Light amplifying apparatus for wavelength division multiplexing capable for determining change in number of multiplexed wavelength signals

A method by a photo amplifying apparatus of determining change in the number of multiplexed wavelengths in received wavelength division multiplexed signals, wherein a measuring point is provided in one of an input stage, an intermediate stage, and an output stage, comprising the steps of:

• measuring the light power of a specific wavelength at said measuring point;
• measuring the light power of all wavelengths at said measuring point;
• and
• determining, when the measured light power of said specific wavelength does not change, and the measured light power of all wavelengths changes, change in the number of multiplexed wavelengths based on the measured light power of said specific wavelength and the measured light power of all wavelengths.

A method by a photo amplifying apparatus of determining change in the signal level of wavelength division multiplexed signals, comprising the steps of:

• measuring the light power of a specific wavelength at a measuring point provided in said photo amplifying apparatus;
• measuring the light power of all wavelengths at said measuring point;
• and
• determining, when change in the measured light power of said specific wavelength is equal to change in the measured light power of all wavelengths, change in the signal level of wavelength division multiplexed signals transmitted through a photo transmission path based on said change in the measured light power of said specific wavelength or said change in the measured light power of all wavelengths.

A method by a photo amplifying apparatus of processing wavelength division multiplexed signals in which a plurality of wavelengths are multiplexed, comprising the steps of:

• receiving said signals from an exterior source;
• measuring the light power of a specific wavelength at a measuring point provided in said photo amplifying apparatus;
• measuring the light power of all wavelengths at said measuring point;
• determining, when change in the measured light power of said specific wavelength is equal to change in the measured light power of all wavelengths, change in the signal level of wavelength division multiplexed signals transmitted through a photo transmission path based on said change in the measured light power of said specific wavelength or said change in the measured light power of all wavelengths;
• and
• determining, when the measured light power of said specific wavelength does not change, and the measured light power of all wavelengths changes, change in the number of multiplexed wavelengths based on the measured light power of said specific wavelength and the measured light power of all wavelengths.