Patent ID: 8107827

Claim:
An apparatus for receiving an optical signal which includes an optical carrier component and at least one information-bearing optical sideband in an optical frequency domain, the apparatus including: an optical filter arrangement having an optical input and at least first and second optical outputs, the optical signal being coupled to the optical input, wherein optical power in substantially only the optical carrier component is transmitted to said first optical output, and optical power in substantially only the optical sideband is transmitted to said second optical output; a first optical splitter, having an input coupled to said first optical output of the optical filter arrangement, which splits the optical power in the optical carrier component into two sub-components having first and second substantially orthogonal polarisation states, transmitted to corresponding first and second polarisation outputs; a second optical splitter having an input coupled to said second optical output of the optical filter arrangement to split the optical power in the optical sideband into first and second sideband power sub-components, transmitted to corresponding first and second optical splitter outputs; first and second optical coupling devices, each having at least two inputs and at least one output at which power from the two inputs is combined; a first input of said first optical coupling device being coupled to the first polarisation output, and a second input of the first optical coupling device being coupled to the first output of said second optical splitter; a first input of said second optical coupling device being coupled to the second polarisation output, and a second input of the second optical covering device being coupled to the second output of said second optical splitter; and at least first and second optical detectors coupled to corresponding ones of each said output of the first and second coupling devices, to generate received electrical signals corresponding with the detected optical signals.