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HIPERON-T - High Performance Optical Network Transceiver for stratospheric data highways

Introduction

Figure 1.1: HIPERON-T application’s scenarios

Free space optical (FSO) communications are a promising alternative for bandwidth hungry applications. FSO applications include bridges between base stations of a cellular network, integration of multi-site networks and as a high speed/capacity back up alternative link for sudden and unexpected events. Moreover, FSO systems offer a tap-free communication channel, a rapid deployment with no need for costly interventions and a license free spectrum. Figure 1.1 shows potential deployment scenarios.

The HIPERON-T is a 10Gbps free space optical (FSO) media converter specially designed to provide a backhaul bridge between two networks by means of FSO communication links. The device can be easily deployed to bridge two different sections of the same Wide Area Network (LAN) or two separate WANs without requiring a wired solution. Moreover, the versatility of this transceiver allows the easy integration of ad-hoc networks that can be used for fast reaction to sudden events.

Motivation

Figure 2.1: Effects of the Index of Refraction Turbulence (IRT)

FSO communication links are subject to the effects of the atmosphere. In particular, the always changing nature of this transmission channel results in the presence of strong and sudden optical power variations at the receiver side. This phenomenon, known as fade, may lead to burst errors in the incoming data sequence and even to the complete outages of the channel. Fades are caused by the interaction of the propagating optical beam and the particles that compose the atmosphere. The dynamics of this phenomenon are usually modelled in terms of the Index of refraction Turbulence (IRT) which functions as a modelling metric to characterize and categorize different channel scenarios. Figure 2.1 exemplifies graphically the effects of the IRT upon a signal transmitted through the atmosphere.

Figure 2.2: Fades on the electrical signal at the receiver side of a FSO communication link

Figure 2.2 shows the resulting electrical signal at the receiver side of a FSO communication system. As seen, the signal presents deep fades and outages that hinder the transmission capabilities of the system. In order to cope with these spurious effects the LET integrates well known and wide spread Forward Error Correction schemes with novel transport and physical layer protocol solutions. 

HIPERON-T Project Specification

Overall Goal

To design, implement and validate a backhaul 10GbE High Performance Optical Network Transceiver (HIPERON-T) for stratospherical data highways

Main Objectives

1. To design and implement a Physical Layer (PHY) and a Data Link Layer for FSO applications.
2. To design effective and efficient error correction schemes (ECS) for FSO communication links.
3. To implement the required modules to guarantee compatibility with the 802.3 Ethernet Standard.
4. To adapt and develop the aforementioned systems to be integrated into an embedded hardware platform.

Targeted performance and features

The different set up requirements for the system and its deployment scenarios impose the following desired features upon HIPERION-T:

1. To be able to establish FSO communication at different data rates, specifically targeting 10Gbps, 1Gbps, 100Mbps and 10Mbps.
2. To be able to establish FSO full duplex communication with the possibility of configuring different data rates for each link, e.g. transmitting at 1Gbps while receiving at 10Gbps.
3. To guarantee a constant delay independently of the data rate of operation.
4. To comply with the FSO transmitter and receiver allowing its integration while maintaining its communication capabilities.
5. To guarantee the integrity of the data by means of error correction schemes specially devised to increase the tolerance to noise and power variance as well as to compensate link-outages with duration of several milliseconds.
6. To recover synchronization based on the alignment and acquisition of specific tracking sequences specially designed for this purpose. The system should also be robust in the presence of jitter.

Duration

January 2015 - December 2016