Fischer is the pioneer in the study of sugars. As these substances are optically active, Fischer invented a mode of representation and a nomenclature still widely used today.
The nomenclature R and S of enantiomers dates only from 1966. Emil Fischer had his own method to describe these two enantiomers:
Fischer projection: OH or NH2 on the right side : enantiomer D OH or NH2 on the left side : enantiomer L
D and L don't correspond in any way to d and l respectively + and - characterizing the rotation of polarized light!
Check yourself (see below) that this is the enantiomer R . It was found (you can not predict!) that this substance rotates the plane of polarization of polarized light to the right, so that's D (+) - glyceraldehyde R (+) - 2,3-dihydroxypropanal