**1. Introduction**

Gravitational waves are ripples in the curvature of spacetime that propagate like waves, traveling outward from the source; they travel at the speed of light (299,792,458 m/s) and squeeze and stretch anything in their path as they pass. Do not confuse it with gravity waves that are waves generated when the force of gravity in a fluid medium or, when it is the case, at the interface between two different media, tries to restore equilibrium, as an example of these waves there are the wind waves on the interface between the atmosphere and the ocean.

Predicted in 1916 [1, 2] by Albert Einstein based on his theory of general relativity, [3] and detected in 2015, gravitational waves transport energy in the form of gravitational radiation, oscillation of spacetime itself. This theory predicts that the presence of mass causes spacetime to warp. When massive objects move around themselves, this curvature is altered, sending ripples of gravitation out of the universe carrying unbelievable amounts of energy. As these sources are very distant by the time, these disturbances catch up with us; they are almost imperceptible because they are weaker and gravitational waves interact very weakly with matter. Because of that, it was only a century after Einstein's prediction that scientists developed a sensitive enough detector—a Laser Interferometer Gravitational-Wave Detector, some kilometers long interferometer and were able to confirm the existence of gravitational waves [4].

The existence of gravitational waves is also a consequence of the Lorentz covariance of general relativity since it brings the concept of a finite speed of propagation of gravity. Gravitational waves did not exist in the Newtonian theory of gravitation, which postulates that physical interactions propagate at infinite speed.

There was already indirect evidence of gravitational waves before its first direct detection. Measurements of the Hulse-Taylor binary system suggested that gravitational waves were more than a hypothetical concept. This system is one of the potential sources of detectable gravitational waves. These potential sources include binary compact star systems composed of white dwarfs, neutron stars, and black holes.

One way of thinking about gravitational radiation is as the messenger that carries information about changes in gravitational fields that attract one thing to another [5].

Several gravitational wave observatories (detectors) are under construction or in operation around the world [6]. In 2017, the Nobel Prize in Physics was awarded to Rainer Weiss, Kip Thorne, and Barry Barish for their role in detecting gravitational waves [7]. In these gravitational wave detectors and previous ones, the use of interferometry was essential for the operation of such a detector.
