The invention relates to a watch, in particular a wristwatch, comprising an electro-optical converter, an opto-electrical converter, a light wave guide, a useful signal generating device and a watch display device. The electro-optical converter is formed to generate and feed a clocked light signal into the light wave guide. A reflector is arranged at a reflector end of the light wave guide, through which the clocked light signal is reflectable back into the light wave guide. A decoupling device is arranged at a feeding end of the light wave guide and is formed to decouple the reflected clocked light signal into the opto-electrical converter. The opto-electrical converter is formed to generate an electrical signal based on the reflected clocked light signal. The watch comprises an electrical signal path between the opto-electrical converter and the electro-optical converter, wherein the electro-optical converter is controllable for generating the clocked light signal based on the electrical signal of the opto-electrical converter. The useful signal generating device is formed to generate a useful signal based on a frequency of the electrical signal, wherein the watch display device is formed to display the time based on the useful signal.