DSP complexity of mode-division multiplexed receivers

Abstract

The complexities of common equalizer schemes are analytically analyzed in this paper in terms of complex multiplications per bit. Based on this approach we compare the complexity of mode-division multiplexed digital signal processing algorithms with different numbers of multiplexed modes in terms of modal dispersion and distance. It is found that training symbol based equalizers have significantly lower complexity compared to blind approaches for long-haul transmission. Among the training symbol based schemes, OFDM requires the lowest complexity for crosstalk compensation in a mode-division multiplexed receiver. The main challenge for training symbol based schemes is the additional overhead required to compensate modal crosstalk, which increases the data rate. In order to achieve 2000 km transmission, the effective modal dispersion must therefore be below 6 ps/km when the OFDM specific overhead is limited to 10%. It is concluded that for few mode transmission systems the reduction of modal delay is crucial to enable long-haul performance.

Low Computational Complexity Mode Division Multiplexed OFDM Transmission over 130 km of Few Mode Fiber

“…The equalizer complexity of this 337.5-Gb/s system can be calculated as described in [5]. The OFDM requires 7.7 complex multiplications per bit and one tap equalization.…”

“…In [5,6] we analyzed some of the most common blind and training symbol (TS) based equalizers, time domain, hybrid time/frequency domain (FDE/TDE), TS based frequency domain equalizer (FDE), orthogonal frequency division multiplexing (OFDM) and hybrid FDE/OFDM. Among these different equalization structures, OFDM gives the least complexity.…”

Capacity Enhancement of Few-Mode Fiber Transmission Systems Impaired by Mode-Dependent Loss

“…Furthermore, we also notice that for low SNRs the capacity gain provided by MS is very low. This is due to the impact of noise that dominates the effect of MDL (given by the different eigenvalues λ i 's) in the capacity expression of Equation (5). However, for high SNRs the gain provided by MS becomes more important.…”

“…In our work, we are interested in FMF sysytems. The impact of DMGD and unitary modal coupling in FMFs is very important to determine the MIMO equalizer complexity at the receiver [4,5]. Moreover, in FMF systems, propagating modes can also be affected by a non-unitary cross-talk known as mode-dependent loss (MDL) that can be either distributed through the fiber or local at the insertion of optical components.…”

Expressions for the nonlinear transmission performance of multi-mode optical fiber

“…Combining analytical result of the potential ISD predicted by the approach of this paper with calculations of digital signal processing complexity [40] should enable fibers to be designed to which optimize the tradeoff between signal processing complexity (proportional to DGD) and nonlinearity without the need for extensive numerical simulations. Since our preliminary results suggest that the system reach, amplifier noise figure etc.…”