OPTICAL FIBER SENSOR LIGHT SOURCE

PROBLEM TO BE SOLVED: To use the total quantity of light outputted from a super-radiance diode for detection, and improve utility of the quantity of output light by rotating a specified angle of a polarization plane of a submode out of a luminous flux generated by the super-radiance diode, and feeding back the submode to the diode. SOLUTION: A luminous flux composed of a linearly polarized components TE mode and TM mode outputted from a super-radiance diode 1 is converged by a collimator 2 and enters an end surface of a polarization plane maintaining optical fiber 31. The TE mode which is the main mode of the incident luminous flux is outputted from an end surface of a polarization plane maintaining optical fiber 31' through a polarization beam splitter 3. The TM mode which is a submode out of the incident polarized luminous flux is branched into a polarization plane maintaining fiber 32' via the beam splitter 3. The polarization plane of the branched TM mode is rotated 90 degrees by an isolator 5. The TM mode is outputted from an end surface of the fiber 32', converged by a collimator 2', fed back to the diode 1, and combined with the TE mode.