According to Photonics.org :
A new range of 635Â nm laser modules featuring a "near end-of-life detection" facility to warn operators of their impending failure will make their debut at LASER 2007. Photonic Products, a UK-based optoelectronics device manufacturer and laser diode specialist, says that it developed the PM-NEOLD laser-diode modules after a request by a client, and is now making them generally available.
"As a laser diode approaches the end of its operational life, its imminent failure is signalled by an increase in the current drawn by its drive circuitry," David McGinness technical sales manager told optics.org. "Typically, when the current draw reaches a value of 120% of its original operating value, the laser diode is considered to have reached its ‘near end-of-life’ condition."