A method of stabilizing the mean wavelength of light generated by a superfluorescent fiber source, the method comprising: providing the SFS, the SFS comprising: an Er-doped fiber having a first end, a second end, and a length between the first end and the second end; a coupler optically coupled to the first end of the EDF; a pump source optically coupled to the coupler, the pump source producing pump light, the mean wavelength influenced by a wavelength of the pump light, the wavelength of the pump light dependent on the temperature of the pump source and dependent on the power of the pump light, the pump light propagating to the EDF via the coupler, whereby the EDF responds to the pump light by producing forward amplified spontaneous emission light propagating away from the pump source and backward ASE light propagating towards the pump source; a mirror optically coupled to the coupler, whereby the mirror reflects the backward ASE light as reflected ASE light which propagates to the EDF, the reflected ASE light amplified upon traveling through the EDF, the forward ASE light and the amplified reflected ASE light propagating out of the second end of the EDF; and an optical isolator coupled to the second end of the EDF, the forward ASE light and the amplified reflected ASE light from the second end of the EDF being transmitted through the optical isolator as the SFS output light; selecting the length of the EDF to reduce the dependence of the mean wavelength on the pump light power and to reduce the contribution of the forward ASE light to the output light such that the stability of the mean wavelength is improved; and reducing the influence of the pump light wavelength on the stability of the mean wavelength by reducing variations of the temperature of the pump source or by tuning the pump source to a wavelength at which a first order-dependence of the mean wavelength on the pump light wavelength is small or substantially zero. providing the SFS, the SFS comprising: an Er-doped fiber having a first end, a second end, and a length between the first end and the second end; a coupler optically coupled to the first end of the EDF; a pump source optically coupled to the coupler, the pump source producing pump light, the mean wavelength influenced by a wavelength of the pump light, the wavelength of the pump light dependent on the temperature of the pump source and dependent on the power of the pump light, the pump light propagating to the EDF via the coupler, whereby the EDF responds to the pump light by producing forward amplified spontaneous emission light propagating away from the pump source and backward ASE light propagating towards the pump source; a mirror optically coupled to the coupler, whereby the mirror reflects the backward ASE light as reflected ASE light which propagates to the EDF, the reflected ASE light amplified upon traveling through the EDF, the forward ASE light and the amplified reflected ASE light propagating out of the second end of the EDF; and an optical isolator coupled to the second end of the EDF, the forward ASE light and the amplified reflected ASE light from the second end of the EDF being transmitted through the optical isolator as the SFS output light; an Er-doped fiber having a first end, a second end, and a length between the first end and the second end; a coupler optically coupled to the first end of the EDF; a pump source optically coupled to the coupler, the pump source producing pump light, the mean wavelength influenced by a wavelength of the pump light, the wavelength of the pump light dependent on the temperature of the pump source and dependent on the power of the pump light, the pump light propagating to the EDF via the coupler, whereby the EDF responds to the pump light by producing forward amplified spontaneous emission light propagating away from the pump source and backward ASE light propagating towards the pump source; a mirror optically coupled to the coupler, whereby the mirror reflects the backward ASE light as reflected ASE light which propagates to the EDF, the reflected ASE light amplified upon traveling through the EDF, the forward ASE light and the amplified reflected ASE light propagating out of the second end of the EDF; and an optical isolator coupled to the second end of the EDF, the forward ASE light and the amplified reflected ASE light from the second end of the EDF being transmitted through the optical isolator as the SFS output light; selecting the length of the EDF to reduce the dependence of the mean wavelength on the pump light power and to reduce the contribution of the forward ASE light to the output light such that the stability of the mean wavelength is improved; and reducing the influence of the pump light wavelength on the stability of the mean wavelength by reducing variations of the temperature of the pump source or by tuning the pump source to a wavelength at which a first order-dependence of the mean wavelength on the pump light wavelength is small or substantially zero.