Javier Lasobras

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

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.

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.

Infrared sensor-based temperature control for domestic induction cooktops

In this paper, a precise real-time temperature control system based on infrared (IR) thermometry for domestic induction cooking is presented. The temperature in the vessel constitutes the control variable of the closed-loop power control system implemented in a commercial induction cooker. A proportional-integral controller is applied to establish the output power level in order to reach the target temperature. An optical system and a signal conditioning circuit have been implemented. For the signal processing a microprocessor with 12-bit ADC and a sampling rate of 1 Ksps has been used. The analysis of the contributions to the infrared radiation permits the definition of a procedure to estimate the temperature of the vessel with a maximum temperature error of 5 °C in the range between 60 and 250 °C for a known cookware emissivity. A simple and necessary calibration procedure with a black-body sample is presented.

Time-Resolved Chirp Measurements Using Complex Spectrum Analysis Based on Stimulated Brillouin Scattering

A novel method to measure the complex optical spectrum of digitally modulated signals based on stimulated Brillouin scattering (SBS) is presented. Time resolved chirp measurements of a 10 Gbps modulation is performed using this technique.

Complex Spectrum Analysis of Modulated Optical Signals Using Stimulated Brillouin Scattering

We introduce a novel method for the measurement of the spectral phase of modulated optical signals based on double-pump stimulated Brillouin scattering interaction and direct homodyne detection. This technique is combined with Brillouin high-resolution analysis to achieve a complete characterization of the complex optical spectrum. A 10-Gb/s nonreturn-to-zero signal with a 32-bit pattern modulated with an electroabsorption modulator is measured using this technique and its time-domain information (power and chirp) is obtained by inverse Fourier transform.

Novel Phase Spectrum Measurement Method based on Stimulated Brillouin Scattering

A novel method to measure the phase spectrum of modulated optical signals based on stimulated Brillouin scattering is presented. Combined with power spectrum measurements, and through inverse Fourier transform, the time-domain information is recovered.

Radiation heat measurement model for temperature estimation in induction heating appliances

Domestic induction heating system employ the output power as control variable. The users select the desired power level among a set of possible values. The advantage of this strategy is related to the control of the associated power electronics. However, temperature control is preferred for cooking applications but it increases the complexity of the system due to the difficulties associated with the temperature estimation of the cookware. Temperature can be measured by means of contact or non-contact technique. This application demands non-contact temperature measurement due to the cooking surface, generally made of glass-ceramic, separates the cookware to the induction heating system placed bellow. Among others, temperature estimation based on radiation detectors, for instance, thermopiles, constitutes one of the most promising methods due to the immediate determination of the measure, but, the optimization of this method required a complex procedure. The aim of this paper is to provide the numerical model of this kind of the system suitable to be used for design purposes. The simulation results have been compared with analytical and experimental measurements in order to verify the correctness of the numerical model.

Characterization of 1.55 µm VCSELs using high-resolution and high- dynamic range measurements of the CW optical spectrum

We present a methodology for the characterization of the main parameters of VCSELs for its use in direct modulation. Power response, chirp parameter alpha, linewidth, side-mode suppression ratio, relaxation oscillations peak frequency, damping rate and relative intensity noise (RIN) are obtained from measurements of the emitted optical spectrum in continuous wave (CW) operation by means of a high resolution (10 MHz) and high dynamic range (80 dB) optical spectrum analyzer. Many of the main static and dynamic parameters of VCSEL lasers can be obtained from the analysis of the optical spectrum when emitting in CW operation, but traditional spectrum analysis techniques do not achieve enough high resolution and dynamic range and high signal to noise ratio to perform it. Recent developments in high resolution optical spectrum analyzer (OSA) technology allow a deeper characterization of the main properties of VCSELs for its applications in optical communication systems by analyzing their CW emitted spectrum.

DFB laser dynamics and noise characterization by high resolution and high dynamic range measurements of its CW optical spectrum

We present results on the characterization of the main parameters of DFB lasers for its use in direct modulation: chirp parameter, linewidth, relaxation frequency and RIN, obtained from measurements of the emitted optical spectrum in continuous operation mode using a high resolution (10 MHz) and high dynamic range (80 dB) optical spectrum analyzer. Results obtained from the characterization of commercial grade available DFB lasers with this method, present typical parameter values, but are also checked with well-know, but more resource demanding, methods involving modulation and optical to electrical conversion.