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Integrated Opto-electronics towards the Coherent Multichannel IBC

Objective

The primary objective of this project is to develop the advanced technology base from which low cost products could be produced to facilitate economic use of the transmission capacity available in optical fibre. It is assumed that a multiplicity of signals at up to 600 Mbit/s each would be carried on one fibre, initially using high density wavelength division multiplexing (HDWDM) with direct detection; and evolving, later, to optical frequency multiplexing with coherent detection. Low cost will be achieved through a high level of integration.
The primary objective of this project is to develop the advanced technology base from which low cost products could be produced to facilitate economic use of the transmission capacity available in optical fibre. Indium phosphide has been chosen as the material on which to base this work as it has the best known properties for ligh emission and detection in the 1200 nm to 1600 nm window of low absorption, low disperion silica fibre.
New components include multiquantum well-distributed bragg reflector (MQW-DFB) lasers with a spectral linewidth less than 0.5 MHz for 20 mW output power. New technological process for active-passive section integration has been established including reactive ion etching (RIE). A MQW ridge modular has been fabricated, with 5 GHz bandwidth and good large signal modulation characteristics at 2.4 Gbit gallium arsenide. DFB sources giving linewidths less than 3 MHz for output power from 1 mW to 18 mW have been built. Very low threshold (7.7 mA) IEC DBR (a world record) with 15 MHz minimum line width, has been achieved in a 400 micron long device.
Optical amplifier fabrication methods have been refined and several samples with different structure tested. Short term performance objectives have been exceeded. A wideband combiner network (insertion loss only 0.38 dB) in polarization maintaining fibre has been fabricated and spliced to 2 indium gallium arsenide pin - gallium arsenide integrated circuit (IC) (good balance) to form a hybrid polarization diversity receiver.
Modulators and 3dB couplers in double heterostructure waveguides on indium phosphide have been demonstrated with efficiency of 2 degree per Vmm. New waveguide structures, based on diluted multiquantum wells, have been demonstrated with coupling loss to single mode fibre less than 2dB.
Technical Approach

Indium phosphide has been chosen as the material on which to base this work as it has the best known properties for light emission and detection in the 1200 nm to 1600 nm window of low absorption, low dispersion silica fibre. The same material system can be used for high performance active and passive components such as FETs single-mode wave guides and branching devices, and polarisation modulators. The project aims towards integrating all these devices thus leading to a high level of functional integration. In addition the system requirements will be studied and laboratory devices will be evaluated both as components and as systems elements, in order to monitor progress and ensure that defined system requirements can be met.

Key Issues

- Increasing use of multiple optical frequency transmission.
- Optical frequency multiplexing (OFM) used to provide higher capacity overlay connections.
- Wavelength allocation, technological limitations.
- Evaluation of systems commensurate with traffic requirements.

Achievements

The work of the first four years has been reported in some 80 publications in the technical press and at conferences. The project has demonstrated world best characteristics for several components including HDWDM receivers, DBR lasers, precision DDFB lasers, fused fibre polarisation diversity networks and state of the art performance for most of the components tackled.

Continuous review of the world scene has guided the project. Key parameters of eleven system possibilities have been analysed and transmission experiments representing five of the front runners have been set up. Proposals have been made in relation to optical wavelength planning.

New components include MQW-DFB lasers with a spectral linewidth <0.5 MHz for 20 mW output power. New technological process for active-passive section integration have been established including RIE. A MQW ridge modular has been fabricated, with 5 GHz bandwidth and good large signal modulation characteristics at 2.4 Gbit/s. DFB sources giving linewidths < 3MHz for output power from 1 mW to 18 mW. Very low threshold (7.7 mA) IEC DBR (a world record) with 15 MHz minimum line-width, has been achieved in a 400 micron long device.

Optical amplifier fabrication methods have been refined and several samples with different structure tested. Short term performance objectives have been exceeded. A wideband combiner network (insertion loss only 0.38 dB) in polarisation maintaining fibre has been fabricated and spliced to two InGaAs pin - GaAs ICs (good balance) to form a hybrid polarisation diversity receiver.

Modulators and 3dB couplers in double hetero-structure wave-guides on InP have been demonstrated with efficiency of 2/V.mm. New waveguide structures, based on diluted multi-quantum wells, have been demonstrated with coupling loss to single mode fibre <2dB.

Low-capacitance (0.1 pF), waveguide - fed PIN diodes have been fabricated with 80% internal coupling efficiency. Four element arrays of pin-transimpedance preamplifiers (OEIC having component count of 88) have been fabricated with a functional yield of 80% on 2" slice. A balanced dual detector receiver for 155 Mbit/s applications has been made; at 2.3 GHz bandwidth 16.8pA/Hz noise, >25 dB common mode rejection.

Expected Impact

The project has established a base from which low cost products can be developed to provide a highly flexible network at physical levels. This device technology will lead to a range of modules, for instance transmitters and receivers for CMC and integrated HDWDM receivers. It is intended that this project will have a major impact on the evolution of both components and systems, thus influencing RACE strategy at a networking level.

Coordinator

BNR Europe Ltd
Address
London Road
CM17 9NA Harlow
United Kingdom

Participants (7)

Alcatel Alsthom Recherche
France
Address
Route De Nozay
91460 Marcoussis
Alcatel Italia SpA
Italy
Address
Via Trento 30
20059 Vimercate Milano
Centro Studi e Laboratori Telecomunicazioni SpA (CSELT)
Italy
Address
Via Guglielmo Reiss Romoli 274
10148 Torino
Electromagnetics Institute Telefonica de Espana SA
Spain
France Télécom
France
Address
38-40 Rue Du Général Leclerc
92131 Issy-les-moulineaux
TECHNICAL UNIVERSITY OF DENMARK
Denmark
University Of Athens
Greece