About Optical Computers – part 2

Working Principle of Optical Computer

The working principle of Optical Computer is similar to the conventional computer except with some portions that performs functional operations in Optical mode. Photons are generated by LED’s, lasers and a variety of other devices. They can be used for encoding the data similar to electrons.

Design and implementation of Optical transistors is currently under progress with the ultimate aim of building Optical Computer. Multi design Optical transistors are being experimented with. A ninety degree rotating, polarizing screen can effectively block a light beam. Optical transistors are also made from dielectric materials that have the potential to act as polarizers. Optical logic gates are slightly challenging, but fundamentally possible. They would involve one control and multiple beams that would provide a correct logical output. 

Fig. 6 – (a) Optical Network on Chip (b) Photonic Chip on Circuit

Electrons have one superior advantage in that, silicon channels and copper wires can be turned and electrons would follow. This effect can be emulated in Optical Chips using Plasmonic Nano particles. They are used for turning corners and continue on their path without major power loss or electron conversions.

Most parts of an Optical chip resembles any other commercially found computer chip. Electrons are deployed in the parts that transform or process information. The interconnects however, have drastic changes. These interconnects are used for information shuttling between different chip areas. Instead of electron shuttling, which might slow down when interconnects heat up, light is shuttled. This is because light can be easily contained and has an advantage of less information loss during travel.

Researchers are hoping that this swift communication process might result in the development of exascale computers i.e. computers that perform billions of calculations every second, 1000 times more processing speed than current speediest systems.

Advantages of Optical Computer

The advantages of Optical Computer are:

·         Optical computer has several major advantages of high density, small size, low junction heating, high speed, dynamically scalable and reconfigurable into smaller/ larger networks/ topologies, massive parallel computing ability and AI applications.

·         Apart from speed, Optical interconnections have several advantages. They are impervious to electromagnetic interference and are not prone to electrical short circuits.

·         They offer low-loss transmission and large bandwidth for parallel communication of several channels.

·         Optical processing of data is inexpensive and much easier than the processing done on electronic components.

·         Since photons are not charged, they do not readily interact with one another as electrons. This adds another advantage in that, light beams pass through each other in full duplex operation.

·         Optical materials have greater accessibility and storage density than magnetic materials.

Disadvantages of Optical Computer

The disadvantages of Optical Computer are:

·         Manufacturing Photonic Crystals is challenging.

·         Computation is complex as it involves interaction of multiple signals.

·         Bulky in size.

Future of Optical Computing

We can see interesting developments in lasers and lights. These are taking over the electronics in our computers. Optical technology is currently being promoted for use in parallel processing, storage area networks, Optical Data Networks, Optical Switches, Biometric and Holographic storage devices at airports.

Processors now contain light detectors and tiny lasers that facilitate data transmission through Optical Fiber. Few companies are even developing Optical Processors that use Optical Switches and laser light to do the calculations. One of the foremost promoters ‘Intel’ is creating an Integrated Silicon Photonics link that is capable of transmitting 50 Gigabytes per second of uninterrupted information.

It is speculated that future computers would come without screens where information presentation is made through a hologram, in the air, and above the keyboard. This kind of technology is being made possible by the collaboration of researchers and industrial experts. Also, Optical technology’s most practical use i.e. the ‘Optical Networking business’ is predicted to reach 3.5 billion dollars from 1 billion currently. 

From <https://electricalfundablog.com/optical-computer/>

 

Optical Computing: Solving Problems at the Speed of Light

According to Moore’s law —actually more like a forecast, formulated in 1965 by Intel co-founder Gordon Moore— the number of transistors in a microprocessor doubles about every two years, boosting the power of the chips without increasing their energy consumption. For half a century, Moore’s prescient vision has presided over the spectacular progress made in the world of computing. However, by 2015, the engineer himself predicted that we are reaching a saturation point in current technology. Today, quantum computing holds out hope for a new technological leap, but there is another option on which many are pinning their hopes: optical computing, which replaces electronics (electrons) with light (photons).

The end of Moore’s law is a natural consequence of physics: to pack more transistors into the same space they have to be shrunk down, which increases their speed while simultaneously reducing their energy consumption. The miniaturisation of silicon transistors has succeeded in breaking the 7-nanometre barrier, which used to be considered the limit, but this reduction cannot continue indefinitely. And although more powerful systems can always be obtained by increasing the number of transistors, in doing so the processing speed will decrease and the heat of the chips will rise.

THE HYBRIDIZATION OF ELECTRONICS AND OPTICS

Hence the promise of optical computing: photons move at the speed of light, faster than electrons in a wire. Optical technology is also not a newcomer to our lives: the vast global traffic on the information highways today travels on fibre optic channels, and for years we have used optical readers to burn and read our CDs, DVDs and Blu-Ray discs. However, in the guts of our systems, the photons coming through the fibre optic cable must be converted into electrons in the microchips, and in turn these electrons must be converted to photons in the optical readers, slowing down the process.

The overhead view of a new beamsplitter for silicon photonics chips that is the size of one-fiftieth the width of a human hair. Credit: Dan Hixson/University of Utah College of Engineering

Thus, it can be said that our current technology is already a hybridization of electronics and optics. “In the near-term, it is pretty clear that hybrid optical-electronic systems will dominate,” Rajesh Menon, a computer engineer at the University of Utah, tells OpenMind. “For instance, the vast majority of communications data is channelled via photons, while almost all computation and logic is performed by electrons.” And according to Menon, “there are fundamental reasons for this division of labour,” because while less energy is needed to transmit information in the form of photons, the waves associated with the electrons are smaller; that is, the higher speed of photonic devices has as its counterpart a larger size.

This is why some experts see limitations in the penetration of optics in computing. For Caroline Ross, a materials science engineer at the Massachusetts Institute of Technology (MIT), “the most important near-term application [for optics] is communications — managing the flow of optical data from fibres to electronics.” The engineer, whose research produced an optical diode that facilitates this task, tells OpenMind that “the use of light for actual data processing itself is a bit further out.”

THE LASER TRANSISTOR

But although we are still far from the 100% optical microchip —a practical system capable of computing only by using photons— advances are increasing the involvement of photonics in computers. In 2004, University of Illinois researchers Milton Feng and Nick Holonyak Jr. developed the concept of the laser transistor, which replaces one of the two electrical outputs of normal transistors with a light signal in the form of a laser, providing a higher data rate.

For example, today it is not possible to use light for internal communication between different components of a computer, due to the equipment that would be necessary to convert the electrical signal to optical and vice versa; the laser transistor would make this possible. “Similar to transistor integrated circuits, we hope the transistor laser will be [used for] electro-optical integrated circuits for optical computing,” Feng told OpenMind. The co-author of this breakthrough is betting on optical over quantum computing, since it does not require the icy temperatures at which quantum superconductors must operate.

Graduate students Junyi Wu and Curtis Wang and Professor Milton Feng found that light stimulates switching speed in the transistor laser. Credit: L. Brian Stauffer

Proof of the interest in this type of system is the intense research in this field, which includes new materials capable of supporting photon-based computing. Among the challenges still to be met in order to obtain optical chips, Menon highlights the integration density of the components in order to reduce the size, an area in which his laboratory is a pioneer, as well as a “better understanding of light-matter interactions at the nanoscale.”

Despite all this, we shouldn’t be overly confident that a photonic laptop will one day reach the hands of consumers. “We don’t expect optical computing to supplant electronic general-purpose computing in the near term,” Mo Steinman, vice president of engineering at Lightelligence, a startup from the photonics lab run by Marin Soljačić at MIT, told OpenMind.

Present and future of photonics

However, the truth is that nowadays this type of computing already has its own niches. “Application-specific photonics is already here, particularly in data centres and more recently in machine learning,” says Menon. In fact, Artificial Intelligence (AI) neural networks are being touted as one of its great applications, with the potential to achieve 10 million times greater efficiency than electronic systems. “Statistical workloads such as those employed in AI algorithms are perfectly suited for optical computing,” says Steinman.

Thus, optical computing can solve very complex network optimization problems that would take centuries for classical computers. In Japan, the NTT company is building a huge optical computer that encloses five kilometres of fibre in a box the size of a room, and will be applied to complicated power or communications networks enhancement tasks.

A photonic integrated circuit. Credit: JonathanMarks

“Looking ahead, we believe we can leverage the ecosystem created by optical telecommunications in the areas of integrated circuit design, fabrication, and packaging, and optimize for the specific operating points required by optical computing,” Steinman predicts. However, he admits that moving from a prototype to full-scale manufacturing will be a difficult challenge.

In short, there are reasons for optimism about the development of optical computing, but without overestimating its possibilities: when computer scientist Dror Feitelson published his book Optical Computing (MIT Press) in 1988, there was talk of a new field that was already beginning to reach maturity. More than 30 years later, “optical computing is still more of a promise than a mainstream technology,” the author tells OpenMind. And the challenges still to be overcome are compounded by another stumbling block: technological inertia. Feitelson recalls the warning issued in those days by IBM researcher Robert Keyes: with the enormous experience and accumulated investment in electronics that we already know, “practically any other technology would be unable to catch up.”

From <https://www.bbvaopenmind.com/en/technology/future/optical-computing-solving-problems-at-the-speed-of-light/>

 Optical computers light up the horizon

 

Optical chips will power our future datacenters and supercomputers. Electronic chips can now have a layer of optical components, like lasers and switches, added to it, to increase their computing power. Credit: Martijn Heck, Aarhus University

Since their invention, computers have become faster and faster, as a result of our ability to increase the number of transistors on a processor chip.

Today, your smartphone is millions of times faster than the computers NASA used to put the first man on the moon in 1969. It even outperforms the most famous supercomputers from the 1990s. However, we are approaching the limits of this electronic technology, and now we see an interesting development: light and lasers are taking over electronics in computers.

Processors can now contain tiny lasers and light detectors, so they can send and receive data through small optical fibres, at speeds far exceeding the copper lines we use now. A few companies are even developing optical processors: chips that use laser light and optical switches, instead of currents and electronic transistors, to do calculations.

So, let us first take a closer look at why our current technology is running out of steam. And then, of course, answer the main question: when can you buy that optical computer?

Moore's Law is dying

Computers work with ones and zeros for all their calculations and transistors are the little switches that make that happen. Current processor chips, or integrated circuits, consist of billions of transistors. In 1965, Gordon Moore, founder of Intel, predicted that the number of transistors per chip would double every two years. This became known as Moore's Law, and after more than half a century, it is still alive. Well, it appears to be alive...

In fact, we are fast reaching the end of this scaling. Transistors are now approaching the size of an atom, which means that quantum mechanical effects are becoming a bottleneck. The electrons, which make up the current, can randomly disappear from such tiny electrical components, messing up the calculations.

Moreover, the newest technology, where transistors have a size of only five nanometers, is now so complex that it might become too expensive to improve. A semiconductor fabrication plant for this five-nanometer chip technology, to be operational in 2020, has already cost a steep 17 billion US dollars to build.

Computer processor chips have plateaued

Looking more closely, however, the performance growth in transistors has been declining. Remember the past, when every few years faster computers hit the market? From 10 MHz clock speed in the 80s, to 100 MHz in the 90s and 1 GHz in 2000? That has stopped, and computers have been stuck at about 4 GHz for over 10 years.

Of course with smart chip design, for example using parallel processing in multi-core processors, we can still increase the performance, so your computer still works faster, but this increased speed is not due to the transistors themselves.

And these gains come at a cost. All those cores on the processor need to communicate with each other, to share tasks, which consumes a lot of energy. So much so that the communication on and between chips is now responsible for more than half of the total power consumption of the computer.

Since computers are everywhere, in our smartphone and laptop, but also in datacenters and the internet, this energy consumption is actually a substantial amount of our carbon footprint.

For example, there are bold estimations that intense use of a smartphone connected to the Internet consumes the same amount of energy as a fridge. Surprising, right? Do not worry about your personal electricity bill, though, as this is the energy consumed by the datacenters and networks. And the number and use of smartphones and other wearable tech keeps growing.

Fear not: lasers to the rescue

So, how can we reduce the energy consumption of our computers and make them more sustainable? The answer becomes clear when we look at the Internet.

In the past, we used electrical signals, going through copper wires, to communicate. The optical fibre, guiding laser light, has revolutionised communications, and has made the Internet what it is today: Fast and extending across the entire world. You might even have fibre all the way to your home.

We are using the same idea for the next generation computers and servers. No longer will the chips be plugged in on motherboards with copper lines, but instead we will use optical waveguides. These can guide light, just like optical fibres, and are embedded into the motherboard. Small lasers and photodiodes are then used to generate and receive the data signal. In fact, companies like Microsoft are already considering this approach for their cloud servers.

Optical chips are already a reality

Now I know what you're thinking around about now:

"But wait a second, how will these chips communicate with each other using light? Aren't they built to generate an electrical current?"

Yes, they are. Or, at least, they were. But interestingly, silicon chips can be adapted to include transmitters and receivers for light, alongside the transistors.

Researchers from the Massachusetts Institute of Technology in the US have already achieved this, and have now started a company (Ayar Labs) to commercialise the technology.

Here at Aarhus University in Denmark we are thinking even further ahead: If chips can communicate with each other optically, using laser light, would it not also make sense that the communication on a chip—between cores and transistors—would benefit from optics?

We are doing exactly that. In collaboration with partners across Europe, we are figuring out whether we can make more energy-efficient memory by writing the bits and bytes using laser light, integrated on a chip. This is very exploratory research, but if we succeed, it could change future chip technology as early as 2030.

The future: optical computers on sale in five years?

So far so good, but there is a caveat: Even though optics are superior to electronics for communication, they are not very suitable for actually carrying out calculations. At least, when we think binary—in ones and zeros.

Here the human brain may hold a solution. We do not think in a binary way. Our brain is not digital, but analogue, and it makes calculations all the time.

Computer engineers are now realising the potential of such analogues, or brain-like, computing, and have created a new field of neuromorphic computing, where they try to mimic how the human brain works using electronic chips.

And in turns out that optics are an excellent choice for this new brain-like way of computing.

The same kind of technology used by MIT and our team, at Aarhus University, to create optical communications between and on silicon chips, can also be used to make such neuromorphic optical chips.

In fact, it has already been shown that such chips can do some basic speech recognition. And two start-ups in the US, Lightelligence and Lightmatter, have now taken up the challenge to realise such optical chips for artificial intelligence.

Optical chips are still some way behind electronic chips, but we're already seeing the results and this research could lead to a complete revolution in computer power. Maybe in five years from now we will see the first optical co-processors in supercomputers. These will be used for very specific tasks, such as the discovery of new pharmaceutical drugs.

But who knows what will follow after that? In ten years these chips might be used to detect and recognise objects in self-driving cars and autonomous drones. And when you are talking to Apple's Siri or Amazon's Echo, by then you might actually be speaking to an optical computer.

While the 20th century was the age of the electron, the 21st century is the age of the photon – of light. And the future shines bright.

 

From <https://phys.org/news/2018-03-optical-horizon.html>

 

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…till next post, bye-bye and take care.