Guided Wave Optical Components and Devices

Basics, Technology, and Applications

Bishnu P. Pal

• Publisher: Academic Press
• Year: 2010
• Print ISBN:
  9780120884810
• eBook ISBN:
  9780080532714
• Topic: Technology & Engineering
• Subtopic: Civil Engineering
• Index: Technology & Engineering

Guided Wave Optical Components and Devices provides a comprehensive, lucid, and clear introduction to the world of guided wave optical components and devices. Bishnu Pal has collaborated with some of the greatest minds in optics to create a truly inclusive treatise on this contemporary topic. Written by leaders in the field, this book delivers cutting-edge research and essential information for professionals, researchers, and students on emerging topics like microstructured fibers, broadband fibers, polymer fiber components and waveguides, acousto-optic interactions in fibers, higher order mode fibers, nonlinear and parametric process in fibers, revolutionary effects of erbium doped and Raman fiber amplifiers in DWDM and CATV networks, all-fiber network branching component technology platforms like fused fiber couplers, fiber gratings, and side-polished fiber half-couplers, arrayed waveguides, optical MEMS, fiber sensing technologies including safety, civil structural health monitoring, and gyroscope applications. - Accessible introduction to wide range of topics relating to established and emerging optical components - Single-source reference for graduate students in optical engineering and newcomer practitioners, focused on components - Extensive bibliographical information included so readers can get a broad introduction to a variety of optical components and their applications in an optical network

CHAPTER 1

Optical Fibers for Broadband Lightwave Communication: Evolutionary Trends in Designs

Bishnu P. Pal^*, Physics Department, Indian Institute of Technology Delhi, New Delhi, India

1 INTRODUCTION

Development of optical fiber technology is considered to be a major driver behind the information technology revolution and the tremendous progress on global telecommunications that has been witnessed in recent years. Fiber optics, from the point of view of telecommunication, is now almost taken for granted in view of its wide-ranging application as the most suitable singular transmission medium for voice, video, and data signals. Indeed, optical fibers have now penetrated virtually all segments of telecommunication networks, whether transoceanic, transcontinental, intercity, metro, access, campus, or on-premise. The first fiber optic telecom link went public in 1977. Since that time, growth in the lightwave communication industry until about 2000 has been indeed mind boggling. According to a Lucent technology report [1], in the late 1990s optical fibers were deployed at approximately 4800 km/hr, implying a total fiber length of almost three times around the globe each day until it slowed down when the information technology bubble burst!

The Internet revolution and deregulation of the telecommunication sector from government controls, which took place almost globally in the recent past, have substantially contributed to this unprecedented growth within such a short time, which was rarely seen in any other technology. Initial research and development (R&D) in this field had centered on achieving optical transparency in terms of exploitation of the low-loss and low-dispersion transmission wavelength windows of high-silica optical fibers. Though the low-loss fiber with a loss under 20 dB/km that was reported for the first time was a single-mode fiber (SMF) at the He–Ne laserm wavelength [2], the earliest fiber optic lightwave systems exploited the first low-loss wavelength window centered on 820 nm with graded index multi-mode fibers forming the transmission media. However, primarily due to the unpredictable nature of the bandwidth of jointed multimode fiber links, since the early 1980s the system focus shifted to SMFs by exploiting the zero material dispersion characteristic of silica fibers, which occurs at a wavelength of 1280 nm [3] in close proximity to its second low-loss wavelength window centered at 1310 nm [4].

The next revolution in lightwave communication took place when broadband optical fiber amplifiers in the form of erbium-doped fiber amplifiers (EDFA) were developed in 1987 [5], whose operating wavelengths fortuitously coincided with the lowest-loss transmission wavelength window of silica fibers centered at 1550 nm [6] and heralded the emergence of the era of dense wavelength division multiplexing (DWDM) technology in the mid-1990s [7]. By definition, DWDM technology implies simultaneous optical transmission through one SMF of at least four wavelengths within the gain bandwidth of an EDFA (Fig. 1.1). Recent development of the so-called AllWave

and SMF-28e

fibers devoid of the characteristic OH⁻ loss peak (centered at 1380 nm) extended the low-loss wavelength window in high-silica fibers from 1280 nm (235 THz) to 1650 nm (182 THz), thereby offering, in principle, an enormously broad 53 THz of optical transmission bandwidth to be potentially tapped through the DWDM technique! These fibers are usually referred to as enhanced SMF (G.652.C) and are characterized with an additional low-loss window in the E-band (1360-1460 nm), which is about 30% more than the two low-loss windows centered about 1310 and 1550 nm in legacy SMFs. The emergence of DWDM technology has also driven development of various specialty fibers and all-fiber components for seamless growth of the lightwave communication technology. These fibers were required to address new features like nonlinearity-induced potential impairments in optical transmission due to large optical throughput, broadband dispersion compensation, bend-loss sensitivity to variation in signal wavelengths, and so on.

FIGURE 1.1 Schematic representing DWDM optical transmission with a minimum of four wavelengths in the EDFA band as a sample.

In this chapter we attempt to present evolutionary trends in the design of single-mode optical transmission fibers, in particular for lightwave communication seen in the last 30 years or so. Multimode fibers in the form of plastic fibers, which hold promise for on-premise and other applications, are discussed in Chapter 2 authored by P. L. Chu.

2 OPTICAL TRANSPARENCY

2.1 Loss Spectrum

SMFs constitute an integral component of any DWDM link meant to transport high volumes of signals and data. Its characteristics greatly influence the choice of auxiliary components that go into a network and also the overall cost and eventual performance of the communication system. Loss and dispersion spectra are the two most important propagation characteristics of a single-mode optical fiber. Figure 1.2 gives an example of the loss spectrum of a state-of-the-art, commercially available, conventional G.652 type of SMF. Except for a portion of the loss spectrum around 1380 nm at which a peak appears due to absorption by minute traces (in parts per billion) of OH⁻ present in the fiber, the rest of the spectrum in a G.652 fiber more or less varies, with wavelength as Aλ⁻⁴, meaning that signal loss in a state-of-the-art SMF is essentially caused by Rayleigh scattering. Rayleigh scattering loss coefficient A in a fiber may be approximately modeled through the relation [8]

FIGURE 1.2 A sample loss spectrum (full curve) of a state-of-the-art G.652 type single-mode fiber, e.g. SMF-28: (a) 1.81 dB/km at 850 nm, (b) 0.35 dB/km at 1300 nm, (c) 0.34 dB/km at 1310-nm, (d) 0.55 dB/k...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• Preface
• Contributors
• Chapter 1: Optical Fibers for Broadband Lightwave Communication: Evolutionary Trends in Designs
• Chapter 2: Recent Development of a Polymer Optical Fiber and its Applications
• Chapter 3: Microstructured Optical Fibers
• Chapter 4: Photonic Bandgap–Guided Bragg Fibers
• Chapter 5: Radial Effective Index Method for the Analysis of Microstructured Fibers
• Chapter 6: Some Important Nonlinear Effects in Optical Fibers
• Chapter 7: Fiber Optic Parametric Amplifiers for Lightwave Systems
• Chapter 8: Erbium-Doped Fiber Amplifiers
• Chapter 9: Fiber Optic Raman Amplifiers
• Chapter 10: Application of Numerical Analysis Techniques for the Optimization of Wideband Amplifier Performances
• Chapter 11: Analog/Digital Transmission with High-Power Fiber Amplifiers
• Chapter 12: Erbium-Doped Fiber Amplifiers for Dynamic Optical Networks
• Chapter 13: Fused Fiber Couplers: Fabrication, Modeling, and Applications
• Chapter 14: Side-Polished Evanescently Coupled Optical Fiber Overlay Devices: A Review
• Chapter 15: Optical Fiber Gratings
• Chapter 16: Enhancing Photosensitivity in Optical Fibers
• Chapter 17: Solitons in a Fiber Bragg Grating
• Chapter 18: Advances in Dense Wavelength Division Multiplexing/Demultiplexing Technologies
• Chapter 19: Dispersion-Tailored Higher Order Mode Fibers for In-Fiber Photonic Devices
• Chapter 20: Acousto-Optic Interaction in Few-Mode Optical Fibers
• Chapter 21: Basic Theory and Design Procedures for Arrayed Waveguide Structures
• Chapter 22: Photobleached Gratings in Electro-Optic Waveguide Polymers
• Chapter 23: Optical MEMS Using Commercial Foundries
• Chapter 24: Principles of Fiber Optic Sensors
• Chapter 25: Structural Strain and Temperature Measurements Using Fiber Bragg Grating Sensors
• Chapter 26: Principles and Status of Actively Researched Optical Fiber Sensors
• Author Biography
• Index