The Chinese University of Hong Kong The Chinese University of Hong Kong 1 Two key questions raised by Two key questions raised by Prof Kao Prof Kao 1. 1. Is Ruby laser a suitable source for optical Is Ruby laser a suitable source for optical communication? communication? 2. 2. What material has sufficient high transparency at such What material has sufficient high transparency at such wavelengths? wavelengths? Difficult problems but fortune favors the brave!
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The Chinese University of Hong Kong 1 Two key questions raised by Prof Kao 1. Is 1. Is Ruby laser a suitable source for optical communication? 2. What.
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The Chinese University of Hong KongThe Chinese University of Hong Kong 11
Two key questions raised by Prof KaoTwo key questions raised by Prof Kao
1.1. Is Ruby laser a suitable source for optical Is Ruby laser a suitable source for optical communication?communication?
2.2. What material has sufficient high transparency What material has sufficient high transparency at such wavelengths? at such wavelengths?
Difficult problems but fortune favors the brave!
The Chinese University of Hong KongThe Chinese University of Hong Kong 22
Con-focal lens systemCon-focal lens system
Lamp Lens guide
Photomultipler
Alignment of the lenses is critical!
O.E. DeLange, “Losses suffered by coherent light redirected and refocused many times in an enclosed medium,” Bell Sys. Tech. J., Vol.44, p. 283, 1965.
D. Gloge, “Experiments with an underground lens waveguide,” Bell Sys. Tech. J., Vol.46, 721, 1967.
Thermal gradient can cause beam to shift by many cm
The Chinese University of Hong KongThe Chinese University of Hong Kong 33
Gas lens systemGas lens system
D.W. Berreman, “Convective Gas Light Guides or Lens Trains for Optical Beam Transmission ,” J. Opt. Soc. Of Am., Vol.55, pp.239-247, 1965.
Difficult to insulate!
The Chinese University of Hong KongThe Chinese University of Hong Kong 44
Hollow metallic and dielectric Hollow metallic and dielectric waveguideswaveguides
Large bending loss and expensive
E.A.J. Marcatili and R.A. Schmeltzer, “Hollow metallic and dielectric Waveguides for long distance optical transmission and lasers,” Bell Sys. Tech. J. Vol.43, p.1783, 1964.
The Chinese University of Hong KongThe Chinese University of Hong Kong 55
Thin film waveguideThin film waveguide
a. A thin film waveguide surrounded by supporting material
a. Field structure of guided wave
A.E. Karbowiak, “New type of waveguide for light and infrared waves,” Elect. Lett., Vol. 1, pp.47-8, April 1965.
Confinement not strong enough and light escapes in bends
The Chinese University of Hong KongThe Chinese University of Hong Kong 66
Detailed analysis of fiber losses Detailed analysis of fiber losses
Attenuation of PMMA
Radiation loss
Bending loss
Intrinsic loss can be as low as 1 dB/km!
The Chinese University of Hong KongThe Chinese University of Hong Kong 77
Prof Kao travelled to convince the worldProf Kao travelled to convince the world
At an early day OFC meeting
Science MuseumSouth Kensington, London
The Chinese University of Hong KongThe Chinese University of Hong Kong 88
Measurement of fiber lossMeasurement of fiber loss Loss too low to measureLoss too low to measure Built a double beam Built a double beam
spectrophotometer to spectrophotometer to improve sensitivity by improve sensitivity by 10X10X!!
The The surface effect surface effect was was characterized by a characterized by a homemade homemade ellipsometerellipsometer. .
M.W. Jones and K.C. Kao, “Spectrophotometric studies of ultra low loss optical glasses II” J. Sci. Instrum. (J. Phys. E), Vol.2, pp. 331-5, 1969.
Double Beam Spectrophotometer
The Chinese University of Hong KongThe Chinese University of Hong Kong 99
Demonstration of silica glass as Demonstration of silica glass as waveguide materialwaveguide material
An Infrasil sample from Schott Glass showed an An Infrasil sample from Schott Glass showed an attenuation attenuation as low as 5 dB/km as low as 5 dB/km at a window around 850 at a window around 850 nm! nm!
A. H. Gnauck, et al., "High-Capacity Optical Transmission Systems," J. Lightwave Technol. 26, 1032-1045 (2008)
15.5 Terabits/sec capacity• 155 wavelengths • 100 Gbps each • over 7000 km
The Chinese University of Hong KongThe Chinese University of Hong Kong 1414
Hundreds of millions of km of fiber cables Hundreds of millions of km of fiber cables deployeddeployed
The Chinese University of Hong KongThe Chinese University of Hong Kong 1515
Submarine fiber optic systemsSubmarine fiber optic systems
Over 420,000 km of fiber in over 100 undersea fiber Over 420,000 km of fiber in over 100 undersea fiber optic systems are deployed.optic systems are deployed.
Courtesy: JX Cai, Tyco Telecommunications
The Chinese University of Hong KongThe Chinese University of Hong Kong 1616
Global fiber deployment (million km)Global fiber deployment (million km)
Other S-M = utility, railway, highway, government, military, premises, etc.
Other local tel. =CO trunks, metro rings, business/office parks, CLEC, etc.
0
300
600
900
1989 1992 1995 1998 2001 2004 2007
MultimodeOther S-MCable TVOth. Local Tel.FTTB, _C, _NFTTPInt'l Subm.Long-Distance