Inside the Direct Broadcast Optical Interconnect
This animation shows an implementation of the DBOI technology for a 32-way free-space, broadcast optical interconnect. Data communication via modulated light with multiple elements can occur simultaneously since light is inherently non-blocking and has a much better real world bit error ratio (BER) than cabling. The active components of this sample interconnect are arranged in four sections to facilitate hot-swap maintenance with minimal usage disruption.
On the left side of the animation, the optical emitters and receivers are mounted on four identical circuit boards. Each of the four DBOI modules has eight emitters and 32 receivers mounted to a circuit board and a set of optical lenses. The emitters are evenly spaced around the perimeter and the receivers are grouped in the middle. Each of the 32 receivers is optically focused on a single emitter and each emitter is simultaneously seen by four different receivers in this example. Each of the four DBOI modules handles all the transmission and reception needs of eight processor or communication nodes.
Splitting and spreading light to make it stable
The emitter sends out a data-carrying collimated light beam to the splitting and spreading lens. These lenses redirect the light for the four intended optical receivers. The 4-way split light beam is also spread which allows exceptional resistance to vibration, temperature drift and external contaminants such as dust.
The split and spread light beam bounces off a mirror which is specially coated to maximize the reflectivity for the frequency of light used in the DBOI. The use of a mirror enables the DBOI to be one half as long and also allows emitters and receivers to be co-planar on a single circuit board.
Focus on the target
The reflected light beam passes through a focusing lens before it reaches its intended receiver. The focusing lens enables isolation of the signal reception to a specific receiver and increases the strength of the received optical signal. Precise lens manufacturing enables each receiver to only see its target emitter without the need for manual adjustment or focus in the manufacturing or field replacement processes.
Not shown in this animation are the control boards connected to the emitters and receivers. On the emitter side, the data communication is divided into packets with destination workgroup addresses. A workgroup can consist of a single destination or any combination up to the max number of nodes. When the data communication optical packet, or flit, is received by each of the four receivers in this sample implementation, the destination address is checked and the data is forwarded to the appropriate nodes. This mechanism allows data to be seen by all the DBOI receivers simultaneously. Each receiver filters and discards unintended communication data before it reaches the node it services.