Disclosed is an optical coupler device, especially for monitoring purposes in an optical point-to-point transmission link, which includes a first, a second and a third optical port and is configured to transmit a first optical signal received at the first optical port to the second optical port and to transmit a second optical signal received at the second optical port to the first and third optical port according to a monitoring split ratio with respect to the optical power of the second optical signal, the first and second optical signal having a wavelength lying in a first optical band. The device is further configured to transmit a third and a fourth optical signal received at the third and the second optical port to the respective other optical port, the third and fourth optical signal having a wavelength lying in a second optical band. The device is controllable with respect to the monitoring split ratio and includes a control means adapted to receive a control signal. The control means controls the opt
