Force sensing in a distal region of an instrument including single-core or multi-core optical fiber

An optical processing apparatus, comprising:

• an optical fiber having a length;
• a core included in the optical fiber, wherein the core includes a plurality of Bragg gratings along an entire length of the optical fiber except for a portion of the core corresponding to an end region of the optical fiber where no Bragg gratings exist;
• an instrument including the optical fiber, the instrument having a distal region and a proximal region;
• a tubular structure encasing the end region of the optical fiber where no Bragg gratings exist and secured at the distal region of the instrument;
• an optical interferometric system coupled to the optical fiber and configured to process reflected light corresponding to a Rayleigh scatter pattern distributed along a portion of the core included within the tubular structure that does not include Bragg gratings to produce a measurement of strain due to a force present at the distal region of the instrument separate from bending induced strain.

An optical processing apparatus, comprising:

• an optical fiber having a length;
• a core included in the optical fiber, wherein the core includes a plurality of Bragg gratings along an entire length of the optical fiber except for a portion of the core corresponding to an end region of the optical fiber where no Bragg gratings exist;
• an instrument including the optical fiber, the instrument having a distal region and a proximal region;
• a tubular structure encasing the end region of the optical fiber where no Bragg gratings exist and secured at the distal region of the instrument;
• an optical interferometric system coupled to the optical fiber and configured to process reflected light from a portion of the core included within the tubular structure that does not include Bragg gratings to produce a measurement of strain due to a force present at the distal region of the instrument separate from bending induced strain,
• wherein the optical fiber is secured within the tubular structure by an epoxy, and
• wherein the optical interferometric system is configured to determine the strain present on the distal region of the instrument based on a first light reflection from a distal end of the optical fiber and on a second light reflection from a distal end surface of the epoxy.