[1] Poole S B, Payne D N, Fermann M E. Fabrication of low-loss optical fibres containing rare-earth ions. Electron. Lett., 1985, 2(17):737～738

[2] Iwatsuki K, Okamura H, Saruwatari M. Wavelength-tunable single-fre quency and single-polarisation Er-doped fibre ring laser with 1.4 kHz linewidt h. Electron. Lett., 1990, 26(21):2033～2035

[3] Gloag A, Langford N, McCallion K et al.. Continuously tunable s ingle-frequency erbium ring fiber laser. J. Opt. Soc. Am. (B), 1996, 13(5):921～925

[4] Ball G A, Morey W W, Glenn W H. Standing-wave monomode erbium fiber laser. IEEE Photon. Technol. Lett., 1991, 3(7):613～615

[5] Ball G A, Glenn W H. Design of a single-mode linear-cavity erbium fiber laser utilising Bragg reflectors. J. Lightwave Technol., 1992, 10(10):1338～1343

[6] Sejka M, Varming P, Hubner J et al.. Distributed feedback Er 3+-doped fibre laser. Electron. Lett., 1995, 31(17):14 45～1446

[7] Loh W H, Laming R I. 1.55 μm phase-shifted distributed feedback f ibre laser. Electron. Lett., 1995, 31(17):1440～1442

[8] Kringlebotn J T, Morkel P R, Reekie L et al.. Efficient diode- pumped single-frequency erbium: ytterbium fibre laser. IEEE Photon. Technol. Lett., 1993, 5(10):1162～1164