This article presents a novel technique to acquire and visualize two-dimensional images of dynamic changes of acoustic pressure in the case of a stationary acoustic wave. This method uses optical feedback interferometry sensing with a near-infrared laser diode. The stationary acoustic wave is generated using two piezoelectric transducers of 40 kHz facing each other, dynamic changes in acoustic pressure are measured in a 100 mm x 100 mm acoustic propagation field whose refractive index is variable along the optical path of the laser from the laser diode to a distant mirror and vice-versa. The image system records an image of 100 x 100 pixels of the acoustic pressure variation.
This paper presents an experimental technique for two-dimensional imaging of dynamic acoustic pressure changes that is applied to visualize a stationary acoustic wave. This technique uses the optical feedback interferometry sensing scheme with a near-infrared laser diode and a two-axis scanning system. The stationary acoustic wave is generated by using a 40 kHz piezoelectric transducer pointing toward a concave acoustic reflector. The acoustic pressure dynamic changes are measured due to its impact on the propagating medium refractive index, which variation is integrated along the laser optical path from the laser diode to a distant mirror and back. The imaging system records a 100×50 pixels image of the acoustic pressure in 66 min.
Current evolution in Datacoms and Gigabit Ethernet have made 850nm Vertical Cavity Surface Emitting Lasers
(VCSEL) the most important and promising emitter. Numerous different structures have been growth, to obtain best
current confinement and then to control the emitted light modal behavior. We have developed a small signal equivalent
electrical model of VCSEL including Bragg reflectors, active area, chip connection and noise behavior. Easy to
integrate with classical software for circuit studies, this model which is widely adaptable for different structures takes
into account the complete electrical environment of the chip. An experimental validation for RF modulation up to 10
GHz has been realized on oxide confined VCSEL, demonstrating that the model could be used to get realistic values
for the VCSEL intrinsic parameters.
Including Langevin noise sources into the rate equations and using the same electrical analogy, noise current and
voltage sources can be added to the model. It allows good prediction for the RIN function shape up to 10GHz for