## 2 Laser Optimized Multimode Optical Fibers with 100-\(\upmu\)m Core Diameter  
Laser-excited optical pulse propagation over MMF with large core (in comparison with standard telecommunication single-mode optical fibers) differs from a multimode regime by the appearance of the DMD effect [1; 2; 3; 4; 5; 6] due to here optical signal is transferred by not the almost all guided modes that satisfy to cut-off conditions but only the limited number of them. The main reason of DMD appearance is the launch of laser-excited optical emission with small spot size to MMF with large core diameter. This great distinction leads to the excitation of just a limited number of particular order modes differing by their delays, while during the propagation in MMF, the amplitudes of these selected mode components, containing in the optical signal, are non-equal. It is mainly defined by the launching conditions of the laser-excited optical signal into the optical fiber core end, by using the typical fiber optic adaptor with uncontrolled radial or angular misalignments, or by utilizing the special device like matching optical fiber or lens system, etc., providing centralized connection or vice versa, pre-set precision angular or radial misalignment. During laser-excited optical signal propagation over MMF, some new guided modes may be excited by mode mixing and power diffusion (e.g., mode coupling effects) occurring due to optical fiber irregularities and micro-/macro-bends. However their number is also limited, as well as their amplitudes also may be weak and neglected with normalized values to less 0.1. Therefore, at the transmitter end of the fiber optic link, the optical pulse contains several modes with non-equal amplitudes and differing mode delays (e.g., mode group velocities), while at the receiver end it comes with spread of both amplitudes and delays relative each other that causes to pulse splitting and may strongly distort it: from the initial typical quasi-Gaussian to inappropriate \"glove\" form at the receiver end. Moreover, for each particular \"laser-MMF\" couple DMD may strong differ from other. It depends on random factors of launching conditions and launching uncertainty provided by the variations of sources, connections, and fiber parameters. That is why DMD is a main issue for short-range multi-Gigabit optical networks based on MMFs. Unlike known solutions (detailed overview is presented in the earlier on published papers [10; 11; 12] and monograph [13]), we proposed to take into account the following outlined factors during the design refractive index profile for LOMF with extremely large core diameter [10; 11; 12]:  
1. Real and approved commercially available LOMFs of Cat. OM2+...OM5 parameters (geometry, refractive index profile, etc. ), taken from the measurement reports/data sheets/specifications, should be used initially, but neither parameters of model optical fibers with the ideal graded refractive index profiles described by just one or a set of simple power-law \(\alpha\)-functions nor the first generation MMFs of Cat. OM1 and OM2, should be targeted to only multimode regime;
2. The development or modification of a fiber structure/refractive index profile during each step of optimization procedure has to be based on results of comparison between the desired DMD diagram and DMD diagram, obtained in the previous iteration;
3. The laser source type and its parameters--especially initial number and order of transverse modes containing in the laser-generated emission as well as the launching conditions--should be taken into account;
4. DMD should be decreased not only at particular wavelengths but over the desired spectral range (for example, conventional telecommunication \"O\"-band with a reference wavelength \(\lambda\) = 1300-1310 nm). Proposed method for design of special graded refractive index profile, providing of selected guided mode delay equalization around some reference mode delay value \(t_{REF}\), is described in details in the earlier on published papers [10; 11; 12].