[1] [1] Snitzer E. Proposed fiber cavities for optical lasers［J］. Journal of Applied Physics, 1961, 32: 36-39.

[2] [2] Snitzer E. Optical maser action of Nd3+ in a barium crown glass［J］. Physical Review Letters， 1961, 7(12): 444-446.

[3] [3] Koester C J, Snitzer E. Amplification in a fiber laser［J］. Applied Optics, 1964, 3(10): 1182-1186.

[4] [4] Poole S B, Payne D N, Fermann M E. Fabrication of low-loss optical fibres containing rare-earth ions［J］. Electronics Letters, 1985, 21(17): 737-738.

[5] [5] Mears R J, Reekie L, Poole S B, et al. Neodymium-doped silica single mode fibre lasers［J］. Electronics Letters, 1985, 21(17): 738-740.

[6] [6] Jeong Y, Sahu J, Payne D N, et al. Ytterbium-doped large-core fiber laser with 1.36 kW continuous-wave output power［J］. Optics Express, 2004, 12(25): 6088-6092.

[8] [8] Sekiya E H, Barua P, Saito K, et al. Fabrication of Yb-doped silica glass through the modification of MCVD process［J］. Journal of Non-Crystalline Solids, 2008, 354(42): 4737-4742.

[9] [9] Petita V, Sekiya E H, Okazakia T, et al. Improvement of Yb3+ doped optical fiber preforms by using MCVD method［C］. SPIE, 2008, 6998: 69980A.

[10] [10] Webb A S, Boyland A J, Standish R J, et al. MCVD in-situ solution doping process for the fabrication of complex design large core rare-earth doped fibers［J］. Journal of Non-Crystalline Solids, 2010, 356(18-19): 848-851.

[11] [11] Leich M, Just F, Langner A, et al. Highly efficient Yb-doped silica fibers prepared by powder sinter technology［J］. Optics Letters, 2011, 36(9): 1557-1559.

[12] [12] Yoo S, Basu C, Boyland A J, et al. Photodarkening in Yb-doped aluminosilicate fibers induced by 488 nm irradiation［J］. Optics Letters, 2007, 32(12): 1626-1628.

[13] [13] Dragic P D, Carlson D C, Croteau A. Characterization of defect luminescence in Yb doped silica fibers: Part I NBOHC［J］. Optics Express, 2008, 16(7): 4688-4697.

[14] [14] Dragic P D, Liu Y S, Galvin T C, et al. Ultraviolet absorption and excitation spectroscopy of rare-earth-doped glass fibers derived from glassy and crystalline performs［C］. SPIE, 2012, 8237: 82370T.

[15] [15] Engholm M, Norin L, Aberg D. Strong UV absorption and visible luminescence in ytterbium-doped aluminosilicate glass under UV excitation［J］. Optics Letters, 2007, 32(22): 3352-3354.

[16] [16] Engholm M, Norin L. Preventing photodarkening in ytterbium-doped high power fiber lasers; correlation to the UV-transparency of the core glass［J］. Optics Express, 2008, 16(2): 1260-1268.

[17] [17] Engholm M, Norin L. Comment on “Photodarkening in Yb-doped aluminosilicate fibers induced by 488 nm irradiation”［J］. Optics Letters, 2008, 33(11): 1216.

[18] [18] Guzman Chávez A D, Kir′yanov A V, Barmenkov Y O, et al. Reversible photo-darkening and resonant photo-bleaching of ytterbium-doped silica fiber at in-core 977-nm and 543-nm irradiation［J］. Laser Physics Letters, 2007, 4(10): 734-739.

[19] [19] Kitabayashi T, Ikeda M, Nakai M, et al. Population inversion factor dependence of photodarkening of Yb-doped fibers and its suppression by highly aluminum doping［C］. CLEO, 2006: OThC5.

[20] [20] Morasse B, Chatigny B, Gagnon E, et al. Low photodarkening single cladding ytterbium fibre amplifier［C］. SPIE, 2007, 6453: 64530H.

[21] [21] Shubin A V, Yashkov M V, Melkumov M A, et al. Photodarkening of alumosilicate and phosphosilicate Yb-doped fibers［C］. CLEO, 2007: CJ3-1-THU.

[22] [22] Peretti R, Jurdyc A M, Jacquier B, et al. How do traces of thulium explain photodarkening in Yb doped fibers ［J］. Optics Express, 2010, 18(19): 20455-20460.

[23] [23] Jetschke S, Unger S, Schwuchow A, et al. Evidence of Tm impact in low-photodarkening Yb-doped fibers［J］. Optics Express, 2013, 21(6): 7590-7598.

[24] [24] Jetschke S, Unger S, Schwuchow A, et al. Efficient Yb laser fibers with low photodarkening by optimization of the core composition［J］. Optics Express, 2008, 16(20): 15540-15545.

[25] [25] Engholm M, Jelger P, Laurell F, et al. Improved photodarkening resistivity in ytterbium-doped fiber lasers by cerium codoping［J］. Optics Letters, 2009, 34(8): 1285-1287.

[26] [26] Engholm M, Norin L. Ytterbium-doped fibers co-doped with cerium: next generation of fibers for high power fiber lasers ［C］. SPIE, 2010, 7580: 758008.

[27] [27] Hnninger I M, Boullet J, Cardinal T, et al. Photodarkening and photobleaching of an ytterbium-doped silica double-clad LMA fiber［J］. Optics Express, 2007, 15(4): 1606-1611.

[28] [28] Piccoli R, Gebavi H, Lablonde L, et al. Evidence of photodarkening mitigation in Yb-doped fiber lasers by low power 405 nm radiation［J］. IEEE Photonics Technology Letters, 2013, 26(1): 50-53.

[29] [29] Piccoli R, Robin T, Brand T, et al. Effective photodarkening suppression in Yb doped fiber lasers by visible light injection［J］. Optics Express, 2014, 22(7): 7638-7643.

[30] [30] Gebavi H, Taccheo S, Lablonde L, et al. Mitigation of photodarkening phenomenon in fiber lasers by 633 nm light exposure［J］. Optics Letters, 2013, 38(2): 196-198.

[31] [31] Zhao N, Xing Y B, Li J M, et al. 793 nm pump induced photo-bleaching of photodarkened Yb3+-doped fibers［J］. Optics Express, 2015, 23(19): 25272-25278.

[32] [32] Jasapara J, Andrejco M, Digiovanni D, et al. Effect of heat and H2 gas on the photo-darkening of Yb+3 fibers［C］. CLEO, 2006: CTuQ5.

[33] [33] Basu C, Yoo S, Boyland A J, et al. Influence of temperature on the post-irradiation temporal loss evolution in Yb-doped aluminosilicate fibers, photodarkened by 488 nm CW irradiation［C］. CLEO, 2009.

[34] [34] Leich M, Rpke U, Jetschke S, et al. Non-isothermal bleaching of photodarkened Yb-doped fibers［J］. Optics Express, 2009, 17(15): 12588-12593.

[35] [35] Eidam T, Wirth C, Jauregui C, et al. Experimental observations of the threshold-like onset of mode instabilities in high power fiber amplifiers［J］. Optics Express, 2011, 19(14): 13218-13224.

[36] [36] Eidam T, Hanf S, Seise E, et al. Femtosecond fiber CPA system emitting 830 W average output power［J］. Optics Letters, 2010, 35(2): 94-96.

[37] [37] Smith A V, Smith J J. Mode instability in high power fiber amplifiers［J］. Optics Express, 2011, 19(11): 10180-10192.

[38] [38] Jauregui C, Eidam T, Otto H J, et al. Physical origin of mode instabilities in high-power fiber laser systems［J］. Optics Express, 2012, 20(12): 12912-12925.

[39] [39] Otto H J, Stutzki F, Jansen F, et al. Temporal dynamics of mode-instabilities in high-power fiber lasers and amplifiers［J］. Optics Express, 2012, 20(14): 15710-15722.

[40] [40] Wirth C, Schreiber T, Rekas M, et al. High-power linear-polarized narrow linewidth photonic crystal fiber amplifier［C］. SPIE, 2010, 7580: 75801H.

[41] [41] Ward B, Robin C, Dajani I. Origin of thermal modal instabilities in large mode area fiber amplifiers［J］. Optics Express, 2012, 20(10): 11407-11422.

[42] [42] Dong L, Peng X, Li J. Leakage channel optical fibers with large effective area［J］. Journal of the Optical Society of America B, 2007, 24(8): 1689-1697.

[43] [43] Dong L, Wu T W, Mckay H A, et al. All-glass large-core leakage channel fibers［J］. IEEE Journal of Selected Topics in Quantum Electronics, 2009, 15(1): 47-53

[44] [44] Liu C H, Chang G q, Litchinitser N, et al. Chirally coupled core fibers at 1550-nm and 1064-nm for effectively single-mode core size scaling［C］. CLEO, 2007: CTuBB3.

[45] [45] Craig Swan M, Liu C H, Guertin D, et al. 33 μm core effectively single mode chirally coupled core fiber laser at 1064-nm［C］. OFC/NFOEC, 2008: OWU2.

[46] [46] Karow M, Zhu C, Kracht D, et al. Fundamental Gaussian mode content measurements on active large core CCC fibers［C］. CLEO EUROPE/IQEC, 2013.

[47] [47] Wang Y B, Liao L, Zhao N, et al. Experimental demonstration of optical fiber laser with octagonal-shaped core［J］. Applied Physics A, 2015, 119(2): 791-794.

[48] [48] Wang Y B, Nan Z, Lei L, et al. A new type of Yb3+ doped fiber with an octagonal-shaped core［C］. CLEO, 2015: JTh2A.26.

[49] [49] Otto H J, Jauregui C, Stutzki F. Controlling mode instabilities by dynamic mode excitation with an acousto-optic deflector［J］. Optics Express, 2013, 21(14): 17285-17298.