Abstract
This paper presents the TEC4SEA research infrastructure created in Portugal to support research, development, and validation of marine technologies. It is a multidisciplinary open platform, capable of supporting research, development, and test of marine robotics, telecommunications, and sensing technologies for monitoring and operating in the ocean environment. Due to the installed research facilities and its privileged geographic location, it allows fast access to deep sea, and can support multidisciplinary research, enabling full validation and evaluation of technological solutions designed for the ocean environment. It is a vertically integrated infrastructure, in the sense that it possesses a set of skills and resources which range from pure conceptual research to field deployment missions, with strong industrial and logistic capacities in the middle tier of prototype production. TEC4SEA is open to the entire scientific and enterprise community, with a free access policy for researchers affiliated with the research units that ensure its maintenance and sustainability. The paper describes the infrastructure in detail, and discusses associated research programs, providing a strategic vision for deep sea research initiatives, within the context of both the Portuguese National Ocean Strategy and European Strategy frameworks.

Abstract
The back propagation algorithm is one of the best methods known for simultaneous linear and nonlinear impairment mitigation in long-haul fibre-optic links. Better understanding the full potential of such algorithm is key to improve the capacity of future links, whose design is likely to depend on the algorithm performance under different link configurations. In this paper, we carry out a novel and pertinent comparison in terms of the computational complexity requirements of both symmetric and asymmetric back-propagation implementation approaches for different dispersion map configurations, using simple single channel transmission, which results in the proposal of several design rules for the optimized deployment of ultra-long haul optical transport systems. In particular, it is concluded that dispersion unmanaged transmission is preferable in the sense of compatibility with different link design configurations as well as computational complexity requirements and maximum performance that can be achieved.

Abstract
The usage of Autonomous Underwater Vehicles (AUVs), Remotely Operated Vehicles (ROVs), and sensors in surveillance, maintenance and inspection of underwater facilities is increasing the need for broadband, cost-e ective communications solutions. Current solutions, mainly based on acoustic communications, enable long ranges but provide low bitrates and have high communication delays. Despite its strong attenuation underwater, RF is envisioned as a technology to enable broadband, short-range communications. We present an ns-3 and an experimental evaluation of IEEE 802.11 networks in freshwater at 700 MHz, 2.4 GHz and 5 GHz frequency bands. Evaluation results con rm the accuracy of the new developed ns-3 underwater RF propagation model and show that IEEE 802.11 networks are feasible for broadband, short range underwater communications, with range and throughput exceeding 2 m and 100 Mbit/s, respectively.

Abstract
Pico-cell based access networks are increasingly seen as a promising solution for the growing mobility and bandwidth user demands. A recently developed resonant tunneling diode oscillator integrated with a photodetector and a laser diode (RTD-PD-LD), is being considered as a viable low cost pico-cell solution for radio-over-fiber based distributed antenna systems. In this paper we experimentally evaluate both the uplink and downlink error vector magnitude performance of the RTD-PD-LD for different phase and frequency modulation formats. We conclude that frequency modulated formats achieve better performance in both uplink and downlink configurations, yet, Gaussian Minimum Shift Keying format also appears to be a practical alternative.

Abstract
This work presents a new topology for the matching networks of an underwater wireless power transfer system. A class-D driver is used in resonance at fundamental and third harmonic frequencies. The double resonance helps reducing the reverse voltage stress at the diode rectifier. We present the analytical derivation of the proposed network and demonstrate the design procedure with an example. We also show that additional degrees of freedom can be acquired with the proposed topology, which improves the design space for time-varying operation conditions of our application, such as the load changing when a battery is being recharged. The performance of our topology is compared to most conventional approaches, such as the series-series and series-parallel networks, revealing a good compromise between power delivery and efficiency across a wide load range.

Abstract
In this paper, we investigate the optical modulation characteristics of a resonant tunnelling diode (RTD) oscillator. This preliminary work on the first RTD-PD oscillators with an optical window available from the iBROW project demonstrate that this device can effectively be used to accomplish amplitude and frequency modulation with light injection.