An optically transparent protective coating is described that remains stable at elevated temperatures associated with optical fiber-based sensor applications and is sufficiently transparent to allow for conventional fiber Bragg gratings (FBGs) to be formed by directly writing through the coating. In particular, vinyl group-containing silicone polymers have been found to provide the UV transparency required for a write-through coating (WTC) and promising mechanical properties for protecting the optical fibers, while also being able to withstand elevated temperatures for extended periods of time.

An optically transparent protective coating is described that remains stable at elevated temperatures associated with optical fiber-based sensor applications and is sufficiently transparent to allow for conventional fiber Bragg gratings (FBGs) to be formed by directly writing through the coating. In particular, vinyl group-containing silicone polymers have been found to provide the UV transparency required for a write-through coating (WTC) and promising mechanical properties for protecting the optical fibers, while also being able to withstand elevated temperatures for extended periods of time.

The optical fibers disclosed is a single mode optical fiber comprising a core region and a cladding region surrounding and directly adjacent to the core region. The core region can have a radius r.sub.1 in a range from 3 μm to 7 μm and a relative refractive index profile Δ.sub.1 having a maximum relative refractive index Δ.sub.1max in the range from 0.25% to 0.50%. The cladding region can include a first outer cladding region and a second outer cladding region surrounding and directly adjacent to the first outer cladding region. The first outer cladding region can have a radius r.sub.4a. The second outer cladding region can have a radius r.sub.4b less than or equal to 45 μm and comprising silica based glass doped with titania.

The optical fibers disclosed is a single mode optical fiber comprising a core region and a cladding region surrounding and directly adjacent to the core region. The core region can have a radius r.sub.1 in a range from 3 μm to 7 μm and a relative refractive index profile Δ.sub.1 having a maximum relative refractive index Δ.sub.1max in the range from 0.25% to 0.50%. The cladding region can include a first outer cladding region and a second outer cladding region surrounding and directly adjacent to the first outer cladding region. The first outer cladding region can have a radius r.sub.4a. The second outer cladding region can have a radius r.sub.4b less than or equal to 45 μm and comprising silica based glass doped with titania.

Provided is a colored optical fiber of which a primary layer is easily formed. The colored optical fiber includes a bare optical fiber, a primary layer formed of an ultraviolet curing resin covering the bare optical fiber, and a secondary layer formed of an ultraviolet curing resin covering the primary layer. Young's modulus of the primary layer is smaller than 70% with respect to a saturated Young's modulus of the primary layer. The saturated Young's modulus of the primary layer is larger than or equal to 0.84 MPa.

Provided is a colored optical fiber of which a primary layer is easily formed. The colored optical fiber includes a bare optical fiber, a primary layer formed of an ultraviolet curing resin covering the bare optical fiber, and a secondary layer formed of an ultraviolet curing resin covering the primary layer. Young's modulus of the primary layer is smaller than 70% with respect to a saturated Young's modulus of the primary layer. The saturated Young's modulus of the primary layer is larger than or equal to 0.84 MPa.

A fibre optic cable (500, 700) comprises retractable fibre units (502) extending in parallel with one another within an extruded polymer tube (504). The fibre units are free to slide in the tube such that a selected fibre unit (702a) can be accessed and re-directed by forming an opening in a wall of the tube (504) and withdrawing the selected fibre unit through the opening (710). Each fibre unit comprises two or more optical fibres (506) embedded in a solid resin material (520) to form a coated fibre bundle and an extruded polymer sheath (524). The fibre optic cable is manufactured by feeding the fibre units through an extrusion head (602) by which the extruded tube (504) is formed. The sheath (524) of each fibre unit is primarily polyethylene. A lining (510) of the extruded polymer tube is formed by polymer other than polyethylene, for example polypropylene.

A fibre optic cable (500, 700) comprises retractable fibre units (502) extending in parallel with one another within an extruded polymer tube (504). The fibre units are free to slide in the tube such that a selected fibre unit (702a) can be accessed and re-directed by forming an opening in a wall of the tube (504) and withdrawing the selected fibre unit through the opening (710). Each fibre unit comprises two or more optical fibres (506) embedded in a solid resin material (520) to form a coated fibre bundle and an extruded polymer sheath (524). The fibre optic cable is manufactured by feeding the fibre units through an extrusion head (602) by which the extruded tube (504) is formed. The sheath (524) of each fibre unit is primarily polyethylene. A lining (510) of the extruded polymer tube is formed by polymer other than polyethylene, for example polypropylene.

A perovskite optical element includes a light guiding unit and a luminescent layer. The light guiding unit is configured to conduct light and serves as a resonant cavity. The luminescent layer is a thin film made of perovskite material and clads the light guiding unit. The luminescent layer is configured to be excited by an excitation module to emit light. The light is conducted and output by the light guiding unit. A manufacturing method of a perovskite optical element includes preparing a dip coating solution; dipping a single crystal optical fiber in the dip coating solution for one hour, removing the single crystal optical fiber out of the dip coating solution, and drying the single crystal optical fiber; and placing the single crystal optical fiber into a tube furnace, heating the crystal optical fiber, and introducing synthetic molecules into the tube furnace.

A perovskite optical element includes a light guiding unit and a luminescent layer. The light guiding unit is configured to conduct light and serves as a resonant cavity. The luminescent layer is a thin film made of perovskite material and clads the light guiding unit. The luminescent layer is configured to be excited by an excitation module to emit light. The light is conducted and output by the light guiding unit. A manufacturing method of a perovskite optical element includes preparing a dip coating solution; dipping a single crystal optical fiber in the dip coating solution for one hour, removing the single crystal optical fiber out of the dip coating solution, and drying the single crystal optical fiber; and placing the single crystal optical fiber into a tube furnace, heating the crystal optical fiber, and introducing synthetic molecules into the tube furnace.