Abstract: Apparatus and method for gain measurement and control of a Distributed Raman Amplifier (DRA). Various embodiments of the apparatus include a detection unit operative to measure, during operation of the DRA, the optical power of a filtered component of the light entering the DRA from the transmission fiber and a gain calculation and control unit coupled to the detection unit and operative to calculate a signal Raman gain property from the measured optical power. The filtered component may exemplarily be a result of passing the light through a band pass filter, a spectral filter with a given spectral shape or a notch filter. The signal Raman gain property may be an average on-off signal Raman gain, an average net signal Raman gain or a signal Raman gain tilt within a communication band. The apparatus and method may be used to operate the DRA in Automatic Gain Control, i.e. to maintain a required constant signal Raman gain and/or signal Raman gain tilt.

Abstract: Apparatus and method for gain measurement and control of a Distributed Raman Amplifier (DRA). Various embodiments of the apparatus include a detection unit operative to measure, during operation of the DRA, the optical power of a filtered component of the light entering the DRA from the transmission fiber and a gain calculation and control unit coupled to the detection unit and operative to calculate a signal Raman gain property from the measured optical power. The filtered component may exemplarily be a result of passing the light through a band pass filter, a spectral filter with a given spectral shape or a notch filter. The signal Raman gain property may be an average on-off signal Raman gain, an average net signal Raman gain or a signal Raman gain tilt within a communication band. The apparatus and method may be used to operate the DRA in Automatic Gain Control, i.e. to maintain a required constant signal Raman gain and/or signal Raman gain tilt.

Abstract: A system and method for providing eye-safety protection during operation of a lumped optical amplifier. The method is based on monitoring of continuous out-of-band Raman amplified spontaneous scattering (ASS) created by the amplified signal in an optical communication network span coupled to an output port of the lumped optical amplifier. The system includes at least one gain stage for providing an amplified signal introduced into the span, a monitoring unit for performing the continuous Raman ASS monitoring, and a control unit operative to detect and analyze in real-time changes in the ASS power, and upon determination that such changes indicate an open span, to reduce the power of the amplified signal or shut down the gain stage.

Abstract: Efficient wavelength calibration in a WDM optical amplifier that includes an optical channel monitor (OCM) is obtained by introducing a notch into the amplified spontaneous emission (ASE) noise spectrum of the amplifier outside a WDM transmission band, and having the OCM detect the notch and use the notch as a reference to calibrate the wavelength measurement. The notch is introduced into the ASE noise spectrum using a notch filter, which is preferably incorporated in a gain flattening filter (GFF).

Abstract: Efficient wavelength calibration in a WDM optical amplifier that includes an optical channel monitor (OCM) is obtained by introducing a notch into the amplified spontaneous emission (ASE) noise spectrum of the amplifier outside a WDM transmission band, and having the OCM detect the notch and use the notch as a reference to calibrate the wavelength measurement. The notch is introduced into the ASE noise spectrum using a notch filter, which is preferably incorporated in a gain flattening filter (GFF).

Abstract: A system and method for providing eye-safety protection during operation of a lumped optical amplifier. The method is based on monitoring of continuous out-of-band Raman amplified spontaneous scattering (ASS) created by the amplified signal in an optical communication network span coupled to an output port of the lumped optical amplifier. The system includes at least one gain stage for providing an amplified signal introduced into the span, a monitoring unit for performing the continuous Raman ASS monitoring, and a control unit operative to detect and analyze in real-time changes in the ASS power, and upon determination that such changes indicate an open span, to reduce the power of the amplified signal or shut down the gain stage.

Abstract: An apparatus for optical amplification that imparts to a narrow band optical amplifier, specifically an Erbium dope fiber amplifier (EDFA), gain properties found in wide band optical amplifiers. In one preferred embodiment, the apparatus comprises an EDFA and an externally attachable (to the EDFA) module that includes a single un-pumped Erbium doped fiber (EDF) connected to a gain flattening filter (GFF). The GFF may be internal or external to the module. In another embodiment, the apparatus comprises an EDFA and an externally attachable module having a plurality of un-doped EDFs with different lengths, switchably connectable to the GFF and the EDFA to provide the required wide-band gain properties.

Abstract: An apparatus for optical amplification that imparts to a narrow band optical amplifier, specifically an Erbium dope fiber amplifier (EDFA), gain properties found in wide band optical amplifiers. In one preferred embodiment, the apparatus comprises an EDFA and an externally attachable (to the EDFA) module that includes a single un-pumped Erbium doped fiber (EDF) connected to a gain flattening filter (GFF). The GFF may be internal or external to the module. In another embodiment, the apparatus comprises an EDFA and an externally attachable module having a plurality of un-doped EDFs with different lengths, switchably connectable to the GFF and the EDFA to provide the required wide-band gain properties.

Abstract: An apparatus for optical amplification that imparts gain properties found in wide-band optical amplifiers to a narrow-band optical amplifier, specifically an Erbium doped fiber amplifier (EDFA). In one preferred embodiment, the apparatus comprises an EDFA and an externally attachable (to the EDFA) module that includes a single un-pumped Erbium doped fiber (EDF) connected to a gain flattening filter (GFF). The GFF may be internal or external to the module. In another embodiment, the apparatus comprises an EDFA and an externally attachable module having a plurality of un-doped EDFs with different lengths, switchably connectable to the GFF and to the EDFA to provide the required wide-band gain properties.

Abstract: A method and apparatus for dynamically obtaining a substantially linear gain tilting of the output spectrum of an EDFA, in either automatic gain control or automatic power control modes. A necessary tilt is obtained while holding the total gain or total output power of the EDFA constant. The apparatus includes a variable mid-stage attenuator inserted between two (first and second) gain sections of the EDFA. The tilting is performed by ordering the attenuator to increase or decrease its attenuation in a value proportional to the tilting needed, while changing substantially simultaneously the pumping of the second gain section. The attenuation change process is based on the saturation mechanism of the erbium amplifier in the L-band, which translates the wavelength-independent loss of a variable optical attenuator into a linear wavelength-dependent gain at the EDFA output.