Abstract: The present invention provides an optical functional circuit where a holographic wave propagation medium is applied and a circuit property is excellent such as small transmission loss and crosstalk. The optical functional circuit where a plurality of circuit elements are formed on a substrate includes the wave propagation medium for converting an optical path of a leakage light so that the leakage light that is not emitted from a predetermined output port of the circuit element is not coupled to a different circuit element. This wave propagation medium is constituted by an optical waveguide that is provided with a clad layer formed on the substrate and a core embedded in the clad layer, and a part of the optical waveguide is formed in accordance with a refractive index distribution which is multiple scattered.

Abstract: A planar lightwave circuit is provided which can be easily fabricated by an existing planar-lightwave-circuit fabrication process, which can lower the propagation loss of signal light and which can convert inputted signal light so as to derive desired signal light. A planar lightwave circuit having a core and a clad which are formed on a substrate, has input optical waveguide(s) (111) which inputs signal light, mode coupling part (112) for coupling a fundamental mode of the inputted signal light to a higher-order mode and/or a radiation mode, or mode re-coupling part (113) for re-coupling the higher-order mode and/or the radiation mode to the fundamental mode, and output optical waveguide(s) (114) which outputs signal light. The mode coupling part or the mode re-coupling part is an optical waveguide which has core width and/or height varied continuously.

Abstract: The present invention provides an optical functional circuit where a holographic wave propagation medium is applied and a circuit property is excellent such as small transmission loss and crosstalk. The optical functional circuit where a plurality of circuit elements are formed on a substrate includes the wave propagation medium for converting an optical path of a leakage light so that the leakage light that is not emitted from a predetermined output port of the circuit element is not coupled to a different circuit element. This wave propagation medium is constituted by an optical waveguide that is provided with a clad layer formed on the substrate and a core embedded in the clad layer, and a part of the optical waveguide is formed in accordance with a refractive index distribution which is multiple scattered.

Abstract: An arrayed waveguide grating type optical multiplexer/demultiplexer circuit in which wavelength dispersion is reduced. An input wave guide (1), a first slab waveguide (2), an arrayed waveguide (3), a second slab waveguide (4) and an output waveguide (5) are connected sequentially. Furthermore, a parabola waveguide (6) is provided between the input waveguide (1) and the first slab waveguide (2), and a taper waveguide (7) is provided between the second slab waveguide (4) and the output waveguide (5). A parabola waveguide length Z0 exists in a range Za,0=Z0=Zp,0 determined by a parabola waveguide length Za,0 where the ratio of absolute amplitude between the main peak and the first side peak in the field distribution of far-field of the parabola waveguide (6) has an upper limit of 0.217, and a parabola waveguide length Zp,0 where the relative phase of the main peak and the first side peak in the field distribution of far-field has a lower limit of 3.14 radian.

Abstract: A wave transmission medium includes an input port 3-1 and an output port 3-2. A field distribution 1 and a field distribution 2 are obtained by numerical calculations. The field distribution 1 is a field distribution of the propagation light (forward propagation light) launched into the input port 3-1. The field distribution 2 is a field distribution of the phase conjugate light (reverse propagation light) resulting from reversely transmitting from the output port side an output field that is expected to be output from the output port 3-2 when an optical signal is launched into the input port 3-1. According to the field distributions 1 and 2, a spatial refractive index distribution is calculated such that the phase difference between the propagation light and reverse propagation light is eliminated at individual points (x, z) in the medium.

Abstract: An arrayed waveguide grating type optical multiplexer/demultiplexer circuit in which wavelength dispersion is reduced. An input wave guide (1), a first slab waveguide (2), an arrayed waveguide (3), a second slab waveguide (4) and an output waveguide (5) are connected sequentially. Furthermore, a parabola waveguide (6)is provided between the input waveguide (1) and the first slab waveguide (2), and a taper waveguide (7) is provided between the second slab waveguide (4) and the output waveguide (5). A parabola waveguide length Z0 exists in a range Za,0=Z0=Zp,0 determined by a parabola waveguide length Za,0 where the ratio of absolute amplitude between the main peak and the first side peak in the field distribution of far-field of the parabola waveguide (6) has an upper limit of 0.217, and a parabola waveguide length Zp,0 where the relative phase of the main peak and the first side peak in the field distribution of far-field has a lower limit of 3.14 radian.

Abstract: An optical multi/demultiplexing circuit includes at least one phase generating optical coupler and an optical delay line coupled to the phase generating optical coupler. The phase generating optical coupler consists of at least one input and at least two outputs. At least one of the phase generating optical coupler has a wavelength dependent or frequency dependent output phase difference in the passband of the circuit so that it can change the transmittance characteristics of the optical multi/demultiplexing circuit.

Abstract: A wave transmission medium includes an input port 3-1 and an output port 3-2. A field distribution 1 and a field distribution 2 are obtained by numerical calculations. The field distribution 1 is a field distribution of the propagation light (forward propagation light) launched into the input port 3-1. The field distribution 2 is a field distribution of the phase conjugate light (reverse propagation light) resulting from reversely transmitting from the output port side an output field that is expected to be output from the output port 3-2 when an optical signal is launched into the input port 3-1. According to the field distributions 1 and 2, a spatial refractive index distribution is calculated such that the phase difference between the propagation light and reverse propagation light is eliminated at individual points (x, z) in the medium.

Abstract: The present invention discloses an interferometer optical switch that can carry out switching over a broad band and has a high extinction ratio and large fabrication tolerance. The interferometer optical switch employs a phase generating coupler, the phase difference of the output of which has wavelength dependence, as at least one of the optical multi/demultiplexing device included in the interferometer optical switch. A wavelength insensitive interferometer optical switch is implemented by making the sum 2?{?1(?)+??L(?)+?2(?)} constant regardless of the wavelength, where ?1(?) is the phase produced by the first optical multi/demultiplexing device, 2???L(?) is the phase difference of the optical delay line with an optical path length difference of ?L, and 2??2(?) is the phase produced by the second optical multi/demultiplexing device.

Abstract: A planar lightwave circuit is provided. The planar lightwave circuit includes a waveguide and a spotsize converter which is a part of the waveguide, wherein a core is embedded in a cladding in the waveguide, and the spotsize converter is located near an end face of a substrate on which the planar lightwave circuit is formed, the spotsize converter including: a core width fine-tuning part in an end face side of the substrate; and a core width converting part which follows the core width fine-tuning part; wherein core width of the spotsize converter is minimum at an end face of the substrate, a mean taper angle ?1 of the core width fine-tuning part is larger than 0° and smaller than a mean taper angle ?2 of the core width converting part.

Abstract: An optical multi/demultiplexing circuit includes at least one phase generating optical coupler and an optical delay line coupled to the phase generating optical coupler. The phase generating optical coupler consists of at least one input and at least two outputs. At least one of the phase generating optical coupler has a wavelength dependent or frequency dependent output phase difference in the passband of the circuit so that it can change the transmittance characteristics of the optical multi/demultiplexing circuit.

Abstract: The present invention provides an optical demultiplexer and an optical multiplexer the transmission characteristics of which are unlikely to be affected by fabrication errors and which have small group delay dispersion. A cross output port (X-OUT) of a second optical demultiplexer element (DEMUX) is selected, and a through output port (T-OUT) of a third DEMUX is selected. A T-OUT of a first DEMUX has a passband equal to the X-OUT of the second DEMUX, and a X-OUT of the first DEMUX has a passband equal to the T-OUT of the third DEMUX. The T-OUT of the first DEMUX has group delay characteristics opposite to those of the X-OUT of the second DEMUX, and the X-OUT of the first DEMUX has group delay characteristics opposite to those of the T-OUT of the third DEMUX.

Abstract: An optical multi/demultiplexer is provided that has a wide passband and small crosstalk among its all channels. It includes first and second arrayed waveguide gratings and a 2×2 optical signal processor. The 2×2 optical signal processor includes first to fourth directional couplers, and first to third delay lines. The first to third delay lines have thin film heater phase shifters for correcting phase errors involved in fabrication. Utilizing the 2×2 optical signal processor having a transmission spectrum with a square profile having a wide passband and rejection band makes it possible for the optical multi/demultiplexer that combines the arrayed waveguide gratings with the waveguide type circulating filter (2×2 optical signal processor) to widen the extinction bandwidth of the adjacent channel.

Abstract: A planar lightwave circuit is provided. The planar lightwave circuit includes a waveguide and a spotsize converter which is a part of the waveguide, wherein a core is embedded in a cladding in the waveguide, and the spotsize converter is located near an end face of a substrate on which the planar lightwave circuit is formed, the spotsize converter including: a core width fine-tuning part in an end face side of the substrate; and a core width converting part which follows the core width fine-tuning part; wherein core width of the spotsize converter is minimum at an end face of the substrate, a mean taper angle &thgr;1 of the core width fine-tuning part is larger than 0° and smaller than a mean taper angle &thgr;2 of the core width converting part.

Abstract: The present invention provides an optical demultiplexer and an optical multiplexer the transmission characteristics of which are unlikely to be affected by fabrication errors and which have small group delay dispersion. A cross output port (X-OUT) of a second optical demultiplexer element (DEMUX) is selected, and a through output port (T-OUT) of a third DEMUX is selected. A T-OUT of a first DEMUX has a passband equal to the X-OUT of the second DEMUX, and a X-OUT of the first DEMUX has a passband equal to the T-OUT of the third DEMUX. The T-OUT of the first DEMUX has group delay characteristics opposite to those of the X-OUT of the second DEMUX, and the X-OUT of the first DEMUX has group delay characteristics opposite to those of the T-OUT of the third DEMUX.

Abstract: An optical multi/demultiplexer is provided that has a wide passband and small crosstalk among its all channels. It includes first and second arrayed waveguide gratings and a 2×2 optical signal processor. The 2×2 optical signal processor includes first to fourth directional couplers, and first to third delay lines. The first to third delay lines have thin film heater phase shifters for correcting phase errors involved in fabrication. Utilizing the 2×2 optical signal processor having a transmission spectrum with a square profile having a wide passband and rejection band makes it possible for the optical multi/demultiplexer that combines the arrayed waveguide gratings with the waveguide type circulating filter (2×2 optical signal processor) to widen the extinction bandwidth of the adjacent channel.