We constructed a lens-free in-line optical isolator by embedding an isolator chip in a thermally expanded core (TEC) fiber without complicated optical alignment. The chip consists of two pairs of rutile wedges and garnet plates. We fabricated the TEC fibers by heating a single-mode fiber with a 200-μm outer diameter; low loss and a spot diameter as large as 49 μm were successfully obtained. The fabricated isolator has excellent optical properties, an insertion loss of 0.45 dB, and an isolation of more than 50 dB at a 1.55-μm wavelength, which confirms the usefulness of the integration techniques.
© 1999 Optical Society of America
(060.2340) Fiber optics and optical communications : Fiber optics components
(130.3120) Integrated optics : Integrated optics devices
(230.2240) Optical devices : Faraday effect
(230.3240) Optical devices : Isolators
T. Sato, J. Sun, R. Kasahara, and S. Kawakami, "Lens-free in-line optical isolators," Opt. Lett. 24, 1337-1339 (1999)