Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Coupled-Channel Enhanced SSFM for Digital Backpropagation in WDM Systems   A novel technique for digital backpropagation (DBP) in wavelength-division
multiplexing systems is introduced and shown, by simulations, to outperform
existing DBP techniques for approximately the same complexity.

17
The categories of this paper are: q-fin
16
The categories of this paper are: stat
34
The categories of this paper are: chem-ph
25
The categories of this paper are: patt-sol
9
The categories of this paper are: nlin
36
The categories of this paper are: cmp-lg
30
The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
6
The categories of this paper are: astro-ph
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
15
The categories of this paper are: nucl-ex
23
The categories of this paper are: solv-int
24
The categories of this paper are: dg-ga
33
The categories of this paper are: plasm-ph
3
The categories of this paper are: physics