2 research outputs found
Synchronisation in sampled receivers for narrowband digital modulation schemes.
SIGLEAvailable from British Library Document Supply Centre- DSC:DXN0033576 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Digital signal processing for coherent optical fibre communications
In this thesis investigations were performed into digital signal processing (DSP)
algorithms for coherent optical fibre transmission systems, which provide improved
performance with respect to conventional systems and algorithms. Firstly, an
overview of coherent detection and coherent transmission systems is given.
Experimental investigations were then performed into the performance of digital
backpropagation for mitigating fibre nonlinearities in a dual-polarization quadrature
phase shift keying (DP-QPSK) system over 7780 km and a dual-polarization 16-
level quadrature amplitude modulation (DP-QAM16) system over 1600 km. It is
noted that significant improvements in performance may be achieved for a nonlinear
step-size greater than one span. An approximately exponential relationship was
found between performance improvement in Q-factor and the number for required
complex multipliers.
DSP algorithms for polarization-switched quadrature phase shift keying (PS-QPSK)
are then investigated. A novel two-part equalisation algorithm is proposed which
provides singularity-free convergence and blind equalisation of PS-QPSK. This
algorithm is characterised and its application to wavelength division multiplexed
(WDM) transmission systems is discussed.
The thesis concludes with an experimental comparison between a PS-QPSK
transmission system and a conventional DP-QPSK system. For a 42.9 Gb/s WDM
system, the use of PS-QPSK enabled an increase of reach of more than 30%. The
resultant reach of 13,640 km was, at the time of publication, the longest transmission
distance reported for 40 Gb/s transmission over an uncompensated link with standard
fibre and optical amplification