Abstract
We present the Almouti-type polarization-time (PT) coding scheme suitable for use in multilevel (M>or=2) block-coded modulation schemes with coherent detection. The PT-decoder is found it to be similar to the Alamouti combiner. We also describe how to determine the symbols log-likelihood ratios in the presence of laser phase noise. We show that the proposed scheme is able to compensate even 800 ps of differential group delay, for the system operating at 10 Gb/s, with negligible penalty. The proposed scheme outperforms equal-gain combining polarization diversity OFDM scheme. However, the polarization diversity coded-OFDM and PT-coding based coded-OFDM schemes perform comparable. The proposed scheme has the potential of doubling the spectral efficiency compared to polarization diversity schemes.
Highlights
The performance of fiber-optic communication systems operating at high data rates is degraded by intra-channel and inter-channel fiber nonlinearities, polarization mode dispersion (PMD), and chromatic dispersion [1]
When the channel coefficients, representing the so called channel state information (CSI), are known at the receiver side, both schemes are able to compensate for DGD of 800 ps, with negligible penalty; in the first scheme one polarization is not used at the receiver side, both polarizations are used on transmitter side, resulting in
We propose an alternative approach that can be used for a number of modulation formats including M-ary phase-shift keying (PSK), M-ary quadrature-amplitude modulation (QAM) and orthogonal frequency division multiplexing (OFDM) as well
Summary
The performance of fiber-optic communication systems operating at high data rates is degraded by intra-channel and inter-channel fiber nonlinearities, polarization mode dispersion (PMD), and chromatic dispersion [1]. The Alamouti-type detector soft estimates of symbols carried by kth subcarrier in ith OFDM symbol, sx( y )i ,k , are forwarded to the a posteriori probability (APP) demapper, which determines the symbol log-likelihood ratios (LLRs) λx(y)(s) of x- (y-) polarization by λx( y ) (nb denotes the number of bits carried by symbol.) Notice that symbol LLRs in Eq (9) are conditioned on the laser phase noise sample φPN=φT-φLO, which is a zero-mean Gaussian process (the Wiener-Lévy process [14]) with variance σ2PN=2π(ΔνT+ΔνLO)|t| (ΔνT and ΔνLO are the corresponding laser linewidths introduced earlier). The extrinsic LLRs are iterated backward and forward until convergence or pre-determined number of iterations has been reached, as explained above (see Fig. 2(c))
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
