  Optical data center network architectures are becoming attractive because of
their low energy consumption, large bandwidth, and low cabling complexity.
In\cite{Xu1605:PODCA}, an AWGR-based passive optical data center architecture
(PODCA) is presented. Compared with other optical data center architectures,
e.g., DOS \cite{ye2010scalable}, Proteus \cite{singla2010proteus}, and Petabit
\cite{xia2010petabit}, PODCA can save up to 90$\%$ on power consumption and
88$\%$ in cost. Also, average latency can be low as 9 $\mu$s at close to
100$\%$ throughput. However, PODCA is not reconfigurable and cannot optimize
the network topology to dynamic traffic.
  In this paper, we present a novel, scalable and flexible reconfigurable
architecture called RODCA. RODCA is built on and augments PODCA with a flexible
localized intra-cluster optical network. With the reconfigurable intra-cluster
network, racks with mutually large traffic can be located within the same
cluster, and share the large bandwidth of the intra-cluster network. We present
an algorithm for DCN topology reconfiguration, and present simulation results
to demonstrate the effectiveness of reconfiguration.
