PROBLEM TO BE SOLVED: To delete photon excessive noise in a light source of a short coherence such as a wide-band super-fluorescent fiber and a super-light-emitting diode. SOLUTION: Beams from a light source 11 are divided into a plurality of components for a light source signal, whereby photon noise or beat noise is divided, similar to light intensity. Each component passes through separate optical paths 19, 21 having a characteristic time delay which is longer than a coherence time of the light source and is recoupled by a polarizing beam splitting coupler 23 at an end part on an output side prior to detection. As a result, strength of a signal is restored to the original, while a level of a total amount of beat noise is lowered. The optical paths 19, 21 are polarized light- keeping fibers, having a different lengths.
METHOD AND DEVICE FOR DELETING PHOTON ACCESS NOISE OF LIGHT SOURCE OF SHORT COHERENCE LENGTH