[1] Iwatsuki K, Okamuro H, Saruwatari M. Wavelength-tunable single-frequency and single-polarization Er-doped fibre ring laser with 1.4 kHz linewidth [J]. Electron. Lett., 1990, 26(24): 2033-2034

[2] Kalli K, Jackson D A. Ring resonator optical spectrum analyzer with 20 kHz resolution [J]. Opt. Lett., 1992,11(15): 1090-1092

[8] Okamura H, Iwatsuki K. A finesse-enhance Er-doped-fiber ring resonator [J]. IEEE J. Lightwave Tech., 1991,

[9] (11): 1554-15609.Gallion P B et al. Quantum phase noise and field correlation in single frequency semiconductor laser system [J].IEEE J. Quantum Electron., 1984, QE-20(4): 343-349

[10] Okoshi T et al. Novel method for high resolution measurement of laser output spectrum [J]. Electron. Lett., 1980,16(16): 630-631