1. A Concept: Transmitting and Receiving Fiber Optic Signals with Petabit per Second Capacity
Tom Juliano
ECE-641
February 20, 2003

2. Three Main System Components
Signal Generation:
Carbon Nanotubes
Tunable Laser
Bioluminescent Materials
Signal Transmission:
Erbium-Doped Silica Fibers or Other
Signal Detection
Silicon and Other Semiconductor Multilayer Photodetector Array

3. Carbon Nanotubes for Signal Generation
These nanotubes can be selectively doped to change the value of their electronic band gap.
Nanotubes are known for their ability to act as fast switches in the MHz-GHz range.

4. Carbon Nanotubes for Signal Generation
They can be grown on an array in discrete locations
One or more of these squares could couple into a fiber, because each square’s area can be made on a small scale
Bundle of Nanotubes that are selectively doped

5. Nanotube Oriented Growth
It has been shown that nanotubes can be selectively and reliably grown on SiO2 in predetermined orientations.
B. Wei et al. Nature, 416, (04 Apr 2002)

6. Nanotubes as Emitters
Nanotubes can be used as field emitters in flat panel displays (<8 mm thick) [Samsung]

7. Transmission of the Signal
Wavelengths of 850, 1310, or 1550 nm should be used to minimize signal attenuation losses
Silica fibers doped with erbium should be used at 1550 nm

8. Transmission of the Signal
If indices of refraction (1.4 and 1.395) and  (1550 nm) are chosen as reasonable values, then fiber diameter is about 5 m.
Main problem is the generation of power from source. About 15% of the power is lost to the cladding.
Chromatic signal distortion is not significant compared to signal attenuation. For a 5 nm wavelength difference in generated signal, a 50 km fiber length is permissible.

9. Detection of the Signal
Technology (X3) is currently patented by Foveon for use in digital cameras to increase pixel resolution
Production of many different elements (millions) on the array is possible with one chip

10. Absorption of Silicon at Different Wavelengths

11. Transmission of the Signal
Multiple layers may be made, instead of just three. The shortest wavelength will penetrate to the shallowest depth, and the longest will penetrate to the deepest. In this example, one signal may have 6 permissible values instead of 2.

12. Transmission of the Signal
Lithography may be used to fabricate such device arrays
Silicon is the substrate, but germanium or another semiconductor may be heteroepitaxially grown on the surface by chemical vapor deposition, followed by another layer of silicon, etc. Interconnects must be employed.

13. Conclusions
Sufficient power generation and losses are the main issue over long distances, so this may be the most feasible over short distances, such as between computer components or LANs.
The bitrate for a single step index fiber for normal conditions is about 30 Gbit/s (only in theory). However, by comparison, a system using 100,000 of these fibers with base 6 logic can produce a theoretical bitrate of 7.68 Pbit/s!
It is not likely that these speeds could actually be realized, but the idea of multiple fibers transmitting signals with simplified generation and detection is the same.