Abstract: An optical module including a substrate having a groove; an optical waveguide layer formed on the substrate, the optical waveguide layer including an optical waveguide core having first and second ends, the first end being aligned with the groove, and an optical waveguide cladding covering the optical waveguide core; a ferrule having a through hole; and an optical fiber inserted and fixed in the through hole. The ferrule has a flat cut portion for semicylindrically exposing a part of the optical fiber inserted and fixed in the through hole. The ferrule is fixed at the flat cut portion to the substrate so that the part of the optical fiber exposed to the flat cut portion is inserted into the groove of the substrate until one end of the optical fiber abuts against the first end of the optical waveguide core.

Abstract: An optical module including a substrate having a groove; an optical waveguide layer formed on the substrate, the optical waveguide layer including an optical waveguide core having first and second ends, the first end being aligned with the groove, and an optical waveguide cladding covering the optical waveguide core; a ferrule having a through hole; and an optical fiber inserted and fixed in the through hole. The ferrule has a flat cut portion for semicylindrically exposing a part of the optical fiber inserted and fixed in the through hole. The ferrule is fixed at the flat cut portion to the substrate so that the part of the optical fiber exposed to the flat cut portion is inserted into the groove of the substrate until one end of the optical fiber abuts against the first end of the optical waveguide core.

Abstract: An optical module including a substrate having a groove; an optical waveguide layer formed on the substrate, the optical waveguide layer including an optical waveguide core having first and second ends, the first end being aligned with the groove, and an optical waveguide cladding covering the optical waveguide core; a ferrule having a through hole; and an optical fiber inserted and fixed in the through hole. The ferrule has a flat cut portion for semicylindrically exposing a part of the optical fiber inserted and fixed in the through hole. The ferrule is fixed at the flat cut portion to the substrate so that the part of the optical fiber exposed to the flat cut portion is inserted into the groove of the substrate until one end of the optical fiber abuts against the first end of the optical waveguide core.

Abstract: An optical module including a substrate having a groove; an optical waveguide layer formed on the substrate, the optical waveguide layer including an optical waveguide core having first and second ends, the first end being aligned with the groove, and an optical waveguide cladding covering the optical waveguide core; a ferrule having a through hole; and an optical fiber inserted and fixed in the through hole. The ferrule has a flat cut portion for semicylindrically exposing a part of the optical fiber inserted and fixed in the through hole. The ferrule is fixed at the flat cut portion to the substrate so that the part of the optical fiber exposed to the flat cut portion is inserted into the groove of the substrate until one end of the optical fiber abuts against the first end of the optical waveguide core.

Abstract: A ferrule assembly includes a ferrule having a through-hole, a first end portion, a second end portion, and an intermediate portion between the first and second end portions, and an optical fiber inserted and fixed in the through-hole. The ferrule has at the intermediate portion a cutaway flat portion allowing the optical fiber inserted in the through-hole to be semi-exposed, and the optical fiber has its entire circumference held by the ferrule at least at the first and second end portions of the ferrule.

Abstract: An optical module including a substrate having a groove; an optical waveguide layer formed on the substrate, the optical waveguide layer including an optical waveguide core having first and second ends, the first end being aligned with the groove, and an optical waveguide cladding covering the optical waveguide core; a ferrule having a through hole; and an optical fiber inserted and fixed in the through hole. The ferrule has a flat cut portion for semicylindrically exposing a part of the optical fiber inserted and fixed in the through hole. The ferrule is fixed at the flat cut portion to the substrate so that the part of the optical fiber exposed to the flat cut portion is inserted into the groove of the substrate until one end of the optical fiber abuts against the first end of the optical waveguide core.

Abstract: An optical module including a substrate having a groove; an optical waveguide layer formed on the substrate, the optical waveguide layer including an optical waveguide core having first and second ends, the first end being aligned with the groove, and an optical waveguide cladding covering the optical waveguide core; a ferrule having a through hole; and an optical fiber inserted and fixed in the through hole. The ferrule has a flat cut portion for semicylindrically exposing a part of the optical fiber inserted and fixed in the through hole. The ferrule is fixed at the flat cut portion to the substrate so that the part of the optical fiber exposed to the flat cut portion is inserted into the groove of the substrate until one end of the optical fiber abuts against the first end of the optical waveguide core.

Abstract: An office-side optical burst receiving apparatus in for example an optical PON transmission system which solves the problem of reception failure due to a low frequency response, constituted by being provided with a pre-amplifier circuit for amplifying an output from a light receiving element, a main amplifier circuit for receiving the output signal thereof and a threshold value as differential inputs and discriminating logics "1" and "0", a threshold control circuit having a "1" level detection circuit and a "0" level detection circuit of the output signal, and a memory/calculation circuit for updating and storing the value regarding the level of the detected logic whenever a cell signal is received. It further contains an adder circuit which defines substantially a half value of a difference of levels of the logics "1" and "0" as a level value, adds the level of the logic "0" detected for the output signal now being received and the stored level, and applies the added value to the main amplifier circuit.

Abstract: A transisterized circuit may be driven with a low voltage without saturation of a direct current operating voltage point. The transisterized circuit includes a first transisterized circuit formed by a cascade connection of a first differential transisterized circuit and a first emitter follower circuit, a second transisterized circuit formed by a cascade connection of a second emitter follower circuit and a second differential transistor circuit, and an inversion circuit connected between said first transisterized circuit and said second transistor circuit.

Abstract: The present invention discloses a signal amplifier circuit used in, for example, a receive portion in an optical communication system, and including an automatic threshold value setting portion to automatically set a threshold value depending upon a "1" side level and a "0" side level of an input signal, an automatic gain control amplifying portion to take as inputs the input signal and the threshold value from the automatic threshold value setting portion so as to perform differential amplification, and a gain control portion to detect amplitude information of the input signal so as to feed a gain control signal according to amplitude of the input signal to the automatic gain control amplifying portion as a feedforward signal. It is thereby possible to avoid limitation of a signal amplified in the signal amplifier circuit at a time of reproduction of a pulse signal, and compensate for offsets present in circuits so as to suppress a variation in pulse width of the output signal.

Abstract: A burst optical signal receiver receives optical signals produced in a burst form from a predetermined subscribers. This burst optical signal receiver comprises an identifying circuit for comparing the input level of an input optical signal with a predetermined threshold value to identify the input level; a peak detector for detecting and holding the peak value of the input optical signal; a DC feedback circuit for acquiring the DC level of an output of the identifying circuit; and a circuit for producing the predetermined threshold value from the DC level from the DC feedback circuit and the peak value held in the peak detector and supplying the predetermined threshold value to the identifying circuit. The peak detector has a plurality of peak detection sections having different gains and operational dynamic ranges and causes those peak detection sections to operate in accordance with the input level of the input optical signal.

Abstract: An optical processing device for converting a wavelength of an optical signal comprises an optical processing unit supplied with an input optical beam carrying thereon one or more optical signals with respective wavelengths that are different from each other, the optical processing means being further supplied with a control optical beam having a stabilized reference wavelength and selecting the optical signal that has a first wavelength and outputting the same with a second wavelength that is specified by the reference wavelength; and a control unit for controlling the optical processing unit by specifying the first wavelength of the optical beam to be selected.

Abstract: An optical processing device for converting a wavelength of an optical signal comprises an optical processing unit supplied with an input optical beam carrying thereon one or more optical signals with respective wavelengths that are different from each other, the optical processing means being further supplied with a control optical beam having a stabilized reference wavelength and selecting the optical signal that has a first wavelength and outputting the same with a second wavelength that is specified by the reference wavelength; and a control Unit for controlling the optical processing unit by specifying the first wavelength of the optical beam to be selected.

Abstract: A method for controlling an optical amplifier that amplifies an input optical beam according to a characteristic curve. The characteristic curve changes depending on an optical power of the input optical beam, and the optical amplifier operates according to a first reference characteristic curve when an input optical beam having a first reference optical power level of the input optical beam, below which first reference optical power level a further reduction in the optical power level of the input optical beam does not produce any substantial change in the relationship of the optical gain of the optical amplifier as a function of a change in wave length of the input optical beam, and accordingly of the first reference characteristic curve; is supplied as a first reference optical power.