A simple spatial method using a coherent light source and an interferometer is proposed for measuring the group delay time difference between the LP01 and LP11 modes in a dual-mode optical fiber. Experimental results obtained by this method are in good agreement with those obtained by the swept-frequency and pulse methods. Moreover, a group delay time difference of 4 psec is measured. Results suggest that this spatial method can be applied to a short fiber less than 1 m in length and/or small time differences around 1 psec by using a laser diode with a short coherence length.
© 1980 Optical Society of America
Original Manuscript: July 18, 1979
Published: May 1, 1980
Nori Shibata, Mitsuhiro Tateda, Shigeyuki Seikai, and Naoya Uchida, "Spatial technique for measuring modal delay differences in a dual-mode optical fiber," Appl. Opt. 19, 1489-1492 (1980)