An example system includes a fuel tank, fittings mounted through a wall of the fuel tank, and optical sensors positioned within the fittings. A respective optical sensor includes a first pressure sensing end inserted through a fitting and internally into the fuel tank and a second end extending externally from the fuel tank. The system also includes an optical fiber bundle mounted external to the fuel tank, and having an optical fiber connected to each of the plurality of optical sensors for guiding light to each of the plurality of optical sensors.