**Meet the editor**

Christian Cuadrado-Laborde received his Ph.D. degree in Physics from the University of La Plata (UNLP, Argentina, 2005), and Electric and Electronic Engineer degree from the University of San Luis (UNSL, Argentina, 1998). He is an Associate Researcher of CONICET (2005), the most important federal research agency in Argentina, at the Optical Research Center (CIOp, La

Plata); and also Associate Professor at the Catholic University of La Plata (Argentina). Dr. Cuadrado-Laborde was awarded by the Spanish Ministry of Science with a research fellow position to join to the Optical Fiber Laboratory group headed by M. V. Andrés of the University of Valencia (Spain) during 2008-2009. Since then, he has continued collaborating with this research group. He is editorial board member in the journals Photonics and Optoelectronics and Journal of Optoelectronic Engineering. He serves also as a reviewer for several well-known journals of the Optical Society of America, the IEEE, Elsevier, SPIE, and the Electromagnetic Academy. Dr. Cuadrado-Laborde has published several research papers in top-tier scientific journals such as Optics Letters, Laser & Photonics Reviews, Optics & Photonics News, etc. His current research interest includes fiber optics applications, photonic signal processing, and all-fiber lasers.

Contents

**Preface VII** 

Chapter 1 **A Guide to Fiber Bragg Grating Sensors 1** 

**to a Cylindrical Metal Rod 45** 

Marcelo M. Werneck, Regina C. S. B. Allil, Bessie A. Ribeiro and Fábio V. B. de Nazaré

Chapter 2 **Surface-Corrugated Microfiber Bragg Grating 25**  Fei Xu, Jun-Long Kou, Yan-Qing Lu, Ming Ding and Gilberto Brambilla

Chapter 3 **Fabrication and Mode Coupling of Long-Period Fiber** 

Chapter 4 **Optical Fibre Long-Period Gratings Functionalised with Nano-Assembled Thin Films: Approaches to Chemical Sensing 63** 

Chapter 5 **Long-Period Fiber Gratings in Active Fibers 87** 

Chapter 6 **Photonic Sensors Based on Flexible Materials** 

Chapter 7 **Application of Fiber Bragg Grating Sensors** 

**in Power Industry 133** 

Chapter 8 **Fiber Bragg Grating Technology for** 

Alexandre Ferreira da Silva, Rui Pedro Rocha, João Paulo Carmo and José Higino Correia

Regina C. S. B. Allil, Marcelo M. Werneck, Bessie A. Ribeiro and Fábio V. B. de Nazaré

**New Generation Optical Access Systems 167** 

Oskars Ozolins, Vjaceslavs Bobrovs, Jurgis Porins and Girts Ivanovs

David Krčmařík, Mykola Kulishov and Radan Slavík

**with FBGs for Use on Biomedical Applications 105** 

**Grating by Winding a Wire Around an Optical Fiber Fixed** 

Jonghun Lee, Cherl-Hee Lee, Kwang Taek Kim and Jaehee Park

Sergiy Korposh, Stephen James, Ralph Tatam and Seung-Woo Lee

## Contents

### **Preface XI**


Preface

process.

Applications of both short-and long-period fiber gratings are very diverse, especially the ones related to the optical communications and the optical fiber sensing. In optical communications different tasks such as wavelength selective filtering, add/drop multiplexing and all-optical switching have been performed. Interestingly, optical fiber sensing has unique advantages such as immunity to electromagnetic radiation, high sensitivity, cost-effective relation, etc. And it is widely used to measure stress, temperature, pressure or chemical parameters, among others physical variables,

Thanks to my postdoctoral studies under the supervision of Prof. Miguel Andrés, in the Optical Fiber Laboratory Group of the Valencia University (Spain), I became involved in the field of fiber gratings. Our main aim was to develop strictly all-fiber lasers. In these applications fiber Bragg gratings are currently used as the in-line mirrors of the Fabry-Perot cavity. However we found another use for fiber gratings when we proposed that the propagation of an acoustic wave through a fiber grating could control the laser itself, either in regime of Q-switching, active mode-locking, or both simultaneously. This finding allows the construction of true strictly all-fiber lasers, by replacing the standard bulk optics modulators, by acousto-optic fiber grating -based modulators. This adds a number of advantages to the laser system such as increased mechanical stability, low power-insertion losses, enhanced power efficiency, high peak power damage, low cost, etalon-free effects and simplified assembly

Later on, I continued studying fiber gratings but for a different application: the photonic fractional processing of signals. It is well-known that the inherent speed limitations of conventional electronics can be overcome by all-optical circuits. These circuits should be studied in order to assess their application on the execution of some common mathematical operations. The possible applications for these devices encompass optical pulse shaping, optical computing, information processing systems, and ultrahigh-speed coding, among other uses. Generally and up-to-date, the in-fiber way is preferred, because it offers simplicity, relatively low cost, low insertion loss, polarization independence, and inherent full compatibility with fiber-optic systems. Through our work, we demonstrated that by properly designing a fiber grating the performance of multiple all-optical fractional mathematical operations such as Hilbert

giving in many cases unrivaled resolution capabilities.

## Preface

Applications of both short-and long-period fiber gratings are very diverse, especially the ones related to the optical communications and the optical fiber sensing. In optical communications different tasks such as wavelength selective filtering, add/drop multiplexing and all-optical switching have been performed. Interestingly, optical fiber sensing has unique advantages such as immunity to electromagnetic radiation, high sensitivity, cost-effective relation, etc. And it is widely used to measure stress, temperature, pressure or chemical parameters, among others physical variables, giving in many cases unrivaled resolution capabilities.

Thanks to my postdoctoral studies under the supervision of Prof. Miguel Andrés, in the Optical Fiber Laboratory Group of the Valencia University (Spain), I became involved in the field of fiber gratings. Our main aim was to develop strictly all-fiber lasers. In these applications fiber Bragg gratings are currently used as the in-line mirrors of the Fabry-Perot cavity. However we found another use for fiber gratings when we proposed that the propagation of an acoustic wave through a fiber grating could control the laser itself, either in regime of Q-switching, active mode-locking, or both simultaneously. This finding allows the construction of true strictly all-fiber lasers, by replacing the standard bulk optics modulators, by acousto-optic fiber grating -based modulators. This adds a number of advantages to the laser system such as increased mechanical stability, low power-insertion losses, enhanced power efficiency, high peak power damage, low cost, etalon-free effects and simplified assembly process.

Later on, I continued studying fiber gratings but for a different application: the photonic fractional processing of signals. It is well-known that the inherent speed limitations of conventional electronics can be overcome by all-optical circuits. These circuits should be studied in order to assess their application on the execution of some common mathematical operations. The possible applications for these devices encompass optical pulse shaping, optical computing, information processing systems, and ultrahigh-speed coding, among other uses. Generally and up-to-date, the in-fiber way is preferred, because it offers simplicity, relatively low cost, low insertion loss, polarization independence, and inherent full compatibility with fiber-optic systems. Through our work, we demonstrated that by properly designing a fiber grating the performance of multiple all-optical fractional mathematical operations such as Hilbert

#### VIII Preface

transform, Fourier transform, differentiation, integration, etc. could be achieved. This, in turn, allows the application of these fiber grating based fractional mathematical operators to different tasks, like phase recovering or optical control.

Therefore, and considering that the field of fiber gratings is within my research area of expertise, I proposed to the InTech publisher to edit a book in this area and now I am pleased to say that this idea was favorably received. Today, it is a great honor and pleasure for me to introduce this new book: Current Trends in Short- and Long-period Fiber Gratings. This is my second collaboration as Editor with InTech, after the success of our first book: Applications of Digital Signal Processing (InTech, 2011), which was in the top ten of the most downloaded books for several months. I truly hope that this new book will also be successfully received by the worldwide scientific community.

In this book the reader will find a collection of chapters written by different experts around the world, covering the broad field of fiber gratings. The main goal of this book is to give an updated overview of the current research trends in the rapidly evolving field of fiber gratings.

Finally, I would like to thank all the authors for their contributions since their support has been crucial for the fulfillment of this project. In addition, I would like to thank the InTech editorial staff for the confidence placed in me to edit this book. On behalf of the authors and myself, we hope readers enjoy this book and benefit of its content, which provides a thorough understanding of several fields related to this exciting technology.

> **Christian Cuadrado-Laborde** CIOp (CONICET La Plata-CIC), Buenos Aires, Argentina

VIII Preface

evolving field of fiber gratings.

technology.

transform, Fourier transform, differentiation, integration, etc. could be achieved. This, in turn, allows the application of these fiber grating based fractional mathematical

Therefore, and considering that the field of fiber gratings is within my research area of expertise, I proposed to the InTech publisher to edit a book in this area and now I am pleased to say that this idea was favorably received. Today, it is a great honor and pleasure for me to introduce this new book: Current Trends in Short- and Long-period Fiber Gratings. This is my second collaboration as Editor with InTech, after the success of our first book: Applications of Digital Signal Processing (InTech, 2011), which was in the top ten of the most downloaded books for several months. I truly hope that this new book will also be successfully received by the worldwide scientific community.

In this book the reader will find a collection of chapters written by different experts around the world, covering the broad field of fiber gratings. The main goal of this book is to give an updated overview of the current research trends in the rapidly

Finally, I would like to thank all the authors for their contributions since their support has been crucial for the fulfillment of this project. In addition, I would like to thank the InTech editorial staff for the confidence placed in me to edit this book. On behalf of the authors and myself, we hope readers enjoy this book and benefit of its content, which provides a thorough understanding of several fields related to this exciting

> **Christian Cuadrado-Laborde** CIOp (CONICET La Plata-CIC),

> > Buenos Aires, Argentina

operators to different tasks, like phase recovering or optical control.

**Chapter 1** 

© 2013 Allil et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2013 Allil et al., licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**A Guide to Fiber Bragg Grating Sensors** 

Marcelo M. Werneck, Regina C. S. B. Allil, Bessie A. Ribeiro

Optical fiber sensors (OFS) appeared just after the invention of the practical optical fiber by Corning Glass Works in 1970, now Corning Incorporated, that produced the first fiber with losses below 20 dB/km. At the beginning of this era, optical devices such as laser, photodetectors and the optical fibers were very expensive, afforded only by telecom companies to circumvent the old saturated copper telephone network. With the great diffusion of the optical fiber technology during the 1980's and on, optoelectronic devices

OFS can be applied in many branches of the industry but we will concentrate here the electrical power industry. In this area, the operators need to measure and monitor some

In the electrical power industry (EPI) we have two facts that can cause collapse of an electronic sensor: presence of high voltage and presence of high electromagnetic interference. Therefore, depending on where we want to measure a parameter it can be very difficult or even impossible to use a conventional sensor. The best option to circumvent this

Additional information is available at the end of the chapter

became less expensive, what favored their use in OFS.

important physical parameters that include:

 Vibration of structures and machines Electric current (from A to kA) Voltage (from mV to MV)

Leakage current of insulators (µA to mA)

Distance between stationary and rotating or moving parts

and Fábio V. B. de Nazaré

http://dx.doi.org/10.5772/54682

**1. Introduction** 

Strain (µє)

Impedance (µΩ)

Gas concentration

 Temperature Pressure
