In order to asses free space optical links, using a Cassegrain telescope, for both classical (i.e. coherent and direct
detection) and quantum (coherent, Dolinar-Kennedy system) several scenarios were analyzed. This analysis was
conducted through a software tool that uses some specific parameters imposed by the environmental condition and
hardware used, such as: pointing and tracking errors, turbulence, modulations schemes, and visibility, among others; in
order to obtain the general performance parameters of the simulated link, such as: bit error rate and the photons number.
The software developed allows the user to produce useful way to assess the possible success of the implementation of
the free space optical link, or a way to identify phenomena that might suggest hardware adjustments to improve the
overall performance of the system. Results allow the revision of the expected link performance for a quantum key
distribution system; although it is possible to use it for general optical quantum communications systems.
We describe a homodyne optical Costas loop receiver intended to detect weak coherent states with diffused phase and suppressed carrier phase modulation. In order to get the information contained in the quadrature components of the optical field, we implement an 8-port receiver operating at 1550 nm, based on the manipulation of the state of polarization of both the local oscillator and the data signal. Employing binary phase-shift keying, we make measurements in the time and frequency domain of the quantum noise and bit error rate using an optimum loop filter, and compare the performance of our receiver against the standard quantum limit for the simultaneous quadrature detection, considering both ideal conditions and the overall efficiency of our set up.
We present a low-cost kit to support optical communications courses teaching. The kit contains a students manual that can be used to explore the basic phenomena involving optical transmission and reception phenomena, a transmitter module, and a receiver module.
It is presented an educational kit to show physical principles: momentum, free fall and measure of gravitational constant
for an object in movement. These principles are reproduced using mechanical parts, optical sensors and laser to send a
signal into a computer. Data results are acquired and analyzed to demonstrate that the results are concordant with the
theory. The results are into a 10% of error far of the known values for gravitational constant on Earth.
This educational and demonstrative kit can be use in elementary and undergraduate level; it has as proposes to be a base
to show complex experiments and advanced theory.