Weakly-Constrained Codes for Suppression of Patterning Effects in Digital Communications

Abstract

???This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder." ???Copyright IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.???We propose weakly-constrained stream and block codes with tunable pattern-dependent statistics and demonstrate that the block code capacity at large block sizes is close to the the prediction obtained from a simple Markov model published earlier. We demonstrate the feasibility of the code by presenting original encoding and decoding algorithms with a complexity log-linear in the block size and with modest table memory requirements. We also show that when such codes are used for mitigation of patterning effects in optical fibre communications, a gain of about 0.5 dB is possible under realistic conditions, at the expense of small redundancy (???10%)

Impact of cascaded MRRs on all-optical clock recovery from 40 Gbit/s RZ-OOK signal

“…The overall results indicate that single ring MRR with rather high power coupling coefficient from bent to straight waveguide can provide reasonable amplitude fluctuation reduction when cascaded up to five devices. To improve the proposed technique weakly-constrained codes for suppression of patterning effects could be added [26]. The considerable improvement has been shown previously with active device after the converter [21] for clock recovery.…”

Power pre-emphasis for suppression of FWM in coherent optical OFDM transmission

“…Numerical simulations of a 15.6 Gbs CO-OFDM system with 100 subcarriers and 7-channel WDM have shown that up to 1dB improvement in the system Q-factor can be obtained when this power allocation method is applied. We believe that the proposed power pre-emphasis technique can be also successfully combined with the constrained channel coding [25,26] to suppress other detrimental nonlinear and linear impairments such as patterning effects due to inter carrier interference.…”

The error statistics analysis of the QPSK-modulated signal in the high-rate optical link

“…As shown above, the error statistics for 1400 km was uneven. In general, the type of error statistics can allow (or cannot allow) to reduce the bit-error rate using the special encoding schemes developed for that purpose ( [10,9]). So, it is useful to estimate the degree of "unevenness" of the statistics for the different transmission distances and for different signal powers.…”

“…In particular, they manifest themselves as uneven error statistics (i.e. patterning effects), as they make the bit-error rate (BER) dependent on the data being transmitted through the fiber ([4]- [10]). The statistical knowledge of error distributions can be used to improve the error correction schemes ([6]- [10]).…”