Here we report on the first CENAM realization of the phase-shift method for chromatic dispersion measurements in
mono-mode phase-shifted optical fibers used for the telecommunications C-band (1 550 nm). This chromatic dispersion
measurement and calibration capability development at CENAM will provide the Mexican telecommunications industry
with a formally established SI units traceability source, thus promoting this rapidly growing and high impact economic
sector competitiveness in Mexico. We also identified a 40 MHz modulation frequency, a 2.5 nm wavelength step and the
1 535 nm to 1 570 nm wavelength scanning range, as the optimum experimental parameters that have to be set in order
to obtain experimental data which numerical Sellmeier polynomials fittings produce representative determinations for
the group delay and the chromatic dispersion. We also obtained 1 549.388 nm ± 0.098 nm, (k=1), for the zero dispersion
wavelength, and 0.719 7 ps-nm<sup>-2</sup> ± 0.005 5 ps·nm<sup>-2</sup>, (k=1), for the zero dispersion slope of the tested optical fiber.
An optical system for real-time measurements on a turning surface was designed and implemented in the optical
metrology laboratory at CICATA-IPN. Different profiles of machined parts can be determined using a single
detector or a photo-diode array. The basis of the measurement is the scattering of a laser beam which is reflected
by the turning surface. Two different configurations were tested, the first one uses a single photodetector and a
commercial lock-in amplifier, and the second uses a photodetector array and a proprietary platform. The samples
under test were mounted on two different lathes for each configuration. The samples were rotating while the
measurements were taken by the electronic system. Under these conditions it was possible to detect the intensity
changes of the scattered light in the single detector case, and changes of the spread in the intensity distribution
in the multidetector case. With the acquired data, qualitative profiles of the samples were obtained, with
promising results. Potential applications in industry are straightforward when surface inspection is necessary to
asses product's quality.
An optical set-up was developed to measure transmitted and scattered light in real time using a photodiode array as a
detector and tested during starch heating. Statistical parameters calculated were Partial Integrated Scattering (PIS) and
variance. Understanding behavior of starch under heat treatment in the presence of water is very important in food
industry. The structure of heated starch granule changes depending on different factors like pH, solvent type and amount,
enzime presence, amylose/amylopectin relation, etc., such changes has been attempted by using several techniques. In
this work, solutions in distilled water of amylopectin, were evaluated. Calcium hydroxide solution was also tested and
mixed with previous amylopectin samples to evaluate any interaction in a two-phase system. A close relationship was
found between the observed optical signals with literature reported structure changes in starch, demonstrating that the
system developed has potential to be used in a real industrial process for monitoring and control.
Development of experimental setup to study strain/stress state in materials emerges from a need to evaluate by a nondestructive
and non-invasive technique the performance in new materials like semiconductor heterostructures, composite
materials and alloys. The system was designed and built to be used as a multi-functional experimental setup. The main
purpose is to characterize materials in elastic and plastic regime by reflectance difference laser measurements and strain
gages. This system allows the generalization of results obtained from a theoretical model based in Finite Element Model
and experimental measurements taken in finite specific points with strain gages. A NI™ platform is used for signal
conditioning and processing. System built is described which includes an optical setup to measure reflectance difference
laser (RDL), and a flexor which applies deformation in a link, with a micrometer. A correlation bigger than 0.95 was
found between optical signal, strain gage signal, and finite element modeling.
Solutions of bovine serum albumin protein were heated from 30 to 85°C in a temperature-controlled optical cell
equipped with air-convective and ohmic heating systems. A polarized laser beam passed through a photo-elastic
modulator was used to measure system changes in optical rotation. Results using both the air-convective and the ohmic
heating systems showed that when the protein system was heated, an increase in absolute value of optical rotation
occurred close to the temperature of denaturation of the protein. Both heating systems were compared, evaluating data
points spread and variation in calculated temperature of denaturation for the replicates. Although no improvement in
these parameters was obtained with ohmic heating when compared to those obtained with the air-convective system, the
optical change related to protein denaturation was more clearly observed. Because ohmic heating strongly interacts with
the sample under study, samples with low polarity and not susceptible to electrolysis should be used to avoid electrical
effects; regardless, ohmic heating coupled to optical systems could also be a useful tool for the evaluation of interaction
of electric field with biological systems optically active.
In this study, the objective was to evaluate optical properties of a corn starch-water mixture as descriptors of its behavior
under processing conditions. A solution of corn starch in water was prepared and heated from 25 to 85°C in a
temperature-controlled optical cell. For the measurement of optical properties, a polarized laser beam modulated through
a photoelastic modulator and an analyzer, was used as optical probe. It was possible to measure transmitted light, along
with optical rotation. Optical measurements showed changes related to temperature dependent phenomena such as starch
granule swelling and gelatinization, in the ranges 25 to 60°C, 60 to 85°C. Above 80°C transmission values were higher,
due to the solution clarification caused by corn starch gelatinization. Regarding optical rotation, it was difficult to obtain
reliable measurements at low temperatures due to the high turbidity of the system. However, once gel was formed at
higher temperatures, optical rotation and light transmission increased. This study demonstrated that optical techniques
are suitable for the study of the behavior of water-starch mixtures under processing conditions such as heating, revealing
a promising future for the monitoring of such phenomena in the production line to lower costs and improve product quality.
We present results of optical measurements in products or processes usually found in industrial processes, which can be used to control them. Laser light scattering was employed during semiconductor epitaxial growth by molecular beam epitaxy. With this technique, it was possible to determine growth rate, roughness and critical temperatures related to substrate degradation. With the same scattering technique, oil degradation as function of temperature was monitored for different automotive lubricants. Clear differences can be studied between monograde and multigrade oils. Optical rotation measurements as function of temperature were performed in apple juice in a pasteurization process like. Average variations related to optical rotation dependence of sugars were measured and monitored during heating and cooling process, finding a reversible behavior. As opposite behavior, sugar-protein solution was measured in a similar heating and cooling process. Final result showed a non-reversible behavior related to protein denaturation. Potential applications are discussed for metal-mechanic, electronic, food, and pharmaceutical industry. Future improvements in optical systems to make them more portable and easily implemented under typical industry conditions are mentioned.
An optical system was developed using a low-cost semiconductor laser and commercial optical and electronic components, to monitor food processes by measuring changes in optical rotation (OR) of chiral compounds. The OR signal as a function of processing time and sample temperature were collected and recorded using a computer data acquisition system. System has been tested during two different processes: sugar-protein interaction and, beer fermentation process. To study sugar-protein interaction, the following sugars were used: sorbitol, trehalose and sucrose, and in the place of Protein, Serum Albumin Bovine (BSA, A-7906 Sigma-Aldrich). In some food processes, different sugars are added to protect damage of proteins during their processing, storage and/or distribution. Different sugar/protein solutions were prepared and heated above critical temperature of protein denaturation. OR measurements were performed during heating process and effect of different sugars in protein denaturation was measured. Higher sensitivity of these measurements was found compared with Differential Scanning Calorimetry, which needs higher protein concentration to study these interactions. The brewing fermentation process was monitored in-situ using this OR system and validated by correlation with specific density measurements and gas chromatography. This instrument can be implemented to monitor fermentation on-line, thereby determining end of process and optimizing process conditions in an industrial setting. The high sensitivity of developed OR system has no mobile parts and is more flexible than commercial polarimeters providing the capability of implementation in harsh environments, signifying the potential of this method as an in-line technique for quality control in food processing and for experimentation with optically active solutions.