V number of fiber or normalized frequency of fiber :

• V number of fiber or normalized frequency of fiber is used to find the number of propagating modes through the fiber.

   V = 2∏a(N.A)

λ

• In step index fiber number of modes propagating through the fiber = V2/2                                                                  

• Taking the two possible polarizations, total number of possible modes propagating through the fiber = V2*2/2 = V2