Optical device and optical receiving device

An optical reception apparatus comprising:

• a first isolator that is arranged on an input stage of an optical amplifier that optically amplifies incident light, and inputs the incident light to the optical amplifier;
• a second isolator that is arranged on an output stage of the optical amplifier and receives input of incident light that has been optically amplified by the optical amplifier;
• and
• a light receiving device that receives the optically amplified incident light from the second isolator, wherein
• the first isolator inputs first linearly-polarized incident light that has been converted from randomly-polarized incident light and that has been transmitted to the optical amplifier;
• and
• the second isolator, when reflected light of the first linearly-polarized incident light that has been optically amplified by the optical amplifier is input from a the reverse direction, converts the reflected light of the first linearly-polarized incident light to reflected light of second linearly-polarized light that is orthogonal to the reflected light of the first linearly-polarized incident light.