We consider performance-complexity tradeoffs when a soft-decision low-density parity-check code is used in concatenation with a hard-decision error-correcting code, such a staircase code. The inner code is carefully designed to reduce errors to the point where the outer code can provide the required error-correcting performance.
Laser beam diffraction and turbulence can potentially reduce secure key rates for CV-QKD in satellite to ground communications. Using previously derived formulas for discrete four-state modulation and reverse reconciliation, we highlight parameters that yield rates exceeding 50 Mbps and estimate percentage reduction due to turbulence.
To overcome the low-reconciliation-efficiency problem of Gaussian modulation (GM)-based-CV-QKD, we propose to use discretized-GM-based-CV-QKD. This scheme has complexity and reconciliation-efficiency similar to discrete modulation (DM)-based-CV-QKD and at the same time solves for the problem of nonexistence of strict security proofs for DM-CV-QKD under collective attacks.
An experiment and numerical simulations analyze low-speed OSC derived XPM-induced phase noise penalty in 100G-WDM systems. WDM transmission performance exhibits signal bit-pattern dependence on OSC, which is due to deterioration in SD-FEC performance.