WDM four-fiber ring with add/drop acousto-optic tunable filter and 4×4 optical switch

The WDM ring has been considered a cost-effective, reliable network architecture due to its features of bandwidth sharing and improved survivability. In a previously reported WDM ring network using transit tunable filters, a tunable filter was employed in an optical wavelength add/drop multiplexer because it is an effective component for reconfiguration in a WDM ring. However, the multiplexer, consisting of optical star couplers and convenient transit tunable filters, was very complex and generated excess signal loss. As the result, electrical regenerators were required to restore the signal-to-noise ratio. A four-port add/drop acousto-optic tunable filter (AOTF) is desirable to realize an optical add/drop multiplexer with simple configuration and low insertion loss. We propose a four-fiber WDM ring employing both add/drop AOTFs and 4×4 optical switches. The structure and performance of this ring are detailed