Power Systems of Electrical Engineering
Date of SubmissionOptical Interconnects
Optical interfaces refer to arrays of optoelectronic devices that is of the order of 1000 optical channels. Each of these channels run at a speed of approximately 1 Gigabit per second. This means that they offer an overall capacity of the same speed to any single integrated circuit. There are still unresolved issues in manufacturing processes, architectural design, packaging, and simulation. However, due to advanced technology, it is possible to understand its use in all commercial systems within a short period. One of its use is chip-to-chip communication (Mutig).
The Use optical methods in addressing chip-to-chip interconnection have been there for a long time. However, it is only until recently that the technology with a very good promise of commercial applications was discovered. This was due to the systematic shift from trying to come up with custom VSLI techniques that have inbuilt optoelectronic capability. Developers focused on developing methods allows the tight integration of parallel arrays of fabricated optoelectronic devices with standard foundry electronics (Mutig).
These optics have the capability of reducing energy for any irreversible communication that is at logic level signals and located inside digital processing machines. This is due to the fact that quantum sources and quantum detectors can perform a very effective impedance transformation, which matches the high impedance given by small devices and also the low impedance found in the electromagnetic propagation. As a result, all forms of communication should be optical except that of the intra-chip (Mutig).
The amount of information that flows in a simple digital electrical interconnection has a limit. The limit depend on interconnection aspect ratio. This limit is not affected by the design details at the electrical lines. The limit is scale invariant. This means that it is not dependent on the expansion or shrinking of the system. For the limit to be exceeded, there requires an additional multi-level modulation. An exceeded limit will pose a problem to a machine with high bandwidth. Optical interconnect can eliminate this problem because they usually they keep off from resistive losses that produce the limit (Kawai).
Limitation of Electrical Interconnects
The following limitations of electrical interconnect led to more research that resulted in the development of optical interconnects.
Electrical interconnects suffer frequency dependent loss. This makes them not suitable to be used over long distances. The loss is caused by dielectric absorption and the skin effect. Resistivity and the constant of proportionality are related. Therefore, copper interconnects resistivity depends on the fabrication technology only (Kawai).
The limit of aspect ratio is scale invariant. In addition to this, it applies equally to all band to band interconnects. This also extends to the Multichip-Module connection. In cases where the cross-section is fixed, the limit is not affected by the material that makes up the interconnects. One of the major reasons why fiber-optics replaced co-axial cables is aspect ratio limit. There is an increased attention due to dielectric absorption (Kawai).
Electric interconnects are not scale invariant. Furthermore, it is not affected by the change in the cross-section. An interconnect with a speed of 1 gigabit per second can only travel a distance of 1 meter. If a fibreglass interconnects is used, it can move up to 10 meters. To obtain a higher overall bandwidth, an individual is forced to increase the number of conductors used in the same cross-section (Kawai).
Kawai, Shigeru. Handbook Of Optical Interconnects. Boca Raton: CRC Press/Taylor & Francis Group, 2005. Print.
Mutig, Alex. High Speed Vcsels For Optical Interconnects. Berlin: Springer, 2011. Print.