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Photosensitive technology for optical systems


PHOTOS seeks to exploit the new and significant technology represented by fibre grating components, written directly into photosensitive optical fibres by UV exposure, to achieve practical and advanced functionalities in WDM and TDM systems.

Fibre grating filter UV-writing

The main objective is to develop key fibre components for future photonic networks which can be advantageously realised with photosensitive grating technology, to assess their system performances by supplying them for test to a set of system-oriented ACTS projects, and to analyse the network impact of this technology.

Identified devices are single- and multi-wavelength band-pass filters, optimised amplifiers and gain flattening filters, single frequency fibre lasers, optical add-drop multiplexers, tuneable filters, and single- and multi-wavelength chromatic dispersion compensators.
The basic material studies have provided new insights into the fundamental mechanisms, including stability, and important data for device design and implementation. Several fibre types have been realised and supplied for DFB fibre laser, bandpass filter, and OADM realisation. Grating characterisation has been addressed with the development of fast OLCR technique, and tunability issues have been assessed.
Significant results have been obtained on all classes of devices: bandpass filters with rejection over the whole erbium amplifier band; DFB fibre laser providing 6 mW output power in single polarisation state; grating for flattened and stabilised amplifier demonstrating a reduction of the gain excursion from 15 dB to 3-4 dB over 1538 nm-1562 nm band; new OADM structure with grating in coupling region with demonstration of 18 dB rejection in back reflection and 17 dB grating strength; chromatic dispersion compensator with development of new methods to write long, chirped and apodised grating and realisation of multi-? as well as long (1.3 m) wideband (10 nm) 1300 ps/nm compensator, which represents an outstanding advance in this field. Packaging work was also carried out on devices, supported by climatic tests, with analysis and derivation of related temperature compensation schemes. For the passive scheme, considerable development of the adhesive system, and the exact design of these packages, has now produced temperature sensitivity reduced to around 0.2nm/100 C. It has also been shown that an active stabilisation technique can provide a uniform control of larger structures, such as long chromatic dispersion compensators.
Initial functional system characterisation has provided first levels of assessment and feedback to designers on device performance: evaluation of bandpass filters concentrating on assessing the required rejection levels; evaluation of the DFB fibre laser with 10 Gb/s external modulation with transmission system performance as good as that of semiconductor DFB laser; assessment of the grating constraints for OADM at 2.5 Gb/s using grating/circulators or Mach-Zehnder configuration and demonstration of excellent performance, including cascade connection in a loop; tests on chromatic dispersion compensators including that on a multiplex of 11 WDM 10 Gb/s channels using wideband compensator, demonstrating a bit error rate <10-9 on all channels after 100 km transmission on standard fibre. System modelling work has provided a useful tool for device optimisation; particular benefit has been derived in grating apodisation for chromatic dispersion compensator design.
Overall expected results of the project are the:
Establishment of a clear understanding of the basic mechanisms of photosensitivity; development of improved fibres for devices realisation; optimisation of processes for practical device realisation; assessment of stability.
Assessment of wavelength tunability.
Design, realisation and packaging of key devices, optimised with respect to systems specifications established in collaboration with a set of system-driven ACTS projects.
Modelling of system behaviour based on devices properties and related analysis.
Devices laboratory functional system characterisation.
Supply of devices to other ACTS projects for system tests.
Exploitation of system tests results in order to analyse the impact of this technology on photonics networks.
Expected Impact
The project, through the optimisation and assessment of photosensitive technology with respect to system needs, will set this technology in place in Europe for the development of future photonics networks.

Main contributions to the programme objectives:
Main deliverables
Grating technologies for a DWDM high bitrate broadband optical network
Contribution to the programme
Important technology elements for the future European photonic network
Technical Approach
The work is organised in three workpackages:
'Material studies, optimisation and supply' embraces the material studies required to understand and master photosensitivity as well as development of improved materials and processing techniques to supply optical fibres for components implementation. Issues regarding grating stability and spectral tunability are also addressed;
'Devices implementation' is concerned with the design, fabrication and packaging of identified key fibre devices that are optimised with respect to systems requirements;
'System oriented characterisation' concerns definition of device specifications, in collaboration with those system-driven ACTS projects that will further test these devices, modelling of their system characteristics, functional characterisation of devices in laboratory tests and the analysis of their impact on future networks.
Summary of Trial
Field trials will be realised through collaboration with system-driven ACTS projects.
Key Issues
Mastering of photosensitive technology;
Design, realisation and packaging of key devices;
Assessment of system characteristics for devices and analysis of the system impact.

Funding Scheme

CSC - Cost-sharing contracts


Alcatel Alsthom Recherche
Route De Nozay
91460 Marcoussis

Participants (8)

United Kingdom
Aston Triangle
United Kingdom
Centro Studi e Laboratori Telecomunicazioni SpA (CSELT)
Via Guglielmo Reiss Romoli 274
10148 Torino
Ecole Polytechnique Fédérale de Lausanne
Optoelectronics Research Centre
United Kingdom
Sirti SpA
Via G.b. Pirelli, 20
20124 Milano
Avenue Georges Clemenceau 15
Universite des Sciences et Technologies de Lille