Optical fibre laser pump source for fibre amplifiers

An optical fibre laser pump source for Pr fibre amplifiers in the 1300 nm region comprising:

• a semiconductor laser source for providing a first light output, said laser source having a wavelength emission within the wavelength band of about 800 nm to 1070 nm;
• a Yb.sup.3+ fibre laser comprising a double clad fibre having a pumped core and inner pump cladding, said core doped with a Yb ions;
• first coupling means for optically launching said first output into said inner pump cladding;
• said Yb.sup.3+ fibre laser having dominate emission spectra with first and second dominate emission peaks respectively at about 974 nm and 1033 nm;
• a pair of fibre gratings formed in said double clad fibre in spaced relation forming an optical resonator cavity;
• said fibre laser having a sufficient fibre length to provide reabsorption in the doped core sufficient to optically discriminate against laser emission at said first dominate emission peak of said Yb.sup.3+ fibre laser;
• said gratings both having a peak wavelength corresponding to the peak of the absorption band of Pr.sup.3+ within the wavelength band of 1012 nm to 1022 nm to optically discriminate against laser emission at said second dominate emission peak of said Yb.sup.3+ fibre laser;
• the combination of both optical discriminations against said first and second dominate emission peaks of said Yb.sup.3+ fibre laser forcing stable laser emission at an operational wavelength between 1012 nm to 1022 nm within the absorption band of Pr.sup.3+ ;
• one of said fibre gratings approximate to said semiconductor laser source having a maximum reflectivity, R.sub.1 at said operational wavelength and the other of said fibre gratings having a reflectivity, R.sub.2 at said operational wavelength less than maximum reflectivity to provide a second light output;
• and
• second coupling means for optically launching said second output into a fibre amplifier with a core doped Pr.sup.3+.