Characterisation of Optical Fibers Using Dual-Comb Swept-Wavelength Interferometry

The growth in data traffic coupled with trends in internet use will result in a requirement for interfaces of the network to reach Tb/s data rate in the future. Considering this, novel transmission techniques that can increase the date rate with orders of magnitude must be considered. One such example is space-division multiplexing (SDM) fibers. Application of novel fibers and SDM components in communication systems is always coupled with limitations and distortions of the signal due to crosstalk, dispersion, differential mode group delay (DMGD) and other effects. They can be calculated, studied and partially mitigated if the transfer function of the fiber under test is known. Thus, it is essential to characterize the fiber\u27s and other component\u27s transfer matrix using fast and accurate measurement techniques. Moreover, these characterisation measurements can be used for building channel models, which can assist in simulations of the transmission and estimation of ultimate system performance.In this thesis various techniques for SDM devices characterisation are described and a novel method based on dual-comb spectroscopy and swept-wavelength interferometry is proposed and evaluated. The presented technique, dual-comb swept-wavelength interferometry (DC-SWI), is studied in terms of capabilities, advantages and limitations with application on different devices under test. This experimental scheme is also used for characterisation of a coupled-core fiber, where the transfer function and DMGD values were extracted.Furthermore, different channel models describing the properties of SDM fiber links are briefly reviewed and discussed

Spectral Interferometry with Frequency Combs

In this review paper, we provide an overview of the state of the art in linear interferometric techniques using laser frequency comb sources. Diverse techniques including Fourier transform spectroscopy, linear spectral interferometry and swept-wavelength interferometry are covered in detail. The unique features brought by laser frequency comb sources are shown, and specific applications highlighted in molecular spectroscopy, optical coherence tomography and the characterization of photonic integrated devices and components. Finally, the possibilities enabled by advances in chip scale swept sources and frequency combs are discussed

Dual-Comb Swept-Wavelength Interferometry: Theory and Experiment

Much efforts have been put to elaborate and improve different high precision measurement schemes for characterization of advanced photonic devices and optical fibers with increasing bandwidth requirements. In light of this, swept-wavelength interferometry and dual-comb spectroscopy have been extensively applied in characterization procedures. In this paper we present in detail an experimental scheme that combines these two techniques and overcomes their limitations by using a tunable laser source in order to sweep over the frequency comb spacing and capture all intermediate frequencies. We demonstrate full-field broadband measurements over 1.25 THz comb bandwidth with increased frequency resolution, which can be performed in only 5\ua0ms sweep. We also show that the nonlinearity of the laser sweep can be removed without an auxiliary interferometer in the setup

Characterisation of a Coupled-Core Fiber Using Dual-Comb Swept-Wavelength Interferometry

We present a measurement of the transfer matrix of a coupled three-core fiber using a novel combination of swept-wavelength interferometry and dual-comb spectroscopy capable of measuring 1 THz bandwidth with a frequency resolution of 50 kHz with only a 25 GHz laser sweep