Alireza Sheikh

Nonbinary staircase codes for spectrally and energy efficient fiber-optic systems

We consider the design of nonbinary staircase codes with higher order modulation for spectrally and energy efficient fiber-optic systems. We optimize the code parameters based on density evolution.

Dispersion Compensation FIR Filter With Improved Robustness to Coefficient Quantization Errors

In this paper, we propose a new finite impulse response (FIR) filter for chromatic dispersion compensation which is given in closed form. We identify a relation between the out-of-band gain and the in-band error when the filter is implemented with finite-precision arithmetic. In particular, a large out-of-band gain makes the filter more sensitive to coefficient quantization errors due to finite precision digital signal processing. To improve robustness to coefficient quantization errors, our proposed filter is designed based on confining the out-of-band gain. By means of simulations, we show that our filter outperforms other existing FIR filters. The performance gain improves with increasing modulation order and decreasing number of bits used to represent the filter taps.

Probabilistically-Shaped Coded Modulation with Hard Decision Decoding for Coherent Optical Systems

We consider probabilistic shaping to maximize the achievable information rate of coded modulation (CM) with hard decision decoding. The proposed scheme using binary staircase codes outperforms its uniform CM counterpart by more than 1.3 dB for 64-QAM and 5 bits/symbol.

On Achievable Information Rates for Coherent Fiber-Optic Systems with Hard Decision Decoding

We analyze achievable information rates (AIRs) for coherent fiber-optic systems with hard decision decoding and show that binary codes achieve higher rates than nonbinary codes, which translates into larger transmission reach. This result is confirmed by simulation of staircase codes.