Corrections to jwbensley <at> gmail <dot> com

Default c value (meters per second): 299792458
Refractive index of light in air is 1.
Typical SMF radius 4.5µm, typical MMF is 32.75µm or 26µm.
Typical wavelength for SMF in µm's is 1.31µm or 1.55µm and for MMF 0.85µm.
MMF has a much higher Numerical Aperture which helps to maintain total internal reflection for all modes of light entering the fibre.

Fibre Properties

Refractive Index (N1 is always > N2)
N1 (Core Index)
N2 (Cladding Index)
NA = √(N12)-(N22)
Critical Angle
Acceptance Angle

V Number
λ [µm] (Wavelength)
a [µm] (Core Radius)
V = (2πa/λ)NA
Single Mode <= 2.405
Number of modes:

Speed of Light

Speed of Light in Core (meters/s)
c (meters/s)
N1 (Core Refractive Index)
v = c / N1
Refractive Index of Core
c (meters/s)
v (speed through core, meters/s)
N1 = c / v

Fibre Latency

Latency (ms)
v (speed through core, meters/s)
d (Distance Km)
l = d / (v/1000)