Abstract: An optical connection structure comprising: a substrate including a main surface and an optical waveguide in which a beam is incident or emitted in a direction intersecting with the main surface; a receptacle including a first lens and a connector guide and disposed on the substrate such that the first lens and the optical waveguide are optically coupled; and an optical connector including a second lens and a guide unit and holding an optical fiber so as to be optically coupled with the second lens, wherein: the receptacle and the optical connector are configured to be detachably through the connector guide and the guide unit; and the first lens and the second lens are optically coupled by mounting the optical connector to the receptacle.

Abstract: A lens component of the present invention has an identification mark that can be formed without impairing the lens surface profile. The lens component includes: at least one set of lenses including, an element-side lens provided facing to a light emitting and receiving element; and a fiber-side lens provided facing to a transmitting and receiving optical fiber; an element-side lens forming surface formed on the element-side lens; and an identification mark provided on the element-side lens forming surface. The element-side lens and the identification mark are separated from each other by a distance that is at least the radius of the element-side lens.

Abstract: An optical device which reduces coupling loss while improving practicality is provided. A multi-core fiber coupling device is an optical device which couples a multi-core fiber to single core fibers, and includes a first optical system which is located on optical axes of a plurality of beams emitted from the multi-core fiber, and which makes the optical axes of the respective beams non-parallel to each other, thereby making the beams in a state of being separated from each other, and a second optical system S2 which makes the optical axes of the plurality of beams in a state of being non-parallel to each other on the side of the first optical system, in a state of being approximately parallel to each other.

Abstract: A lens component has a element-side lens portion 65 which is provided so as to face a light emitting and receiving element 52 mounted on a circuit substrate 24, a positioning portion 75 that protrudes such that the element-side lens portion 65 is separated from the circuit substrate 24 by a predetermined distance, and an adhesion portion 76 that forms an adhesive-agent filling space S, which is filled with an adhesive agent 77, between the circuit substrate 24 and the adhesion portion 26, in a state where the positioning portion 75 contacts with the circuit substrate 24 and the element-side lens portion 65 is fixed so as to face the light emitting and receiving element 52.

Abstract: An optical connection structure comprising: a substrate including a main surface and an optical waveguide in which a beam is incident or emitted in a direction intersecting with the main surface; a receptacle including a first lens and a connector guide and disposed on the substrate such that the first lens and the optical waveguide are optically coupled; and an optical connector including a second lens and a guide unit and holding an optical fiber so as to be optically coupled with the second lens, wherein: the receptacle and the optical connector are configured to be detachably through the connector guide and the guide unit; and the first lens and the second lens are optically coupled by mounting the optical connector to the receptacle.

Abstract: A lens component has a element-side lens portion 65 which is provided so as to face a light emitting and receiving element 52 mounted on a circuit substrate 24, a positioning portion 75 that protrudes such that the element-side lens portion 65 is separated from the circuit substrate 24 by a predetermined distance, and an adhesion portion 76 that forms an adhesive-agent filling space S, which is filled with an adhesive agent 77, between the circuit substrate 24 and the adhesion portion 26, in a state where the positioning portion 75 contacts with the circuit substrate 24 and the element-side lens portion 65 is fixed so as to face the light emitting and receiving element 52.

Abstract: A lens component of the present invention has an identification mark that can be formed without impairing the lens surface profile. The lens component includes: at least one set of lenses including, an element-side lens provided facing to a light emitting and receiving element; and a fiber-side lens provided facing to a transmitting and receiving optical fiber; an element-side lens forming surface formed on the element-side lens; and an identification mark provided on the element-side lens forming surface. The element-side lens and the identification mark are separated from each other by a distance that is at least the radius of the element-side lens.

Abstract: An optical connecting member includes a board chip, an optical element mounted on the board chip, and a lens member including a lens part optically connected to the optical element. An accommodating space for accommodating the optical element is formed between the lens member and the board chip. The accommodating space communicates with the outside only through a very small communicating part.

Abstract: An optical device which reduces coupling loss while improving practicality is provided. A multi-core fiber coupling device is an optical device which couples a multi-core fiber to single core fibers, and includes a first optical system which is located on optical axes of a plurality of beams emitted from the multi-core fiber, and which makes the optical axes of the respective beams non-parallel to each other, thereby making the beams in a state of being separated from each other, and a second optical system S2 which makes the optical axes of the plurality of beams in a state of being non-parallel to each other on the side of the first optical system, in a state of being approximately parallel to each other.

Abstract: In an optical waveguide grating in an optical fiber having a cladding region around a core region, a periodic refractive index distribution is existed in a predetermined area of the core region along the optical axis. The core region has a composition of GeO2—P2O5—SiO2 based glass, for example, whereas the cladding region is made of SiO2, and the co-doping ratio in the core region is adjusted, so as to lower the temperature dependence of characteristics. The doping amount of P2O5 in the core region is preferably {fraction (1/15)} to 1 times, more preferably 0.6 to 1 times that of GeO2.

Abstract: The present invention relates to a long-period grating device which eliminates only a desirable wavelength of core-mode light in a wavelength band in use from 1525 nm to 1610 nm. The long-period grating device according to the present invention comprises an optical fiber provided with a core region and a cladding region, whereas a long-period grating whose refractive index changes with a period &Lgr; in the advancing direction of light is provided in the core region, wherein the period &Lgr; is set such that the absolute value of a loss peak due to mode coupling concerning a refractive index modulation component with a period &Lgr;/(2n+1) (n=1, 2, 3, 4) is 0.2 dB or less in the wavelength band in use.

Abstract: The present invention provides a method for determining a condition of aging for an optical waveguide grating. In this method, the aged deterioration,curve of the optical waveguide grating is set as a forms of C·t−&agr;, t represents time, and &agr; and C represent parameters. Then, the condition of the aging is determined based on the aged deterioration curve.

Abstract: The present invention provides a method for determining a condition of aging for an optical waveguide grating. In this method, the aged deterioration curve of the optical waveguide grating is set as a form of C·t−&agr;, where t represents time, and &agr; and C represent parameters. Then, the condition of the aging is determined based on the aged deterioration curve.

Abstract: The present invention relates to an optical filter having a long-period grating which couples, in signal light propagating through a core region, core mode light having a predetermined wavelength to cladding mode light, thereby attenuating the core mode light; and a method of making the same. In particular, in the filter area provided with the long-period grating, the intervals of individual parts exhibiting its average refractive index is constant along the advancing direction of the signal light, whereas values of maximum points and minimum points of a refractive index modulation function defining the refractive index vary along the advancing direction of the signal light.

Abstract: The present invention provides a method for determining a condition of aging for an optical fiber grating. This method comprises a step of setting the aged deterioration curve of the optical fiber grating as a form proportional to t.sup.-n, where t represents time, and n represents a parameter dependent on temperature; and a step of determining the condition of the aging according to the aged deterioration curve.

Abstract: In an optical filter formed with a grating whose refractive index fluctuates along an optical axis of an optical waveguide so as to reflect light in a predetermined wavelength band, assuming that a position in the grating area is defined by a positional coordinate value z which is standardized by -.pi. to .pi. in a light propagating direction, an amplitude .DELTA.n of refractive index changing width in z satisfies: ##EQU1## by use of predetermined parameters x.sub.1 and x.sub.2 and proportional constants k.sub.1 and k.sub.2, .DELTA.n monotonously increasing or decreasing depending on whether the expression -.pi..ltoreq.z.ltoreq.0 or 0.ltoreq.z.ltoreq..pi. is satisfied, respectively.

Abstract: A band-pass filter formed in an optical waveguide, provided with a diffraction grating group having a period .LAMBDA. of refractive index fluctuation changing in an axial direction with substantially a constant changing width .DELTA.n, comprises two periodic refractive index variable areas having periodes .LAMBDA. different from each other; a zero area, disposed therebetween, having substantially a constant refractive index; and boundary areas, disposed between the zero area and the respective periodic refractive index variable areas, in which the changing width of refractive index monotonously changes between 0 and .DELTA.n.