Patent ID: 7561798

Claim:
A method for testing an optical fiber link, comprising: selecting a wavelength of a test signal based on a type of testing to be conducted and a type of symptom to be detected; generating a first test signal of the selected wavelength; employing a first wavelength division multiplexer (WDM) to receive said first test signal via a port of said first WDM prior to propagation along said optical fiber link and multiplex said first test signal onto said optical fiber link along with a communication signal, wherein said first test signal is used in a test of said optical fiber link; employing a second WDM spaced apart from said first WDM along the optical fiber link to demultiplex said first test signal from said optical fiber link and output said first test signal via a port of said second WDM; evaluating said first test signal output via the port of said second WDM and without further propagation along said optical fiber link to thereby test said optical fiber link; generating a second test signal of the selected wavelength; measuring optical power of said first and second test signals; employing the second WDM to receive said second test signal via a port of said second WDM prior to propagation along said optical fiber link and multiplex said second test signal onto said optical fiber link along with a communication signal; employing the first WDM to demultiplex said second test signal from said optical fiber link and output said second test signal via a port of said first WDM; and evaluating said second test signal output via the port of said first WDM and without further propagation along said optical fiber link to thereby test said optical fiber link, wherein said first and second test signals are spaced apart from said communication signal by at least about 100 nm.