Data transport architecture
over fiber and/or copper
Francesco Simeone
INFN Sez. Roma
1
Detection Unit interface with the Optical Network
Tower 1
…
Tower 5
2 fibers
redundancy can be
implemented at
connector level
PJB
MEOC
2 fibers allow
100% redundancy
SJB 1
…
SJB 18
Slow control data sent to the DUs connected to the SJB as broadcast.
Data from each DU is sent to the SJB over a different fiber using a
specific color.
2
Data Transmission (1/3): Tower Backbone
•
Backbone architecture: optical daisy chain
–
–
–
–
“waterfall” scheme (1 B&W transceiver per node);
data rate 1.25 Gb/s (easily expandable up to 2.5 Gb/s);
accommodates up to 6 PMTs and 2 hydros per storey
high optical power budget allows
cheaper connectors;
– nodes are connected by backbone branches
– optical and electrical branches are separated;
– PRO: improved system reliability, lower cable
complexity, shorter manufacture time and assembly
time.
3
Data Transmission (1/3): Tower Backbone
•
Backbone architecture: optical daisy chain
–
–
–
–
“waterfall” scheme (1 B&W transceiver per node);
data rate 1.25 Gb/s (easily expandable up to 2.5 Gb/s);
accommodates up to 6 PMTs and 2 hydros per storey
high optical power budget allows
cheaper connectors;
– nodes are connected by backbone branches
– optical and electrical branches are separated;
– PRO: improved system reliability, lower cable
complexity, shorter manufacture time and assembly
time.
F20
B&W
BackBone
F19
F18
F17
F16
F15
1 Fiber
1 color per
direction
F4
F3
F2
F1
F0
4
Data Transmission (2/3): BackBone Bypass
•
Faulty nodes can be bypassed:
– use a splitter per node (10:90 ratio);
– use an active switch per node (controlled
by the independent power control
system);
– allowed by the high optical power budget
available at each hop;
– bypass optical loss: pass 1.1 dB and tap
10 dB;
– total worst case loss 11 dB (10 nodes
failure case);
– transceivers with about 15 dB power link
budget can be used (wide availability)
– Low power transceivers electronics: <1W
per floor
5
Data Transmission (3/3): the copper daisy chain
• Copper daisy chain architecture:
– stringent limitations between cable length and max
data flux;
– double daisy chain:
 one going up, lower speed, carries the clock:
the receiver recover and regenerates the clock
 one going down, carrying 1.2 Gb/s data at
~50m distance
– accommodates up to 6 PMTs and 2 hydros per
storey;
– at the DU base an electronic board transfers the flux
on optical fibre (one colour) to the optical network
– copper handling safer than fibre handling, with
copper cheaper connectors and components
– data rate on copper limited
– bypassing a faulty storey not so easy as with optical
backbone
6
Data Transmission (3/3): Tower JB Electronics
Copper
V-I
meter
Opto Tx
Opto Rx
Fiber
Odd
Back
Bone
(OBB)
Main DC
400 V
Copper
Opto Tx
Opto Rx
400V/5V
DC/DC
converter
Tower
Single
Fiber
TX/RX
DWDM
TX/RX
Fiber
Even
Back
Bone
(EBB)
Spread Spectrum
Drivers
Power Monitor & Control,
Data Mux & Demux, Floor Control
7