Final Report Summary - POLIFIRE (Polarisation impairments mitigations in fibre Raman effect assisted systems)
Project background: At present, there is a large demand for green optical networks, namely backbone optical networks with an increased optical fibre capacity and transmission distance at low-operating cost and reduced power consumption. This is dictated by growing applications of e-commerce, e-banking and e-business, broadcasting media and medical applications. Modern optical communication systems are mainly based on long-span fibre networks which actively exploit optical fibre amplifiers. Unlike generic approaches using erbium-doped fibre (EDF)-based in-line amplifiers (ILA) for regeneration of fading optical signal, project POLIFIRE has addressed the disruptive change in information and communication solutions towards drastic energy saving (green) technologies in the context of preliminary study and trial tests of a new technological approach, as well as cross-sectoral and multidisciplinary training of the recruited researcher. A new technology demonstrated the ways to increased un-repeatered (without ILA) transmission distance (of 300 km) and transmission rate (above 100 Gb / s) by applying a fibre Raman amplifier (FRA) with mitigated polarisation impairments, namely polarisation mode dispersion (PMD) and polarisation dependent gain (PDG). FRA uses an intrinsic property of silica fibre to create amplification and so to compensate losses without additional ILAs. PMD leads to the pulse broadening caused by varying group velocities for the pulses with different states of polarisation (SOPs) whereas PDG leads to the uncontrollable output gain variation caused its dependence on the input signal SOP.
Overview of results: The main result of the POLIFIRE is in a theoretical approach to an optimal fibre spinning profile for simultaneously increasing the Raman gain and suppression of polarisation impairments. For theoretical characterisation of the approach feasibility, a new model of FRA accounting for random birefringence of fibre and fibre spinning profile has been developed. To find Raman gain and gain fluctuations averaged over the fibre birefringence fluctuations, the stochastic generator approach was implemented. As a result, stochastic equations have been transformed into simplified ordinary differential equations with substantially (factor 100) reduced time of computation. It gave opportunity to consider cases of forward and backward pump along with different fibre spinning profiles and find optimal parameters by a cost effective way.
In view of similarity of two-scale periodically spun FRA (SFRA) to the periodically driven excitable system (ES), we have found resonance-like de-correlation of pump and signal SOPs and polarisation pulling equivalent to the stochastic resonance (SR) and dynamic localisation (DL) in ES. We demonstrated that the interaction between pump and signal SOPs in a FRA periodically spun with the period of 1 m plays the role of a potential, noise is defined by the random birefringence in a fibre, and a long period (> 100 m) fibre spinning plays role of an adiabatic forcing. As a result, it was possible to reproduce the SR in two-scale spun fibre in terms of de-correlating the pump and signal SOPs with simultaneous suppression of PDG and PMD and increasing the Raman gain.
DL has been demonstrated in the form of an activated polarisation pulling for an optimal fibre spinning profiles, namely enhanced 'attracting' of the signal SOP to the pump SOP, along with increased Raman gain, suppressed gain fluctuations and PMD.
Available on the telecommunication market low PMD fibre (Corning LEAF) has no optimal fibre spinning profile and so, as it was shown at Aston Institute of Photonic Technologies (AIPT), suffers from polarisation and modulation instabilities (POI & MI) and increased pump-to-signal relative intensity noise (RIN) transfer. As shown at Alcatel-Lucent, mitigation of these impairments and so 8 x 112 Gb / s over 300 km transmission can be done for the cost of a high electrical power consumption and a post-processing rather than a real-time processing. Thus, the major condition for an increased transmission rate and a distance in high-capacity un-repeatered links by a cost-effective way is in further practical steps related to the drawing fibres with two-scale fibre spinning profile.
Approaches to the characterisation of the polarisation impairments in FRAs have been used in experimental study of noise driven polarisation instabilities in fibre lasers (FRLs). We demonstrated that increased noise in the laser cavity can result in spontaneous mode-locking and in intermittent self-pulsing (ISP), namely self-pulsing with strong, and irregular inter-spike intervals. Intermittency is one of the complex features of developed turbulence and studies of intermittency are important for understanding the fundamental aspects of multi-mode FRLs operation. We have found a new type of ISP caused by polarisation switching in FRLs. The practical implementation of the obtained results can be in the design of stabilised multi-wavelength FRLs for telecommunication and sensing applications.
Implementation of passively mode-locking techniques results in suppression of stochastic dynamics and so in a regular polarisation dynamic in the form of new types of vector solitons (VS), namely short pulses with the specific shape. Unlike previously observed polarisation locked and polarisation rotating VS with SOPs either locked or evolving with a period of few round trips, we have found experimentally and theoretically new types of VSs with the SOP slowly evolving with the period of thousands round-trips. The obtained results can find a practical implementation in secure communications, trapping and manipulation of atoms and nanoparticles and vectorial control of magnetisation.
Conclusions: The results of POLIFIRE are reflected in 6 journal papers published as well as in 12 papers published in conference proceeding. The project academic impact can be summarised as follows:
(a) Two-scale fibre spinning is a cost-effective way to increased optical fibre capacity and transmission distance in high capacity un-repeatered links at low-operating cost and reduced power consumption.
(b) New types of FRLs (ultra-long continuous wave, mode-locked, random etc.) with characteristics required in metrology, fibre-optic communication, medicine, material processing and micro-machining can be developed based on the novel results on noise driven polarisation instabilities.
(c) New type of VS characterised experimentally and theoretically can find implementation in secure communications, trapping and manipulation of atoms and nanoparticles and vectorial control of magnetisation.
(d) New vector model of a FRA will benefit researchers in the context of development of advanced algorithms and numerical methods for stochastic nonlinear systems.
Impact on the career development: During the research and training period at Aston Institute of Photonic Technologies (AIPT), research fellow Dr Sergey Sergeyev:
(a) acquired theoretical and experimental competence in quasi-lossless fibre optic transmission links based on ultra-long fibre Raman lasers;
(b) made an innovative update of such systems in terms supressed polarisation impairments and intensity fluctuations;
(c) acquired competence in project management, teaching and research commercialisation methods;
(d) increased number academic and industrial collaboration links at the level of Principal Investigator;
(e) organised and managed joint research on FRLs (Raman and erbium doped) with visiting researchers and the staff members of the AIPT.
As a result, Dr Sergeyev was able to achieve his career goals in acquiring senior research fellow position at AIPT and Coordinator role in Marie Curie IAPP (GRIFFON, Grant Agreement 324391) project.
Socio-economic impact of the project: The project contributes to the European Union (EU) fibre optic-based information-carrying digital communications infrastructure through results on a low-cost and high-capacity optical communication system and to photonics industry through increased demand in advanced fibre-optic components and systems. The results of research and training demonstrate the technical excellence, and so contribute to the transition of Europe to a knowledge-based society, driving the transformation of industry towards higher added value and sustainable development as outlined in information and co information and communication technology (ICT) strategic objectives.
Impact on standards: The project will have impact on standardisation through bringing to market new laser sources for advanced transmission schemes and high-speed optical communications. The project results will lead to increase the span for un-repetered transmission and, thus, to decrease of number of amplifiers and reduction of a consumed power per transmitted bit over fixed distance.
Societal impact: The reduction of the fast optical communications cost together with simultaneous increase of bandwidth and speed will enable far more citizens across the EU to take advantages of fibre communication links in the context of improved quality of service in e-banking and e-business, high-definition (HD) and three-dimensional (3D) TV, high-quality telephony, and medical diagnostics. Thus, project outputs will improve quality of life, increase the number of employees in the sector of ICT service, and will remove the separation between largely connected districts and those who left behind.
Environmental impact: Proposed system has reduced power consumption and operational costs in view of absence of electrical cable embedded into the optical cable to drive online amplifiers.
Overview of results: The main result of the POLIFIRE is in a theoretical approach to an optimal fibre spinning profile for simultaneously increasing the Raman gain and suppression of polarisation impairments. For theoretical characterisation of the approach feasibility, a new model of FRA accounting for random birefringence of fibre and fibre spinning profile has been developed. To find Raman gain and gain fluctuations averaged over the fibre birefringence fluctuations, the stochastic generator approach was implemented. As a result, stochastic equations have been transformed into simplified ordinary differential equations with substantially (factor 100) reduced time of computation. It gave opportunity to consider cases of forward and backward pump along with different fibre spinning profiles and find optimal parameters by a cost effective way.
In view of similarity of two-scale periodically spun FRA (SFRA) to the periodically driven excitable system (ES), we have found resonance-like de-correlation of pump and signal SOPs and polarisation pulling equivalent to the stochastic resonance (SR) and dynamic localisation (DL) in ES. We demonstrated that the interaction between pump and signal SOPs in a FRA periodically spun with the period of 1 m plays the role of a potential, noise is defined by the random birefringence in a fibre, and a long period (> 100 m) fibre spinning plays role of an adiabatic forcing. As a result, it was possible to reproduce the SR in two-scale spun fibre in terms of de-correlating the pump and signal SOPs with simultaneous suppression of PDG and PMD and increasing the Raman gain.
DL has been demonstrated in the form of an activated polarisation pulling for an optimal fibre spinning profiles, namely enhanced 'attracting' of the signal SOP to the pump SOP, along with increased Raman gain, suppressed gain fluctuations and PMD.
Available on the telecommunication market low PMD fibre (Corning LEAF) has no optimal fibre spinning profile and so, as it was shown at Aston Institute of Photonic Technologies (AIPT), suffers from polarisation and modulation instabilities (POI & MI) and increased pump-to-signal relative intensity noise (RIN) transfer. As shown at Alcatel-Lucent, mitigation of these impairments and so 8 x 112 Gb / s over 300 km transmission can be done for the cost of a high electrical power consumption and a post-processing rather than a real-time processing. Thus, the major condition for an increased transmission rate and a distance in high-capacity un-repeatered links by a cost-effective way is in further practical steps related to the drawing fibres with two-scale fibre spinning profile.
Approaches to the characterisation of the polarisation impairments in FRAs have been used in experimental study of noise driven polarisation instabilities in fibre lasers (FRLs). We demonstrated that increased noise in the laser cavity can result in spontaneous mode-locking and in intermittent self-pulsing (ISP), namely self-pulsing with strong, and irregular inter-spike intervals. Intermittency is one of the complex features of developed turbulence and studies of intermittency are important for understanding the fundamental aspects of multi-mode FRLs operation. We have found a new type of ISP caused by polarisation switching in FRLs. The practical implementation of the obtained results can be in the design of stabilised multi-wavelength FRLs for telecommunication and sensing applications.
Implementation of passively mode-locking techniques results in suppression of stochastic dynamics and so in a regular polarisation dynamic in the form of new types of vector solitons (VS), namely short pulses with the specific shape. Unlike previously observed polarisation locked and polarisation rotating VS with SOPs either locked or evolving with a period of few round trips, we have found experimentally and theoretically new types of VSs with the SOP slowly evolving with the period of thousands round-trips. The obtained results can find a practical implementation in secure communications, trapping and manipulation of atoms and nanoparticles and vectorial control of magnetisation.
Conclusions: The results of POLIFIRE are reflected in 6 journal papers published as well as in 12 papers published in conference proceeding. The project academic impact can be summarised as follows:
(a) Two-scale fibre spinning is a cost-effective way to increased optical fibre capacity and transmission distance in high capacity un-repeatered links at low-operating cost and reduced power consumption.
(b) New types of FRLs (ultra-long continuous wave, mode-locked, random etc.) with characteristics required in metrology, fibre-optic communication, medicine, material processing and micro-machining can be developed based on the novel results on noise driven polarisation instabilities.
(c) New type of VS characterised experimentally and theoretically can find implementation in secure communications, trapping and manipulation of atoms and nanoparticles and vectorial control of magnetisation.
(d) New vector model of a FRA will benefit researchers in the context of development of advanced algorithms and numerical methods for stochastic nonlinear systems.
Impact on the career development: During the research and training period at Aston Institute of Photonic Technologies (AIPT), research fellow Dr Sergey Sergeyev:
(a) acquired theoretical and experimental competence in quasi-lossless fibre optic transmission links based on ultra-long fibre Raman lasers;
(b) made an innovative update of such systems in terms supressed polarisation impairments and intensity fluctuations;
(c) acquired competence in project management, teaching and research commercialisation methods;
(d) increased number academic and industrial collaboration links at the level of Principal Investigator;
(e) organised and managed joint research on FRLs (Raman and erbium doped) with visiting researchers and the staff members of the AIPT.
As a result, Dr Sergeyev was able to achieve his career goals in acquiring senior research fellow position at AIPT and Coordinator role in Marie Curie IAPP (GRIFFON, Grant Agreement 324391) project.
Socio-economic impact of the project: The project contributes to the European Union (EU) fibre optic-based information-carrying digital communications infrastructure through results on a low-cost and high-capacity optical communication system and to photonics industry through increased demand in advanced fibre-optic components and systems. The results of research and training demonstrate the technical excellence, and so contribute to the transition of Europe to a knowledge-based society, driving the transformation of industry towards higher added value and sustainable development as outlined in information and co information and communication technology (ICT) strategic objectives.
Impact on standards: The project will have impact on standardisation through bringing to market new laser sources for advanced transmission schemes and high-speed optical communications. The project results will lead to increase the span for un-repetered transmission and, thus, to decrease of number of amplifiers and reduction of a consumed power per transmitted bit over fixed distance.
Societal impact: The reduction of the fast optical communications cost together with simultaneous increase of bandwidth and speed will enable far more citizens across the EU to take advantages of fibre communication links in the context of improved quality of service in e-banking and e-business, high-definition (HD) and three-dimensional (3D) TV, high-quality telephony, and medical diagnostics. Thus, project outputs will improve quality of life, increase the number of employees in the sector of ICT service, and will remove the separation between largely connected districts and those who left behind.
Environmental impact: Proposed system has reduced power consumption and operational costs in view of absence of electrical cable embedded into the optical cable to drive online amplifiers.