The Fair Trade Commission will likely impose surcharges totaling around ¥16 billion on about 10 fiber-optic cable parts makers for operating a cartel for devices ordered by the two regional phone units of NTT Corp., sources said.

The watchdog has informed Sumitomo Electric Industries Ltd., Furukawa Electric Co., Fujikura Ltd. and SWCC Showa Cable Systems Co. of its intention to levy the huge surcharge and order an end to their collusion, the sources said.

The four companies are suspected of having the lead role in forming the cartel.

The FTC searched around 10 companies last June, including Advanced Cable Systems Corp. and Hitachi Cable Ltd., on suspicion they had been running a cartel since February 2005 to dole out orders from NTT East Corp. and NTT West Corp. for parts like fiber-optic cable connectors and to determine their cost, according to the sources.

The two NTT companies actively promote household use of fiber-optic cables, which offer the highest Internet access speeds.

The domestic market for fiber-optic cables and their associated parts is estimated at roughly ¥48.5 billion. Orders from NTT East and NTT West account for about 70 percent of the market.