Exploiting the bandwidth potential of multimode optical fibres

Lead Research Organisation: University of Cambridge
Department Name: Engineering

Abstract

Historically the optical fibre was perceived to provide "unlimited" bandwidth, however, the capacity of current communications systems based on single mode optical fibre technology is very close to the limits (within a factor of 2) imposed by the physical transmission properties of single mode fibres. The major challenge facing optical communication systems is to increase the transmission capacity in order to meet the growing demand (40% increase year-on-year) whilst reducing the cost and energy consumption per bit transmitted. If new technologies are not developed to overcome the capacity limitations inherent in single mode fibres and unlock the fibre bandwidth then the growth in the digital services, applications and the economy that these drive is likely to be curtailed. The need for increased capacity in the core and metro areas of the network and within computing data centres is likely to become even more acute as optical access technologies, providing far greater bandwidths directly to the users, take hold and services such as ubiquitous cloud computing are adopted.
Multimode optical fibres (MMF) offer the potential to increase the capacity beyond that of current technologies by exploiting the spatial modes of the MMF as additional transmission paths. To fully exploit this available capacity it is necessary to use coherent optical (CO) reception and multiple-input multiple-output (MIMO) digital signal processing techniques analogous to those already used in wireless communication systems such as WiFi. This project aims to develop the technologies and sub-systems required to implement a CO-MIMO system over MMF that exceeds the capacity of current single mode fibre systems and reduces the cost and energy consumption per bit transmitted. To achieve this goal the project addresses the following key engineering challenges necessary to realise a complete system demonstrator.
Engineer the channel: The multimode optical fibre MIMO channel, unlike its wireless counterpart, presents the opportunity to engineer the optical channel to optimise its performance for MIMO operation by designing and fabricating new optical fibres, using proven solid core technology, to maximise the MIMO capacity of the fibre.
Dynamically control the channel: The transmission characteristic of the multimode optical fibre channel varies with time. We will exploit both the flexible and fast adaptive nature of digital signal processing, and the less energy intensive and slower adaptation of liquid crystal spatial light modulator based optical signal processing to compensate for the channel variation and recover the spatially multiplexed data channels.
Employ energy efficient optical amplification: In order to reduce both the energy consumption and cost per bit and to extend the propagation distance into the hundreds of kilometres region it is essential to develop optical fibre amplification technologies that provide amplification to multiple spatial and wavelength channels and thus share the cost.
Coherently detect the optical signal to exploit the wavelength and spatial domains: The developed system will combine spatial multiplexing with existing dense wavelength division multiplexing, polarisation multiplexing and multilevel modulation techniques to maximise the capacity. The key to achieving this is the use of coherent optical detection and digital signal processing, which is essential not only to fully exploit the spatial capacity of the MMF channel, but also facilitates the use of existing multiplexing techniques that are difficult to realise in conventional multimode transmission systems.
The technologies and systems developed within this project will find applications, ranging from capacity upgrades of existing MMF data networks in data and computer processing centres, through to the installation of new high capacity metro and long haul fibre transmission systems using the MIMO optimised fibres and technologies developed in this project.
 
Description The control of modes within an optical fibre allows a whole range of different attributes of the fibre to be optimised and enhanced. The standard use of multi-mode fibre is very limited in applications such as telecommunications, however with the use of modal control, these limitations can be bypassed or controlled. As an example, modal control allows different optical modes to carry different channels of data all at the same time without interference, greatly expanding the available bandwidth of the fibre. The control can be implemented at both the input and the output of the fibre allowing a huge range of different properties to be enhanced or optimised. As well as demonstrating the power and versatility of modal control, this project has also shown that the technique s created a new generation of multi-core and custom core optical fibres which can carry even more data in an optimal fashion.
Exploitation Route The work on this project has demonstrated the power of the modal control; concept. This has already been adapted for use with fibre optical sensors to create enhance functionality as well as with optical endoscopes to enhance the detection of early stage oesophageal cancer.
Sectors Aerospace, Defence and Marine,Agriculture, Food and Drink,Chemicals,Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology,Transport

URL http://www-g.eng.cam.ac.uk/CMMPE/telecoms.html
 
Description Holographic modal control has been used in the telecoms industry and is being developed by Huawei as part of their transmission network systems. This will help deliver the next generation of Internet services. The technique is also being used to improve the properties of optical fibre sensors by the company Michell Instruments. The modal control techniques have also been applied to optical fibre endoscopes for the detection of early stage esophageal cancer as part of three CRUK grants.
First Year Of Impact 2013
Sector Aerospace, Defence and Marine,Construction,Digital/Communication/Information Technologies (including Software),Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology,Transport
Impact Types Societal,Economic

 
Description CRUK Multidisciplinary Project
Amount £60,000 (GBP)
Funding ID RG75463 
Organisation Cancer Research UK 
Sector Charity/Non Profit
Country United Kingdom
Start 11/2014 
End 10/2015
 
Description Cambridge Cancer Centre Early Detection Grant
Amount £100,000 (GBP)
Organisation Cambridge Cancer Centre 
Sector Academic/University
Country United Kingdom
Start 04/2016 
End 03/2017
 
Description Cancer Research UK Multidisciplinary Project
Amount £480,000 (GBP)
Funding ID C47594/A21102 
Organisation Cancer Research UK 
Sector Charity/Non Profit
Country United Kingdom
Start 04/2016 
End 03/2019
 
Description IAA Follow on Fund
Amount £60,000 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 04/2016 
End 03/2017
 
Description Industrial PhD Studentship (S. Senanayake)
Amount £56,000 (GBP)
Organisation Michell Instruments 
Sector Private
Country United Kingdom
Start 10/2013 
End 09/2016
 
Title Holographic modal multiplexer 
Description The modal mux system is a portable transmitter and receiver system which can be moved to different labs for use in modal mux fibre systems. 
Type Of Material Improvements to research infrastructure 
Year Produced 2015 
Provided To Others? Yes  
Impact The portable mux system has allowed the mux to be used wit both a coherent detection system at UCL as well as a fully complex equalisation system 
URL http://www-g.eng.cam.ac.uk/CMMPE/telecoms.html
 
Description PhD Studentship 
Organisation Michell Instruments
Country United Kingdom 
Sector Private 
PI Contribution PhD Studentship in conjunction with the IFM Ultra Precision CIM. The student was sponsored by local company Michell Instruments as part of the IFM CIM on Ultra Precision Manufacturing. The project focused on novel; optical fibre sensors using the modal control system developed on the COMIMO project grant. PhD Completed March 2017..
Collaborator Contribution Michell paid the fees of the PhD studentship and provided testing facilities for the fibre sensors.
Impact Confidential IP filed with Michell Instruments
Start Year 2012
 
Description PhD Studentship 
Organisation University of Cambridge
Department Institute for Manufacturing
Country United Kingdom 
Sector Academic/University 
PI Contribution PhD Studentship in conjunction with the IFM Ultra Precision CIM. The student was sponsored by local company Michell Instruments as part of the IFM CIM on Ultra Precision Manufacturing. The project focused on novel; optical fibre sensors using the modal control system developed on the COMIMO project grant. PhD Completed March 2017..
Collaborator Contribution Michell paid the fees of the PhD studentship and provided testing facilities for the fibre sensors.
Impact Confidential IP filed with Michell Instruments
Start Year 2012
 
Description Modal fibre Youtube Channel 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact YouTube channel created by Dr Joel Carpenter which highlights the multi media aspects of his research into modal control in multimode fibres, The work is focused both on the scientific, educational and artistic aspects of his research into modal control in fibres. The work includes several very good tutorials on the basics of the technique which he pioneered hon the COMIMO EPSRC grant.
Year(s) Of Engagement Activity 2012,2013,2014,2015,2016
URL https://www.youtube.com/user/joelacarpenter