A high pressure swivel includes an inner and an outer wall. The front end includes a photodetector and an array of parallel conversion circuits, each including an activation switch, a charge amplifier and an Analog to Digital Converter. An insulating film is formed thereon, and a second transparent conductive film is patterned to form a pixel electrode. The improvements can be used alone or together. The light response of the medium corresponding to different wavelength of the incident light and different pressure values during measurements. Various other apparatuses, assemblies, systems, methods, etc.