Reconfigurable wireless data center network using free-space optics

1. A reconfigurable free-space optical inter-rack network, comprising:

a plurality of server racks, each including at least one switch mounted on a top thereof,

wherein each top-mounted switch includes a plurality of free-space-optic link connectors, each with a free-space optical connection to a free-space-optic link connector on another top-mounted switch;

a single ceiling mirror above the plurality of server racks that substantially covers the plurality of server racks, wherein the single ceiling mirror redirects optical connections between pairs of free-space-optic link connectors to provide a clear lines-of-sight between each pair of connected free-space-optic link connectors; and

a controller that preconfigures a free-space optical network connecting the plurality of server racks by establishing connections between pairs of free-space-optic link connectors, and that reconfigures connections between pairs of free-space-optic link connectors in response to network traffic demands and events,

wherein the free-space-optic link connector comprises a liquid crystal switchable mirror (SM) that is electrically controllable and that switches between a reflection mode and a transparent mode.

2. The network of claim 1 , wherein the controller preconfigures an alignment of each SM to maximize a dynamic bisection bandwidth of a set of all possible candidate links between pairs of SMs.

3. The method of claim 2 , wherein the dynamic bisection bandwidth is maximized by constructing an n-node random regular graph of degree mk, wherein n is a number of server racks, in is a number of top-mounted switch per rack, and k is a number of SMs per top-mounted switch,

grouping the mk edges on each node into m sets of k edges corresponding to each of the m top-mounted switches, and

for every edge connecting a pair of SMs (a, b), aligning one SM each of a and b towards each other.

4. A reconfigurable free-space optical inter-rack network, comprising:

a plurality of server racks, each including at least one switch mounted on a top thereof,

wherein each top-mounted switch includes a plurality of free-space-optic link connectors, each with a free-space optical connection to a free-space-optic link connector on another top-mounted switch;

a single ceiling mirror above the plurality of server racks that substantially covers the plurality of server racks, wherein the single ceiling mirror redirects optical connections between pairs of free-space-optic link connectors to provide a clear lines-of-sight between each pair of connected free-space-optic link connectors; and

a controller that preconfigures a free-space optical network connecting the plurality of server racks by establishing connections between pairs of free-space-optic link connectors, and that reconfigures connections between pairs of free-space-optic link connectors in response to network traffic demands and events,

wherein the free-space-optic link connector includes a mirror galvanometer (GM) that rotates around an axis on a plane of the mirror in response to an electric signal, and the controller preconfigures an orientation of each GM to maximize a dynamic bisection bandwidth of a set of all possible candidate links between pairs of GMs.

5. The network of claim 4 , wherein the dynamic bisection bandwidth is maximized by, for each top-mounted switch per rack,

randomly partitioning the plurality of server racks into disjoint blocks, wherein for each block B and top-mounted switch a∈B, there exists an orientation of each GM on an ith top-mounted switch of each rack such that all racks in B fall within a coverage cone of the GM,

creating a random block-level matching Mi over the blocks, and

for each edge (B 1 , B 2 )∈M i , orienting the GMs on each top-mounted switch i in each rack within block B 1 towards B 2 , wherein a GM on any top-mounted switch in B 1 covers all top-mounted switches on racks in B 2 .