Abstract: The present invention provides a one-core bidirectional optical transmitting/receiving module for wavelength multiplexing, which does not require optical waveguide fabricated with high precision and which has superb high frequency characteristics and has very low optical and electrical crosstalks and available at low cost. At the middle of an optical fiber 1 buried in a glass substrate 3, a light irradiating portion is provided, which has a wavelength selection filter 2 placed obliquely to the optical fiber. The light irradiating portion is fixed immediately above a backside entrance type photodetection element 4 mounted on a ceramic substrate 6 by flip-clip bonding, and only optical signals with specific wavelength are received. An optical fiber extra portion 7 between a photodetection unit and a light emitting unit has sufficient length, and an end of the optical fiber is optically coupled with the light emitting element.

Abstract: An optic rotation sensing apparatus includes a light source emitting light. The light emitted from the light source is transmitted to a sensing loop which provides a phase difference between opposite-direction light waves in response to a rotation. Return light outputted from the sensing loop is transmitted to a photodetector. A device modulates a phase of light propagating in the sensing loop. Another device depolarizes light propagating in the sensing loop. The invention further controls and processes an output signal representing the output of the photodetector at a phase at which a level of an AM noise component of the output signal is minimized.

Abstract: A fiber-optic coil for use as the sensor loop of a fiber-optic gyroscope includes a first optical fiber segment wound as radially successive coiled layers around a coil bobbin in a first region thereof, and a second optical fiber segment wound as radially successive coiled layers around the coil bobbin in an axially adjacent second region thereof. The first and second optical fiber segments are joined to each other through a longitudinal middle portion, which is positioned in the radially innermost coiled layers of the first and second optical fiber segments adjacent to a longitudinal center of said coil bobbin. Each of the first and second optical fiber segments is wound in alternate axial directions in the radially successive coiled layers. The first and second optical fiber segments may be integrally joined to each other by the longitudinal middle portion, or may be separate from, but joined to, each other by a depolarizer across the longitudinal middle portion.

Abstract: An optical phase modulator for use with a fiber optic sensor such as a fiber optic gyroscope includes a piezoelectric vibrator which is asymmetric in at least one cross-sectional shape thereof, a pair of electrodes for applying a voltage to said piezoelectric vibrator, and an optical fiber joined to at least a portion of said piezoelectric vibrator by adhesive bonding. The piezoelectric vibrator has a cavity defined therein, and one of said electrodes is disposed on a surface of said piezoelectric vibrator which defines said axial cavity, the other electrode being disposed on an outer surface of said piezoelectric vibrator. The piezoelectric vibrator may be cylindrical, elliptically cylindrical, or planar in shape. The cavity may be cylindrical or elliptically cylindrical in shape.