Abstract: The invention refers to a safety procedure for optical fiber systems. Such systems are widely used in telecommunication to transport optical signals between a transmitter terminal and a receiver terminal. By the invented safety procedure the optical input power fed into said optical fiber system is automatically shut off or at least reduced in case of an unintended escape of light from at least one fiber. A safety interface, provided in the transmission line detects changes of the total optical output power in at least one fiber and initiates a shut-down of the input power as soon as a decrease of the total output power is detected, that exceeds a predefined value within a predefined time window. Thus the slope of the total output power is measured and evaluated rather than its absolute value.

Abstract: The invention relates to a system for injecting into a fiber signals from multiple sources at different wavelengths. The signals from each source are injected into the fiber by a circulator. The circulators of the various sources are cascaded. Reflector means for reflecting signals from sources previously injected are provided between each source and its circulator. The invention is used to inject signals from multiple sources without the injection of signals from one source attenuating signals from sources previously injected. It applies in particular to Raman amplification, for which purpose it provides a multiband source without attenuation between bands. Multiband amplifications is achieved without loss of gain between bands.

Abstract: The invention concerns a method for monitoring an optical waveguide between a monitoring terminal point and a monitoring unit, in which an optical data signal from a transmitter, and for amplification, pump light from a pump laser, is emitted into the optical waveguide, wherein a monitoring signal transmitted by the monitoring unit is returned via the same waveguide to the monitoring unit by a reflection device located at the monitoring terminal point, in particular a Bragg grating placed in the optical waveguide, and wherein the reflection device is tuned to a reflection that is exactly the wavelength of the monitoring signal, as well as a monitoring system and a monitoring unit for said Method.

Abstract: The invention refers to a safety procedure for optical fiber systems. Such systems are widely used in telecommunication to transport optical signals between a transmitter terminal and a receiver terminal. By the invented safety procedure the optical input power fed into said optical fiber system is automatically shut off or at least reduced in case of an unintended escape of light from at least one fiber. A safety interface, provided in the transmission line detects changes of the total optical output power in at least one fiber and initiates a shut-down of the input power as soon as a decrease of the total output power is detected, that exceeds a predefined value within a predefined time window. Thus the slope of the total output power is measured and evaluated rather than its absolute value.

Abstract: In a fiber optic link signal or pump sending power limitations due to stimulated Raman scattering are pushed back by using attenuation in the Raman gain region. Various techniques are proposed for limiting stimulated Raman scattering. In particular, the use of optical fiber lightly doped with dysprosium, the attenuation of which increases rapidly beyond 1 500 nm, is proposed. The use of this fiber to transport pump power at 1 480 nm towards remote amplifiers would enable injection of pump power up to an order of magnitude of 10 W, whereas the limit is currently 1.3 W. This technique would enable the range of links to be increased approximately 80 km.

Abstract: An optical fiber transmission system between a sender and a receiver of at least two signals with different wavelengths includes a line optical fiber and a pumping system for sending a pump signal into the line fiber to amplify the signals by distributed stimulated Raman scattering over an amplification length of the fiber. Gain equalization is applied in-line over the amplification length of the fiber so that the gain of each signal is close to the gain of the most strongly amplified signal, whereby each signal is amplified with substantially the same gain.

Abstract: The invention refers to an optical fiber transmission system, comprising a transmitter terminal 10 launching an optical signal into a fiber line, which is guiding the signal to a receiver terminal on the far end of the fiber line. The signal composed of a multitude of bit-patterns at different wavelength channels within a given total bandwidth of wavelengths. In order to increase the optical power budget of the system, the fiber line consists, in its first section, of at least two branches 12a, 12b. The transmitter 10 launches a separate part of the optical signal into each one of the branches 12a, 12b. Each part of the signal is composed of a sub-multitude of the bit-patterns at neighboring wavelength channels within non-overlapping bandwidth domains.

Abstract: WDM transmission system comprising transmitters 2 for generating optical signals in different channels, a multiplexer 3 for combining said optical signals into a WDM signals, a transmission line 4 for transmitting said WDM signal, a demultiplexer 6 for demultiplexing the WDM signal received from the transmission line 4 and receivers 7 for receiving the optical signals of each channel, characterized in that it further comprises a Raman depletion compensator 8, 10 for compensating the depletion due to Raman-shift in the power of the wavelength grid spectrum.

Abstract: In a fiber optic transmission system comprising line fiber and a pump for distributed amplification in the line fiber by stimulated Raman scattering, the line fiber comprises multiple sections and the nature of the fibers in each section and the length of each section are chosen so that the Raman gain is lower than the Rayleigh backscattering coefficient at all points of the system. This avoids the limitations that are experienced if the Raman gain is greater than the Rayleigh backscattering coefficient.

Abstract: The invention concerns a method for monitoring an optical waveguide between a monitoring terminal point and a monitoring unit, in which an optical data signal from a transmitter, and for amplification, pump light from a pump laser, is emitted into the optical waveguide, wherein a monitoring signal transmitted by the monitoring unit is returned via the same waveguide to the monitoring unit by a reflection device located at the monitoring terminal point, in particular a Bragg grating placed in the optical waveguide, and wherein the reflection device is tuned to a reflection that is exactly the wavelength of the monitoring signal, as well as a monitoring system and a monitoring unit for said Method.

Abstract: In a repeaterless optical fiber transmission system, the invention proposes providing polarization scrambling means. This makes it possible to limit the amount of energy that is transferred by the Raman effect, while increasing the amount of power that can be injected into the link. The invention is equally applicable to the lightwaves used for carrying information and to the lightwaves used for pumping.

Abstract: A system for transmission over a repeaterless optical fiber line between an emitter and a receiver terminal, the system being of the type implementing remote optical amplification and local optical amplification on reception. The remote optical amplification consists in sending a pump beam from the receiver terminal towards at least one remote section of doped fiber situated upstream in said optical fiber line, said receiver terminal including, in particular, pumping means enabling said pump beam to be generated and enabling it to be injected into said optical fiber line. The terminal also includes means for performing said local optical amplification. According to the invention, said means for implementing local optical amplification are constituted by at least one local section of doped fiber situated within said receiver terminal between said pumping means and said optical fiber line.

Abstract: Transmission line sections in a connection comprise passive portions transmitting the signal without compensating for its natural attenuation and occupying 15% to 65% of the length of the section. They also include active portions that amplify the signal. The invention is particularly applicable to making intercontinental connections.

Abstract: A telecommunications system having erbium-doped fiber optical amplifiers for transmitting signals including at least one signal at a wavelength of about 1550 nm, wherein the amplifiers are fibers whose cores are doped with erbium and germanium and are free from aluminum; and wherein for each of the amplifiers, the length of the fiber and the pumping power which is injected therein are such that the noise generated by the fiber is generally emitted around 1550 nm. As can be seen in FIG. 4 , the signal-to-noise ratio remains satisfactory after 10,000 km of propagation without using an intermediate filter.