Mitsubishi GOT1000 Series Connection Manual page 214

3 Checking the wiring state (for optical loop system only)
Check if the optical fiber cable is connected correctly in [Loop test] of GX Developer.
For the GX Developer operation method, refer to the following manual.
(1) Check the [Receive direction error]. (The display example on GX Developer Version 8)
Startup procedure
GX Developer
5 - 22
5.2 Preparatory Procedures for Monitoring
5.2.7 Checking for normal monitoring
Q corresponding MELSECNET/H Network System Reference Manual (PLC to PLC
network)
[Diagnostics] [MELSECNET (II)/10/H diagnostics]
Loop test