Abstract: The method consists of first splicing (FIG. 2) one short length of a single-mode fiber (3, 4) into each of the optical fibers (1, 2) of fibers lying parallel to each other (FIG. 1), then fusing the two spliced-in single-mode fibers (3, 4) together (FIG. 3) and pulling them to form a coupler (6) (FIG. 4), and then embedding the coupler (6) in a protective housing (7) up to points beyond the splices (5).

Abstract: For short-distance communication systems, particularly for optical-waveguide links in the subscriber area, it is proposed to operate the standard single-mode optical waveguide for long-distance applications, which is optimized for the wavelength range from 1300 nm to 1600 nm, with optical transmitters and optical receivers whose operating wavelengths lie clearly below the cutoff wavelength of the optical waveguide. By means of a suitable stable laser-waveguide coupling, it is ensured that single-mode operation is achieved, which is necessary to transmit digital signals at high bit rates. The increased loss of the optical waveguide at 800 nm can be accepted because of the relatively short length of subscriber lines. Both unidirectional and bidirectional transmission over a single optical waveguide using wavelength-division or modal multiplexing is possible.

Abstract: Optical heterodyne receivers for ASK-, PSK-, FSK-, and DPSK-modulated signals are disclosed which contain a polarization controller. The receiver contains a unit (Q, Q') which works on the difference-detector principle to eliminate the shot noise of the local oscillator (LO), which emits circularly polarized light. It further includes a quadrature demodulator (D, D', D") which, besides delivering the useful signal (N), provides polarization control signals (S.sub.E, S.sub.W) with which the ellipticity and the polarization angle of the received light (E.sub.S) are adjusted in such a way that the received light (E.sub.S) is linearly polarized at an angle of 45.degree. or 135.degree..

Abstract: Optical-waveguide coils are used in rotation rate measuring instruments. To protect the optical-waveguide coil (1) from external influences, such as sound waves, pressure, and temperature changes, which may result in measurement errors, it is wound on a coil form (2) of soft elastomer under low tension. The coil unit so formed (1/2) is then placed in the annular groove (4) of a housing (3/5). Spacers at the coil form (2) position the coil unit (1/2) in the annular groove in such a way that the coil (1) is exactly in the middle of the annular groove (4). The remaining free space of the annular groove (4) is then filled with a sealing compound (6) in a vacuum. The sealing compound also spreads between the windings of the coil (1). It is preferably the same material as that from which the coil form (2) is made.

Abstract: In the rotation rate measuring instrument, two light beams traverse a coiled optical fiber (1) in opposite directions. The two beams emerging from the optical fiber are combined, and the rotation rate is determined from the Sagnac phase difference between the two beams. The optical fiber (1), which may be embedded in a sealing compound (4), is contained in a double-walled housing (8, 9) having its two walls linked by heat bridges (10, 10'). The material of the housing is a good thermal conductor. The heat bridges between the two walls are located so that external heat will act on the coiled optical fiber (1) at predetermined points.

Abstract: An optical fiber is coiled in an instrument in such a way that its beginning and its end belong to the same layer or to adjacent layers and are close together.

Abstract: In the rotation rate measuring instrument, two component beams derived from a light beam produced by a laser circulate around a coiled optical waveguide (radius R, length L) in opposite directions. From the phase difference between the two component beams due to the Sagnac effect, the rotation rate is determined. Before entering the optical waveguide, each of the two component beams is modulated in a modulator (5, 6) such that the phase differences (2.nu.+1).pi./2, (2.nu.+5).pi./2, and (2.nu.+3).pi./2 (where .nu. is an arbitrary integer) exist periodically between the two component beams emerging from the optical waveguide. The drive signals for the two modulators, which exhibit periodic frequency changes of 2F, are varied in such a way that the output of an optical-to-electrical transducer (2) to which the two component beams are directed after travelling around the optical waveguide provides a constant signal. To compensate for the Sagnac phase difference, an additional frequency difference of .DELTA.

Abstract: In the measuring instrument, a light beam generated by a laser (1) is split into two component beams (L(CW), L(CCW)) which travel along a coiled optical waveguide (7) in opposite directions. After traversing the optical waveguide, the two component beams are superimposed on each other (5) and directed to an optical/electrical transducer (8). One of the two component beams (L(CW)) is frequency-modulated in a Bragg cell (6) before entering the optical waveguide (7), switchover being effected between two modulation frequencies (f1, f2) at a given frequency (F.sub.S). The modulation frequencies are chosen so that, after traversal of the optical waveguide (7), the phase differences (.phi..sub.B1, .phi..sub.B2) between the two component beams (if the rotation rate .OMEGA.=0) are .pi./2 and 3.pi./2 or even integral multiples thereof. In case of rotation, the phase difference (.phi..sub.S) caused by the Sagnac effect is superimposed on these phase differences.