(a) Schematic of the three-wavelength OR-PAM system. Amp: amplifier, BS: beam splitter R/T: 10/90, DM: dichroic mirror 550 nm long-pass, DAQ: data Acquisition, FC: fiber coupler, HWP: half-wave plate, LPF: 540 nm long-pass filter, MMF: multi-mode fiber, PBS: polarizing beam splitter, PM-SMF: polarization-maintain single-mode fiber, SPF: 570 nm short-pass filter, UST: ultrasonic transducer, NDF: neutral density filter, WT: water tank (b) The time delays among different pulses measured by a photodiode.