Abstract: An optical repeater for an optical digital transmission line has a pair of in-service monitoring circuits (55, 55') each of which includes a flip-flop (57) for dividing frequency of transmission data to derive commands and burst carrier in the first line (54). A counting means (59, 61) is provided for detecting parity errors and counting the errors in an opposite second line (65). A timing generation means (62) is provided for reading out the counting means (61) upon receipt of the burst carrier. A phase modulator (64) provides phase modulation to a clock pulse in an opposite second line (65) according to the output of the timing generation means (62). The number of errors in the second line (65) is stored in the counting means (61) according to commands in a first line (54) from a terminal transmitter (52). The content of the counting means (61) is forwarded to a terminal receiver (66) through phase modulation of clock pulses in a second line (65) upon receipt of the burst carrier.

Abstract: An anchoring structure is disclosed for connecting to a casing of an optical submarine repeater or a cable joint box an optical submarine cable which is composed of a cylindrical pressure proof layer formed by a combination of three deformed metal wires of the same sectorial cross-section and disposed inside an insulator so that the pressure proof layer has centrally thereof a circularly-sectioned optical fiber unit housing space for housing an optical fiber unit formed by at least one optical fiber, a cable tensile-strength member formed by a plurality of tensile-strength wires disposed concentrically with the cylindrical pressure proof layer on the outside thereof and a metallic tape layer disposed in a cylindrical form outside the tensile-strength member to extend in its axial direction, the seam of the metallic tape layer being welded and the insulator being disposed outside the metallic tape layer.

Abstract: An optical fiber submarine cable, which is provided with at least one coated optical fiber, a power supplying, pressure resisting layer of a pipe-like configuration, a tension resisting wire layer formed of a conductive material of relatively low conductivity and disposed in close contact with the power supplying, pressure resisting layer of the pipe-like configuration, and an insulator layer disposed around the tension resisting wire layer. The power supplying, pressure resisting layer is formed as at least one inner layer and an outer layer.

Abstract: An optical fiber submarine cable, in which a multilayer, cylindrical pressure resisting layer is prepared so as to have a construction in that at least one optical fiber layer is successively covered by a cushion layer and a rounded layer of a first tape of a good electric conductor member, a longitudinal joint of side edges of the first tape is welded, at least one second tape of a good electric conductor material is closely coated on the layer of the first tape by the use of an adhesive binder layer therebetween, and a longitudinal joint of the side edges of the second tape is welded.

Abstract: A submarine optical fiber cable using a low-loss optical fiber as a transmission medium, which is provided with a cylindrical pressure resisting layer composed of an assembly of three equally divided long pressure resisting segments of fan-shaped sections with flat contact planes and having at least one optical fiber in an optical fiber housing space formed in the center of the assembly so as to protect the optical fiber from a high water pressure.

Abstract: A light dispersion measuring apparatus, provided with a light source for generating reference light pulses of short duration and of a constant frequency and also variable-frequency light pulses in synchronization with the reference light pulses but at a frequency different therefrom. A variable optical delay line delays the reference light pulses. An optical transmission medium, to be detected and to which the variable-frequency light pulses are applied is provided. An optical non-linear effect element receiver the output light pulses from the variable optical delay line and the optical transmission medium and is disposed so that when the two light pulses coincide emitted from the light source with each other, the sum component of the frequencies of the two types of light pulses produces a maximum output. A photo detector detects the sum component.

Abstract: The operation of a laser in an optical repeater in an optical transmission system using an optical fiber cable is telemonitored at a terminal station by changing the mark ratio of the test signal which is transmitted from the terminal station to the circuit.

Abstract: An optical loss in a single mode optical device is measured by utilizing multi-mode equipment. The present system comprises of an optical source (1), a sample (30) to be tested, a reference optical attenuator (31) for replacing the optical loss in the sample (30), a first optical switch (40) provided between the optical source (1) and the sample (30) through a single mode optical fiber, a second optical switch (41) provided between the sample (30) and the light receiver (2) through the multi-mode optical fiber, said reference optical attenuator (31) being provided between the first optical switch (40) and the second optical switch (41) so that the optical path is switched either to the sample (30) or to the reference attenuator (31), the optical fiber between the sample (30) and the second optical switch (41) and the optical fiber connected to the input and the output of the reference attenuator (31) being a multi-mode optical fiber.

Abstract: An optical fiber feedthrough for an optical submerged repeater for use in an optical fiber submarine cable, in which a metal film is coated on the outer peripheral surface of an optical fiber to be introduced into the repeater, and in which a thermoplastic material, such as polyethylene or the like, is filled between the inner wall of a hole made in an end face plate of a pressure resisting container of the repeater and the metal film.

Abstract: The error rate and the operation of repeaters inserted in an optical transmission line are monitored at the terminal station on land by transmitting the test signal and monitoring the response signal of repeaters through the optical data transmission line without utilizing interstitial copper pair. Each repeater has the particular identification code, and the transmission terminal transmits the test code having the repeater identification code and an acknowledgement block with an empty bit position on the time divisional basis with the data to be transmitted. The repeater which finds his identification code in the test code, inserts the response in the acknowledgement block, and repeats the signal including both said test code and the data to be transmitted. The reception terminal analyzes the response signal of each repeater to determine the error rate of each repeaters.

Abstract: An optical-fiber submarine cable, in which a combination is provided by a thin, cylindrical pressure resisting sheath, and a reinforcing member of a cross section inserted by the thin, cylindrical pressure resisting sheath so as to divide the circular cross section of the pressure resisting sheath into a plurality of spaces and to have a required withstand pressure; and in which at least one low-loss optical fiber is inserted in each of the plurality of spaces. The combination can be fabricated by separately paying out the reinforcing member and the thin, cylindrical pressure resisting sheath, or by curving inwardly a sheet of tape being paid out.

Abstract: In a long line transmission system, the signal level at the transmission station is pre-equalized by the value L.sub.s which is adjustable according to the signal level at the receiving station. The receiving station equalizes the received signal to the standard level at the output of the receiving station. The difference between the actual level L.sub.r at the input of the receiving station and the standard level there, is fed back to the transmission station through a return transmission line, and said difference is utilized to adjust the pre-equalization value L.sub.s at the transmission station. The ratio L.sub.s /L.sub.r is controlled to be constant by the operation of the pre-equalization level distributor installed at the transmission station.

Abstract: A system equalizer and a method of equalization employed in a repeatered submarine cable system, in which automatic gain controlled (AGC) submerged repeaters are employed to compensate for fluctuations of the cable loss caused by the temperature fluctuations in the surrounding environment of the repeatered submarine cable system. In a terminal equipment connected to the repeatered submarine cable system, the seasonal misalignment of the repeatered cable system is equalized by a switchable equalizer having a loss-frequency characteristic corresponding to the total of compensation errors in the AGC submerged repeaters. Short-term level fluctuations of the repeatered cable system are compensated by an automatic equalizer, which has a loss-frequency characteristic proportional to the square root of frequency f and is controlled by the level of a pilot signal transmitted through the repeatered submarine cable system. An unknown fixed deviation is finally equalized by a second adjustable equalizer.