an object of the present invention is to provided a device that performs dispersive compensation in an optical fiber transmission path , such as performing waveform shaping in optical fiber transmission . this adaptive dispersion compensating element is provided with a chirp bragg grating 104 formed in an optical fiber , a temperature gradient impressing means 105 that impresses a temperature gradient along the longitudinal direction of the chirp bragg grating , a spectral resolving means 106 that spectrally resolves the output light from the chirp bragg grating , a detecting means 107 that detects the output light from the spectral resolving means , and a control means 108 that performs feedback control of the temperature gradient impressing means based on the output from the detecting means and provides a compact and high - stability device that performs the dispersive compensation in the optical fiber transmission path , such as performing the waveform shaping in the optical fiber transmission .