NEW YORK, Dec. 7 -- Lucent Technologies plans to spin off another business as an independent company. The unit, to be called Agere Systems, will manufacture silicon chips and optical components such as lasers. Earlier this year, Lucent spun off Avaya, a bigger but slower-growing business that is a producer of office telephone systems.The spin off will be completed by the end of the first quarter of 2001, said Lucent. Lucent will sell up to 20 percent of Agere through an initial public offering of stock. The remaining shares of Agere would be distributed to Lucent shareholders during the summer.