A tuneable DBR laser (1; 1', 1") comprising an amplifier section containing an active material, a part-reflecting optical output, a connection section which at an end of the amplifier section which lies opposite the output of the DBR laser connects to the amplifier section, and a wavelength-selective reflector (7a, 7b, 7c, 7d) which is optically coupled to the amplifier section by way of the connection section, and at least one further wavelength selective reflector (7a, 7b, 7c, 7d), which is optically coupled to the amplifier section likewise by way of the connection section, wherein the connection section comprises at least one MMI coupler and several wave guides (13a, 13b, 13c, 13d; 16a, 16b, 16c, 16d), wherein a phase shifter (11a, 11b, 11c, 11d) is arranged in a course of at least one of these wave guides (13a, 13b, 13c, 13d; 16a, 16b, 16c, 16d) and wherein the wavelength-selective reflectors (7a, 7b, 7c, 7d) differ from one another by way of different reflection spectra and are in each case connected to one of several outputs (10a, 10b, 10c, 10d) of the at least one MMI coupler, characterised in that the waveguides (13a, 13b, 13c, 13d; 16a, 16b, 16c, 16d) are running next to one another, so that in each case different optical paths lead from the amplifier section to each of the reflectors (7a, 7b, 7c, 7d), through the at least one MMI coupler and in each case one of the waveguides (13a, 13b, 13c, 13d; 16a, 16b, 16c, 16d), wherein the DBR laser by way of activating the at least one phase shifter (11a, 11b, 11c, 11d) can be switched over between different resonators which are delimited in each case by one of the wavelength-selective reflectors (7a, 7b, 7c, 7d), wherein (a) the connection section comprises a first MMI coupler and a second MMI coupler, wherein outputs of the first MMI coupler are connected by way of the waveguides (13a, 13b, 13c, 13d) running next to one another, in each case to one of several inputs (14a, 14b, 14c, 14d) of the second MMI coupler and wherein the wavelength-selective reflectors (7a, 7b, 7c, 7d) are connected in each case to one of several outputs (10a, 10b, 10c, 10d) of the second MMI coupler, or (b) the at least one MMI coupler comprises at least two further outputs (15a, 15b, 15c, 15d), the further outputs (15a, 15b, 15c, 15d) lying opposite the outputs (10a, 10b, 10c) of this MMI coupler which are connected to the wavelength-selective reflectors (10a, 10b, 10c) and being connected in each case by way of one of the waveguides (16a, 16b, 16c, 16d) running next to one another to a mirror (17a, 17b, 17c, 17d) which reflects back into the respective waveguide (16a, 16b, 16c, 16d), wherein the amplifier section is optically coupled to an input of this MMI coupler, which preferably lies opposite the mentioned further outputs (15a, 15b, 15c, 15d). (a) the connection section comprises a first MMI coupler and a second MMI coupler, wherein outputs of the first MMI coupler are connected by way of the waveguides (13a, 13b, 13c, 13d) running next to one another, in each case to one of several inputs (14a, 14b, 14c, 14d) of the second MMI coupler and wherein the wavelength-selective reflectors (7a, 7b, 7c, 7d) are connected in each case to one of several outputs (10a, 10b, 10c, 10d) of the second MMI coupler, or (b) the at least one MMI coupler comprises at least two further outputs (15a, 15b, 15c, 15d), the further outputs (15a, 15b, 15c, 15d) lying opposite the outputs (10a, 10b, 10c) of this MMI coupler which are connected to the wavelength-selective reflectors (10a, 10b, 10c) and being connected in each case by way of one of the waveguides (16a, 16b, 16c, 16d) running next to one another to a mirror (17a, 17b, 17c, 17d) which reflects back into the respective waveguide (16a, 16b, 16c, 16d), wherein the amplifier section is optically coupled to an input of this MMI coupler, which preferably lies opposite the mentioned further outputs (15a, 15b, 15c, 15d).