This paper is a review of the scientific works of the co-authors. In the paper, the basic principles of action of sensor systems with optical response of two types are considered. In particular, two spectroscopic technologies for probing some objects or events in non-living (synthetic) or biological environments are considered. In the first part of the work, sensor technologies related to the use of probes with optical response specially introduced into the sensor system are analyzed. As a rule, these probes are specially developed systems, the spectral properties of which change significantly under interaction with the object of probing. In the first part of the work, sensors of the first type are considered. In particular, the main ideas used in this type of sensors are given and specific examples of the use of such sensors are analyzed: specially created molecules that have a low fluorescence quantum yield due to a significant number of mechanical intramolecular degrees of freedom. The intercalation of such probes to large biomolecules leads to a change in the spectral characteristics of these probes, in particular, to a significant increase in fluorescence (up to 1000 times). The case of two-photon absorption of molecular probes in the transparency window of biological tissues is examined. Semiconductor and metal nanoparticles whose absorption and fluorescence spectra depend on their sizes were also proposed as probes of the first type (as sensors of elastic vibrations of the environment).The second part of the paper is devoted to the mechanisms of autosensing (the case when the medium's own optical centers are used to detect processes occurring in biological or synthetic systems). The main ideas that underlie the operation of sensors with optical response of this type were analyzed, and examples of such use were also given. In particular, the use of the own spectral properties of biomacromolecules and some coenzymes for changes in the external environment is considered. The use of the optical response of synthetic macromolecules on the value of their molecular weight was also analyzed.
