Optical fiber length adjuster

An endoscope comprising:

• an insertion portion for insertion into a body to be observed;
• an optical fiber provided through the insertion portion, the optical fiber being configured to guide light from a light source to a distal end of the insertion portion;
• and
• an optical fiber length adjuster comprising:
• a holding portion to hold the optical fiber, and
• an entrance and an exit for the optical fiber,
• wherein the optical fiber length adjuster being configured to adjust a length of a portion of the optical fiber positioned in the insertion portion in response to a curving operation of the insertion portion;
• the optical fiber length adjuster being located between the insertion portion of the endoscope and the light source, and
• the optical fiber length adjuster adjusting the length of the portion of the optical fiber positioned in the insertion portion resulting from the curving operation of the insertion portion of the endoscope, the optical fiber length adjuster being configured to adjust the length so as to suppress an external force applied to the optical fiber resulting from the curving operation where the length changes so as to increase the length of the portion of the optical fiber positioned in the insertion portion when the optical fiber held by the holding portion receives the external force in a pulling direction of the optical fiber, and to decrease the length of the portion of the optical fiber positioned in the insertion portion when the optical fiber held by the holding portion does not receive the external force in the pulling direction of the optical fiber.