Hong Kong-listed optical communication stocks fell across the board, with Hygon Microelectronics (01191.HK) down more than 12%, InnoLight Technology (03308.HK) and Xizhi Technology-P (01879.HK) down more than 6%, Cambridge Technology (06166.HK) down more than 5%, and Huahong Grace Semiconductor (01347.HK) down nearly 5%.