Fabrication method of multi-core fiber Bragg grating probe used for measuring structures of a micro part based on the capillary self-assemble technique

A fabrication method of a multi-core FBG probe for measuring structures of a micro part based on the capillary self-assemble technique, comprising:

• reducing the diameter of the fiber inscribed with FBG by:
• preparing a fiber, inscribed with FBG, of 100 mm˜1000 mm in length;
• where the FBG part, located at the 30 mm˜50 mm from the terminal of the fiber inscribed with FBG, is 10 mm˜20 mm in length;
• stripping a coating of 50 mm˜80 mm in length off the fiber inscribed with FBG from its terminal close to the FBG part;
• reducing the diameter of the FBG part without the coating of the fiber inscribed with FBG using a mechanical method, which includes:
• straightening the fiber inscribed with FBG,
• fixing the fiber inscribed with FBG on a setting mechanism of a synchronous-rotation motor and aligning the axis of the fiber inscribed with FBG with that of the synchronous-rotation motor,
• polishing the fiber inscribed with FBG, the wheel covered by the polishing slice above the axis of rotation of the synchronous-rotation motor polishes the part without the coating of the fiber inscribed with FBG repeatedly at a constant speed along its axis, and
• monitoring the procedure of the polishing with a microscopy system and stopping the polishing when the diameter of the part without the coating of the fiber inscribed with FBG is d, wherein d is in a range from 50 μm to 100 μm, and the fiber inscribed with FBG whose diameter has been reduced is achieved;
• cutting off the fiber inscribed with FBG whose diameter has been reduced of 30 mm˜50 mm in length using a cleaver, and making sure that the FBG part is located at the terminal of the fiber inscribed with FBG whose diameter has been reduced and its length is in a range from 5 to 10 mm;
• and
• washing the fiber inscribed with FBG whose diameter has been reduced using an ultrasonic cleaner with the anhydrous ethanol for 5 min˜20 min;
• Self-assembling the fiber inscribed with FBG whose diameter has been reduced by:
• preparing a tube of 10 mm˜30 mm in length and D=(50 μm˜100 μm)×3+(1 μm−50 μm) in inner diameter which has an inner taper angle at one terminal;
• inserting the N fibers inscribed with FBG whose diameter has been reduced by step 1 into the tube from the terminal with an inner taper angle and making sure that their FBG terminals of 5 mm˜10 mm in length out of the tube is parallel;
• fixing the tube vertically and immersing the FBG terminal of the fibers inscribed with FBG whose diameter has been reduced into the a glass with the UV adhesive of less than 100 cp in viscosity for 5 min˜15 min, wherein the immersion depth is 3 mm˜6 mm;
• the UV adhesive is raised in the gaps between the fibers inscribed with FBG whose diameter has been reduced and a most compact structure of fiber bundle is formed as a result of the capillary self-assembly;
• taking the tube and the fiber bundle within the tube out of the UV adhesive without the dislocation of the fiber bundle, and curing the fiber bundle with UV adhesive using a UV light for 1 min˜10 min to form the multi-core FBG;
• and
• filling the inner taper angle of the tube with the thermosetting adhesive and curing it using a heater at a constant temperature of 50° C.˜180° C. for 10 min˜60 min;
• polishing the terminal of the multi-core FBG by:
• fixing the tube with the multi-core FBG on an optic fiber polishing machine and adjusting the height of the tube to make the terminal of the multi-core FBG contacted with the polishing slice;
• polishing the terminal of the multi-core FBG as the way for processing a FC/PC connector and stopping the polishing when the terminal is smooth and impeccable, and the polished multi-core FBG is achieved;
• and
• cleaning the terminal of the polished multi-core FBG using the dust-free paper and anhydrous ethanol;
• fabricating a spherical tip on the polishing terminal of the polished multi-core FBG by:
• fixing the tube with the polished multi-core FBG processed by step 3 vertically;
• adjusting the height of the polished multi-core FBG and make the polishing terminal located at 0.5 mm˜3 mm below the electrode of the electric discharge machine;
• and
• adjusting discharge time and intensity of an electric discharge machine and melting the polished multi-core FBG;
• the melt fiber forms a favorable sphere because of the gravity and the surface tension, and a spherical tip is fabricated on the polishing terminal of the polished multi-core FBG after it becomes cool;
• a multi-core FBG probe is thus fabricated.