An optoacoustic apparatus comprising: a first light source capable of generating pulses of light at a first predominant wavelength; a second light source capable of generating pulses of light at a second predominant wavelength; an internal light path comprising: first and second electrically controlled optical attenuators (3902, 3912) for the first and second light source, respectively; first and second light sync detectors for the first and second light source, respectively; and a combiner, to direct at least a portion of the pulses of each of the first and second light sources along a common path; a common light output connection terminal; an external light path connected to the internal light path via the common light output connection terminal, the external light path comprising: a plurality of optical fibers having a first end formed into at least one fiber bundle providing an input, and a second end terminating in a handheld probe; and at least one optical window at the distal end of the handheld probe, the handheld probe further comprising an array of ultrasound transducers covered by an acoustic lens at the distal end; a power meter calibrated to determine power at the first and second predominant wavelength, the power meter adapted to measure power at the first predominant wavelength in proximity to the at least one optical window after the first light sync is detected, and to measure power at the second predominant wavelength in proximity to the at least one optical window after the second light sync is detected; and the apparatus having a calibration mode wherein the apparatus is adapted to electrically attenuate the first optical attenuator when the power measured by the power meter at the first predominant wavelength in proximity to the at least one optical window after the first light sync is detected is above a first level, and to electrically attenuate the second optical attenuator when the power measured by the power meter at the second predominant wavelength in proximity to the at least one optical window after the second light sync is detected is above a second level. a first light source capable of generating pulses of light at a first predominant wavelength; a second light source capable of generating pulses of light at a second predominant wavelength; an internal light path comprising: first and second electrically controlled optical attenuators (3902, 3912) for the first and second light source, respectively; first and second light sync detectors for the first and second light source, respectively; and a combiner, to direct at least a portion of the pulses of each of the first and second light sources along a common path; a common light output connection terminal; first and second electrically controlled optical attenuators (3902, 3912) for the first and second light source, respectively; first and second light sync detectors for the first and second light source, respectively; and a combiner, to direct at least a portion of the pulses of each of the first and second light sources along a common path; a common light output connection terminal; an external light path connected to the internal light path via the common light output connection terminal, the external light path comprising: a plurality of optical fibers having a first end formed into at least one fiber bundle providing an input, and a second end terminating in a handheld probe; and at least one optical window at the distal end of the handheld probe, the handheld probe further comprising an array of ultrasound transducers covered by an acoustic lens at the distal end; a plurality of optical fibers having a first end formed into at least one fiber bundle providing an input, and a second end terminating in a handheld probe; and at least one optical window at the distal end of the handheld probe, the handheld probe further comprising an array of ultrasound transducers covered by an acoustic lens at the distal end; a power meter calibrated to determine power at the first and second predominant wavelength, the power meter adapted to measure power at the first predominant wavelength in proximity to the at least one optical window after the first light sync is detected, and to measure power at the second predominant wavelength in proximity to the at least one optical window after the second light sync is detected; and the apparatus having a calibration mode wherein the apparatus is adapted to electrically attenuate the first optical attenuator when the power measured by the power meter at the first predominant wavelength in proximity to the at least one optical window after the first light sync is detected is above a first level, and to electrically attenuate the second optical attenuator when the power measured by the power meter at the second predominant wavelength in proximity to the at least one optical window after the second light sync is detected is above a second level.