PHOTOS: Photosensitive technology for optical systems

• Forschungsstelle: EU FRP
• Projektnummer: 95.0178
• Projekttitel Englisch: PHOTOS: Photosensitive technology for optical systems

Schlüsselwörter (Englisch)

Fiber gratings; fiber photosensitivity; low coherence reflectometry; WDM; chromatic dispersion compensation

Alternative Projektnummern (Englisch)

EU project number: AC046

Forschungsprogramme (Englisch)

EU-programme: 4. Frame Research Programme - 1.2 Communications technologies

Kurzbeschreibung (Englisch)

See abstract

Partner und Internationale Organisationen (Englisch)

Alcatel Suisse SA (CH), Swisscom (CH), EPFL-TCOM (CH), Alcatel France (F), British Telecom (GB), Univ. of Lille (F), Univ. of Paris Sud (F), ORC Southampton (GB), Aston Univ. (GB), Sirti

Abstract (Englisch)

The main objective of the ACTS project 'PHOtosensitive Technology for Optical Systems (PHOTOS)' was (1) to develop and characterize Bragg grating technology, (2) to build active and passive devices based on Bragg gratings, and (3), to assess their system performance by supplying them for tests to a set of system-oriented ACTS projects and to analyze the network impact of this technology for future photonic networks. EPFL contributed to all three workpackages of the project.
Based on our experience in Bragg grating fabrication and characterization using reflection and transmission (R&T), Optical Low Coherence Reflectometry (OLCR), and stress measurements we were able to contribute substantially to workpackage (WP) 1.1, 'Phenomenological Studies'. In 1998 R&T and stress measurements have been performed on highly photosensitive and hydrogen loaded standard Telecom fibers to evaluate H2-induced stress changes, and UV-induced index and stress changes. A significant irreversible reduction of axial tensile stress in the core of H2-loaded fibers has been observed. The reduction depends on the core dopants and the fiber drawing tension. Hydrogen loading increases the compressive stress, which is further increased by UV- irradiation. The stress measurements have been performed in collaboration with ALCATEL Switzerland. EPFL worked on the improvement of high-speed optical low-coherence reflectometer. To solve the problem of nonlinearity in the scan distance, the OLCR has been equipped with a DFB laser for optical scan path calibration using interference fringes. In addition, characteristics such as longitudinal scan speed, scan range, measurement repetition rate and sensitivity have been further evaluated experimentally and theoretically. First measurements of long period grating induced cladding modes during photoinscription have been performed using this high-speed reflectometer. The characterization technique has been developed in parallel. EPFL made OLCR measurements of gratings with various apodization profiles fabricated by different PHOTOS partners.
The objective of WP2 was to build active and passive devices based on photosensitive elements. Here, EPFL contributed to WP2.5 by developing a tunable filter device for wavelength routing. In 1998 a piezo-electrically driven tunable filter has been assembled. An apodized fiber grating from ASTON University has been integrated into this device. Reflection spectra were measured to determine tuning range and the 1, 3, and 20 dB bandwidth changes during tuning. A 30 nm tuning range without any changes in reflectivity or spectral shape of the grating has been obtained. Maximum tuning speeds of 21 nmlmsec and wavelength setting time below 1.5 msec have been measured. System tests of the tunable filter device have been performed at BRITISH TELECOM Laboratories.
The objective of WP3 was to deliver device specifications for the design and the fabrication of Bragg gratings and to analyze the network impact of these devices. The activity of EPFL-TCOM together with SWISSCOM in WP3.4 was focused on modeling chromatic dispersion compensating (CDC) gratings and evaluating their performance in systems. A harmonic ripple model has been used to evaluate the performance in one span transmission systems operated at 10 Gbit/s. A numerical tool to model multi-span systems with cascaded CDC devices has been developed. It was used to characterize various CDC devices developed within the project. Finally, a 12-links single-channel core network based on standard single-mode fibers has been planned for Swisscom emphasizing the influence of chromatic dispersion compensation at high bit rates in either linear or non-linear regimes.

Datenbankreferenzen (Englisch)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 95.0178