Guāngxiān rùhù hòu, tiáozhìjiětiáoqì huànchéng le guāngmāo.
After fiber was installed, the modem was replaced with an ONT.
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调制解调器 is the textbook/literal term (modulator-demodulator) but in everyday speech people say 猫 - a phonetic loan from English 'modem'. Fiber-optic ONTs are nicknamed 光猫 ('optical cat'). The full 调制解调器 mostly survives in manuals and packaging.
