E. A. De Souza

A novel protection mechanism in TDM-PON

The Passive Optical Network (PON) was proposed as a solution for the bandwidth bottleneck at the Access Networks, mainly due to the characteristics of the fibers. A failure in the network causes a large quantity of information losses. By adopting a ring topology and optical switches we propose a novel protection mechanism for time division multiplexed passive optical network (TDM-PON) that provides resilience against multiple network fails without equipment duplication. Two types of rings with one and two fibers are considered.

Multi-pump discrete Raman amplifier for CWDM system in the O-band

We demonstrate theoretically that discrete Raman amplifiers operating in the O-band region (1260-1360 nm) are more efficient than in any other band if we consider the fiber attenuation. Compared with the C-band (1530-1565 nm), the net gain is 3 dB higher. We present also theoretically two types of discrete Raman amplifiers which can be used in the O-band with a course wavelength division multiplexing system. The first amplifier has a bandwidth of 70 nm that was designed with four pump lasers operating at 12XY nm. The second one has a bandwidth of 100 nm and needed six pump lasers to obtain a flattened gain across the O-band. In addition, we have analyzed the gain saturation in both optical amplifiers.

Combining Marr and Canny operators to detect edges

We demonstrated that a single kernel analog self-electro-optic effect device with five input detectors find edges in an image. To avoid the post-processing to suppress false edges we propose a novel edge detector operator that combines Canny and Marr operators.

58 kHz ultra-low repetition rate ultralong Erbium-doped fiber laser mode-locked by carbon nanotubes

In this paper we present a 58 kHz fundamental repetition rate 3.5 km long EDFL mode-locked by SWCNT saturable absorbers. Because laser nonlinearities and accumulated dispersion, we observed chirped soliton-like 6.79 ps pulses with 0.49 nm spectral width. This is the lowest repetition rate in EDFL, to the best of our knowledge.

Micromechanical exfoliation of two-dimensional materials by a polymeric stamp

In this work, an alternative technique to the traditional micromechanical exfoliation of two-dimensional materials is proposed, consisting of isolated flakes of graphite and molybdenum disulphide onto polymeric surfaces films. The set made up of polymer and flakes is fabricated by using a hot-press machine called polymeric stamp. The polymeric stamp was used to allocate flakes and also to allow the exfoliation process to take place just in one face of isolated flake. Optical microscopy, Raman spectroscopy and photoluminescence spectroscopy results showed that multilayers, bilayers and single layers of graphene and MoS2 were obtained by using a polymeric stamp as tool for micromechanical exfoliation. These crystals were more easily found because the exfoliation process concentrates them in well-defined locations. The results prove the effectiveness of the method by embedding two-dimensional materials into polymers to fabricate fewer layers crystals in a fast, economic and clean way.

An Electrooptic Multiple-Quantum-Well Device for Image Processing

We investigated the use of an analog self-electrooptic effect device based on GaAs multiple quantum wells as an image processor chip to early vision processes. We focused our attention at the edge detection process using layouts of photodetectors to extract Laplacians of images. Laplacians of linear, constant, step, and Gaussian intensity profiles agree with the expected values. These results show that the device works properly as an edge detector.

Thin films incorporating carbon nanotubes used as saturable absorbers to passively mode-lock Erbium-doped fiber lasers

We present a new method to fabricate thin films using single-walled carbon nanotubes and a urethane-based transparent polymer. We construct an Erbium-doped fiber laser to test our films as saturable absorbers to passive mode-lock them. As results, pulse-trains were achieved and we carry on an optimization study about the relation involving cavity length, total cavity dispersion, absorption strength of thin films incorporating SWCNT and laser bandwidth to produce higher bandwidths in passive mode-locking regime.

Erbium-doped fiber laser passively mode-locked by thin films incorporating carbon nanotubes

We fabricate thin films incorporating single-walled carbon nanotubes by a simple method and construct an Erbium-doped fiber laser to test our saturable absorbers to passive mode-lock them. We present a study about total cavity dispersion in mode-locked regime to produce higher bandwidths.

O-band passive mode-locked Raman fiber laser based on Single Wall Carbon Nanotubes as saturable absorbers

We present a passive mode-locked Raman laser incorporating SWCNT (Single-Wall Carbon Nanotubes) as saturable absorbers operating in O-band. We construct two single mode fiber lasers to generate ultrashort pulses near zero dispersion wavelength fiber. As results, pulse-trains were achieved in two different regimes and we compared the output bandwidth, rate repetition and pulse durations from both lasers. With high accumulated dispersion, nanoseconds square duration pulses were generated from laser cavity. So we study the pulse duration behavior introducing a dispersion shifted fiber (DSF) inside the cavity and verified a strong relation between pulse shortening and DSF length.

Image Kernel Implementation by Spatial Arrangement of Multiple Quantum Well Diodes

We report the operation of the image processor based on spatial arrangement of quantum well diodes at reduced incident power and bias voltage. Linear relation between the optimum electrical biasing for a given incident power of an electro‐absorptive modulator is presented that is used to convert the electrical filtered image to optical one.