Patent ID: 7010189

Claim:
An optical monitoring apparatus for use in a wavelength division multiplexing network for monitoring a wavelength division multiplexing (WDM) signal in a network system, comprising: a pump laser; a WDM coupler for coupling said WDM signal and said pump laser; an erbium-doped fiber that is 6 meters in length receiving said WDM signal and said pump laser transmitted from said WDM signal, and scanning gain profile of said WDM signal; a saturated tone light source for controlling said gain profile of said WDM signal; an optical circulator coupled with said erbium-doped fiber, receiving said saturated tone light source, and subsequently outputting an output signal with a specified frequency; and wherein said saturated tone light source is a distributed feedback (DFB) laser with a wavelength of 1540 nm and power of 15 dBm.