The phase jitter enables to assess quality of signals transmitted in a bi-directional, long-distance fibre optic

link dedicated for dissemination of the time and frequency signals. In the paper, we are considering

measurements of jitter using a phase detector the detected frequency signal and the reference signal are

supplied to. To cover the wideband jitter spectrum the detected signal frequency is divided and – because of

the aliasing process – higher spectral components are shifted down. We are also examining the influence of

a residual jitter that occurs in the reference signal generated by filtering the jitter occurring in the same signal,

whose phase fluctuations we intend to measure. Then, we are discussing the evaluation results, which

were obtained by using the target fibre optic time and frequency transfer system.

We experimentally studied three different D-shape polymer optical fibres with an exposed core for their applications as surface plasmon resonance sensors. The first one was a conventional D-shape fibre with no microstructure while in two others the fibre core was surrounded by two rings of air holes. In one of the microstructured fibres we introduced special absorbing inclusions placed outside the microstructure to attenuate leaky modes. We compared the performance of the surface plasmon resonance sensors based on the three fibres. We showed that the fibre bending enhances the resonance in all investigated fibres. The measured sensitivity of about 610 nm/RIUfor the refractive index of glycerol solution around 1.350 is similar in all fabricated sensors. However, the spectral width of the resonance curve is significantly lower for the fibre with inclusions suppressing the leaky modes.

We experimentally studied three different D-shape polymer optical fibres with an exposed core for their applications as surface plasmon resonance sensors. The first one was a conventional D-shape fibre with no microstructure while in two others the fibre core was surrounded by two rings of air holes. In one of the microstructured fibres we introduced special absorbing inclusions placed outside the microstructure to attenuate leaky modes. We compared the performance of the surface plasmon resonance sensors based on the three fibres. We showed that the fibre bending enhances the resonance in all investigated fibres. The measured sensitivity of about 610 nm/RIU for the refractive index of glycerol solution around 1.350 is similar in all fabricated sensors. However, the spectral width of the resonance curve is significantly lower for the fibre with inclusions suppressing the leaky modes.

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.

The aim of the research was implementation of fibre Bragg grating sensors and the Aramis system to monitor strain, displacement and stress values in new materials used in the building industry. Selected elements of a residential building made of the Polytech material with a 60% content of the EPS granulate from recycling were tested: a prefabricated wall with a lintel, a reinforced concrete floor slab, a lintel, a reinforced concrete column and a wall. Long-term testing was also carried out taking account of changes in environmental conditions. The methodology of the research was based on the development of purpose-made dedicated FBG strain sensors, laboratory calibration and the embedding of the sensors in the tested element structure. The proposed system of continuous measurements made it possible to determine real strain, displacement and stress values in selected elements of the Polytech structure for a facility founded in a difficult geotechnical terrain (subsoil).

The research and analysis of the bactericidal properties of the spacer knitted fabric with the UV-C system are presented in this paper. The disintegration factor affecting the bacteria in the knitted fabric is the UV-C radiation in the range of 265–270 nm distributed via woven optical fibres. The way of integrating elements of the system generating the UV-C radiation in the structure of the spacer knitted fabric was designed, as well as various configurations of optical fibres arrangement, fibre density, number of radiation sources, and diode types were tested. The material was contaminated with selected microorganisms indicative of sanitary contamination and important in terms of nosocomial infections. The scope of the research included microbiological (quantitative and qualitative) analyses of selected taxonomic groups of microorganisms (mesophilic bacteria, fungi, actinomycetes) before and after the irradiation process. The analysis of the research results and the applied modification of the knitted fabric turned out to be effective in reducing the amount of potentially pathogenic microorganisms.

Dynamic angle measurement (DAM) plays an important role in precision machining, aerospace, military and artificial intelligence. Because of its advantages including high sensitivity, solid state and miniaturization, fibre-optic gyroscope (FOG) has great application prospects in the field of DAM. In this paper, we propose a dynamic angle metrology method based on FOG and a rotary table to evaluate the DAMaccuracy with FOG. The system synchronously collects data from the FOG and rotary table, and analyses the DAM accuracy of the FOG for different sway conditions compared with that of the angle obtained from the rotary table. An angle encoder in the rotary table provides absolute or incremental angular displacement output with angular displacement measurement accuracy of 10′′ (0:0028◦) and angular displacement repeat positioning accuracy of 3′′ (0:00083◦), and can be used as an angle reference. The experimental results show that the DAM accuracy of the FOG is better than 0:0028◦ obtained with the angular encoder, and the absolute DAM accuracy of the FOG is better than 0:0048◦ for given conditions. At the same time, for the multi-path signal synchronization problem in the metrology field, this paper proposes a signal delay measurement method combining test and algorithm procedures, which can control a delay within 25 μs.

We describe an all−in−fibre apparatus for Constant Intensity Direct Absorption Spectroscopy (CIDAS) for gas concentration measurements which keeps the power of a diode laser constant along the frequency sweep. The reduction of the large variation of the laser power, connected to the frequency scan, enhances the ability of detecting small variations in a background signal, resulting in an increase of the sensitivity with respect to standard direct absorption techniques. Moreover, CIDAS allows for a real−time observation of the absorption signals without any kind of post−detection processing. The apparatus has been tested with carbon dioxide (CO₂) and methane (CH₄), around 1.57 and 1.65 μm, respectively.

This paper investigates the noise levels present at various points in the FOSREM type fiber optic seismograph. The main aim of this research was to discover magnitudes of noise, introduced by various components of the analog and optical circuits of the device. First, the noise present in the electronic circuit without any optics connected is measured. Further experiments show noise levels including the detector diode not illuminated and illuminated. Additional tests were carried out to prove the necessity of analog circuitry shielding. All measurements were repeated using three powering scenarios which investigated the influence of power supply selection on noise. The results show that the electronic components provide a sufficient margin for the use of an even more precise detector diode. The total noise density of the whole device is lower than 4⋅10−7 rad/(s√Hz). The use of a dedicated Insulating Power Converter as a power supply shows possible advantages, but further experiments should be conducted to provide explicit thermic confirmation of these gains.

In this work the influence of the cavity parameters on optical losses of a simple intensity-based in-line refractive index sensor utilizing a micromachined side-hole fibre was studied by means of numerical simulations. To perform these simulations, the Authors used the finite-difference time-domain method. The proposed sensor setup consists of light source, micromachined optical fibre as a sensor head, and a detector which makes it low-cost and easy to build. The changes of the external refractive index can be, therefore, recovered by direct measurements of the transmitted intensity from which insertion loss values can be calculated. By changing geometry of the cavity micromachined into the side-hole optical fibre, it was possible to determine its influence on the final sensor sensitivity and measurements range. Based on the provided analysis of simulations results, a simple fibre optic sensor can be fabricated mainly for sensing external liquids refractive index for application in biochemistry or healthcare.

Preliminary results of laboratory and field tests of fibre optic rotational seismographs designed for rotational seismology are presented. In order to meet new directions of the research in this field, there is clearly a great need for suitable and extremely sensitive wideband sensors. The presented rotational seismographs based on the fibre optic gyroscopes show significant advantages over other sensor technologies when used in the seismological applications. Although the presented results are prepared for systems designed to record strong events expected by the so-called “engineering seismology”, the described system modification shows that it is possible to construct a device suitable for weak events monitoring expected by basic seismological research. The presented sensors are characterized, first and foremost, by a wide measuring range. They detect signals with amplitudes ranging from several dozen nrad/s up to even few rad/s and frequencies from 0.01 Hz to 100 Hz. The performed Allan variance analysis indicates the sensors main parameters: angle random walk in the range of 3 ∙ 10 ⁻⁸ - 2 ∙ 10 ⁻⁷ rad/s and bias instability in the range of 2 ∙ 10 ⁻⁹ - 2 ∙ 10 ⁻⁸ rad/s depending on the device. The results concerning the registration of rotational seismic events by the systems located in Książ Castle, Poland, as well as in the coalmine “Ignacy” in Rybnik, Poland were also presented and analysed.

The main goal of the article is to present the concept of using a simulation environment when designing an advanced fibre-optic seismometer (FOS) using a field-programmable gate array (FPGA) computing system. The first part of the article presents the advanced requirements regarding the FOS principle of operation, as well as the measurement method using a closed-loop operation. The closed-loop control algorithm is developed using the high-level language C++ and then it is synthesised into an FPGA. The following part of the article describes the simulation environment developed to test the operation of the control algorithm. The environment includes a model of components of the measurement system, delays, and distortions in the signal processing path, and some of the measurement system surroundings. The article ends with a comparison of simulation data with measurements. The obtained results are consistent and prove correctness of the methodology adopted by the authors.