Finisar's ( FNSR) blowout quarter shines a brighter light on the fiber optic-networking sector.The Sunnyvale, Calif., optical component maker posted pro forma net income of $7.7 million, or 3 cents a share, on $93.5 million in sales. Those numbers, released after the market closed Thursday, compare with an adjusted net loss of $7.8 million, or 4 cents a share, on sales of $63.4 million a year ago. The sudden swing to profit and estimate-beating 8% sequential top-line growth marks a big turnaround for the optical parts maker, which has struggled through the lean years of telecom collapse. Fans say the company's forecast for sustained profits and 20% annual growth targets prove Finisar -- and perhaps the beaten-down optical networking industry along with it -- may have finally put the rockier times behind it. "This one-quarter surge in profitability has been more than three years in the making," writes Needham analyst John Harmon, who upgraded the stock to a strong buy Friday. Finisar's recent history is strikingly similar to the rebuilding and diversification efforts of telecom component maker JDSU ( JDSU). Last year, JDSU sold some of its manufacturing operations and put together a string of acquisitions including Acterna, a network test and measurement outfit. The moves to get more products like lasers and power components, along with new sales from an adjacent network-testing market, underlie a big bet that optical network construction will soon revive. So far, it seems the bulls are on to something. The big performance from Finisar, combined with solid numbers and upward guidance from optical networking shop Ciena ( CIEN) Thursday, helped boost shares in the sector. Finisar jumped 89 cents, or 31%, to $3.80 in early trading Friday. Meanwhile JDSU rose 23 cents to $3.72 and is up 40% since the beginning of the year.