 HUNTSVILLE, Ala.--BUSINESS WIRE--ADTRAN, Inc. NASDAQ: ADTN ADTRAN or the Company, today announced certain preliminary financial results for the third quarter ended September 30, 2021. All figures in this release are approximate due to the preliminary nature of the announcement. For the third quarter, revenue is expected to be 138 million, gross margin is expected to be 34.5, non-GAAP gross margin is expected to be 34.6, operating loss is expected to be 10.1 million and non-GAAP op 