This paper presents the design, fabrication process, and experimental evaluation of a high-sensitivity, all-silica, all-fiber,
micro machined Fabry-Perot strain-sensor. This sensor has a short Fabry-Perot cavity and thus allows for the application
of low-resolution spectral interrogation systems; in our case the commercial white light signal interrogator was used. The
fabrication process includes the design and production of special sensor-forming optical-fiber. This fiber includes a
central titanium-doped region, a phosphorus doped-ring surrounding a titanium doped region, and pure silica cladding in
order to produce the proposed sensor, two sections of sensor forming fiber are cleaved and etched in a HF/IPA solution.
The phosphorus-doped region etches at a considerably higher rate than the other fiber-sections, and thus creates a deep
gutter on the cleaved fibers frontal surface. The titanium-doped region etches at a rate that is, to some extent, higher than
the etching-rate of pure silica, and thus creates a slightly retracted surface relative to the pure silica fiber-cladding. The
etched fibers are then re-spliced to create an all-silica strain sensor in "double configuration", which has a section of
etched sensor-forming fiber on both sides. Thus this sensor has a long active length, whilst the length of the Fabry-Perot
cavity can be adjusted by a titanium-doping level. The central titanium-doped region also creates a waveguide structure
that is used to deliver light to the cavity through one of the fibers. The proposed fabrication process is cost-effective and
suitable for high-volume production. The greatest achievement of the depicted in-line strain sensor is the extension of its
active sensor length, which is more than 50 times greater than the sensor-cavity's length, and is thus approximately 50
times more sensitive to strain. This sensor also exhibits low-intrinsic temperature sensitivity.