Abstract: A control device of modulating signal generates high-side signal and low-side signal. The high-side signal takes level in accordance with level of AC component of a monitor signal obtained by photoelectric conversion of modulated light, when the polarity of the AC component is positive, or its magnitude is zero. The high-side signal further takes constant level when the polarity of the AC component is negative. The low-side signal takes constant level when the polarity of the AC component is positive. The low-side signal further takes level in accordance with level of the AC component when the polarity of the AC component is negative, or its magnitude is zero. Then, the control device adjusts level of the modulating signal based on a greatest value of absolute values of levels taken by the high-side signal and a greatest value of absolute values of levels taken by the low-side signal.

Abstract: An optical device is formed on an optical integrated circuit (IC) chip. The optical device includes: an optical circuit, a first grating coupler, a second grating coupler, a first 1×2 coupler, and a second 1×2 coupler. The first 1×2 coupler is equipped with a first optical port provided at a single-port end and a second optical port and a third optical port provided at a two-port end. The second 1×2 coupler is equipped with a fourth optical port provided at a single-port end and a fifth optical port and a sixth optical port provided at a two-port end. The first grating coupler is coupled to the first optical port. The second optical port is coupled to the optical circuit. The third optical port is coupled to the fourth optical port. The fifth optical port is coupled to the second grating coupler.

Abstract: An optical waveguide device includes first and second waveguides formed parallel to each other. The first waveguide includes a first rib and a first slab. The first slab is formed in a region between the first rib and the second waveguide. The second waveguide includes a second rib, a second slab and a third slab. The second rib is provided between the second slab and the third slab. The first and second slabs are integrally formed. At one end of the optical waveguide device, a first effective refractive index that indicates an effective refractive index of a TEi mode in the first waveguide is higher than a second effective refractive index that indicates an effective refractive index of a TEj mode in the second waveguide. At another end, the first effective refractive index is lower than the second effective refractive index.

Abstract: An optical device includes a substrate, a first cladding layer that is laminated on one surface of the substrate, and a first optical waveguide that is formed in the first cladding layer at a side opposite to the substrate in the first cladding layer. The optical device further includes an electro-optic crystal layer that is laminated on a surface of the first cladding layer at a side opposite to the substrate, and a second optical waveguide that is formed of the electro-optic crystal layer on a surface of the electro-optic crystal layer at a side opposite to the first cladding layer. The optical device further includes a second cladding layer that is laminated on a surface of the electro-optic crystal layer at a side opposite to the first cladding layer.

Abstract: An optical device with an optical transmitter circuit and an optical receiver circuit integrated on a substrate has at least one of a first oblique waveguide extending obliquely with respect to an edge of the substrate at or near an incident port for introducing a light emitted from a light source to the optical device, a second oblique waveguide extending obliquely with respect to the edge of the substrate at or near a signal receiving port optically connected to the optical receiver circuit, and a third oblique waveguide extending obliquely with respect to the edge of the substrate at or near a signal transmission port optically connected to the optical transmitter circuit.

Abstract: An optical device includes an electro-optic crystal layer, a first optical waveguide formed in the electro-optic crystal layer, and an electrode that applies an electric signal to the first optical waveguide. Further, the optical device includes a second optical waveguide in an amorphous state formed in the electro-optic crystal layer and connected to the first optical waveguide.

Abstract: A receiving device includes a light source outputting local oscillation light, a detector detecting intermittent input of a burst light signal by using the local oscillation light, a first converter converting the detected burst optical signal into an electrical analog signal, an amplifier amplifying the analog signal according to a gain, a second converter converting the amplified analog signal into a digital signal, and a setting processor setting the gain of the amplifier and a wavelength of the local oscillation light instructed by a control device when setting a communication line with one of transmitting devices transmitting the burst optical signal, wherein, before setting the communication line, the setting processor switches the wavelength of the local oscillation light according to the burst optical signal transmitted from each of the transmitting devices, adjusts the gain of the amplifier and notifies the control device of the adjusted gain.

Abstract: An optical modulator includes an optical waveguide through which signal light passes, a split unit that splits the signal light that passes through the optical waveguide, and a pair of phase shifters each of which shifts a phase of signal light that is split by the split unit. Each of the phase shifters includes an in-shifter waveguide through which the signal light passes, and a heater electrode that heats the in-shifter waveguide in accordance with a driving voltage. The in-shifter waveguide includes an inbound waveguide for inputting the signal light coming from the split unit, an outbound waveguide for outputting the signal light, a folded waveguide that connects the inbound waveguide and the outbound waveguide. The heater electrode is arranged in the vicinity of the inbound waveguide and the outbound waveguide.

Abstract: An optical waveguide device includes a slot groove formed in a substrate; a pair of electrodes disposed in the slot groove; an electro-optic polymer material in the slot groove; and a step portion formed at an outer side of the slot groove, in a length direction of the slot groove.

Abstract: An optical waveguide device includes an intermediate layer, a thin-film LN layer including X-cut lithium niobate, and a buffer layer stacked on a substrate; an optical waveguide formed in the thin-film LN layer; and an electrode for driving. The intermediate layer is formed by an upper first intermediate layer and a lower second intermediate layer, the second intermediate layer having a permittivity that is smaller than a permittivity of the first intermediate layer.

Abstract: An optical receiver includes an optical amplifier that amplifies a received optical signal containing multiple wavelengths, a monitor circuit that monitors light intensities of the demultiplexed optical signal, a processor, and a memory having information representing a relationship between a total incident light intensity of the optical signal incident onto the optical amplifier and gains of the optical amplifier for the respective wavelengths.

Abstract: An optical coherent transceiver includes a transmitter and a receiver that share laser light. The transmitter includes a pair of parent MZIs in a modulator, which are parent MZIs configured to perform quadrature modulation on the laser light according to a bias voltage, and two pairs of child MZIs in the modulator, which are child MZIs configured to perform phase modulation on the laser light according to the bias voltage. The transmitter includes a control circuit configured to control the bias voltage to be applied to the parent MZIs and the child MZIs. The control circuit is configured to, when turning light output of the transmitter off, with input of a data signal being set off, control the bias voltage such that a phase difference between the parent MZIs is around 90 degrees and a phase difference between the child MZIs in each of the pairs is 180 degrees.

Abstract: An optical semiconductor element includes an optical receiver including a first semiconductor layer, a heater for heating the first semiconductor layer; and a monitor. A first semiconductor layer that absorbs light and generates electric carriers; a heater for heating the first semiconductor layer; and a monitor including a second semiconductor layer in which dark current is changed by heat generated by the heater.

Abstract: An optical device includes a substrate, a dielectric substance laminated on the substrate, an optical waveguide surrounded by the dielectric substance, a heater electrode that is disposed above the optical waveguide and that is surrounded by the dielectric substance, and a trench. The trench includes a plurality of split trenches each of which is formed in a hollow segmented shape in the dielectric substance and in which the split trenches are disposed in parallel with the heater electrode. The split trenches are disposed in parallel with the heater electrode such that an area of the dielectric substance located between an end of each of the split trenches and a side surface of the heater electrode is gradually expanded.

Abstract: Optical device, that is provided between optical output element and optical propagation element, includes: first lens circuit configured to include one or more lenses through which output light of the optical output element passes; and second lens circuit configured to include one or more lenses and guide output light of the first lens circuit to the optical propagation element. When F11 represents distance between the optical output element and the first lens circuit, F12 represents distance between the first lens circuit and first beam waist position of the first lens circuit, F21 represents distance between the first beam waist position and the second lens circuit, and F22 represents distance between the second lens circuit and second beam waist position of the second lens circuit, F11 and F22 are equal to each other and F12 and F21 are equal to each other.

Abstract: An optical waveguide device has a function of removing or suppressing a higher-order mode component of propagating light. The optical waveguide device includes a curved waveguide having a curved shape where a curvature continuously changes. A first waveguide is coupled to one end of the curved waveguide and a second waveguide is coupled to the other end of the curved waveguide. A curvature of the first waveguide and the curvature of the curved. waveguide are equal to each other in a coupling point in which the first waveguide is coupled to the curved waveguide, and a curvature of the second waveguide and the curvature of the curved waveguide are equal to each other in a coupling point in which the second waveguide is coupled to the curved waveguide.

Abstract: A photodetector has a substrate, a light input layer formed as a first semiconductor over the substrate, the first semiconductor being transparent to a wavelength being used, and a light absorption layer formed as a second semiconductor on the light input layer, the second semiconductor having a bandgap smaller than that of the first semiconductor. The light absorption layer has a first region doped with a first conductivity-type impurity, a second region doped with a second conductive-type impurity different from the first conductive-type impurity, and an undoped region between the first region and the second region. The first region, the undoped region and the second region are arranged in a direction parallel to the substrate. The light absorption layer has a region having an effective refractive index higher than the rest of the light absorption layer between the first region and the second region.

Abstract: An optical integrated device includes a substrate and a waveguide that has a hollow structure. The waveguide includes a first waveguide and a second waveguide that is optically coupled to the first waveguide and that has a smaller relative refractive index difference than that of the first waveguide and converts a mode diameter to a mode diameter of an optical fiber in accordance with travelling of light. The optical integrated device includes a dent portion that is formed in the vicinity of the dicing line on the substrate such that the width of the output end surface is smaller than the core width of the optical fiber that is optically coupled to the output end surface in the state in which the dicing end surface of the substrate protrudes farther than the output end surface of the second waveguide in the axial direction of the optical waveguide.

Abstract: An optical device cut from a wafer into a chip by dicing, on the wafer, the optical device includes a plurality of optical waveguides; an optical circuit connected to the optical waveguide; and of the plurality of optical waveguides, a testing optical waveguide that guides test light to the optical circuit to be tested, by bypassing a non-connected optical waveguide portion at a terrace for mounting an optical chip component.

Abstract: An optical device includes a modulator and a tap coupler. The modulator includes an optical waveguide that is formed of a thin-film lithium niobate (LN) substrate and through which light passes, and an electrode that applies voltage to the optical waveguide, and modulates a phase of light that passes through the optical waveguide in accordance with an electric field in the optical waveguide, where the electric field corresponds to the voltage. The tap coupler includes at least a part formed of the thin-film LN substrate, and splits a part of the light that passes through an inside of the optical waveguide. The tap coupler includes a delayed interferometer that splits a part of the light that passes through the optical waveguide, at a split ratio corresponding to a phase difference of light that passes through an inside of the tap coupler from the optical waveguide.