Abstract: Unidirectional and bidirectional fiber optic rotary joints are disclosed for coupling at least one optical signal across a rotary interface. The unidirectional joint includes a stator having a waveguide. A rotor is rotatable through a full 360.degree. revolution and is concentric to the stator. Light transmitters are positioned on a first circumference and connected to one of the stator and the rotor. Each of the transmitters emits an optical signal. Light receivers are positioned on a second circumference and connected to the other one of the stator and the rotor. Each of the transmitted optical signals is emitted tangentially into the waveguide and is reflected in short chordal lengths along the waveguide. Each optical signal is received by at least one of the second plurality of light receivers through the full 360.degree. revolution of the rotor. The number of light receivers is greater than the number of light transmitters. Certain receivers do not receive an optical signal during a portion of the 360.

Abstract: A single stage secondary oxygen concentrator for receiving a gas mixture from a first stage oxygen concentrator and a method of use therefor is disclosed. The concentrator includes a first carbon molecular sieve bed and a second carbon molecular sieve bed. A first inlet valve is connected to an inlet of the first carbon molecular sieve bed and a second inlet valve is connected to the inlet of the second carbon molecular sieve bed. A first product outlet valve is connected to the outlet of the first carbon molecular sieve bed and a second product outlet valve is connected to the product outlet of the carbon molecular sieve bed. The oxygen concentrator has control means for controlling a first cycle in which the first carbon molecular sieve bed is being charged with the gas mixture and the second carbon molecular sieve bed is being desorbed.