  Rapid and direct monitoring of dissolved gases in liquids under strong
electromagnetic interference is very important. Electronic gas sensors that can
be placed into liquids are difficult to work reliably under strong
electromagnetic fields. The existing optical monitoring techniques for
dissolved gases all require gas-liquid separation, and are conducted in gas
phase, which have poor timeliness. In this paper, a dissolved gas monitoring
probe without liquid-gas separation under strong electromagnetic interference
is proposed. We take transformer oil-dissolved acetylene monitoring as an
example, an oil-core photonic crystal fiber photothermal interferometry probe
is proposed and demonstrates the feasibility of trace oil-dissolved acetylene
directly monitoring without oil-gas separation. The minimum detection limit
reaches 1.4 ppm, and the response time is about 70 minutes. Due to the good
insulation performance and the compact size, the all-fiber probe provides
applicability to be placed into transformer oil and perform on-line monitoring
under strong electromagnetic interference.
