Superconducting Technology Assessment - nitrd

There is another option to employ DWDM which might be considered however, if, as discussed above, it is possible
to make an electrically and optically efficient 50 Gbps modulator capable of operating at the intermediate temperature.
In this case, a light source placed at 300K that is a laser whose output is not a single wavelength, but a comb of
wavelengths, could be used. Such lasers have been built for research purposes and are now commercially available
from at least one vendor. In this case, the laser light is transmitted by a single fiber to the intermediate temperature,
where it is demultiplexed to an array of identical modulators, and remultiplexed onto a single output fiber to 300K.
This technique would eliminate the need to control the wavelength of very large numbers of individual lasers.
There would likely be a major wallplug power advantage here since the electrical power to modulate the light at
40K would then be less than the power needed to generate it there. Figure 5 shows a schematic representation of
a DWDM system which employs only 3 fibers between cryogenic components and room temperature.
DETECTOR
ARRAY
CPU
OUTPUT
LINE
DRIVERS
IDEAL DATA TRANSMISSION CONCEPT
4K 40K ARRAY 300K
DEMUX
64 x 50 Gbps
ELECTRICAL
RIBBON
CABLE
64λ x 50 Gbps
MODULATOR
ARRAY
DEMUX
MUX
DEMUX
Figure 5. A 3-fiber, 64-wavelength, 50-Gbps DWDM System for bidirectional transmission totaling 6.4 Tbps between a superconductive processor
at 4 K and high speed mass memory at 300K. Optical connections are shown in red, electrical in black.
To accomplish at least one of these options by 2010 appears to be feasible, given the current state of the technology
and the estimated cost to achieve the desired goals by then. The development of more easily manufacturable
technologies, such as organic glasses or polymers, for application by 2012 should receive special attention because
of cost issues. As discussed earlier, the final choice will be determined as much by systems engineering and
economic decisions as by the availability of any of the required technologies. Each of the options should be
examined in detail in the initial phase of the study, with a commitment to the final development of a manufacturing
capability to follow.
MUX
MODULATOR
FROM MEMORY
64λ−CW
64λ x 50 Gbps
DEMUX
FREQUENCY
COMB
LASER
FREQUENCY
COMB
LASER
DETECTOR
ARRAY
TO MEMORY
221