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.