The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
Aalto

Applications of Fiber Optical Resonators in Measurement and Telecommunications Technology

Tuomo von Lerber

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Electrical and Communications Engineering for public examination and debate in Micronova at Helsinki University of Technology (Espoo, Finland) on the 5th of October, 2007, at 12 noon.

Overview in PDF format (ISBN 978-951-22-8902-8)   [1057 KB]
Dissertation is also available in print (ISBN 978-951-22-8901-1)

Abstract

The advent of optical fibers has greatly impacted the modern technology landscape. Most notably, existing telecommunications infrastructure relies on optical fiber networks, which have the ability to transmit high-bandwidth data over considerable distances. Optical fibers have also visible foothold in the field of metrology, where they are used as sensors in various applications.

An optical resonator is a basic building block of many optical devices, such as lasers, measurement probes, and optical signal processing equipment. In this dissertation we propose new methods and tools for metrology and general telecommunications sciences based on fiber optical resonators. Compared to conventional free-space technology, fiber resonators enable easy connectivity and they are shown to be robust against ambient perturbations.

This thesis consists of two parts that concentrate on optical measurement and signal processing technology, respectively. The first part introduces new measurement schemes for fiber loss and minute birefringence quantification. A loss of an optical fiber medium is measured using a so-called fiber cavity ring-down method. In presence of an external source of loss, such as fiber bending or degradation, one may obtain information about the environment of the probe. Another scheme measures birefringence and, thus, the beat length of a short fiber section. We also suggest a computational method for resonator photon lifetime (also called resonator time constant) extraction under noisy signal conditions. We demonstrate that the developed algorithm may yield meaningful results even when conventional methods fail.

The second part of the thesis deals with all-optical signal processing and temporal data synchronization. In a proof-of-principle experiment we perform an all-optical clock recovery for 21 parallel wavelength channels at two simultaneous data rates. The method relies on a birefringent optical resonator, whose transmission spectrum is used to filter carrier and sideband frequencies of return-to-zero-modulated data for multiple wavelength channels. In another clock recovery experiment we investigate the possibility to use sideband filtered signal, combined with a continuous wave light emitted at the carrier wavelength.

This thesis consists of an overview and of the following 5 publications:

  1. T. von Lerber and M. W. Sigrist, Cavity-ring-down principle for fiber-optic resonators: experimental realization of bending loss and evanescent-field sensing, Applied Optics 41, 3567-3575 (2002).
  2. T. von Lerber and M. W. Sigrist, Time constant extraction from noisy cavity ring-down signals, Chemical Physics Letters 353, 131-137 (2002).
  3. T. von Lerber, H. Ludvigsen, and A. Romann, Resonator based measurement technique for quantification of minute birefringence, Optics Express 12, 1363-1371 (2004).
  4. T. von Lerber, J. Tuominen, H. Ludvigsen, S. Honkanen, and F. Kueppers, Multichannel and rate all-optical clock recovery, IEEE Photonics Technology Letters 18, 1395-1397 (2006).
  5. T. von Lerber, J. Tuominen, H. Ludvigsen, S. Honkanen, and F. Küppers, Investigation of multiwavelength clock recovery based on heterodyne beats of sideband-filtered signal, Optics Communications 271, 87-90 (2007).

Errata of publication 3

Keywords: optical fiber, resonator, cavity ring-down, clock recovery, birefringence

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© 2007 Helsinki University of Technology


Last update 2011-05-26