High gamma smartphones based on Android operating system support the development of third-party applications. This kind of devices include subsystems such as sensors and actuators which can be used for diverse purposes. One example is the implementation of short range visible light communication (VLC) channels where the built-in light-emitting diode (LED) is the transmitter, and the complementary metal-oxide semiconductor (CMOS) camera works as the receiver. A major challenge for this communication channel is the modulation bandwidth of the light source which is limited to a few MHz, and the availability of a line-of-sight. The camera shutter is limited to a few frames per second (30 or 60 fps) for a few bits per second transmission, but the Rolling Shutter effect could allow the enhancement of the bit rate. In this work, we propose a VLC protocol design for the use of the built-in camera and the flash LED in order to implement a short range VLC channel, for high gamma mobile-to-mobile devices based on Android. The design is based on On-Off Keying (OOK) modulation for initially transmitting a few bits. Based on the rolling shutter effect in the CMOS image sensor, bright and dark fringes can be observed within each received frame, and the data can then be retrieved. Furthermore, two thresholding schemes for high fluctuation and large extinction ratio (ER) variations in each frame, are explored. Full protocol design and short range (5 cm), >100 kbits/s, VLC demonstration and image processing results will be included in the presentation.
Different types of mechanical and digital devices for measuring the velocity of fluids such as rotameters, annubar tubes, orifice plates, are suitable options. A limitation of such devices is that the direct interaction with the flux causes unwanted perturbations affecting their results. In this work, the design of a 540nm pulsed fiber laser system for measuring the velocity of water as a fluid via the Particle Image Velocimetry (PIV) technique is proposed. In particle image velocimetry, the fluid motion is made visible by adding small tracer particles and from the position of these particles, at two instances of time, it is possible to determine the flow velocity. The proposed, made in-house, noncommercial PIV system consists of: a second harmonic generation Q-switched Yb-doped fiber laser emitting 540nm pulses, a CCD camera, a pair of cylindrical diverging lenses, reference beads, and the fluid under test. The Yb3+-doped fiber laser itself is capable of producing 540nm, 5 – 15ns, 400mJ pulses at 500Hz – 15kHz repetition rates, suitable for PIV flow field studies. Full fiber laser design, in-house PIV system integration and flow field measurement results will be included in the presentation.
The development of novel Al-, Ge- doped and un-doped standard single mode fibers for future optical communication at 2μm requires the integration of, among other pieces of equipment, an optical time domain reflectometry (OTDR) technique for precise spectral attenuation characterization, including the well-known cut-back method. The integration of a state of the art OTDR at 2μm could provide valuable attenuation information from the aforementioned novel fibers. The proposed setup consists of a 1.7 mW, 1960nm pump source, a 30 dB gain Thulium doped fibre amplifier at 2μm, an 0.8mm focal length lens with a 0.5 NA, a 30 MHz acusto-optic modulator, a 3.1 focal length lens with a 0.68NA, an optical circulator at 2μm, an InGaAs photodetector for 1.2 nm-2.6 nm range, a voltage amplifier and an oscilloscope. The propagated pulse rate is 50 KHz, with 500 ns, 200 ns, 100 ns and 50 ns pulse widths. Attenuation versus novel fibers types for lengths ranging from 400- to 1000- meter samples were obtained using the proposed setup.