DIRECTIONS FOR IMPROVING THE QUALITY PARAMETERS OF TRANSMISSION SYSTEMS ON MODERN DWDM COMMUNICATION NETWORKS

Abstract

The paper presents directions for the further development of modern fiber-optic co   mmunication. The need for a constant increase in the information-throughput capacity of optical communication lines, associated with the increase in the information-throughput capacity of an optical fiber, is noted. The principles of DWDM technology, which allows to meet the growing needs for increasing this capacity, are considered. The need for a high number of regenerators on optical transmission lines for the introduction of DWDM technology was noted, and a conclusion was drawn about the expediency of using broadband optical amplifiers instead of regenerators, which amplify the optical group signal in a purely optical form, without converting it into electrical form.

In addition, the work presents the problems that arise when using optical amplifiers, in particular, the generation of quantum noise during the operation of the amplifier, which worsens the signal-to-noise ratio in the line and, in the final case, at the input of the receiving device.

The paper also gives other factors that worsen the signal/noise ratio at the input of the optical receiving device. Among such factors are optical noise, which occurs in an optical fiber due to Rayleigh scattering.

The effect on the signal/noise ratio of the optical signal modulation mode at the output of the laser source is presented. It is shown that an increase in the damping ratio at the output of the modulator and a corresponding increase in the modulation depth increase the signal-to-noise ratio at the output of the optical amplifier.

The most common types of modulators for high-speed DWDM technologies are considered. These are Mach–Zehnder modulators and electroabsorption modulators, both of which provide the required baud rate for STM-64 or higher technologies.

The advantages of a Mach-Zehnder-based modulator are shown, as it can provide a better damping ratio due to the selection of the control voltage.

Calculations of the signal/noise ratio at the output of the optical amplifier depending on the depth of the optical modulation and different values of the noise factor of the optical amplifier have been carried out and provided. It is shown that increasing the modulation depth and reducing the noise factor significantly improves the signal-to-noise ratio at the output of the amplifier. At the same time, the noise coefficient can be reduced by choosing the wavelength of the pumping radiation.

Conclusions have been made regarding the features of the application of various types of optical amplifiers in communication networks.