ABB Relion 670 Series REL670 Commissioning Manual page 60

Section 4
Starting up
54
An IED equipped with optical connections has an minimum space
requirement of 180 mm for plastic fiber cables and 275 mm for glass
fiber cables. Check the allowed minimum bending radius from the
optical cable manufacturer.
1MRK 506 355-UEN A
Line distance protection REL670 2.1 IEC
Commissioning manual