How to calculate the foreign classics of optical fiber optic cables?

Foreign classics in optical fiber cables refer to the characteristics of the cable that determine its ability to transmit light. These characteristics include attenuation, dispersion, and polarization mode dispersion. Calculating the foreign classics of optical fiber cables is important in understanding the performance of the cable and ensuring that it meets the requirements for the intended application.

Attenuation:

Attenuation is the reduction in the strength of the light signal as it travels through the optical fiber cable. Attenuation is measured in decibels per kilometer (dB/km). The attenuation of the cable is determined by the properties of the fiber and the manufacturing process. The main factors that affect attenuation include the purity of the fiber, the uniformity of the fiber diameter, and the presence of impurities or defects in the fiber.

The attenuation of the cable can be calculated using the following formula:

Attenuation = 10 x log10(P1/P2) / L

where P1 is the input power, P2 is the output power, and L is the length of the cable.

The attenuation of the cable can also be measured using an optical time-domain reflectometer (OTDR). An OTDR sends a pulse of light into the cable and measures the reflected light at different points along the cable. The attenuation can be calculated by analyzing the changes in the intensity of the reflected light.

Dispersion:

Dispersion is the spreading out of the light signal as it travels through the optical fiber cable. Dispersion is caused by differences in the speed of light in different parts of the fiber. There are two main types of dispersion: chromatic dispersion and modal dispersion.

Chromatic dispersion is caused by differences in the speed of light at different wavelengths. Chromatic dispersion limits the bandwidth of the cable and can cause distortion in the signal. Chromatic dispersion is measured in picoseconds per kilometer per nanometer (ps/km/nm).

Modal dispersion is caused by differences in the propagation time of different modes of light in the fiber. Modal dispersion limits the distance that the cable can transmit a signal without the need for regeneration. Modal dispersion is measured in picoseconds per kilometer (ps/km).

The dispersion of the cable can be calculated using the following formula:

Dispersion = D x L

where D is the dispersion coefficient and L is the length of the cable.

The dispersion coefficient is a measure of the dispersion per unit length of the fiber. The dispersion coefficient can be calculated using the following formula:

D = (n2 - n1) / (2 x pi x c x n1 x n1 x lambda)

where n1 is the refractive index of the core, n2 is the refractive index of the cladding, c is the speed of light in a vacuum, and lambda is the wavelength of the light.

Polarization mode dispersion:

Polarization mode dispersion (PMD) is caused by differences in the propagation time of the two polarization modes of light in the fiber. PMD limits the distance that the cable can transmit a signal without the need for regeneration. PMD is measured in picoseconds per kilometer (ps/km).