Abstract: A scalable, reconfigurable, and cost-effective add/drop arrangement is provided which enables a wavelength division multiplexed (WDM) system to be upgraded to accommodate new or changing add/drop requirements without disruptions in existing service. The add/drop arrangement is based on a modular architecture wherein one or more modular optical routing devices are coupled in an optical fiber path to facilitate the selective adding/dropping of individual optical channels and to facilitate in-service upgrades without disrupting existing transmissions in the optical fiber path. In an exemplary embodiment, at least two directional optical transfer devices, such as optical circulators, are coupled to a drop path for dropping optical channels from the WDM signal, an add path for receiving optical channels to be added to the WDM signal, and a common path between the directional optical transfer devices.

Abstract: Automatic reduction of optical signal power supplied by an upstream network element by a prescribed amount is achieved by capturing and processing reflected optical energy that is generated within the optical fiber path as a result of a downstream fiber cut, open connector, or other potentially hazardous discontinuity. Generally, the power level of the reflected optical signal is detected and measured in the optical fiber path and the optical signal power supplied by the upstream network element is automatically reduced. The optical signal power may either be reduced by an amount corresponding to the measured reflected optical signal power or may be completely shut off until the faulty condition is resolved.