Tunable narrow-band light source using two optical circulators

We report a tunable narrow-band light source with a spectral width of 0.26/spl plusmn/0.04 nm, a 0-dBm output power, and a reduced background spectrum in the 1.5-μm band, which we have developed for optical low coherence reflectometry. The Rayleigh backscatter signal fluctuations were reduced to within /spl plusmn/0.4 dB by using this source. The source will also be used in a system for measuring optical waveguide circuits. This is because the coherence length is about 1 cm and, by using a fiber-optic depolarizer, the degree of polarization is less than 0.016.