In a fiber splicing device, an adjustment apparatus for moving a first fiber-section perpendicular to its end face is designed such that it is composed of at least one piezo-actuator and a drive. After the splicing of the two fiber ends, the piezo-actuator is charged to a preset electrical voltage and the electrical voltage at the piezo-actuator is subsequently measured while the first carriage is moved away perpendicular to the fiber end face and is compared to the preset values. As a result thereof, the tensile stress acting on the fiber can be identified dependent on the movement of the first carriage, so that the drive can be arrested after a preset tensile testing stress has been reached.