Patent ID: 8902419

Claim:
A detection apparatus comprising: a first light source group having a plurality of light sources including first and second light sources; a switch that selectively activates any one of the plurality of light sources; a first optical system that introduces light from the activated light source into an electrical conductor of an optical device; a plurality of polarization control elements, one of the plurality of polarization control elements receiving the light from the activated light source so as to control a polarization direction of the activated light source, and a detector that detects Raman scattering light from light scattered or reflected by the electrical conductor, wherein when the detector detects the Raman scattering light at an intensity equal to or lower than a predetermined intensity, the switch deactivates the first light source, which is activated by the switch, and activates the second light source, and a first polarization direction of first light, which is controlled by one of the plurality of polarization control elements, from the first light source is different from a second polarization direction of second light, which is controlled by one of the plurality of polarization control elements, from the second light source.