Firstly, infra-red light, like visible light, is restricted to line of sight operations (Figure 4a), although the use of diffuse propagation can reduce this restriction by allowing the beam to bounce off passive reflective surfaces.
(infra-red light; is restricted; to line of sight operations) (the use of diffuse propagation; can reduce; this restriction)
infra-red light the use of diffuse propagation
is restricted can reduce
to line of sight operations
this restriction