EKT 442: Optoelectronics EKT 442: Optoelectronics

School of Computer and Communication School of Computer and Communication Engineering, Engineering,

University Malaysia Perlis (UniMAP)University Malaysia Perlis (UniMAP)

Optoelectronics Communications

CHAPTER CHAPTER 11

Coursework Contribution1. COURSE IMPLEMENTATIONSI)Lecture

3 hours per week for 14 weeks (Total = 42 hours)II)Laboratory

2 hours per week for 14 weeks (Total = 28 hours)

Laboratory assignment 30%

Test 1&2 20 %

Final Exam 50%

Total 100%

Lecturer: Mr. Hilal A. FadhilOffice: 1st Floor, House #8A, KKF 34, K.wei- Kuala PerlisE-mail: hilaladnan@unimap.edu.myOffice tel#: 04-9852639 HP#: Upon Request

Teaching Engineer: Mr. Matnor+ Ms. Fazilna, matnor@unimap.edu.myOffice: House #A4, KKF 33, Kuala Perlis

• Course materialCourse text book:

• “Gerd Keiser, Optical Fiber Communications, 3rd Edition, Mc Graw Hill, 2000

Reference Books:– Joseph C. Palais, Fiber Optic Communications, 5th

Edition, Prentice Hall, 2005 – Jeff Hecht, Undestanding Fiber Optics, 5th Edition,

Prentice Hall, 2006

Course Outcome

Chapter 1-Introduction:

Chapter 2: Light Propagation & Transmission Characteristics of Optical Fiber

Chapter 3: Optical Components/ Passive Devices

Chapter 4: Optical Sources

Chapter 5: Light Detectors, Noise and Detection

Chapter 6: SYSTEM DESIGN

What are the features of a optical communication system?What are the features of a optical communication system?Why “optical ” instead of “copper wire ”?Why “optical ” instead of “copper wire ”?

Introduction

For years fiber optics has been merely a system for piping light around corners and into in accessible places so as to allow the hidden to be seen. But now, fiber optics has evolved into a system of significantly greater importance and use. Throughout the world it is now being used to transmit voice, video, and data signals by light waves over flexible hair-thin threads of glass or plastics. Its advantages in such use, as compared to conventional coaxial cable or twisted wire pairs, are fantastic. As a result, light-wave communication systems of fiber optics communication system are one of the important feature for today’s communication.

A History of Fiber Optic Technology

The Nineteenth Century

• John Tyndall, 1870

– water and light experiment

– demonstrated light used internal reflection to follow a specific path

• William Wheeling, 1880

– “piping light” patent

– never took off

• Alexander Graham Bell, 1880

– optical voice transmission system

– called a photophone

– free light space carried voice 200 meters

• Fiber-scope, 1950’s

The Twentieth Century

• Glass coated fibers developed to reduce optical loss

• Inner fiber - core

• Glass coating - cladding

• Development of laser technology was important to fiber optics

• Large amounts of light in a tiny spot needed

• 1960, ruby and helium-neon laser developed

• 1962, semiconductor laser introduced - most popular type of laser in fiber optics

cladding

core

The Twentieth Century (continued)

• 1966, Charles Kao and Charles Hockman proposed optical fiber could be used to transmit laser light if attenuation could be kept under 20dB/km (optical fiber loss at the time was over 1,000dB/km)

• 1970, Researchers at Corning developed a glass fiber with less than a 20dB/km loss

• Attenuation depends on the wavelength of light

Short

band

Optical Wavelength Bands

C-band: Conventional Band

L-band: Long Band

Fiber Optics Applications• Military

– 1970’s, Fiber optic telephone link installed aboard the U.S.S. Little Rock– 1976, Air Force developed Airborne Light Fiber Technology (ALOF)

• Commercial– 1977, AT&T and GTE installed the first fiber optic telephone system– Fiber optic telephone networks are common today– Research continues to increase the capabilities of fiber optic transmission

Applications of Fiber Optics

• Military• Computer• Medical/Optometric• Sensor• Communication

Military Application

Computer Application

Sensors

Gas sensors

Chemical sensors

Mechanical sensors

Fuel sensors

Distance sensors

Pressure sensors

Fluid level sensors

Gyro sensors

Medical Application

• Endoscope

• Eyes surgery

• Blood pressure meter

The Future• Fiber Optics have immense potential bandwidth

(over 1 teraHertz, 1012 Hz)• Fiber optics is predicted to bring broadband services

to the home– interactive video– interactive banking and shopping– distance learning– security and surveillance– high-speed data communication– digitized video

Fiber Optic Fundamentals

Advantages of Fiber Optics

• Immunity from Electromagnetic (EM) Radiation and Lightning

• Lighter Weight• Higher Bandwidth

• Better Signal Quality• Lower Cost• Easily Upgraded• Ease of Installation

The main advantages:Large BW and Low loss

Immunity from EM radiation and Lightning:

- Fiber is made from dielectric (non-conducting) materials, It is un affected by EM radiation.

- Immunity from EM radiation and lightning most important to the military and in aircraft design.

- The fiber can often be run in same conduits that currently carry power, simplifying installation.

Lighter Weight:

- Copper cables can often be replaced by fiber optic cables that weight at least ten times less.

- For long distances, fiber optic has a significant weight advantage over copper cable.

Higher Bandwidth - Fiber has higher bandwidth than any alternative

available.- CATV industry in the past required amplifiers every

thousand feet, when copper cable was used (due to limited bandwidth of the copper cable).

- A modern fiber optic system can carry the signals up 100km without repeater or without amplification.

Better Signal Quality

- Because fiber is immune to EM interference, has lower loss per unit distance, and wider bandwidth, signal quality is usually substantially better compared to copper.

Lower Cost

- Fiber certainly costs less for long distance applications.- The cost of fiber itself is cheaper per unit distance than copper if

bandwidth and transmission distance requirements are high.

Principles of Fiber Optic Transmission

• Electronic signals converted to light• Light refers to more than the visible portion of the electromagnetic

(EM) spectrum

Optical power Measurement units:

In designing an optical fiber link, it is of interest to establish, measure the signal level at the transmitter, at the receiver,, at the cable connection, and in the cable.

Power: Watt (W), Decibel (dB), and dB Milliwatt (dBm).

dB: The difference (or ratio) between two signal levels. Used to describe the effect of system devices on signal strength. For example, a cable has 6 dB signal loss or an amplifier has 15 dB of gain.

dBPower

Powerlog10Gain

In

Out

dBm: A signal strength or power level. 0 dBm is defined as 1 mW (milliWatt) of power into a terminating load such as an antenna or power meter.

The Electromagnetic Spectrum

- Light is organized into what is known as the electromagnetic spectrum.

- The electromagnetic spectrum is composed of visible and near-infrared light like that transmitted by fiber and all other wavelengths used to transmit signals such as AM and FM and television.

• Wavelength - the distance a single cycle of an EM wave covers

• For fiber optics applications, two categories of wavelength are used– visible (400 to 700 nanometers) - limited use– near-infrared (700 to 2000 nanometers) - used almost always

in modern fiber optic systems

Principles of Fiber Optic Transmission

• Fiber optic links contain three basic elements– transmitter– optical fiber– receiver

Transmitter ReceiverUser

Output(s)

Optical Fiber

Electrical-to-OpticalConversion

Optical-to-ElectricalConversion

UserInput(s)

Elements of an Optical Fiber communication

• Transmitter (TX)

– Electrical interface encodes user’s information through AM, FM or Digital Modulation

– Encoded information transformed into light by means of a light-emitting diode (LED) or laser diode (LD)

ElectricalInterface

Data Encoder/Modulator

LightEmitter

OpticalOutput

UserInput(s)

• Receiver (RX)

– decodes the light signal back into an electrical signal– types of light detectors typically used

• PIN photodiode• Avalanche photodiode• made from silicon (Si), indium gallium arsenide (InGaAs) or germanium (Ge)

– the data decoder/demodulator converts the signals into the correct format

Light Detector/Amplifier

Data Decoder/Demodulator

ElectricalInterface

OpticalInput

UserOutput(s)

• Transmission comparison– metallic: limited information and distance– free-space:

• large bandwidth• long distance• not private• costly to obtain

useable spectrum– optical fiber: offers

best of both

Fiber Optic Components

• Fiber Optics Cable

• Extremely thin strands of ultra-pure glass• Three main regions

– center: core (9 to 100 microns)– middle: cladding (125 or 140 microns)– outside: coating or buffer (250, 500 and 900 microns)

A FIBER STRUCTURE

Light Emitters• Two types

– Light-emitting diodes (LED’s)

• Surface-emitting (SLED): difficult to focus, low cost

• Edge-emitting (ELED): easier to focus, faster

– Laser Diodes (LD’s)

• narrow beam

• fastest

Detectors

• Two types

– Avalanche photodiode

• internal gain

• more expensive

• extensive support electronics required

– PIN photodiode

• very economical

• does not require additional support circuitry

• used more often

Interconnection Devices

• Connectors, splices, couplers, splitters, switches, wavelength division multiplexers (WDM’s)

• Examples– Interfaces between local area networks and devices– Patch panels– Network-to-terminal connections

Manufacture of Optical Fiber

• 1970, Corning developed new process called inside vapor deposition (IVD) to first achieve attenuation less than 20dB/km

• Later, Corning developed outside vapor deposition (OVD) which increased the purity of fiber

• Optical fiber was developed that exhibits losses as low as 0.2dB/km (at 1550nm). This seemed to be adequate for any application.

• As the Internet expanded, more capacity was needed. Electronics can handle about 40Gbps, but not much more. Researchers developed Dense Wavelength-Division Multiplexing (DWDM) - 80 or more simultaneous data streams can now be combined on a single fiber, each being transmitted at a slightly different color of light

Introductions

Manufacture of Optical Fiber - MCVD• Modified Chemical Vapor Deposition (MCVD)

– another term for IVD method– vaporized raw materials are deposited into a pre-made silica tube

Cont…• Widely adopted to produce very low – loss graded – index fibers.• The glass vapor particles, arising from the reaction of the constituent metal halide

gases and oxygen, flow through the inside of a revolving silica tube.• As the SiO2 particles are deposited, they are sintered to a clear glass layer by an

oxyhydrogen torch which travels back and forth along the tube.

• When the desired thickness of glass has been deposited, the vapor flow is shut off and the tube is heated strongly to cause it to collapse into a solid rod preform.

• The fiber that is subsequently drawn from this preform rod will have a core that consists of the vapor deposited material and a cladding that consists of the original silica tube.

Manufacture of Optical Fiber - OVD

• Outside Vapor Deposition (OVD)– vaporized raw materials are deposited on a rotating rod– the rod is removed and the resulting perform is consolidated by heating