An optical-fiber filter system to narrow a linewidth and to reduce noise fluctuations of an optical beam is provided. The optical-fiber filter system includes an optical fiber having a first end-face and an opposing second end-face, the first end-face and the second end-face setting a fiber length; a fiber Bragg grating having a first reflectivity positioned at the first end-face; and a reflector having a second reflectivity positioned at the second end-face. When the optical beam at a first frequency is coupled from a laser into one of the first end-face or the second end-face, a resonant cavity is established at the first frequency between the fiber Bragg grating and the reflector while Brillouin scattered light shifted from the first frequency within the optical fiber is transmitted through the fiber Bragg grating.

Narrow bandwidth reflectors for reducing stimulated brillouin scattering in optical cavities

There has been a problem that pumping light leaks from a part having a coating at the joint of a double-clad fiber added with a rare earth and a general single-mode fiber, and heat is generated partly from the fiber by this energy thus causing deterioration of the fiber. Deterioration of a fiber due to residual excitation light can be prevented by preventing residual excitation light in a double-clad fiber from exiting to a single-mode fiber, and the reliability is enhanced. Output of oscillation light can be increased because output of excitation light is not limited. Furthermore, a laser display having a high color reproducibility can be achieved by employing a light source combining a fiber laser light source and a wavelength conversion module.

Laser light source device and image display apparatus

PROBLEM TO BE SOLVED: To provide an optical fiber amplifier which extends the transmission distance by compensating for the inter-mode loss difference in a mode multiplex transmission system.SOLUTION: The optical fiber amplifier utilizes the fact that the distribution of optical intensity of signal light is shifted from the position of center in the core more for the signal light of higher order mode. More specifically, the amplification factor for the signal light is increased more when the radial position in the core is separated farther from the position of center in the core, thus increasing the amplification factor for the signal light more for the signal light of higher order mode.

Optical fiber amplifier

There has been a problem that pump light leaks from a portion having a coating at the joint of a double clad fiber added with a rare earth element and a general single mode fiber, and heat is generated partially from the fiber by that energy thus causing deterioration of the fiber. Deterioration of a fiber due to residual exciting light can be prevented by preventing residual exciting light in a double clad fiber from exiting to a single mode fiber, and the reliability is enhanced. Output of oscillation light can be increased because output of exciting light is not limited. Furthermore, a laser display having high color reproducibility can be achieved by employing a light source combining a fiber laser light source and a wavelength conversion module.

Laser light source and image display

The preset invention relates to a transmission-type tunable optical filter which emits a certain wavelength of an element of light in a broadband incident to one end portion of an optical waveguide to an other end portion of the optical waveguide using long period grating instead of an existing Bragg grating According to the present invention, the transmission-type tunable optical filter comprises: the optical waveguide including a cladding, a first core, and a second core which are encircled by the cladding and are separated from each other; a first long period grating formed in a first optical waveguide region wherein the first core of the optical waveguide is located; a first heater located on the optical waveguide in the first optical waveguide region, adjusting an optical period of the first long period grating by a thermo-optic effect; a second long period grating formed in a second waveguide region wherein the second core of the optical waveguide is located; and a second heater located on the optical waveguide in the second optical waveguide region, adjusting an optical period of the second long period grating by the thermo-optic effect The certain wavelength of an element of light in the broadband, which is incident to one end portion of the optical waveguide and is emitted in a core mode of the first core, is converted to be in a cladding mode as the optical period of the first long period grating is adjusted by the first heater The wavelength element, having converted to be in the cladding mode, is converted to be in a core mode of the second core; and is emitted to an other end portion of the optical waveguide as the optical period of the second long period grating is adjusted by the second heater

Tunable optical filter of transmission type using long period gratings

PROBLEM TO BE SOLVED: To provide an optical filter having a new structure and using a long- period grating (LPG) so as to provide in-line band pass filtering for light signals. SOLUTION: In the basic aspect, two LPGs not similar to each other are mounted on an optical fiber transmission line. The first LPG converts the light transmitted in the basic mode or LP01 mode of the optical fiber transmission line into a higher order mode (HOM) of the optical fiber in a wide wavelength range. The signals with converted mode have the mode LPm ,n and then coupled to a second waveguide having different transmission characteristics from those of the first waveguide. The propagation of light in the LPm ,n mode is supported by the second waveguide. The light having the converted mode is transmitted through the second LPG. The signals in a narrow band with selected wavelengths received by the second LPG are again converted into the LP01 mode. The selected narrow band of the LP01 mode efficiently propagates on the rest of the optical fiber transmission line.

Siddharth Ramachandran

Papers

Optical band pass filter using long-period grating