Fujikura Limited

Akira Oka

Kensuke Ogawa

Hiroyuki Kusaka

Kazuhiro Goi

Takuya Oda

An optical module includes: an output section that outputs TM light; and a substrate-type optical waveguide. The substrate-type optical waveguide includes: a waveguide that guides the TM light outputted from the output section; a polarization rotating element that converts the TM light guided through the waveguide into TE light; and a function element that receives the TE light. In the optical module equation (a&#xd7;L)&#x3e;(b&#xd7;L+c) is satisfies, where L is a length of the waveguide, a is a propagation loss of the TE light per unit length of the waveguide, b is a propagation loss of the TM light per unit length of the waveguide, and c is an insertion loss by the polarization rotating element.

Optical module and inputting method

In a substrate-type optical waveguide element, in a case where effective refractive indexes of a TE polarized wave and a TM polarized wave in a first core are defined as N@WG1 and N@WG1, respectively, and effective refractive indexes of a TE polarized wave and a TM polarized wave in a second core are defined as N@WG2 and N@WG2, respectively, a magnitude relation of the effective refractive indexes N@WG1 and N@WG2 at a start position of a parallel-core section is opposite to that at an end position of the parallel-core section, and a relative refractive index difference defined by Formula (a) is 0.25 or higher.

Substrate-type optical waveguide element and method for producing substrate-type optical waveguide element

A planar optical waveguide device includes: a substrate; a core that forms a first waveguide and a second waveguide that are arranged in parallel on the substrate; and a cladding that covers the core and has a refractive index smaller than that of the core. The core includes a first rib portion that forms the first waveguide, a second rib portion that forms the second waveguide, and a slab portion that is provided only on one side of the first rib portion and the second rib portion in a width direction to have a thickness smaller than the thicknesses of the first rib portion and the second rib portion and is shared between the first rib portion and the second rib portion.

Planar optical waveguide device, DP-QPSK modulator, coherent receiver, and polarization diversity

Provided is a substrate-type optical waveguide element in which when (i) effective refractive indexes of a TE polarized wave and a TM polarized wave in the first core are N@WG1 and N@WG1, respectively, and (ii) effective refractive indexes of a TE polarized wave and a TM polarized wave in the second core are N@WG2 and N@WG2, respectively, a magnitude relation of the effective refractive indexes N@WG1 and N@WG2 at a start position of a parallel-core section is opposite to a magnitude relation of the effective refractive indexes N@WG1 and N@WG2 at an end position of the parallel-core section, and at least one of the cores includes (a) a main part having a quadrilateral cross section and (b) a protruding part protruding from one of side surfaces of the main part in a direction parallel to a boundary surface between a lower cladding and a upper cladding.

Substrate-type optical waveguide element

A planar optical waveguide device includes: a substrate; and an optical waveguide that includes a core and a cladding. The core forms a preceding-stage mode conversion section and a subsequent-stage mode conversion section, the preceding-stage mode conversion section being configured to convert a mode of input light, the subsequent-stage mode conversion section being configured to convert a mode of light output from the preceding-stage mode conversion section. Sectional shapes of the first core portion and the second core portion are not congruent with each other at an input end of the preceding-stage mode conversion section, the sectional shape or size of at least one core is continuously changed along a light waveguide direction, and sectional shapes of the first core portion and the second core portion are congruent with each other at an output end of the preceding-stage mode conversion section.

Planar optical waveguide device, polarization multiplexing 4-value phase modulator, coherent receiver, and polarization diversity

An effective refractive index of a TM0 polarized wave guided through the first core when existing alone and an effective refractive index of a TE0 polarized wave guided through the second core when existing alone are continuous as a function of a distance from a starting point of a side-by-side arrangement section. A magnitude relationship between an effective refractive index of an odd mode of a TE0 polarized wave guided through the side-by -side arrangement section and an effective refractive index of an even mode of a TM0 polarized wave guided through the side-by-side arrangement section is reversed between the starting point and an ending point of the side-by-side arrangement section. A refractive index distribution is vertically asymmetrical in an interaction section.

An effective refractive index of a TM0 polarized wave guided through the first core when existing alone and an effective refractive index of a TE0 polarized wave guided through the second core when existing alone are continuous as a function of a distance from a starting point of a side-by-side arrangement section. A magnitude relationship between an effective refractive index of an odd mode of a TE0 polarized wave guided through the side-by-side arrangement section and an effective refractive index of an even mode of a TM0 polarized wave guided through the side-by-side arrangement section is reversed between the starting point and an ending point of the side-by-side arrangement section. A refractive index distribution is vertically asymmetrical in an interaction section. An emission edge surface and an emission edge surface cover an entrance edge surface without excess or deficiency.

A high-order polarization conversion device configured of a planar optical waveguide, includes: a substrate; a lower clad disposed on the substrate; a core including a lower core and an upper core, the lower core being disposed on the lower clad and having a fixed height in a rectangular sectional shape, the upper core being formed of the same material as the lower core and having a fixed height in a rectangular sectional shape that is disposed continuously on the lower core; and an upper clad that is disposed on the core and the lower clad and is formed of the same material as the lower clad. The high-order polarization conversion device performs high-order polarization conversion between TEof the start portion and TMof the end portion.

High-order polarization conversion device, optical waveguide device, and DP-QPSK modulator

A polarization conversion element is disclosed in which an optical waveguide formed on a substrate sequentially includes a first waveguide portion, a polarization rotation portion, and a second waveguide portion, an effective refractive index of a TE mode having the highest effective refractive index in an eigen mode of waveguide light on a sectional surface of the first waveguide portion is higher than an effective refractive index of a TM mode having the highest effective refractive index, an effective refractive index of the TM mode having the highest effective refractive index on a sectional surface of the second waveguide portion is higher than an effective refractive index of the TE mode having the highest effective refractive index, and heights of waveguide structures (for example, cores) of the first waveguide portion and the second waveguide portion are equal to each other.

Polarization conversion element

A planar optical waveguide element includes: a substrate; and an optical waveguide comprising a core and a cladding, the core being provided on the substrate so as to include first and second core regions arranged in parallel, the cladding having a smaller refractive index than the core. Also, the core forms a preceding-stage mode conversion portion that converts a mode of input light and a subsequent-stage mode conversion portion that converts a mode of light output from the preceding-stage mode conversion portion, and the first and second core regions are spaced apart from each other at an input end of the subsequent-stage mode conversion portion, and a gap between the first and second core regions is continuously decreased along the light waveguide direction such that the first and second core regions are in contact with each other at an output end of the subsequent-stage mode conversion portion.

Planar optical waveguide element, dual polarization quadrature phase shift keying modulator, coherent receiver, and polarization diversity

A planar optical waveguide device, includes: two input portions that are waveguides that have the same width, are parallel to each other, and have rectangular cross-sections; a wide portion that is a linear waveguide and is connected after the two input portions; a tapered portion that is connected after the wide portion and that is a multi-mode waveguide which has a tapered shape having a width decreasing gradually and through which at least TE1 propagates; and an output portion that is connected after the tapered portion and that is a multi-mode waveguide which has a rectangular cross-section and through which at least TE1 propagates. The planar optical waveguide device forms a high-order mode conversion combining element that outputs the TE0, which is input to the two input portions, as the TE1 from the output portion.

Planar optical waveguide device and DP-QPSK modulator

Since a cross section of at least a partial segment of a first core has a step-like shape including a quadrilateral shape of a main part and a quadrilateral shape of a protruding part protruding from the main part, respective effective refractive indices of TE polarized waves in the first core and in the second core differ from each other.

Substrate-type waveguide element and optical modulator

A polarization conversion device includes: a directional coupler that includes an input side optical waveguide and an output side optical waveguide which are disposed in parallel to each other and each of which has a core. Assuming that a direction in which the input side optical waveguide and the output side optical waveguide face each other is a width direction and a direction perpendicular to the width direction is a height direction in a cross section perpendicular to a longitudinal direction of each of the input side optical waveguide and the output side optical waveguide, and the directional coupler is configured to couple first light guided through the input side optical waveguide to second light guided through the output side optical waveguide, the polarization direction of the second light is perpendicular to that of the first light.

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Sakura, Japan

Akira Oka