Temperature control of a PM ring fiber cavity for long-term laser frequency stabilization

We present a high performance, low cost, simple setup for long term temperature stabilization of a 2 m optical fiber ring cavity for laser frequency stabilization applications thanks to birefringence of the fiber and its dependence on temperature. The fiber temperature is controlled, at millisecond time scale by LED (light emissive diode) illumination. This allows reaching a temperature stability of 0.1 μK at 100 seconds for the 2 m long PM ring fiber cavity. This is a reduction of the fiber temperature by a factor of 2×10^5 (from 20 mK to 0.1 μK) and 5×10^5 (from 300 mK to 0.6 μK), at 100 seconds and at 10^5 seconds, respectively, with respect to the ambient temperature variations.