Coupling efficiency calculations on an integrated l.e.d./sphere-lens source for optical fibres

The letter reports some numerical calculations on the power accepted by an optical fibre (n.a. = 0.16, radius 42.5 ¿m) from an l.e.d. with an integrated hemispherical lens. It is shown that the launched power is much higher than in simple close coupling of the source, and that there is an optimum radius of 2¿3 ¿m for the source.