Fibre optics experiment. Moulded gelatin dessert (known as jelly or Jell-O, centre) transmitting a red light beam. A red laser beam is being transmitted through and out (centre left) of the mould by a process known as total internal reflection. Due to the reflective property of the gelatine, the beam is able to travel the length of the mould even though it is bent, without loss of intensity. Total internal reflection is the physical property that is utilized in the transmission of digital data down optical fibres.