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It seems that there are some misconceptions/ misunderstandings about laser diode lifetime ie. MTTF/MTBF ratings.
I saw a post in another thread earlier today where people were discussing this, but it wasn't the thread topic and I cannot find the thread now.
Anyway, someone had thought that since their laser or the diode in their laser was rated for 5000 or 8000 hours that it meant that the laser/diode would work for that amount of time; this is not so. Many may in fact last up to or perhaps even longer than the rated, but many will not even last a fraction of that amount of time. MTBF/MTTF numbers are a statistic that are good for determining product quality when many thousands or millions of units are considered, but they mean very little to how long an individual unit will live. For the person buying laser the number can be used for instance to compare the quality of one diode to another in that a diode with a 8000hr MTBF on average will be of higher quality than one of 5000hr MTBF; but it doesn't mean much more.
Here's a link that describes this somewhat and there's more on the web, just do a google search.
Using MTBF and Time Dependent Reliability for disks : Ramblings from Richard's Ranch
One of the interesting things that is used to describe MTBF is that in the USA, the death rate of children between the ages of 5 to 14 is 0.0208% per year, this would equal an MTBF of 4,807 years for these kids.
This article was written about MTBF in disk drives, but it applies to all electronics or anything that uses MTBF as a quality metric.
I saw a post in another thread earlier today where people were discussing this, but it wasn't the thread topic and I cannot find the thread now.
Anyway, someone had thought that since their laser or the diode in their laser was rated for 5000 or 8000 hours that it meant that the laser/diode would work for that amount of time; this is not so. Many may in fact last up to or perhaps even longer than the rated, but many will not even last a fraction of that amount of time. MTBF/MTTF numbers are a statistic that are good for determining product quality when many thousands or millions of units are considered, but they mean very little to how long an individual unit will live. For the person buying laser the number can be used for instance to compare the quality of one diode to another in that a diode with a 8000hr MTBF on average will be of higher quality than one of 5000hr MTBF; but it doesn't mean much more.
Here's a link that describes this somewhat and there's more on the web, just do a google search.
Using MTBF and Time Dependent Reliability for disks : Ramblings from Richard's Ranch
One of the interesting things that is used to describe MTBF is that in the USA, the death rate of children between the ages of 5 to 14 is 0.0208% per year, this would equal an MTBF of 4,807 years for these kids.
This article was written about MTBF in disk drives, but it applies to all electronics or anything that uses MTBF as a quality metric.
