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!

850 nm - GaAs laser emission region850 nm - GaAs laser emission region. .

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.

The Chinese University of Hong KongThe Chinese University of Hong Kong 1010

The race to develop the first low-loss The race to develop the first low-loss optical fiberoptical fiber

Outside Vapor Deposition Method used by Corning in 1970

© 1999 S.O. Kasap, Optoelectronics (Prentice Hall)

Vapors: SiCl4+ GeCl4+O2

Rotate mandrel

(a)

Deposited sootBurner

Fuel: H2

Target rod

Deposited Ge doped SiO2

(b)

Furnace

Porous sootpreform with hole

Clear solidglass preform

Drying gases

(c)

Furnace

Drawn fiber

Preform

The Chinese University of Hong KongThe Chinese University of Hong Kong 1111

Fiber drawingFiber drawing Many optical fiber production Many optical fiber production

methods inventedmethods invented• OVDOVD• VADVAD• MCVDMCVD• PCVDPCVD

1111

© 1999 S.O. Kasap, Optoelectronics (Prentice Hall)

Preform feed

Furnace 2000°C

Thicknessmonitoring gauge

Take-up drum

Polymer coater

Ultraviolet light or furnace for curing

Capstan

Schematic illustration of a fiber drawing tower.

Preform feed

Furnace 2000°C

Thicknessmonitoring gauge

Take-up drum

Polymer coater

Ultraviolet light or furnace for curing

Capstan

Schematic illustration of a fiber drawing tower.

The Chinese University of Hong KongThe Chinese University of Hong Kong 1212

Light guiding inside fiberLight guiding inside fiber

Snell’s Law :

Note: if we increase 1 to c such that 2=90o

If 1 > c Total Internal Reflection

n2

n1

22 1

1

sin , c

nn n

n

Core

Cladding

Cladding

Jacket

Jacket

1 1 2 2sin sinn n

The Chinese University of Hong KongThe Chinese University of Hong Kong 1313

High-capacity experimental demonstration High-capacity experimental demonstration

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

Source: KMI Research, CRU Group