Optical low coherence reflectometer using [3/spl times/3] fiber coupler

This letter reports that a high-sensitivity OLCR incorporating a balanced detection scheme can be constructed using only one [3/spl times/3] fiber coupler, instead of a cascade connection of a few [2/spl times/2] fiber couplers. This is because two ports on the input side of the coupler can be used to perform balanced detection. A shot-noise limited sensitivity of -152 dB could be achieved without paying special attention to reducing reflection at the local oscillator port.<>