PROJECT FINAL REPORT
Project acronym: TUCAN
Project title: Tunable CPE (Customer Premises Equipment) for Access Networks
Project duration: 3 years 1 month from July 2011 to July 2014
Coordinator (organisation): Oclaro Technology Ltd
Scientific representative of the coordinator (name and title): Dr Mike Wale
E-mail: mike.wale@oclaro.com
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Final publishable summary report
Executive summary
The TUCAN project aimed to develop and demonstrate the technology for a remotely tunable
universal Customer Premises Equipment (CPE) module transmitter for high bandwidth (up to
10Gb/s) Wavelength Division Multiplexed (WDM) Passive Optical access Networks. It
complemented the IMPACT project which concentrated on the system aspects. The 37 month
project comprised Oclaro (Coordinator, UK), ADVA Optical Networking SE (DE), University of
Cambridge (UK), ELCON Systemtechnik (DE), Gooch & Housego (UK), University College
London (UK) and TU Berlin (DE).
The overall project scope was as planned, although a module-based approach to the
application of Photonic Integrated Circuits (PICs) was employed, rather than fully monolithic
solution as originally envisaged. Tunable wideband DBR lasers based on the Aluminium
Quaternary (AlQ) materials system were developed, together with the technology to integrate
them with a Mach-Zehnder (MZ) modulator with potential for low cost volume production.
Fully integrated monolithic tunable laser-MZ PICs were realised within the project and
achieved state of art performance. Laser control algorithms were developed and linked to the
module control firmware. Two different prototype modules were developed as test vehicles
and to demonstrate the capability of the overall package.
The PIC-based transceiver modules were integrated into Customer Premises Equipment
(CPE) and ultimately trialled in a full system configuration, as developed within the sister
PIANO+ project IMPACT. Experimental results achieved in these trials give us good
confidence in the system concept and technology base needed for successful large-scale
implementation. The project culminated in a successful field trial in Austria conducted within
the related PIANO+ IMPACT project.
Summary of project context and objectives
The TUCAN project addressed the component needs for Customer Premises Equipment
(CPE) for high data rate (1 to 10Gb/s) WDM PON access networks. Current optical Time
Division Multiplexed access networks, such as GPON, operate with a single upstream
wavelength and utilise low cost, fixed wavelength lasers. Such networks have limited
scalability and there is accordingly great interest in next-generation solutions such as WDMPON.
For WDM PONs it was essential to develop a universal CPE WDM transmitter that could be
used on any network unit, regardless of the operating wavelength, i.e. it must be either
‘colourless’ or tunable. Tunable Distributed Bragg Reflector (DBR) lasers provide a solution
that allows flexibility in system design and hence represent a widely applicable and futureproof solution. However, the cost, power consumption and wavelength control requirements of
currently available products has prohibited their use in access links until now.
The project targeted the development of a low cost tunable transceiver technology that will be
capable of meeting access network cost targets whilst maintaining high performance and
reducing power requirements.
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Description of the main S&T results/foregrounds
State of the art Indium Phosphide (InP) laser and integrated laser-modulator designs have
been developed using the aluminium quaternary (AlQ) material system to enhance behaviour
and performance at higher temperature, thereby reducing thermal control requirements,
power dissipation and module cost. The Oclaro wideband tunable laser designs have been
enhanced, enabling this capability to be integrated on a single InP chip with a high
performance Mach-Zehnder optical modulator. This approach provides a truly cost-focused
design solution to help achieve the cost and performance targets required by the system.
As part of this low cost system approach, a new wavelength assignment and control system
was designed and implemented using the inherent wavelength allocation performed by the
channel selective nature of arrayed waveguide gratings inherent within the selected WDM
PON architecture (so called “wavelength routed WDM-PON”). This has enabled a system
using feedback from the optical line terminal (OLT) and novel wavelength selection and
control algorithms to be demonstrated. The laser automatically locates the correct operating
channel and the remains at the correct wavelength to within ±2.5GHz, without any
impairment. Work on tuning control algorithms led by UCAM and UCL has demonstrated the
viability of operation over a wide laser temperature range, which may permit further reductions
in module cost and power. Based on the knowledge developed in the project, we envisage a
major reduction in the requirements for pre-calibration of the laser at the factory, with
corresponding savings in product cost.
Prototype assemblies to demonstrate the functional laser, modulator and controls were
supported by Gooch & Housego and Oclaro. “Prototype A” used laser chips and subassembly packaging from Oclaro to create a test vehicle allowing tunable laser assessment.
Laser chip-on-carrier assemblies were produced by TUB using both wire-bond and flip-chip
approaches, producing functioning laser assemblies in both cases. Packaging of PIC chip-oncarrier assemblies into transmitter packages was then carried out by Gooch & Housego.
“Prototype B” built by Oclaro contained the laser-modulator PICs designed and manufactured
in the project, all packaged within an industry standard SFP+ module form factor. This work
generated an SFP+ with unique functionality, specifically to demonstrate the operation of
remote wavelength control in a CPE using a centralised wavelength locking technique.
Modules were supplied for experimental system evaluation and the field trial.
Beside the sequential testing of prototype “A” and “B”, TUB built prototype “A” both as a
traditional die and wire assembly and as a flip chip assembly, in order to compare production
benefits such as reduced process time and material usage, as well as potential for functional
improvements like higher data rate. UCL verified their functionality and Flip Chip assembly,
even with Thermo Compression bonding of brittle III/V semiconductors, was shown as a
viable alternative assembly method with potential for cost reduction and higher data rate.
The demonstration system used ELCON customer premises equipment (CPE) with integrated
T-SFP+ optical module and interface PCBA supplied by Oclaro. The interface PCBA provided
decoding of a downlink Embedded Communications Channel (ECC) and generation of a
channel-specific uplink pilot tone. The ECC was used to convey network feedback for remote
CPE wavelength control using algorithms developed by UCAM. The communications protocol
was defined by ADVA (who also implemented the head end wavelength controller device
integrated into the OLT central office side of the system) and was based on either BPSK or an
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amplitude-modulated OOK scheme operating at 1kbps. For future developments the interface
PCBA functionality would be integrated into the T-SFP+ module.
Project research and development activities concluded with a successful field trial in
Gmunden, Austria, using installed infrastructure owned and operated by Energie AG, a
partner in a sister PIANO+ project IMPACT. Along with excellent link performance, this field
trial demonstrated the advanced management features developed in this project and in
IMPACT, including simultaneous remote wavelength control of three CPEs over a 25km link
of deployed fibre. We are pleased to note that the field trial generated significant publicity for
the technology and systems solutions developed within the project.
Fig. 1: Experimental Setup of the tunable WDM-PON System in the Field Trial
Fig. 2: Fibre route in the network of Energie AG between the central office in Gmunden and Laakirchen.
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Potential impact (including the socio-economic impact and the wider societal
implications of the project so far) and the main dissemination activities and
exploitation of results
The project has delivered several important technological advances, with high-performance,
high-temperature Indium Phosphide PICs and embedded laser control techniques being
amongst the key items to note. Conference and journal papers have been generated and
submitted. Market demand for WDM-PON based systems is growing and clearer migration
paths from the current GPON type architectures are being defined within industry
standardisation bodies (e.g. FSAN and ITU-T study group 15 question 2 as well as question
6), where the project partner ADVA Optical Networking is actively contributing. This
standardisation effort assists the wider adoption of the WDM-PON approach and the
corresponding technologies.
A number of aspects developed within the project are directly exploitable by the partners
within the consortium, including cost-effective integrated tunable lasers and transceivers
employing InP AlQ technology, and algorithms for automated control of uncooled lasers.
Together they bring the prospect of cost-effective access networks capable of delivering more
than 1Gb/s to the consumer several steps nearer. It should be noted that apart from traditional
fibre-to-the-home applications the 10 Gb/s capable system can also be used in so-called
“mobile front haul” (MFH) systems, which significantly gained interest during the course of the
project especially stemming from LTE deployments. Such systems need to be able to
transport CPRI data rates up to 10.1 Gb/s (CPRI line rate option 8).
Project public website and relevant contact details.
www.pianoplus.eu/tucan
mike.wale@oclaro.com
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