Phase-shifted helical long-period fiber grating and its characterization by using the microscopic imaging method.

We demonstrate a simple and robust method to write a phase-shifted helical long-period fiber grating (HLPG), where an equivalent phase-shift is formed by changing the local period of the grating during the fabrication process. Furthermore, we propose and demonstrate a simple method to characterize the phase-shift formed in a HLPG, which is realized by… CONTINUE READING