One of the most prospective technologies and one of the ways of data transmission are determined. The parameters of optical loss resource in the network are given. The influence of optical power in the line on quality of digital television image during transmission in NGN telecommunications network using GPON access technology is considered. Equipment NetUP IPTV Combine, Optical Line Terminal, Optical Network Terminal, optical switch, optical attenuator were used as the head station During the experiment. Step dependence of the image quality on optical power in the channel is revealed. Image quality was evaluated by subjective and objective method of evaluation. The least squares method, method of equation of straight line passing through two points were used. There are several figures attached to the text for the purpose of results explanation. Recommendations of the International Telecommunication Union were used in the calculations.