The paper presents the results of a study of the effect of the composition gradient and refractive index on the attenuation of an optical signal at a wavelength of 1.55 microns. The attenuation measurements were carried out by the breakage method and the comparison method, the attenuation by both methods was 0.9 dB/cm when waveguides were formed along the change in the lithium composition in the crystal plate of the composition Li0.94...0.98Nb1.06...1.02O3.12...3.04.