1. IEEE06/San Diego R. Kass N18-5 1 Bandwidth of Micro Twisted-Pair Cables and Spliced SIMM/GRIN Fibers and Radiation Hardness of PIN/VCSEL Arrays W. Fernando, K.K. Gan, A. Law, H.P. Kagan, R.D. Kass, S. Smith The Ohio State University M.R.M. Lebbai, P.L. Skubic University of Oklahoma Richard Kass The Ohio State University OUTLINE Introduction-ATLAS/Pixel Detector/SuperLHC Bandwidth of micro twisted-pair cables Bandwidth of fusion spliced SIMM-GRIN fibers Radiation hardness of PIN/VCSEL arrays Summary

2. IEEE06/San Diego R. Kass N18-5 2 The Current ATLAS Pixel Detector A pixel module contains: 1 sensor (2x6cm) ~40000 pixels 16 front end (FE) chips 2x8 array Flex-hybrid 1 module control chip (MCC) There are ~1700 modules ~10 8 channels ~1.85m Pixel Detector: ATLAS’s Inner most charged particle tracker Measures (x,y,z) to ~30  m Pixel detector is based on silicon Pixel size 50  m by 400  m ~100 million pixels Radiation hardness is an issue must last ~ 10 years ATLAS is a detector at CERN designed to study 14 TeV pp collisions Detector upgrade planned for Super-LHC in 2015

3. IEEE06/San Diego R. Kass N18-5 3 Present Pixel Opto-link Architecture Current optical link of pixel detector transmits signals at 80 Mb/s Opto-link separated from FE modules by ~1m transmit control & data signals (LVDS) to/from modules on micro twisted pairs Use PIN/VCSEL arrays Use 8 m of rad-hard/low-bandwidth SIMM fiber fusion spliced to 70 m rad-tolerant/medium-bandwidth GRIN fiber  Simplify opto-board and FE module production  Sensitive optical components see lower radiation level than modules  PIN/VCSEL arrays allow use of robust ribbon fiber VCSEL: Vertical Cavity Surface Emitting Laser diode VDC: VCSEL Driver Circuit PIN: PiN diode DORIC: Digital Optical Receiver Integrated Circuit optoboard holds VCSELs, VDCs, PINS ~150m optoboard ~1m

4. IEEE06/San Diego R. Kass N18-5 4 R&D Issues for Super-LHC A Bandwidth of ~ 640 Mb/s is needed Can micro twisted pair transmit at this speed? Can fusion spliced SIMM/GRIN fiber transmit at this speed? Radiation Hardness of opto-board components Can PIN/VCSEL arrays survive SLHC radiation dosage? ~150m optoboard ~1m

5. IEEE06/San Diego R. Kass N18-5 5 Bandwidth of Micro Twisted Pairs Bandwidth measurements made with LeCroy Wavemaster 8600A digital scope (6 GHz input bandwidth, and 7.5GHz differential probe) Eye diagrams made using pseudo-random data (650Mb/s, 1 Gb/s) Eye masks adapted from Gigabit Ethernet Spec. (IEEE std. 802.3) Bandwidth of 3 micro twisted-pair wires were compared. Wire used is MWS Wire Industries Twistite 38 AWG (25  m insulation, 100um wire, 150  m OD) (current pixel cable) 5 turns per inch, with 75Ω termination. 36 AWG (9um insulation, 127um wire,145um OD) 10 turns per inch, with 100Ω termination. 5 turns per inch, with 75Ω termination.

6. IEEE06/San Diego R. Kass N18-5 6 Bandwidth of Micro Twisted Pairs Bandwidth of 3 micro twisted-pair wires were compared: 38 AWG/100  m, 2 turns/cm (current pixel cable) 36 AWG/127  m, 2 turns/cm 36 AWG/127  m, 4 turns/cm The Current pixel cable is the best! 2 T/cm 4 T/cm

7. IEEE06/San Diego R. Kass N18-5 7 Micro Twisted Pair Eye Diagrams 140 cm pixel cable 60 cm pixel cable Transmission at 650 Mb/s is adequate 650 Mb/s 1.3Gb/s Transmission at 1.3 Gb/s may be acceptable

8. IEEE06/San Diego R. Kass N18-5 8 Bandwidth of Fusion Spliced Fiber GRIN: Graded Index multi mode optical fiber GRIN fibers are rad-tolerant with medium bandwidth SIMM: Single Index MultiMode optical fiber SIMM fibers are rad-hard but lower bandwidth Present system designed to work at 80Mb/s but will it work at1Gb/s ? splices made using Fujikura fusion splicer Bandwidth Test Setup for existing Pixel Architecture

9. IEEE06/San Diego R. Kass N18-5 9 Bandwidth of Fusion Spliced Fiber 8 + 80 m spliced SIMM/GRIN fiber 1 m GRIN fiber Transmission up to 2 Gb/s looks adequate 2 Gb/s

10. IEEE06/San Diego R. Kass N18-5 10 Radiation Level at SuperLHC Optical link of current pixel detector is mounted on patch panel:  much reduced radiation level compared to collision point: SI (PIN) @ SLHC: n 2.5 x 10 15 1-MeV n eq /cm 2 n 4.3 x 10 15 p/cm 2 or 114 Mrad for 24 GeV protons GaAs (VCSEL) @ SLHC: n 14 x 10 15 1-MeV n eq /cm 2 n 2.7 x 10 15 p/cm 2 or 71 Mrad for 24 GeV protons

11. IEEE06/San Diego R. Kass N18-5 11 SLHC Issues for PIN/VCSEL PIN: What is responsivity after irradiation? What is rise/fall time after irradiation? VCSEL: Driver chip will most likely be fabricated with 0.13  m process operating voltage is 1.2 V thick oxide option can operate at 2.5 V  VCSEL requirement: < 2.3 V to produce 10 mA or more some VCSELs require > 2.3 V to operate at 10 mA or more What is rise/fall time after irradiation? What is optical power after irradiation? What current is needed for annealing? We irradiated 4 different kinds of VCSELs: Optowell Advanced Optical Components (AOC) ULM Photonics (5Gb/s and 10Gb/s versions)

12. IEEE06/San Diego R. Kass N18-5 12 Real Time Monitoring in T7 Beam Test Real time testing of opto-board system using loop-back setup data DORIC clock PIN VDC VCSEL Opto-board VDCVCSEL bi-phase marked optical signal decoded data decoded clock Signal routed back to opto-baord via test board attached to 80-pin connector & test board Bit error test setup at CERN’sT-7 beamline 24 GeV protons Compare transmitted and decoded data measure minimum PIN current for no bit errors Measure optical power In control room 25m optical fiber cable In beam Two VCSEL arrays from same vendor per opto-board

13. IEEE06/San Diego R. Kass N18-5 13 Results: PIN Responsivity Responsivity of PINs decrease by ~50% after SLHC dosage Responsivity (  A/  W) Count channel number Responsivity (  A/  W) PINS are manufactured by TRUELIGHT

14. IEEE06/San Diego R. Kass N18-5 14 VCSEL LIV Characteristics ULM requires higher voltage to operate All arrays have very good optical power Pre-irradiation AOC current (mA) power (  W) Voltage (V) ULM 10Gb/s current (mA) power (  W) Voltage (V) Optowell current (mA) power (  W) Voltage (V) ULM 5Gb/s current (mA) power (  W) Voltage (V)

15. IEEE06/San Diego R. Kass N18-5 15 VCSEL Power vs Dosage Optowell survives to SLHC dosage Other VCSELs might survive with more annealing or slower irradiation SLHC

16. IEEE06/San Diego R. Kass N18-5 16 Summary Micro twisted-pair cable of current ATLAS pixel detector can be used for transmission up to 1 Gb/s Fusion spliced SIMM/GRIN fiber can transmit up to 2 Gb/s PIN responsivity decreases by 50% after SLHC dosage Optowell VCSEL survives SLHC dosage Current opto-link architecture satisfies SLHC requirements

17. IEEE06/San Diego R. Kass N18-5 17 extra slides

18. IEEE06/San Diego R. Kass N18-5 18 Setup for Irradiation in Shuttle at CERN Opto-boards Rad hard optical fibers 25 meter optical fiber Remotely moves in/out of beam CERN T7