Abstract: In a bidirectional optical module, a technique for attaining a miniaturization and a lower cost of a bidirectional optical module in which one optical fiber propagation path can be bused in two ways is disclosed. According to this technique, a molded product 12 is made of a transparent material, and a beam splitter layer 121 is inclined and embedded. A sub carrier 15 has a stage portion constituting an upper stage and a lower stage and is mounted on a flat top plane of a carrier 19. A semiconductor laser 14 is mounted on the upper stage of the sub-carrier, and a light receiving device 13 is mounted at a lower position of the molded product on the lower stage, and a side of the molded product is mounted on the side, and the respective planes are consequently bonded.

Abstract: An optical composite module whose optical axis can be easily adjusted, which is small-sized and has an advantage in ease of mountability. A convergent rod lens 2 with a band-pass optical filter 5 (BPF) bonded to an end thereof, and a double-core glass tube 3 housing an input optical fiber 1a and an output optical fiber 1b are secured. The double-core glass tube 3 has an outer diameter coinciding with that of the convergent rod lens 2. The center line between the input optical fiber 1a and the output optical fiber 1b coincides with an optical axis of the convergent rod lens Light with wavelength &lgr;4 output from the input optical fiber 1a passes through the BPF 5, and is received by a light-receiving element 7 and converted into an electric signal. Light with other wavelengths output from the input optical fiber 1a is reflected by the BPF 5, and coupled into the output optical fiber 1b.

Abstract: A polarization independent optical isolator for transmitting a signal ray in a forward direction and suppressing backward transmission comprises: a first and second optical isolation unit for receiving, transmitting, and outputting signal rays in the forward direction and for suppress backward transmission of any rays; and a reflection unit for coupling to first and second optical isolation unit by directing the outputted signal ray from the first optical isolation unit to the second optical isolation unit, the signal ray received by the first optical isolation unit transmitting in the opposite direction to the outputted signal ray from the second optical isolation unit. A reflection protection unit may be provided to prevent undesired reflection at inlet of the optical isolator. A optical filter for reflecting a component having a predetermined wavelength and transmitting remaining component may be used for the reflection unit. An optical detector may be used for monitoring the remaining component.

Abstract: A polarization independent optical isolator for transmitting a signal ray in a forward direction and suppressing backward transmission comprises: a first and second optical isolation unit for receiving, transmitting, and outputting signal rays in the forward direction and for suppress backward transmission of any rays; and a reflection unit for coupling to first and second optical isolation unit by directing the outputted signal ray from the first optical isolation unit to the second optical isolation unit, the signal ray received by the first optical isolation unit transmitting in the opposite direction to the outputted signal ray from the second optical isolation unit. A reflection protection unit may be provided to prevent undesired reflection at inlet of the optical isolator. A optical filter for reflecting a component having a predetermined wavelength and transmitting remaining component may be used for the reflection unit. An optical detector may be used for monitoring the remaining component.

Abstract: A polarization independent optical isolator for use in optical communication systems is provided. This optical isolator functions to provide dual-way optical isolation wherein an input optical signal entering in the isolation direction is transmitted through the optical isolator twice using a reflecting member, and includes a magnetooptic plate and a birefringent plate disposed between the magnetooptic plate and the reflecting member.

Abstract: An object of the present invention is to provide an optical passive component having a polarization-independent optical isolator for constituting an optical fiber amplifier and exhibiting an optical isolator function. At least first and second optical fibers for input and output of light rays, a birefringent crystal, a lens for converting the input light rays into nearly collimated rays, a magnetooptical crystal for receiving a magnetic field so as to rotate by .pi./8+N.pi./4(n=0, 1, . . . ) the polarization direction of the input light rays, and a reflector are disposed in order. A half wave plate is provided to cover one portion of the ray path between the above described birefringent crystal and the above described lens.

Abstract: On one end side of a converging rod lens are provided a first and second input optical fibers and a first and second output optical fibers. On the other end side of the converging rod lens is provided a reflecting mirror. Between the converging lens and the first and second input and output optical fibers is provided a birefringent element for resolving a ray which passes therethrough into an ordinary ray and an extraordinary ray. In the optical paths of the first and second output optical fibers between the converging rod lens and birefringent element is placed a compensator for rotating 45 degrees the plane of polarization of a ray which passes therethrough. The reflecting mirror reflects incident rays from the first and second input optical fibers to the first and second output optical fibers. Between the converging rod lens and the reflecting mirror is provided a magneto-optical element for rotating 22.5 degrees the plane of polarization of a ray which passes therethrough.

Abstract: Optical passive components comprising: a first optical fiber for outputting pumping light; a second optical fiber for receiving the pumping light and either outputting or receiving signal light; a third optical fiber for either receiving or outputting the signal light; a wavelength selecting filter which transmits therethrough the pumping light and reflects the signal light; a mirror which reflects most of the signal light reflected by the wavelength selecting filter and transmits therethrough a portion of the signal light reflected by the wavelength selecting filter such that the wavelength selecting filter and the mirror form an optical assembly; an optical isolator which passes therethrough the signal light reflected by the mirror so as to output the signal light; and a semiconductor optical detecting device for detecting the signal light transmitted through the mirror; wherein the first, second and third optical fibers are disposed at one side of the optical assembly.

Abstract: An optical fiber amplifier suited for use in optical fiber transmission systems includes a plurality of optical passive components. The optical passive components are integrated into an assembly including a birefringent crystal, a first lens, a magneto-optic crystal, an optical filter, and a second lens, all of which are axially aligned in this order, with a half-wave plate interposed between the birefringent crystal and the first lens. The birefringent crystal is opposed to end faces of first and second optical fibers and separates incident light into two linearly polarized light beams having respective polarized light planes generally perpendicular to each other. The half-wave plate allows light emitted from the second optical fiber to pass therethrough and rotates a polarized light plane of incident light. The first lens converts incident light into a generally collimated ray, and the magneto-optic crystal rotates a polarized light plane of incident light by an angle of .pi./8+Nn/4 (N=0, 1, 2, . . .