[1] [1] N. Amitay, H. M. Presby, F. V. Dimarcello et al.. Optical fiber tapersa novel approach to self-aligned beam expansion and single-mode hardware[J]. J. Lightwave Technol., 1987, LT-5(1): 70～76

[3] [3] Kazuo Shiraishi, Shin-Ichi Kuroo. A new lensed-fiber configuration employing cascaded GI-fiber chips[J]. J. Lightwave Technol., 2000, 18(6): 787～794

[4] [4] Osamu Hanaizumi, Yoshizo Aizawa, Hiroaki Minamide et al.. Fabrication of an expanded core fiber having MFD of 40 μm preserving outer diameter[J]. IEEE Photon. Technol. Lett., 1994, 6(7): 842～844

[5] [5] Kyung-Rok Kim, Kyunghwan Oh. All-fiber spot-size transformer for efficient free-space optical interconnecting devices[J]. Appl. Opt., 2003, 42(31): 6261～6266

[6] [6] Takashi Sato, Ryoichi Kasahara, Jun Sun et al.. In-line optical isolators integrated into a fiber array without alignment[J]. IEEE Photon. Technol. Lett., 1997, 9(7): 943～945

[8] [8] M. N. McLandrich. Core dopant profiles in weakly fused single-mode fibers[J]. Electron. Lett., 1988, 24(1): 8～10

[9] [9] Mitsuru Kihara, Michito Matsumoto, Taodashi Haibara et al.. Characteristics of thermally expanded core fiber[J]. J. Lightwave Technol., 1996, 14(10): 2209～2214

[10] [10] Yasuo Ohtera, Osamu Hanaizumi, Shojiro Kawakami. Numerical analysis of eigenmodes and splice losses of thermally diffused expanded core fibers[J]. J. Lightwave Technol., 1999, 17(12): 2675～2681