1. Point-to-point connection between each DOM and the shore station
Photonic Readout and DAQ system
E. Heine , M. van der Hoek, J. Hogenbirk, , P. Jansweijer, M. de Jong, G. Kieft, P. Kooijman, S. Mos, H. Peek, J.W. Schmelling, P. Timmer , E. de Wolf (Nikhef, Amsterdam, the Netherlands), H. Löhner (KVI, Groningen, the Netherlands)
on behalf of the KM3NeT Consortium
12,800 digital optical modules (DOMs),
31 3-inch PMTs per DOM
Shore station at 100 km distance
Point-to-point connection between each DOM and the shore station D
wavelength
CW laser
array
Clock/Data
gen.
Clock-Data
modulation
POPT
time
i=1
i=M λ1 λM
Pout,i = A(λi)*Pin(λi)
Reduced
optical power
Pout = Pin / N
detect
Reflective
modulator
DOM electronics
Serialized PMT
data
DOM #1
Data
All DU data
P(t) per λ
Wavelength mux
Wavelength demux
Shore station electronics
Optical
amplifier
Power splitter
to different DUs
100 km
< 2km
Shore station
Prim. Junction Box
DU’s
Gated
Seabed
DOM
# M A Y X
Mirror 1 A’
TY→X
Sec. Junction Box
3 km
looptime
signaling
to electronics
Wavelength
Demux
in sets of
M channels
TA → DOM#i → A’
Norm
Cal.
TA’ → DOM #i → A’
TX→Y
i=1…M
i=(3M+1)…4M
per DU
Channels 1…M
Looptime M Z
TX→Y = TY→X
TA’ → DOM#i → A’
TDOM#i → A’/2
TA → DOM#i → A’
For illustration (measured only during construction)
Pulse echo A’ to all DOMs #i--M and Z
Clock/framing round trip measured
TA → DOM#i = TA → DOM#i → A’ – TDOM#i → A’
* Slow control not shown
wavelength
POPT
visualizer
Data stream
Overview Timing measurement *
Optical I/O port in DOM
Bit Error Rate (BER) test results
at a bit rate of 1.25 Gbps
Timing circuit
Conclusions
Signal amplification adapted to transmission over 100 km cable to shore. Reflected R-EAM modulated signal of -10 dBm
with an extinction ratio of r = 7 fits in the return path of the network.