Fiber Optic Telecommunication

Fiber Optic
Telecommunication
Nick Massa
Springfield Technical Community College
Springfield, Massachusetts
Fiber optics is a major building block in the telecommunication infrastructure. Its high
bandwidth capabilities and low attenuation characteristics make it ideal for gigabit transmission
and beyond. In this module, you will be introduced to the building blocks that make up a fiber
optic communication system. You will learn about the different types of fiber and their
applications, light sources and detectors, couplers, splitters, wavelength-division multiplexers,
and state-of-the-art devices used in the latest high-bandwidth communication systems. Attention
will also be given to system performance criteria such as power and rise-time budgets.
Prerequisites
Before you work through this module, you should have completed Module 1-7, Basic Principles
of Fiber Optics. In addition, you should be able to manipulate and use algebraic formulas, deal
with units, and use basic trigonometric functions such as sine, cosine, and tangent. A basic
understanding of wavelength, frequency, and the velocity of light is also assumed.
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F U N D AM E N T AL S O F P H O T O N I C S
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Objectives
When you finish this module, you will be able to:
• Identify the basic components of a fiber optic communication system
• Discuss light propagation in an optical fiber
• Identify the various types of optical fibers
• Determine the dispersion characteristics for the various types of optical fibersDescribe
the various connector types
• Calculate decibel and dBm power
• Calculate the power budget for a fiber optic system
• Calculate the bandwidth of a fiber optic system
• Describe the operation and applications of the various types of fiber optic couplers
• Describe the operation and applications of light-emitting diodes (LEDs)
• Describe the operation and applications of laser diodes (LDs)
• Describe the operation and applications of distributed-feedback (DFB) lasers
• Discuss the differences between LEDs and laser diodes with respect to performance
characteristics
• Discuss the differences between the various types of optical detectors with respect to
performance characteristics
• Describe how pulse code modulation (PCM) is used in analog-to-digital conversion
• Describe the operation North American Digital Hierarchy
• Describe the difference between internal and external modulation
• Discuss the principles of time-division multiplexing (TDM)
• Discuss the principles of wavelength-division multiplexing (WDM)
• Discuss the principles of dense wavelength-division multiplexing (DWDM)
• Discuss the significance of the International Telecom Union grid (ITU grid)
• Discuss the use of erbium-doped fiber amplifiers (EDFA) for signal regeneration
• Describe the operation and applications of fiber Bragg gratings
• Describe the operation and application of fiber optic circulators
• Describe the operation of a typical fiber optic communication system and the
components that make it up
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Scenario—Using Fiber Optics in Telecommunication
Michael recently completed an associate degree in laser electro-optics technology
at Springfield Technical Community College in Springfield, Massachusetts. Upon
graduation he accepted a position as an electro-optics technician at JDS Uniphase
Corporation in Bloomfield, Connecticut. The company makes high-speed fiber optic
modulators and components that are used in transmitters for the
telecommunication and cable television industry.
The company’s main focus is on the precision manufacturing of these devices,
which requires not only an in-depth knowledge of how the devices work but also an
appreciation for the complex manufacturing processes that are required to fabricate
the devices to exacting specifications. While Mike was in school, he took courses in
optics, fiber optics, and electronics. The background he received, especially in the
area of fiber optic testing and measuring, has proven to be invaluable in his day-today
activities. On the job, Mike routinely works with fusion splicers, optical power
meters, and laser sources and detectors, as well as with optical spectrum
analyzers and other sophisticated electronic test equipment.
Mike was fortunate in that during his senior year in college he was awarded a full
scholarship and internship at JDS Uniphase. The company allowed Mike to
complete his degree while working part time. According to Mike, “the experience of
working in a high-tech environment while going to school really helps you see the
practical applications of what you are learning—which is especially important in a
field that is so rapidly changing as fiber optics.”
Opening Activities
The field of fiber optics, especially with respect to telecommunication, is a rapidly changing
world in which, seemingly, each day a new product or technology is introduced. A good way to
start learning about this field is to research the companies