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Content
Thunderbolt Technology
Anitta Varghese Koluthara
Computer Science Department Rajagiri College of Computer Science Cochin, Kerala [email protected]
Abstract— Thunderbolt code named Light Peak is Intel’s new high-speed optical cable technology designed to connect electronic devices to each other in a peripheral bus. Thunderbolt delivers high bandwidth starting at 10 GB/s with the potential ability to scale to 100 GB/s over the next decade. At 10 GB/s, you could transfer a full-length Blu-Ray movie in less than 30 seconds. It is intended as a single universal replacement for current buses such as SCSI, SATA, USB, FireWire, PCI Express and HDMI. In comparison to these buses, Thunderbolt is much faster, longer ranged, smaller, and more flexible in terms of protocol support. Thunderbolt also has the ability to run multiple protocols simultaneously over a single cable, enabling the technology to connect devices such as peripherals, displays, disk drives, docking stations, and more. Thunderbolt was developed by Intel and brought to market with technical collaboration from Apple Inc. In late February 2011, Apple introduced its Mac Book Pro laptop computers with Intel’s light peak technology and announced its commercial name as Thunderbolt. It can be added to existing products with relative ease. Keywords-component; formatting; style; styling; insert (key words)
controllers that both supported two bidirectional buses at the same time, wired to four external connectors. Each pair of optical cables from the controllers is led to a connector, where power is added through separate wiring. The physical connector used on the prototype system looks similar to the existing USB or FireWire connectors. Intel has stated that Thunderbolt has the performance to drive everything from storage to displays to networking, and it can maintain those speeds over 100 meter runs. II. THUNDERBOLT TECHNOLOGY
I.
INTRODUCTION
The present era is the era of connectivity. 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 to5Gbps.But Intel has unveiled a new interoperable standard called Thunderbolt which 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) and has potential to scale its speed high up to 100Gbps in near future. Thunderbolt is basically an optical cable interface, in an attempt to reduce the proliferation of ports on computers. Fiber-optic cabling is not new, but Intel executives believe Thunderbolt will make it cheap enough and small enough to be incorporated into consumer electronics at a price point that consumers and manufacturers will accept. Thus with Thunderbolt, the bandwidth would tremendously increase, multiple protocols could be run over single longer and thinner cable. The prototype system featured two motherboard
Thunderbolt basically provides a standard low cost, high bandwidth optical-based interconnect, it supports multiple existing I/O protocols and smooth transition between them, it supports wide range of devices, connect to many devices with the same cable. Thunderbolt consists of a controller chip and optical module that would be included in platform to support this technology. The optical module performs the task of electricity to light conversion and vice versa, using miniature lasers and photo detectors. The controller chip provides protocol switching to support multiple protocols over single cable. Thunderbolt cable contains a pair of optical fibers that are used for upstream and downstream traffic to provide speed of about 10Gbps in both the directions and power is added through separate wiring. Earlier USB performed very well in this direction but increased bandwidth demand and high performance has led to development of new more efficient technologies. Combining the high bandwidth of optical fiber with Intel’s practice to multiplex multiple protocols over a single fiber, optical technology may change the landscape of IO system design in the future. As advantages over existing systems, they also note that a system using Thunderbolt will have fewer and smaller connectors, longer and thinner cables, higher bandwidth, and can run multiple protocols on a single cable. It’s possible that most of the legacy IO protocols can be tunneled by optical-capable protocols, so some of the legacy IO interfaces can be converged to one single optical interface, significantly simplifying the form factor design of computers. This change in IO system will definitely affect the design of systems. The ultimate goal of system architects is to make a balanced and efficient system, on both power and cost grounds. III.
COMPONENT OVERVIEW
Light Peak consists of a controller chip and an optical module that would be included in platforms supporting this
Identify applicable sponsor/s here. If no sponsors, delete this text box. (sponsors)
technology. The optical module performs the conversion from electricity to light and vice versa, using miniature lasers (VCSELs) and photo detectors. The main components are: A. Fiber optics cable B.Optical module C.Controller chip
1. VCSEL (light source) 2. Optical modulator 3. PIN diode (light detector)
A. Fiber Optics Cable The fiber used here is a silica-based optical fiber structure which consists of a cladding layer with a lower refractive index than the fiber core it surrounds. This refractive index difference causes a total internal reflection, which guides the propagating light through the fiber core with an attenuation less than 20 dB/km necessary threshold to make fiber optics a viable transmission technology. The fiber is coated with a thin primary coating to protect the inner glass fiber from environmental hazards. Thunderbolt is based on Laser-optimized Multi-mode fiber (LOMF). By laser optimized it just means that the fiber was designed to be used with lasers. The internal diameter of each Thunderbolt fiber is 62.5 microns. The beam expander molded into the lens expands that to 700 microns, so that dusts usually around 100 microns may interrupt the beam partially but the connection will still work. The beam expander also compensates for distortion or movement in the connector after been used for a while. Thunderbolt fiber has a 3-micron coating to prevent cracking, it can be bent to a radius of 3mm and it won’t break. It is mixed with copper wires for power and fiber optic cables for data. B. Optical Module The optical module does the function of converting optical signals into electrical signals and vice versa. This module contains an array of VCSEL (vertical cavity surface emitting laser). This consists of:
1.VCSEL VCSELs are semiconductor lasers, more specifically laser diodes with a monolithic laser resonator, where the emitted light leaves the device in a direction perpendicular to the chip surface. The laser resonator consists of two distributed Bragg reflector (DBR) mirrors parallel to the wafer surface with an active region consisting of one or more quantum wells for the laser light generation in between. The planar DBR-mirrors consist of layers with alternating high and low refractive indices. Each layer has a thickness of a quarter of the laser wavelength in the material, yielding intensity reflectivity above 99%. VCSELs has low-cost potential because the devices are completed and tested at the wafer level for material quality and processing purposes and a matrix VCSEL is capable of delivering high power( up to few watts).Thunderbolt Technology VCSELs have low threshold current value, low temperature sensitivity, high transmission speed, high fiber coupling efficiency and circular and low divergence output beam as compared to edge emitters.VCSELs for wavelengths from 650 nm to 1300 nm are typically based on gallium arsenide(GaAs) wafers with DBRs formed from GaAs and aluminum gallium arsenide (AlxGa(1-x)As). The current is confined in an oxide VCSEL by oxidizing the material around the aperture of the VCSEL. As a result in the oxide VCSEL, the current path is confined by the ion implant and the oxide aperture. The wavelength of VCSELs may be tuned, within the gain band of the active region, by adjusting the thickness of the reflector layers. 2. Optical Modulator In optical networks, binary digital modulation is typically used, namely on (light on) and off (no light) to transmit data. These semiconductor laser devices generate output light intensity which is proportional to
the current applied to them, therefore making them suitable for modulation to transmit data. Modulation schemes can be divided into two main categories: a direct and an external modulation. In a direct modulation scheme, modulation of the input current to the semiconductor laser directly modulates its output optical signal since the output optical power is proportional to the drive current. In an external modulation scheme, the semiconductor laser is operating in a Continuous-Wave (CW) mode at a fixed operating point. An electrical drive signal is applied to an optical modulator, which is external to the laser. Consequently, the applied drive signal modulates the laser output light on and off without affecting the laser operation. Block diagram of a typical external modulator
a Cross bar switching unit which switches the various protocols from light peak ports (LPK) to their respective protocol adapter. Secondly LPK Ports and Protocol Adapter ports which connect down to PC using any standard and diverging it their respective protocol through protocol adapter. The Host controller is typically multi protocol and has multiple ports with a software interface unit and is optimized for host side implementation whereas the peripheral controller could be single port and single protocol-based and is optimized for particular usage. This is because of this controller chip that different protocols get identified and transmitted correctly. API (Application programming interface) helps to determine the different protocols. It places the FIS (Flag Identification Symbol) packets in the memory, the controller access these packets from the memory and send these packets to the destination over the optical link. The multi-protocol capability the controller implements is an innovative new technology that will enable new usage models like flexible system designs and thinner form factors, media creation and connectivity, faster media transfer and cable simplification. IV. TODAYS CHALLENGES
Typical external modulator consists of an optical splitter a material called lithiumniiabate (LiNbO3)-whose refractive index varies with the applied electric field and an optical combiner. The input light enters the external modulator via the input fiber. The light is first splits into two fibers using an optical splitter. The top fiber path travels through a length of LiNbO3crystal. The light in the bottom fiber experiences a fixed delay. After the light travels through the lithiumniobate crystal and the fixed length of fiber, an optical combiner merges the two fiber paths. The light travels through identical path legs .By applying an electric field to the material, its refractive index changes. If the time delays through the fixed fiber and the LiNbO3crystal is equal, the light will be in phase when it reaches the output optical combiner. Due to the nature of light, since the light in both legs are in phase, they will constructively add to form the maximum possible output .The refractive index and the speed of light change as the applied voltage changes. When the speed changes enough to delay the light by half of one wavelength, the light will add destructively, yielding a minimum possible output. C.CONTROLLER CHIP The heart of Thunderbolt is an Intel-designed controller chip that handles the protocols, along with an optical module that converts electrical signals to photons and vice versa. Basic implementation unit of Thunderbolt Controller contains, firstly
In the coming 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 printed circuit board(PCB) layout. However optical communications do not create EMI by using photonics rather than electrons, thus allowing higher bandwidth and longer distances. Besides, optical technology also allows for small form factors and longer, thinner cables. The USB connectors on the smaller devices like mobile phones have to use mini-USB or microUSB to save on the space taken up by the wiring and electricity through wire creates electric field interference, but light do not create EMI since it rely over photonics. Optical connecters can carry extremely narrow beams of light and fiber can be thinner because more streams can pass through glass or plastic passages. Each fiber is only 125 microns wide. In the present scenario, the devices are getting smaller, thinner, and lighter but present connecting standards seems to hinder in their performance being to thicker and stiffer. So vendors turn over to new technologies providing much better performance and Thunderbolt seems to be providing a good solution. Different protocols demands for different connectors leading to too many connectors and cables. But in Thunderbolt there is the Thunderbolt protocol and the native protocols such as PCIExpress, Display Port, USB or whatever might be running on it. The native protocols run basically on top of the Thunderbolt protocol. But the Thunderbolt protocol defines the speed. The protocol is running at 10 gigabits per second. So, if the native protocols that are running on to profit are also running at 10 gigabits per second, or something close to that, then the effective bandwidth for a device on the other end would be equivalent to that 10Gbps. Thus, it can be said that
presently we demand for the devices and technologies that provides much higher bandwidth , more flexible designs, thinner form factor and new and better usage models and much simpler and easier in terms of connectivity’s. Thus Thunderbolt seems to be providing a good solution to the problems existing with the copper connectors and provides a good platform for the high performance system. V. DATA TRANSFER SPEED COMPARISION
VI.
THUNDERBOLT V/S USB 3.0 THUNDERBOL T
USB 3.0
9 Copper Wires
Optical Fiber Cable
A. Wireless Network The slowest is wireless. For example, Wireless N (802.11n) can reach 160 Mb/s in the real world. Thunderbolt is about 60 times faster. Faster wireless standards will come out, but nothing even close to what a good cable can provide. B. Ethernet Moving on to other Ethernet type connections, Apple first used Gigabit Ethernet on the "Mystic “Power Mac G4 in 2000. It gives a full 1 GB/s. The fastest Ethernet on the market is 10 Gigabit Ethernet (10GBase-T), and 100 Gigabit Ethernet is under development. You won't find 10G Ethernet on many computers. The standard also makes use of fiber optic cable to achieve these transfer rates. C. C.USB 3.0 The latest USB 3.0 connectors are starting to make an appearance. We see that at best it will be only half the speed of Thunderbolt. USB 3.0 is rated at 4.8 GB/s. Of course, theoretical and actual are two different things. In the past USB was unable to deliver more than about two-thirds of theoretical speed. D. FireWire FireWire was an important competitor to USB, but it has been losing popularity. Still, the FireWire standard is still progressing. FireWire S3200 is planned to reach 3.2 GB/s. That keeps it comparable to USB 3.0, but still much slower than Thunderbolt. I doubt we'll see many devices that use it. E. Hard Drives SATA 6 GB/s Hard drives need to be speedy, and a new SATA protocol was recently released, SATA 6 Gb/s.As the name implies, it can go 6 GB/s. The nice thing with this protocol is it remains compatible with older systems and hard drives. You do need to have the right motherboard to take advantage of the latest speed increase. F. HDMI and Display Port The newest video protocols, HDMI and Display Port, are both ready to transfer HD video content and huge blocks of data if all the wires are used together. HDMI version 1.3 and higher will transfer at 10.2 GB/s, while Display Port can go up to 10.8 Gb/s. These are slightly better than Thunderbolt, but they are mostly designed for video. No one is pushing the data transfer rates of these protocols.
Speed-3 Gb/sec
Speed-10 Gb/sec
Only USB Protocol
Universal
VII.
ADVANTAGES
The Thunderbolt optical modules are physically much smaller than those of telecom grade. The optical modules are designed to be much lower cost and higher performance. Thunderbolt can send and receive data at 10 billion bits per second. The thin optical fiber will enable Thunderbolt to transfer data over very thin, flexible cables. Unlike electrical cables, Thunderbolt do not faces the problem of EMI, thus can be used up to 100m. Thunderbolt also has the ability to run multiple protocols simultaneously over a single cable, enabling the technology to connect devices such as docking stations, displays, disk drives, and more. The data transfer is bidirectional in nature thus enabling devices to transfer simultaneously. Quality of service implementation. No Operating System (OS) changes required. It also supports another feature known as Hot-swapping which means the PC needs not be shut down and restarted to attach or remove a peripheral. Enables I/O performance for the next generation. Supports multiple existing I/O protocols over a single cable and smooth transition for today’s existing electrical I/O protocols. Can connect to more devices with the same cable, or to combo devices such as docking stations.
CONCLUSION
Thunderbolt is a high-speed, multi-protocol interconnect for innovative and emerging client usage models, that complements other existing interconnects. Thunderbolt is the name for a new high-speed optical cable technology designed to connect electronic devices to each other. Thunderbolt delivers high bandwidth starting at 10 GB/s with the potential ability to scale to 100 GB/s over the next decade. Thunderbolt allows for smaller connectors and longer, thinner, and more flexible cables than currently possible. . Thunderbolt also has the ability to run multiple protocols simultaneously over a single cable, enabling the technology to connect devices such as peripherals, displays, disk drives, docking stations, and more. Intel is working with the optical component
manufacturers to make Thunderbolt components ready to ship in this year. Thunderbolt is complementary to existing I/O technologies, as it enables them to run together on a single cable at higher speeds. At the present time, Intel has conducted three successful public demonstrations of the Thunderbolt technology and confirmed that the first Thunderbolt-enabled PCs should begin shipping soon. The goal of this new developing technology is to build a high-bandwidth, faultresilient, low-cost network that can deliver performance isolation across applications. The basic approach to achieve this target is to integrate low-radix switches into server platform and interconnect severs directly using multipath topologies. Thus if the question WHY THUNDERBOLT?? arises, then the answer would be because it is cheaper as it incorporates cheaper switching components, provide better bandwidth allocation and performance isolation, uses flexible topologies, integrate multiple protocol devices on to one cable. Intel CEO Paul Otellini called Thunderbolt the I/O performance and connection for the next generation, and confirmed that both Nokia and Sony have publicly announced their support.VictorKrutul, director of Intel’s optical development team and founder of the Thunderbolt program, is even more effusive, calling Thunderbolt the biggest thing to happen to the optical industry ever, or at least since the creation of the laser.
REFERENCES [1]SreenivasAddagatla, Mark Shaw, SuyashSinha and Prashant Chandra, AmeyaS.Varde, MichaelGrinkrug, “Direct Network Prototype Leveraging Light Peak Technology”, 18thIEEE Symposium on High Performance Interconnects,2010 [2] Jason Ziller and Victor Krutul, “A New Optical Technology-Light Peak” IntelTechnology Journal, Volume 8 [3]Wooten, E. L., “A Review of Lithium Niobate Modulators for Fiber-OpticCommunications Systems” [4] http:// en.wikipedia.org/wiki/Light_Peak [5]http://en.wikipedia.org/wiki/Light_Peak [6]http://news.cnet.com/8301-13924_3- 20025559-64.html [7]http://www.lightpeakinfo.com [8]http://www.technewsworld.com/story/68231.html [9]http://optics.or g/indepth/1/3/6 [10]http://arstechnica.com/apple/news/2009/09/appleinspiration-behind- light-peak-optical[11]http://www.lightwaveonline.com/about-us/lightwavecurrent-issue/Intel-plots-Light[12] http://Peak- interconnect-revolution.html
Anitta Varghese Koluthara
Computer Science Department Rajagiri College of Computer Science Cochin, Kerala [email protected]
Abstract— Thunderbolt code named Light Peak is Intel’s new high-speed optical cable technology designed to connect electronic devices to each other in a peripheral bus. Thunderbolt delivers high bandwidth starting at 10 GB/s with the potential ability to scale to 100 GB/s over the next decade. At 10 GB/s, you could transfer a full-length Blu-Ray movie in less than 30 seconds. It is intended as a single universal replacement for current buses such as SCSI, SATA, USB, FireWire, PCI Express and HDMI. In comparison to these buses, Thunderbolt is much faster, longer ranged, smaller, and more flexible in terms of protocol support. Thunderbolt also has the ability to run multiple protocols simultaneously over a single cable, enabling the technology to connect devices such as peripherals, displays, disk drives, docking stations, and more. Thunderbolt was developed by Intel and brought to market with technical collaboration from Apple Inc. In late February 2011, Apple introduced its Mac Book Pro laptop computers with Intel’s light peak technology and announced its commercial name as Thunderbolt. It can be added to existing products with relative ease. Keywords-component; formatting; style; styling; insert (key words)
controllers that both supported two bidirectional buses at the same time, wired to four external connectors. Each pair of optical cables from the controllers is led to a connector, where power is added through separate wiring. The physical connector used on the prototype system looks similar to the existing USB or FireWire connectors. Intel has stated that Thunderbolt has the performance to drive everything from storage to displays to networking, and it can maintain those speeds over 100 meter runs. II. THUNDERBOLT TECHNOLOGY
I.
INTRODUCTION
The present era is the era of connectivity. 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 to5Gbps.But Intel has unveiled a new interoperable standard called Thunderbolt which 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) and has potential to scale its speed high up to 100Gbps in near future. Thunderbolt is basically an optical cable interface, in an attempt to reduce the proliferation of ports on computers. Fiber-optic cabling is not new, but Intel executives believe Thunderbolt will make it cheap enough and small enough to be incorporated into consumer electronics at a price point that consumers and manufacturers will accept. Thus with Thunderbolt, the bandwidth would tremendously increase, multiple protocols could be run over single longer and thinner cable. The prototype system featured two motherboard
Thunderbolt basically provides a standard low cost, high bandwidth optical-based interconnect, it supports multiple existing I/O protocols and smooth transition between them, it supports wide range of devices, connect to many devices with the same cable. Thunderbolt consists of a controller chip and optical module that would be included in platform to support this technology. The optical module performs the task of electricity to light conversion and vice versa, using miniature lasers and photo detectors. The controller chip provides protocol switching to support multiple protocols over single cable. Thunderbolt cable contains a pair of optical fibers that are used for upstream and downstream traffic to provide speed of about 10Gbps in both the directions and power is added through separate wiring. Earlier USB performed very well in this direction but increased bandwidth demand and high performance has led to development of new more efficient technologies. Combining the high bandwidth of optical fiber with Intel’s practice to multiplex multiple protocols over a single fiber, optical technology may change the landscape of IO system design in the future. As advantages over existing systems, they also note that a system using Thunderbolt will have fewer and smaller connectors, longer and thinner cables, higher bandwidth, and can run multiple protocols on a single cable. It’s possible that most of the legacy IO protocols can be tunneled by optical-capable protocols, so some of the legacy IO interfaces can be converged to one single optical interface, significantly simplifying the form factor design of computers. This change in IO system will definitely affect the design of systems. The ultimate goal of system architects is to make a balanced and efficient system, on both power and cost grounds. III.
COMPONENT OVERVIEW
Light Peak consists of a controller chip and an optical module that would be included in platforms supporting this
Identify applicable sponsor/s here. If no sponsors, delete this text box. (sponsors)
technology. The optical module performs the conversion from electricity to light and vice versa, using miniature lasers (VCSELs) and photo detectors. The main components are: A. Fiber optics cable B.Optical module C.Controller chip
1. VCSEL (light source) 2. Optical modulator 3. PIN diode (light detector)
A. Fiber Optics Cable The fiber used here is a silica-based optical fiber structure which consists of a cladding layer with a lower refractive index than the fiber core it surrounds. This refractive index difference causes a total internal reflection, which guides the propagating light through the fiber core with an attenuation less than 20 dB/km necessary threshold to make fiber optics a viable transmission technology. The fiber is coated with a thin primary coating to protect the inner glass fiber from environmental hazards. Thunderbolt is based on Laser-optimized Multi-mode fiber (LOMF). By laser optimized it just means that the fiber was designed to be used with lasers. The internal diameter of each Thunderbolt fiber is 62.5 microns. The beam expander molded into the lens expands that to 700 microns, so that dusts usually around 100 microns may interrupt the beam partially but the connection will still work. The beam expander also compensates for distortion or movement in the connector after been used for a while. Thunderbolt fiber has a 3-micron coating to prevent cracking, it can be bent to a radius of 3mm and it won’t break. It is mixed with copper wires for power and fiber optic cables for data. B. Optical Module The optical module does the function of converting optical signals into electrical signals and vice versa. This module contains an array of VCSEL (vertical cavity surface emitting laser). This consists of:
1.VCSEL VCSELs are semiconductor lasers, more specifically laser diodes with a monolithic laser resonator, where the emitted light leaves the device in a direction perpendicular to the chip surface. The laser resonator consists of two distributed Bragg reflector (DBR) mirrors parallel to the wafer surface with an active region consisting of one or more quantum wells for the laser light generation in between. The planar DBR-mirrors consist of layers with alternating high and low refractive indices. Each layer has a thickness of a quarter of the laser wavelength in the material, yielding intensity reflectivity above 99%. VCSELs has low-cost potential because the devices are completed and tested at the wafer level for material quality and processing purposes and a matrix VCSEL is capable of delivering high power( up to few watts).Thunderbolt Technology VCSELs have low threshold current value, low temperature sensitivity, high transmission speed, high fiber coupling efficiency and circular and low divergence output beam as compared to edge emitters.VCSELs for wavelengths from 650 nm to 1300 nm are typically based on gallium arsenide(GaAs) wafers with DBRs formed from GaAs and aluminum gallium arsenide (AlxGa(1-x)As). The current is confined in an oxide VCSEL by oxidizing the material around the aperture of the VCSEL. As a result in the oxide VCSEL, the current path is confined by the ion implant and the oxide aperture. The wavelength of VCSELs may be tuned, within the gain band of the active region, by adjusting the thickness of the reflector layers. 2. Optical Modulator In optical networks, binary digital modulation is typically used, namely on (light on) and off (no light) to transmit data. These semiconductor laser devices generate output light intensity which is proportional to
the current applied to them, therefore making them suitable for modulation to transmit data. Modulation schemes can be divided into two main categories: a direct and an external modulation. In a direct modulation scheme, modulation of the input current to the semiconductor laser directly modulates its output optical signal since the output optical power is proportional to the drive current. In an external modulation scheme, the semiconductor laser is operating in a Continuous-Wave (CW) mode at a fixed operating point. An electrical drive signal is applied to an optical modulator, which is external to the laser. Consequently, the applied drive signal modulates the laser output light on and off without affecting the laser operation. Block diagram of a typical external modulator
a Cross bar switching unit which switches the various protocols from light peak ports (LPK) to their respective protocol adapter. Secondly LPK Ports and Protocol Adapter ports which connect down to PC using any standard and diverging it their respective protocol through protocol adapter. The Host controller is typically multi protocol and has multiple ports with a software interface unit and is optimized for host side implementation whereas the peripheral controller could be single port and single protocol-based and is optimized for particular usage. This is because of this controller chip that different protocols get identified and transmitted correctly. API (Application programming interface) helps to determine the different protocols. It places the FIS (Flag Identification Symbol) packets in the memory, the controller access these packets from the memory and send these packets to the destination over the optical link. The multi-protocol capability the controller implements is an innovative new technology that will enable new usage models like flexible system designs and thinner form factors, media creation and connectivity, faster media transfer and cable simplification. IV. TODAYS CHALLENGES
Typical external modulator consists of an optical splitter a material called lithiumniiabate (LiNbO3)-whose refractive index varies with the applied electric field and an optical combiner. The input light enters the external modulator via the input fiber. The light is first splits into two fibers using an optical splitter. The top fiber path travels through a length of LiNbO3crystal. The light in the bottom fiber experiences a fixed delay. After the light travels through the lithiumniobate crystal and the fixed length of fiber, an optical combiner merges the two fiber paths. The light travels through identical path legs .By applying an electric field to the material, its refractive index changes. If the time delays through the fixed fiber and the LiNbO3crystal is equal, the light will be in phase when it reaches the output optical combiner. Due to the nature of light, since the light in both legs are in phase, they will constructively add to form the maximum possible output .The refractive index and the speed of light change as the applied voltage changes. When the speed changes enough to delay the light by half of one wavelength, the light will add destructively, yielding a minimum possible output. C.CONTROLLER CHIP The heart of Thunderbolt is an Intel-designed controller chip that handles the protocols, along with an optical module that converts electrical signals to photons and vice versa. Basic implementation unit of Thunderbolt Controller contains, firstly
In the coming 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 printed circuit board(PCB) layout. However optical communications do not create EMI by using photonics rather than electrons, thus allowing higher bandwidth and longer distances. Besides, optical technology also allows for small form factors and longer, thinner cables. The USB connectors on the smaller devices like mobile phones have to use mini-USB or microUSB to save on the space taken up by the wiring and electricity through wire creates electric field interference, but light do not create EMI since it rely over photonics. Optical connecters can carry extremely narrow beams of light and fiber can be thinner because more streams can pass through glass or plastic passages. Each fiber is only 125 microns wide. In the present scenario, the devices are getting smaller, thinner, and lighter but present connecting standards seems to hinder in their performance being to thicker and stiffer. So vendors turn over to new technologies providing much better performance and Thunderbolt seems to be providing a good solution. Different protocols demands for different connectors leading to too many connectors and cables. But in Thunderbolt there is the Thunderbolt protocol and the native protocols such as PCIExpress, Display Port, USB or whatever might be running on it. The native protocols run basically on top of the Thunderbolt protocol. But the Thunderbolt protocol defines the speed. The protocol is running at 10 gigabits per second. So, if the native protocols that are running on to profit are also running at 10 gigabits per second, or something close to that, then the effective bandwidth for a device on the other end would be equivalent to that 10Gbps. Thus, it can be said that
presently we demand for the devices and technologies that provides much higher bandwidth , more flexible designs, thinner form factor and new and better usage models and much simpler and easier in terms of connectivity’s. Thus Thunderbolt seems to be providing a good solution to the problems existing with the copper connectors and provides a good platform for the high performance system. V. DATA TRANSFER SPEED COMPARISION
VI.
THUNDERBOLT V/S USB 3.0 THUNDERBOL T
USB 3.0
9 Copper Wires
Optical Fiber Cable
A. Wireless Network The slowest is wireless. For example, Wireless N (802.11n) can reach 160 Mb/s in the real world. Thunderbolt is about 60 times faster. Faster wireless standards will come out, but nothing even close to what a good cable can provide. B. Ethernet Moving on to other Ethernet type connections, Apple first used Gigabit Ethernet on the "Mystic “Power Mac G4 in 2000. It gives a full 1 GB/s. The fastest Ethernet on the market is 10 Gigabit Ethernet (10GBase-T), and 100 Gigabit Ethernet is under development. You won't find 10G Ethernet on many computers. The standard also makes use of fiber optic cable to achieve these transfer rates. C. C.USB 3.0 The latest USB 3.0 connectors are starting to make an appearance. We see that at best it will be only half the speed of Thunderbolt. USB 3.0 is rated at 4.8 GB/s. Of course, theoretical and actual are two different things. In the past USB was unable to deliver more than about two-thirds of theoretical speed. D. FireWire FireWire was an important competitor to USB, but it has been losing popularity. Still, the FireWire standard is still progressing. FireWire S3200 is planned to reach 3.2 GB/s. That keeps it comparable to USB 3.0, but still much slower than Thunderbolt. I doubt we'll see many devices that use it. E. Hard Drives SATA 6 GB/s Hard drives need to be speedy, and a new SATA protocol was recently released, SATA 6 Gb/s.As the name implies, it can go 6 GB/s. The nice thing with this protocol is it remains compatible with older systems and hard drives. You do need to have the right motherboard to take advantage of the latest speed increase. F. HDMI and Display Port The newest video protocols, HDMI and Display Port, are both ready to transfer HD video content and huge blocks of data if all the wires are used together. HDMI version 1.3 and higher will transfer at 10.2 GB/s, while Display Port can go up to 10.8 Gb/s. These are slightly better than Thunderbolt, but they are mostly designed for video. No one is pushing the data transfer rates of these protocols.
Speed-3 Gb/sec
Speed-10 Gb/sec
Only USB Protocol
Universal
VII.
ADVANTAGES
The Thunderbolt optical modules are physically much smaller than those of telecom grade. The optical modules are designed to be much lower cost and higher performance. Thunderbolt can send and receive data at 10 billion bits per second. The thin optical fiber will enable Thunderbolt to transfer data over very thin, flexible cables. Unlike electrical cables, Thunderbolt do not faces the problem of EMI, thus can be used up to 100m. Thunderbolt also has the ability to run multiple protocols simultaneously over a single cable, enabling the technology to connect devices such as docking stations, displays, disk drives, and more. The data transfer is bidirectional in nature thus enabling devices to transfer simultaneously. Quality of service implementation. No Operating System (OS) changes required. It also supports another feature known as Hot-swapping which means the PC needs not be shut down and restarted to attach or remove a peripheral. Enables I/O performance for the next generation. Supports multiple existing I/O protocols over a single cable and smooth transition for today’s existing electrical I/O protocols. Can connect to more devices with the same cable, or to combo devices such as docking stations.
CONCLUSION
Thunderbolt is a high-speed, multi-protocol interconnect for innovative and emerging client usage models, that complements other existing interconnects. Thunderbolt is the name for a new high-speed optical cable technology designed to connect electronic devices to each other. Thunderbolt delivers high bandwidth starting at 10 GB/s with the potential ability to scale to 100 GB/s over the next decade. Thunderbolt allows for smaller connectors and longer, thinner, and more flexible cables than currently possible. . Thunderbolt also has the ability to run multiple protocols simultaneously over a single cable, enabling the technology to connect devices such as peripherals, displays, disk drives, docking stations, and more. Intel is working with the optical component
manufacturers to make Thunderbolt components ready to ship in this year. Thunderbolt is complementary to existing I/O technologies, as it enables them to run together on a single cable at higher speeds. At the present time, Intel has conducted three successful public demonstrations of the Thunderbolt technology and confirmed that the first Thunderbolt-enabled PCs should begin shipping soon. The goal of this new developing technology is to build a high-bandwidth, faultresilient, low-cost network that can deliver performance isolation across applications. The basic approach to achieve this target is to integrate low-radix switches into server platform and interconnect severs directly using multipath topologies. Thus if the question WHY THUNDERBOLT?? arises, then the answer would be because it is cheaper as it incorporates cheaper switching components, provide better bandwidth allocation and performance isolation, uses flexible topologies, integrate multiple protocol devices on to one cable. Intel CEO Paul Otellini called Thunderbolt the I/O performance and connection for the next generation, and confirmed that both Nokia and Sony have publicly announced their support.VictorKrutul, director of Intel’s optical development team and founder of the Thunderbolt program, is even more effusive, calling Thunderbolt the biggest thing to happen to the optical industry ever, or at least since the creation of the laser.
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