Fig. 1. Fabrication of optical fiber by melt-in-tube method. (a) Diagram of fiber drawing process; (b)-(d) fiber preforms based on ceramics or crystals; (e)-(f) cross sections of prepared optical fiber

Fig. 2. Main processes for fabricating microcrystalline optical fiber. (a) Drawn precursor fiber; (b) muffle furnace process; (c) microcrystalline optical fiber; (d)(e) nanocrystalline particles with certain size

Fig. 3. Crystallization process in microcrystalline optical fiber by MIT method. (a) Glass rod before drawing process; (b) crystallization appears in bottom after drawing process and glass rod turns to opaque; (c) X-ray diffraction patterns of samples 1#-4# (1# represents uncontrolled crystallized glass rod after drawing, 2# represents glass rod before drawing, 3# represents secondary melted glass after crystallization, 4# represents optical fiber core drawn by MIT method, and insert is opaque glass aft

Fig. 4. Laser processing on optical fibers. (a) Diagram of laser post-processing on optical fiber; (b) temperature distributions of fiber after laser irradiation

Fig. 5. In-situ chemical reaction in fiber drawing process. (a)(b) Chemical reaction and element migration during drawing process; (c)-(e) changes of core composition in different stages of fiber drawing process

Fig. 6. Semiconductor fiber connected with silica optical fiber network. (a) Coupling of spatial optical light and tapered semiconductor core optical fiber; (b) coupling of tapered semiconductor core optical fiber and single-mode fiber

Fig. 7. Laser applications of YAS fiber. (a) Diagram of all-fiber linear cavity based on Tm∶YAS fiber; (b) 2.0 μm laser output spectrum of Tm∶YAS fiber laser; (c) 1.0 μm laser output spectrum of Nd∶YAS fiber laser (insert is near-field energy distribution of home made all-fiber laser); (d) diagram of DBR fiber laser with highly doped Yb∶YAS; (e) longitudinal mode characteristics of single frequency fiber laser