The disclosure provides a light-transmissive glass halogen filament tube with a filament light source having a coil concentricity ratio of not greater than 20% disposed therein, the filament tube having a multi-layer optical interference coating deposited on the outer surface thereof that transmits visible radiation from about 400-750 nm and reflects infra red radiation from about 800-2500 nm back to the filament for re-absorption, the coated filament tube exhibiting an LPW gain of at least 26%.