Abstract
The options to implement a coherent optical system employing a phase estimation algorithm combined with adaptive linear equalization are investigated. Several carrier phase estimator strategies are discussed, in terms of parallelization, performance and implementation complexity.

Abstract
The electrical compensation of chromatic dispersion (CD) and polarization mode dispersion (PMD) in a coherent optical system exploiting polarization multiplexing is discussed in this paper. The benefits of combining a phase estimation algorithm with a decision directed least-mean-square equalizer in a feedback configuration is reported.

Abstract
We show experimental results of clock recovery from return-to-zero (RZ) format data by using injection locking of a free-running optoelectronic oscillator (OEO) circuit, which consists of a resonant tunneling diode (RTD) oscillator integrated circuit with both a detector and optical source. Error free extraction of a clock signal from the RTD-OEO is shown under both optical and electrical injection. The clock recovery performance at similar to 1.25 Gb/s is analyzed in terms of timing jitter, phase noise and locking bandwidth.

Abstract
The digital equalization of fibre impairments in coherent optical communications allows for ultimate limits of spectral efficiency to be achieved, while reducing the cost and complexity compared to optical based solutions. Digital backpropagation (BP) was proposed recently as a reduced complexity approach for jointly compensating linear and non-linear impairments in single polarization coherent optical systems. Furthermore, polarization division multiplexed quadrature phase-shift keying (PDM-QPSK) has emerged as a promising format to increase spectral efficiency. Here we assess the performance of the simplified backpropagation equalization in both single channel and multiple channel transmission in combination with polarization multiplexing for different dispersion map configurations. It is shown that polarization multiplexing induces a degradation in performance due to cross-phase modulation polarization scattering, the backpropagation algorithm still overperforming linear equalization.

Abstract
The Daphne project has been addressing the adoption of an optical fiber infrastructure for future aircrafts. Beyond the obvious motivation of reduced weight and electromagnetic interference, the availability of a huge amount of bandwidth makes the optical fiber well suited to transport Radio Frequency (RF) signals transparently, while avoiding cumbersome dedicated RF cabling. An integrated optical network may be exploited to transport radio signals from diverse aircraft antennas ranging from satellite/earth communications, collision avoidance, GPS signals for positioning and attitude determination, weather/detection RADAR to corrosion sensors. Such network can also support passenger infotainment and mobile communication services, such as cellular GSM/UMTS/LTE, broadband Wi-Fi (IEEE 802.11) and Ultra-Wide-Band Wimedia/WiGig. Specifically, the optical fiber infrastructure may provide connectivity from external antennas (through remote nodes) to RF transceivers installed in the cockpit and avionics bay (head-end nodes); in the context of the present paper, the transmission of differential GPS signals used to provide aircraft attitude information will be discussed. The use of GPS for aircraft attitude determination has been under discussion for more than 20 years [1]. It consists in performing carrier-phase differential processing of measurements from GPS antennas affixed to the frame of the aircraft, which yields centimeter- or millimeter-level accuracies, provided that integer phase ambiguities are resolved [2]. The attitude algorithm consists in a highly accurate real time kinematic (RTK) technique, given the short baseline distance between antennas, in which the main antenna acts as a Base station and two auxiliary antennas as Rovers. In the present experiment, we used a setup consisting of two-antennas (Base and Rover), which is enough to evaluate the RTK performance. A particular aspect of concern stems from the fact that the transmission of optical signals through a complex optical fiber network is subject to the occurrence of reflections in the multitude of connectors spanning the path between a remote node and a head-end node. Therefore, we will focus our analysis on the performance impact of optical reflections affecting the power level stability of the optical source. © 2012 IEEE.

Abstract
The measured characteristics of a R-EAM, acting as a base station, were used to assess the performance of a radio-over-fiber uplink for possible provision of wireless services within aircrafts. The specific case of deployment of UWB signals was analyzed. We conclude that laser RIN is a performance degradation factor that imposes a limit on the achievable SNR, especially for a zero biased modulator. A laser RIN of -160 dB/Hz would be required in order to avoid the RIN limitation. Additionally, in this case the performance becomes limited by shot noise. Although the zero bias case seems limitative, the R-EAM can be optimum biased using a small battery, which can last for several months, allowing the base-station to operate as a passive device. © 2011 IEEE.