Abstract: A variable optical attenuator is constituted of input/output optical systems, a birefringent member provided at output sides of the input/output optical systems, a liquid-crystal member capable of individually varying polarizing states of input beams exiting the birefringent member, and a reflection member which reflects light passing through the liquid-crystal member, to thereby cause the light to return to an output lens of the input/output optical systems by way of the liquid-crystal member and the birefringent member. Thus, there can be provided a variable optical attenuator which is more compact and less expensive than a related-art variable optical attenuator.

Abstract: There provided a small low-cost optical monitor device. In this optical monitor device, input fibers and output fibers are arranged in an array on one side, first lenses are arranged in an array on the optic axes of input optical signals outputted from the input fibers, and second lenses are arranged in an array on the optic axes of output optical signals inputted to the output fibers. Input optical signals is inputted to a coupler film via the first lenses and optical signals which pass through the coupler film will be detected by front incidence type PD elements. On the other hand, output optical signals reflected from the coupler film are inputted to the second lenses separate from the first lenses, from which the input optical signals were outputted, and are coupled to the corresponding output fibers. As a result, a reflection and loop back structure is realized. In this reflection and loop back structure, a plurality of input optical signals are reflected accurately by a coupler film and are outputted.

Abstract: A variable optical attenuator is constituted of input/output optical systems, a birefringent member provided at output sides of the input/output optical systems, a liquid-crystal member capable of individually varying polarizing states of input beams exiting the birefringent member, and a reflection member which reflects light passing through the liquid-crystal member, to thereby cause the light to return to an output lens of the input/output optical systems by way of the liquid-crystal member and the birefringent member. Thus, there can be provided a variable optical attenuator which is more compact and less expensive than a related-art variable optical attenuator.

Abstract: An optical module includes a first level detecting part having a semi-transparent structure and receiving a light signal emitted from a light-emitting element, a second level detecting part receiving the light signal which penetrates through the first level detecting part and passes through an optical filter, and a control part controlling an operation temperature of the light-emitting element on the basis of electric signals output from the first and second level detecting parts.

Abstract: An optical receptacle module includes an optical module unit including therein an optical device and carrying a sleeve, a ferrule holder fitted into the sleeve and holding therein a ferrule, a frame member mounted on the ferrule holder, and an adapter unit mounted on the frame unit and accepting an external optical plug, wherein the ferrule holder having an engagement part for engagement with the frame at a location away from the optical device with respect to an engagement part of the frame member used for engagement with the adapter unit.

Abstract: An optical transmitting/receiving module including a light emitting element, a light receiving element, a transmitting optical communication line for transmitting an optical signal, a receiving optical communication line for receiving an optical signal, and a single aspherical lens for coupling the transmitting light emitted from the light emitting element to the transmitting optical communication line and for coupling the receiving light emergent from the receiving optical communication line to the light receiving element. The light emitting element is arranged so that the center line of a beam of the transmitting light emitted from the light emitting element is inclined with respect to the optical axis of the lens. With this arrangement, the optical transmitting/receiving module can be reduced in size.

Abstract: A compact, low-cost combined transmitting/receiving optical communications module, which is suitable for use in a TCM system and which is capable of normal operation over a particularly wide temperature range in optical communications equipment, is provided. The optical transmitting/receiving section for this purpose has a laser diode which outputs a transmitted optical signal, a combined monitor/receiving photodiode which not only monitors the optical output signal from the laser diode during a transmitting period, but also receives the input optical signal from the transmission path during the receiving period, and an optical mixer/divider which performs transmitting/receiving mixing and dividing between the transmission path, the laser diode, and the photodiode.

Abstract: An optical parallel receiving module receives optical signals transmitted in parallel in a plurality of channels by using optical fibers. The optical parallel receiving module includes photo-electric conversion elements for converting received signals which are electric signals as received signals, limiter amplifiers for comparing the received signals and a threshold level, and data decision circuits for recognizing data at a timing in every period of received data using a reference clock.

Abstract: An optical module for two-way transmission includes a lens for converging a received light from an optical fiber, and a photodiode for sensing the converged received light. A laser diode outputs a transmitted light, and a prism shifts the optical path of the transmitted light converged by the lens, and inputs the transmitted light to the optical fiber.

Abstract: A compact size optical multiplexer and demultiplexer module. The optical multiplexer and demultiplexer module includes a multiplexing and demultiplexing film disposed on an end surface of a waveguide substrate, having an optical waveguide formed thereon, on which surface an input and output end of the optical waveguide appears. The multiplexing and demultiplexing film transmits a light beam of wavelength .lambda..sub.1 and reflects a light beam of wavelength .lambda..sub.2. A first optical fiber is disposed such that a light beam with the wavelength .lambda..sub.1 propagated therethrough is coupled to the input and output end of the waveguide substrate after being transmitted through the multiplexing and demultiplexing film and the second optical fiber is disposed such that a light beam with the wavelength .lambda..sub.2 propagated therethrough is coupled to the first optical fiber after being reflected by the multiplexing and demultiplexing film. A light beam with the wavelength .lambda..sub.

Abstract: Disclosed herein is a duplicated light source module constructed so that rays of light emitted from two light sources pass through one lens and then enter one optical fiber through a birefringent element. This module is useful when a light source in an optical transmitter is intended to be duplicated or when a high-power pumping source in an optical fiber amplifier is required.

Abstract: A ball lens assembly constructed of a lens holder formed with a press-fit hole having a circular section and a ball lens press-fitted with the press-fit hole of the lens holder. The lens holder is formed by sintering stainless steel powder. As the lens holder is formed by sintering, a force for press-fitting the ball lens into the lens holder can be suppressed to thereby effectively prevent breakage of the ball lens.

Abstract: A device which includes a polarizer wherein one of a pair of transmission faces of a transparent substrate by a light beam on which a polarizing separating film is not formed is formed in an inclined relationship with respect to the other transmission face of the transparent substrate on which the polarizing separating film is formed and a parallel light beam having a predetermined incident angle with respect to the polarizing separating film is passed through the polarizing separating film to effect polarized light separation. Two such devices are provided and a Faraday rotator is provided between the two devices to constitute an optical isolator.

Abstract: A ferrule having an optical fiber connected thereto and a spherical lens are fixed in a cylindrical lens holder to form a fiber collimator. The thickness of a cylindrical wall of the lens holder is made smaller at a spherical lens receiving portion than the other portion and the cylindrical lens holder is fixed to a substrate by welding. A pair of such fiber collimators are provided in an opposing relationship to each other on the substrate, and an optical function element is disposed between the opposing fiber collimators to form an optical device. By provision of a light path changing over mechanism as such optical function element, an optical switch of a small size having a high performance can be provided.

Abstract: A wavelength-division multiplexing optical transmission system is disclosed which transmits light of wavelengths .lambda..sub.1, .lambda..sub.2 and .lambda..sub.3 (.lambda..sub.1 <.lambda..sub.2 <.lambda..sub.3) by way of a single optical fiber. An optical multiplexer/demultiplexer of the filter type is used which includes a parallelogram prism, a first filter formed on a side face of the parallelogram prism, and second and third filters formed on the opposite side face of the parallelogram. Bidirectional optical fiber communications between the central telephone exchange side and a subscriber side can be achieved using such optical multiplexer/demultiplexer of the filter type. With the arrangement of the invention, an optical multiplexer/demultiplexer of the filter type can be produced at a low cost without the necessity of using a filter having a wide stopping band as a filter to be formed on a parallelogram prism.