Cisco Technology, Inc.

Corning O.t.i. Spa

Telefonaktiebolaget Lm Ericsson (Publ)

Marconi Communications Gmbh

Corning O.t.i. Inc.

Infibra Technologies S.r.l.

Ericsson Ab

Fabrizio Di Pasquale

Giovanni Sacchi

Fausto Meli

Fabrizio Forghieri

Giorgio Grasso

Silvia Turolla

Francesco Testa

Antonella Bogoni

Antonio D'Errico

Antonio D'errico

Giacomo Antonio Rossi

Guido Oliveti

Paolo Vavassori

Valeria Gusmeroli

Roberta Castagnetti

Federico Carniel

Tiziano Nannipieri

Ada Livia Braverman

Emilio Casaccia

Alessandro Signorini

Paolo Pintus

Paolo Gurnari

Mohammad Taki

Alberto Zermani

Stefano Faralli

Antonio D'ERRICO

A method for measuring a distributed physical value of an optical device under test (DUT), includes the steps of: launching into the DUT a probe signal that includes a plurality of optical pulses at at least one test wavelength, and receiving at least one optical signal backscattered by the DUT, wherein the optical pulses are obtained with at least the following steps: generating a first time sequence of first pulses that corresponds to a word of a first code, the first time sequence lasting not shorter than a time of flight and being formed by a number of time slots that is equal to the number of bits of the word of the first code; generating a second time sequence of second pulses that corresponds to a word of a second code; and amplitude modulating the second time sequence with the first time sequence.

Method and apparatus for measuring a distributed physical value of an optical device under test

Optical add and drop switch and aggregator apparatus comprising: N first wavelength selective routing apparatus each configured to split a wavelength multiplexed input signal into L sub-signals; demultiplexers each configured to demultiplex a respective sub-signal into K optical signals; output ports each configured to output a respective output optical signal; add ports configured to receive optical signals to be added; M second wavelength selective routing apparatus each having X outputs, each said apparatus being configured to receive optical signals from a respective add port and to route each received optical signal to a respective one of its outputs; drop ports configured to output optical signals to be dropped; and a switch matrix coupled between the demultiplexers, the output ports, the drop ports and the second wavelength selective routing apparatus, the switch matrix comprising a plurality of optical switches arranged in XM columns and KLN rows.

Optical routing apparatus and method

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 adaptive dispersion compensation system that also achieves optical amplification by inducing Raman amplification effects in dispersion compensating fiber. This amplification/chromatic dispersion compensation architecture may be applied, e.g., at the end of an all-optical link, or an intermediate points along the link. By varying the length of dispersion compensating fiber used and the pump power, one may accommodate a wide range of dispersion compensation requirements as determined in the field. This scheme also provides all of the advantages typically provided by the use of Raman amplification.

Lumped raman amplifier for adaptive dispersion compensation

Lumped Raman amplifier for adaptive dispersion compensation

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

Raman amplification of a WDM signal with excellent gain flatness across a very large bandwidth is achieved. Co-propagating and counter-propagating Raman pumping are combined in the same fiber. Multiple pumping wavelengths are employed. Wavelengths employed for co-propagating pumping and wavelengths employed for counter-propagating pumping alternate in order of wavelength. In one embodiment, N co-propagating pump wavelengths and N+1 counter-propagating pump wavelengths are used. Alternatively, one may use N+1 co-propagating pump wavelengths and N counter-propagating pump wavelengths.

Gain flattened bi-directionally pumped Raman amplifier for WDM transmission systems

Systems and methods for ameliorating double Rayleigh backscattering induced impairments are provided. Raman amplification is divided among two or more stages. Optical energy from a single counter-propagating pump may traverse multiple stages while optical energy at the frequency of the signal to be amplified is permitted to propagate in the forward direction only. In this way the pump power can be effectively distributed over the entire amplifier length. The scheme may be implemented in a simple configuration employing a closed circulator and a fiber Bragg grating. Multiple wavelength pump operation may be accommodated as well as either discrete or distributed Raman amplification.

Suppression of double rayleigh backscattering and pump reuse in a raman amplifier

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

Four-wave mixing crosstalk between co-propagating Raman amplification pump sources and WDM channels is suppressed. Therefore, co-propagating pumping may be applied to Raman amplification without incurring penalties due to four-wave mixing crosstalk. Pump power need not be substantially increased to accommodate use of the present invention. Also, the use of lower cost Fabry-Perot pump sources is facilitated. In one implementation, the advantageous suppression of four-wave mixing crosstalk between pump signals and WDM channels is accomplished by imposing chromatic dispersion on the co-propagating pump sources.

Copropagating Raman pump unit to suppress four-wave mixing crosstalk between pump modes and WDM signals

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 ( ).

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Milan, Italy

Fabrizio Di Pasquale