1.3-µm Laser reliability determination for submarine cable systems

To meet the stringent requirements of a submarine cable system, our 1.3-μm laser prequalification program has two objectives — first, to define the testing methodology that will accurately evaluate the potential reliability of the laser; and second, to obtain a preliminary indication of laser reliability on which the system configuration can be designed. Our testing methodology involves a combination of step-temperature, step-power, and isothermal testing over the temperature interval between 10 and 80°C and power levels of 1 to 5 mW per facet. Our results show that the long-term degradation process is thermally accelerated, with a median activation energy of 1 eV and a standard deviation of 0.13 eV. By using these activation energies, in conjunction with our measurements of degradation rates, we can project laser performance to 10°C, i.e., system operating temperature. It is estimated that the median time to failure for “light bulb” operation at 10°C is over 2 × 107 hours; and with 98-percent probability it is greater than 5 × 106 hours. Hence, when viewed strictly in terms of light bulb sources of stimulated power, these 1.3-μm lasers have adequate life. In addition, other potential operational malfunctions are being investigated, and they do not seem to change our basic conclusion about the usefulness of these 1.3-μm lasers for submarine cable application.