Patent ID: 8548320

Claim:
A method for monitoring a wavelength-division multiplexed signal, comprising: generating from a first node, a first optical objective signal including a first objective wavelength λ o1 , generating from a second node, a second optical objective signal including a second objective wavelength λ o2 , and generating from a monitor, an optical guard signal including a guard wavelength λ g that is between λ o1 and λ o2 ; a central hub receiving the first optical objective signal, the second optical objective signal, and the optical guard signal; the central hub generating the wavelength-division multiplexed signal by wavelength-division multiplexing the first optical objective signal, the second optical objective signal, and the optical guard signal, wherein the wavelength-division multiplexed signal includes: a first multiplexed objective channel, a second multiplexed objective channel, and a multiplexed guard channel having a range of wavelengths between λ o1 and λ o2 ; receiving the wavelength-division multiplexed signal by the monitor; and detecting an error of the first multiplexed objective channel by determining an error of the multiplexed guard channel, determining the error includes comparing the multiplexed guard channel to the optical guard signal.