565 Mbit/s optical PSK transmission system with endless polarisation control

Neural networks as a tool for recognition of partial discharges

“…In these formulas, [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] is the electrooptical constant [14], no is the ordinary refractive index of LiNbO3 (= 2.2125 for X = 1523 nm), E,, and E,, represent the x-and y-components of the external electrical field strength, respectively, caused by the voltage differences between the electrodes while w and c are the frequency and velocity of light in vacuum. Since the two waves propagate with different phase velocities, they show a phase retardation r at the output of the waveguide which is described by:…”

“…Since the state of polarization (henceforth referred to as SOP) of the transported signal fluctuates as a result of changes in the temperature, stress and humidity of the fiber, a fading of the output electrical signal occurs. Several techniques to overcome this problem are known: polarization diversity, data-induced polarization switching, polarization scrambling, use of polarization maintaining fibers and use of a polarization controller [3]- [7]. From these techniques the one using a polarization controller yields the best receiver sensitivity.…”

“…From these techniques the one using a polarization controller yields the best receiver sensitivity. Until now mechanical polarization controllers have been realized, using electrical fiber squeezers, fiber cranks which can be rotated or polarization preserving fibers wound around piezo-electrical cylinders [7]- [9]. To keep receivers small, reliable and operating at low voltages (< 100 V), however, an integrated broad-band optical polarization controller on a lithium niobate (LiNb03) substrate [lo], [11] is the most likely candidate for future production.…”