Patent ID: 7327960

Claim:
A receiver transponder to be used in an optical add and drop node connected in a two-fiber network, comprising: first and second optoelectric converters for converting received optical signals to electric signals and each having an optical input terminal and an output terminal, the first optoelectric converter having its optical input terminal connected to an optical fiber carrying light signals from a first direction for receiving the light signals and for converting them to electric signals on a first output terminal and the second optoelectric converter having its optical input terminal connected to an optical fiber carrying light signals from a second direction opposite the first direction for receiving the light signals and for converting them to electric signals on a second output terminal, each optoelectric converter generating an output signal carrying light signal power information and a supervisory channel on a monitor output terminal different from the output terminal of the optoelectric converter; an electronic switch having two signal input terminals, a signal output terminal and a control input terminal, each of the two optoelectric converters connected with the first and second output terminals respectively to one of the two signal input terminals of the electronic switch, a signal on the control input terminal controlling the electronic switch to select one of the signal input terminals from which a signal existing on the selected one of the signal input terminals is transferred to the signal output terminal of the electronic switch, whereby the direction from which information on a channel terminated in the optical add and drop node is to be received can be chosen; an electronic reshaping circuit having an input terminal and an output terminal the input terminal connected to the signal output terminal of the electronic switch for reshaping a signal output from the electronic switch; wherein the electronic reshaping circuit is also arranged to clean the supervisory channel from the signal output from the electronic switch.