Global overview of the Optical Network for KM3Net Phase 1 Sander Mos KM3NeT Collaboration Meeting 30 January 2013 Marseille

30 January 2013Sander Mos – Nikhef optical team2 Wet mateable connector Optical connectors Optical connectors are the most troublesome and unreliable parts in an optical network. Optical contact surfaces need to be very clean before connecting. Otherwise extra attenuation is introduced. Each connector exhibits some back reflection. This can cause unwanted interference. Flat surface or FC connectors have a back reflection of -30 dB (poor) to -50 dB. Angled or APC connectors have -50 dB to -60 dB back reflection. This is the most preferred type of connector. Wet mateable connectors often have unreliable attenuation characteristics. Use as less connectors in an optical path as possible! When properly done a fusion splice is the most reliable connection. Dry mateable connector FC/APC connector Fusion Splice

30 January Optical Amplifiers Optical power Optical channels Optical power Optical channels Optical power Wavelengths Optical power Wavelengths Input Output EDFA is an all optical amplifier. It consists of a length (10-50m) of Erbium doped fibre which is pumped by a pump laser. The pump laser can be 980 nm or 1480 nm. Pumping with 980 nm gives the lowest minimum noise figure. <4 dB Pumping with 1480 nm has the highest quantum efficiency, and a noise figure of <5.5 dB. To increase reliability redundant pump lasers can be used. Important for submarine applications. EDFA slow control is needed to tune the output power in case of a different optical channel load. (If less optical channels are used) The minimum required Optical Signal to Noise Ratio (OSNR) limits the maximum number of EDFA’s which can be in an optical path. Amount of amplification depends on input signal levels Amplification is wavelength dependant Sander Mos – Nikhef optical team Shaping of the input spectrum to correct for wavelength- and optical power- dependent amplification

30 January 2013Sander Mos – Nikhef optical team4 Optical Fibres and power handling Major Nonlinear Effects in long fibre lengths (>20km) Stimulated Raman Scattering (SRS) This adds an extra power penalty Stimulated Brillouin Scattering (SBS) This limits the maximum optical power per channel Self-Phase Modulation (SPM) Cross-Phase Modulation (XPM) Four Wave Mixing (FWM) All these nonlinear effects highly depend on the fibre type, channel spacing and optical power per channel. 40 Channels at 100 GHz spacing is more relaxed then 80 Channels at 50 GHz spacing SBS threshold SRS power penalty, with channels at 100 GHz spacing (without special techniques to suppress SRS, by e.g. wavelength dithering or phase modulation of the optical wave)

30 January Redundant or segmented network? Shorestation Junction Box DU Return fibres 1 Downstream fibre 1 Redundant downstream fibre Shorestation Junction Box DU Return fibres N Downstream fibres for N segments OR Segment 1 Segment N+1 Sander Mos – Nikhef optical team

30 January Redundant or segmented network? RedundantSegmented Minimum of 2 fibres needed for downstream Minimum of N fibres needed for downstream One set of EDFA’s for CW and data distribution N sets of EDFA’s for CW and data distribution One Clock and timing signalN Clock and timing signals Failure of 1 downstream optical path no loss of detector Failure of 1 downstream optical path complete segment of DU strings lost Downstream data only over few fibresDownstream data over many fibres More constraints on EDFA amplification Less constraints on EDFA amplification Nr of strings = (Available fibres – 2)*4Nr of strings = (Available fibres – N)*4 A Redundant downstream connection for the slow control and timing of the DOM uses the least amount of fibres. Sander Mos – Nikhef optical team

30 January km Shorestation C-Band nm L-Band nm DU-String DOM Redundant fibre N fibres Preliminary Design for Phase 1 with 40 / 80 Channels 16 fibres Design with redundant optical paths OFM Up to 4 DU Strings Up-Stream path To Next Node To Intermediate optical units - Wavelength interleaving. 80 Channels are split in to 4 x 20 Channels - Clock distribution - Amplification Optical Fanout Module Intermediate optical unit Per 4 DU strings one unit is needed CW Laserbank with up to 80 Channels inside the C-Band for providing light to the REAM’s One laser with modulator for Slow control / timing of all the DOM’s with a total shared data rate of 1Gbps. (Broadcast) Per DU string 20 APD receivers are needed. Distribution of 80 CW channels and Slow control/timing data Sander Mos – Nikhef optical team First Node Last Node Redundant fibre 2 fibres -One with 40-80λ CW + 1λ -One for the upstream data 16 x 14 x Max 20x DOM

30 January km MOD + Drivers 50/50 APD Lasers on/off LiNbO3 λ1-80 λ81 SMA BNC SMA C2 λ1λ1 λ1λ1 D1 λ1-80 [1,5…77] + 81 λ λ CW + 1λ C-Band nm L-Band nm 1:4 LiNbO3 D λ1λ1 λ GHz + 50GHz DWDM DU-String 1:20 DOM λ81 2:16 Solidstate Switches Redundant fibre N fibres 16x λ GHz 16 fibres Shorestation Sander Mos – Nikhef optical team Preliminary Design for Phase 1 with 40 / 80 Channels 14 x 2 x 16 x Last Node First Node Design with redundant optical paths Intermediate optical unit [2,6…78] + 81 [3,7…79] + 81 [4,8…80] + 81 [1,5…77] [2,6…78] [3,7…79] [4,8…80] Channel GHz Redundant fibre

30 January Overview Optical connectors are the most troublesome and unreliable parts in an optical network. Use as less connectors in an optical path as possible! The number of EDFA’s that can be connected in series is limited by the OSNR. A system with 40 channels is foreseen for the first stage and this will later be extended to 80 channels. Sander Mos – Nikhef optical team