Self-Enclosed All-Fiber In-Line Etalon Strain Sensor Micromachined by 157-nm Laser Pulses

An in-line all-fiber etalon, formed by a self-enclosed Fabry-Perot cavity inside an optical fiber fabricated by using 157-nm laser micromachining, is first demonstrated in this paper. This etalon has almost perfect sensor characteristics, such as excellent interferometric fringe contrast of up to ~30 dB, low thermal cross-sensitivity, great potential to realize mass-production with good reproducibility, low cost, super capability to operate in harsh environments, etc. The static, quasi-static, and dynamic strain characteristics of the etalon sensor are investigated, which prove that such an etalon could meet versatile applications for strain measurement.