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L1 MUON BARREL VCSEL’s OPTICAL LINK

L1 MUON BARREL VCSEL’s OPTICAL LINK. Developed by ATLAS Napoli’s Group 500 links from on detector L1 muon barrel trigger to USA15 Unidirectional link on multimode fibre driven by 850 nm VCSEL Based on G-Link HDMP-1022/4 and HDMP-1032°/4° chipset

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L1 MUON BARREL VCSEL’s OPTICAL LINK

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  1. L1 MUON BARREL VCSEL’s OPTICAL LINK Developedby ATLAS Napoli’s Group 500 linksfrom on detector L1 muonbarrel trigger to USA15 Unidirectional link on multimode fibre drivenby 850 nm VCSEL Based on G-Link HDMP-1022/4 and HDMP-1032°/4° chipset UseofAgilent (nowAvago) HFBR-5912 opticaltransceiver 40.078 MHz clock, 800 Mbit/sec serial stream on fiber

  2. L1 MUON BARREL VCSEL FAILURE Westarted “discovering” VCSEL failures at the beginingof 2009 Up tpnowwefound 23 brokenlinks Failure rate was a bit higherthenone per month, and decreased a littleafter the decisiontaken in 2010 toswitch off the link whennot in use In allbrokenlinkssameproblem: no output light in the transmitter 12 brokenlinkspeggyboardswererepalcedwithspareones. On other 8 linkswehavereplaced the VCSEL (simple but delicate operation). Remaining 3 linksnotyetrepaired. - Wehave sent 3 broken VCSEL partsto AVAGO forinvestigation

  3. AVAGO INVESTIGATION RESULTS -Mostlikely the brakingis due toelectro-staticdischarges Most probably the damage had happened during the production in the “assembly/test processes” From 2005 on the company has constantly improved the production line At the end of 2009 a zener diode was introduced to improve the protection of HFBR-5912E against discharges up to a factor 20 Our lasers were produced in 2003 and 2004; this means that the lasers are sensible to ESD’s - In 2009 and 2010 we have replaced our broken lasers with some spare parts bought in the past and produced in 2007 (mid way between 2004 and 2009)

  4. L1 MUON BARREL LINK NEXT ACTIONS Napoli's group (A. Aloisio and V. Izzo) have measured the optical  spectrum of all HFBR- 5912E used in the apparatus. The measure was taken at the end of the fiber. The results of measurements and the preliminary conclusions are illustrated in the next slides In the meantime INFN has financed 50 new VCSEL’s to be bought from 2010 AVAGO production (the upgraded one) Exchanging a link means exchanging a PAD box. This is a boring job, although it is not too much difficult (only few PAD’s are in a very difficult access position ) In addition INFN has also financed in a conditional way (“sub-judice”) 150 extra VCSEL’s, in case this will be really necessary.

  5. the largest majority have “regular” spectra centered around 850 nm (typical variation between 846 nm and 854 nm), max value -20 dbm and width (at – 50 dbm) between 1.5 and 2 nm

  6. “fringed” spectra, more irregular respect to the previous ones. Max value -20dbm, centered at a lowest value (between 842 nm and 844 nm) and width (at – 50 dbm) a little higher

  7. “narrow” spectra similar to Liquid Argon broken links. More than 15% of the total. It is not clear if they have problems. The LAr links were cut off from one side; here, with some approximation, we could say that some of them are cut off. But, with some optimism, we could consider these spectra similar to those of category 1), regardless their 1 ns width at – 50dm

  8. PRELIMINARY CONCLUSIONS In the literature apparently doesn’t exist any link between spectra of optical power and damage from ESD; and since we don’t have more information, the only reasonable thing to do is to wait for some breakings and to consult the database to verify wich kind of spectra had the broken links. We could also repeat the measurements in 6 or 12 months from now to verify if it exists some sort of “evolution “of spectra.

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