Highly reliable and high power 980 nm pump laser diode module for underseacable systems

Highly reliable and high power weakly index guided buried-stripe type 980 n m pump laser diodes developed for undersea applications are reviewed. The 1 0,000-hour large scale reliability tests of the first generation LD chips s hows that 16.7 FIT for the random failure was confirmed at 10 degreesC with 60% confidence level at 120 mW output power. We also fabricated a FBG lock ed co-axial type module using a can-sealed LD with a two-lens system, which showed a stable FBG locked mode oscillation at 980 nm under the temperatur e range from 5 degreesC to 45 degreesC. The 5,000-hour heat cycle test of t he modules reveals that the cumulative failure rate after 27 years at 10 de greesC is expected to be 0.023%. These first generation LD modules were emp loyed in the transoceanic commercial systems such as Pacific Crossing-1 and the Japan-US cable system projects. We have also succeeded in developing t he 980 nm LD for higher output operation with optimizing waveguide design. The 1000 mum long LD showed CW kink-free operation up to 545 mW optical out put and a maximum output power of over 650 mW, which was limited by thermal rollover. In. addition, a preliminary aging test at 350 mW optical output power at 50 degreesC has shown stable operation up to 2,300 h. We also conf irmed 300 mW kink-free fiber output power with a co-axial type module with the improved coupling efficiency of approximately 78%. These figures are th e highest reported operation levels for 980-nm co-axial type modules.