Cisco Technology, Inc.

Corning O.t.i. Spa

Ericsson Ab

Marconi Communications Gmbh

Pirelli Cavi E Sistemi S.p.a.

Corning O.t.i. Inc.

Giovanni Sacchi

Fabrizio Di Pasquale

Fausto Meli

Roberta Castagnetti

Silvia Turolla

Giorgio Grasso

Antonella Bogoni

Antonio D'Errico

Giacomo Antonio Rossi

Guido Oliveti

Paolo Vavassori

Valeria Gusmeroli

Fabrizio DiPasquale

Simone Sugliani

Paolo Gurnari

Alberto Zermani

Marco Angellieri

Antonio D'ERRICO

A Raman pump module for generating pump radiation having a pump wavelength (&#x3bb;) for coupling into a transmission fiber of an optical wavelength division multiplex (WDM) communication system to provide Raman amplification of WDM radiation counter propagating therethrough is disclosed. The pump module is for use in a communications system in which the WDM radiation has a transmission waveband (&#x3bb;) and wherein the transmission fiber has a zero dispersion wavelength (&#x3bb;) lying midway between the transmission waveband and the pump wavelength. The module comprises a Raman pump laser for generating the pump radiation and a de-correlator for de-correlating the longitudinal modes of the pump radiation before it is coupled into the transmission fiber.

Counter-pumped distributed Raman amplification in wavelength division multiplex optical communication systems

A looped WDM optical network comprises an optical loop with optical amplifiers () between the sections of the loop () and with ASE recirculation in the loop. At a point of the loop a laser beam is injected and allowed to circulate in the loop with the laser beam being centered around a &#x3bb;wavelength where it is desired that a lasing peak be generated. This supplies high network strength in terms of section loss variations and greatly improves the OSNR of the WDM signal. High network survivability is also achievable.

Looped optical network with ASE light recirculation and link and network survivability control system

An approach for automatic Raman gain and tilt control for a WDM (Wavelength Division Multiplexing) optical communication systems is disclosed. An optical fiber carries a plurality of optical signals, in which at least one of the optical signals are reference signals. An optical gain unit (e.g., Raman pump unit) couples to the optical fiber and adjusts the reference signals to compensate, in part, for losses associated with the optical fiber and gain tilt accumulation. Upon detecting and analyzing the reference signals, a controller controls the optical gain unit and outputs a control signal to the optical gain unit based upon the analyzed reference signals. An optical amplifier is connected to the optical fiber and amplifies the optical signals. The optical gain unit provides a nearly constant power per channel at an input of the optical amplifier. Under this approach, a Raman gain control mechanism, combined with the use of gain controlled EDFA (Erbium Doped Fiber Amplifier), allows high transmission capacity over ultra-long distances without optical regeneration and with high flexibility.

Automatic raman gain and tilt control for ultra-long-distance dense WDM optical communication system

A modular interleaved Raman amplifier structure is exploited to reap the advantages provided by the high Raman gain coefficient and small effective area of highly nonlinear fibers without incurring penalties caused by nonlinear effects and double-Rayleigh backscattering noise. Very tight WDM channel spacings may be accommodated. The amplifier structure may be implemented at very low initial cost and with high reliability, scalability, and modularity.

Interleaved lumped raman amplifier structure based on highly nonlinear fibers for densely spaced WDM channels

An advantageous amplification architecture for DWDM systems including systems with very high capacity is provided. A modular interleaved structure for amplification is provided. Advantages include robustness to non-linear effects, modular as-needed deployment of system capacity, and low noise figure in implementations that incorporate Raman amplification technology.

Modular optical amplifier structure for highly dense interleaved WDM systems

An optical amplifying unit includes an input for the input optical signals and an output for the output of the optical signals. A single-mode active fiber codoped with Er and Yb is optically connected to the input and the output and adapted to amplify the optical signals. A first pump source generates a first pump radiation including an excitation wavelength for Er, and a second pump source for generates a second pump radiation including an excitation wavelength for Yb. A first optical coupler optically couples the first pump radiation into the core of the active fiber in a co-propagating direction with respect to signal direction, and a second optical coupler optically couples the second pump radiation into the core of the active fiber in a counter-propagating direction with respect to signal direction.

Optical amplifying unit and optical transmission system

An optical amplifying unit ( ) for amplifying optical signals in an optical transmission system has an amplification wavelength band with a lower wavelength limit greater than 1570 nm and includes an input ( ) for the input of optical signals, an output ( ) for the output of optical signals and an optical amplifier ( ) interposed between the input ( ) and the output ( ) to amplify the optical signals. The optical amplifier ( ) includes an amplification fiber ( ) co-doped with erbium and ytterbium, at least a pump source ( ) to generate pump radiation and at least an optical coupler ( ) optically coupling the pump sources ( ) to the amplification fiber ( ). The optical amplifying unit has a power gain of at least 31 dB when the optical signals have an input power of at least &minus;10.5 dBm and wavelengths within the amplification wavelength band.

An optical transmission system includes an optical transmitting unit ( ) to transmit optical signals in a transmission wavelength band above 1570 nm; an optical receiving unit to receive the optical signals; an optical fiber link optically coupling the transmitting unit to the receiving unit, at least an optical amplifying unit ( ) coupled along the link and adapted to amplify the optical signals; the optical amplifying unit ( ) having an amplification wavelength band including the transmission wavelength band and comprising: an input ( ) for the input of the optical signals, an output ( ) for the output of the optical signals, at least an erbium-doped active fiber ( ) for the amplification of the optical signals, having a first end optically coupled to the input ( ) and a second end optically coupled to the output ( ), a pump source ( ) for generating a pump radiation having a wavelength greater than 1400 nm and lower than 1470 nm, and an optical coupler ( ) optically coupling the pump source ( ) to the active fiber ( ).

Optical amplifier and optical transmission system

An approach for minimizing four-wave mixing (FWM) cross-talk (XT) in a WDM (wavelength division multiplexing) optical communication system is disclosed. An Erbium doped Fiber Amplifier (EDFA) includes a pre-amplifier that receives an input optical signal and outputs an amplified input optical signal. The pre-amplifier includes the following components: a first active fiber that carries WDM signals corresponding to a particular operating band (e.g., L-band); a co-propagating pump laser that induces high inversion in a portion of the first active fiber; a filter that is coupled to the first active fiber and slightly inverts the gain tilt of the WDM signals and suppresses the amplified spontaneous emission (ASE) lights accumulated at wavelengths shorter than the signal bandwidth; a second active fiber that is coupled to the filter; and a counter-propagating pump laser that induces high inversion in a portion of the second active fiber. An optical unit (e.g., an optical add/drop module, a gain equalizing filter (GEF), or a dispersion compensating fiber (DCF)) may be coupled to the pre-amplifier and receives the amplified input signal, in which the optical unit introduces a prescribed loss to the WDM system. A booster amplifier is coupled to the optical unit and is configured to amplify a signal that is output from the optical unit. An automatic optical gain control (AOGC) mechanism of the EDFA provides nearly constant gain that is independent of the number of channels utilized in the WDM system and also minimizes system penalties due to fast relaxation oscillations induced by adding/dropping of channels.

All-optical gain controlled L-band EDFA structure with reduced four-wave mixing cross-talk

A pump device to couple a pump radiation to an active optical fiber adapted to amplify optical signals, includes a first optical coupler ( ) that optically couples a first fraction of the pump radiation ( ) to the active fiber ( ) and has an insertion loss for the optical signals less than or equal to 0,2 dB; and a second optical coupler ( ) that is optically coupled to the first coupler ( ) to receive from the first coupler ( ) a second fraction of the pump radiation, that is further optically coupled to the active fiber ( ) for feeding to the active fiber ( ) at least part of the second fraction of the pump radiation and that has a coupling efficiency for the pump radiation of at least 70%.

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Milan, Italy

Giovanni Sacchi