Componenti e circuiti ottici
Componenti e circuiti ottici -
1
Optical Communication Systems
> 1.5 dB/km
0.4 dB/km
< 0.2 dB/km
Componenti e circuiti ottici -
2
A little bit of history…
1994
Componenti e circuiti ottici -
3
A little bit of history…
1994
1999
Componenti e circuiti ottici -
4
Towards Optical Networks
Componenti e circuiti ottici -
5
Fiber Optical Telecommunications
Componenti e circuiti ottici -
6
Fiber Capacity
Componenti e circuiti ottici -
7
Trunk transmission capacity
Componenti e circuiti ottici -
8
Capacity per Optical Fiber
100 Gbit/s
TDM
2010 First system installed
?
Electronics
Polarization Mode Dispersion
WDM
Componenti e circuiti ottici -
9
100 Gbit/s field trails
(Verizon, Alcatel-Lucent)
OFC 2008
Componenti e circuiti ottici - 10
> 100 Gbit/s systems
ECOC Sep 2010
32 QAM – 2 polarization
Componenti e circuiti ottici -
11
Trunk transmission capacity
OFC Feb. 2010
10
10
Tb
it/
s
0
Tb
it/
s
2010
Componenti e circuiti ottici - 12
100 Gbit/s systems and beyond
higher channel capacity
higher spectral efficiency
new optical components required!
Rx
Tx
Componenti e circuiti ottici - 13
At the transmitter side…
100 Gbit/s optical modulators (NTT)
λ/2 plate
(0.5 dB)
pol ER > 20dB
over 7 THz
(0.3 dB)
PDM-QPSK
(OFC 2008)
Arbitrary
modulation
format
(ECOC 2010)
Componenti e circuiti ottici - 14
… within the network …
Wide-passband and low-loss characteristics
40 Ch
100Ghz spacing
< 30 pm
B = 45 GHz
IL = 3.7 dB
XT < -38 dB
Silica ∆n = 1.5%
29 x 32 mm
Ultra small athermal AWG using 2.5%-Δ waveguides
40 Ch
100Ghz spacing
IL = 3.0 dB
XT < -37 dB
Silica ∆n = 2.5%
Componenti e circuiti ottici - 15
… at the receiver side
Infinera (Sep. 2010)
x10
•polarization splitting
•polarization rotation
•demultiplexing
•coherent detection
•polarization tracking
•…
(160 photodiodes)
Everything integrated in a single optical InP chip
Componenti e circuiti ottici - 16
Not only telecom…
Componenti e circuiti ottici - 17
Silicon Photonics (Intel)
Componenti e circuiti ottici - 18
The 50 Gbit/s silicon photonic link
Tx
Rx
Componenti e circuiti ottici - 19
Optical components
Componenti e circuiti ottici - 20
Components for WDM systems
Componenti e circuiti ottici - 21
Components and Modules in DWDM sistems
… quante cose imparerete in questo corso !
Componenti e circuiti ottici - 22
Optical interleavers
(<1dB)
(> 30dB)
Componenti e circuiti ottici - 23
Optical (de)multiplexers
Componenti e circuiti ottici - 24
Optical Switching
Performance goals:
Modulation format transparency
Today’s switching
-N receivers & N transmitters
- Limited data bandwidth
Componenti e circuiti ottici - 25
Optical λ-converters
Electronically controlled λ-converters
N receivers & N transmitters
Low speed (electr. bandwidth)
No Transparency
High conversion efficiency
Optically controlled λ-converters
Active/nonlinear devices
High speed (opt. bandwidth)
Transparency
Low conversion efficiency
Componenti e circuiti ottici - 26
The need for selective filters in WDM systems
Componenti e circuiti ottici - 27
Filters requirements
Componenti e circuiti ottici - 28
Optical technologies
Componenti e circuiti ottici - 29
Technologies for optical devices
(InP, Si…)
Polymers
Componenti e circuiti ottici - 30
An example: Power splitters
Why integration ?
Silicon
0.15
+/+/- 2%
> 70
Size
# Comp.
cm
mm2
µm2
1-2
<5
> 10
µm2
> 100
Silicon coupler
(2010, Polimi)
Componenti e circuiti ottici - 31
WDM silicon photonics
16 splitters
14 splitters
8 mm
> 50 splitters
Jan. 2010
Componenti e circuiti ottici - 32
Design of integrated circuits
System
We are here
• Eye diagram
• Bit error rate
•…
Componenti e circuiti ottici - 33
The beginning of the story: optical waveguides
• Single mode regime (why? …always?)
• Low loss
• Low (high) polarization dependence
• Small bending radius
• Active control (thermo, electrooptics, …) ?
• Nonlinearities ?
TE0
TE1
Componenti e circuiti ottici - 34
Waveguide index contrast
The index contrast ∆n is the most important
parameter of a dielectric waveguide
nco
ncl
Waveguide dimensions
Fiber to waveguide coupling
Bending radius
Losses
Directional couplers gap
Birefringence, PDL
Technological processes
Material
Tolerances
Componenti e circuiti ottici - 35
High or low index contrast?
… that’s the question
Low index contrast (0.69%) is an assessed
technology but...
Few functions per chip
Interconnects leave large space unused
Restrictions on devices (ring resonators and Bragg gratings)
Large area waveguides, low nonlinearity
while high contrast....
Economics of wafer scale integration
Compact implementation of complex functions (system on a chip)
Allows certain functions not possible with low contrast
Multifunction chips
Compact nonlinear devices
Many chips per wafer = high yield
Componenti e circuiti ottici - 36
Very Large Scale Integration
Yield ∝
1
Chip Area * defects per cm2
Cost per funct. ∝
Wafer cost
# functions per chip * Yield
VLSI
VLSI == High
High yield
yield and
and low
low cost
cost per
per function
function
Componenti e circuiti ottici - 37
Optical bends
Componenti e circuiti ottici - 38
The need for high index contrast
Rmin ~ 5∆n-1.5 [µm]
Silica
PLCs
10
Silicon Nitride
High ∆ PLCs
17% Hydex
Silicon
4
1.5% 1.5mm
10000
10 3
1000
10 2
100
10
1
10
10
0
1
0.3 0.75 1.5
17
35
Rmin
0.7% 5 mm
Devices per 6” Wafer
Minimum Bending Radius [µm]
Fiber
∆n
6.0% 0.2mm
17%
40µm
40% 10 µm
200% 1.2 µm
20 µm
200
Index Contrast ∆n %
Componenti e circuiti ottici - 39
Bends, bends, bends … and resonators
Jan, 2007
Sep 2010
Componenti e circuiti ottici - 40
Our little diamond
40 µm
Polimi, 2010
Componenti e circuiti ottici - 41
Integrated Optical Technologies
Photonic
crystals
Index
contrast
Silicon (SOI)
Componenti e circuiti ottici - 42
Low index contrast: classical integrated optics
Low loss ( <0.05 dB/cm )
but
> 5cm
Componenti e circuiti ottici - 43
High contrast glasses
500 µm
Moderate loss ( 0.15-0.5 dB/cm )
2 cm
Componenti e circuiti ottici - 44
Semiconductor: very high index contrast
, Si
High loss ( >1 dB/cm )
SOI
Ghent University, 2004
Componenti e circuiti ottici - 45
Silicon Photonics: my first 10 years
IBM
2007
220
500
1.7
1
y
Ebeam
Glasgow
Univ.
2008
220
480
1 (2)
1
n/y
Ebeam
Componenti e circuiti ottici - 46
Silicon photonics: what is good…
Componenti e circuiti ottici - 47
Silicon photonics: … what is challenging
Componenti e circuiti ottici - 48
How much small is a silicon photonic device?
400 nm !
200 nm !
Red blood cell
8 um (x 20)
300 nm !
Human hair
80 um (x 200)
Componenti e circuiti ottici - 49
Photonic Crystals
PC W1 waveguide
90°Bend
Componenti e circuiti ottici - 50
Some technological issues
Packaging
Size
Performance
Pigtailing (fiber-waveguide connections)
Back Reflections (<50dB for CATV)
Temperature control
>> Electronics
Monitoring (hot topic !)
Need for feedback
Micro/Mini Sistems
Sensitivity
Integration of several active/passive
components on chip (mono/hybrid)
Polarization state
Design on tolerance (yield)
Tuning/trimming
Componenti e circuiti ottici - 51
Hybrid integration
Componenti e circuiti ottici - 52
Photonics integrated circuits: where are we going to?
Componenti e circuiti ottici - 53