An official website of the United States government
Optical fiber is increasingly used for both communication and distributed sensing of temperature and strain in environmental studies. In this work, we demonstrate the viability of unreinforced fiber tethers (bare fiber) for Raman-based distributed temperature sensing in deep ocean and deep ice environments. High-pressure testing of single-mode and multimode optical fiber showed little to no changes in light attenuation over pressures from atmospheric to 600 bars. Most importantly, the differential attenuation between Stokes and anti-Stokes frequencies, critical for the evaluation of distributed temperature sensing, was shown to be insignificantly affected by fluid pressures over the range of pressures tested for single-mode fiber, and only very slightly affected in multimode fiber. For multimode fiber deployments to ocean depths as great as 6000 m, the effect of pressure-dependent differential attenuation was shown to impact the estimated temperatures by only 0.15 °K. These new results indicate that bare fiber tethers, in addition to use for communication, can be used for distributed temperature or strain in fibers subjected to large depth (pressure) in varying environments such as deep oceans, glaciers and potentially the icy moons of Saturn and Jupiter.
more »
« less
Summit Greenland Temperature Logs
This dataset presents physical parameters (temperature, Stokes and anti-Stokes Raman scattering signals) measured during the emplacement of bare single-mode optical fiber within the Greenland Ice Sheet using the Ice Diver melt probe at Summit Station, Greenland (specifically, at 72.5817 N, 38.4578 W). In addition to Stokes and Anti-Stokes signals, the dataset includes englacial temperature profiles derived via Raman distributed temperature sensing (DTS) at 1 m resolution, from ice depths -50 – 355 m (with 0 m representing the top of the borehole). The Raman backscatter signals (Stokes and Anti-Stokes) were captured by the ULTIMA Single Mode Distributed Temperature System (Silixa Ultima Single Mode interrogator) operating at a source wavelength of 1550 nm. Temperature data represent the first 108 hours of cooling (from June 7 – June 12, 2024) following melt probe entrapment in the ice at a depth of ~350 m. Temperature data were calibrated using a section of 25 m of the unreinforced fiber placed in an insulated controlled temperature bath during deployment. Two external PT-100 temperature probes were placed within the bath above and below the spool of fiber optic cable to monitor calibration bath temperatures. External temperature probes were an average of 1.5±0.2 °C warmer than the fiber optic cable. Data records are contained in three Excel spreadsheets (ice_diver_temperatures, Stokes_ice_diver and Anti_Stokes_ice_diver). The first column represents depth below the ice surface, with time in both standard and Matlab datenum format across the top of the spreadsheet. For additional information contact: Scott Tyler styler@unr.edu; Dale Weinbrenner dpw@apl.washington.edu; Sophie Wensman Sophia.Wensman@dri.edu
more »
« less
- Award ID(s):
- 2019719
- PAR ID:
- 10608373
- Publisher / Repository:
- HydroShare
- Date Published:
- Format(s):
- Medium: X
- Location:
- Summit Greenland
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract The design and construction of a waste rock pile influences water infiltration and may promote the production of contaminated mine drainage. The objective of this project is to evaluate the use of an active fiber optic distributed temperature sensing (aFO‐DTS) protocol to measure infiltration and soil moisture within a flow control layer capping an experimental waste rock pile. Five hundred meters of fiber optic cable were installed in a waste rock pile that is 70 m long, 10 m wide, and was covered with 0.60 m of fine compacted sand and 0.25 m of non‐reactive crushed waste rock. Volumetric water content was assessed by heating the fiber optic cable with 15‐min heat pulses at 15 W/m every 30 min. To test the aFO‐DTS system 14 mm of recharge was applied to the top surface of the waste rock pile over 4 h, simulating a major rain event. The average volumetric water content in the FCL increased from 0.10 to 0.24 over the duration of the test. The volumetric water content measured with aFO‐DTS in the FCL and waste rock was within ±0.06 and ±0.03, respectively, compared with values measured using 96 dielectric soil moisture probes over the same time period. Additional results illustrate how water can be confined within the FCL and monitored through an aFO‐DTS protocol serving as a practical means to measure soil moisture at an industrial capacity.more » « less
-
Hybrid fs/ps coherent anti-Stokes Raman scattering (CARS) is employed to investigate the vibrational temperature evolution of N2 in lean methane flames exposed to pulsed microwave irradiation. Vibrational temperature during and post microwave illumination by a 2 μs, 30 kW peak power, 3.05 GHz pulse is monitored in flames diluted with N2, N2 and CO2 , and N2 and Ar. Electric field strengths inside the microwave cavity are monitored directly using electric field probes. Temperature increases up to 140 K were observed in flames with additional Ar and CO2 dilution, whereas temperature increases by 80 K were observed in mixtures diluted with only N2 . The microwave energy deposition to excited states begins to thermalize over scales of 100 μs, however, equilibrium is not reached before excited combustion products convect out of the probe volume on the order of several 1 ms. Understanding the impact of varying bath gases on microwave interaction, magnitude of temperature rise and thermalization timescales is critical for the development and validation of new kinetic models for applications exhibiting significant degrees of thermal non-equilibrium, such as high-speed reentry flows and plasma-assisted combustion.more » « less
-
Seafloor moorings measuring pressure and temperature were deployed from April to September 2023 at three sites near the route of the fiber optic telecommunications cable that extends offshore of Oliktok Point, Alaska. The raw data data (1 Hertz (Hz) sampling) are processed for hourly estimates of the ocean surface wave conditions, along with average seawater temperature and average depth. The sites were ice-covered from April to July, then mostly open water in August and September. The data were collected to calibrate proxy wave measurements using Distributed Acoustic Sensing (DAS) from the telecommunications cable.more » « less
-
Measurements of ice temperature provide crucial constraints on ice viscosity and the thermodynamic processes occurring within a glacier. However, such measurements are presently limited by a small number of relatively coarse-spatial-resolution borehole records, especially for ice sheets. Here, we advance our understanding of glacier thermodynamics with an exceptionally high-vertical-resolution (~0.65 m), distributed-fiber-optic temperature-sensing profile from a 1043-m borehole drilled to the base of Sermeq Kujalleq (Store Glacier), Greenland. We report substantial but isolated strain heating within interglacial-phase ice at 208 to 242 m depth together with strongly heterogeneous ice deformation in glacial-phase ice below 889 m. We also observe a high-strain interface between glacial- and interglacial-phase ice and a 73-m-thick temperate basal layer, interpreted as locally formed and important for the glacier’s fast motion. These findings demonstrate notable spatial heterogeneity, both vertically and at the catchment scale, in the conditions facilitating the fast motion of marine-terminating glaciers in Greenland.more » « less
