Technology at work

Video: 100-krad/s Endless Polarization Tracking with Miniaturized Module Card (related to the publication Electronics Letters, Vol. 47, No. 14, 2011, pp. 813-814 and the feature article in the same issue)

Poincaré sphere displays captured before polarization beam splitter during 100 to 100000 rad/s polarization tracking (July 2011)

An unmodulated laser signal was passed through an electrooptic endless polarization scrambler Novoptel EPS1000, followed by an endless polarization controller Novoptel EPC1000-100 (configuration EPC1000-??-?-1-?-??-O). The signal before the polarization beam splitter was tapped and monitored with an Agilent 8509B polarimeter. The pictures show accumulated polarization states measured over 10 min each at approximately 100 rad/s to 100 krad/s maximum scrambling speed. The polarization states (red) are nicely confined.

Video (english): 40-krad/s Polarization Tracking in 200-Gb/s PDM-RZ-DQPSK Transmission over 430 km (reported in IEEE Photonics Technology Letters, 22 February 2010, DOI 10.1109/LPT.2010.2043252)

Video: Early mechanical 12-krad/s endless polarization scrambling machine. Our polarization controllers easily track this scenario (reported in Electron. Lett., Vol. 44, Issue 23, Nov. 6, 2008, pp. 1376 – 1378) even though the bulk-optic rotating halfwave plate exhibits a position-dependent loss of several dB.

When you watch this video don’t forget to switch on the audio. This machine serves to introduce fast endless polarization changes. A rotating bulk-optic halfwave plate (bottom left, between collimators) is placed amidst 3 + 4 rotating fiberoptic quarterwave plates (right), which rotate at different, incommensurate speeds. The halfwave plate rotates at 1.2 times the speed of the electromotor (green). The motor speed is continuously increased from an initial standstill until it reaches 402 Hz. With each physical halfwave plate rotation corresponding to up to 8π rad on the Poincaré sphere, the achieved halfwave plate rotation speed of 482 Hz (28920 turns per minute) corresponds to a polarization change speed of 12 krad/s. Due to the large halfwave plate rotation speed the trajectories are mainly circles of all orientations and radii, especially difficult-to-track great circles. For results see Poincaré sphere displays below.

Poincaré sphere displays captured before polarization beam splitter during 100, 10000, 20000 and 40000 rad/s polarization tracking (July 2010)

An unmodulated laser signal was passed through a mechanical endless polarization scrambling machine (see video one section above), followed by an endless polarization controller (configuration EPC1000-??-?-1-?-??-O). The signal before the polarization beam splitter was tapped and monitored with an Agilent 8509B polarimeter. The pictures show accumulated polarization states measured over 10 min at approximately 100 rad/s (scrambling by quarterwave plates only), 10 krad/s, 20 krad/s and 40 krad/s maximum scrambling speed. The polarization states (red) are nicely confined, even though control speed and quality were reduced by the fact that the mechanical rotating halfwave plate introduces several dB of position-dependent loss.