Abstract: An adapter for receiving optical fiber connectors, of the type having an inner part suitable for receiving an internal connector carrying an internal optical fiber having an end ferrule, and having an outer part suitable for receiving an external connector having an external optical fiber with an end ferrule, is made suitable for use with different external connectors by having the outer part readily separable from the inner part. The parts have complementary engaging surfaces and cooperating engaging means which lock the two parts together upon relative rotation of one of the parts relative to the other through about a right angle. The usual alignment sleeve is carried by the outer part, and when this part has been separated from the inner part the internal fiber ferrule is accessible for cleaning.