Abstract: In a method of amplitude equalization of a plurality of optical signals having mutually different wavelengths, the optical signals are launched into a first end of an optical fiber (5). The optical signals are amplified, before being launched into the fiber (5), to a level at which at least one of the signals exceeds a stimulated Brillouin scattering (SBS) threshold value (TSBS) characteristic of the fiber, so that part of the signal energy in the fiber is transferred to a Stokes signal propagating in the fiber (5) in a direction opposite to said optical signals. An apparatus for amplitude equalization of a plurality of optical signals having mutually different wavelengths comprises an optical fiber (5) having an input end (6) where said optical signals may be supplied to the fiber, and an output end (10) where said optical signals may be tapped from the fiber after equalization.

Abstract: In a method of amplitude equalization of a plurality of optical signals having mutually different wavelengths, the optical signals are launched into a first end of an optical fiber (5). The optical signals are amplified, before being launched into the fiber (5), to a level at which at least one of the signals exceeds a stimulated Brillouin scattering (SBS) threshold value (TSBS) characteristic of the fiber, so that part of the signal energy in the fiber is transferred to a Stokes signal propagating in the fiber (5) in a direction opposite to said optical signals. An apparatus for amplitude equalization of a plurality of optical signals having mutually different wavelengths comprises an optical fiber (5) having an input end (6) where said optical signals may be supplied to the fiber, and an output end (10) where said optical signals may be tapped from the fiber after equalization.

Abstract: An optical amplifier comprises an active fiber (1) a pump unit (2) spaced from the active fiber and adapted to give a nominal, continuous pump power in an operational state, and a pump fiber (3) adapted to transfer optical pump power from the pump unit (2) to the active fiber (1). Moreover, in a safety state, the pump unit (2) is adapted to give a pulsed pump power whose mean power is lower than a prescribed safety limit. A method of preventing emission of optical power exceeding a prescribed safety limit on interruption of an optical fiber (3) which transfers pump power from a pump unit (2) to an active fiber (1), comprises changing the mean power of the pump power in response to a signal received from the active fiber (1) so that the mean power assumes a value below said safety limit if said signal is not received, and assumes a nominal value if said signal is received.

Abstract: In a method of amplitude equalization of a plurality of optical signals having mutually different wavelengths, the optical signals are launched into a first end of an optical fiber (5). The optical signals are amplified, before being launched into the fiber (5), to a level at which at least one of the signals exceeds a stimulated Brillouin scattering (SBS) threshold value (TSBS) characteristic of the fiber, so that part of the signal energy in the fiber is transferred to a Stokes signal propagating in the fiber (5) in a direction opposite to said optical signals. An apparatus for amplitude equalization of a plurality of optical signals having mutually different wavelengths comprises an optical fiber (5) having an input end (6) where said optical signals may be supplied to the fiber, and an output end (10) where said optical signals may be tapped from the fiber after equalization.

Abstract: An optical amplifier comprises an active fiber (1), a pump unit (2) spaced from the active fiber and adapted to give a nominal, continuous pump power in an operational state, and a pump fiber (3) adapted to transfer optical pump power from the pump unit (2) to the active fiber (1). Moreover, in a safety state, the pump unit (2) is adapted to give a pulsed pump power whose mean power is lower than a prescribed safety limit.

Abstract: An optical amplifier comprises an active fiber (1), a pump unit (2) spaced from the active fiber and adapted to give a nominal, continuous pump power in an operational state, and a pump fiber (3) adapted to transfer optical pump power from the rump unit (2) to the active fiber (1). Moreover, in a safety state, the pump unit (2) is adapted to give a pulsed pump power whose mean power is lower than a prescribes safety limit. A method of preventing emission of optical power exceeding a prescribed safety limit on interruption of an optical fiber (3) which transfers pump power from a pump unit (2) to an active fiber (1), comprises changing the mean power of the pump power in response to a signal received from the active fiber (1) so that the mean power assumes a value below said safety limit if said signal is not received, and assumes a nominal value if said signal is received.

Abstract: In a method of measuring on an optical fibre (2), a pulse is launched into the fibre, and the temporal course (8, 9) of the echo of this pulse is measured. Then, a signal level representing the background noise present in the fibre is subtracted in a subsequent signal processing of the echo signal. The signal level representing the present background noise is calculated on the basis of the instantaneous value (20) of the background noise which it assumes during the measurement of the echo signal. In a first embodiment the background noise is measured at a wavelength different from the wavelength of the emitted pulse. In a second embodiment wherein several successive pulses (25, 26) are launched into the fibre, optical power (27) is launched into the fibre at a wavelength other than the pulse wavelength during the intervals between said pulses.