Fault analysis: optical performance investigation of fiber connections with imperfect physical contact.
We investigated the insertion and return losses of optical fiber connections with various air-filled gaps. Such gaps might occur when a fiber connection using physical contact unexpectedly fails, resulting in imperfect physical contact. The optical performance of these fiber connections depends on wavelength and gap size. We revealed that the measured optical performance of fiber connections with an imperfect physical contact, i.e., with an air-filled gap, might deteriorate to ~18 dB for insertion loss and 9.4 dB for return loss at worst.
A pressure-sensitive fiber optic connector for loss analysis of physical contact
Abstract We design and fabricate a physical contact (PC) type pressure-sensitive fiber optic connector (FOC), which can be used to measure the contact force and analyze the contact loss caused by the contact force between two PC type FOCs. A fiber Bragg grating (FBG) is wrote on the fiber tip of the connector. The relationship between the Bragg wavelength of the FBG and the contact force exerted on the connector head is got by experiment with a stress sensitivity of 5.4 pm/N. We use this pressure-sensitive FOC for loss analysis of PC type FOCs. The relationships between contact force and insertion loss (IL) of three PC type FOCs have been got experimentally. Finally, finite element simulation results demonstrate the effectiveness of the system.
rPET detectors design and data processing
Small animal PET systems based on rotating planar detectors posses some interesting advantages for high sensitivity, high resolution imaging. We have designed the rPET detectors based on MLS crystals assembled on a 30times30 matrix optically coupled to a flat-panel PS-PMT. Weighted position readout circuits pre-process the 64 signals from the 8times8 anodes matrix, which are digitized using a charge-integrating converter. The amplification electronics, including the trigger output for coincidence detection, and the high voltage supply are integrated in a three PCBs stack that forms the base attached to the back of the PMT. The whole assembly is enclosed in a light tight, lead (Pb) shielded aluminum box. The detectors are mounted on a rotating gantry with more than 180 degrees rotation span. The digitized events are screened and histogramed, and a modified center of gravity algorithm removes from the position calculation those signals with poor signal to noise ratio. Apparent mean crystal size on the 511 keV field-flood images is 0.6 mm, mean peak-to-valley ratio is better than 8, and intrinsic resolution is 1.5 mm at the central row, with the energy window wide open. Sensitivity (CPS) for a pair of these detectors set in coincidence at 160 mm distance is 1%