Optical devices and methods for regulating optical channel signals with specified wavelengths are disclosed. According to one aspect of the present invention, a number of variable optical apparatuses are employed. Each of the variable optical apparatuses includes a first and a second optical channel module, both configured at a wavelength _i. Each of the variable optical apparatuses further includes an optical regulator (i.e. a neutral density filter controlled by a stepper motor) coupled between the first and second optical channel modules. When signals with different wavelengths arrive, only the signal with the wavelength _i will transmit through the first optical channel module and the rest are reflected off. The transmitted signal is regulated (i.e. attenuated or strengthened) accordingly by the optical regulator before transmitting through the second optical channel module. Hence, the signals with different wavelengths can be respectively regulated by one of the variable optical apparatuses.