Bending detecting system, light guide body, tubular apparatus, light detecting apparatus, light detecting method, and optical bending measuring apparatus

A light guide body comprising:

• a light guide, having elongated shape, configured to guide an incident light in a propagating direction, wherein the light guide comprises:
• a core;
• and
• a cladding disposed around the core;
• a first grating disposed in a boundary area of a boundary between the core and the cladding,
• wherein the first grating comprises a first periodic structure along the propagating direction with a first pitch, and
• wherein the first grating is configured to generate an first diffracted light form the incident light;
• and
• a second grating, disposed in the boundary area of the boundary,
• wherein the second grating comprises a second periodic structure along the propagating direction with a second pitch, and
• wherein the second grating is configured to generate a second diffracted light from the incident light,
• wherein the second grating is configured to be disposed in a position different from a position of the first grating about at least one of a propagating direction and a predetermined axis direction of the light guide, the predetermined axis direction being perpendicular to the propagating direction.

A light detecting apparatus for detecting bending of a light guide, the light detecting apparatus comprising:

• a light detector configured to:
• detect a first diffracted light from the light guide, the first diffracted light being generated from an incident light emitted into the light guide;
• and
• detect a bending of the light guide based upon an optical feature amount of the first diffracted light.

An optical bending measuring apparatus for measuring bending of a light guide, the optical apparatus comprising:

• a light source which supplies measurement light;
• a light guide which has a core and a cladding and which transmits the measurement light in a longitudinal axis direction thereof;
• sensing parts provided in positions different in the longitudinal axis direction of the light guide and each having a grating, the grating being provided in contact with the core or provided in parts of the cladding, and the grating generating diffracted lights from the measurement light being traveled in the core;
• a light detector which detects lights including the diffracted lights output from the light guide;
• and
• a processer which separates the diffracted lights at respective wavelengths from the lights, and independently measures bending amounts of the positions of the light guide on the basis of an intensity change of the separated diffracted lights.