Optics express
-
We have proposed and experimentally demonstrated a 60-GHz bidirectional radio-over-fiber system with downstream orthogonal frequency division multiplexing address (OFDMA) and wavelength reuse upstream single-carrier frequency division multiple address (SC-FDMA). In the downstream, a 3-dB optical coupler is used for two-carrier injection-locking a distributed feedback (DFB) laser in order to realize the single-sideband modulation. ⋯ Transmission of 9.65-Gb/s 16-QAM downstream OFDMA on 60-GHz carrier and 5-Gb/s QPSK upstream SC-FDMA (2.5 Gb/s for each user) are both successfully demonstrated over 53-km standard single mode fiber without chromatic dispersion compensation. The crosstalk between the downstream OFDMA and the upstream SC-FDMA can be neglected.
-
We present the nodal aberration field response of Ritchey-Chrétien telescopes to a combination of optical component misalignments and astigmatic figure error on the primary mirror. It is shown that both astigmatic figure error and secondary mirror misalignments lead to binodal astigmatism, but that each type has unique, characteristic locations for the astigmatic nodes. ⋯ For the case of secondary mirror misalignments, one of the astigmatic nodes remains nearly at the field center (in a coma compensated state) as presented in Optics Express 18, 5282-5288 (2010), while the second astigmatic node moves away from the field center. This distinction leads directly to alignment methods that preserve the dynamic range of the active wavefront compensation component.