A New Fiber Optic Speed Record

Researchers at University College London (UCL) have set a new bandwidth record for fiber optic bandwidth transmission. They’ve been able to communicate through a fiber optic cable at over 178 terabits per second, or 178,000 gigabits per second. The research was done in collaboration with fiber optic firms Xtera and KDDI Research. The press release of the achieved speed claims this is 20% faster than the previously highest achieved speed.

The achieved speed has almost reached the Shannon limit, which defines the maximum amount of error-free data that can be sent over a communications channel. Perhaps the most impressive thing about the announcement was that UCL scientists achieved this speed over existing fiber optic cables and didn’t use pristine fiber installed in a laboratory.

The fast signal throughput was achieved by combining several techniques. First, the lasers use raman amplification, which involves injecting photons of lower energy into a high-frequency photon stream. This produces predictable photon scattering which can be tailored to the characteristics needed for optimally traveling through glass fiber.

The researchers also used Erbium-doped fiber amplifiers. To those who have forgotten the periodic table, erbium is a commonly found metal in nature with an atomic weight of 68. Erbium has a key characteristic needed for fiber optic amplifiers in that the metal efficiently amplifies light in the wavelengths used by fiber optic lasers.

Finally, the amplifiers used for the fast speeds used semiconductor optical amplifiers (SOA). These are diodes that have been treated with anti-reflection coatings so that the laser light signal can pass through with the least amount of scattering. The net result of all of these techniques is that the scientists were able to reduce the amount of light that is scattered during the transmission though a glass fiber cable, thus maximizing data throughput.

UCL also used a wider range of wavelengths than are normally used in fiber optics. Most fiber optic transmission technologies create empty buffers around each light bandwidth being used (much like we do with radio transmissions). The UCL scientists used all of the spectrum, without separation bands, and used several techniques to minimize interference between bands of light.

This short description of the technology being used is not meant to intimidate a non-technical reader, but rather show the level of complexity in today’s fiber optic technology. It’s a technology that we all take for granted, but which is far more complex than most people realize. Fiber optic technology might be the most lab-driven technology in daily use since the technology came from research labs and scientists have been steadily improving the technology for decades.

We’re not going to see multi-terabit lasers in regular use in our networks anytime soon, and that’s not the purpose of this kind of research. UCL says that the most immediate benefit of their research is that they can use some of these same techniques to improve the efficiency of existing fiber repeaters.

Depending upon the kind of glass being used and the spectrum utilized, current long-haul fiber technology requires having the signals amplified every 25 to 60 miles. That means a lot of amplifiers are needed for long-haul fiber routes between cities. Without amplification, the laser light signals get scattered to the point where they can’t be interpreted at the receiving end of the light transmission. As implied by their name, amplifiers boost the power of light signals, but their more important function is to reorder the light signals into the right format to keep the signal coherent.

Each amplification site adds to the latency in long-haul fiber routes since fibers must be spliced into amplifiers and passed through the amplifier electronics. The amplification process also introduces errors into the data stream, meaning some data has to be sent a second time. Each amplifier site must also be in powered and housed in a cooled hut or building. Reducing the number of amplifier sites would reduce the cost and the power requirement and increase the efficiency of long-haul fiber.

New Technology – Telecom and Computing Breakthroughs

The InternetToday I look at some breakthroughs that will result in better fiber networks and faster computers – all components needed to help our networks be faster and more efficient.

Increasing Fiber Capacity. A study from Bell Labs suggests that existing fiber networks could be made 40% more efficient by changing to IP transit routing. Today operators divvy up networks into discrete components. For example, the capacity on a given route may be segmented into distinct dedicated 100 Gig paths that are then used for various discrete purposes. This takes the available bandwidth on a given long-haul fiber and breaks it into pieces, much in the same manner as was done in the past with TDM technology to break data into T1s and DS3s.

The Bell Lab study suggests a significant improvement if the entire bandwidth on a given fiber is treated as one huge data pipe, much in the same manner as might be done with the WAN inside of a large business. This makes sense because there is always spare or unused capacity on each segment of the fiber’s bandwidth and putting it all together into one large pipe makes the spare capacity available. Currently Alcatel Lucent, Telefonica, and Deutsche Telekom are working on gear that will enable the concept.

Reducing Interference on Fiber. Researchers at University College London have developed a new set of techniques that reduce interference between different light wave frequencies on fiber. It is the accumulation of interference that requires optical repeaters to be placed on networks to refresh optical signals.

The research team took a fresh approach to how signals are generated onto fiber and pass the optical signals through a comb generator to create seven equidistantly-spaced and frequency-locked signals, each in the form of a 16 QAM super-channel. This reduces the number of different light signals on the fiber to these seven channels which drastically reduces the interference.

The results were spectacular and they were able to generate a signal that could travel without re-amplification for 5,890 kilometers, or 3,660 miles. This has immediate benefit for undersea cables since finding ways to repeat these signals is costly. But there are applications beyond long-haul fiber and the team is now looking at ways to use the dense super-channels for cable TV systems, cable modems, and Ethernet connections.

Faster Computer Chips. A research team at MIT has found a way to make multicore chips faster. Multicore chips contain more than one processor and are used today for intense computing needs in places like data centers and in supercomputers.

The improvement comes through the creation of a new scheduling technique they are calling CDCS (computation and data co-scheduling). This technique is a way to more efficiently distribute data flow and the timing of computations on the chips. The new algorithm they have developed allows data to be placed near to where calculations are performed, reducing the movement of data within the chip. This results in a 46% increase in computing capacity while also reducing power consumption by 36%. Consequently, this will reduce the need for cooling which is becoming a major concern and one of the biggest costs at data centers.

Faster Cellphones. Researchers at the University of Texas have found a way to double the speed at which cellphones and other wireless devices can send or receive data. The circuit they have developed will let the cellphone radio deploy in ‘full-duplex’ mode, meaning that the radio can make both send and receive signals at the same time.

Today a cellphone radio can do one or the other and your phone’s radio constantly flips between sending or receiving data. Radios have always done this so that the frequencies from the transmitting part of the phone, which are normally the stronger of the two signals, don’t interfere with and drown out the incoming signals.

The new circuit, which they are calling a circulator, can isolate the incoming and outgoing signals and acts as a filter to keep the two separate. Circulators have been is use for a long time in devices like radar, but they have required large, bulky magnets made from expensive rare earth metals. But the new circulator devised by the team does this same function using standard chip components.

This circulator is a tiny standalone device that can be added to any radio chip and it acts like a traffic manager to monitor and control the incoming and outgoing signals. This simple, new component is perfect for cellphones, but will benefit any two-way radio, such as WiFi routers. Since a lot of the power used in a cellphone goes to flipping between send and receive mode, this new technology ought to also provide a significant improvement to battery life.

Million-Fold Increase in Hard Drive Capacity? Researchers at the Naval Research Laboratory have developed a way to magnetize graphene, and this could lead to data storage devices with a million-time increase in storage per size of the device. Graphene is a 1-atom thick sheet of carbon which can be layered to make multi-dimensional stacked chips.

The scientists have been able to magnetize the graphene by sitting it on a layer of silicon and submerging it in a pool of cryogenic ammonia and lithium for about a minute. They then introduce hydrogen, which renders the graphene electromagnetic. The process is adjustable, and with an electron beam you can shave off hydrogen atoms and effectively write on the graphene chip. Today we already have terabyte flash drives. Anybody have a need for an exabyte flash drive?