Speaker
Description
Fibre-based frequency references offer a robust and cost-effective alternative to cavity-stabilised lasers for precision interferometry, including for space-based laser interferometer links. However, the long fibre coils used in these systems are highly sensitive to temperature fluctuations, necessitating effective thermal isolation. We have designed a multi-layer in-vacuum thermal shield to meet the thermal attenuation requirements of GRACE-like missions. However, the residual temperature fluctuations within the shield fall below the resolution of conventional thermistor probes.
To address this, we leverage the temperature sensitivity of the fibre coil itself to characterise the thermal shield's attenuation performance under heater excitation. A heterodyne Mach-Zehnder interferometer measures temperature-induced phase shifts in a 1 km fibre coil with a measured optical gain of 55 rad/mK. This fibre-optic sensing approach enables high-sensitivity temperature measurement without the use of separate electronic sensors and the parasitic thermal paths introduced by electrical wiring.
We developed an analytic cascaded RC thermal circuit model to predict the shield’s thermal response. Preliminary in-air measurements using a thermistor showed excellent agreement with this model, but the data became dominated by the thermistor’s own parasitic thermal short. We have now integrated the full fibre-optic system and characterisation measurements are ongoing to determine the effective precision, retaining the thermistor as a benchmark. Our goal is to remove the thermistor and its thermal short, relying solely on the fibre coil for temperature monitoring. This self-sensing approach will enable experimental verification of the shield's attenuation performance across the mission-relevant frequency band of 0.1mHz to 100mHz.
| I am the presenting author | Yes |
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