Photonic NoC Routing Survey
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[[PHENIC]]
CENTER:SIZE(60){COLOR(gold){Understanding Light, Wavelengths and Spectrum}}
CENTER:Last update Dec. 2015., By B.
#CONTENTS
***What is Color? [#n7388e3f]
Color is all around us. It is a sensation that adds excitement and emotion to our lives. Everything from the cloths we wear, to the pictures we paint revolves around color. Without color; the world (especially RGB World) would be a much less beautiful place. Color can also be used to describe emotions; we can be red hot, feeling blue, or be green with envy.
In order to understand color we need a brief overview of light. Without light, there would be no color, and hence no RGB World. Thank God for light!
Light is made up of energy waves which are grouped together in what is called a spectrum. Light that appears white to us, such as light from the sun, is actually composed of many colors. The wavelengths of light are not colored, but produce the sensation of color.
Visible light - The wavelengths our eyes can detect is only a small portion of the electromagnetic energy spectrum. We call this the visible light spectrum. At one end of the visible spectrum are the short wavelengths of light we perceive as blue. At the other end of the visible spectrum are the longer wavelengths of light we perceive as red. All the other colors we can see in nature are found somewhere along the spectrum between blue and red. Beyond the limits at each end of the visible spectrum are the short wavelengths of ultraviolet light and Xrays and the long wavelengths of infrared radiation and radio waves, which are not visible to the human eye.
CENTER:&ref(color.png,,80%);
***What is visible light ? [#jf2ea407]
Visible light is a form of electromagnetic radiation (EMR). EMR exists throughout the universe, and is basically small packets of energy that travel from one point in space to another at 186,282 miles per second (the speed of light). As these particles travel, they follow a wave pattern, and oscillate up and down between high and low points along the way.
CENTER:&ref(wavelength-nm.jpg,,80%);
The light we are most familiar with is surely the light we can see. Our eyes are sensitive to light whose wavelength is in the range of about 400 nm to 700 nm, from the violet to the red. But for fiber optics with glass fibers, we use light in the infrared region which has wavelengths longer than visible light. Because the attenuation of the fiber is less at longer wavelengths.
***What is wavelength? [#bcf38689]
The distance between each peak is called the wavelength. Wavelengths are measured in meters, micrometers and nanometers; the shorter that distance, the higher the particle’s energy and frequency.
CENTER:&ref(chart-wavelength.png,,130%);
Radio waves have very long wavelengths, ranging between one and ten meters between each wave peak. In X-rays or gamma rays, particles pack a lot more energy and travel at very short wavelengths, smaller than a nanometer. When these particles are traveling at wavelengths between about 400 and 700 nanometers, we can see them, and that is what makes up visible light.
***Some Light Wavelengths are Easily Absorbed, and Highly Effective [#y3201330]
EMR can be absorbed by matter (and this is the basis of photochemistry). But not all wavelengths are as easily absorbed as others. For example, dangerous gamma rays, x-rays, the higher bands of ultraviolet light, and microwaves are not easily absorbed by the atmosphere, while radio waves, infrared and visible light are not absorbed and penetrate the earth's atmosphere.
Likewise, not all wavelengths of light are readily absorbed by the skin or animal cells and certain wavelengths are much more effective in photochemical reactions than others. In particular, NASA's work with LED lights discovered that light in the far red, nearly infrared range at a wavelength of 670 nanometers, is one of two optimal wavelengths for both penetration of the skin and absorption by the mitochondria. Light at the 670nm wavelength can penetrate the skin up to 4 centimeters and travel within tissue up to 20 centimeters, whereas white light energy cannot go nearly as deep [[SRC>http://www.qbmi.com/light-therapy/understanding-light/wavelengths-and-spectrum]].
Wavelength and frequency are related. Generally, the radiation of shorter wavelengths are identified by their wavelengths, while the longer wavelengths are identified by their frequency.
***Common Wavelengths in Fiber Optics [#q3e83a51]
Wavelengths typically range from 800 nm to 1600 nm, but by far the most common wavelengths actually used in fiber optics are 850 nm, 1300 nm, and 1550 nm. Multimode fiber is designed to operate at 850 nm and 1300 nm, while single-mode fiber is optimized for 1310 nm and 1550 nm. The difference between 1300 nm and 1310 nm is simply a matter of convention. Both lasers and LEDs are used to transmit light through optical fiber. Lasers are usually used for 1310nm or 1550nm single-mode applications. LEDs are used for 850nm or 1300nm multimode applications.
CENTER:&ref(www.png,,130%);
***Why Those Common Wavelengths? [#y76e269f]
As mentioned above, the most common wavelengths used in fiber optics are 850 nm, 1300 nm and 1550 nm. But why do we use these three wavelengths? Because the attenuation of the fiber is much less at those wavelengths. Therefore, they best match the transmission properties of available light sources with the transmission qualities of optical fiber. The attenuation of glass optical fiber is caused by two factors: absorption and scattering. Absorption occurs in several specific wavelengths called water bands due to the absorption by minute amounts of water vapor in the glass. Scattering is caused by light bouncing off atoms or molecules in the glass.
It is strongly a function of wavelength, with longer wavelengths having much lower scattering. From the chart below, we can obviously see that there are three low-lying areas of absorption, and an ever-decreasing amount of scattering as wavelengths increase. As you can see, all three popular wavelengths have almost zero absorption.
CENTER:&ref(w.png,,130%);
-[[Introduction to the Electromagnetic Spectrum (720p)>https://www.youtube.com/watch?v=hXe7EVv1y0Q]]
***Electromagnetic Spectrum [#w960faa9]
CENTER:&ref(VisibleLightSpectrum.jpg,,50%);
***The Sun’s Electromagnetic Spectrum [#v2a7057d]
The energy that reaches the Earth is known as solar radiation. Although the sun emits radiation at all wavelengths, approximately 44% falls within visible-light wavelengths. The region of the spectrum referred to as visible light (light our eyes can detect) is composed of
relatively short wavelengths in the range 400 nanometers (nm), or 0.4 micrometers (μm), through 700 nm, or 0.7 μm.
CENTER:&ref(RadiationIntensityVSWavelength.jpg,,50%);
***Refrcative Index [#s8c22b27]
In optics the refractive index or index of refraction n of an material is a dimensionless number that describes how light, propagates through that medium. It is defined as
n = c/v, (V: speed of light, and v speed of the medium).
For example, the refractive index of water is 1.33, meaning that light travels 1.33 times faster in a vacuum than it does in water.
The refractive index of silicon is 3.48 - 3.42, meaning that light travels 3.48 - 3.42 times faster in a vacuum than it does in silicon.
-[[List of Refractive INdices>https://en.wikipedia.org/wiki/List_of_refractive_indices]]
***What are Redshift and Blueshift? [#x723e65d]
Redshift and blueshift describe how light changes as objects in space (such as stars or galaxies) move closer or farther away from us. The concept is key to charting the universe's expansion.
Visible light is a spectrum of colors, which is clear to anyone who has looked at a rainbow. When an object moves away from us, the light is shifted to the red end of the spectrum, as its wavelengths get longer. If an object moves closer, the light moves to the blue end of the spectrum, as its wavelengths get shorter.
CENTER:&ref(redshift.png,,50%);
A blueshift is any decrease in wavelength, with a corresponding increase in frequency, of an electromagnetic wave; the opposite effect is referred to as redshift. In visible light, this shifts the color from the red end of the spectrum to the blue end.
***Photonics Devices Delay Parameters [#gabf8d70]
For 22nm technology [Ref.1] :
-Waveguide propagation delay: 1.14 micro-s/micro-m
-Modulator delay: 23.8 ps
-Photo Detectordelay: 4.2 ps
Ref.1: Somayyeh Koohi, Shaahin Hessabi,[[¨Scalable architecture for a contention-free optical network on-chip>https://www.researchgate.net/publication/257251990_Scalable_architecture_for_a_contention-free_optical_network_on-chip]], J. Parallel and Distributed Computing, vol 72, no. 11, 2012.
***Photonic Devices Insertion Loss parameters [#x0517e91]
-waveguide propagation loss: 1dB/cm
-passing through ring loss: 0.5dB
-passing by ring loss: 0.01dB
-waveguide bending loss: 0.005 dB
-waveguide crossing loss: 0.12 dB
-splitter loss: 0.1dB
-receiver loss: -17dBm
Ref. Mark J. Cianchetti, Joseph C. Kerekes, and David H. Albonesi, [[Phastlane: A Rapid Transit Optical Routing Network>http://www.csl.cornell.edu/~albonesi/research/papers/isca09.pdf]], ISCA 2009.
***Laser power [#z7dd1f1d]
Off-chip laser power (LP) is constant and independent of network traffic.
LP is computed from the maximum optical insertion loss in the NoC.
Optical insertion loss = passing through the MR loss + passing by MR loss + waveguide crossing and bedding loss + waveguide propagation loss
*References [#i85e6220]
-WWW
終了行:
[[PHENIC]]
CENTER:SIZE(60){COLOR(gold){Understanding Light, Wavelengths and Spectrum}}
CENTER:Last update Dec. 2015., By B.
#CONTENTS
***What is Color? [#n7388e3f]
Color is all around us. It is a sensation that adds excitement and emotion to our lives. Everything from the cloths we wear, to the pictures we paint revolves around color. Without color; the world (especially RGB World) would be a much less beautiful place. Color can also be used to describe emotions; we can be red hot, feeling blue, or be green with envy.
In order to understand color we need a brief overview of light. Without light, there would be no color, and hence no RGB World. Thank God for light!
Light is made up of energy waves which are grouped together in what is called a spectrum. Light that appears white to us, such as light from the sun, is actually composed of many colors. The wavelengths of light are not colored, but produce the sensation of color.
Visible light - The wavelengths our eyes can detect is only a small portion of the electromagnetic energy spectrum. We call this the visible light spectrum. At one end of the visible spectrum are the short wavelengths of light we perceive as blue. At the other end of the visible spectrum are the longer wavelengths of light we perceive as red. All the other colors we can see in nature are found somewhere along the spectrum between blue and red. Beyond the limits at each end of the visible spectrum are the short wavelengths of ultraviolet light and Xrays and the long wavelengths of infrared radiation and radio waves, which are not visible to the human eye.
CENTER:&ref(color.png,,80%);
***What is visible light ? [#jf2ea407]
Visible light is a form of electromagnetic radiation (EMR). EMR exists throughout the universe, and is basically small packets of energy that travel from one point in space to another at 186,282 miles per second (the speed of light). As these particles travel, they follow a wave pattern, and oscillate up and down between high and low points along the way.
CENTER:&ref(wavelength-nm.jpg,,80%);
The light we are most familiar with is surely the light we can see. Our eyes are sensitive to light whose wavelength is in the range of about 400 nm to 700 nm, from the violet to the red. But for fiber optics with glass fibers, we use light in the infrared region which has wavelengths longer than visible light. Because the attenuation of the fiber is less at longer wavelengths.
***What is wavelength? [#bcf38689]
The distance between each peak is called the wavelength. Wavelengths are measured in meters, micrometers and nanometers; the shorter that distance, the higher the particle’s energy and frequency.
CENTER:&ref(chart-wavelength.png,,130%);
Radio waves have very long wavelengths, ranging between one and ten meters between each wave peak. In X-rays or gamma rays, particles pack a lot more energy and travel at very short wavelengths, smaller than a nanometer. When these particles are traveling at wavelengths between about 400 and 700 nanometers, we can see them, and that is what makes up visible light.
***Some Light Wavelengths are Easily Absorbed, and Highly Effective [#y3201330]
EMR can be absorbed by matter (and this is the basis of photochemistry). But not all wavelengths are as easily absorbed as others. For example, dangerous gamma rays, x-rays, the higher bands of ultraviolet light, and microwaves are not easily absorbed by the atmosphere, while radio waves, infrared and visible light are not absorbed and penetrate the earth's atmosphere.
Likewise, not all wavelengths of light are readily absorbed by the skin or animal cells and certain wavelengths are much more effective in photochemical reactions than others. In particular, NASA's work with LED lights discovered that light in the far red, nearly infrared range at a wavelength of 670 nanometers, is one of two optimal wavelengths for both penetration of the skin and absorption by the mitochondria. Light at the 670nm wavelength can penetrate the skin up to 4 centimeters and travel within tissue up to 20 centimeters, whereas white light energy cannot go nearly as deep [[SRC>http://www.qbmi.com/light-therapy/understanding-light/wavelengths-and-spectrum]].
Wavelength and frequency are related. Generally, the radiation of shorter wavelengths are identified by their wavelengths, while the longer wavelengths are identified by their frequency.
***Common Wavelengths in Fiber Optics [#q3e83a51]
Wavelengths typically range from 800 nm to 1600 nm, but by far the most common wavelengths actually used in fiber optics are 850 nm, 1300 nm, and 1550 nm. Multimode fiber is designed to operate at 850 nm and 1300 nm, while single-mode fiber is optimized for 1310 nm and 1550 nm. The difference between 1300 nm and 1310 nm is simply a matter of convention. Both lasers and LEDs are used to transmit light through optical fiber. Lasers are usually used for 1310nm or 1550nm single-mode applications. LEDs are used for 850nm or 1300nm multimode applications.
CENTER:&ref(www.png,,130%);
***Why Those Common Wavelengths? [#y76e269f]
As mentioned above, the most common wavelengths used in fiber optics are 850 nm, 1300 nm and 1550 nm. But why do we use these three wavelengths? Because the attenuation of the fiber is much less at those wavelengths. Therefore, they best match the transmission properties of available light sources with the transmission qualities of optical fiber. The attenuation of glass optical fiber is caused by two factors: absorption and scattering. Absorption occurs in several specific wavelengths called water bands due to the absorption by minute amounts of water vapor in the glass. Scattering is caused by light bouncing off atoms or molecules in the glass.
It is strongly a function of wavelength, with longer wavelengths having much lower scattering. From the chart below, we can obviously see that there are three low-lying areas of absorption, and an ever-decreasing amount of scattering as wavelengths increase. As you can see, all three popular wavelengths have almost zero absorption.
CENTER:&ref(w.png,,130%);
-[[Introduction to the Electromagnetic Spectrum (720p)>https://www.youtube.com/watch?v=hXe7EVv1y0Q]]
***Electromagnetic Spectrum [#w960faa9]
CENTER:&ref(VisibleLightSpectrum.jpg,,50%);
***The Sun’s Electromagnetic Spectrum [#v2a7057d]
The energy that reaches the Earth is known as solar radiation. Although the sun emits radiation at all wavelengths, approximately 44% falls within visible-light wavelengths. The region of the spectrum referred to as visible light (light our eyes can detect) is composed of
relatively short wavelengths in the range 400 nanometers (nm), or 0.4 micrometers (μm), through 700 nm, or 0.7 μm.
CENTER:&ref(RadiationIntensityVSWavelength.jpg,,50%);
***Refrcative Index [#s8c22b27]
In optics the refractive index or index of refraction n of an material is a dimensionless number that describes how light, propagates through that medium. It is defined as
n = c/v, (V: speed of light, and v speed of the medium).
For example, the refractive index of water is 1.33, meaning that light travels 1.33 times faster in a vacuum than it does in water.
The refractive index of silicon is 3.48 - 3.42, meaning that light travels 3.48 - 3.42 times faster in a vacuum than it does in silicon.
-[[List of Refractive INdices>https://en.wikipedia.org/wiki/List_of_refractive_indices]]
***What are Redshift and Blueshift? [#x723e65d]
Redshift and blueshift describe how light changes as objects in space (such as stars or galaxies) move closer or farther away from us. The concept is key to charting the universe's expansion.
Visible light is a spectrum of colors, which is clear to anyone who has looked at a rainbow. When an object moves away from us, the light is shifted to the red end of the spectrum, as its wavelengths get longer. If an object moves closer, the light moves to the blue end of the spectrum, as its wavelengths get shorter.
CENTER:&ref(redshift.png,,50%);
A blueshift is any decrease in wavelength, with a corresponding increase in frequency, of an electromagnetic wave; the opposite effect is referred to as redshift. In visible light, this shifts the color from the red end of the spectrum to the blue end.
***Photonics Devices Delay Parameters [#gabf8d70]
For 22nm technology [Ref.1] :
-Waveguide propagation delay: 1.14 micro-s/micro-m
-Modulator delay: 23.8 ps
-Photo Detectordelay: 4.2 ps
Ref.1: Somayyeh Koohi, Shaahin Hessabi,[[¨Scalable architecture for a contention-free optical network on-chip>https://www.researchgate.net/publication/257251990_Scalable_architecture_for_a_contention-free_optical_network_on-chip]], J. Parallel and Distributed Computing, vol 72, no. 11, 2012.
***Photonic Devices Insertion Loss parameters [#x0517e91]
-waveguide propagation loss: 1dB/cm
-passing through ring loss: 0.5dB
-passing by ring loss: 0.01dB
-waveguide bending loss: 0.005 dB
-waveguide crossing loss: 0.12 dB
-splitter loss: 0.1dB
-receiver loss: -17dBm
Ref. Mark J. Cianchetti, Joseph C. Kerekes, and David H. Albonesi, [[Phastlane: A Rapid Transit Optical Routing Network>http://www.csl.cornell.edu/~albonesi/research/papers/isca09.pdf]], ISCA 2009.
***Laser power [#z7dd1f1d]
Off-chip laser power (LP) is constant and independent of network traffic.
LP is computed from the maximum optical insertion loss in the NoC.
Optical insertion loss = passing through the MR loss + passing by MR loss + waveguide crossing and bedding loss + waveguide propagation loss
*References [#i85e6220]
-WWW
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