Laser Diode Fiber Coupling

. The edge emitting diodes have emission pattern full width at half maximum (FWHM) at 30 – 50° in the plane perpendicular to active  area junction and FWHM of 5 – 10° in plane parallel to junction.
. As angular output distribution of laser is greater than fiber acceptance angle laser emitting area is much smaller than cross-section of fiber core, spherical/cylindrical lenses can be used employed for improving coupling efficiency.
. The coupling efficiency for a surface emitting LED as a function of emitting area diameter for a fiber with NA  0.20 and core radius a  25 μm is shown in Fig.  1.

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