The Fabry-Perot semiconductor laser (10) includes a laser beam which is coupled into an external cavity with a length of less than 50 m. The fundamental frequency of the cavity is different for different wavelengths. The facet (11) of the laser which is nearest to the cavity has a reflectivity greater than 3 per cent. The external cavity consists of two or more discrete, wavelength selective reflectors. The reflectors consists of two or more reflection gratings arranged one after another in a monomode glass fibre, with different central wavelengths and with reflectivities less than 80 per cent.
展开▼
