What makes the Van den Hul OPTOCOUPLER Mk II special is the fact that both ends of the single fiber are shaped in the form of a convex (spherical) lens which has many advantages; The OPTOCOUPLER Mk IIs lens shaped input and output surfaces produce an extra focusing of the light beam. Light entering the cable at an angle is focused and therefore undergoes 50% less wall reflections per unit length inside the fiber (i.e. the light path is shorter).This not only reduces the loss of light intensity (attenuation) (even when the cable is being bent) but also the time difference of travel between the light rays traversing the fiber at various angles (so-called modal dispersion) is much reduced; A pulse of light traversing the optical fiber therefore undergoes less time-smear and this in effect reduces the amount of jitter distortion experienced at your D/A converter.The OPTOCOUPLER Mk IIs convex shaped fiber ends furthermore bring about a better controlled fiber top surface contacting the optical transmitter and receiver-end. In this way optical insertion losses are reduced to a minimum.