## 6 Conclusions  
In this work, we have verified applicability of the band-limited reference-free speckle spectroscopy (BLRFS) with the moderate spectral resolution of the applied bench-top instrument to characterize a fluorescence radiation transport in multiple-scattering random media. Another important feature of the examined BLRFS instrument is \"random mixing\" of the collected fluorescence radiation at the optical path between the light-collecting system and the monochromator. This \"mixing\" occurs due to application of a multimode fiber-optic patch-cord as a radiation-transferring channel and causes significant suppression of the detected intensity fluctuations. The considered noise-reduction and data-correction procedures allow for recovery of the spectral dependencies of statistical moments of scan-induced intensity fluctuations even in the case of relatively small coherence lengths of spectrally selected fluorescence radiation compared to the characteristic propagation path of fluorescence photons in the medium. Despite a significant suppression of intensity fluctuations resulting from non-ideal detection conditions (in particular, a small value of \(\beta\)), the features of fluorescence radiation transfer in the probed media caused by an expressed multiple-scattering can be clearly identified using the BLRFS system assembled from commonly available components. These features are elongation of the characteristic propagation path of fluorescence photons due to a presumable negative absorption of fluorescence radiation in a certain spectral interval and a strong influence of the scattering strength on this process. A key point in the application of the BLRFS method for characterization of the light transport in random media is to provide a satisfactory sensitivity of the measured informative parameters (the statistical moments of intensity fluctuations at various wavelengths) to wavelength-dependent changes in the characteristics of the light-medium interactions (in particular, the transport mean free path and the absorption length). A general criterion for such satisfactory sensitivity can be represented in the following form: \(\langle\Delta s\rangle/l_{c}\sim 1\). In the opposite cases \(\langle\Delta s\rangle/l_{c}\approx 0\) and \(\langle\Delta s\rangle/l_{c}>>1\), the measured statistical moments of intensity fluctuations are practically insensitive to variations in the interaction characteristics. It should be noted that for a given probed medium, the average path-length difference \(\langle\Delta s\rangle\) for a given wavelength is fixed, while the coherence length \(l_{c}\) can be adjusted. The achievable upper limit of the coherence length adjustment is defined by the maximal spectral resolution of the applied spectral selection unit (the monochromator), and the coherence length of detected light can be reduced from this limit using enlargement of an output slit of the monochromator (or, similarly, smoothing of the spectral data by a running window at the data processing stage). Another way to reduce the coherence length examined in this work is to apply a multimode fiber-optic patch-cord with a given length as a light-transferring channel between the light-collecting assembly and the monochromator. The enforced reduction of the coherence length of detected radiation can be especially useful in the case of the BLRFS probes of micro- or nano-structured composite systems consisting of dielectric or semiconductor nanoparticles characterized by a large permittivity in the optical range. For these systems, the transport mean free paths of visible and near-infrared light are typically equal to a few micrometers (in our case, see the obtained data for the titania-based samples).