Signal identification method

A method for identifying characteristics of an optical signal, comprising:

• receiving a data sample representing a first optical signal;
• said receiving step comprising the steps of:
• providing an optical fiber having an amount of optical power therein;
• tapping off a fraction of the optical power present in the optical fiber;
• obtaining an optical power spectrum;
• and parsing the optical power spectrum into a plurality of data samples associated with particular channels of a wavelength division multiplexing communication system;
• wherein each of the data samples comprises a plurality of data points;
• and wherein obtaining the optical power spectrum is limited to a first resolution by the characteristics of an optical spectrum analyzer, and wherein at least one signal characteristic attributed to the first optical signal has a resolution finer than the first resolution;
• comparing the data sample to a set of pre-stored model curves, each model curve representing at least one signal characteristic using a curve-fit analysis;
• determining, for each comparison, an error value representing a quantity of difference between the data sample and a particular one of the pre-stored model curves;
• selecting one of the pre-stored model curves with an error value having a least quantity of difference;
• attributing to the first optical signal the at least one signal characteristic of the selected one of the pre-stored model curves;
• and
• determining center frequency detuning from an ITU grid for the optical signal by performing a least-squares estimate for each characteristic functional form several times with small discrete frequency shifts to the functional form applied each time.