(Reuters) -Gorilla Glass maker Corning on Tuesday forecast fourth-quarter sales above analysts’ estimates, but revenue from its largest business unit that makes fiber optic products fell short of expectations.

Shares of the Apple supplier fell more than 7% in premarket trading after the results, though the stock is still up about 88% so far this year.

The company’s optical communications division, which accounts for nearly 40% of total revenue, recorded net sales of $1.65 billion for the third quarter, below analysts’ average estimate of $1.73 billion, according to LSEG data.

U.S. optical fiber companies Corning, OFS-Felite and Drake Communications have been pressured by slower network investment in China, where authorities in September imposed a 37.9% anti-dumping tariff on imports of

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