| 摘要 |
PROBLEM TO BE SOLVED: To provide a difference delay time correcting device and a primary polarization dispersion correcting device which has no mechanical sliding part such as an optical axis adjustment, is high in speed and high in reliability and can correct group delay time difference. SOLUTION: An a-axis propagation crystal of KNbO3 of a length of 10 cm is used as a double refractive crystal 10, the polarization direction of output light from optical fiber is made to coincide with b-axis and c-axis directions and the bias portion of delay time difference generated by the double refractive crystal 10 is offset each other by a polarization retaining optical fiber 20 of the prescribed length. The double refractive crystal 10 is fixed on a temperature controlling element (Peltier element) 60 and the delay time difference can be controlled from 0 to 8 ps by temperature control.
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