In swept-source optical coherence tomography (SSOCT), the swept-source stimulates system by a series of wavelengths in time sequence; a photo detector then collects all reflected/backscattered light from testing sample as the components of Fourier series. Due to the nature of the SSOCT, the processing in spectral domain can merge multiple swept-sources with different central wavelengths, which greatly increases the resolution of the OCT imaging. In the wavelength probing OCT, a standard broadband SSOCT system is used to extract the internal structure of the sample, and another narrow band light can be used to probe the spectral feature of the sample at the probing wavelength.