Large-core Multimode Optical Fiber Research Articles

Magnetically-sensitive nanodiamond thin-films on glass fibers

By assembling 140 nm-sized fluorescent nanodiamonds (FNDs) in a thin-film on (3-aminopropyl) triethoxysilane functionalized glass surface, we prepare magnetically-sensitive FND-fiber probes for endoscopy. The obtained FND layers show good uniformity over large surfaces and are characterized using confocal, fluorescence, and atomic force microscopes. Further, FNDs are assembled on single large-core multimode optical fibers and imaging fiber bundles end face to detect optically detectable magnetic resonance (ODMR) signals. The ODMR signals are recorded through the fiber’s far end in magnetic fields between 0 to 2.5 mT. A multi-channel sensor is demonstrated with the capability of parallel-in-time mapping and instantaneous readout from individual pixel and enabling magnetic mapping at high spatial resolution. Results of this study are promising for early stage detection in bio-diagnostic applications.

Disordered Anderson Localization Optical Fibers for Image Transport—A Review

Disordered optical fibers show novel waveguiding properties, enabled by the transverse Anderson localization of light, and are used for image transport. The strong transverse scattering from the transversely disordered refractive index structure results in transversely confined modes that can freely propagate in the longitudinal direction. In some sense, an Anderson localization disordered fiber behave like a large-core multimode optical fiber, with the advantage, that most modes are highly localized in the transverse plane, so any point in the cross section of the fiber can be used for localized beam transport. This property has been used for high-quality transportation of intensity patterns and images in these optical fibers. This review covers the basics and the history of the transverse Anderson localization in disordered optical fibers and captures the recent progress in imaging applications using these optical fibers.

Design of an Optical Fibre-based Receiver System for Atmospheric Sensing Lidar

In this paper we report on the design of an optical fiber-based light receiver which is meant for replacing the conventional beam steering secondary mirror of the Newtonian telescope of a biaxial Raman lidar. The influence of using optical fibre, acting as an aperture stop of constant diameter on the geometrical compression form factor; the transitional altitude and the resulting blur disk diameter have been determined. The viability of using a commercially available optical fibre as a receiver and the associated trade-offs have been discussed. A hot-fused fibre bundle-based receiver is proposed as a potential alternative for low altitude profiling to be enabled. These theoretical investigations have formed the basis for our current experimental work aimed at the development of all fibre-based reconfigurable beam delivery systems for mobile lidars. Full Text: PDF References A.M. Melesse et al., "Remote Sensing Sensors and Applications in Environmental Resources Mapping and Modelling", Sensors 51, 3209 (2007). CrossRef P. Wang et al., "A macrobending singlemode fiber refractive index sensor for low refractive index liquids", Phot. Lett Poland 2, 67 (2010). CrossRef J.R. Jenness et al., "Design of a lidar receiver with fiber-optic output", Appl. Optics 36, 4278 (1997). CrossRef J.V. Hey et al., "Determination of overlap in lidar systems", Appl. Optics 50, 5791 (2011). CrossRef K. Stelmaszczyk et al., "Analytical function for lidar geometrical compression form-factor calculations", Appl. Optics 44, 1323 (2005). CrossRef A.A.P. Boechat et al., "Bend loss in large core multimode optical fiber beam delivery systems", Appl. Optics 30, 321 (1991). CrossRef http://www.schott.com/china/chinese/download/284345_fo_light_it_right_e_without_tecspec.pdf DirectLink https://www.thorlabs.com/thorproduct.cfm?partnumber=APCH1500 DirectLink

High-Power Fiber Lasers and Amplifiers Based on Multimode Interference

In this paper, high-power fiber lasers and amplifiers based on multimode interference (MMI) in active large-core multimode optical fibers are proposed and their properties are investigated. Experimental results and simulations indicate that such fiber lasers and amplifiers are promising candidates for high-power miniature solid-state lasers. Utilization of the MMI leads to remarkable spectral and spatial features of fiber lasers and amplifiers such as generation of high-power diffraction-free beams.

Detailed investigation of self-imaging in largecore multimode optical fibers for application in fiber lasers and amplifiers

Properties of the self-imaging effect based on multimode interference (MMI) in large-core passive optical fibers are investigated and analyzed in detail, with the purpose of using multimode active fibers for high power single-transverse-mode emission. Although perfect self-imaging of the input field from a standard single-mode fiber (SMF-28) in a multimode fiber becomes practically impossible as its core diameter is larger than 50 microm, a quasi-reproduction of the input field occurs when the phase difference between the excited modes and the peak mode inside the multimode fiber is very small. Our simulation and experimental results indicate that, if the length of the multimode fiber segment can be controlled accurately, reproduction of the input field with a self-imaging quality factor larger than 0.9 can be obtained. In this case, a low-loss hybrid fiber cavity composed of a SMF-28 segment and a very-large-core active multimode fiber segment can be built. It is also found that for the hybrid fiber cavity, increasing the mode-field diameter of the single-mode fiber improves both the self-imaging quality and the tolerance on the required length accuracy of the multimode fiber segment. Moreover, in this paper key parameters for the design of MMI-based fiber devices are defined and their corresponding values are provided for multimode fibers with core diameters of 50 microm and 105 microm.

Degradation of beam quality and depolarization of the laser beam in a step-index multimode optical fiber

The characteristics of a laser beam are altered during propagating through large-core multimode optical fibers. The distribution of modes excited by the input laser beam is modified by means of mode coupling on transmission through the fiber, leading to the degradation of beam quality and the depolarization of the delivered beam. The relationship between the beam quality factor ( M 2) of output beam from a large-core multimode fiber and the fiber length, as well as the relationship between the degree of polarization ( V) of output beam from such a fiber and the fiber length, are introduced in this paper. When a laser beam was well launched into a large-core step-index multimode fiber, M 2 of the output beam was a compound tanh function of the fiber length. A linear polarization beam that well launched into such fiber suffered depolarization. The V of the output beam was an exponent function of fiber length. And the misalignment between beam axis and fiber axis made the beam quality degrade faster but made no difference of the utmost M 2 in the aligned and misaligned conditions. Also, the misalignment condition made the polarization of output beam degrade faster.

Finite-element modal analysis of large-core multimode optical fibers: erratum

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text Masashi Eguchi and Suguru Horinouchi, "Finite-element modal analysis of large-core multimode optical fibers: erratum," Appl. Opt. 43, 3158-3158 (2004) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

All propagation modes of large-core multimode optical fibers with an arbitrary core profile.

Plastic optical fibers are typical large-core multimode optical fibers. High-bandwidth graded-index plastic optical fibers, which support a great number of propagation modes compared with conventional silica-glass multimode optical fibers, were developed in the 1990s. However, because they support a great number of propagation modes, their modal analyses have been limited to the WKB analysis. We obtain all the propagation modes of a convex-index large-core multimode optical fiber by use of the finite-element method, which has a strong advantage for arbitrary core profiles.

Finite-element modal analysis of large-core multimode optical fibers.

Plastic optical fibers that are a typical large-core multimode optical fiber support a great number of modes compared with conventional silica-glass multimode optical fibers. So far the WKB method hasbeen used for most of the modal analyses of these fibers because of a great number of guided modes. We describe the accurate eigenmodal analysis of large-core multimode optical fibers with the finite-element method (FEM) and compute the propagation constants of all LP modes. In addition, the FEM has a strong advantage for arbitrary core profiles whereas the WKB method is not suitable fornonmonotonic profiles. To demonstrate the advantage, we apply the FEM to the fiber having sinusoidal fluctuations.

Laser shock processing with 20 MW laser pulses delivered by optical fibers

A large-core multi mode optical fiber is used to deliver 100 mJ, 5 ns laser pulses produced by a frequency-doubled Nd:YAG laser over a distance of several meters. No damage is observed neither inside the fiber nor at its surface. The transmitted pulses are focused to a diameter of 700 μ m onto a water-immersed type 304 stainless steel sample for laser shock processing. With a pulse density of 10000 pulses/cm 2 , a compressive residual surface stress is achieved. The affected depth is almost 900 μ m, the maximum compressive stress −700 MPa.

Delivery of 10-MW Nd:YAG laser pulses by large-core optical fibers: dependence of the laser-intensity profile on beam propagation

A large-core multimode optical fiber of a few meters length is studied as a 10-MW beam delivery system for a 15-ns pulsed Nd:YAG laser. A laser-to-fiber vacuum coupler is used to inhibit air breakdown and reduce the probability of dielectric breakdown on the fiber front surface. Laser-induced damage inside the fiber core is observed behind the fiber front surface. An explanation based on a high power density is illustrated by a ray trace. Damaged spots and measurements of fiber output energies are reported for two laser beam distributions: a flat-hat type and a near-Gaussian type. Experiments have been performed to deliver a 100-pulse mean energy between 100 and 230 mJ without catastrophic damage.

Bend loss in large core multimode optical fiber beam delivery systems

We present results of an experimental investigation of the optical losses produced by bending large core optical fibers, typical of those used in power beam delivery systems. Experiments have been conducted over a range of core diameters for both plastic clad silica and all-silica fibers as a function of bend radius. A theoretical model has been developed for predicting the magnitude of the bend loss, and agreement was obtained with the experimental results. The study thus yields design information for fiber beam delivery systems.