This paper studies numerical characteristics and characteristic matrix of attenuation spectrum of G.652.D single-mode optical fibres, and considers the attenuation factor to optimize the mathematical expression of optical fibre attenuation spectrum model. The study aims to improve the digital modeling ability of optical fibre attenuation spectrum for research and manufacturing of optical fibre and development of optical system.

ITU-T G.650.1(2020) provides an example matrix for use in the "spectral attenuation modelling" method to calculate attenuation spectrum of G.652.D single-mode optical fibres. This paper analyzes and demonstrates that the spectral attenuation model method could approximately obtain optical fibre attenuation spectrum with low error by characteristic matrix corresponds to four wavelengths. An optimized attenuation spectrum characteristic matrix is given by considering sources of attenuation, and the effect of the new matrix is verified with attenuation spectrum test data of 1000 fibre samples.

Main research results of this paper include: (1) When there is a good correspondence between the wavelengths corresponding to the fibre attenuation spectrum characteristic matrix and main attenuation sources of G.652.D fibre, the spectral attenuation model method is able to approximate the fibre attenuation spectrum with small errors; (2) An attenuation spectrum characteristic matrix of G.652.D single mode fibre is calculated based on attenuation sources of the fibre, and this matrix is able to reflect mechanism of fibre attenuation better, compared to the characteristic matrix calculated solely from data; (3) Verification with test data of optical fibre samples shows that the new matrix could calculate the attenuation spectrum of optical fibre samples with comparable small errors.

This paper studies and concludes that the reason why the spectral attenuation model method is able to approximate the optical fibre attenuation spectrum is that the corresponding wavelengths of the characteristic matrix has a good correspondence with main attenuation sources of the optical fibre. Combining with the attenuation sources, optimized characteristic matrix can be calculated. The new matrix could reflect the mechanism of the optical fibre attenuation and also effectively calculate the attenuation spectrum of the optical fibre samples with small errors.