Transient temperature-induced modulation of the radiation in multichannel fiber waveguides

Transient temperature-induced phase perturbations and modulation of radiation in multichannel fiber waveguides were observed experimentally. A temperature drop of ΔT₀ ~ 10 ^– 2 °C in a two-mode fiber waveguide of 130 m length created a transient temperature field giving rise to a phase shift up to 10π. Complete relaxation of the temperature gradient took 10 ^– 5 s. The results indicated that interference of probe waves in multichannel waveguides can be used in high-precision studies of transient temperature-induced processes.