27-06-2012, 11:47 AM
Thunderbolt Interconnects Technology and its Current Application
[attachment=25698]
INTRODUCTION
Light Peak (Thunderbolt) is Intel's code-name for a new high-speed optical cable technology designed to connect electronic devices to each other in a peripheral bus. Optical networking technologies have been over the last two decades reshaping the entire telecom infrastructure networks around the world. As network bandwidth requirements increase, optical communication and networking technologies have been moving from their telecom origin into the enterprise. For example, today in data centers, all storage area networking is based on fiber interconnects with speeds ranging from 1 Gb/s to 10 Gb/s. As the transmission bandwidth requirements increase and the costs of the emerging optical technologies become more economical, the adoption and acceptance of these optical interconnects within enterprise networks will increase. This report provides the framework for the Thunderbolt optical interconnect technology. A brief overview of the Thunderbolt interconnects technology and its current application within the enterprise is presented.
THUNDERBOLT
Thunderbolt is a new high-speed optical cable technology designed to connect electronic devices to each other in a peripheral bus. It has the capability to deliver high bandwidth, starting at 10 Gbit/s,with the potential ability to scale to 100 Gbit/s. 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 was developed as a way to reduce the proliferation of ports on modern computers. Bus systems like USB were intended to do the same, and successfully replaced a number of older technologies like RS232 and Centronics printer ports. However, increasing bandwidth demands have led to the introduction of a new series of high-performance systems like eSATA and Display Port that USB and similar systems cannot address. Thunderbolt provides enough bandwidth to allow all of these systems to be driven over a single type of interface, and in many cases on a single cable using a daisy chain. The Thunderbolt cable contains a pair of optical fibers that are used for upstream and downstream traffic. This means that Thunderbolt offers a maximum of 10 Gbit/s in both directions at the same time. The prototype system featured two motherboard 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.
THE FUNDAMENTALS OF OPTICAL COMPONENTS
A basic optical communication link consists of three key building blocks: optical fiber, light sources, and light detectors. We discuss each one in turn.
Optical Fibers
In 1966, Charles Kao and George Hockmam predicted that purified glass loss could be reduced to below 20 dB per kilometer, and they set up a world-wide race to beat this prediction. In September 1970, Robert Maurer, Donald Keck, and Peter Schultz of Corning succeeded in developing a glass fiber with attenuation less than 20 dB/km: this was the necessary threshold to make fiber optics a viable transmission technology. The silica-based optical fiber structure 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.
Light Detectors
Light detectors convert an optical signal to an electrical signal. The most common light detector is a photodiode. It operates on the principle of the p-n junction. There are two main categories of photo detectors: a p-i-n (positive, intrinsic, negative) photodiode and an Avalanche Photodiode (APD), which are typically made of InGaAs or germanium. The key parameters for photodiodes are (a) capacitance, (b) response time, © linearity, (d) noise, and (e) responsively. The theoretical responsively is 1.05 A/W at a wavelength of 1310 nm. Commercial photodiodes have responsively around 0.8 to 0.9 A/W at the same wavelength [1-4]. The dark photo-current is a small current that flows through the photo-detector even though no light is present because of the intrinsic resistance of the photo-detector and the applied reverse voltage. It is temperature sensitive and contributes to noise. Since the output electrical current of a photodiodes typically in the range of μA, a Trans impedance.
[attachment=25698]
INTRODUCTION
Light Peak (Thunderbolt) is Intel's code-name for a new high-speed optical cable technology designed to connect electronic devices to each other in a peripheral bus. Optical networking technologies have been over the last two decades reshaping the entire telecom infrastructure networks around the world. As network bandwidth requirements increase, optical communication and networking technologies have been moving from their telecom origin into the enterprise. For example, today in data centers, all storage area networking is based on fiber interconnects with speeds ranging from 1 Gb/s to 10 Gb/s. As the transmission bandwidth requirements increase and the costs of the emerging optical technologies become more economical, the adoption and acceptance of these optical interconnects within enterprise networks will increase. This report provides the framework for the Thunderbolt optical interconnect technology. A brief overview of the Thunderbolt interconnects technology and its current application within the enterprise is presented.
THUNDERBOLT
Thunderbolt is a new high-speed optical cable technology designed to connect electronic devices to each other in a peripheral bus. It has the capability to deliver high bandwidth, starting at 10 Gbit/s,with the potential ability to scale to 100 Gbit/s. 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 was developed as a way to reduce the proliferation of ports on modern computers. Bus systems like USB were intended to do the same, and successfully replaced a number of older technologies like RS232 and Centronics printer ports. However, increasing bandwidth demands have led to the introduction of a new series of high-performance systems like eSATA and Display Port that USB and similar systems cannot address. Thunderbolt provides enough bandwidth to allow all of these systems to be driven over a single type of interface, and in many cases on a single cable using a daisy chain. The Thunderbolt cable contains a pair of optical fibers that are used for upstream and downstream traffic. This means that Thunderbolt offers a maximum of 10 Gbit/s in both directions at the same time. The prototype system featured two motherboard 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.
THE FUNDAMENTALS OF OPTICAL COMPONENTS
A basic optical communication link consists of three key building blocks: optical fiber, light sources, and light detectors. We discuss each one in turn.
Optical Fibers
In 1966, Charles Kao and George Hockmam predicted that purified glass loss could be reduced to below 20 dB per kilometer, and they set up a world-wide race to beat this prediction. In September 1970, Robert Maurer, Donald Keck, and Peter Schultz of Corning succeeded in developing a glass fiber with attenuation less than 20 dB/km: this was the necessary threshold to make fiber optics a viable transmission technology. The silica-based optical fiber structure 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.
Light Detectors
Light detectors convert an optical signal to an electrical signal. The most common light detector is a photodiode. It operates on the principle of the p-n junction. There are two main categories of photo detectors: a p-i-n (positive, intrinsic, negative) photodiode and an Avalanche Photodiode (APD), which are typically made of InGaAs or germanium. The key parameters for photodiodes are (a) capacitance, (b) response time, © linearity, (d) noise, and (e) responsively. The theoretical responsively is 1.05 A/W at a wavelength of 1310 nm. Commercial photodiodes have responsively around 0.8 to 0.9 A/W at the same wavelength [1-4]. The dark photo-current is a small current that flows through the photo-detector even though no light is present because of the intrinsic resistance of the photo-detector and the applied reverse voltage. It is temperature sensitive and contributes to noise. Since the output electrical current of a photodiodes typically in the range of μA, a Trans impedance.