Principle and theoretical analysis of all-fiber circular polarizers

A new suggestion of making chiral fiber gratings and all-fiber circular polarizers by spinning strain-induced high birefringence fibers was presented. By means of coupled-mode theory, it is shown that a circular polarizer might be achieved by using a spun Bow-Tie fiber or Panda fiber with short pitches of less than one millimeter. Unlike the special chiral fibers previously mentioned, these strain-induced high birefringence fibers are commercially available and are easy to be spliced with common fibers. The coupled-mode analysis also reveals the scheme of polarization-selectivity between coupled modes and the necessary conditions for achieving polarizers in these kinds of chiral fiber gratings. A numerical simulation was done on a spun Panda fiber, and it is shown that in a right-handed rotating birefringent fiber with a numerical aperture of 0.186 5, a beat length of 125 millimeter, a rotation pitch of 0375 millimeter and a fiber length of 332 millimeter, a left-circular polarization light would output at the wavelength of 155 micron.