geometrical, optomechanical, optothermal, and structure properties of natural, optical and polymeric fibres [1,2]. Many authors [3][4][5][6] have utilized the two-and multiplebeam interference techniques to detect these properties with high accuracy. The most common interferometric techniques include Pluta polarizing interference microscope [7], Fizeau interferometer [8], Michelson interferometer, Mach-Zehnder interferometer [1] and digital holographic interferometry [9]. In [3,4,6], two-beam Pluta polarizing interference microscope was used to study optomechanical and optothermal properties of the different polymeric fibres. These studies allow the recording of instantaneous changes in the optomechanical and optothermal properties of those fibres samples during the stretching or heating processes. These changes help to understand the behaviour of such fibres under the influence of these actions. To gain the information utilized to achieve the study, the contour line approach [6] is used. Communally, implementation of the previously mentioned interference techniques in fibre characterization utilizing the contour line approach requires that the interference fringes be perpendicular to the test fibre sample, and thus, a time-consuming adjustment process is necessary.The interference pattern analysis techniques [10] can be defined as methods to extract the phase distribution of the object under investigation hidden in the interference pattern using computer operations. These techniques have been used as an assistant factor for the interference pattern to extract the phase values with high degree of accuracy. The most widely phase extraction techniques are the spatial carrier frequency method (Fourier analysis techniques) [11] and the temporal phase shifting method [12].The temporal phase shifting technique [12][13][14] is a method to calculate the phase of a pixel relying on the value of that pixel in several interference patterns. So this Abstract We present an extension of the adaptive spatial carrier frequency method which is proposed for fast measuring optical properties of fibrous materials. The method can be considered as a two complementary steps. In the first step, the support of the adaptive filter shall be defined. In the second step, the angle between the sample under test and the interference fringe system generated by the utilized interferometer has to be determined. Thus, the support of the optical filter associated with the implementation of the adaptive spatial carrier frequency method is accordingly rotated. This method is experimentally verified by measuring optical properties of polypropylene (PP) fibre with the help of a Mach-Zehnder interferometer. The results show that errors resulting from rotating the fibre with respect to the interference fringes of the interferometer are reduced compared with the traditional band pass filter method. This conclusion was driven by comparing results of the mean refractive index of drown PP fibre at parallel polarization direction obtained from the new and ada...