Ignacio Garcés

Mode coupling contribution to radiation losses in curvatures for high and low numerical aperture plastic optical fibers

We have studied the optical power losses due to multiple curvatures in polymethylmetacrylate (PMMA) plastic optical fibers (POFs) of different numerical apertures (NAs) and attenuation. The fibers were tested for several configurations in order to assess the influence of different types of curved-to-straight fiber transitions in the amount of power radiation. We found that losses are below the standards for all tested fiber types, and thus, they are a suitable choice for local area network (LAN) applications. In addition, our results revealed the presence of modal interactions as confirmed using an experimental procedure to estimate the mode coupling strength for the same fibers.

Global characterization of optical power propagation in step-index plastic optical fibers.

We propose to characterize optical power transmission in stepindex plastic optical fibers by estimating fiber diffusion and attenuation as functions of the propagation angle. We assume that power flow is described by Gloge s differential equation and find a global solution that was fitted to experimental far field patterns registered using a CCD camera as a function of fiber length. The diffusion and attenuation functions obtained describe completely the fiber behavior and thus, along with the power flow equation, can be used to predict the optical power distribution for any condition.

Characterization of the Main Semiconductor Laser Static and Dynamic Working Parameters From CW Optical Spectrum Measurements

We present a complete characterization of the work parameters of several types of semiconductor lasers. Static parameters as: power, linewidth and linewidth enhancement factor and also dynamic parameters such as: relaxation oscillations, relative intensity noise and damping rates are calculated using measurements of the optical spectrum of the lasers operated in continuous-wave mode. Methods for the calculation of these parameters are described and applied to the lasers under test by means of a single general setup and a single set of measurements

Analysis of leakage properties and guiding conditions of rib antiresonant reflecting optical waveguides

Power leakage properties and guiding conditions of rib antiresonant reflecting optical waveguides (rib-ARROW) have been theoretically and experimentally studied as a function of wavelength and polarization of the light for different geometrical and optical parameters that characterize the rib-ARROW structure. Obtained results show that rib-ARROWs can only be fabricated with low losses in a wavelength range when determined rib configurations are adopted. Furthermore, these waveguides exhibit a polarization sensitivity that largely depends on the core-substrate refractive index difference. Together with the experimental results, theoretical calculations from different modeling methods are also presented and discussed.

Measurement of the linewidth enhancement factor in DFB lasers using a high-resolution optical spectrum analyzer

Linewidth enhancement factor (also know as chirp parameter is calculated for two distributed feedback lasers using the linewidth asymptotic behavior predicted by Schawles-Townes and Henry. A high-resolution optical spectrum analyzer (BOSA) is used to measure power and linewidth. Comparison with widely accepted network analyzer method is performed with very good agreement.

Stimulated Brillouin scattering gain profile characterization by interaction between two narrow-linewidth optical sources

We report on results from the characterization of Stimulated Brillouin Scattering (SBS) spectra for standard single-mode fiber produced by the interaction between two counter-propagating tunable laser sources (TLS) using one as the probe signal to measure and the other as the pump, sweeping a wide span around the signal. Assuming TLS linewidth negligible against SBS gain bandwidth, we measure SBS spectrum for a wide range of pump and probe signal power levels and study the evolution of relevant SBS parameters such as linewidth and gain profile. High signal to noise ratio measurements allows analyzing the evolution of the SBS gain profile from Lorentzian to Gaussian as predicted by current theory of SBS and the use of SBS response for filtering applications.

Precise characterization of the frequency chirp in directly modulated DFB lasers

We report on results from the characterization of the frequency chirp characteristics of distributed feedback (DFB) lasers under direct modulation conditions. Parameters describing transient and adiabatic chirp effects are measured for a DFB laser from the ratio of phase to amplitude modulation factors when modulated with sine waves using a high-resolution optical spectrum analyzer. Transient and adiabatic chirp effects produced under digital non-return to zero (NRZ) amplitude modulation are also analyzed using the emitted optical spectrum. Finally, results from the measurement technique are compared with those obtained from measured optical spectra.

Analysis of optochemical absorbance sensors based on bidimensional planar ARROW microoptics

Abstract A new approach for developing absorbance optochemical sensors is presented in this paper. It is based on a planar microoptic circuit where an optochemically active membrane, which responds selectively to a compound, is deposited in the device, yielding a part of the guiding planar structure. Light is propagated through the membrane, which changes its spectral absorption properties and controls the selectivity of the measurements by means of several immobilised compounds. This way, high sensitivity of the device can be easily obtained due to relatively long light paths through the membrane, and low response times can be achieved as the analyte diffusion occurs perpendicularly to the light path and through a thin membrane. Experimental results on measurements of the concentration of a specific ion in solution using the fabricated sensors are also presented.

Linewidth Enhancement Factor of Semiconductor Lasers: Results from Round-Robin Measurements in COST 288

Round-robin measurements on the linewidth enhancement factor are carried out within several laboratories participating to EU COST 288 action. The alpha-factor is measured by applying up to 7 different techniques. The obtained results are compared.

Multiple-bit all-optical logic based on cross-gain modulation in a semiconductor optical amplifier

In this paper we have evaluated the non-linear response of a semiconductor optical amplifier (SOA) in terms of Cross Gain Modulation effect (XGM). The different ranges of optical power that make the SOA work as a logic gate have been determined, as well as the optimum relation between inputs to obtain the best response. Taking into account the SOA response, a schematic model for an all-optical 4-input NOR gate using a single SOA has been proposed. Our experimental set-up has been tested with four streams of 10 Gbps RZ data to verify the proper and stable operation of the NOR gate under diverse power levels for each data input. The logic output has been evaluated for different inputs using an optical eye diagram to verify its quality; in addition, the possibility of using the NOR output as the input to other logical semiconductor structures, which would allow to chain multiple gates, has been demonstrated. The concatenation of NOR gates allows to build more complex all-optical devices which will permit the design of advanced mechanisms in the field of transparent networks, such as comparators or look-up tables for switching nodes, without the necessity of optical-electrical conversion.