Francisco Javier Fraile-Peláez

Transmission bistability in a double-coupler fiber ring resonator.

The transmission bistability of a two-coupler nonlinear ring resonator is demonstrated and described by using a geometrical method that provides a qualitative understanding of the operation characteristics of the device. Results showing the influence of the coupling constants and the linear phase are presented.

Fast and slow light in zigzag microring resonator chains

We analyze fast- and slow-light transmission in a zigzag microring resonator chain. In the superluminal case, a new light-transmission effect is found whereby the input optical pulse is reproduced in an almost-simultaneous manner at the various system outputs. When the input carrier is tuned to a different frequency, the system permits to slow down the propagating optical signal. Between these two extreme cases, the relative delay can be tuned within a broad range. We propose, and analyze numerically, a laser-array configuration for the stable operation of active devices.

Study of Optimal All-Pass Microring Resonator Delay Lines With a Genetic Algorithm

We study the properties of finite-length all-pass side-coupled microring delay lines optimized using a genetic algorithm. The average bandwidth-group delay product is found to follow a linear growth with the number of cascaded stages N. Both the magnitude and the slope of the figure of merit vary with the specific optimization criteria but, for all the cases addressed, they are below the unit slope linear dependence with N of a theoretical upper bound.

Continuum states and fields in quantum optics

The relation between the continuous-mode quantization scheme used in quantum optics and the quantum system formed by a continuum of standard harmonic oscillators is established. The number and coherent states of this system are shown to be the ones introduced without explicit reference to the continuum by other authors.

Ultra-short pulse propagation model for multi-core fibers based on local modes

Multi-core fibers (MCFs) have sparked a new paradigm in optical communications and open new possibilities and applications in experimental physics and other fields of science, such as biological and medical imaging. In many of these cases, ultra-short pulse propagation is revealed as a key factor that enables us to exploit the full potential of this technology. Unfortunately, the propagation of such pulses in real MCFs has not yet been modelled considering polarization effects or typical random medium perturbations, which usually give rise to both longitudinal and temporal birefringent effects. Using the concept of local modes, we develop here an accurate ultra-short pulse propagation model that rigorously accounts for these phenomena in single-mode MCFs. Based on this theory, we demonstrate analytically and numerically the intermodal dispersion between different LP01 polarized core modes induced by these random perturbations when propagating femtosecond pulses in the linear and nonlinear fiber regimes. The ever-decreasing core-to-core distance significantly enhances the intermodal dispersion induced by these birefringent effects, which can become the major physical impairment in the single-mode regime. To demonstrate the power of our model, we give explicit strategies to reduce the impact of this optical impairment by increasing the MCF perturbations.

Characterization of a FBG sensor interrogation system based on a mode-locked laser scheme

This paper is focused on the characterization of a fiber Bragg grating (FBG) sensor interrogation system based on a fiber ring laser with a semiconductor optical amplifier as the gain medium, and an in-loop electro-optical modulator. This system operates as a switchable active (pulsed) mode-locked laser. The operation principle of the system is explained theoretically and validated experimentally. The ability of the system to interrogate an array of different FBGs in wavelength and spatial domain is demonstrated. Simultaneously, the influence of several important parameters on the performance of the interrogation technique has been investigated. Specifically, the effects of the bandwidth and the reflectivity of the FBGs, the SOA gain, and the depth of the intensity modulation have been addressed.

Phase Asymmetry Effect in Longitudinal Offset Coupled Resonator Optical Waveguides

We show that the implementation of the longitudinal displacement technique for adjusting the coupling coefficients in microring waveguides is subject to a phase asymmetry effect. This issue is shown to substantially alter the system response in apodized filters and cannot be ignored in the design stage.

Optical Regeneration Using Nonlinear Interaction in Slow-Wave Microring Resonator Chains

We propose the use of slow-wave micro-ring resonator chains with saturable loss as optically controllable group delays for the retiming of optical signal in communication links. The proposed scheme is analyzed using numerical simulation.

Performance analysis of optical prefiltering-SCM systems by accurate spectral techniques

We present a detailed study of the dc optical prefiltering (OP) technique in subcarrier multiplexed (SCM) lightwave systems. A numerical model, including all of the most relevant limiting effects, is used in combination with Pronys method in order to obtain an accurate assessment of analog transmission systems performance. Intrinsic limitations of the dc-OP technique are highlighted and the full numerical results are compared with those obtained from limited analytical approximations.

Characterization of Microring Filters for Differential Group Delay Applications

The longitudinal offset technique permits to improve the accuracy of the coupling coefficients of integrated directional couplers and provides designs that can be easily implemented with current fabrication tolerances. In this paper, we address the additional degree of freedom offered by this technology in order to tailor the differential group delay in coupled-resonator optical filters. We present the characterization of several devices exploiting this feature and we discuss their potential applications.