| 摘要 |
A distributed-feedback (DFB) semi-conductor laser 2 emits a light beam which is injected into a fibre 16 through an optical isolator comprising a Faraday rotator 8, 10 and an output polariser 6. This beam next travels through a two-directional coupler 30, by virtue of which a fraction of the light is reflected by a feedback reflector 19 towards the laser 2, and another fraction is directed towards a member 24, 26, 28, 32 which measures the relative noise intensity affecting the forward beam. The angular position of the polariser 6 is adjusted so as to minimise the noise thus measured. The invention applies in particular to producing optical transmission heads for fibre-optic telecommunication systems. <IMAGE>
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