Here, a is a constant. The slope b = μac0 is then used for the calculation of the linear light absorption coefficient μa. Such fitting has usually a very good correlation (r > 0.999) with the detected signal front, which provides high accuracy of the light absorption coefficient determination (RSD ca. 0.1% [27], [28] and [31]). As described above by Eqs. (2) and (6), a part of the signal PROFILE which is closer than τL to the signal maximum is not exponential and should not be used in fitting.