1,720,979 research outputs found
A novel polarisation independent phase conjugator/wavelength converter utilising inline fibre distributed feedback lasers
No full textWe propose and demonstrate a novel technique for optical wavelength conversion and phase conjugation by fibre four-wave mixing (FWM) using inline fibre distributed-feedback (DFB) lasers
Noise optimisation of polarisation independent wavelength converters based on dual-pump four-wave mixing
No full textFour-wave mixing (FWM) has recently attracted great attention for wavelength conversion and phase conjugation. It offers strict transparency in wavelength conversion, where the use of any modulation format is permitted. In order for a FWM-based device to be practical, various polarisation independent mechanisms have been proposed and demonstrated which include the polarisation diversity technique and the orthogonally-polarised pumps technique. In this paper, we analyse the noise properties of polarisation independent four-wave mixing based on the orthogonally-polarised pumps technique. Noise reduction using fibre gratings is experimentally demonstrated, for the first time, in a dual-pump polarisation independent four-wave mixer. A power penalty improvement in excess of 5 dB in a 10 Gbit/s RZ system is achieved
Polarisation independent all-fibre phase conjugator incorporating inline fibre DFB lasers
No full textWe propose and demonstrate a novel technique for optical wavelength conversion and phase conjugation by fibre four-wave mixing (FWM) using inline fibre distributed-feedback (DFB) lasers as orthogonally polarized pump sources. This technique features polarisation independent operation without the need for externally injected pump light. Polarisation dependency as low as 0.5dB has been achieved using this technique
Linear and non-linear dispersion compensation of short pulses using midspan spectral inversion
No full textFibre nonlinearity and dispersion may limit the repeater spacing in high speed fibreoptic transmission systems. We report experimental and numerical results on the nonlinear propagation of short optical pulses over standard non-dispersion shifted fibre links which are dispersion compensated using midspan spectral inversion. It has been found that an increased transmission nonlinearity can be tolerated if the spectral inversion is moved away from the midpoint of the span. Full recovery of the initial pulsewidth is experimentally demonstrated in the presence of nonlinearities. A system design based on these results is presented, allowing high transmitted power and long repeater spacing
Simple broadrange tuning of fibre-DFB lasers
No full textAll-fibre distributed feedback (DFB) lasers providing continuous tuning over 27nm are demonstrated for the first time. Extended wavelength coverage of the lasers is obtained using a simple bend-tuning technique which delivers undistorted outputs over the full tuning-range
Transmission of <10ps pulses over 318km standard fiber using midspan spectral inversion
No full textWe report experimental results on transmission of 5.7ps input pulses over 318km standard fibre. The minimum output pulsewidth was 9.5ps. In line filters, third order chromatic dispersion, and polarisation mode dispersion are the dominant broadening effects
Linear and non-linear dispersion compensation at ultra-high data rates using mid point spectral inversion
No full textWe report experimental and numerical results on transmission of short pulses in systems with midspan spectral inversion and standard fibre. It is shown that a larger amount of nonlinearities can be tolerated if the spectral inversion is moved away from the midpoint of the span. Full recovery of the initial pulsewidth is experimentally demonstrated in the presence of nonlinearities
Broad-band continuously tunable all-fibre DFB lasers
No full textUp to 27-nm continuous tuning is demonstrated from Er/Yb all-fiber distributed-feedback (DFB) lasers using a simple tuning technique for axial extension and compression. The demonstrated devices operate with powers up to 10 dBm and remain operating in single mode over the full tuning range. Our results represents the broadest tuning-range previously reported in any DFB laser configuration and demonstrate that uniform compression tuning of long Bragg gratings is possible with high reliability
Comparison of DSF and SOA based phase conjugators employing noise-suppressing fibre grating
No full textWe compare the performance of dispersion-shifted-fibre (DSF) and semiconductor-optical-amplifier (SOA) based phase conjugators in a 10 Gb/s non-return-to-zero transmission system with respect to conversion efficiency, noise figure and distortion. Fibre gratings are used for signal extraction and amplified spontaneous emission (ASE) suppression, allowing closer wavelength spacing and reducing the conjugation noise figure by up to 12 dB. Despite the higher SOA conversion efficiency, both conjugators give similar noise figures with ASE suppression. However, the DSF based conjugator has the advantage of distortion tolerance at higher input power
Optimisation of DSF and SOA based phase conjugators by incorporating noise-suppressing fibre gratings
No full textWe compare the performance of dispersion-shifted-fibre (DSF) and semiconductor-optical-amplifier (SOA) based phase conjugators for a 10 Gb/s non-return-to-zero system with respect to conversion efficiency, noise figure and distortion. Fibre gratings are used for signal extraction and amplified spontaneous emission (ASE) suppression, allowing closer wavelength spacing and reducing the conjugation noise figure by up to 12 dB. Despite the higher SOA conversion efficiency, both conjugators give similar noise figures with ASE suppression. However, the DSF based conjugator has the advantage of distortion tolerance at higher input power. Introduction: Optical phase conjugation has attracted much recent research attention due to its potential application for group-velocity-dispersion and self-phase-modulation compensation in mid-point spectral inversion (MPSI) systems, and also for coherent wavelength conversion in optical switching and routing. The two most promising optical phase conjugation techniques are four-wave mixing (FWM) in either dispersion-shifted fibre (DSF), or semiconductor optical amplifiers (SOA). A DSF based conjugator requires phase matching close to its zero dispersion wavelength for efficient four-wave mixing. This restricts its wavelength flexibility compared to an SOA based conjugator which offers a much wider conversion bandwidth. Furthermore, the low FWM conversion efficiency in passive DSF seems to make the SOA a preferred phase conjugating medium. However, in a practical communication system, conjugation optical signal-to-noise ratio (SNR) is more important than conversion efficiency. The noise at the conjugate wavelength is usually dominated by the amplified spontaneous emission (ASE) noise from the pump and signal. The reduction of this noise has been demonstrated in an SOA based conjugator (i) by bandpass filtering of the pump and/or signal waves before mixing, and (ii) by the insertion of a notch filter at the conjugate wavelength before the conjugator. In this letter, SOA and DSF based conjugators are compared by investigating the conversion efficiency, noise and eye opening in a 10 Gb/s non-return-to-zero (NRZ) externally-modulated system, using an identical filtering network. We report for the first time the use of fibre gratings for efficient ASE noise filtering and conjugate signal extraction. The performance enhancement using these noise-suppressing gratings is also investigated
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