Reliability assessment of multiwell distributed feedback laser source for direct detection links at 2.6 Gbit/s

The paper, describing the results of prequalification reliability tests for multiple quantum-well DFB lasers, is the first reported work in which lasers, degraded to the end of life for threshold current, exhibit stable single-mode performance with side-mode suppression ratios exceeding 45 dB and unchanged dynamic performance at 2.6 Gbit/s. Lifetests of laser chips were carried out at 50°C and 125°C and the dynamic performance of these laser chips was measured at 0 hours and at selected times during the lifetest. The lifetest results at 50°C showed a small initial change but exhibited no significant ageing after 12000 h. The median predicted change in drive current for 5 mW at 25 years was -3%, with more than 98% of the sampling demonstrating less than a 20% predicted increase. Under overstress conditions at 125°C it is predicted that in excess of 90% of the sample will exhibit an increase in drive current of less than 50% in 25 years. This gives a high degree of confidence in the CW performance of the MQW DFB ridge laser. As was expected from the stable CW performance, no significant drift was observed in the dynamic performance. Devices subjected to further overstress tests at 160°C exhibited a significant degradation corresponding to an end of life condition of a 50% increase in drive current. Despite this degradation, neither the side-mode suppression ratio nor the patterning were observed to change. These results give the confidence that the MQW DFB ridge-waveguide lasers will not only meet the reliability requirements of land-based and submerged links in terms of CW performance and factors crucial to 2.6 Gbit/s but they will also exhibit stable single-mode performance, and patterning, irrespective of the degree of degradation