An optical add-drop multiplexer comprising: a splitter or combiner, the splitter arranged to split input optical power to a first filter and a second filter, the combiner arranged to combine optical power from a first filter and second filter; the first filter (142, 420) configured to filter a first band (B E, C) of wavelengths (λ E, λ C) of a communication spectrum for a first communication segment, the first band (B E, C) having a first spectral edge (E, E1) and wherein the first band comprises first guard band (B G) wavelengths (λ G) adjacent to the first spectral edge and two or more wavelengths (λ E, λ C) for carrying information residing spectrally adjacent to the first guard band wavelengths; and the second filter (142, 430) configured to filter a second band (B A, L) of wavelengths (λ A, λ L) of the communication spectrum for a second communication segment, the second band (B A, L) having a second spectral edge (E, E2) and wherein the second band comprises second guard band wavelengths (B G) adjacent to the second spectral edge and two or more wavelengths (λ A, λ L) for carrying information residing spectrally adjacent to the second guard band wavelengths, the second band (B A, L) overlapping the first band (B E, C) in an overlap band (B O) of wavelengths (A O), wherein the overlap band (B O) comprises common wavelengths (λ) between a spectral edge (E, E 1) of the first band (B E, C) of wavelengths (λ E, λ C) and a spectral edge (E, E 2) of the second band (B A, L) of wavelengths (λ A, λ L), the overlap band (B O) having a variable size; wherein the overlap band (B O) is fractionally divided between spectrally adjacent wavelengths (λ E, λ C) for carrying information of the first band (B E, C) and spectrally adjacent wavelengths (λ A, λ L) for carrying information of the second band (B A, L) such that the first band (B E, C) includes a first fraction of the overlap band (B O) of wavelengths (λ O) for the first communication segment and the second band (B A) includes the remaining fraction of the overlap band (B O) of wavelengths (λ O) for the second communication segment. a splitter or combiner, the splitter arranged to split input optical power to a first filter and a second filter, the combiner arranged to combine optical power from a first filter and second filter; the first filter (142, 420) configured to filter a first band (B E, C) of wavelengths (λ E, λ C) of a communication spectrum for a first communication segment, the first band (B E, C) having a first spectral edge (E, E1) and wherein the first band comprises first guard band (B G) wavelengths (λ G) adjacent to the first spectral edge and two or more wavelengths (λ E, λ C) for carrying information residing spectrally adjacent to the first guard band wavelengths; and the second filter (142, 430) configured to filter a second band (B A, L) of wavelengths (λ A, λ L) of the communication spectrum for a second communication segment, the second band (B A, L) having a second spectral edge (E, E2) and wherein the second band comprises second guard band wavelengths (B G) adjacent to the second spectral edge and two or more wavelengths (λ A, λ L) for carrying information residing spectrally adjacent to the second guard band wavelengths, the second band (B A, L) overlapping the first band (B E, C) in an overlap band (B O) of wavelengths (A O), wherein the overlap band (B O) comprises common wavelengths (λ) between a spectral edge (E, E 1) of the first band (B E, C) of wavelengths (λ E, λ C) and a spectral edge (E, E 2) of the second band (B A, L) of wavelengths (λ A, λ L), the overlap band (B O) having a variable size; wherein the overlap band (B O) is fractionally divided between spectrally adjacent wavelengths (λ E, λ C) for carrying information of the first band (B E, C) and spectrally adjacent wavelengths (λ A, λ L) for carrying information of the second band (B A, L) such that the first band (B E, C) includes a first fraction of the overlap band (B O) of wavelengths (λ O) for the first communication segment and the second band (B A) includes the remaining fraction of the overlap band (B O) of wavelengths (λ O) for the second communication segment.