Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 217 km long distance photon-counting optical time-domain reflectometry
  based on ultra-low noise up-conversion single photon detector   We demonstrate a photon-counting optical time-domain reflectometry with 42.19
dB dynamic range using an ultra-low noise up-conversion single photon detector.
By employing the long wave pump technique and a volume Bragg grating, we reduce
the noise of our up-conversion single photon detector, and achieve a noise
equivalent power of -139.7 dBm/sqrt(Hz). We perform the OTDR experiments using
a fiber of length 216.95 km, and show that our system can identify defects
along the entire fiber length with a distance resolution better than 10 cm in a
measurement time of 13 minutes.

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The categories of this paper are: dg-ga
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The categories of this paper are: astro-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: supr-con
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The categories of this paper are: hep-th
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The categories of this paper are: solv-int
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The categories of this paper are: econ
1
The categories of this paper are: cs
33
The categories of this paper are: plasm-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: funct-an
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The categories of this paper are: atom-ph
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The categories of this paper are: stat
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The categories of this paper are: math-ph