Patent ID: 8396366

Claim:
A method of operating an interface between a network node and an optical fiber link to a remote node at an opposite end of said link, said link having first and second optical fiber loops, each optical fiber loop having a transmitting optical fiber and a receiving optical fiber, said method comprising: transmitting signals from said node through transmitting optical fibers of both of said first and second optical fiber loops; receiving signals for said node through one of said receiving optical fibers of said first and second optical fiber loops; monitoring receiving optical fibers of both of said first and second optical fiber loops; detecting a fault on one of said receiving optical fibers of said first and second optical fiber loops; switching off a transmitting optical fiber of said optical fiber loop to which said fault-detected receiving optical fiber belongs; maintaining reception of signals for said node through said one of said receiving optical fibers of said first and second optical fiber loops if said fault-detected receiving optical fiber is the other receiving optical fiber of said first and second optical fiber loops, or switching reception of signals for said node through said other receiving optical fiber of said first and second optical fiber loops if said fault-detected receiving optical fiber is said one receiving optical fiber of said first and second optical fiber loops; and maintaining transmission of signals from said node through a transmitting optical fiber of an optical fiber loop to which said fault-detected receiving optical fiber does not belong; whereby said interface performs both protection and safety measures for said network node.