FIELD: measuring equipment.
SUBSTANCE: according to the method for measuring the excess optical fibre length in a modular tube of an optical cable, characteristics of back Raileigh scattering of optical cable optical fibre of modular design are measured at least at two values of temperature of medium surrounding the cable, including low negative temperature. According to these characteristics, the excess optical fibre length in the modular tube of the optical cable at regular sites at a low negative temperature are determined. Characteristics of back Raileigh scattering of optical cable optical fibre of modular design are measured at positive and negative temperature of medium surrounding the cable, and the value of the excess optical fibre length in the modular tube of the optical cable at regular site at low negative temperature, at which the measurements have been carried out, are calculated by the formula: 
, 
, where α(T0) is the optical fibre attenuation coefficient defined for regular site by the characteristic of the back Raileigh scattering measured at positive temperature; α(Ti) is the optical fibre attenuation coefficient defined for the regular site by the characteristic of the back Raileigh scattering measured at i-th low negative temperature; B is the parameter constant for the given cable design at the wavelength at which the measurements have been carried out.
EFFECT: increasing the scope and reducing the error in measuring the excess optical fibre length in the modular tube of the optical cable.
1 dwg
