Question

The wavelength of the carrier waves in a modern optical fiber communication network is close to:
A) 600 nm
B) 900 nm
C) 2400 nm
D) 1500 nm

Answer 1

Hint : Light travels in a modern optical fiber through total internal reflections from the surface of the optical fiber cables. The wavelength of the light depends on the refractive index of the medium in the optical fiber and the surrounding medium.

Complete step by step answer
An optical fiber is a flexible, transparent fiber which has a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to transmit light between the two ends of the fiber and are used widely in fiber-optic communications. This is because optical fibers enable transmission over longer distances and at higher bandwidths than electrical cables over long distances.
The fiber optical cable uses the application of total internal reflection of light as mentioned in the hint. The fibers are designed such that they facilitate the propagation of light along with the optical fiber depending on the requirement of power and distance of transmission by the total internal reflection of the light rays. Different kinds of transmission distances will utilize different kinds of cables.
To minimize attenuation which is losses due to interactions with different mediums, the wavelength of the light is chosen to be 1500 nm which corresponds to option (D).

Note
The wavelength mentioned above is for a typical single-mode fiber used for telecommunications. Other kinds of cables made from different materials will operate at different wavelengths since the angle for total internal reflection will be different for different materials. This will also influence the time taken by the signal to travel a certain distance.