RELIABILITY ASSESSMENT OF MULTIWELL DISTRIBUTED-FEEDBACK LASER SOURCEFOR DIRECT-DETECTION LINKS AT 2.6 GBIT S/

The paper, describing the results of prequalification reliability test s for multiple quantum-well DFB lasers, is the first reported work in which lasers, degraded to the end of life for threshold current, exhib it stable single-mode performance with side-mode suppression ratios ex ceeding 45 dB and unchanged dynamic performance at 2.6 Gbit/s. Lifetes ts of laser chips were carried out at 50-degrees-C and 125-degrees-C a nd the dynamic performance of these laser chips was measured at 0 hour s and at selected times during the lifetest. The lifetest results at 5 0-degrees-C showed a small initial change but exhibited no significant ageing after 12 000 h. The median predicted change in drive current f or 5 mW at 25 years was -3%, with more than 98% of the sampling demons trating less than a 20% predicted increase. Under overstress condition s at 125-degrees-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 year s. 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-degrees-C exhibited a sig nificant degradation corresponding to an end of life condition of a 50 % increase in drive current. Despite this degradation, neither the sid e-mode suppression ratio nor the patterning were observed to change. T hese results give the confidence that the MQW DFB ridge-waveguide lase rs will not only meet the reliability requirements of land-based and s ubmerged links in terms of CW performance anf factors crucial to 2.6 G bit/s but they will also exhibit stable single-mode performance, and p atterning, irrespective of the degree of degradation.