The present invention provides a metal strip coil that can suppress a shape failure at an end portion of the coil. A metal strip coil including a metal strip wound around a winding core, wherein the metal strip is wound from one end side toward the other end side of the winding core, turns back at the other end portion, is wound from the other end side toward the one end side of the winding core, turns back at the one end portion, and is repeatedly wound in such a manner, wherein in the turnback, the metal strip has a turnback portion at which the metal strip is wound in a direction perpendicular to the axial direction of the winding core, in a side view of the metal strip coil, the turnback portion is arcuate, and the turnback portions are formed in a multistage manner from the inner circumference toward the outer circumference, and a line connecting a midpoint of the arcuate arc with the center of the arc is formed so as to rotate stepwise in one direction, in an order of the arcuate turnback portions which are formed in a multistage manner from the inner circumference to the outer circumference.

A method of winding an optical fiber includes winding the optical fiber using a bobbin that includes: a body portion having two end portions; and a pair of flanges, respectively disposed at the end portions in an axial direction of the body portion. An inner surface of each of the flanges is inclined toward an outer side in the axial direction and toward a radial outer side. The method further includes guiding the optical fiber to the bobbin using a final pulley. The bobbin and the final pulley reciprocate relative to each other in the axial direction at a traverse speed V (mm/sec) such that 0.0050≤θ (rad)≤0.1000, where θ is a delay angle, θ=arctan (V/L), and L (mm) is a distance from a winding position of the optical fiber at the bobbin to the final pulley in a radial direction.

A method of winding an optical fiber includes winding the optical fiber using a bobbin that includes: a body portion having two end portions; and a pair of flanges, respectively disposed at the end portions in an axial direction of the body portion. An inner surface of each of the flanges is inclined toward an outer side in the axial direction and toward a radial outer side. The method further includes guiding the optical fiber to the bobbin using a final pulley. The bobbin and the final pulley reciprocate relative to each other in the axial direction at a traverse speed V (mm/sec) such that 0.0050≤θ (rad)≤0.1000, where θ is a delay angle, θ=arctan (V/L), and L (mm) is a distance from a winding position of the optical fiber at the bobbin to the final pulley in a radial direction.

A method of forming a fracking tool, such as a frac ball or a frac plug mandrel, may include: applying a resin to wet a filament; winding the wetted filament to form a cylinder; placing the cylinder in a cylindrical mold; increasing a pressure in the cylindrical mold to at least 3,000 psi; curing the resin at the pressure and a temperature of at least 250° F.; and extracting the cylinder from the mold. In some instances, the method may further include adding the resin and/or another resin into the cylindrical mold.

A method of forming a fracking tool, such as a frac ball or a frac plug mandrel, may include: applying a resin to wet a filament; winding the wetted filament to form a cylinder; placing the cylinder in a cylindrical mold; increasing a pressure in the cylindrical mold to at least 3,000 psi; curing the resin at the pressure and a temperature of at least 250° F.; and extracting the cylinder from the mold. In some instances, the method may further include adding the resin and/or another resin into the cylindrical mold.

A method of manufacturing an optical fiber, in which a coating is provided on a bare optical fiber, includes winding the optical fiber around a bobbin such that a strain sensing coefficient T.sub./KL is greater than 0 and less than or equal to 973, and a one-layer strain .sub.n is greater than or equal to 0.01.

A method of manufacturing an optical fiber, in which a coating is provided on a bare optical fiber, includes winding the optical fiber around a bobbin such that a strain sensing coefficient T.sub./KL is greater than 0 and less than or equal to 973, and a one-layer strain .sub.n is greater than or equal to 0.01.

A winding system contains a let off stand, a winding coordinator, and a wind-up stand. The left off stand contains a tape holder and a generally planar base which rotates in a first direction. The winding coordinator contains a generally planar section having an opening for an elongated element and rotates in a second direction opposite to the first direction.

A winding system contains a let off stand, a winding coordinator, and a wind-up stand. The left off stand contains a tape holder and a generally planar base which rotates in a first direction. The winding coordinator contains a generally planar section having an opening for an elongated element and rotates in a second direction opposite to the first direction.

A method of manufacturing an optical fiber, in which a coating is provided on a bare optical fiber, includes winding the optical fiber around a bobbin such that a strain relaxation coefficient T.sub./K is less than or equal to 292, and an one-layer strain .sub.n is greater than or equal to 0.01.