| 摘要 |
A network interface unit includes an input for receiving downstream signals from an optical fiber, an optical pathway leading from the input, a laser connected to the optical pathway for transmitting upstream signals in a first wavelength band, and a receiver for receiving downstream signals in a second wavelength band that doesn't overlap with the first wavelength band. A first filter is provided for filtering signals in a third wavelength band from the optical pathway before signals in the third wavelength band reach the receiver, and a second filter is provided between the input and the laser for filtering signals in a fourth wavelength band from the optical pathway, the fourth wavelength band not overlapping with the first wavelength band or the third wavelength band, and an arrangement is also provided for preventing processing of the fourth wavelength band downstream of the second filter. Also a filtering method.
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