Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ultimate capacity limit of a multi-span link with phase-insensitive
  amplification   The Shannon capacity of a point-to-point link with an optimised configuration
of optical amplifiers is compared with general detection strategies permitted
by quantum mechanics. Results suggest that the primary application area of
receivers based on such strategies may be unamplified short-distance links or
free-space optical communication

5
The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph
22
The categories of this paper are: chao-dyn
0
The categories of this paper are: hep-ph
1
The categories of this paper are: cs
10
The categories of this paper are: q-bio
31
The categories of this paper are: ao-sci
6
The categories of this paper are: astro-ph
11
The categories of this paper are: hep-lat
25
The categories of this paper are: patt-sol
28
The categories of this paper are: alg-geom
32
The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
8
The categories of this paper are: hep-ex
17
The categories of this paper are: q-fin
7
The categories of this paper are: hep-th