Yves Auffret

Quasi-all-optical network extension for submarine cabled observatories

Submarine cabled networks are designed to collect valuable data in geophysics, geochemistry, biology, or oceanography. Unfortunately, the development of such a network is expensive and needs complex subsea infrastructures. Once in place, a cabled network cannot be easily relocated. The current cost of cables and their installation are one of the major obstacles to these networks deployment. On the one hand, these cables are necessary to provide power supply and communication data, and on the other hand they drastically reduce the possibilities to extend the cabled observatory network in order to reach a closed area of significant interest. This is why, to address this issue, we propose a quasi-all-optical architecture to easily extend multidisciplinary cabled networks or to create a dedicated submarine hydrophone or seismometer network. This solution consists of using only a single fiber optic to transmit both the energy, required to supply the instrument, and the data, exchanged between the shore station or equivalent. In this paper, we present our proposed architecture, and we discuss its feasibility thanks to experimental results.

MIMO underwater acoustic channel characterization based on a remotely operated experimental platform

In the framework of the development of a MIMO (Multi-input Multi-output) capable underwater acoustic modem, this paper describes on the one hand a remotely operated experimental platform at sea in real conditions able to transmit and receive real-time multi-streams signals and the other hand an analysis of the experimental channel capacity gain brought by the MIMO approach with respect to traditional single transmitter system. The original remotely operated generation/acquisition system provides an extensive characterization of the MIMO underwater acoustic channel for various transmission ranges and sea states. The capacity analysis extracted from real conditions channel estimates confirm that MIMO approach in experimental scenario leads to a substantial capacity gain with respect to single transmitter even by taking account signal overhead. As foreseen by theory, the MIMO capacity gain is also shown to be dependent from transmission range and transducers arrays configuration.

Smart Sensor Metamodel for deep sea observatory

Deep sea observatories, based on sensor networks, provide new features to the ocean survey like a continuous observation of the ocean. The sensors used in these observatories provide environment data and also insure new functionalities or services due to the permanent running of this network. The nominal behavior of each sensor must be extended to feet with this concept of deep sea observatory. So in this paper, we present our smart sensor metamodeling approach for deep sea-observatory. This work aims at specifying a Domain Specific Language (DSL) dedicated to smart sensor networks in a goal to model the behavior of the sensor and to produce automaticaly the software which is embedded in the network infrastructure. This DSL includes three modeling levels of smart sensor: static properties, interface and behavior. The sensor interface provides to observers and scientific researchers a set of services dedicated to ocean measures that the sensor can do, based on internal or external event detections. The sensor behavior permits observers to know how the sensor behaves.

Open-Sea Observatories: A New Technology to Bring the Pulse of the Sea to Human Awareness

Historically, observation in Marine Science was mainly based on in situ measurements made mainly over ship surveys and shore measurements. Unfortunately, ship surveys can only be episodic, and are constrained by weather and by the constant rise of ship-time cost. As the data provided by non-communicating moorings are stored in the measurement system, a ship intervention is needed to recover both the mooring and the data after several acquisition months. Further to the rather successful mediumand short-term deployment of these traditional devices, scientists have expected the development of long-term observations and permanent marine system-monitoring tools so as to gain more insight into the observed processes. By providing additional information, satellite technology can partly solve this gap between the reality and expectations. However, even though satellite images provide information over a large time frame (from minutes to years) and a wide range of spatial resolutions (from metres to thousands of kilometres), they only cover the upper layer of the sea. An Open-Sea Observatory is a complementary tool that allows one to make, in the water column and on the seafloor, long-term measurements of many environmental parameters and to acquire them in real-time, or near real-time. In addition to this real-time data transmission, these systems permit remote intervention by humans when needed, and thus can be considered as 2-way communicating devices. Because of these two characteristics, observatories are innovative systems that bring internet to the ocean and make the ocean reality visible to the human eye. According to our definition of an Open-Sea observatory, other very useful observation tools such as gliders, floats, repeated profiler transects, etc. will not be considered in this chapter to only focus on such ocean observatories. Observatory initiatives have been spreading worldwide since the 1990s. In Europe, several initiatives started twenty years ago so as to upgrade free-fall systems from the sea surface (the so-called “landers”) to make them 2-way communicating and to develop bottom

Raman amplification in an optically high-powered data link dedicated to a 10 km long extension for submarine cabled observatories

We describe a quasi-all-optical extension dedicated to simplifying the deployment of submarine cabled observatories. Based on power-over-fiber technologies, high power supply and data are both transmitted in one optical fiber of a few kilometers in length. We study the Raman amplification on the down- and up-stream data in the static regime with the high optical power varying from 100 mW to 4 W over a 10 km long single-mode optical fiber. We focus on the data optical budget and signal to noise ratio dependence with respect to the high optical power value and the data optical wavelength. We also present the transmission quality in the dynamic regime of this quasi-all-optical extension.

On the analysis of orthogonal chirp division multiplexing for shallow water underwater acoustic communication

This paper describes the use of the novel Orthogonal Chirp Division Multiplex (OCDM) waveform for an end-to-end high data rate underwater acoustic transmission system. The described OCDM based transmission is evaluated over a realistic underwater acoustic (UWA) channel and compared fairly against the conventional orthogonal frequency division multiplex (OFDM). By efficiently exploiting multi-paths diversity of the channel, OCDM is shown to provide better robustness than OFDM especially in case of a underloaded configuration when only a subset of N chirp waveforms are modulated leading to an interesting trade-off between spectral efficiency and robustness against UWA channel impairments.

Scientific specifications, common and complementary developments for deep sea and coastal fixed point multidisciplinary cabled observatories

The developments of subsea observatories has been addressed by several national and European projects involving Ifremer engineering teams during the last decade. The motivation of scientific research disciplines has been growing during the same period. The coordination of ESONET Network of Excellence has been a unique occasion to analyse the best practices world wide and propose standards and recommendations. The merger of existing observatories and construction of new deep sea observatories in Europe is now organized at European level through EMSO (European Multidisciplinary Seafloor Observatory). Its preparatory phase is now building a multi-site large research infrastructure. The French participation is planned through the EMSO-France initiative. The need to monitor the sea environment is also acute in the coastal zone as Marine Protective Areas, indicators of marine biodiversity and ecological quality are requested by the marine strategy directives (such as European Marine Strategy Framework Directive). The cost effectiveness of the long term observatories will gain from a choice of common technologies and operating methods for coastal observatories and deep sea networks. Innovative solutions are proposed in the fields of: biofouling protection, sensor web enable interface, sensor registry, data management, material choice, energy requirements, junction box designs,… A review of these solutions is presented in the paper. Coastal cabled observatories such as MeDON are used as test benches for several of these new developments. Even in the cases when depth will induce different technologies, the deep sea cabled and shallow water cabled observatories may be designed in such a way that operating methods will be similar (components, subsea intervention methods, remote maintenance procedures, network management practices, sensor calibration procedures,…). Ifremer engineering teams are using the ongoing projects to enhance reliability in shallow as well as deep water cabled observatories.

Experimentation of MIMO underwater acoustic communication in shallow water channel

This paper describes an end-to-end underwater acoustic transmission system based on MIMO (multiple input multiple output) principle. The described transmission system is experimented over various sea conditions and compared against conventional SIMO (single input multiple output) mode operating with a single transmission stream and multiple receive sensors. By analyzing the optimal performance of the proposed decoder, we select a MIMO and SIMO mode achieving similar robustness against underwater acoustic channel and demonstrate over longterm experiment, that, as foreseen by theory, MIMO technology provide a data rate gain at a same robustness level.

Long-term subsea observatories: Comparison of architectures and solutions for infrastructure design, interfaces, materials, sensor protection and deployment operations

These subsea observatory infrastructures may have different architectures; the ESONET and EMSO (see www.esonet-emso.org) projects have identified five main types of observatories.

Coastal observatory as a development platform for marine instrumentation

Sea Test Base / Celadon is a non-profit organization, which offers testing facilities mainly based on a coastal non-cabled observatory, dedicated for designing, testing and qualifying marine sensors and marine instruments in real conditions. This platform can be considered as an experimental laboratory at sea, available 24/7/365 from the Internet. In a first step, we describe, analyse and compare the differences in terms of architecture and services between conventional marine cabled, non-cabled observatories and Sea Test Base facilities. In a second step, we present the results obtained with this platform to design, improve and qualify the hardware and the algorithms for a Multiple-Input and Multiple-Output (MIMO) modem for underwater acoustic communication. In conclusion, we present the upcoming extension of Sea Test Base, which consists of a shared open platform based on a mesh network including buoys and a pontoon, dedicated to underwater acoustic experiments at sea.