BOSTON, Mass., June 2 -- SpecTran Corp. expects its net sales to grow by more than 25 percent in 1999. The company predicts sales will increase at a compound annual rate of 12 to 15 percent through 2003, with earnings per share expected to grow at an equal or faster rate, said SpecTran chairman and CEO Charles Harrison. These financial projections include an anticipated doubling of sales and earnings of SpecTran's Specialty Optics subsidiary during the period in question.SpecTran attributes this year's growth in fiber demand to explosive Internet growth, increasing bandwidth requirements, and continued deregulation of the telecommunications industry. Harrison expects this increased demand to ease the downward pressure on standard fiber pricing, which was triggered in part by industry oversupply.