Packaging of fibre-optic communication lasers for the Gb/s range

A package for a DFB (distributed feedback) laser with integrated optical isolator is described. The design is based on a modular set-up: a laser module provided with a short ferruled pigtail is combined with an optical isolator module with the device fiber pigtail. Laser feedback due to reflections in the isolator module is avoided by slanting the collimated beam through the isolator. An advantage of the design is that both modules can be tested separately. Tests in a 2.5-Gb/s system show that proper data transmission is maintained over a 100-km fiber link despite a deliberately imposed back-reflection at a level of 10%. A bit error rate of 10^-10 at 10% laser feedback is obtained for -31 dBm detector power