Abstract: The FIFO device includes an MCF, a first lens having a first optical axis parallel to a center axis of the MCF, a group of second lenses including the same number of second lenses having a second optical axis parallel to the first optical axis as cores of the MCF, and a group of single-core optical fibers including the same number of single-core optical fibers as the second lenses. An end face of each single-core optical fiber is obliquely polished so as to incline in a predetermined inclination direction with respect to a plane orthogonal to the center axis by a predetermined polishing angle. Oblique polishing directions of surrounding single-core optical fibers are set so that the corresponding second lenses are positioned closer to the first optical axis or to the first lens compared to their positions at the time when the surrounding single-core optical fibers are not obliquely polished.

Abstract: An optical filter device includes: a first multi-core optical fiber including a plurality of first cores; a first lens; an optical filter which is rotated by a rotation angle about a rotation axis; a second lens; and an optical fiber including cores which the emission light beams from the second lens enter. When directions directed from a reference axis toward one side and another side with respect to the reference axis along an orthogonal axis orthogonal to an optical axis and the reference axis are defined as first and second orthogonal directions, respectively, a circumferential orientation of the first multi-core optical fiber is set so that a separation distance is minimized. The separation distance is a sum of distances from the reference axis to first cores that are most separated away from the reference axis in the first and second orthogonal directions, respectively.

Abstract: A slope gain equalizer that corrects a slope of a gain characteristic of an optical signal in a predetermined wavelength bandwidth. An interference filter, which allows insertion losses in a predetermined wavelength region to be inclined in opposite directions between a transmitting direction and a reflecting direction from a short wavelength side to a long wavelength side, is arranged between a dual-core fiber collimator and a single-core fiber collimator facing each other on an optical axis. An optical signal of a predetermined bandwidth inputted from a first or second optical fiber held by the dual-core fiber collimator is reflected by the interference filter and outputted from the second or the first optical fiber. An optical signal inputted from a third optical fiber held by the first optical fiber or the single-core fiber collimator is transmitted through the interference filter and outputted from the third or the first optical fiber.

Abstract: A preform for optical fiber made of a quartz glass sintered body which is made from quartz glass powder as a main raw material, in which at least a portion of the quartz glass sintered body is an opaque body, the opaque body has a visible light transmittance of 90% or less at a length of 5 mm or less in one direction, and the opaque body has a bulk density of 2.1 g/cm3 or more, or the opaque body has a visible light transmittance of 90% or less at a length of 5 mm or less in one direction, and the opaque body has an open porosity of 3.5% or less.

Abstract: An interference filter module comprises two optical fiber collimators arranged on an optical axis so as to be opposed to each other, interference filters, and a casing including a main body portion and filter holding portions to be mounted into the main body portion, which are configured to hold the interference filters. Two interference filters including a kth filter when counted from a front end and a k-th filter when counted from a rear end are determined as a k-th set. The two interference filters of the k-th set are accommodated in two filter holding portions, each of which is a k-th holding portion when counted from the front end and the rear end, respectively. The two filter holding portions have rotation axes in directions orthogonal to a fore-and-aft direction and are rotatably held by the casing. The rotation axes of the filter holding portions are orthogonal to each other.

Abstract: A slope gain equalizer that corrects a slope of a gain characteristic of an optical signal in a predetermined wavelength bandwidth. An interference filter, which allows insertion losses in a predetermined wavelength region to be inclined in opposite directions between a transmitting direction and a reflecting direction from a short wavelength side to a long wavelength side, is arranged between a dual-core fiber collimator and a single-core fiber collimator facing each other on an optical axis. An optical signal of a predetermined bandwidth inputted from a first or second optical fiber held by the dual-core fiber collimator is reflected by the interference filter and outputted from the second or the first optical fiber. An optical signal inputted from a third optical fiber held by the first optical fiber or the single-core fiber collimator is transmitted through the interference filter and outputted from the third or the first optical fiber.

Abstract: An optical fiber feedthrough includes a tubular-shaped sleeve and an elastic tube. The sleeve includes a through hole extending in an axial direction and is mountable to a package such that an end portion thereof on one side is located on an inner side of the package and an end portion thereof on an other side is located on an outer side of the package. The elastic tube includes an insertion portion entering the inside of the through hole from an outer end portion being an end portion on the other side of the through hole, and a projection portion projecting to the outside from the outer end portion. An optical fiber is insertable into the through hole and the elastic tube, and an outer peripheral surface of the elastic tube and an inner peripheral surface of the through hole are fixed to each other with an adhesive.

Abstract: In a wavelength selective filter, an optical fiber collimator, an interference filter, and a reflective plate are arranged in this order from front to rear along a z-axis. The collimator has a collimator lens disposed on the rear side of an optical fiber that is opened. The interference filter includes light incident and emitting surfaces, opposed with their xy-planes rotated about a y-axis at a predetermined rotation angle. The reflective plate has a front reflective surface having a normal direction along a z-axis direction, and reflects, toward the front, light incident from the front through the interference filter, to be incident onto the interference filter. The optical fiber collimator causes the input light propagating through the optical fiber from the front to be incident onto the interference filter, and converges the reflected light transmitted through the interference filter to the optical fiber and outputs the light.

Abstract: Provided is an optical module comprising a substrate, a holder, and a spacer. An optical waveguide is formed in/on the substrate and end parts thereof are protruding from one surface of the substrate. The holder holds an optical fiber and exposes one end part of the optical fiber in such a manner that the one end part of the optical fiber can be optically connected to the end parts of the optical waveguide at a side of one surface of the holder. The spacer is held the one surface of the substrate and the one surface of the holder.

Abstract: Provided is an optical module comprising a substrate, a holder, and a spacer. An optical waveguide is formed in/on the substrate and end parts thereof are protruding from one surface of the substrate. The holder holds an optical fiber and exposes one end part of the optical fiber in such a manner that the one end part of the optical fiber can be optically connected to the end parts of the optical waveguide at a side of one surface of the holder. The spacer is held the one surface of the substrate and the one surface of the holder.

Abstract: An interference filter module comprises two optical fiber collimators arranged on an optical axis so as to be opposed to each other, interference filters, and a casing including a main body portion and filter holding portions to be mounted into the main body portion, which are configured to hold the interference filters. Two interference filters including a kth filter when counted from a front end and a k-th filter when counted from a rear end are determined as a k-th set. The two interference filters of the k-th set are accommodated in two filter holding portions, each of which is a k-th holding portion when counted from the front end and the rear end, respectively. The two filter holding portions have rotation axes in directions orthogonal to a fore-and-aft direction and are rotatably held by the casing. The rotation axes of the filter holding portions are orthogonal to each other.

Abstract: An optical multiplexer/demultiplexer includes: first to n-th demultiplexed light input/output portions; a multiplexed light input/output portion; second to n-th interference film filters; and first to n?1-th mirrors. The first to n-th demultiplexed light input/output portions are disposed on a single plane and correspond to light having a single wavelength. The second to n-th interference film filters are disposed in front of the second to n-th demultiplexed light input/output portions. The first to n?1-th mirrors are disposed in front of the first demultiplexed light input/output portion and in front of the n?1-th interference film filters. Light from the first demultiplexed light input/output portion strikes the first to n?1-th mirrors and the second to n-th interference film filters and is input to the multiplexed light input/output portion. Light output from the multiplexed light input/output portion strikes the second to n-th interference film filters and first to n?1-th mirrors.

Abstract: An optical device including a Faraday rotator, wherein the Faraday rotator includes a Faraday element 31 made of a magnetooptical material 34, two permanent magnets 35, and an electromagnet 20a, with a direction of travel of light as a front-rear direction, the Faraday element includes light incident/emission surfaces in front and rear, and surfaces parallel to each other in left and right, the plate-shaped permanent magnets are attached to each of left and right side surfaces of the Faraday element such that different magnetic poles are opposed to each other, and the permanent magnets are configured to apply a permanent magnetic field to the Faraday element in one direction of a left direction and a right direction, a shaft part 10 that holds the Faraday element, attached with the permanent magnets, over an entire length in the front-rear direction is included, the electromagnet is configured including a coil made by winding a conductor 21 around a periphery of the shaft part with the front-rear direction as

Abstract: An optical multiplexer/demultiplexer includes: first to n-th demultiplexed light input/output portions; a multiplexed light input/output portion; second to n-th interference film filters; and first to n?1-th mirrors. The first to n-th demultiplexed light input/output portions are disposed on a single plane and correspond to light having a single wavelength. The second to n-th interference film filters are disposed in front of the second to n-th demultiplexed light input/output portions. The first to n?1-th mirrors are disposed in front of the first demultiplexed light input/output portion and in front of the n?1-th interference film filters. Light from the first demultiplexed light input/output portion strikes the first to n?1-th mirrors and the second to n-th interference film filters and is input to the multiplexed light input/output portion. Light output from the multiplexed light input/output portion strikes the second to n-th interference film filters and first to n?1-th mirrors.

Abstract: An optical connector connects: N (N is an integer of 3 to 14) single-mode fibers each including one core with a high refractive index in a cladding material with a low refractive index; to multi-core fiber including N cores with high refractive indexes in a cladding material with low refractive index such that the cores of the single-mode fibers are respectively optically coupled to cores of the multi-core fiber. The optical connector includes: quartz glass cylinder having a first end face to be in contact with the multi-core fiber and a second end face to be in contact with single-mode fibers; N glass fibers that are arranged in the quartz glass cylinder to extend from the first to second end face, the N glass fibers each including: a circular rod with high refractive index that has a constant outer diameter; and a low refractive index material that surrounds an outer periphery of the circular rod and has a constant thickness.

Abstract: A variable optical attenuator in which a polarization beam splitter splits a beam incoming from the front into two linearly-polarized beams perpendicular to each other and separately outputs them to the back along first and second light paths. A Faraday rotator rotates a polarization plane of the two incoming linearly-polarized beams to an arbitrary angle by controlling a magnetic field to be applied to a Faraday element by a magnetism applying means and outputs them to the back. First and second analyzers arranged in the first and the second light paths and parallelly arranged perpendicular to these light paths are arranged in that order. The two analyzers have optical axes perpendicular to each other so that the optical axes are in the same direction as that of the polarization plane of the two linearly-polarized beams output from the polarization beam splitter.

Abstract: An optical component including an interference filter which is less likely to generate back reflected light, where the filter is accommodated in a hollow cylindrical housing and is tilted with respect to the optical axis. The housing has front and back openings. First and second collimator lenses respectively face the front and back openings. The housing includes a filter housing section and first and second cylindrical optical path sections extending in the front-back direction respectively from the front and back openings to the filter housing section while maintaining the shape of each opening. The diameter of the opening of the first optical path section is smaller than the apparent diameter of the first collimator lens. When light is input from the front along the optical axis, light of prescribed wavelengths is output to the back. Light reflected by the filter travels toward the inside of the first optical path section.

Abstract: An optical switch includes: a first birefringent element; a first Faraday rotator; a first half-wave plate; a second birefringent element; a second half-wave plate; a second Faraday rotator; and a third birefringent element, which are arranged in a forward direction from the front, wherein the first birefringent element splits light in the forward direction from a first optical port into ordinary and extraordinary lights emitted onto first and second optical paths, respectively, the first and second half-wave plates are arranged on the first and second optical paths, respectively, and in the first and second Faraday rotators, a permanent magnetic field in a left-right direction and an external magnetic field in a front-back direction in an on state are applied to a Faraday element, a bidirectional optical path is formed between the first and second optical ports in an off state, and the optical path is interrupted in the on state.