An in-fiber optical isolator for high-power operation using two kinds of
fiber, not including the active fiber where laser gain occurs. A
hi-birefringence passive fiber with a tilted Bragg grating is connected
to the active fiber at one end with the connection region stripped and
potted to remove pump and s-polarized signals. The other end of the hi-bi
fiber is fusion spliced to a low-birefringence fiber and oriented so that
the birefringent axes are parallel. The low-bi fiber then passes straight
through a gap in a linear magnetic array calculated to cause a 45 degree
Faraday rotation. The far end of the low-bi fiber is connected to another
hi-birefringence passive fiber with a tilted Bragg grating but with the
birefringent axes of the hi-bi rotated by 45 degrees with respect to
those of the low-bi fiber. Backward light transmitted by the second Bragg
grating will then be removed by the first Bragg grating.