Wavelength meter

A wavelength meter is combined with optical elements to measure the wavelength in order to change communication channels by adjusting the wavelength. The wavelength meter has two wavelength-dependent interferometers with a lower sensitivity on large wavelength ranges and a higher sensitivity on small wavelength ranges, respectively. Each interferometer provides an output signal having an intensity that varies with wavelength. Using the interferometer with a lower sensitivity on large wavelength ranges to first determine a rough range of the wavelength of an incident optical signal, it then uses the interferometer with a higher sensitivity on small wavelength ranges to measure the accurate wavelength of the incident optical beam.