Light detection device and laser device

A light detection device comprising:

• a first optical fiber including a first core surrounded by a first cladding;
• a second optical fiber including a second core surrounded by a second cladding, wherein the second core has a diameter larger than a diameter of the first core and is connected to the first core;
• a first cladding mode stripper provided outside the first cladding;
• a first light detector;
• and
• a second light detector, wherein
• in a longitudinal direction of the first optical fiber, the first light detector is disposed on one side of the first cladding mode stripper and the second light detector is disposed on another side of the first cladding mode stripper,
• the first light detector detects Rayleigh scattering of light that propagates through the first core,
• the second light detector detects Rayleigh scattering of light that propagates through the first core or the second core, and
• at least one of the first optical fiber and the second optical fiber is a multimode fiber.