The article explores the concept of deuterium-deuterium (DD) fusion as a potential energy source for advanced extraterrestrial civilizations. The study suggests that the prolonged use of DD fusion could lead to a depletion of deuterium in planetary water sources, creating anomalous deuterium-hydrogen (D/H) ratios that could serve as technosignatures. These anomalies, below the natural values found in astronomical objects, are proposed to persist over eons, making them potential indicators of long-lived technological societies. The research delves into the implications of various energy consumption levels, ocean sizes, and initial D/H values on the timescales for reaching anomalously low D/H ratios. Additionally, the article discusses the potential use of different wavelengths, such as O-D stretching and near-infrared imaging, to detect D/H anomalies in atmospheric water vapor on Earth-like exoplanets. By proposing the application of spectroscopy and imaging technologies for this purpose, the study opens up possibilities for identifying technosignatures in exoplanetary water sources.