An optical path can be created through optically challenging media. Light can transmit over the optical path between an end of an optical waveguide and a point displaced from the end. A fluid that scatters or absorbs light, generates interference, or otherwise poses optical challenges can be disposed between the waveguide end and the point. The optically challenging fluid can comprise blood, turbid and/or opaque fluid, absorbing liquids, or other liquid or fluid presenting transmission issues, for example. An optical path can be formed between the end and the point to facilitate transmitting light through the optically challenging fluid. In certain examples, the optical path can comprise a waveguide formed of fluids emitted into the optically challenging fluid, a gas injected into the optically challenging fluid, or an expandable structure, such as a balloon filled with substantially transparent liquid or gas.
