Abstract: A rotating coupling for transmitting optical signals across an optical fiber juncture is described which in one preferred embodiment comprises a body member having an axial passageway sized for coaxially receiving a first rotatable optical fiber member and a second optical fiber member in generally axial abutting relationship, the passageway defining a cylindrically shaped first enlargement near a first end of the body member and a generally conically shaped second enlargement axially adjacent the first enlargement, a lubricated rotatable bearing member disposed within the first and second enlargements and having a central bore for receiving the first optical fiber member for rotation therewith and having outer shape defined generally by the first and second enlargements, an axial recess in the second end of the body member for receiving an axially resilient spring for holding the second optical fiber member in axial alignment with the first optical fiber member, and a threaded end cap for the second end of t

Abstract: A photovoltaic solar cell system is provided which comprises a hollow light tube of substantially conventional design of optically transparent material, generally square cross section and preselected length and width and having on the outer surfaces thereof longitudinally extending triangularly shaped grooves defining a plurality of ridges having triangular cross section along the tube length, each ridge having a 90.degree. apex angle and surfaces along its length defining a 45.degree. angle with the inner surfaces of the tube; light concentrating optics are operatively connected to one end of the tube for directing light into the tube; and a plurality of solar cells are disposed on the outer surfaces of the tube in a rectangular array of size corresponding to tube size with the photoactive surfaces of the cells facing inwardly of the tube. The tube may be hermetically sealed and either evacuated or filled with inert gas in certain applications.