Fig. 1. Optical fiber ultrasonic sensing system. (a) Sensors and principle of ultrasonic detection; (b) optical fiber sensing system

Fig. 2. Calculated noises versus input optical power (or photocurrent)

Fig. 3. Measured sensor system noise n_0,beat signal power P_rf,and frequency noise Δf_noise versus optical power P_opt and photocurrent I_dc. (a) System noise n_0;(b) beat signal power P_rf;(c) frequency noise Δf_noise

Fig. 4. Schematic of fiber-based photoacoustic imaging system

Fig. 5. Photoacoustic microscopic results of a mouse ear with different input optical powers. (a) 15.7 mW; (b) 10.5 mW；(c) 1.7 mW; (d) B-scan results along the dotted lines