Patent ID: 8107819

Claim:
An optical network device comprising: a control unit configured to generate a magnetic signal based on a control signal, the control signal being configured to provide information relating to a distance between the optical network device and an optical line termination; a light source configured to generate an input optical signal: a variable optical attenuator comprising: a first polarizer configured to generate a first polarized optical signal by transmitting a part of the input optical signal having a first polarization plane; a tunable polarization rotator configured to generate a second polarized optical signal by adjusting a polarization angle of the first polarized optical signal based on the magnetic signal; and a second polarizer configured to generate an output optical signal by transmitting a part of the second polarized optical signal having a second polarization plane; and an additional variable optical attenuator between the light source and the variable optical attenuator, the additional variable optical attenuator including an optical isolator configured to reduce reflected light from the variable optical attenuator, the reflected light being associated with the input optical signal.