Abstract: A photodetection device including: first optical fibers; a second optical fiber; an optical combiner having: an end face connected to an end face of each of the first optical fibers; and another end face connected to an end face of the second optical fiber; a first photodetector that detects an intensity of light propagating through at least one of the first optical fibers; a second photodetector that detects Rayleigh scattering of light propagating through the second optical fiber; and a calculator that calculates the intensity of light propagating in a predetermined direction through the first optical fibers or the second optical fiber, from a result of detection by the first photodetector and a result of detection by the second photodetector.

Abstract: A laser device includes at least one light source; a delivery fiber configured to propagate laser light launched from the light source; a monitor fiber optically coupled to the delivery fiber and configured to propagate a part of the light propagating in a direction opposite to a propagation direction of the laser light in the delivery fiber, and a light receiving unit configured to receive the light propagated by the monitor fiber. The light receiving unit is configured to detect first light included in a wavelength band of visible light.

Abstract: A laser device includes at least one light source; a delivery fiber that is configured to propagate of laser light emitted from the light source; and a first light detection unit and a second light detection unit configured to detect a part of light propagating in a direction opposite to a propagation direction of the laser light through the delivery fiber. The first light detection unit detects first light included in a wavelength band of visible light. The second light detection unit detects second light included in a wavelength band of near-infrared light.

Abstract: A photodetection device including: first optical fibers; a second optical fiber; an optical combiner having: an end face connected to an end face of each of the first optical fibers; and another end face connected to an end face of the second optical fiber; a first photodetector that detects an intensity of light propagating through at least one of the first optical fibers; a second photodetector that detects Rayleigh scattering of light propagating through the second optical fiber; and a calculator that calculates the intensity of light propagating in a predetermined direction through the first optical fibers or the second optical fiber, from a result of detection by the first photodetector and a result of detection by the second photodetector.

Abstract: A photodetector includes: a substrate; an optical fiber disposed on the substrate; and a photodetection element fixed to the substrate, and that detects scattered light of light guided by the optical fiber. The photodetector further includes: a first fixing member and a second fixing member that fix the optical fiber to the substrate.