1. PeterJ Slide 1 Oct 14, 2008 Transfer exact timing using a coded data communication channel

2. PeterJ Slide 2 Oct 14, 2008 2 3 -  1 Data Receiver CIP Confidential Shore StationUndersea Station OM PMTs Loop timing JB DU 1     OM PMTs KM3NeT Timing Principle Mod  One Reference Clock (GPS) Local Clocks are phase locked; thus isochronous. But their values have an offset Broadcast Individual Optical Channel Loop timing

3. PeterJ Slide 3 Oct 14, 2008 2 3 -  1 Data Receiver CIP Confidential Shore StationUndersea Station OM PMTs Loop timing JB DU Continuous Wave DWDM lasers (26 wavelengths) Timing (& comms) 1 of 100 fibers Power splitter to feed 100 Detection Units 1 of 100 fibers Reflective Modulator 1     Data Timing Tap Optical Receiver OM PMTs 500m 1500m KM3NeT Timing Principle DWDM DeMuxes DWDM Mux Mod  Directional Coupler Arrayed Waveguide Grating Modulate Timing on all ’s

4. PeterJ Slide 4 Oct 14, 2008 Start Stop Rx 8B/10B Encoded Tx 8B/10B Encoded Constant Impedance Trombone Line 0  2x10 cm = 0  700 ps Timing over 8B10B Test Setup

5. PeterJ Slide 5 Oct 14, 2008 K28.5D16.2K23.7 IDLECharExt Tx 8B/10B Encoded K28.5D16.2K28.5D16.2 IDLE K28.5D16.2K28.5D16.2 IDLE K28.5D16.2K23.7 IDLECharExt K28.5D16.2K28.5D16.2 IDLE K28.5D16.2 IDLE K28.5D16.2 IDLE Start Stop Rx 8B/10B Encoded Variable propagation delay K23.7 Timing over 8B10B

6. PeterJ Slide 6 Oct 14, 2008 +700 ps +0 ps Reset (= resynchronize) Variable Propagation Delay… What is happening???

7. PeterJ Slide 7 Oct 14, 2008 810 Closer Inspection… RxRecClk + 700 ps Reset (= resynchronize & Byte Re-Align) BitSlide(4:0) At 3.125 Gbps: Absolute timing is determined by “Start/Stop” delay (in 20 bit steps of 6.4 ns) plus BitSlide fine delay (20 steps of 320 ps) 000101011011101011000001010110111010110000010101101110101 8 700 ps

8. PeterJ Slide 8 Oct 14, 2008 0111010110000010101101110101100000101011011101011000001 19 Demo: “On the edge”… RxRecClk 0111010110000010101101110101100000101011011101011000001 19 Reset (= resynchronize & Byte Re-Align) BitSlide(4:0) 6.4 ns 0111010110000010101101110101100000101011011101011000001 0 + 320 ps 1 0011 = 190 0000 = 0

9. PeterJ Slide 9 Oct 14, 2008 Conclusion Timing information is distributed inherent over a serial data channel and can be used Timing resolution is equal to a Unit Interval (= bit time; at 3.125 Gbps = 320 ps) Receivers in Optical Modules are all phase locked (thus isochronous) to one master clock (GPS) on shore

10. PeterJ Slide 10 Oct 14, 2008 For the skeptic… Does this work from board to board? Transmitter Lattice LFSCM25 Receiver Xilinx Virtex-5 3.125 Gbps via Constant Impedance Trombone Line Transmitter Crystal Oscillator Receiver locked to Transmitter Oscillator Yes it does! Fine time (320 ps Steps) Coarse time (6.4 ns Steps)

11. PeterJ Slide 11 Oct 14, 2008