• Since the core and cladding have different indices of refraction hence they have different attenuation coefficients α1 and α2
  • For step index fiber, the loss for a mode order (v, m) is given by,


                                                                            … (2.5.1)

For low-order modes, the expression reduced to


                                                                         … (2.5.2)

where,  and  are fractional powers.

  • For graded index fiber, loss at radial distance is expressed as,


                                                             … (2.5.3)

The loss for a given mode is expressed by,


                                                                            … (2.5.4)

where, P(r) is power density of that model at radial distance r.