Patent ID: 7388657

Claim:
A method comprising: transmitting at least one optical time domain reflectometry (OTDR) test signal on a first optical path, wherein said OTDR test signal is reflected by at least one reflecting element in said first optical path and a reflected OTDR test signal is coupled onto a second optical path; detecting said at least one reflected OTDR test signal on said second optical path to obtain OTDR data; applying at least one linear fit to said OTDR data, each said linear fit extending to a point corresponding to a known repeater location, said applying said linear fit including determining a slope and vertical offset of lines to be fit to portions of said OTDR data corresponding to spans in said optical path; calculating an average slope value of said lines fit to said portions of said OTDR data and re-applying said linear fit using said average slope value; deriving loop gain data from said OTDR data by identifying an intersection of each said linear fit and said known repeater location; and monitoring a condition of said first optical path using said loop gain data.