Martino Ruppi – KM3NeT 16 – 18 April 2007 - Pylos
Clock distribution and absolute time calibration in NEMO phase 1
Martino Ruppi
INFN di Bari
Martino Ruppi – KM3NeT 16 – 18 April 2007 - Pylos
Outlook
• NEMO phase 1 mini-tower
• Clock Requirements
• Clock Shore Station implementation
• Time data flow
• The console
Martino Ruppi – KM3NeT 16 – 18 April 2007 - Pylos
NEMO phase 1 mini-towerFCM
• Symmetric systems offshore and onshore
• Dense Wavelength Division Multiplexing (DWDM) based on passive Add&Drop
• Synchronous Protocol FCM onshore offshore
• Recovery clock offshore from data flow
OM• Front End (FE) and time-
stamping in OM• Analog signal sampled at
fixed rate (200 MHz)• Data recording triggered
when signal exceeds a remotely-set threshold
• The clock recovered by FCM is sent to OM
• Synchronous Protocol FCM OM
800 Mbps Synchronous
protocol Junction Box
DWDMAdd&Drop
Optical Module(OM & FE)
Synchronousprotocol
Floor Control Module (FCM)
220 m
100 m
40 m
Martino Ruppi – KM3NeT 16 – 18 April 2007 - Pylos
Clock RequirementsTime counting in OMs is based on clock recovered in FCM
Each onshore FCM has to be synchronized by a low-jitter common clock
We need to compare the OM time flow with UTC
Onshore clock has to be extracted from GPS clock and time information
has to be sent to the apparatus
System scaling to KM3 size
The clock produced has to guarantee a very high fan-out
Martino Ruppi – KM3NeT 16 – 18 April 2007 - Pylos
Clock Shore Station
• TDC 25ps sensitive • GPS receiver (+/-30 ns RMS)• GPS Antenna (now on the roof ot the onshore
station)• PC control• Modular PXI Crate FPGA board National Instr.
• Recovery clock from GPS receiver• Clock Fan-out toward FCMs onshore• Data and time recovery by IRIG B format • UTC data flow sent to FCMs onshore in
synchronous protocol• Go-and-Back time measurements with each
pair of onshore/offshore FCM by TDC• Network Time Protocol (NTP) server
synchronization of PCs by ethernet
GPSReceiver
TDC Connecting Board
Ck 10MHzIRIG B
4 X LVDS Ck 4MHz
4 X LVDS Time Data 4Mbit/s
FPGAStopx
Startx
RS232GPS Antenna
SCSI
PC
NTP
Martino Ruppi – KM3NeT 16 – 18 April 2007 - Pylos
Data flow protocol to FCM
• 8b/10b code (reveling error, scrambling 0/1, byte function embedded)
• Time upgraded each 125 s • Data (and Slow-Control) absolute time• Acoustic data absolute time• Room to accomodate more information or commands
sec.
500 bit = 1/8000 seconds
min hous days frames since 01/01/2006start Idle … stopsec since 01/01/2006 Idle IdleIdle Idle
Data absolute time Acoustic absolute timeUTC
Martino Ruppi – KM3NeT 16 – 18 April 2007 - Pylos
The Console (1)
LabView enviroment • FPGA Xilinx programming
• PC interface
• Instrument remote control
• Information storage in DB
• Logging
• Check alarms
• Accessible for control through ethernet
Martino Ruppi – KM3NeT 16 – 18 April 2007 - Pylos
The Console (2)
Off shore time calibration
FPGA monitoringand management
Go and Back time measurementsTDC Management
Satellite signal GPS locking
On shore Time calibration
Martino Ruppi – KM3NeT 16 – 18 April 2007 - Pylos
Conclusions
• The system is currently working in the NEMO Phase 1 control station
• Extension for a full-size 16-floor tower is undergoing (NEMO Phase 2)
• The setup can be easily adapted to serve even a KM3-size apparatus (it only needs more modules for the PXI crate)