Industrial Technology Research Institute

Foci Fiber Optic Communications, Inc.

K Roger Lee

Song-Fure Lin

Chien-Hsiung Chiu

Yen-Zen Lee

Yuh-Lin Cheng

Jing-Yuan Lin

An optical circulator having reduced size and low polarization mode dispersion is disclosed. A transparent optical circulator comprises a first birefringent crystal, a first pair of Faraday polarization rotators having two Faraday polarization rotators aligned in parallel with the propagation direction of an optical signal, a second birefringent crystal, a second pair of Faraday polarization rotators similar to the first pair of Faraday polarization rotators, and a third birefringent crystal. The optical circulator with a reflector or an input/output device and the Faraday rotators together reduce the total size of the circulator, increase the number of input/output ports, and improve the propagation quality of the optical signal by decreasing the polarization mode dispersion. A reflective optical circulator is also presented.

Optical circulator

An optical isolator is placed in the path of an input optical fiber and an output optical fiber, the optical isolator comprises: a first GRIN lens for receiving rays emitted from the input optical fiber and converging into parallel rays; a first birefringent crystal wedge for splitting the parallel rays into a first ray polarized along the birefringent crystal's optical axis and a second ray polarized perpendicularly to the optical axis; a second birefringent crystal wedge for recombining the first ray and the second ray wherein at least one of the first birefringent crystal wedge and the second birefringent crystal wedge comprises a birefringent crystal of YVO.sub.4 ; a second GRIN lens for focusing the recombined rays into the output optical fiber through the second birefringent crystal wedge; a Faraday rotator is mounted between the first birefringent crystal wedge and the second birefringent crystal wedge so that the rays emitted from the input optical fiber can be recombined and focused into the output optical fiber, and the rays reflected from the output optical fiber will be diverged and cannot be refocused into the input optical fiber.

Optical isolator

A system for measuring the strength of fiber optical current in an AC magnetic field by adopting Faraday effect and temperature compensation. In general, the current measurement systems that adopt Faraday effect have the structure including a Faraday element, a polarizer and an analyzer. When a light beam is directed through the Faraday element, the plane of polarization rotates according to the strength of induced magnetic field and Verdet constant in the Faraday element. The rotation affects the optical intensity sensed by the analyzer. The variation on light intensity after passing through the analyzer is converted into an electric current by a optical-electric transducer. But the accuracy of this system this system always affected by the ambient environment, wherein the major factor is the thermal effect of Verdet constant. This invention utilizes thermo-optical sensing device to sense the temperature variation in Faraday element, and furthermore utilizes the sensed variation as means of compensation to regulate the process of current measurement so that will not be affected by ambient temperature.

Growing community of inventors

Tainan Hsien, Taiwan

K Roger Lee