This paper reports a methodology for the design of a segment transmitter for indoor spaces based on optical fibers with different geometric parameters. The segment transmitter made this way aims to simulate the characteristics of a typical VLC transmitter. The article deals with the possibilities of using optical fibers with the possibilities of lighting and communication using the visible spectrum. Design options are studied using a 3D software model, which is then verified using real measurements. A POF (Plastic Optical Fiber) with a large numerical aperture and a core diameter of 550 μm is used to construct the segment transmitter.
Traffic monitoring is the subject of scientific publications and technical solutions, primarily due to the need to optimize and increase traffic safety. There are many systems that can determine direction, velocity, or make vehicle classifications. These can be, for example, traditional camera systems, laser gates, LIDAR scanning, pneumatic sensors, or induction loops. A non-traditional approach is the use of optical fibers as a traffic sensor. Optical fiber sensors use different technologies, one of them being sensors that evaluate the phase change of light (interferometers). The enormous sensitivity of these sensors combined with electromagnetic inertia are promising parameters for deploying system in areas that may be disturbed by magnetic fields or require special security requirements. The focus of this research is an optical fiber sensor based on the Michelson interferometer. The paper deals with the sensitivity of the measuring arm when changing its arrangement. Different configurations of the measuring fiber arrangement in relation to the objects to be monitored lead to the construction of a monitoring system with properties useful for direction monitoring and velocity measurement. This paper deals with the asymmetric configuration of the measuring arm of an optical fiber interferometer. Experiments in outdoor vehicular traffic conditions together with frequency spectrum analysis investigate the usability of the measurement system. The system itself can be extended to classify the measured objects by analyzing the amplitude frequency spectrum and using machine learning.
The article describes the use of fiber-optic interferometer in the rail transport. We proposed a measuring sensor system based on the Mach-Zehnder interferometer. The basic tracked parameter of vehicles are detection (count of vehicles). The proposed system was tested in the real tram traffic. Altogether, 435 vehicles were detected with 100 % success. The basic advantages of the solution include immunity to electromagnetic interference (EMI) and the ability to remotely evaluate information about the traffic.
The authors focused on the problem of production and measurement parameters of optical couplers created from polymer polydimethylsiloxane (PDMS) for fiber-optic sensors. For the production of optical couplers, clear two-component elastomers Sylgard 184 and RTV 615 (manufacturer Dow Corning) was used. These elastomers offer a suitable combination of mechanical and optical properties. For the experiments, a total of 50 optical couplers were created. The effect of thermal aging on their transfer properties was analyzed. The thermal load was performed in a temperature box at 100 and 200 ° C under constant conditions for 48 hours. Measurements were made for a wavelength of 1550 nm and 1310 nm.
During track maintenance operations, the early detection of oncoming rail vehicles is critical for the safety of maintenance personnel. In addition, the detection system should be simple to install at the trackside by minimally qualified personnel. Fibre optic based sensor systems have the inherent advantages of being passive, unaffected by radio frequency interference (RFI) and suffering very low signal attenuation. Such a system therefore represents a good alternative to conventional approaches such as ultrasonic based sensor systems. The proposed system consists of one or more passive fibre trackside sensors and an x86 processing unit located at the work site. The solid fibre connection between sensors and processing unit eliminates the risk of RFI. In addition, the detection system sensors are easy to install with no requirement for electrical power at the sensor site. The system was tested on a tram line in Ostrava with the results obtained indicating the successful detection of all the trams in the monitoring windows using a single sensor. However, the platform allows flexibility in configuring multiple sensors where required by system users.
In this article the author’s team deals with using Wavelength Division Multiplexing (WDM) for Free Space Optical (FSO) Communications. In FSO communication occurs due to the influence of atmospheric effect (attenuation, and fluctuation of the received power signal, influence turbulence) and the WDM channel suffers from interchannel crosstalk. There is considered only the one direction. The behavior FSO link was tested for one or eight channels. Here we will be dealing with modulation schemes OOK (On-Off keying), QAM (Quadrature Amplitude Modulation) and Subcarrier Intensity Modulation (SIM) based on a BPSK (Binary Phase Shift Keying). Simulation software OptiSystem 14 was used for tasting. For simulation some parameters were set according to real FSO link such as the datarate 1.25 Gbps, link range 1.4 km. Simulated FSO link used wavelength of 1550 nm with 0.8 nm spacing. There is obtained the influence of crosstalk and modulation format for the BER, depending on the amount of turbulence in the propagation medium.
In this article the author’s team deals with problems of modulation formats for Free Space Optical (FSO) Communications. FSO communications have high bandwidth, low signal attenuation, quick installation, security, unlicensed band and low cost. In FSO communication occurs due to the influence of atmospheric effect (attenuation, and fluctuation the received power signal, influence turbulence). Here will be dealing modulation schemes OOK (On-Off keying) and Subcarrier Intensity Modulation (SIM) based on a BPSK (Binary Phase Shift Keying). In which will studied their characteristic and effect of atmospheric influence on the received signal. This results in decreased Eye-Diagram, Signal-to-Noise Ratio (SNR) and Bit Error Rate (BER). To evaluate the modulation formats in atmospheric turbulence is used simulation box with heat and wind sources.
This article is dealing with evaluation of air turbulences in uence on the laser beam in the simulation box with regards to change of beam polarization state. For measurement the laser optical source LDM1550 operating at 1550 nm and polarimeter PAX5710 were used. The laser source was placed in front of simulation box that served for generation of stable turbulent environment. The simulation of turbulent environment was generated by high-speed ventilators PMD1212PMB1-A. The thermal turbulences were created by Empire CTH-5000 and Solac TH 8325 heaters. All heaters were placed along the side of simulation box. With the help of polarimeter and detector PAN5710IR3 were then subsequently recorded changes of polarization state of the optical beam with regards to changes of turbulence condition within the box. The results are then discussed and interpreted with the help of statistic methods in the end of the article.
The contribution deals with the influence of DFB laser light on spectral properties of coherent and noncoherent sources. DFB laser, FP laser and surface emitting LED have been as the directed light sources. All sources operated at wavelengths around 1550 nm. As a master DFB laser the tunable laser within range of wavelengths from 1510-1610 nm has been applied. The connection of light sources was carried out with the help of fiber optical couplers 2x2 with division ratio 50:50. The spectral properties of directed light sources were searched in dependence on wavelength changes of tunable laser source. Besides of wavelengths, the optical power of tunable laser has been changed in range - 0,25 dBm – 0 dBm. All changes within directed light sources were searched for various values of driving currents. It was verified experimentally that the mutual interaction DFB-DFB lasers is minimal, the influence of optical power coming from master DFB laser appeared as neglected. Several effects manifested during mutual interaction between master DFB laser and directed FP laser. In this case the intense changes in optical power of particular modes were observed. Some modes had suppressed their powers some modes were dominantly excited. These changes could be the basis for construction of all optical switches or for devices making logical functions. Important spectral changes were also observed in case of mutual interaction between DFB master laser and directed surface emitting LED.
This paper is dealing with design of new type of optical transmitter that is composed of bundle of optical fibers. For design purposes multimode fibers with different dimensions 50/125 and 62.5/125 µm were used. Software designs consisting of 3 or 5 optical fibers in bundle were subsequently evaluated from the point of view of uniform optical intensity distribution and dimensions of light pattern in space.
A high sensitive optical receiver design for the mobile free space optical (FSO) networks is presented. There is an array of photo-detectors and preamplifiers working into same load. It is the second stage sum amplifier getting all signals together. This topology creates a parallel amplifier with an excellent signal to noise ratio (SNR). An automatic gain control (AGC) feature is included also. As a result, the effective noise suppression at the receiver side increases optical signal coverage even with the transmitter power being constant. The design has been verified on the model car which was able to respond beyond the line of sight (LOS).
In this article are presented results from application of fiber optical DTS system within long term research of temperature energy accumulation in Paskov rock massif. In this area was established special measuring station for that purpose, because rock massif in Paskov area has ideal properties for temperature changes measurement. The twelve geothermal boreholes were drilled during this research, which were then used for rock massif heating by Thermal Response Test device. With the help of DTS system was observed how the temperature distribution and penetration in between boreholes in rock massif is. Thanks to the DTS system we were able to determine the Thermal Response Test device heating power influence on the nearest monitoring boreholes.
The free space optic links are used in places, where it is very difficult to use optical fiber links. The advantages of free space optic link are a great bit rate, easy and fast installation, unlicensed frequency band. The greatest disadvantage is transmission medium, which it uses in case of FSO link, the atmosphere. The worst influence on FSO link is caused by atmospherical effect called fog. This article deals with the study of fog influence on FSO link and its bit error ratio. The real measurement of BER with artificial generated fog and FSO link was performed. The measurement was done in laboratory conditions. The results are presented in this article.
Optical fibreless data networks P2P offer fast data transmissions with big transmittance from 1- 10 Gbps on a distance of 1- 6 km. Perfections of such networks are especially flexibility, rapid creation of communications. Sensitivity to atmospheric influences, necessity of light on sight belongs to disadvantages. Transmission through atmosphere be characterized by non-stationarity, inhomogeneity, the influences have random character. It means immediately that it is possible only with difficulty to project conclusions concerning to the measurement on one line upon fiberless line in another position. Contribution tackles a question of forming of the artificial hazy atmospheres, finding the statistical parameters of artificially created foggy atmospheres that could be reproduced to real environment. This work describes created laboratory apparatus powered with fog generator, heat source and ventilating fans, which allow in a controlled way to change the optical transmission inside the bounded space. Laser diode radiation at wavelength of 850 nm is transmitted into created space like this which is scanned with optical power meter after passing of artificially created turbulent vaporous environment. Changes in intensity of the passed lights are captured; the mean value and maximum deviation from the mean value are computed. In this way it is possible to change the reached specific attenuation in dB/km. Owing to turbulences it happens to deviations from the mean value, these abnormalities are characterized by the distribution function that describes the size of turbulences in time. By the help of ergodic theorem then it is possible to deduce that the distribution function of the foggy turbulences gained at continuous time evaluation has same history like the distribution function gained behind the same conditions in the setup in other times. It holds as well that these distribution functions are the same for variety of points in experimental space, provided there are well - kept the same conditions of turbulence creations. Contribution shows the experimental values, shapes of distribution functions, their influence on attenuation of fiberless communication lines and on achieved the transmission BER. At the present time the verification of conclusions is performed from the experimental model on outdoor connecting link working upon the distance of 1,3 km at the transmission rate of 1,25 Gbps.
This article deals with spectral characteristics measurement of fiber couplers which are used for FTTx networks. Due to
WDM systems we are able to communicate with several wavelengths at a time. In xPON systems the data transmission
runs at wavelengths 1310 nm, 1490 and 1550 nm, in case of using singlemode fibers, or at 850 nm and 1300 nm in case
of using multimode fibers. The target of this work is a testing how the individual parameters of fiber coupler behave
whether broad spectrum light source is connected to the input. In sum it was measured four most often used fiber
couplers, fiber coupler in port configuration 1x2 with coupling ratio 50/50%, fiber coupler in port configuration 1x2 with
coupling ratio 30/70%, fiber coupler in port configuration 1x2 with coupling ratio 10/90% and fiber coupler in port
configuration 1×4 with coupling ratio 4×25%. For these fiber couplers it was set insertion losses, coupling ratios,
homogeneities and total losses by using a broad spectrum light source. The results are valuable information for
companies which deal with optical networks.
Fiber optical interferometers belong to highly sensitive equipments that are able to measure slight changes like distortion
of shape, temperature and electric field variation and etc. Their great advantage is that they are insensitive on ageing
component, from which they are composed of. It is in virtue of herewith, that there are evaluated no changes in optical
signal intensity but number interference fringes. To monitor the movement of persons, eventually to analyze the changes
in state of motion we developed method based on analysis the dynamic changes in interferometric pattern. We have used
Mach- Zehnder interferometer with conventional SM and PM fibers excited with the DFB laser at wavelength of 1550
nm. It was terminated with optical receiver containing InGaAs PIN photodiode. Its output was brought into measuring
card module that performs on FFT of the received interferometer signal. The signal rises with the composition of two
waves passing through single interferometer arm. The optical fiber SMF 28e or PM PANDA fiber in one arm is
referential; the second one is positioned on measuring slab at dimensions of 1×2m. A movement of persons over the slab
was monitored, signal processed with FFT and frequency spectra were evaluated. They rose owing to dynamic changes
of interferometric pattern. The results reflect that the individual subjects passing through slab embody characteristic
frequency spectra, which are individual for particular persons. The scope of measuring frequencies proceeded from zero
to 10 kHz. At experiments the stability of interferometric patterns was evaluated as from time aspects, so from the view
of repeated identical experiments. Two kinds of balls (tennis and ping-pong) were used to plot the repeatability
measurements and the gained spectra at repeated drops of balls were compared. Those stroked upon the same place and
from the same elevation and dispersion of the obtained frequency spectra was evaluated. These experiments were
performed on the series of 20 repeated drops from highs of 0,5 and 1m. The evaluation of experiments displayed that the
dispersion of measured values is lower than 4% and could be reduced by PM fibers usage.
Polyaniline hydrochloride was prepared by the oxidation of aniline hydrochloride with ammonium peroxodisulfate in
dilute hydrochloric acid. The polyaniline films were produced during the polymerization on the microscope glass
surfaces immersed in the reaction mixture. The thin film was created and its thickness has been about 100 nm. We have
measured the spectral transmittance together with temperature changes. The polyaniline thin film is conductive and we
observed changes in optical transmittance spectra and reflective spectra with electric current. Optical spectra have been
measured in range from 380 nm to 1010 nm.
The electric conductivity has been changed with silicate substrate. This substrate influenced the free electrons
distribution and therefore the optical properties of polyaniline. Due to electric current going through the nanofilm its
sensitivity to temperature has been increased. We also observed two specific spectral windows. The first one was
characterized by its insensitivity to temperature; the second one has been temperature sensitive. The central wavelength
of insensitive window is about 500nm. This property can be the base for novel sensors structures.
We used Ocean Optics USB spectrometer for evaluation of spectral changes. Wideband white light halogen source
from the same manufacturer has been applied as a light source. Small polarizing dependence of reflected light has been
observed too.
The team of authors tries to provide information on the results of the fiber-optic DTS system application under long-term
research of accumulation possibilities of thermal energy in the rock mass in this article. In 2006, was in Ostrava
implemented the largest object in the Czech Republic, which is heated by heat pump system. It is a multi-purpose aula at
VŠB-TU + CIT (Center for Information Technology). The installed heat pump system consists of ten heat pumps with a
total output of 700kW and 110 wells about 140m deep. The applied research is conducted in two measuring polygons
("Big" and "Little" polygon). Simultaneously with fiber-optic DTS system is applied group of PT1000 temperature
sensors and Geothermal Response Test (GERT). Fiber-optic DTS system is deployed inside polyethylene PE collector
via a special sensory fiber optic cable. The ecological antifreeze mixture, based on the technical spirit, used for the
collection and delivery of energy to the rock mass circulates inside of PE collector. PT1000 temperature sensors are
placed at certain intervals on the outer side of the PE U-tube within the heat well. The result of application of the fiberoptic
DTS system is information about the heat profile of wells, thermal conductivity of the geological environment and
the impact of external changes in the thermal wells, along with the accumulation possibilities of thermal energy in the
rock mass (over-summer period).
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