Los Altos resident Stephanie Jensen, 50, was sentenced to four months in prison and fined $1.25 million last week, the latest Silicon Valley executive convicted for fraudulent stock-option backdating.

Jensen, who worked as human resources vice president at San Jose-based Brocade Communications Systems Inc., was accused of conspiring with CEO Gregory Reyes to hide the way in which Brocade employees received low-price stock options. Reyes was convicted in 2007 of fraudulent backdating, sentenced to more than a year in prison and fined $15 million. The FBI and the Securities and Exchange Commission carried out the investigation.

Backdating stock-option grants is legal when properly documented. When employees receive stock with an artificially lowered price, they score an instantaneous profit, increasing the company’s expense. Investigations of Brocade and other Silicon Valley companies have probed whether companies systematically concealed the backdating.