Measurement of optical fiber parameters and thermal core diffusion characteristics by digital image processing.

The simultaneous measurement of the numerical aperture (NA) and mode field diameter (MFD) of single-mode fibers was performed on several commercial fibers by means of digital image processing of the output light projected into a screen. In addition, the changes induced by core diffusion in an ultra-high (UH) NA fiber at several heat depositions from a CO2 laser source were measured. The measurement method was demonstrated to be useful to monitor the adiabaticity of this process, by taking the product of the NA and MFD to verify if it remains constant. The method provides a cheap alternative to measure these optical fiber parameters by using simple optomechanical elements and a readily available smartphone camera, and it can be easily implemented in the laboratory.

Experimental optimization of concatenated taper Mach-Zehnder interferometers operating in the 1000-1150 nm wavelength range.

Experimental optimization of all fiber Mach-Zehnder interferometers based on concatenated tapers is presented. The experimental optimization was realized by the application of the four parameters Taguchi algorithm, and the insertion loss of comb filters operating around the 1064 nm wavelength was taken as the parameter to be optimized. The out of band losses were reduced from around 2.5 dB (43.7%) to a minimum of 0.45 dB (9.84%) in one case, and from 2.9 (48.71%) to 0.4 dB (8.79%) by using a fixed tapers pair's geometry with 1 mm×1 mm×1 mm of up-taper length/waist length/down-taper length, respectively, and a waist diameter of 40 µm.