Light Peak Technology

Introduction

       We are living in an age of connectivity. Think of any sort of information, and it can be transferred to us within no time; be it audio, video or any other form of data. when we are talking about transferring data between our computer and the other peripherals, the first and foremost standard comes to our mind is Universal Serial Bus (USB). It is a medium speed serial data addressable bus system which carry large amount of data to a relatively short distance (up to 5m).The present version USB 3.0 promises to provide theoretical speed of up to 5Gbps.
Is that enough for out tech savy generation????





    Intel has unveiled a new inter-operable standard called LIGHT PEAK. This technology can transfer data between computers and the peripherals at the speed of 10Gbps in both the directions with maximum range of 100m (much higher than USB or any other standard). They also have the potential to scale its speed high up to 100Gbps in near future. Light Peak is the code name for a new high-speed optical cable technology designed to connect electronic devices to each other. Light Peak is basically an optical cable interface designed to connect devices in peripheral bus. It is being developed as a single universal replacement for the current buses such as SCSI, SATA, USB, FireWire, PCI express, and HDMI etc in an attempt to reduce the proliferation of ports on computers. Fiber-optic cabling is not new, but Intel executives believe Light Peak will make it cheap enough and small enough to be incorporated into consumer electronics.

    With light peak, the bandwidth would tremendously increase, multiple protocols could be run over single longer and thinner cable. The prototype system featured two motherboard controllers that both supported two bidirectional buses at the same time, wired to four external connectors. Intel has stated that Light Peak has the performance to drive everything from storage to displays to networking, and it can maintain those speeds over 100 meter runs.

Why is it required?

     Over the years we've used different ports for peripherals in computers. Older computers have special ports just for accessories like keyboards, mice, printers and monitors. With older computers, we have to install a special computer card on the motherboard if wanted to add other peripherals like joysticks and game-pads.While USB (Universal Serial Bus) didn't eliminate all special ports, it did cut down their number. Today, peripherals like keyboards, mice, printers and webcams are available as USB accessories. The ports are hot-pluggable, meaning you can connect or disconnect them at any time. They're also interchangeable in that you don't always have to plug each device into a specific USB port. But USB has its limitations.One of those limitations is speed. The USB 2.0 standard transmits data at 480 megabits per second (Mbps). That's fast enough for accessories like keyboards and mice to work smoothly but not fast enough for high-bandwidth accessories like computer monitors. The USB 3.0 standard increases the speed to 4.8 gigabits per second (Gbps), which is 10 times faster than USB 2.0, but the computer industry has been slow to adopt USB 3.0.Intel's its own answer to transferring data at high speeds using a standardized format is called Light Peak. Intel representatives say it has the potential to transmit data at more than 20 times the speed of USB 3.0. And as the name suggests, it will do this through the medium of light.


     In the near future, people would be using more and more electrical devices such as HD devices, MIDs and many more and user experience would depend on the huge volume of data capturing, transfer, storage, and reconstruction. But existing electrical cable technology is approaching the practical limit for higher bandwidth and longer distance, due to the signal degradation caused by electro-magnetic interference (EMI) and signal integrity issues.Higher bandwidth can be achieved by sending the signals down with more wires, but apparently this approach increases cost, power and difficulty of PCB layout, which explains why serial links such as SATA, SAS, and USB are becoming the mainstream. However optical communications do not create EMI because there communication is done with the help of photons rather than electrons, thus allowing higher bandwidth and longer distances. Besides, optical technology also allows for small form factors and longer, thinner cables.





Where We Reached?

    Is it ready for implementation!!!!Light Peak, announced in 2009, was originally designed to use fiber optics to transmit data among systems and devices, but the initial builds will be based on copper.For the majority of application today, copper is good, But data transmission is much faster over fiber optics, which will increasingly used by vendors in Light Peak implementations.Intel has said Light Peak technology would use light to speed up data transmission between mobile devices and products including storage, networking and audio devices. It would transfer data at bandwidths starting at 10 gigabits per second over distances of up to 100 meters.But with copper wires, the speed and range of data transmission may not be as great.PCs today are linked to external devices using connectors like USB,USB 3.0 already has a traction in the market.There could be co-existence, with USB, display and networking protocols running on top of Light Peak.



Merits

1) One Port to Rule Them All
The idea behind a technology like Light Peak is that it's going to replace all the formats we currently use such as USB, Fire Wire and all the other stuff you've ever at one time connected to your computer. This is all in hopes of cutting down the number of ports needed on your computer, and hopefully to create a new standard that external drives and other devices can use to connect.
 

2) Unbelievably Fast Transfer
USB is pretty much the format used for device connections. Then there is Fire Wire, USB 2.0, Fire Wire 800, USB 3.0 … you get the idea. The reason this happened was increased bandwidth needs. More technologies came, and pretty soon there was a mess of this cable and that cable for each particular device we wanted to connect to our computers. Light Peak is offering high bandwidth at 10Gbps, and can possibly be taken up to 100Gbps over the next decade, according to Intel's website. They also say that it can transfer a full-length Blu-Ray movie in under 30 seconds.
 

3) Can Lead to Smaller, Thinner Notebooks, Tablets, Etc.
This single port is as small as the rumored Apple port, it will reduce the size of many of the devices we use today. This technology can offer high enough bandwidth to transfer data to various devices without breaking a sweat. Even with two or three of these ports, it would take up less space than two USB ports, FireWire, Ethernet, etc. Of course we would probably need some sort of splitter to connect our various devices, but even that may just be part of the transition phase as manufacturers adopt the technology.

Areas of Improvement

1) Adoption Rate May Be Slow
This is always a bit of a concern for those who buy early. What if people are slow to pick up a new format? If consumers don't bite, manufacturers don't use it. If manufacturers don't use it, consumers don't want it. That vicious cycle. USB 1.1 was released in 1998, but even that seemed to take a while to become a household name. Of course having a computer in the 90s didn't almost seem like a requirement.

2) New Plugs, New Peripherals, New This, New That
This is also part of that transition phase mentioned above. While the result over the course of a few years may be a single does-it-all connection, it will take a while before all devices and peripherals start using it regularly. That's going to be the not-so-fun part. Most of us don't like spending money, especially on unproven technology.

Optical Fiber Communication

History of optical fiber communication

Introduction

   In this twenty first century, the era of ‘Information technology’ , There are two umbrella technologies that revolutionized communication,They are wireless communication and optical communcation. wireless communication has the advantage of reaching anywhere and everywhere but limited by capacity. Optical communication gifted with its enormous capacity was limited by its less reach. the combination of these technologies made a significant impact in all sorts of life.

   Optical fiber communication plays a vital role in the development of high quality and high-speed telecommunication systems. Today, optical fibers are not only used in telecommunication links but also used in the Internet and local area networks (LAN) to achieve high signaling rates.

Historical perspective of optical communication

   The use of light for transmitting information from one place to another place is a very old technique. In 800 BC., the Greeks used fire and smoke signals for sending information like victory in a war, alertting against enemy, call for help, etc. Mostly only one type of signal was conveyed. During the second century B.C. optical signals were encoded using signaling lamps so that any message could be sent. There was no development in optical communication till the end of the 18th century. The speed of the optical communication link was limited due to the requirement of line of sight transmission paths, the human eye as the receiver and unreliable nature of transmission paths affected by atmospheric effects such as fog and rain. In 1791, Chappe from France developed the semaphore for telecommunication on land. But that was also with limited information transfer. In 1835, Samuel Morse invented the telegraph and the era of electrical communications started throughout the world.

   The use of wire cables for the transmission of Morse coded signals was implemented in 1844. In 1872, Alexander Graham Bell proposed the photo phone with a diaphragm giving speech transmission over a distance of 200 m. But within four years, Graham Bell had changed the photophone into telephone using electrical current for transmission of speech signals. In 1878, the first telephone exchange was installed at New Haven. Meanwhile, Hertz discovered radio waves in 1887. Marconi demonstrated radio communication without using wires in 1895. 

   Using modulation techniques, the signals were transmitted over a long distance using radio waves and microwaves as the carrier. During the middle of the twentieth century, it was realized that an increase of several orders of magnitude of bit rate distance product would be possible if optical waves were used as the carrier.The information carrying capacity of telegraphy is about hundred times lesser than a telephony. Even though the high-speed coaxial systems were evaluated during 1975, they had smaller repeater spacing. Microwaves are used in modern communication systems with the increased bit rate distance product. However, a coherent optical carrier like laser will have more information carrying capacity.

   So the communication engineers were interested in optical communication using lasers in an effective manner from 1960 onwards. A new era in optical communication started after the invention of laser in 1960 by Maiman. The light waves from the laser, a coherent source of light waves having high intensity, high monochromaticity and high directionality with less divergence, are used as carrier waves capable of carrying large amount of information compared with radio waves and microwaves. Subsequently H M Patel, an Indian electrical engineer designed and fabricated a CO2 laser. 

   Optical communication systems use high carrier frequencies(~100 THz) in the visible or near-infrared region of the electromagnetic spectrum. They are sometimes called light wave systems to distinguish them from microwave systems, whose carrier frequency is typically smaller by five orders of magnitude (∼1 GHz). Fiber-optic communication systems are lightwave systems that employ optical fibers for information transmission. Such systems have been deployed worldwide since 1980 and have indeed revolutionized the technology behind telecommunications. Indeed, the lightwave technology, together with microelectronics, is believed to be a major factor in the advent of the “information age.” 

The birth of fiber optic systems

   To guide light in a waveguide, initially metallic and non-metallic wave guides were fabricated.But they have enormous losses. So they were not suitable for telecommunication. Tyndall discovered that through optical fibers, light could be transmitted by the phenomenon of total internal reflection. During 1950s, the optical fibers with large diameter of about 1 or 2 millimetre were used in endoscopes to see the inner parts of the human body.

   Optical fibers can provide a much more reliable and versatile optical channel than the atmosphere, Kao and Hockham published a paper about the optical fiber communication system in 1966. But the fibers produced an enormous loss of 1000 dB/km. But in the atmosphere, there is a loss of few dB/km. Immediately Kao and his fellow workers realized that these high losses were a result of impurities in the fiber material. Using a pure silica fiber these losses were reduced to 20 dB/km in 1970 by Kapron, Keck and Maurer. At this attenuation loss, repeater spacing for optical fiber links become comparable to those of copper cable systems. Thus the optical fiber communication system became an engineering reality.

Total Internal Reflection

   Consider a ray of light traveling from a medium of higher refractive index to a medium of lower refractive index.then the angle of refraction will be always greater than the angle of incidence as shown in the figure. so if we keep on increasing the incident angle then at a particular point the refracted wave just graces through the medium boundary,that is the angle of refraction will be 90 degree. the incident angle for which the refracted ray just graces through the boundary is called critical angle. any ray which incidents at the boundary beyond the critical angle will be totally internally reflected back.

  

Snells law:

n1 sin i = n2 sin r;

n1        = refractive index of medium with higher refractive index

n2        = refractive index of medium with lower refractive index

n1 > n2 for TIR to take place,

at TIR r = 90 degree,

ie sin r =1. 

sin i = n2/n1,where i is called the critical angle.

Different types of fibers

   There are different type of fibers available.We know that the light or the optical signals are guided through the silica glass fibers by total internal reflection. A typical glass fiber consists of a central core glass (50μm) surrounded by a cladding made of a glass of slightly lower refractive index than the core’s refractive index. The overall diameter of the fiber is about 125 to 200 μm. Cladding is necessary to provide proper light guidance i.e. to retain the light energy within the core as well as to provide high mechanical strength and safety to the core from scratches. Based on the refractive index profile we have two types of fibers (a) Step index fiber (b)Graded index fiber.






(a) Step index fiber: In the step index fiber, the refractive index of the core is uniform throughout and undergoes an abrupt or step change at the core cladding boundary. The light rays propagating through the fiber are in the form of meridional rays which will cross the fiber axis during every reflection at the core cladding boundary and are propagating in a zig-zag manner


(b) Graded index fiber : In the graded index fiber, the refractive index of the core is made to vary in the parabolic manner such that the maximum value of refractive index is at the centre of the core. The light rays propagating through it are in the form of skew rays or helical rays which will not cross the fiber axis at any time and are propagating around the fiber axis in a helical (or) spiral manner