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Bandwidth of Micro Twisted-Pair Cables and Spliced SIMM/GRIN Fibers and Radiation Hardness of PIN/VCSEL Arrays

Bandwidth of Micro Twisted-Pair Cables and Spliced SIMM/GRIN Fibers and Radiation Hardness of PIN/VCSEL Arrays. Richard Kass The Ohio State University. 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

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Bandwidth of Micro Twisted-Pair Cables and Spliced SIMM/GRIN Fibers and Radiation Hardness of PIN/VCSEL Arrays

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  1. Bandwidth of Micro Twisted-Pair Cables and Spliced SIMM/GRIN Fibers and Radiation Hardness of PIN/VCSEL Arrays Richard Kass The Ohio State University 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 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. ~1.85m The Current ATLAS Pixel Detector ATLAS is a detector at CERN designed to study 14 TeV pp collisions Detector upgrade planned for Super-LHC in 2015 Pixel Detector: ATLAS’s Inner most charged particle tracker Measures (x,y,z) to ~30 mm Pixel detector is based on silicon Pixel size 50mm by 400 mm ~100 million pixels Radiation hardness is an issue must last ~ 10 years 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 ~108 channels

  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 a Simplify opto-board and FE module production a Sensitive optical components see lower radiation level than modules a PIN/VCSEL arrays allow use of robust ribbon fiber ~150m ~1m optoboard VCSEL:Vertical Cavity Surface Emitting Laser diode VDC:VCSEL Driver Circuit PIN:PiNdiode DORIC:Digital Optical Receiver Integrated Circuit optoboard holds VCSELs, VDCs, PINS

  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 ~1m optoboard

  5. Bandwidth of Micro Twisted Pairs • Bandwidth of 3 micro twisted-pair wires were compared. • Wire used is MWS Wire Industries Twistite • 38 AWG (25mm insulation, 100um wire, 150mm 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. 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)

  6. Bandwidth of Micro Twisted Pairs Bandwidth of 3 micro twisted-pair wires were compared: 38 AWG/100 mm, 2 turns/cm (current pixel cable) 36 AWG/127 mm, 2 turns/cm 36 AWG/127 mm, 4 turns/cm 2 T/cm 2 T/cm 4 T/cm The Current pixel cable is the best!

  7. Micro Twisted Pair Eye Diagrams 60 cm pixel cable 140 cm pixel cable 650 Mb/s Transmission at 650 Mb/s is adequate 1.3Gb/s Transmission at 1.3 Gb/s may be acceptable

  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 ? Bandwidth Test Setup for existing Pixel Architecture splices made using Fujikura fusion splicer

  9. Bandwidth of Fusion Spliced Fiber 8 + 80 m spliced SIMM/GRIN fiber 1 m GRIN fiber 2 Gb/s Transmission up to 2 Gb/s looks adequate

  10. Radiation Level at SuperLHC Optical link of current pixel detector is mounted on patch panel: amuch reduced radiation level compared to collision point: SI (PIN) @ SLHC: n2.5 x 1015 1-MeV neq/cm2 n4.3 x 1015 p/cm2 or 114 Mrad for 24 GeV protons GaAs (VCSEL) @ SLHC: n14 x 1015 1-MeV neq/cm2 n2.7 x 1015 p/cm2 or 71 Mrad for 24 GeV protons

  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 mm process operating voltage is 1.2 V thick oxide option can operate at 2.5 V aVCSEL 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. Opto-board clock PIN DORIC data VDC VCSEL VCSEL VDC Real Time Monitoring in T7 Beam Test Compare transmitted and decoded data measure minimum PIN current for no bit errors Measure optical power Real time testing of opto-board system using loop-back setup Signal routed back to opto-baord via test board attached to 80-pin connector & test board 25m optical fiber cable bi-phase marked optical signal decoded data decoded clock In beam In control room Bit error test setup at CERN’sT-7 beamline 24 GeV protons Two VCSEL arrays from same vendor per opto-board

  13. Results: PIN Responsivity PINS are manufactured by TRUELIGHT Responsivity (mA/mW) Count channel number Responsivity (mA/mW) Responsivity of PINs decrease by ~50% after SLHC dosage

  14. Voltage (V) Voltage (V) power (mW) power (mW) Optowell AOC current (mA) current (mA) Voltage (V) Voltage (V) power (mW) power (mW) ULM 10Gb/s ULM 5Gb/s current (mA) current (mA) VCSEL LIV Characteristics Pre-irradiation ULM requires higher voltage to operate All arrays have very good optical power

  15. VCSEL Power vs Dosage SLHC Optowell survives to SLHC dosage Other VCSELs might survive with more annealing or slower irradiation

  16. Summary JMicro twisted-pair cable of current ATLAS pixel detector can be used for transmission up to 1 Gb/s JFusion spliced SIMM/GRIN fiber can transmit up to 2 Gb/s JPIN responsivity decreases by 50% after SLHC dosage JOptowell VCSEL survives SLHC dosage JCurrent opto-link architecture satisfies SLHC requirements

  17. extra slides

  18. Setup for Irradiation in Shuttle at CERN 25 meter optical fiber Rad hard optical fibers Opto-boards CERN T7 Remotely moves in/out of beam CERN T7

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