An example light guide assembly for illuminating a display of an instrument cluster includes a light receiving portion, a light propagating portion and a conical surface positioned between the light receiving portion and the light propagating portion. If an optical fiber line acting as an optical transmission medium breaks in the optical transmission system, the signal power detected from the optical fiber decreases, whereby it changes to a set value or less or the amount of decrease in signal power per unit time changes by a set value or more. The first and second acoustic wave filter sections are longitudinally coupled resonator-type acoustic wave filter sections each including a plurality of IDTs disposed in a direction in which acoustic waves propagate. The system maintains and restores full-capacity communication services by switching at least a portion of the channel groups from a first optical fiber connection to a second optical fiber connection system based on the priority levels assigned to the channel groups. The driving mechanism has a first motor for driving one end of the rear axle in conjunction with a first driven member and a first transmission member, and a second motor for driving the other end of the rear axle in conjunction with a second driven member and a second transmission member. A second metal gridline can be formed by directly plating metal to an emitter region on the back side of the silicon substrate, eliminating the need for contact openings for the second metal gridline.