On-site water level measurement method based on wavelength division multiplexing for harsh environments in nuclear power plants

Lee, Hoon-Keun; Choo, Jaeyul; Shin, Gangsig; Kim, Sung-Man

doi:10.1016/j.net.2020.05.005

Cited by 11 publications

(23 citation statements)

References 14 publications

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“…Based on Equation (1), the power coefficients for the Fresnel reflection are approximately −26.3 dB (0.23% power reflection) in the water (

) and −14.7 dB (3.36% power reflection) in the air (

), respectively. The power difference ( ∆P) between those Fresnel reflections is approximately 11.6 dB, which is well matched with the measurement results [ 16 ].…”

Section: Theoretical Model For Remote Sensingsupporting

confidence: 84%

“…The sensing unit is a commercial fiber-optic patch-cord including standard SC/PC type connectors, which is based on fluorine-doped silica fiber. In the simulation, we assumed that the refractive index of fiber (

) is 1.4492, air (

) is 1.0002739, and water (

) is 1.3152, respectively [ 16 ]. Note that we considered the refractive indices to be constant within the C-band as those are nearly independent of the wavelength and temperature [ 15 ].…”

Section: Theoretical Model For Remote Sensingmentioning

confidence: 99%

“…The AWG has relatively low (e.g., <5 dB) insertion loss, which does not visibly vary for wavelengths (i.e., channels). Thus, the intensity of the received optical signal at the reflectometer can be expressed as Equation (2) without taking the RBS effects into consideration [ 15 , 16 ],

where

and

correspond to the electrical field of ASE and the AWG transfer function, respectively. The ASE light can be modeled as uniformly-spaced spectral components that have constant amplitude and uniformly distributed random phase within [0 ~ 2π].…”

Section: Theoretical Model For Remote Sensingmentioning

confidence: 99%

“…In the simulation, we select

, and

to be 1.5 dB, 4.5 dB, 1 dB, 0.2 dB/km, and −56 dB, respectively. These values are based on the previous measurement [ 16 ].…”

Section: Theoretical Model For Remote Sensingmentioning

confidence: 99%

“…Recently, we proposed and demonstrated a simple all-optical water level monitoring method based on the use of spectrum-sliced amplified spontaneous emission (ASE) light, for its application in nuclear power plant safety [ 15 , 16 ]. This method provides a simple way of multichannel sensing, at a high spatial resolution for low insertion loss, having great robustness to external temperature changes.…”

Section: Introductionmentioning

confidence: 99%

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Long-Reach DWDM-Passive Optical Fiber Sensor Network for Water Level Monitoring of Spent Fuel Pool in Nuclear Power Plant

Lee

Choo

Shin

et al. 2020

Sensors

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This paper presents a passive optical fiber sensor network based on the dense wavelength division multiplexing (DWDM) to remotely monitor the water level of the spent fuel pool in nuclear power plants. In states of emergency, such as a tsunami, safety information must be secured for rapid response, in spite of all power losses in the plant. We consider the proposed passive sensor network to be one of the best solutions that is able to provide the remote (more than tens of kilometers) monitoring station with the highly reliable on-site information. The principle of water level measurement is based on the change of Fresnel reflection power coefficient at sensing units, which are installed according to the water levels in a row. The sensing units that play the role of reflector and modulator at the same time are connected to an arrayed waveguide grating (AWG) for DWDM. By measuring the spectrum of the optical signal transferred from the sensing units, the water level can be determined in real-time. However, in the remote sensing, the system performance can be seriously degraded due to the Rayleigh Back-Scattering (RBS) of the seeded amplified spontaneous emission (ASE) light that is induced at the fiber-optic link. As such, we investigate the effect of RBS on the remote (more than tens of kilometers) sensing performance of the proposed network. Following the theoretical analysis, we propose a simple network configuration to overcome the RBS issue by utilizing two different transmission paths: one for downstream of the ASE seed light, and the other for upstream of the optical signals coming from the sensing units. Based on the proposed configuration, the maximum sensing distance can be increased up to 42.5 km without the support of any optical amplifier.

show abstract

“…Based on Equation (1), the power coefficients for the Fresnel reflection are approximately −26.3 dB (0.23% power reflection) in the water (

) and −14.7 dB (3.36% power reflection) in the air (

), respectively. The power difference ( ∆P) between those Fresnel reflections is approximately 11.6 dB, which is well matched with the measurement results [ 16 ].…”

Section: Theoretical Model For Remote Sensingsupporting

confidence: 84%

) is 1.4492, air (

) is 1.0002739, and water (

) is 1.3152, respectively [ 16 ]. Note that we considered the refractive indices to be constant within the C-band as those are nearly independent of the wavelength and temperature [ 15 ].…”

Section: Theoretical Model For Remote Sensingmentioning

confidence: 99%

where

and

Section: Theoretical Model For Remote Sensingmentioning

confidence: 99%

“…In the simulation, we select

, and

to be 1.5 dB, 4.5 dB, 1 dB, 0.2 dB/km, and −56 dB, respectively. These values are based on the previous measurement [ 16 ].…”

Section: Theoretical Model For Remote Sensingmentioning

confidence: 99%

Section: Introductionmentioning