Specific wavelength colorimeter

A self contained, specific wavelength, single beam colorimeter is described for direct spectrophotometric measurement of the concentration of a given solute in a test sample. An electrical circuit employing a photoconductive cell converts the optical output into a linear, directly readable meter output. The colorimeter is simple to operate and is adapted for use in zero gravity conditions. In a specific application, the colorimeter is designed to analyze the concentration of iodine in potable water carried aboard a space vehicle such as the 4B stage of Skylab

Generation of pulsed dual wavelength erbium doped fiber laser

Single and dual wavelength fiber lasers and pulsed fiber lasers are well-known to be used for various applications. In the generation of dual wavelength fiber lasers and pulsed fiber lasers, the researchers found the mode competition among the dual wavelength is caused by the cross-gain saturation and strong homogeneous line broadening faced by erbium doped fiber (EDF). Therefore, the aim of this thesis is to generate a single and dual wavelength fiber laser and pulsed fiber laser by using fiber Bragg grating (FBG) in single ring and Figure-8 configurations at 1550 nm and 1560 nm. Analysis and optimization on single wavelength fiber laser and single wavelength pulsed fiber laser give a peak power of -10.70 dBm (8.51x10-2 mW) and -54.01 dBm (3.97x10-6 mW) with signal to noise ratio (SNR) of 59.70 dB and 10.29 dB, respectively, at 1550 nm. Similarly, at 1560 nm, this gives a peak power of -13.60 dBm (4.37x10-2 mW) and -60.00 dBm (1.00x10-6 mW) with SNR of 57.60 dB and 8.78 dB, respectively. For dual wavelength fiber laser and dual wavelength pulsed fiber laser, this gives a peak power of -12.90 dBm (5.13x10-2 mW) and -54.03 dBm (3.95x10-6 mW) at 1550 nm and a peak power of -14.80 dBm (3.24x10-2 mW) and -57.99 dBm (1.59x10-6 mW) at 1560 nm, respectively. The SNR obtained for 1550 nm and 1560 nm for dual wavelength fiber laser and dual wavelength pulsed fiber laser are 55.38 dB and 11.16 dB and 53.58 dB and 11.27 dB, respectively. The repetition rate of single and dual wavelength pulsed fiber laser is 2.878 MHz. It can be concluded that single and dual wavelength fiber lasers are successfully generated using single ring and figure-8 configurations whereas single and dual wavelength pulsed fiber laser are generated using only Figure-8 configuration due to mode locking occurrence. The polarization inside the cavity is controlled to solve mode competition and homogeneous in EDF, in order to obtain a stable dual wavelength

Infrared tunable laser

A tunable laser apparatus is reported with a first wavelength selective reflector and a second wavelength selective reflector forming one end of an optical cavity, and a third wavelength selective reflector forming the other end of an optical cavity. A first lasable dye solution develops radiation of a wavelength selected by the first reflector and a second lasable dye solution develops radiation of a wavelength selected by the second reflector and a non-linear mixing crystal disposed within the optical cavity. The selected radiation is passed through the nonlinear mixing crystal causing it to develop radiation of a third wavelength which is transmitted out of the optical cavity through the third reflector

Multichannel operation of an integrated acousto-optic wavelength routing switch for WDM systems

Polarization independent acousto-optic tunable filters (PIAOTF's) can operate as transparent wavelength-selective crossconnects to route signals in wavelength division multiplexed optical networks. In this paper, a new low power PIAOTF is characterized as a switch in multiwavelength operation, using four equally spaced lightwave signals with wavelengths between 1546 nm and 1558 nm. Interchannel interference due to sidelobe excitation is lower than -11 dB for single wavelength switching and is equal to -6 dB in the extreme case of simultaneous switching of all wavelength channels. Sources of interport and interchannel crosstalk for single and multiple wavelength switching are identified

Studies on Temperature and Strain Sensitivities of a Few-mode Critical Wavelength Fiber Optic Sensor

This paper studied the relationship between the temperature/strain wavelength sensitivity of a fiber optic in-line Mach-Zehnder Interferometer (MZI) sensor and the wavelength separation of the measured wavelength to the critical wavelength (CWL) in a CWL-existed interference spectrum formed by interference between LP01 and LP02 modes. The in-line MZI fiber optic sensor has been constructed by splicing a section of specially designed few-mode fiber (FMF), which support LP01 and LP02 modes propagating in the fiber, between two pieces of single mode fiber. The propagation constant difference, Δβ, between the LP01 and LP02 modes, changes non-monotonously with wavelength and reaches a maximum at the CWL. As a result, in sensor operation, peaks on the different sides of the CWL then shift in opposite directions, and the associated temperature/strain sensitivities increase significantly when the measured wavelength points become close to the CWL, from both sides of the CWL. A theoretical analysis carried out has predicted that with this specified FMF sensor approach, the temperature/strain wavelength sensitivities are governed by the wavelength difference between the measured wavelength and the CWL. This conclusion was seen to agree well with the experimental results obtained. Combining the wavelength shifts of the peaks and the CWL in the transmission spectrum of the SFS structure, this study has shown that this approach forms the basis of effective designs of high sensitivity sensors for multi-parameter detection and offering a large measurement range to satisfy the requirements needed for better industrial measurements

Effect of wavelength dependence of nonlinearity, gain, and dispersion in photonic crystal fiber amplifiers

Photonic crystal fibers are used in fiber amplifiers and lasers because of the flexibility in the design of mode area and dispersion. However, these quantities depend strongly on the wavelength. The wavelength dependence of gain, nonlinearity and dispersion are investigated here by including the wavelength dependence explicitly in the nonlinear Schr\"odinger equation for photonic crystal fibers with varying periods and hole sizes. The effect of the wavelength dependence of each parameter is studied separately as well as combined. The wavelength dependence of the parameters is shown to create asymmetry to the spectrum and chirp, but to have a moderating effect on pulse broadening. The effect of including the wavelength dependence of nonlinearity in the simulations is demonstrated to be the most significant compared that of dispersion or gain

Polarimetry SAR detectors for monitoring Mediterranean forest fires events

Over the past decades, the great technological advances made in airborne and space sensors have led to a significant improvement of the remote sensing methods and techniques used for studying worldwide natural ecosystem disturbances. Generally, optical sensors are chosen for investigating landscapes transformation, however, this technology requires certain technical and environmental conditions (sunlight, no cloud-coverage) which are problematic for monitoring some regions of the world. In response to this challenge, this research aims to highlight the capabilities of Synthetic Aperture Radar - SAR satellite sensors for detecting disturbances in Mediterranean forests due to fire events. We are exploring three different methodologies: 1. Monitoring image intensity changes in dense time series of radar data; 2. We are investigating soil moisture changes after the fire that can be detected in intensities of radar images; 3. We are testing novel polarimetric SAR change detectors that are able to extract more information from polarimetric data (intensities and cross-correlations between polarimetric channels). All the procedures in this project were developed by using Co & Cross polarised radar satellite data acquired by the ESA-Sentinel-1 system in C-band, using the Doñana national park (Spain) forest fire event in June-July 2017 as a case study