485 optical cable connector grounding
The differential signaling of RS-485 does not require a signal ground to communicate. The RS-485 communication standard is the backbone of many industrial and building automation systems. It allows robust and reliable data transfer across distances of up to 4,000 feet (1,200 meters) using cost-effective twisted pair cabling. For example, Bob Perrin's classic article The Art and Science of RS485 says: Signals A and B are complementary, but this. Two wire devices will likely have non-isolated transceiver which share a reference to chassis ground internally.
Read More
