Super Monitor Design for Fast Link Failure Localization in All-Optical Networks

An m-cycle is an optical loop-back pre-cross connection of a supervisory wavelength. In a cycle-based link failure detection scheme, a monitor transmits supervisory signals onto the m-cycle, receives them back, and compares with the one sent for fault detection. In this paper, we propose the notion of super monitor for cutting down the hardware cost of monitors. Instead of having a dedicated monitor for each m-cycle, a super monitor is placed at the junction of a set of m-cycles. Supervisory signals from a single laser source are split simultaneously onto multiple m-cycles using an optical splitter. As the cost of a monitor is usually dominated by the laser, co-locating conventional monitors to form a super monitor for cost reduction makes sense. To this end, we formulate the problem of determining the optimal number of super monitors as well as their locations as an add-on feature of any existing cycle-based link failure detection scheme. We call it monitor placement problem. We follow a two-step approach for its solution, where in the first step, we enumerate each candidate cycle-set (i.e., a set of m-cycles where the super monitor can be placed); and in the second step, a simple integer linear programming (ILP) is constructed for placing super monitors at some candidate cycle sets. Numerical results show that by properly placing super monitors, considerable amount of monitoring cost can be saved.