Patent ID: 7336858

Claim:
An in-fiber optical isolator for high-powered operation, all fibers having first and second ends, the isolator comprising: a. a first passive high-birefringent fiber with a 45 degree tilted polarizing Bragg grating, a first end of which is connected to a first end of an active polarization-maintaining high-birefringent double-clad fiber with a glass core doped with Yb or Nb ions, both ends stripped and potted to thereby allow removal of pump and s-polarized signals; b. a low-birefringent fiber with a polarization beat length at the lasing wavelength of approximately 2 cm and having a first end fusion spliced to the second end of said first passive fiber and oriented with the birefringence axes of said low-birefringent fiber and said first passive fiber parallel; c. a first linear array of pairs of block-shaped permanent magnets butted against neighboring magnet pairs in a repelling configuration and adjacent to a second similar magnet array but separated by a gap wherein said low-birefringent fiber can lie and is free to move longitudinally, and wherein the number and size of the magnets are selected to obtain a Faraday rotation of 45 degrees; d. a second passive high-birefringent fiber with a 45 degree tilted polarizing Bragg grating, a first end of which is fusion spliced to the second end of said low birefringent fiber outside of said magnet array, the birefringent axes of said second passive fiber being oriented 45 degrees relative to the birefringent axes of said low-birefringent fiber; and e. a second active fiber having one end connected to a second end of said second passive fiber, both ends being stripped and potted to thereby allow removal of pump and s-polarized signals, whereby backward light transmitted by said second passive fiber will be removed by said first passive fiber forming an isolator.