Abstract: System and method for dispersion compensation tuning for a WDM optical transmission system. A tunable dispersion compensation module (4) is located at or substantially close to a transmitting end of the optical transmission line (2) and at least one distributed Raman amplifier having an Raman pump (1) is coupled to the transmission line 2. The dispersion compensation is controlled by means of a signal derived from the Raman pump (1) which is fed through a control loop (3) to the tunable dispersion compensation module (4).

Abstract: System and method for dispersion compensation tuning for a WDM optical transmission system. A tunable dispersion compensation module (4) is located at or substantially close to a transmitting end of the optical transmission line (2) and at least one distributed Raman amplifier having an Raman pump (1) is coupled to the transmission line 2. The dispersion compensation is controlled by means of a signal derived from the Raman pump (1) which is fed through a control loop (3) to the tunable dispersion compensation module (4).

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: A device (D) for amplifying optical signals is connected to an optical fiber (3) conveying an optical data signal and delivers into said optical fiber first and second optical pump signals at different wavelengths for amplifying the data signal by stimulated Raman scattering. Each pump signal comprises two pump signal components whose polarizations are mutually orthogonal. Moreover, the amplification device D comprises a control module 14 for delivering alternately a first combined pump signal and a second combined pump signal, the first combined pump signal comprising a component of the first pump signal and a component of the second pump signal that have mutually orthogonal polarizations and the second combined pump signal comprising the other component of the first pump signal and the other component of the second pump signal.

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: In a method of optically amplifying signals between a sender station and a receiver station connected by an optical fiber, the power of a primary optical signal circulating between the sender station and the receiver station is amplified in the fiber by first order stimulated Raman scattering by first and second secondary optical pump signals having first and second wavelengths and circulating between the sender station and the receiver station, the first and second secondary signals are modulated, and at least a first tertiary optical signal having a third wavelength adapted to amplify the power of the first and second secondary signals by second order stimulated Raman scattering is transmitted in the fiber between the sender station and the receiver station.

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: A method of making an optical transmission system safe, the system including a transmission optical fiber and emitting an optical wanted signal, transmitting a transmitted optical signal containing the wanted optical signal and optical noise, sampling a portion of the transmitted optical signal constituting a monitoring optical signal, and analyzing the power of the monitoring optical signal to deduce, as a function of the power of the monitoring optical signal, whether the transmission optical fiber is broken. The method isolates in the monitoring optical signal a first signal containing only the noise and a second signal containing the noise and the wanted signal and compares the power of the first and second signals and to deduce that the transmission optical fiber is broken if the ratio of the power of the second signal to the power of the first signal is substantially equal to 1.

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: The invention provides a circuit for amplitude modulating an optical signal with an N-state electrical signal where N is greater than or equal to 2, the circuit comprising a modulator having a first input for receiving the optical signal to be modulated and a second input for receiving a modulating electrical signal. According to the invention, the circuit comprises, upstream from the second input, shaping component having an input receiving the N-state electrical signal and having an output that switches from one of the N states to another of the N states in response to the N-state electrical signal taking up a level that is greater than a predetermined threshold, and switching from the other state to the one of the N states in response to the N-state electrical signal taking up a level that is less than the predetermined threshold, the predetermined threshold being associated with the pair of states, and having a level that lies between and is different from the respective levels taken by the two states.