  When circuits are set up and dismantled dynamically in elastic optical
networks, spectrum tends to become fragmented in the fiber links. The
fragmentation limits the available path choices and may lead to significant
blocking of connection requests. There are two types of fragmentation in the
network spectrum in the links due to contiguity constraints and over the paths
due to continuity. Study of fragmentation and its management is essential to
operate the networks efficiently. This paper proposes a vectored fragmentation
metric for characterizing the fragmentation, which covers both types of
fragmentation. We discuss the characteristics of this metric in both transient
and steady-state of the dynamic network. We also test the proposed metric for
connection requests granularity range, arrival rates and holding times, to
establish functionality of this metric. We also compare the link-based
fragmentation metric with our Vectored Fragmentation Metric to understand the
better representation.
