Ultra high speed optical transmission using subcarrier-multiplexed four-dimensional LDPC-coded modulation

Abstract

We propose a subcarrier-multiplexed four-dimensional LDPC bit-interleaved coded modulation scheme that is capable of achieving beyond 480 Gb/s single-channel transmission rate over optical channels. Subcarrier-multiplexed four-dimensional LDPC coded modulation scheme outperforms the corresponding dual polarization schemes by up to 4.6 dB in OSNR at BER 10(-8).

Four-Dimensional Nonbinary LDPC-Coded Modulation Schemes for Ultra-High-Speed Optical Fiber Communication

“…There are three constellation sizes considered, namely 16, 32, and 64. In order to compare against the 4-D BI-LDPC-CM performance curves presented previously in [2], we use the same signal constellations. Using Fig.…”

“…As the slopes of the performance curves indicate, the gaps between nonbinary and the corresponding binary curves are expected to increase for lower BERs such as and , signifying larger NCGs and larger additional coding gains at lower BERs when using the proposed NB-LDPC-CM scheme. We should note that any 4-D constellations other than the ones in [2] can be used. For example, the optimum constellations presented by Sloane et al [8] may provide an additional 0.5 dB coding gain at the BER of at the expense of increased implementation complexity since the optimum constellation points require 12-digit accuracy, which is much larger compared to accuracy required by the 4-D regular polytopes used in [2].…”

“…Thus solutions for 100 GbE and beyond need to attain ultra high transmission speeds in terms of aggregate bit rates while keeping the operating symbol rates low to facilitate nonlinearity and PMD management. A promising solution employing coded modulation using low-density paritycheck (LDPC) codes as component codes has already been discussed in our previous works [1], [2]. The underlying idea is to use spectrally-efficient modulation formats at low symbol rates along with strong LDPC codes for forward error correction (FEC) in order to accomplish reliable communication at high aggregate bit rates.…”

“…As a result, one can exploit this four-dimensional (4-D) signal space to set up more power-efficient signal constellations than one could do using the 2-D signal space-by increasing the Euclidean distance between constellation points for a given average signal power [3]. 4-D bit-interleaved LDPC-coded modulation (4-D BI-LDPC-CM) employing binary LDPC codes for FEC was discussed in [2]. In this letter, we employ nonbinary LDPC codes for FEC and show that the proposed 4-D nonbinary LDPC-coded modulation (4-D NB-LDPC-CM) scheme can provide larger coding gains than the corresponding 4-D BI-LDPC-CM scheme.…”

“…1 depicts the transmitter and receiver configurations for the proposed 4-D NB-LDPC-CM scheme. Compared to prior-art 4-D BI-LDPC-CM scheme presented in [2], we observe the following differences: 1) the set of binary LDPC encoders are replaced by a single -ary LDPC encoder, 2) the block interleaver unit, which distributes codeword bits of each binary LDPC encoder used in BI-LDPC-CM over all of transmitted symbols [2], is eliminated, 3) the feedback loop into the maximum a posteriori probability (MAP) detector from the decoding unit is eliminated, and 4) symbol-to-bit and vice versa conversion interfaces are eliminated since the nonbinary 1041-1135/$26.00 © 2011 IEEE decoder operates at the symbol level. We should highlight item 3 further.…”