In Junos, we can use RPM (real-time performance monitoring) to monitor link quality.
1. give a name to the ping probe and test name
edit services rpm probe ping-probe test test-ping
2. set probe type
set probe-type icmp-ping
3. set probe count for each test and interval between each ping (in second)
set probe-count 10 set probe-interval 1
4. set source and target address (must be the interconnect IPs if you want to detect link quality)