In some examples, a mechanical transfer ferrule based optical switch may include an optical fiber tube unit connectable to an end of an optical fiber. The optical fiber tube unit may include a lens to transmit light through the optical fiber. An optical fiber tube unit positioning assembly may include an optical fiber tube unit support detachably connectable to the optical fiber tube unit, and an optical fiber tube unit guide to operatively position the optical fiber tube unit support relative to a multi-fiber connector. The optical fiber tube unit guide may align the optical fiber tube unit and the lens to a specified lens of the multi-fiber connector, and connect the optical fiber to a specified optical fiber channel.