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Long-haul and high-resolution optical time domain reflectometry using superconducting nanowire single-photon detectors.

Zhao Q, Xia L, Wan C, Hu J, Jia T, Gu M, Zhang L, Kang L, Chen J, Zhang X, Wu P - Sci Rep (2015)

Bottom Line: In a 40-minute-long measurement, we obtained a dynamic range of 46.9 dB, corresponding to a maximum sensing distance of 246.8 km, at a two-point resolution of 0.1 km.The time for measuring fiber after 100 km was reduced to one minute, while the fiber end at 217 km was still distinguished well from noise.After reducing the pulse width to 100 ns, the experimental two-point resolution was improved to 20 m while the maximum sensing distance was 209.47 km.

View Article: PubMed Central - PubMed

Affiliation: Research Institute of Superconductor Electronics (RISE), School of Electronic Science and Engineering, Nanjing University, 22 Hankou Road, Nanjing 210093, China.

ABSTRACT
In classical optical time domain reflectometries (OTDRs), for sensing an 200-km-long fiber, the optical pulses launched are as wide as tens of microseconds to get enough signal-to-noise ratio, while it results in a two-point resolution of kilometers. To both reach long sensing distance and sub-kilometer resolution, we demonstrated a long-haul photon-counting OTDR using a superconducting nanowire single-photon detector. In a 40-minute-long measurement, we obtained a dynamic range of 46.9 dB, corresponding to a maximum sensing distance of 246.8 km, at a two-point resolution of 0.1 km. The time for measuring fiber after 100 km was reduced to one minute, while the fiber end at 217 km was still distinguished well from noise. After reducing the pulse width to 100 ns, the experimental two-point resolution was improved to 20 m while the maximum sensing distance was 209.47 km.

No MeSH data available.


Related in: MedlinePlus

ν-OTDR setup using an superconducting nanowire single-photon detector. (a) Schematic setup of a ν-OTDR using an SNSPD. The attenuator was connected for adjusting the power of incident optical pulses to prevent the detector from saturating when the initial fiber was measured. (b) Under-tested fiber. There are two fiber spools fold together on the top right. The fiber spool sat under the blue spool was not connected. (c) The “capacitor-grounded” readout circuit for reading out SNSPD’s outputs.
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f1: ν-OTDR setup using an superconducting nanowire single-photon detector. (a) Schematic setup of a ν-OTDR using an SNSPD. The attenuator was connected for adjusting the power of incident optical pulses to prevent the detector from saturating when the initial fiber was measured. (b) Under-tested fiber. There are two fiber spools fold together on the top right. The fiber spool sat under the blue spool was not connected. (c) The “capacitor-grounded” readout circuit for reading out SNSPD’s outputs.

Mentions: Figure 1a is our long-haul OTDR setup. To realize a high dynamic range, pure optical pulses with high extinction ratio are necessary. To obtain these, we internally modulated a Fabry-Perot (FP) laser diode (Thorlab, FPL1009S) with a squared pulse driver. Although a reverse bias was applied on the diode to force it to be off, we still observed some leakage light. Hence, an acousto-optic modulator (AOM) controlled by a pulse pattern generator (PPG) was connected after the diode to remove the leakage light. But the AOM introduced an additional 3 dB loss. The repetition rate (fr) of the diode was 100 Hz, which was slow enough to ensure that the backscattered signals did not overlap between successive pulses. The widths of optical pulses (tP) were tuned to 1 μs and 100 ns for two independent measurements. The center wavelength of the output light was 1550 nm with a bandwidth of 10 nm, which gave negligible coherent Rayleigh noise. The 10 nm-bandwidth pulses spread in the fiber due to dispersions and thus the two-point resolution was deteriorated in the OTDR measurement with 100 ns optical pulses. However, in the OTDR measurement with 1 μs optical pulses, the pulse spread was only a small portion of the total pulse width. The peak power of the optical pulses was 6 dBm, measured by a calibrated photodiode. When measuring the initial fiber, we attenuated the input pulses or reduced the biased voltage of the diode to lower the power of the backscattered light to prevent the SNSPD from saturating. The optical pulses then entered into six fiber spools (as shown in Fig. 1b) with a total length of 217 km through a circulator. The SNSPD was operated in a liquid helium flow cryostat at a temperature of 2.0 K. Time delays between the SNSPD’s outputs and input optical pulses were collected and analyzed by a time-correlated single-photon detection card (TCSPC, HydraHarp400). The time bin size (tb) was set according to the optical pulse width.


Long-haul and high-resolution optical time domain reflectometry using superconducting nanowire single-photon detectors.

Zhao Q, Xia L, Wan C, Hu J, Jia T, Gu M, Zhang L, Kang L, Chen J, Zhang X, Wu P - Sci Rep (2015)

ν-OTDR setup using an superconducting nanowire single-photon detector. (a) Schematic setup of a ν-OTDR using an SNSPD. The attenuator was connected for adjusting the power of incident optical pulses to prevent the detector from saturating when the initial fiber was measured. (b) Under-tested fiber. There are two fiber spools fold together on the top right. The fiber spool sat under the blue spool was not connected. (c) The “capacitor-grounded” readout circuit for reading out SNSPD’s outputs.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4447072&req=5

f1: ν-OTDR setup using an superconducting nanowire single-photon detector. (a) Schematic setup of a ν-OTDR using an SNSPD. The attenuator was connected for adjusting the power of incident optical pulses to prevent the detector from saturating when the initial fiber was measured. (b) Under-tested fiber. There are two fiber spools fold together on the top right. The fiber spool sat under the blue spool was not connected. (c) The “capacitor-grounded” readout circuit for reading out SNSPD’s outputs.
Mentions: Figure 1a is our long-haul OTDR setup. To realize a high dynamic range, pure optical pulses with high extinction ratio are necessary. To obtain these, we internally modulated a Fabry-Perot (FP) laser diode (Thorlab, FPL1009S) with a squared pulse driver. Although a reverse bias was applied on the diode to force it to be off, we still observed some leakage light. Hence, an acousto-optic modulator (AOM) controlled by a pulse pattern generator (PPG) was connected after the diode to remove the leakage light. But the AOM introduced an additional 3 dB loss. The repetition rate (fr) of the diode was 100 Hz, which was slow enough to ensure that the backscattered signals did not overlap between successive pulses. The widths of optical pulses (tP) were tuned to 1 μs and 100 ns for two independent measurements. The center wavelength of the output light was 1550 nm with a bandwidth of 10 nm, which gave negligible coherent Rayleigh noise. The 10 nm-bandwidth pulses spread in the fiber due to dispersions and thus the two-point resolution was deteriorated in the OTDR measurement with 100 ns optical pulses. However, in the OTDR measurement with 1 μs optical pulses, the pulse spread was only a small portion of the total pulse width. The peak power of the optical pulses was 6 dBm, measured by a calibrated photodiode. When measuring the initial fiber, we attenuated the input pulses or reduced the biased voltage of the diode to lower the power of the backscattered light to prevent the SNSPD from saturating. The optical pulses then entered into six fiber spools (as shown in Fig. 1b) with a total length of 217 km through a circulator. The SNSPD was operated in a liquid helium flow cryostat at a temperature of 2.0 K. Time delays between the SNSPD’s outputs and input optical pulses were collected and analyzed by a time-correlated single-photon detection card (TCSPC, HydraHarp400). The time bin size (tb) was set according to the optical pulse width.

Bottom Line: In a 40-minute-long measurement, we obtained a dynamic range of 46.9 dB, corresponding to a maximum sensing distance of 246.8 km, at a two-point resolution of 0.1 km.The time for measuring fiber after 100 km was reduced to one minute, while the fiber end at 217 km was still distinguished well from noise.After reducing the pulse width to 100 ns, the experimental two-point resolution was improved to 20 m while the maximum sensing distance was 209.47 km.

View Article: PubMed Central - PubMed

Affiliation: Research Institute of Superconductor Electronics (RISE), School of Electronic Science and Engineering, Nanjing University, 22 Hankou Road, Nanjing 210093, China.

ABSTRACT
In classical optical time domain reflectometries (OTDRs), for sensing an 200-km-long fiber, the optical pulses launched are as wide as tens of microseconds to get enough signal-to-noise ratio, while it results in a two-point resolution of kilometers. To both reach long sensing distance and sub-kilometer resolution, we demonstrated a long-haul photon-counting OTDR using a superconducting nanowire single-photon detector. In a 40-minute-long measurement, we obtained a dynamic range of 46.9 dB, corresponding to a maximum sensing distance of 246.8 km, at a two-point resolution of 0.1 km. The time for measuring fiber after 100 km was reduced to one minute, while the fiber end at 217 km was still distinguished well from noise. After reducing the pulse width to 100 ns, the experimental two-point resolution was improved to 20 m while the maximum sensing distance was 209.47 km.

No MeSH data available.


Related in: MedlinePlus