ATTENUATION and WINDOWS For Attenuation we mean the loss in power that the luminous energy suffers in going through an absorbing means as the fiber optics. It depends on the wave length and on the type of material the fiber is made of (plastic or glass).
Type values are fractions of dB/km for glass fibers, of some db/m for plastic fibers.
Other losses, not intrinsic to the nature of the fiber, are determined by the junctions among more sections of fiber and by the bending modality of the optical cable (Bending Losses).
Fiber optics are commonly used in 3 areas of wave length, called Windows:
Att.(dB) = 10 · log(POUT/PIN)
Ist window
between 800 and 900 nm (typically 820 or 850 nm) IInd window around 1330 nm IIIrd window around 1550 nm.
Attenuation bend in glass fiber Graded-Index
On the same wave lengths sources and detectors will have to have the maximum power and sensitivity.