Optical detection system for a gas turbine engine combustion assembly

A gas turbine engine comprising:

• an outer case extending circumferentially about an axial centerline of the gas turbine engine;
• a combustor disposed radially inward of the outer case, the combustor forming a combustion chamber;
• a fuel injector extending through the outer case and the combustor, the fuel injector configured to direct a fuel into the combustion chamber for combustion within the combustion chamber;
• a monochromator mounted to the outer case, the monochromator having a first line-of-sight to the combustion chamber;
• and
• a photodetector assembly disposed within the fuel injector, the photodetector assembly having a second line-of-sight to the monochromator.

A combustion assembly for a gas turbine engine, the combustion assembly comprising:

• a combustor forming a combustion chamber;
• a plurality of fuel injectors disposed within the combustor, each fuel injector of the plurality of fuel injectors including a housing;
• a volume phase holographic grating (VPHG) disposed outside the combustion chamber, the VPHG configured to receive light from the combustion chamber;
• and
• a plurality of photodetector assemblies, each photodetector assembly of the plurality of photodetector assemblies at the housing of a respective fuel injector of the plurality of fuel injectors, at least one of the plurality of photodetector assemblies having a line-of-sight to the VPHG.