The methods of generating spread-spectrum sequences with Mach-Zehnder interferometer are studied, also the principle and the scheme of a reported Chebyshev chaotic sequence generator is analyzed. To eliminate the limitation caused by the size of optical elements, a new scheme using the properties of cosine function is put forward. By using voltage to adjust the refractive index of the arms of Mach-Zehnder interferometer, a wavelength adaptive generator can be realized, with which different Chebyshev optical chaotic sequences with different input wavelengths could be obtained.