Ubiquitous satellite communications are in a leading position for bridging the digital divide. Fulfilling such a mission will require satellite services on par with fibre services, both in bandwidth ...and cost. Achieving such a performance requires a new generation of communications payloads powered by large-scale processors, enabling a dynamic allocation of hundreds of beams with a total capacity beyond 1 Tbit s
. The fact that the scale of the processor is proportional to the wavelength of its signals has made photonics a key technology for its implementation. However, one last challenge hinders the introduction of photonics: while large-scale processors demand a modular implementation, coherency among signals must be preserved using simple methods. Here, we demonstrate a coherent photonic-aided receiver meeting such demands. This work shows that a modular and coherent photonic-aided payload is feasible, making way to an extensive introduction of photonics in next generation communications satellites.
We demonstrate a partially degenerated intermodal four-wave mixing (FWM) process realized in a few-mode nonlinear optical fiber, leading to the effective generation of visible red and blue light from ...532 nm sub-nanosecond pulses. We present a self-seeded FWM configuration with a signal beam obtained in the additional section of the same type of fiber that ensures perfect matching between the seed and the Stokes beams. Over 40% of the wavelength conversion efficiency in the FWM process was obtained using a fiber length shorter than 1 m.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Our study investigated the partially degenerate intermodal four-wave mixing (IM-FWM) process in nonlinear multimode optical fibers with strain-induced birefringence. The difference in the refractive ...index along the two orthogonal directions was due to the photoelastic effect that occurred when the fiber under test (FUT) was subjected to uniformly applied diameter stress caused by winding on a cylinder of a given diameter. Our work analyzed how the nonlinear frequency conversion and the output modal field profiles depended on the degree of birefringence in FUT. The experimental results significantly affected the order of the excited moduli in fiber sections characterized by different amounts of birefringence. We also checked the efficiency of the FWM process for different polarizations of the pump beam to determine those for which the FWM process was most effective for the 532 nm sub-nanosecond pulses. More than 30% conversion efficiency was obtained for the FUTs with a length of tens of centimeters.
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In this paper, a highly-sensitive distributed shape sensor based on a multicore fiber (MCF) and phase-sensitive optical time-domain reflectometry (φ-OTDR) is proposed and experimentally demonstrated. ...The implemented system features a high strain sensitivity (down to ∼0.3 µɛ) over a 24 m-long MCF with a spatial resolution of 10 cm. The results demonstrate good repeatability of the relative fiber curvature and bend orientation measurements. Changes in the fiber shape are successfully retrieved, showing detectable displacements of the free moving fiber end as small as 50 µm over a 60 cm-long fiber. In addition, the proposed technique overcomes cross-sensitivity issues between strain and temperature. To the best of our knowledge, the results presented in this work provide the first demonstration of distributed shape sensing based on φ-OTDR using MCFs. This high-sensitivity technique proves to be a promising approach for a wide range of new applications such as dynamic, long distance and three-dimensional distributed shape sensing.
Optical fibre carbon dioxide (CO₂) sensors are reported in this article. The principle of operation of the sensors relies on the absorption of light transmitted through the fibre by a silica gel ...coating containing active dyes, including methyl red, thymol blue and phenol red. Stability of the sensor has been investigated for the first time for an absorption based CO₂ optical fiber sensor. Influence of the silica gel coating thickness on the sensitivity and response time has also been studied. The impact of temperature and humidity on the sensor performance has been examined too. Response times of reported sensors are very short and reach 2-3 s, whereas the sensitivity of the sensor ranges from 3 to 10 for different coating thicknesses. Reported parameters make the sensor suitable for indoor and industrial use.
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In this work, a compact all-fiber bend sensor based on a dual-core microstructured optical fiber has been manufactured and characterized. The sensor relies on the unbalanced Michelson interferometric ...technique realized by attaching a piece of silica fiber to one of the fiber cores acting as the unbalancing element. Three probes with different lengths of the unbalancing element have been experimentally tested for sensitivity tailoring analysis. Additionally, a theoretical model has been developed for comparison and verification of the results. Good linear behavior of the spectral shift with bend has been measured and it has been proven that the sensitivity of the sensor depends on the length of the unbalancing element and the orientation of the cores. Higher sensitivities are achieved for shorter lengths of the unbalancing element and orientation of the core axis parallel to the bend direction. The highest sensitivity reported is 9.97 pm/µm for the case of 34 µm of unbalancing element and orientation of 0 degrees.
We report on a bendable photonic crystal fiber for short pulse high power fiber laser applications. This fiber uses a double lattice structure and enables single mode operation with a very large mode ...area that reaches 1454 µm² when the fiber is kept straight and 655 µm² in the fiber bent around a 10 cm radius. Single mode operation is enforced by the very large bending loss in excess of 50 dB/m experienced by the higher order modes, whilst bending loss for the fundamental mode is smaller than 0.01 dB/m. We outline the principles of our fiber design and we explore the guiding properties of the fiber.
An optical fiber interferometric microprobe for detection of specific proteins is presented in this paper. The microprobe is an all-fiber device, which is based on Michelson interferometer ...configuration, which allows for detection of protein antigens in an analyzed solution thanks to antibodies immobilized on the sensor surface. The interferometer is made of dual core fiber and has a precisely formed arm length difference, achieved by splicing a fragment of polarization maintaining fiber to one of the cores. An all-fiber configuration of the sensor decreases substantially cross-sensitivities to temperature and deformation in comparison to other optical fiber interferometers. Reported sensor has a sensing region on the tip of the interferometer and therefore may be used for point measurements in medicine. The immunosensor and optical measuring system are designed to utilize the most common broadband light sources that operate at a central wavelength of 1.55 µm. The results show that it is possible to detect a protein antigen present in a solution by using an all-fiber interferometer coated with specific antibodies. The resulting peak shift can reaches 0.6 nm, which is sufficient to be measured by an optical spectrum analyzer or a spectrometer. A model allowing for estimation of the value of lower limit of detection for such sensors has been elaborated. The elaborated detection system may act as a framework for detection of various antigens and thus it can find future applications in medical diagnostics.
•A compact interferometric microprobe with sensing tip was made of a dual-core fiber.•The reported interferometer is made by fusion splicing.•The interferometer exhibits reduced cross-sensitivities.•The tip of the sensor was coated with specific antibodies.•Anti-IgG proteins were detected in a solution.
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•Few-Mode Fibers (FMF) and Multimode Fibers (MMF) can be used in Phase-Sensitive OTDR (PS-OTDR) to decrease influence of the nonlinear effects.•Application of FMFs and MMFs in PS-OTDR allows to ...increase signal-to-noise ratio at distances up to 50 km.•FMF supports longer propagation distances than MMF due to the lower attenuation.•FMF and MMF application is compatible with other techniques of OTDR range extension.
We discuss the possible advantages of using few-mode and multimode fibers in coherent optical time-domain reflectometry sensing systems. We show that the application of few-mode and multimode fibers decreases nonlinear effects and impedes modulation instability. In comparison to standard single-mode optical fiber, few-mode and multimode fibers may help to increase signal power at the receiver. We also show that few-mode fibers may potentially increase sensing distance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We report on the design of a novel flexible very large mode area photonic crystal fibre for short pulse high peak power fibre laser and beam delivery applications. This fibre has an extremely large ...mode area exceeding 2500 microm(2) when kept straight and over 1000 microm(2) when bent over a 10 cm radius at a wavelength of 1064 nm. In addition our fibre exhibits very small fundamental mode bending loss below 10(-2) dB/m. The large difference between the propagation loss levels of fundamental and higher order modes forces efficient single-mode guidance in the fibre core while bent. This allows using the fibre to build compact high power laser systems. The paper further explores the major features of this fibre including: the dependence of the mode field area on the fibre core shape, the influence of the bending radius and of the bending direction as well as the impact of manufacturing tolerances on the fibre specifications.
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