Tapered fiber regions. Diagram of a tapered fiber. Region A is the unstreched fiber, where the fiber remains the original unperturbed diameter d
0. Region B is the taper transition over which the unstreched diameter is adiabatically reduced to the minimum diameter d maintained throughout region C, which is known as the taper waist. A constant hot-zone L is assumed such that the taper transition has an exponential profile.