A lighting device is formed of a bistable spring, a housing, a flexible light guide member, and a lighting module. The domed grid is held on an L-shaped ring such that a gap is formed between an outside diameter of the domed grid and the jacket. If a communication path fails, communication may continue along another path. Thus, the ARC of the present invention significantly reduces or prevents back reflection of light and the problem of the CD alteration caused by the diffracted andor reflected light. A capacitance C1 obtained by combining C1a and C1b is smaller than a capacitance C2 obtained by combining C2a and C2b.