Abstract: This invention provides an illuminating device characterized in that the device comprises a light-transmitting rod for transmitting the light incident on one end thereof toward the otehr end, a diffusion pattern formed on the outer peripheral surface of the rod by adhering a fine powder of high refractive index in the shape of a line extending continuously or discretely axially of the rod, and a transparent protective tube covering the peripheral surface of the rod with a circumferential clearance formed between the rod and the tube, the clearance between the rod and the protective tube being sealed off at opposite ends thereof.

Abstract: This invention provides a branch structure for a rod-type optical transmission line having a quartz rod core, characterized in that two quartz rod branch members bent to a substantially L-shaped form and having a circular cross section are combined together with the axes of longitudinal portions of the members in parallel and with the horizontal portions thereof bifurcated, the combined longitudinal portions being ground to a planar surface each at the opposed faces thereof so as to conjointly form a circular cross section in a predetermined cross sectional area ratio, the combined longitudinal portions being adhered together at the ground planar surfaces, conjointly having the same diameter as the quartz rod core and being coaxially connected to the core at a straight portion of the transmission line. The branch structure of the present invention can divide light for transmission into a branch line at a desired ratio with a reduced transmission loss.