise Ratio k~0.45
• No Implant
tcharge
n-Metal AR SiO 2
p+ InP
Xj
n- InP Multiplication
n InP Charge
Grading Layer
n InGaAs
n- InGaAs Absorption
n- InP Buffer
n+ InP Substrate
Xd
tmesa
tInGaAs
tBuffer
WOCC-2005

Resonant-Cavity InGaAs/InAlAS SACM APD
• Resonant-Cavity Structure
• High QE ~ 75%
• Mesa Isolated
• SACM Configuration
• Thin InAlAs Multiplication
Region (200 nm)
• Lower Noise k ~ 0.18
• Bandwidth>20 GHz
• High Gain-Bandwidth
Product
Probe Metal
hυ
Dielectric DBR
Metal Ring
Contact
InGaAs Cap Ring Contact
p+ InAlAs
50 nm InAlAs Spacer
60 nm InGaAs Abs. Layer
50 nm InAlAs Spacer
Polyimide
APD Active Region
n+ InAlAs/InGaAs DBR
n+ InP Buffer Layer
Semi-Insulating InP Substrate
WOCC-2005
150 nm p-InAlAs Charge
200 nm InAlAs Multiplication
n+ InAlAs

Wafer-Fused SHIP APD
• Silicon Heterointerface
Photodetector (SHIP)
• Wafer-Fused Si
Multiplication Region
Au/Zn Contact
PMGI
• Mesa Isolated (20-30 µm)
• Backside Illumination
• Bandwidth= 13 GHz
• GainxBandwidth= 315
GHz
• Reliability Issue
n-type Si Substrate
p-type Implant
p+ InGaAs
n- InGaAs
Bonding
Interface
WOCC-2005

Buried Mesa APD with Regrown Guard-Ring
• Mesa Etch and Regrowth
Isolation Layer (Patented)
• No Diffused Junctions and
Multiple Implanted GRs
• Regrowth p-InP Guard Ring
+ Implanted Guard Ring
• Bandwidth< 4GHz for OC-48
Applications (2.5 GHz)
• GB Product=37 GHz
• Sensitivity= -33 dBm
• Excess Noise Factor=0.4
Regrown
p-InP
P+-InP
n-InP Mulutplication
InGaAsP
i-InGaAs
n-InP
Proton
Implant
Isolation
WOCC-2005

Planar InGaAlAs/InAlAs MQW APD
• SI InP Substrate
• Inverted Mesa Junction
• Ti Implanted Guard-Ring to
Decrease p-concentration of
Field-Buffer Layer
• Dark Current Increase Due to
Implantation
• SiN X Passivation
• p+ Zn Diffusion Isolation
• Contact Metal Deposition
• Flip-Chip Bonding
• Cd=0.15pF, Cp=0.06pF
• RL=25 Ω to achieve
Bandwidth=15.2GHz
• Id=0.36µA@ M=10
• GB Product = 120GHz
AR Coating
SI-InP Substrate
Zn Diffused
Region
Sn Bump
p-contact
Ti Implanted Guard-Ring
n+ InAlAs Cap
p+ InP
P - InGaAs
p+ InP
Field Buffer
InGaAlAs/
InAlAs
Superlattice
WOCC-2005

Waveguide APD
• Multimode Waveguide Structure
• Mesa Etch and SiNx Passivation
• InAlAs/InAlGaAs MWQ
Multiplication Layer ~0.25 µm
20 µm
6 µm
p-Metal
• InGaAs Abs. Layer ~ 0.3 µm
• Top and Bottom InAlGaAs
Cladding Layer ~ 0.8 µm
• Bandwidth= 20 GHz
n-Metal
p+ InAlGaAs
InAlGaAs
InAlAs/InAlGaAs MQW
SiNx
• GB Product= 160 GHz
n+ InAlGaAs
• Large Dark Current
• 1 µA @ 90% V B
InP Substrate
• Edge Coupled w/ Lensed Fiber (3
µm Spot Size)
WOCC-2005

Real-World APD Device Specifications
• Quantum Efficiency, Responsivity
• Gain characteristics
• Bandwidth @ M=10,12 when P IN is low (Sensitivity)
• Bandwidth @ M< 4 when P IN is high (Overload)
• Primary Dark Current
• Excess Noise Factor
• Capacitance
• Breakdown 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 Bandwidth
• InGaAs, InP layer thickness
• Device geometry
• Trade-off 3: BW@ M~10 ~ BW@ M~3
• Multiplication layer doping
• Diffusion junction depth control (Ehet control)
• Trade-off 4: Breakdown Voltage ~ Thickness, Doping
• InGaAs, InP layer thickness
• Multiplication layer doping
WOCC-2005

APD Design- Balance between Trade-offs
10
APD Bandwidth vs. Gain
3 dB Bandwidth (GHz)
1
1 10 100
Gain
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
1000
Failure Rate vs. Ea
P ro jected F ailu re R ate,
FIT
100
10
1
0.1
MOCVD APD
0.4 0.5 0.6 0.7 0.8 0.9 1
Activation Energy, eV
With >5000 hrs
accelerated aging test,
activation energy is
extracted.
With the estimated Ea of 0.96 eV, these devices have very small FIT (< 1 FIT).
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 Advantages
• MSA 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

0.5 86
0.4 86
0.3 86
0.2 86
0.1 86
0.08 6
MSA APD Receivers
Eye
BER
TriQuint R195A BER vs. Temperature @ 9.95Gb/s
10 -4
T= 0 C
T= 25 C
10 -6
T= 50 C
-26 dBm, M=10 9.953 Gb/s, 1550 nm, 2E31 – 1 PRBS
BER
10 -8
T= 70 C
-10
10
10 -12
< 1.0 dB Penalty
from 25C to 70C
-32 -30 -28 -26 -24 -22 -20
Power (dBm)
-3 dBm, M=3
WOCC-2005

0.5 8 6
0.4 8 6
0.3 8 6
0.2 8 6
0.1 8 6
0.08 6
10G APD Receiver OSNR Performance
Tx
9.95328 Gb/s
Attn.
M
EDFA
OSA
BPF
Attn.
M
BERT
LM
(Vth Adjust)
R195A
Rx
R195A BER at 18dBm OSNR (Vth optimized)
BER
10 -4
10 -6
10 -8
unit 1, opt. -20dBm
unit 2, opt. -20dBm
unit 3, opt. -20dBm
unit 4, opt. -20dBm
unit 5, opt. -20dBm
10 -10
10 -12
-22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0
Power (dBm)
WOCC-2005

0.586
0.486
0.386
0.286
0.186
0.08 6
BER vs. Vpd over Temperature
10 -4
TriQuint R195A BER vs. Vapd, 9.95Gb/s, T=0, 25, 50, 70 O C
10 -6
BER
10 -8
T= 0 C
-10
10
10 -12
T= 25 C
T= 50 C
T= 70 C
20 21 22 23 24 25 26 27 28 29 30 31 32
Vapd (V)
* For each temperature the optical power was adjusted to obtain a BER in
the range of 4e-11 to 9e-11.
WOCC-2005

Next Generation MSA Receiver & ROSA
Eye
BER
10 -4
10 -6
-28 dBm, M=9 9.953 Gb/s, 1550 nm, 2E31 – 1 PRBS
BER
10 -8
-10
10
10 -12
-32 -30 -28 -26 -24 -22 -20
Power (dBm)
+1 dBm, M=3
WOCC-2005

Fiber Transmission Experiments
0 km
100 km
(a)
(b)
Eye diagrams back-to-back, and after 100 km transmission. (a) Optical. (b) Electrical.
7/4/2005 32
WOCC-2005

Path Penalty after 100 km Fiber
Receiver Sensitivity vs. APD Vpd (B/B, 100Km)
Receiver Sensitivty (dBm)
-24
-24.5
-25
-25.5
-26
-26.5
-27
-27.5
-28
-28.5
-29
-29.5
-30
B2B
100Km
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)
2.4
2.2
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Path Penalty 100km Fiber
(dB)
7/4/2005 33
WOCC-2005

PIN & APD ROSAs
• Low cost, high performance
• XMD compatible
• 3.3V TIA
• Detector on carrier
APD flip-chip
On carrier
TIA
WOCC-2005

Advancement in Access
Speed
(bit/s)
1G
100M
10M
1M
100k
LAN(SS)
GbE-MC
100M-Ether
MC
10M-Ether
MC
Commercial
product
π
STM
PON
155M
B-
PON
final final
ADSL
622M
B-
PON
G/GE-PON
IEEE802.3
Under development
PON 系
FSAN
FSAN,ITU-T
FSAN
WDM-PON
Under research
※G-PON:Gigabit-PON(FSAN)
GE-PON:GigaEthernet-PON(IEEE802.3)
1998
2000 2001
2003
WOCC-2005

FTTP Architecture
Circuit/Packet
Switch
1550 nm broadcast
Optical
Network
Terminal
(ONT)
Residential
1490nm data
Splitter
ONT
Ethernet
Optical Line
Terminal (OLT)
1310 nm data
N x POTS
Med-Small
Office
Central
Office
ONT
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.
WOCC-2005

FTTP Market
Market: North America: 1-2M home for 2005
Verizon: About 150k Subscribers, 1M home passed. Plan to add 2M home by 2005
SBC: Field trial on 2004, and plan add 300K home on 2005
Japan: 2-3M homes for 2005
NTT: Plan spend $48B for 30M subscribers by 2010, add 1-2M subscribers on 2005
Yahoo BB: Strong competitor with 2M subscribers in 2005 plan
Korea: Plan to add 10M subscribers by 2007, but no detail plan yet
China: Still on earlier stage of deployment, a lot of trials
Europe: 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 transmission
• APD for receiving
• Cost, cost and cost while not sacrificing performance!
1310nm FP, DFB or
1490nm DFB
1.25G APD or PIN
WOCC-2005

EPON & GPON Requirements
• EPON & GPON Different Requirements
• PIN mostly in ONT side
• APD mostly used in OLT side
• APD will be more common due to split ratio increases
EPON
GPON
(IEEE 803.2ah)
(ITU-T)
1000BASE-PX10 1000BASE-PX20 G.984.2
Distance 10 Km 10 Km 20 Km
Attn Range
5-20dB
@ upstream
5-20dB
@ upstream
Class A: 5-20dB
Class B: 10-25dB
Class C: 15-30dB
Output
Power
ONT: -1 ~ +4 dBm
OLT: -3 ~ +2 dBm
ONT: -1 ~ +4 dBm
OLT: +2 ~ +7 dBm
ONT: -2 ~ +3 dBm @ ClassB
OLT: +1 ~ +6 dBm @ ClassB
Receive
Power
ONT: -24 ~ -3 dBm
OLT: -24 ~ +1 dBm
ONT: -24 ~ -3 dBm
OLT: -27 ~ -6 dBm
ONT: -25 ~ -4 dBm @ ClassB
OLT: -28 ~ -7 dBm @ ClassB
WOCC-2005