In this article, the advantages of the unity of sensory and telecommunication approaches will be shown, using examples of monitoring systems for second-generation telecommunication passive optical networks (PON). In comparison with the TDM network architecture, its combination with the WDM architecture is much more efficient, both in terms of the number of channels per fiber, and in terms of the number of channels per laser. This architecture showed a high coverage of monitoring objects by sensors in optically efficient network organization with their small number. Theoretically, the number of sensors in the fiber optical sensor system (FOSS) can be expanded to 256 sensors using two fibers. Note that in the fiber optical telecommunication system (FOTS) the maintenance of 256 PON TDM-WDM terminals is a typical requirement. Thus, monitoring tasks for FOTS and FOSS PON are based on unified approaches. In general, when designing a FOTS, it is necessary to take into account the close relationship that exists between all the factors that determine the characteristics of the network elements, with the existing economic conditions, which will create an optimal network.