42 demonstrate that the wavelength changes as before u2014 time diagram 3 c 1 the modulated optical signal shown in the exaggerated scale in the time diagram 3 c 2 demonstrates changes in the phase caused by the fiber dispersion it indicates delays with respect to the signal which entered the fiber 3 b 2 as can be seen for positive dispersion d at the portions of the received signal corresponding to those halves of the sine wave when the carrier wavelength is more than the average nominal the delay of the modulated signal increases and reaches its maximum when the wavelength is maximally differs from the average to the contrary at the portions of the signal corresponding to the halves of the sine wave where the carrier wavelength is less than the average the data delay has a different sign and also reaches its maximum when the wavelength maximally differs from the average this can easily be seen in the graphs u201c c u201d according to equation 1 since changes in the wavelength cause changes in the data delay the phase differences between the signal representing the wavelength changes u03bb t and the signal representing the data delay t t u2014 will represent the sign of the dispersion it should.