Author Archives: mathscinotes

I have spent some time lately talking to people about laser failure characteristics. Most electronic component reliability modeling is done using the exponential probability distribution, which assumes the components have a constant failure rate and there is no wear-out mechanism. It turns out that lasers have a wear-out mechanism, which means the exponential probability distribution is not appropriate. Laser failure rates are usually modeled by a lognormal probability distribution, as are the failure rates of brakes (Figure 1) and incandescent light bulbs. These components have reliabilities that are dominated by wear-out mechanisms that accelerate when damage to a small region grows exponentially. A good example would be a hard spot on a brake pad that becomes hot during braking relative to the rest of the pad. This hard spot tends grow quickly because the heat generated during braking concentrates there. Continue reading →