Abstract: A housing 20 is equipped for supporting, from a side, a platform of a wavelength selection device comprising an input/output port 10, a collimator 11, an expanding optical system 12, a spectroscopic element, a collecting optical system 14 and a micro electro mechanical system (MEMS) mirror array 15. Because the above noted optical member is supported from the side only, influences of a thermal expansion is limited to the height direction of the optical member and the optical axis direction. By these aspects, the influence of thermal expansion is limited to a two-dimensional from a common three-dimensional, thereby enabling a design of a countermeasure to an influence of a thermal expansion. Also, the support from the side does not create a dead space thereby making the wavelength selection device compact.

Abstract: An optical device enabling reducing device scale is constituted by M circulators (11a, 11b), (M being a natural number), a waveguide-type diffraction grating (12) including M first input/output waveguides (121a, 121b) formed at its one end and M×N second input/output waveguides (125a-1 to 125a-N and 125b-1 to 125b-N) formed at the other end, (N being a natural number), and paths from the M circulators being connected to the M first input/output waveguides; and N reflection-type optical switches (13-1 to 13-N) each for reflecting the optical paths for M adjacent waveguides out of the M×N second input/output waveguides (125a-1 to 125a-N and 125b-1 to 125b-N) and for switching over the returning-destination waveguide respectively, wherein the M circulators, the waveguide-type diffraction grating and N reflection-type optical switches are arranged in cascade. Consequently, the optical device can function preferably also as a wavelength selective optical switch available in a WDM transmission system.

Abstract: In a multi-wavelength spectroscopic apparatus using diffraction gratings, a first diffraction grating is a diffraction grating with diffraction efficiencies of p-polarized light and s-polarized light being equal on a short wavelength side of an operating wavelength range, and a second diffraction grating is a diffraction grating with diffraction efficiencies of p-polarized light and s-polarized light being equal on a long wavelength side of an operating wavelength range. By performing dispersion with two such diffraction gratings, it is possible to enlarge the amount of angular dispersion, and to produce a spectroscopic apparatus, which cancels wavelength dependencies of the diffraction efficiencies and has a small wavelength dependency of the diffraction efficiency.

Abstract: A tunable dispersion compensator includes a collimating unit that collimates an incident light to output a parallel light, a parallel shifting unit that spatially shifts the parallel light from the collimating unit within a predetermined range, and an optical-path-length providing unit that provides optical path length of light corresponding to a position at which light output from the parallel shifting unit is input.

Abstract: A wavelength selective optical switch of the present invention separates a WDM light emitted from an input port of an input and output optical system, according to wavelengths, by a diffraction grating, and thereafter, condenses the lights of respective wavelengths on MEMS mirrors respectively corresponding to the respective wavelengths, in a mirror array, to reflect them by a condenser optical system, to thereby switch optical paths for the respective lights. The condenser optical system is configured by combining a plurality of lenses whose focal distances are different from each other, and positions in an optical axis direction of the lenses are adjustable by a slide mechanism. Thus, despite an error in the focal distances of the condenser lenses, in a mounting angle of a spectral element or the like, a beam pitch at the condensing positions of the lights of respective wavelengths can be coincident with a mirror pitch in the mirror array.

Abstract: A dispersion-slope compensator including a feedback-type optical filter constituted by a looped optical line; an input-and-output optical line which inputs and outputs optical signals; and optical couplers which couples the looped optical line and the input-and-output optical line at two or more positions so that a Mach-Zehnder interferometer is formed by a portion of the looped optical line and a portion of the input-and-output optical line which are located between two of the optical couplers. A portion of the optical path realizing an MZI arm which constitutes the Mach-Zehnder interferometer is spatially separated from the other portions of the optical path so that the optical length of the MZI arm can be variably adjusted, and an amount of compensation for dispersion slope can be variably set.

Abstract: An optical device enabling reducing device scale is constituted by M circulators (11a, 11b), (M being a natural number), a waveguide-type diffraction grating (12) including M first input/output waveguides (121a, 121b) formed at its one end and M×N second input/output waveguides (125a-1 to 125a-N and 125b-1 to 125b-N) formed at the other end, (N being a natural number), and paths from the M circulators being connected to the M first input/output waveguides; and N reflection-type optical switches (13-1 to 13-N) each for reflecting the optical paths for M adjacent waveguides out of the M×N second input/output waveguides (125a-1 to 125a-N and 125b-1 to 125b-N) and for switching over the returning-destination waveguide respectively, wherein the M circulators, the waveguide-type diffraction grating and N reflection-type optical switches are arranged in cascade. Consequently, the optical device can function preferably also as a wavelength selective optical switch available in a WDM transmission system.

Abstract: An optical device used, for example, in an add/drop multiplexer, a dynamic gain equalizer or a optical power monitor. The optical device includes (a) a substrate; (b) a first slab waveguide formed on the substrate; (c) channel waveguides of differing lengths formed on the substrate, light output from the first slab waveguide being input to the channel waveguides; and (d) a second slab waveguide formed on the substrate, light output from the channel waveguides being input to the second slab waveguide. An end face of the second slab waveguide shares a face with an end face of the substrate. The optical device has low loss characteristics.

Abstract: The present invention provides an optical switch for restricting a reduction in an optical coupling efficiency to an output optical path, which comprises a first spectral unit, a second spectral unit for further spectrally diffracting a plurality of wavelength components spectrally diffracted in the first spectral unit, a plurality of movable mirrors capable of reflecting the plurality of wavelength components spectrally diffracted in the second spectral unit respectively and directing the same in different directions, and a controller for compensating for deviation angles relative to optical axes of the plurality of wavelength components spectrally diffracted in the second spectral unit through setting of angles of reflecting faces in the plurality of movable mirrors.

Abstract: The optical switch includes: a spectroscopic device which separates wavelength division multiplexed (WDM) light into its component wavelengths; and a plurality of movable reflectors, arranged in a spectral direction at different intervals, for reflecting light of an individual component wavelength separated by said spectroscopic device. With this optical switch, deterioration of the characteristic of the pass band is avoided, so that the pass band characteristic is increased.

Abstract: A collimator array includes a substrate; a plurality of lenses formed on one face of the substrate; and a plurality of projecting parts, each of which is formed on a portion corresponding to the lens on the other face of the substrate, respectively and is fusion-connected to an optical fiber, respectively; wherein an area of the fusion-connected face of the projecting part with respect to the optical fiber is set to be larger than a cross sectional area of the optical fiber. Thereby, it is possible to provide a collimator having fewer variations in an output beam angle and a diameter of an output beam and having excellent strength, and a method for manufacturing the same.

Abstract: A dispersion-slope compensator including a feedback-type optical filter constituted by a looped optical line; an input-and-output optical line which inputs and outputs optical signals; and optical couplers which couples the looped optical line and the input-and-output optical line at two or more positions so that a Mach-Zehnder interferometer is formed by a portion of the looped optical line and a portion of the input-and-output optical line which are located between two of the optical couplers. A portion of the optical path realizing an MZI arm which constitutes the Mach-Zehnder interferometer is spatially separated from the other portions of the optical path so that the optical length of the MZI arm can be variably adjusted, and an amount of compensation for dispersion slope can be variably set.

Abstract: A tunable dispersion compensator includes a collimating unit that collimates an incident light to output a parallel light, a parallel shifting unit that spatially shifts the parallel light from the collimating unit within a predetermined range, and an optical-path-length providing unit that provides optical path length of light corresponding to a position at which light output from the parallel shifting unit is input.

Abstract: A 2-input, 2-output optical circuit is constructed by serially connecting two or more Mach-Zehnder interferometers possessing a structure in which two waveguides are embraced by two couplers. One output and one input of the two 2-input, 2-output optical circuit are connected by an optical propagation path to thereby construct a loop circuit. The waveguides of the Mach-Zehnder interferometers as well as the loop circuit are each provided with an optical path-length adjustment portion, thereby constructing a wavelength dispersion compensating filter.

Abstract: An optical device used, for example, in an add/drop multiplexer, a dynamic gain equalizer or a optical power monitor. The optical device includes (a) a substrate; (b) a first slab waveguide formed on the substrate; (c) channel waveguides of differing lengths formed on the substrate, light output from the first slab waveguide being input to the channel waveguides; and (d) a second slab waveguide formed on the substrate, light output from the channel waveguides being input to the second slab waveguide. An end face of the second slab waveguide shares a face with an end face of the substrate. The optical device has low loss characteristics.

Abstract: A 2-input, 2-output optical circuit is constructed by serially connecting two or more Mach-Zehnder interferometers possessing a structure in which two waveguides are embraced by two couplers. One output and one input of the two 2-input, 2-output optical circuit are connected by an optical propagation path to thereby construct a loop circuit. The waveguides of the Mach-Zehnder interferometers as well as the loop circuit are each provided with an optical path-length adjustment portion, thereby constructing a wavelength dispersion compensating filter.

Abstract: The output from a digital signal amplitude regenerator circuit in which the amplitude of a transmitted burst data signal is amplified, and an initial potential generator circuit, are connected to a switch. While there are no burst data, the initial potential generator circuit provides a circuit for compensating for degradation in pulse width comprising a low-pass filter, a pulse width compensation threshold generator circuit, and a limiting amplifier, with an initial potential needed to set a threshold. When a carrier detection signal generator circuit detects the arrival of a burst data signal, a carrier detection signal is outputted, and the switch is switched over from the initial potential to the burst data signal. Thus, the circuit for compensating for the degradation in pulse width located at a later stage can detect a threshold from an optimal initial potential, and thereby the degradation in pulse width can be optimally compensated.

Abstract: In a signal amplifying circuit connected to a transfer circuit having a known non-linear transfer characteristic and a transient characteristic, a threshold generation circuit generates a threshold signal based on an input signal, a threshold control circuit controls the threshold signal so as to correct the non-linear transfer characteristic of the transfer circuit provided at a former stage based on the input signal. Also, basic amplifying circuit blocks can be connected in a multistage form, each of which is composed of a threshold generation circuit and a differential amplifying circuit, and control the threshold signal of a latter stage block so as to correct the non-linear transfer characteristic of a basic amplifying circuit block at a former stage based on the input signal.

Abstract: A differential amplifier having an integrated resistance load type differential pair in which a constant current which varies to suppress a small signal gain variation of a resistance load type differential pair caused by variations of circumferential conditions and manufacturing process conditions and a constant current which varies to suppress a limiter amplitude variation of the resistance load type differential pair caused by the variations of the same conditions are mixed at a fixed ratio under a condition which is most frequently used among the circumferential conditions and a condition which is best achieved among the manufacturing process conditions, which is used as a bias current of the differential pair.

Abstract: In a variable gain amplifier controlling a gain by using differential amplifiers with a gain control signal, a gain switchover differential amplifier or a bias circuit which composes a current mirror with the gain switchover differential amplifier is connected between a high and a low gain differential amplifier for the same bias current which are mutually connected to share load resistances for the same output polarity and a bias current source common to both of the differential amplifiers, to perform switchover operations of the high and the low differential amplifier by a gain control signal, and a current source which flows a fixed offset current through at least the low one of the high and the low differential amplifier is provided.