Jahresbericht 2005 - IPHT Jena

46
comprising a semiconductor laser and an extended
external cavity. On the one hand, the FGL concept
for Non-Return-to-Zero (NRZ) data transmission
is considered as a potential low-cost data
transmitter device; on the other hand, the laser
output power and emission wavelength is shown
to be sensitive to packaging, laser temperature
and device current (see IPHT annual report
2001).
FGL understanding and optimization require simulation
tools, which have been developed at the
IPHT. The numerical method bases on the travelling
wave model for DFB (distributed feedback)
semiconductor lasers. As the lasing condition of
the external cavity laser depends on its own history,
the applied model splits the laser into individual
sections, each with its own treatment of
rate equations, (Bragg) reflections and losses.
The simulation tools give access to the complex
output power behaviour, mode jumps and eye.
Additionally it is now possible to design special
laser architectures like mode-hop-free FGLs with
active wavelength stabilization and wavelengthswitchable
FGLs, which are based on the interaction
between the external cavity with superimposed
Bragg gratings and the internal cavity,
which comprises the semiconductor optical
amplifier section.
Fig. 2.15: Simulated eye diagrams of the virtual
fibre-grating-laser at 2.5 Gbit/s. Shown are the
eye diagrams with the emission wavelength at the
Bragg wavelength (top) and at the long-wavelength
slope close to a mode-hop (bottom).
OPTIK / OPTICS
2.2.10 Implementation of an OADM with a
data rate of 10 Gbit/s as technology
demonstrator in the PLATON project
(Planar Technology for Optical Networks)
(M. Rothhardt, C. Aichele, M. Becker,
U. Hübner)
The EU-funded PLATON Project involves collaboration
and permanent feedback with a variety of
European research partners: Université des Sciences
et Technologies de Lille (France), Université
Paris Sud (France), Ecole Polytechnique Fédérale
de Lausanne (Switzerland), Technische Universität
Hamburg Harburg (Germany), Instituto de
Engenharia de Sistemas e Computadores do
Porto (Portugal), and two industrial partners,
Lucent Technologies GmbH (Nürnberg, Germany)
and Highwave Optical Technologies (France).
The objective of the PLATON project was to
study, develop and assess photosensitive planar
technology through key pilot devices. The main
subject of interest is demonstrating the feasibility
of the technology for making components like
channel waveguides, multimode interferometers,
Mach-Zehnder structures and Bragg gratings.
The work aims at a reconfigurable optical adddrop
multiplexer (OADM) which will be the final
demonstrator.
Objectives of the IPHT were particularly:
(i) Accomplishing an optimized process for optical
layer deposition
(ii) Structuring the optical waveguides of the key
pilot components (OADM)
(iii) Realizing the Bragg gratings inside the optical
waveguides
(iv) UV trimming of the MZI structures (Mach
Zehnder Interferometer) of the OADM’s
(v) Packaging and fibre coupling of the optical
chips.
Fig. 2.16: OADM scheme with MZI structure, sections
for UV trimming, input and output ports and
Bragg grating regions.
The main results are:
(i) Optical layer deposition
The well-mastered technology at the IPHT for
optical silica layer deposition, FHD (Flame Hydrolysis
Deposition) is applied for this project. The
core layer is germanium-doped. Our parameters
achieved are:
Core layer thickness of 4.5 µm/5.2 µm and a
refractive index of n[core] = 1.469. The refractive
index tolerance is δn