Abstract: Unwanted signal components in time-division multiplexed (TDM) systems may lead to crosstalk and noise if these pulses overlap with signal pulses from an interrogated sensor. The crosstalk and noise are dominated by interference between the signal pulses from the interrogated sensor and the unwanted signal components and can be greatly reduced by suppressing this interference signal. The unwanted signal components may include overlapping pulses originating from different sets of interrogation pulses (repetition periods). Modulating the phase or frequency between the repetition periods so that the unwanted interference signal does not appear at frequencies from which the phase of the interrogated sensor is demodulated suppresses this interference. Other unwanted signal components include leakage light during dark periods of the duty cycle of an interrogation signal.

Abstract: A fluid dynamic bearing cartridge includes a shaft or sleeve adapted to be fixed in place has at least one fluid dynamic bearing supporting the shaft and one or more seals at either end of the shaft. The seal arrangements may include a pair of centrifugal capillary seals at either end of the shaft. Alternatively, a grooved pumping seal or centrifugal capillary seal at one end may be used in combination with a static capillary seal, especially where a journal bearing defined along the shaft near the capillary seal has an imbalanced groove section.

Abstract: A system for controlling fluid flow from multiple isolated producing zones in a well is provided. Components of the system are placeable in and retrievable from bottom entry side pocket mandrel sections permanently installed in a production tubing string in the well. These components include retrievable isolation valve modules. Control signals for modules are developed either downhole or at the surface and modules may be placed or retrieved through the production tubing without pulling the production tubing from the well. In high flow rate applications the sliding sleeve flow control valve of the present invention provides a variable aperture valve having a fully open cross sectional area equal to that of the production tubing, thereby achieving a minimal pressure drop across the valve.