The two devices are correctly configured. When the two devices ping each other, packet loss occurs. If the ping packet size is small, the packet loss ratio is low. If the ping packet size is large, the packet loss ratio is high.
Connect the ground cables of the AR1220 and optical transceiver to ground points. The fault is rectified.
The AR1220 and NE40E are interfered by the ground potential difference.
Before starting a device, check whether all components on the device are correctly connected.