Two-dimensional fiber array Two-dimensional fiber array with integrated topologywith integrated topologyfor short-distance optical interconnectionsfor short-distance optical interconnections
Makoto Naruse1),2), Alvaro Cassinelli3), and Masatoshi Ishikawa3)
1: Ultrafast Photonic Network GroupCommunications Research Laboratory , Japan
E-mail: [email protected]
2: Japan Science and Technology Corporation (JST), PRESTO
3: Dept. Information Physics and Computing, University of Tokyo
Contents
1. Interconnection fabric
2. Wave-guide-base, direct implementation of interconnection topology
3. Interconnection decomposition
4. Experimental fabrication
5. Summary and future plans
Optical Interconnection fabric / switching fabric
LSILSI
LSILSI
LSI
LSILSI
LSI
Optical Interconnection fabric / Switching fabric
Inter Chip, Inter-boardOptical interconnection
Optical interconnection
Multistage architecture
Multistage architecture
…
…
All optical
Optoelectronic
An example: Omega network
Inp
ut
Ou
tpu
t
OE
Computation
EO Optical interconnect
Optical interconnect
w/o OEO
Regularly interconnected multistage architecture
Wave-guide-base, direct implementation of interconnection topology
…
…
OE
Computation
EO Optical interconnect
Optical interconnect
w/o OEO
• Two-dimensional fiber array
Configure the interconnection topology directly by positioning the input and output end of the wave-guides
Input
Output
All optical
Optoelectronic
Design considerations
• Two-dimensional (2D) parallelism • Focus on Permutation network (such as perfect shuffle)• Scalability• Module reusability (Permutation reusability)
• Alignment difficulty: Both input and output end• Theoretically more volume efficient than free-space equivalent
Other remarks
Out of scope of this paper
Y.Li, et. al., “Volume-consumption comparisons of free-space and guided-wave optical interconnections”, Appl.Opt. 39 (2000), 1815
Example1: Omega networkIn
pu
t
Ou
tpu
t
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
• Messy topology
• Poor scalability
• Poor reusability
Permutation=Perfect shuffle
2D direct implementation
Example 2:Indirect Binary n-Cube Network
Permutation=Butterfly and perfect shuffle
Several kinds of different interconnection topology are used
Interesting fact
Perfect shuffle and butterfly permutation can be made out of the following three types of elemental permutations: Row, Column, and Diagonal permutations
Column permutationRow permutation Diagonal permutation
Before decomposition
Direct implementation
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0123456789
101112131415
Node assignment:Scan mapping
Perfect shuffle
Interconnection decomposition
Row permutation
Column permutation
Diagonal permutationDecompose
0123456789
101112131415 1
2
6
14
0123456789
101112131415
Perfect shuffle
Interconnection decomposition
Column permutation
Column permutation
Diagonal permutation
0123456789
101112131415
Decompose
3
10
10
3
0123456789
101112131415
Butterfly
shuffle shuffle shuffleshuffle
Processor arrays
(exchange switches and more)
Row permutation
90º
Overall Omega Network
Column permutation
Diagonal permutation
(2) (3) (4) -1(4)
Processor arrays
(exchange switches and more)
Row permutation
90º
Column permutation
Diagonal permutation
Overall Indirect Binary n-Cube Network
Two holder prototypes: Zirconium, SiO2
Pitch: 250±5 m
Multimode graded index fibers: NA=0.21(core 50m, cladding 126m)
Transmission loss: 3dB/km
Length: 30 cm
Prototype fiber module: Preliminary 4x4 array
3 mm
2 mm
5 mm
Embedded interconnection topology
Pitch uniformity
0
2
4
6
8
10
12
14
16
244 246 248 250 252 254 256
Zirconium
Pitch (m)
Num
ber
of li
nk
245m-255mAve. 250mStd deviation 2.0m
246m-254mAve. 250mStd deviation 1.5m
SiO2
Pitch(250m)
Input Output (CCD image)
No relay optics
Interconnection example
VCSEL arrayFiber module input
Input
Output
x 50 m
0
0.05
0.1
0.15
0.2
0.25
-105 -90 -75 -60 -45 -30 -15 0 15 30 45 60 75
X (microns)
Exi
t p
ow
er (
a.u
)
x
Alignment tolerances(half peak power)
y 70 m
Transmission efficiency / Alignment tolerance
Transmission efficiency
Max. transmittance 38.45%
0
5
10
15
20
25
30
35
40
45
6 7 8 9 10 11 12 13
VCSEL driving current (mA)
Tra
nsm
itta
nce
(%
)
38.45
9.5
LED regime
LASER regime
Summary and future plans
• Wave-guide-base, direct implementation of 2D parallel interconnection topology
• Interconnection decomposition for scalability and reusability
• 2D fiber array with interconnection topology was demonstrated
Future plan: • Theoretical foundation for interconnection
decomposition and total system design• Higher-density 2D interconnect• System demonstration