Abstract: An optical transmission system for transmitting an optical signal through an optical fiber transmission line includes a first optical fiber transmitting the optical signal and having a first zero-dispersion wavelength shorter than a wavelength of the optical signal, and a second optical fiber transmitting the optical signal from the first optical fiber and having a second zero-dispersion wavelength longer than the wavelength of the optical signal. A first nonlinear effective cross-sectional area of the first optical fiber is larger than a second nonlinear effective cross-sectional area of the second optical fiber.

Abstract: The invention relates to a system and method for determining wavelength dependent information in optical signal transmission systems. According to the invention after a plurality of optical signals at different wavelengths are launched into the transmission system, backscattered and/or reflected signal portions are received for each wavelength, and subsequently processed to determine wavelength dependent information about the transmission system. With the present invention the gain evolution along the transmission link can be measured, after the transmission system is installed. In particular this is advantegous for submarine optical signal transmission systems.

Abstract: The present invention provides a method of dispersion compensation comprising the steps of:

Abstract: A drop/insert apparatus for dropping/inserting channels on a both-way multi-channel optical link includes a "line" optical fiber serving to convey optical signals in two opposite transmission directions, over at least two channels having distinct wavelengths per transmission direction.

Abstract: A process for locating a fault on an optical transmission link using a coherent detection reflectometer at a terminal sends over the transmission link measuring pulses and a loading signal interleaved between the measuring pulses. The loading signal is chosen to have the same optical wavelength as the measuring pulses with which it is combined and an extended bandwidth such that the power that it develops in the narrow measuring band of the reflectometer is negligible compared to that developed by the measuring pulses.

Abstract: A system is disclosed for monitoring repeaters of an installation for transmission of signals via optical conductors in which each repeater includes an optical amplifier for amplifying the signals transmitted by the optical conductors. A remote monitoring signal is transmitted from a main or monitoring center to each repeater. The system includes, at the main center, a remote monitoring signal transmitter having a wide spectrum of optical wavelengths, preferably at least as wide as the wanted spectrum of wavelengths of the optical signals transmitted on the conductors. In this way the wanted signal is virtually undisturbed by the remote monitoring signal.

Abstract: In an optical communication system using polarization scrambling of the transmitted optical signal, the scrambling causes the polarization vector to rotate. The scrambler includes a modulator to modulate either the phase or the wavelength of the optical signal. A polarization dispersion device converts the phase modulation or wavelength modulation into polarization modulation. This polarization dispersion device consists of the optical communication fibers on the output side of the modulator.

Abstract: A tunable optical filter tuning device suitable for use in the receive part of an optical transmission system rejects some of the optical noise superimposed on a wanted optical signal. The device commands displacement of the characteristic of the optical filter along the wavelength axis and includes a tuning detector to detect the time at which this displacement can be stopped. The tuning detector includes an optical power detector receiving a signal from the optical filter and detects any modulation of a signal from the optical power detector. The displacement is stopped when the detector detects modulation of the signal from the optical power detector.

Abstract: This bidirectional transmission system, especially one using optical fiber, between a source terminal and a user terminal employing a single carrier for both transmission directions obtained from a source in the source terminal characterized in that it comprises for each transmission direction means for modulating one parameter of said carrier, this parameter being intensity for the two directions and subject in all cases to the condition that the modulation applied first for transmission in the downward direction from the source terminal to the user terminal the depth of modulation is sufficiently high to leave sufficient power for application of the second modulation to which that applied second can be applied for transmission in the upward direction from the user terminal to the source terminal.