Sycamore Networks Inc. agreed to buy Sirocco Systems Inc. for $2.88 billion in stock, its second effort to snap up a maker of fiber-optic equipment used in cities. Sycamore, whose products carry and switch data and voice traffic on networks made of glass fibers, will pay 28 million shares for Sirocco, a closely held, 16-month-old startup with no sales. It expects to complete the purchase in about 60 days.