Bidirectional symmetric 8x10. 7Gb/s WDM-PON over 108 km installed fiber using low complexity polarization-insensitive coherent ONUs

Polarization-time block-coded OFDM-QPSK downstream channels are robustly detected using a polarization-insensitive coherent receiver, consisting of only a 3dB coupler and single balanced PD. 8 x10.7Gb/s channels are bidirectionally transmitted over 108 km installed fiber achieving a 1:16-way passive split

Real time dynamic strain monitoring of optical links using the backreflection of live PSK data.

A major cause of faults in optical communication links is related to unintentional third party intrusions (normally related to civil/agricultural works) causing fiber breaks or cable damage. These intrusions could be anticipated and avoided by monitoring the dynamic strain recorded along the cable. In this work, a novel technique is proposed to implement real-time distributed strain sensing in parallel with an operating optical communication channel. The technique relies on monitoring the Rayleigh backscattered light from optical communication data transmitted using standard modulation formats. The system is treated as a phase-sensitive OTDR (ΦOTDR) using random and non-periodical non-return-to-zero (NRZ) phase-shift keying (PSK) pulse coding. An I/Q detection unit allows for a full (amplitude, phase and polarization) characterization of the backscattered optical signal, thus achieving a fully linear system in terms of ΦOTDR trace coding/decoding. The technique can be used with different modulation formats, and operation using 4 Gbaud single-polarization dual PSK and 4 Gbaud dual-polarization quadrature PSK is demonstrated. As a proof of concept, distributed sensing of dynamic strain with a sampling of 125 kHz and a spatial resolution of 2.5 cm (set by the bit size) over 500 m is demonstrated for applied sinusoidal strain signals of 500 Hz. The limitations and possibilities for improvement of the technique are also discussed.This work was supported by the European Research Council through Starting Grant UFINE (Grant no. 307441), the Spanish MINECO through project TEC2013-45265-R, PCIN-2015- 219, and the regional program SINFOTON-CM: S2013/MIT-2790. HFM acknowledges EU funding through the FP7 ITN ICONE program, gr. #608099. SML acknowledges funding from the Spanish MINECO through a “Ramon y Cajal” contract. UK EPSRC funding through project EP/J008842/1

Comparison of low complexity coherent receivers for UDWDM-PONs (λ-to-the-User)

It is predicted that demand in future optical access networks will reach multigigabit/s per user. However, the limited performance of the direct detection receiver technology currently used in the optical network units at the customers' premises restricts data rates per user. Therefore, the concept of coherent-enabled access networks has attracted attention in recent years, as this technology offers high receiver sensitivity, inherent frequency selectivity, and linear field detection enabling the full compensation of linear channel impairments. However, the complexity of conventional (dual-polarization digital) coherent receivers has so far prevented their introduction into access networks. Thus, to exploit the benefits of coherent technology in access networks, low complexity coherent receivers, suitable for implementation in ONUs, are needed. In this paper, the recently proposed low complexity coherent (i.e., polarization-independent Alamouti-coding heterodyne) receiver is, for the first time, compared in terms of its minimum receiver sensitivity with five previously reported receiver designs, including a detailed discussion on their advantages and limitations. It is shown that, of all the configurations considered, the Alamouti-coding based receiver approach allows the lowest number of photons per bit (PPB) transmitted (with a lower bound of 15.5 PPB in an ideal implementation of the system), while requiring the lowest optical receiver hardware complexity (in terms of the optical component count). It also exhibits comparable complexity to the currently deployed direct-detection receivers, which typically require over 1000 PPB. Finally, a comparison of experimentally achieved receiver sensitivities and transmission distances using these receivers is presented. The highest spectral efficiency and longest transmission distance at the highest bit rate (10 Gb/s) was reported using the Alamouti-coding receiver, which is also the only one, to date, to have been demonstrated in a full system bidirectional transmission

Real time dynamic strain monitoring of optical links using the backreflection of live PSK data

A major cause of faults in optical communication links is related to unintentional third party intrusions (normally related to civil/agricultural works) causing fiber breaks or cable damage. These intrusions could be anticipated and avoided by monitoring the dynamic strain recorded along the cable. In this work, a novel technique is proposed to implement realtime distributed strain sensing in parallel with an operating optical communication channel. The technique relies on monitoring the Rayleigh backscattered light from optical communication data transmitted using standard modulation formats. The system is treated as a phase-sensitive OTDR (ΦOTDR) using random and non-periodical non-return-to-zero (NRZ) phase-shift keying (PSK) pulse coding. An I/Q detection unit allows for a full (amplitude, phase and polarization) characterization of the backscattered optical signal, thus achieving a fully linear system in terms of ΦOTDR trace coding/decoding. The technique can be used with different modulation formats, and operation using 4 Gbaud single-polarization dual PSK and 4 Gbaud dual-polarization quadrature PSK is demonstrated. As a proof of concept, distributed sensing of dynamic strain with a sampling of 125 kHz and a spatial resolution of 2.5 cm (set by the bit size) over 500 m is demonstrated for applied sinusoidal strain signals of 500 Hz. The limitations and possibilities for improvement of the technique are also discussed.European CommissionMinisterio de Economía y CompetitividadComunidad de Madri

Error probability performance of a short-reach multicore fiber optical interconnect transmission system

A standalone module for rectangular array multicore fiber (MCF)-based optical interconnect (OI) is realized that includes inherent intercore crosstalk and provides space division multiplexed coupling/decoupling of optical power. The module is integrated in a short-reach communication system to provide bit error probability (BEP). Next, a closed-form equation for BEP applicable to MCF OI with intercore crosstalk is derived. For characteristic parameters of the module, results obtained by two approaches agree within 1% for 40 Gbps per channel and predict an error-free transmission of aggregated data rate of 2.5 Tbps through the MCF OI under consideration

Digital signal processing based on inverse scattering transform

Through numerical modeling, we illustrate the possibility of a new approach to digital signal processing in coherent optical communications based on the application of the so-called inverse scattering transform. Considering without loss of generality a fiber link with normal dispersion and quadrature phase shift keying signal modulation, we demonstrate how an initial information pattern can be recovered (without direct backward propagation) through the calculation of nonlinear spectral data of the received optical signal

Physical activity levels and motivational responses of boys and girls: A comparison of direct instruction and Tactical Games Models of games teaching in physical education

The purpose of this study was to independently determine the levels of moderate-to-vigorous physical activity (MVPA) and self-determined motivation of both boys and girls as they participated in prolonged units of invasion games (i.e. 6-12 lessons) through two pedagogical models; direct instruction and the Tactical Games Model (TGM). It was hypothesized that given the differences in domain interaction and lesson structure, both boys and girls would gain higher levels of physical activity (PA) and possess higher quality motivation during TGM-based lessons when compared to direct instruction lessons. Seventy-two children aged 11-12 years; (42 boys, 30 girls) were randomly assigned to either a control or intervention group (TGM). Children wore RT3® triaxial accelerometers over a 12 week period to objectively measure time spent in MVPA. The System for observing Fitness Instruction Time (SOFIT) tool was completed during each lesson to additionally assess lesson context information and teacher behavior. SDT questionnaires were also completed, pre and post-intervention. Boys in the TGM condition displayed significantly higher levels of MVPA in both rugby and football activities in comparison to the control group although no significant differences in motivation were noted post-intervention. While girls in the TGM condition recorded comparable PA levels in the football sessions, they recorded significantly lower PA activity levels in the netball lessons. There were no significant differences in girls’ motivation post-intervention. It is recommended that future studies build on this research by continuing to examine PA and the quality of student motivation while using GCAs over prolonged unit lengths (i.e. greater than 12 lessons) using structural equation modeling techniques to assess the relationships between, and mediating influences of, SDT constructs on PA levels

Hybrid Organic-Inorganic Coordination Complexes as Tunable Optical Response Materials.

Novel lead and bismuth dipyrido complexes have been synthesized and characterized by single-crystal X-ray diffraction, which shows their structures to be directed by highly oriented π-stacking of planar fully conjugated organic ligands. Optical band gaps are influenced by the identity of both the organic and inorganic component. Density functional theory calculations show optical excitation leads to exciton separation between inorganic and organic components. Using UV-vis, photoluminescence, and X-ray photoemission spectroscopies, we have determined the materials' frontier energy levels and show their suitability for photovoltaic device fabrication by use of electron- and hole-transport materials such as TiO2 and spiro-OMeTAD respectively. Such organic/inorganic hybrid materials promise greater electronic tunability than the inflexible methylammonium lead iodide structure through variation of both the metal and organic components

Bidirectional wavelength-division multiplexing transmission over installed fibre using a simplified optical coherent access transceiver

High-speed broadband services require optical fibres in access networks, in which multiple subscribers are connected to service providers, to satisfy the continuously growing bandwidth demand. The primitive signaling scheme used in access networks enables the use of low-cost equipment but diminishes the bandwidth available to end-users. Thus, current technology will be unable to support future broadband demands. Coherent communication systems offer significantly improved power- and bandwidth-efficiency, but require fundamental simplifications to become economically viable for access networks. Here, we demonstrate a promising simplified coherent receiver exhibiting a robust performance against polarisation fluctuations over an installed fibre network. It enables the realisation of high-order modulation formats and offers high sensitivities, achieving a four-fold increase in the supported number of subscribers and approximately doubling the transmission distance compared to the recently standardized access technology. The proposed solution indicates that digital coherent technology can be feasible and transform the access networks, enabling ubiquitous new services and applications with uncontended, multi-gigabits/user broadband connections.This work was supported by the EPSRC Programme Grant UNLOC EP/J017582/1, and EP/J008842/1. Dr. Domaniç Lavery thanks the Royal Academy of Engineering under the Research Fellowships scheme for funding his fellowship. We also wish to acknowledge Dr. Will Yang and the EPSRC National Dark Fibre Infrastructure Service (NDFIS) NS/A000021/1 for providing access to the Aurora2 dark fibre network. We would like to thank Arın Lavery for his contribution to Fig.1