Hong Kong-listed optical communication stocks fell sharply in early trading, with Robotec (03757.HK) down more than 9.5%, Yangtze Optical Fibre and Cable (06869.HK) down more than 8%, InnoLight Technology (03308.HK) and Nagen Technology (09856.HK) down more than 8%, and Hygon Optics (01191.HK) down more than 7%.