METHOD FOR MEASURING DISTRIBUTION OF EXCESS OPTICAL FIBER LENGTH IN OPTICAL CABLE MODULE Russian patent published in 2017 - IPC G02B6/44 

FIELD: measuring equipment.

SUBSTANCE: in the claimed method for measuring the distribution of the excess optical fiber length in the optical cable module, the backscattering characteristics of the optical fiber are preliminarily measured at two wavelengths. According to these characteristics, the distribution of the optical fiber attenuation coefficients along the cable α(z, λ), where z is the distance from the proximal end along the cable length, λ - the wavelength, at which the backscattering characteristic of the optical fiber was measured, then at each point z along the cable length, the difference between the optical fiber attenuation coefficients is measured at different wavelengths Δα(z). Then, the optical fiber bending radii are calculated in the optical cable module along the cable length by the formula: R(z)=R₀-Δα_ij(z)/η(λ_i) (1), where R₀ and η(λ) are parameters of the optical cable, and according to the distribution of the optical fiber bending radii in the optical cable module, the distribution of the excess optical fiber length is determined in the optical cable module along the cable length. Herewith the measurements of the optical fiber backscattering characteristics are performed at a low negative temperature after the optical cable has been at the given temperature for a certain predetermined time interval, the distribution of the excess optical fiber length in the optical cable module is determined according to the distribution of the optical fiber bending radii in the optical cable module along the cable length EFL(z, T_m) at the temperature, at which the measurements were made, and then the distribution of the excess optical fiber length in the optical cable module is determined along the cable length at the given temperature T by the formula: EFL(z, T)=EFL(z, T_m)-(T-T_m)⋅ Δε_T (2), where Δε_T - the difference between the coefficients of the linear module material expansion and quartz glass.

EFFECT: reducing the error in measuring the attenuation coefficients of the optical fiber at the bends and, as a consequence, reducing the error in measuring the excess optical fiber length in the optical cable module compared to the prototype.

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