[time-nuts] Opera coordinator has resigned

Achim Vollhardt avollhar at physik.uzh.ch
Sat Mar 31 19:24:39 UTC 2012


Dear John and all,

I do work in high energy physics and we use LEMO and other standards. 
For some years now, I have started to advertise against LEMO (in 
particular the LEMO 00 size), as it is VERY sensitive to mechanical 
defects and partial connection (yes, you can ..). We have found very 
often defective LEMO connections, which could only be detected via time 
domain reflectometry. Or LEMO interfaces, which changed impedance 
significantly when rotating them in the fully mated position.. this list 
could be extended a lot more. And this famous click when mating is 
inaudible in typical high energy physics electronics barracks.. too much 
fan noise.

In addition, for the very fast signals of modern DAQ systems, LEMO 00 is 
just not up to speed (literally) anymore. If size is not of ultimate 
importance, we switched to SMA, or SMC if size matters.

About this dreadful OPERA fiber connector:

It very much looks like a FC connector. It has a polarisation nut and I 
have to confess having misconnected them more than once myself.
It might have been beneficial to shorten in this standard the thread 
length so there is no possibility to engage the thread (not even 
partially) when not properly aligned. As the thread is indeed fairly 
long, you can do what seemed to have happened in OPERA.


I acknowledge the importance of QA, but also some design-inherent 
features like low power indications should be in place to prevent these 
things from happening.

Regards,
Achim



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