Optical fiber sensors having long active lengths, systems, and methods

A method of manufacturing an optical fiber sensor according to claim 17 further comprising forming a tail portion that extends beyond the forward end of the gutter by a distance greater than or equal to 5 Do.

A method of manufacturing an optical fiber sensor, comprising:

• providing a structure-forming fiber having a central portion etchable at a first rate when exposed to an etching medium, an inner cladding portion surrounding the central portion having an etching rate that is greater than the etching rate of the central portion when exposed to the etching medium, and an annular outer cladding portion surrounding the inner cladding portion having an etching rate that is less than the etching rate of both the central portion and the inner cladding portion when exposed to the etching medium;
• and
• exposing an end of the structure-forming fiber to the etching medium for a sufficient time to produce an outer dimension Do, a pedestal, and a gutter surrounding the pedestal having a gutter depth defining an active region of length, L, wherein L/Do≧0.5.

A method of manufacturing an optical fiber sensor, comprising:

• providing a structure-forming fiber having a central portion having a composition of doped silica, an annular inner cladding portion surrounding the central portion having a composition of doped silica that is preferentially doped to provide an etching rate in an etching medium greater than the central portion, and an outer annulus portion surrounding the gutter portion and having a composition of substantially pure silica to provide an etching rate in the etching medium less than both the central portion and the annular inner cladding portion;
• and
• exposing an end of the first optical fiber segment to an etchant for a sufficient time to produce an outer dimension Do, pedestal, and a gutter surrounding the pedestal having a gutter depth defining an active region of length, L, wherein L/Do≧0.5.