In this paper, we present a fibre-optic sensor for simultaneous measurement of refractive index and thickness of liquid layers.We designed an experimental low-coherence setup with two broadband light sources and an extrinsic fibre-optic Fabry–Pérot interferometer acting as the sensing head.We examined how the refractive index of a liquid film and its thickness affect spectrum at the output of a fibre-optic interferometer. We performed a series of experiments using two light sources and only one sensing head. The spectra were collected in ranges of 1220÷1340 nm and 1500÷1640 nm. The obtained results show that using two spectra recorded simultaneously for two wavelength ranges enables to determine thickness in a range of 50÷500 μm, and refractive index of a liquid film in a range of 1:00÷1:41 RIU using only one sensing head.

Distributed measurement often relies on sensor networks. In this paper, we present the construction of low-coherence fiber-optic Fabry–Pérot sensors connected into a quasi-distributed network. We discuss the mechanism of spectrum modulation in this type of sensor and the constraints of assembly of such sensors in the network. Particular attention was paid to separate the signals from individual sensors which can be achieved by cavity length-based addressing. We designed and built a laboratory model of a temperature sensors network. The employed sensors are low-coherence Fabry–Pérot interferometric sensors in a fiberoptics configuration. The extrinsic sensor cavity utilizes the thermal expansion of ceramics, and the sensors are addressed by the different lengths of the cavities. The obtained test results showthat the signal components from each sensor can be successfully separated, and the number of sensors could be expanded depending on the FWHM of the light source.

In recent years organic semiconductors have been given attention in the field of active materials for gas sensor applications. In the paper the investigations of the optoelectronic sensor structure of ammonia were presented. The sensor head consists of polyaniline and Nafion layers deposited on the face of the telecommunication optical fiber. The elaborated sensor structure in the form of Fabry-Perot interferometer is of the extremely small dimension – its thickness is of the order of 1 um. Many sensor structures of diffierent combinations of the polyaniline and Nafion layers were constructed and investigated. The optimal solution seems to be the structures with small number of polianiline layers (up to three).