Rapidly-tunable narrowband light source with symmetrical crossing configuration for low coherence reflectometry

A rapidly-tunable narrowband light source is constructed for jaggedness-free low coherence reflectometry. A double-path tunable bandpass filter module whose two passbands automatically agree during wavelength tuning is used in the source. The source can emit narrowband low coherence light with an FWHM of 0.57 nm, a power of >0 dBm, and a suppressed background spectrum, at wavelengths from 1534 to 1560 nm. The entire wavelength range can be swept within 10 ms. The rapid tunability leads to both a reduction in the time required to perform the wavelength averaging of Rayleigh backscatter signals, and an enlargement of fine structures in the mean reflection profiles