Patent ID: 6895186
Filing Date: 2005-05-17
Classification: H04J

Abstract:
1. A system for accessing a WDM bidirectional optical fiber ring network having a first network fiber for carrying WDM signals in a first direction and a second network fiber for carrying WDM signals in a second direction, each of the first and second network fibers for carrying up to W WDM signals each having a respective one of W distinct wavelengths, where W is a positive integer, the system comprising a network node coupled to a network access station having a transmitter and a receiver through transmitter access fiber means and receiver access fiber means, respectively, the transmitter for providing signals having respective ones of the W wavelengths, the receiver for receiving signals having respective ones of the W wavelengths, the network node intersecting the first and second network fibers and comprising a first and a second WADM each having a first input, a second input, a first output and a second output, for each one of the W wavelengths, λ, each of the first and second WADMs has a bar state, in which a signal having the wavelength λ received at the first input of the WADM is provided to the first output of the WADM, and a signal having the wavelength λ received at the second input of the WADM is provided at the second output of the WADM, for each one of the W wavelengths, λ, each one of the first and second WADMs has a cross state, in which a signal having the wavelength λ received at the first input of the WADM is provided at the second output of the WADM and a signal having the wavelength λ received at the second input of the WADM is provided at the first output of the WADM, wherein the first input of the first WADM is coupled to the transmitter access fiber means; the second input of the first WADM being coupled to receive signals on the first network fiber entering the network node; the first output of the first WADM is coupled to the first input of the second WADM; the second output-of the first WADM is coupled to provide signals on the first network fiber leaving the network node; the second input-of the second WADM is coupled to receive signals on the second network fiber entering the network node; the first output of the second WADM is coupled to the receiver access fiber means; and the second output of the second WADM being coupled to provide signals on the second network fiber leaving the network node, such that when both the first and second WADMs are in the bar state for the wavelength λ, a signal having the wavelength λ on the first network fiber entering the network node passes through the network node unchanged to the first network fiber leaving the network node, and a signal having the wavelength λ on the second network fiber entering the network node passes through the network node unchanged to the second network fiber leaving the network node; such that when for the wavelength λ the first WADM is in the cross state and the second WADM is in the bar state, a signal having the wavelength λ on the first network fiber entering the network node is routed to the receiver of the network access station, and a signal having the wavelength λ provided by the transmitter of the network access station is routed to the first network fiber leaving the network node, a signal having the wavelength λ on the second network fiber entering the network node passing through the network node unchanged to the second network fiber leaving the network node; and such that when for the wavelength λ the first WADM is in the bar state and the second WADM is in the cross state, a signal having the wavelength λ on the second network fiber entering the network node is routed to the receiver of the network access station, and a signal having the wavelength λ provided by the transmitter of the network access station is routed to the second network optical fiber leaving the network node, a signal having the wavelength λ on the first network fiber entering the network node passing through the network node unchanged to the first network fiber leaving the network node.