Thanks Jonas
Indeed it would be better.
But with a HP cable, because the QSFP+ port compatibility on HP Switch is even more risky to me .
With Juniper sfp+ on SRX.
Unfortunately such splitter does not exist, I've check on HP site
http://www8.hp.com/fr/fr/products/networking-switches/product-detail.html?oid=5354511#!tab=oas
I haven't checked on Juniper site but as I said we' would move the potential issue on HP QSFP+ side, I won't have a confirmation it will work for sure.