The fiber should be________________ to avoid deterioration of the optical transmission characteristics resulting from mode-coupling-induced micro-bending.

Optoelectronics and Optical Communication 

The fiber should be________________ to avoid deterioration of the optical transmission characteristics resulting from mode-coupling-induced micro-bending.

a) Free from irregular external pressure 
b) Coupled with plastic 
c) Large in diameter 
d) Smooth and in a steady state

Answer : - Free from irregular external pressure