A bend-loss tolerant multimode fiber transmission system is provided. The system includes: a transmission fiber having a core and a cladding, and a mode-launching system for selectively exciting only a useful portion of the transmission modes, that portion corresponding to high effective refractive indices relative to a refractive index of the cladding the useful portion corresponding to a substantial number of modes. The mode-launching system may include a lead-in fiber, coupled to the transmission fiber, supporting a number of lead-in modes substantially corresponding to the number of transmission modes in the useful portion. The transmission fiber may have a refractive index profile, within a region of its core that is aligned with the lead-in fiber core, which has a shape that matches a refractive index profile shape in the lead-in fiber core. The transmission fiber core may have a graded refractive index profile that is parabolic or nearly parabolic or truncated.
COBISS.SI-ID: 18727958
One important theme in captioning is whether the implementation of captions in individual sign language interpreter videos can positively affect viewers% comprehension when compared with sign language interpreter videos without captions. In our study, an experiment was conducted using four video clips with information about everyday events. Fifty-one deaf and hard of hearing sign language users alternately watched the sign language interpreter videos with, and without, captions. Afterwards, they answered ten questions. The results showed that the presence of captions positively affected their rates of comprehension, which increased by 24% among deaf viewers and 42% among hard of hearing viewers. The most obvious differences in comprehension between watching sign language interpreter videos with and without captions were found for the subjects of hiking and culture, where comprehension was higher when captions were used. The results led to suggestions for the consistent use of captions in sign language interpreter videos in various media.
COBISS.SI-ID: 18752790
This letter presents a multiplexed fiber-optic sensor array suitable for detection of liquid intrusions, spills, and leaks. The proposed detection systems is based on active heating and observation of temperature changes in short sections of optically absorbing (vanadium-doped) optical fibers that were interconnected into a sensing array by a standard single-mode optical fiber. The heating of the vanadium-doped fiber sections was achieved by application of a common 980-nm pump laser source. The associated signal processing and integration utilizes a simple, custom-designed optical time domain reflectometry that relies on only a few low-cost standard telecom components.
COBISS.SI-ID: 18911766
This letter presents a miniature, all-fiber fiber optic twist/rotation sensor. The proposed sensor consists of polarization maintaining lead-in fiber (PMF), a short section of standard (fully circularly symmetric) single-mode fiber, which is exposed to twist/axial rotation, an all-fiber quarter-wave wave plate, and a reflective layer. This sensor exploits the inability of a short-section circular symmetric single-mode fiber to change the polarization state or spatial E-field vector orientation of an optical wave when exposed to mechanical twist/rotation. Thus, the twisting of a single-mode fiber in the proposed configuration causes displacement of the lead-in PMF and wave-plate axis. This enables encoding of the twist angle into a power ratio of the lead-in PMF linearly polarized modes that is propagated in a backward direction by the application of a wave plate, which can be straightforwardly measured by a simple interrogation system. The proposed design allows for compact sensor design with sensors’ active lengths below 5 mm. The unambiguous angular measurement range of the proposed sensor is ±45°. An angular resolution better than 0.03° was demonstrated, while the temperature sensitivity proved to be (0.011 °C. To achieve low-temperature sensitivity of the sensing system, a combination of different PMFs was used to eliminate the temperature sensitivity of the PMF-based wave plate, which is the main source of temperature-induced errors in the presented setup.
COBISS.SI-ID: 18417174
This letter presents a miniature fiber-optic sensor created at the tip of an optical fiber suitable for simultaneous measurement of relative humidity and temperature. The proposed sensor is based on two cascaded Fabry-Perot interferometers, the first configured as a relative humidity sensing element made from silica micro-wire coated with thin porous SiO2 layer, and the second as a temperature sensing element, made from a segment of a standard single mode fiber. The sensor has linear characteristics for both measurement parameters, and sensitivity of 0.48 degree/%RH and 3.7 degree/°C.
COBISS.SI-ID: 19189782