Search

Background and Aims: Awake craniotomy often results in postoperative aphasia. Over the last several decades, neurosurgical technologies have evolved, increasing resection precision for the surgeon (e.g., intraoperative fMRI). However, one ongoing concern reported by surgical teams is delineating the extent of tissue that can be safely resected – remove too little and one may not get the desired result; remove too much and one risks impairing language function. Despite technological advances and considerable progress in the neuroanatomy of language, the Penfield three-task approach (counting, naming, reading; based on the Wernicke-Geschwind model) for intraoperative language mapping remains the standard. Although this can elicit speech-arrest and “aphasic” errors, the basic tasks are not aligned with current language models and fail to probe subtler language functions that are often impaired postoperatively (De Witte & Marien, 2013). For example, stimulation of anterior and posterior cortex could invoke reading problems due to different reasons (e.g., phonology, vision). Preserving language function is therefore reliant on probing a spectrum of multimodal functions during cortical mapping. This requires a test-battery driven by a multifaceted theoretical framework (MRI, experimental neuropsychology etc.). The first step towards developing such a tool is to establish which intraoperative tasks are effective in mapping language function and minimising aphasic symptoms. Methods: A systematic review was conducted. Databases were searched for articles using key terms (e.g., “brain tumour” AND “neurosurgery” AND “language” etc.). This returned 7294 articles screened for inclusion by title, abstract and full-text by independent reviewers based on the following criteria: 1) patients aged >18 years; 2) brain tumour excision under awake conditions or general anaesthesia; 3) validated language outcomes for pre-, intra- and post-operative assessment. Data were extracted from eligible papers including intervention (intraoperative tasks) and outcomes (language function pre-, intra- and post-operatively), and are currently being analysed. Results: It is expected that adopting a multimodal approach will provide better outcomes than the traditional Penfield approach. For example, employing tasks engaging different input modalities (e.g., phonology, vision) and measuring a range of processes (e.g., rhyme judgement, pattern recognition) will provide a better profile of language functioning for the surgeon. Not all modalities and processes will be affected by the tumour and resection location so task delivery should be optimised as a function of patient group (e.g., semantic tasks are more beneficial for anterior temporal resection). Conclusions: For the first time the results from this review will allow predictions to be made regarding the best combination of tasks for mapping and preserving language function in and out of theatre. It will consider important factors such as tumour location, from which more valid conclusions may be reached on how to tailor interventions. Data from cortical mapping may also provide insights into the neuroanatomy of language. The findings will provide a basis for the development of specific tasks that comprehensively and concisely assess the functions associated with a particular region pre-, intra-, and post- operatively. Such a tool is not only relevant for craniotomy but for diagnosis of different language impairments in non-tumour patients.

This paper presents WDM transmission at 2µm over 1.15km of HC-PBGF with wavelength channels selected to span a 36.3nm waveband. A total capacity of 81Gbit/s was achieved using 4 x 12.5Gbit/s NRZ-OOK external modulation and 4 x 7.7Gbit/s 4-ASK Fast-OFDM direct modulation signals.

We report a novel OFDM-transmitter operating in the emerging 2µm waveband. Sub-FEC limit transmission of a 32QAM signal over 500m of both solid and hollow-core fiber was achieved and the generation of 30Gbits 64QAM demonstrated.

World's first demonstration of WDM transmission in a HC-PBGF at the predicted low loss region of 2µm is presented. A total capacity of 16 Gbit/s is achieved using 1x8.5 Gbit/s and 3x2.5 Gbit/s channels modulated using NRZ OOK over 290 meters of hollow core fiber.

High power fibre laser sources in the 2 µm wavelength region with picosecond-scale pulse durations have attractive applications such as materials processing, eye-safe radar and nonlinear frequency conversion to midinfrared wavelengths. Current implementations are typically based on the amplification of picosecond pulses obtained from a mode-locked oscillator, and pulse energies of several hundred nano-Joule and peak powers of the order of 10 kW have been achieved.

Coherent optical communications allows for better resilience to transmission-related linear and nonlinear impairments (e.g., using binary phase shift keying, BPSK) and/or for increased capacity via the transmission of several bits per symbol (QPSK, 16 QAM, ....)

An efficient phase preserving amplitude noise limiter suitable for constant envelope phase-modulated signals is experimentally demonstrated for 10-Gb/s differential phase-shift-keying (DPSK) signals exploiting injection locking in Fabry-Pérot lasers. The limiter operates successfully over a 16.4-nm tuning range leading to 12 dB of power penalty reduction for $10 - 3 of bit-error-rate (BER) performance. © 2006 IEEE.

This paper shows, for the first time, the implementation of a WDM subsystem at the 2µm wavelength window with mixed formats. Three wavelength channels were directly modulated with BPSK Fast-OFDM at 5Gbit/s per channel, with a fourth channel NRZ-OOK externally modulated at 8.5Gbit/s giving a total capacity in excess of 20 Gbit/s.

In this study, a phase-preserving limiter based on injection locking a semiconductor laser is fully investigated as an amplitude limiter for 10 Gb/s constant envelope phase encoded signals. A theoretical analysis on the modulation bandwidth and the modulation transfer function of the injection locked laser is carried out targeting to identify the operational characteristics and the regeneration properties of the proposed amplitude limiter. The theoretical analysis demonstrates the potential of the specific limiter to amplify 25 Gbaud phase modulated signals with simultaneous regeneration of its amplitude properties. Subsequently an experimental investigation demonstrates the performance of the proposed regenerator and addresses its potential exploitation in future optical networks. The specific limiter exhibits significant amplitude noise squeezing capability and extreme implementation simplicity. © 2011 IEEE.

The performance of future ultra-long haul communication systems exploiting phase-encoded signals is likely to be compromised by noise generated during signal transmission. One potential way to mitigate such noise is to use Phase Sensitive Amplifiers (PSAs) which have been demonstrated to help remove phase as well as amplitude noise from phase-encoded signals. Recently, we showed that a PSA-based signal regenerator based on degenerate four-wave mixing can be implemented in a network-compatible manner in which only the (noisy) signal is present at the device input (black-box operation). The developed regenerator was also able to perform simultaneous wavelength conversion and multicasting, details/analysis of which are presented herein. However, this scheme was tested only with artificial noise generated in the laboratory and with the regenerator placed in front of the receiver, rather than in-line where even greater performance benefits are to be expected. Here, we address both theoretically and experimentally the important issue of how such a regenerator, operating for convenience in a multicasting mode, performs as an in-line device in an installed transmission fiber link. We also investigate the dispersion tolerance of the approach. © 2006 IEEE.

The performance of future ultralong-haul communication systems exploiting phase-encoded signals is likely to be compromised by nonlinear phase noise generated during signal transmission. One potential way to mitigate against nonlinear phase noise is to use phase-sensitive amplifiers (PSAs) that have been demonstrated to help remove such phase noise as well as to provide simultaneous signal amplitude noise suppression when operated in saturation. Recently, we have shown that a PSA-based signal regenerator based on degenerate four-wave mixing could be implemented in a network-compatible manner in which only the (noisy) signal is present at the device input (black-box operation). However, this scheme was tested only with relatively highfrequency deterministic perturbations applied to the signal. Here, we address both theoretically and experimentally the important issue of how such a regenerator works with more realistic random broadband amplitude/phase noise distributions. Good regenerative performance is demonstrated and our study also illustrates an additional unique feature of PSA-based regeneratorsnamely error correction for differentially encoded signals when placed in front of a DPSK receiver. Furthermore, we present a simplified regenerator implementation providing highly stable operation and representing a significant further step toward a practical device. © 2011 IEEE.

We present a phase locking scheme that enables the demonstration of a practical dual pump degenerate phase sensitive amplifier for 10 Gbit/s non-return to zero amplitude shift keying signals. The scheme makes use of cascaded Mach Zehnder modulators for creating the pump frequencies as well as of injection locking for extracting the signal carrier and synchronizing the local lasers. An in depth optimization study has been performed, based on measured error rate performance, and the main degradation factors have been identified. © 2011 Optical Society of America.

The exponentially increasing capacity demand in information systems will be met by carefully exploiting the complementary strengths of electronics and optics1,2. Optical signal processing provides simple but powerful pipeline functions that offer high speed, low power, low latency and a route to densely parallel execution3. A number of functions such as modulation and sampling4-7, complex filtering8 and Fourier transformation have already been demonstrated. However, the key functionality of all-optical quantization has still not been addressed effectively. Here, we report an all-optical signal processing architecture that enables, for the first time, multilevel all-optical quantization of phase-encoded optical signals. A four-wave-mixing process is used to generate a comb of phase harmonics of the input signal, and a two-pump parametric process to coherently combine a selected harmonic with the input signal, realizing phase quantization. We experimentally demonstrate operation up to six levels. © 2011 Macmillan Publishers Limited. All rights reserved.