Fundamental phase noise limit in optical fibres due to temperature fluctuations

Theoretical results are presented for the power and RMS amplitude spectra of phase noise in optical fibres due to thermodynamic temperature fluctuations, including the effects of finite fibre outside diameter and retardation. For a fibre optic Mach–Zehnder interferometer with 20m of 125μm diameter fibre in each arm, the (0–25) kHz phase noise is (5.1–1.3) × 10−7rad RMS/√(Hz) at 1300nm.