Patent ID: 6895142

Claim:
A branching unit A branching unit comprising: a first optical input for receiving optical signals, a second optical input for receiving optical signals, branching apparatus comprising a plurality of interconnected interleavers for separating component portions of optical signals input at the first optical input and for combining some of those separated optical signal component portions with other optical signals input at the second optical input so as to provide combined optical signals, a first optical output for outputting the combined optical signals, and a second optical output for outputting other of the separated optical signal component portions, wherein the branching apparatus further comprises at least one concatenated group of interleavers comprising: an initial drop interleaver having one optical input for receiving optical signals and two separate optical outputs each for outputting respective component portions of optical signals received thereby; and a terminal add interleaver having two separate optical inputs each for receiving optical signals and one optical output for outputting a combination of optical signals concurrently received at the two inputs thereof, wherein one optical output of the initial drop interleaver is in optical connection with one optical input of the terminal add interleaver of the concatenated group.