An elongated hollow optical waveguide (1) is described, as can be used in particular in a photobioreactor for supplying phototrophic organisms both with light and with nutrients. The optical waveguide (1) has a casing (3) made from transparent plastic, which surrounds a hollow core (5). The hollow core has a diameter of at least 1 mm, preferably at least 3 mm or at least 1 cm. A plurality of openings (7) with a diameter of at least 0.5 mm, preferably at least 1 mm, is constructed in the casing (3). Light can propagate through the transparent casing and preferably exit laterally (19) along the entire optical waveguide (1). Nutrients (15) can be conveyed through the hollow core (5) into the interior of the photobioreactor. Conversely, portions of the solution, to which organisms have been added, can also be sucked through the hollow core (5), for example in order to analyze the same.