Given that, wavelength, λ=800‌nm speed of light, c=3×108m∕s Then, frequency, f=
c
λ
Substituting the values, we get Source frequency, f=
3×104
800×10−9
‌Hz =375×1014‌Hz It is said in the question that only 1% of source frequency is available as signal bandwidth. ∴ Total available signal bandwidth =1% of 375×1014 =
1
100
×3.75×1014‌Hz=3.75×1012‌Hz Given that, the frequency bandwidth of one signal =6‌MHz=6×106‌Hz Hence, the number of channels =