Abstract: A method and system for bandwidth efficient optical transport in radio access networks using radio-over-fiber optical transport may directly transmit radio access signals over an optical fiber by frequency multiplexing multiple parallel streams of digital wireless signals into a serial stream of optical digital subcarrier signals. A radio-over-fiber transceiver to enable efficient optical transport in radio access networks may be implemented on remote radio head and baseband unit equipment as a plug-in digital coherent optics module or as an on-board internally mounted digital coherent optics module.

Abstract: A Raman amplifier comprising a gain control unit adapted to control a pump power of an optical pump signal in response to at least one monitored optical feedback signal reflected back from a transmission line fiber connected to said pumped Raman amplifier.

Abstract: Methods and systems for post-transient gain control of optical amplifiers may include using a gain offset control module in an optical amplifier to generate a gain offset cancelling signal. The gain offset cancelling signal may be output to a gain control module in the optical amplifier to generate at least one of a pump signal and an attenuation control signal. In this manner, a gain offset may be cancelled for a plurality of wavelengths in an optical signal transmitted by an optical network.

Abstract: Methods and systems for post-transient gain control of optical amplifiers may include using a gain offset control module in an optical amplifier to generate a gain offset cancelling signal. The gain offset cancelling signal may be output to a gain control module in the optical amplifier to generate at least one of a pump signal and an attenuation control signal. In this manner, a gain offset may be cancelled for a plurality of wavelengths in an optical signal transmitted by an optical network.

Abstract: A method and apparatus for suppressing pump-mode optical beat interference noise in a Raman amplified fiber link of an optical network, wherein a wavelength of a laser beam generated by a first pump laser and a wavelength of a laser beam generated by a second pump laser of a pair of polarization multiplexed pump lasers are detuned with respect to each other to suppress the optical beat interference, OBI, noise in the Raman amplified fiber link of said optical network.

Abstract: The invention relates to a directionless and colorless reconfigurable optical add/drop multiplexer (ROADM) for a number of clients comprising: an add/drop interface for optical signals of at least one optical network, wherein each received optical signal is split by at least one optical splitter into optical signals which are applied to a downstream cross connector distributing the split optical signals to wavelength selectors of different clients, wherein each wavelength selector performs a wavelength selection of at least one wavelength from the distributed optical signals, wherein an optical signal having a selected wavelength (?) is applied to a client transponder of a client.

Abstract: A Raman amplifier comprising a gain control unit adapted to control a pump power of an optical pump signal in response to at least one monitored optical feedback signal reflected back from a transmission line fiber connected to said pumped Raman amplifier.

Abstract: It is described an optical amplification device for receiving an optical input signal and transmitting an amplified optical output signal on the basis of the optical input signal comprising an optical amplifier that comprises an input and an output. An optical gain control unit is connected to the output path of the optical amplifier and the optical gain control unit is connected to the input path of the optical amplifier. The optical gain control unit is configured to control the gain of the optical output signal. Additionally, an electrical gain control unit is connected to the output path of the optical amplifier. The electrical gain control unit is also connected to the input path of the optical amplifier. The electrical gain control unit is configured to control the gain of the optical output signal. By providing both an electrical gain control unit and an optical gain control unit, a control characteristic can be improved.

Abstract: A Raman amplifier comprising a gain control unit adapted to control a pump power of an optical pump signal in response to at least one monitored optical feedback signal reflected back from a transmission line fiber connected to said pumped Raman amplifier.

Abstract: A method and apparatus for suppressing pump-mode optical beat interference noise in a Raman amplified fiber link of an optical network, wherein a wavelength of a laser beam generated by a first pump laser and a wavelength of a laser beam generated by a second pump laser of a pair of polarization multiplexed pump lasers are detuned with respect to each other to suppress the optical beat interference, OBI, noise in the Raman amplified fiber link of said optical network.

Abstract: A Raman amplifier comprising a gain control unit adapted to control a pump power of an optical pump signal in response to at least one monitored optical feedback signal reflected back from a transmission line fiber connected to said pumped Raman amplifier.

Abstract: It is described an optical amplification device for receiving an optical input signal and transmitting an amplified optical output signal on the basis of the optical input signal comprising an optical amplifier that comprises an input and an output. An optical gain control unit is connected to the output path of the optical amplifier and the optical gain control unit is connected to the input path of the optical amplifier. The optical gain control unit is configured to control the gain of the optical output signal. Additionally, an electrical gain control unit is connected to the output path of the optical amplifier. The electrical gain control unit is also connected to the input path of the optical amplifier. The electrical gain control unit is configured to control the gain of the optical output signal. By providing both an electrical gain control unit and an optical gain control unit, a control characteristic can be improved.

Abstract: The invention relates to a directionless and colorless reconfigurable optical add/drop multiplexer (ROADM) for a number of clients comprising: an add/drop interface for optical signals of at least one optical network, wherein each received optical signal is split by at least one optical splitter into optical signals which are applied to a downstream cross connector distributing the split optical signals to wavelength selectors of different clients, wherein each wavelength selector performs a wavelength selection of at least one wavelength from the distributed optical signals, wherein an optical signal having a selected wavelength (?) is applied to a client transponder of a client.

Abstract: A method for transmitting broadcast and narrowcast services in a system having a headend, a hub connected the headend, and a plurality of nodes connected to the hub. Instead of transmitting the signals directly from the headend to each node, the signals are transmitted from the headend to the hub. The signals transmitted from the headend to the hub include both broadcast services to be transmitted to each node and narrowcast services to be transmitted only to predetermined targeted nodes. The broadcast and narrowcast services are transmitted by optical signal beams operating at different wavelengths. Subscribers can transmit signals to the headend, via each node, on the reverse channel. The reverse channel information from subscribers is combined at each respective node into a single wavelength for each node. The narrowcast services are added at the headend instead of at the hub.

Abstract: A system and method for reducing Raman cross-talk between optical signals having different wavelengths in an optical communications system. Optical signals having wavelengths &lgr;1, &lgr;2, &lgr;3, and &lgr;4, respectively, are launched into an optical fiber at the headend of the system by an optical transmitter. Each wavelength &lgr; is preferably separated from each adjacent wavelength by the same amount, &Dgr;&lgr;. &lgr;1 and &lgr;2 have vertical polarizations and &lgr;3 and &lgr;4 have horizontal polarizations. Because there is no Raman cross-talk between orthogonally polarized optical signals, there will be no Raman cross-talk between &lgr;1 and &lgr;3, between &lgr;2 and &lgr;4, between &lgr;1 and &lgr;4, or between &lgr;2 and &lgr;3. However, there is Raman cross-talk between &lgr;1 and &lgr;2 because each is vertically polarized and also between &lgr;3 and &lgr;4 because each is horizontally polarized.

Abstract: A system for amplifying separate optical signals traveling in a forward path and a reverse path over an optical communications system used for CATV program distribution. A first and second optical circulator, each having a first, second, and third port, are connected to respective opposite sides of a bi-directional amplifier. The first port of the first circulator inputs a first optical signal traveling in the forward path. The second port of the first circulator is coupled to an input/output port of the amplifier. The third port of the first circulator outputs an amplified second signal traveling in the reverse path. The second circulator is similarly connected to the side of the amplifier. A first and second signal/signal WDM coupler, each having a pass port P, an add port A/D, and a common port C, are coupled to the first and second optical circulators, respectively.

Abstract: A distortion circuit for linearizing third-, fifth- and seventh-order distortion components in a non-linear optical communications system includes at least one group of series connected diodes coupled to a common input terminal for receiving a signal source at one end and to an inductor and a capacitor at the other end, a resistance coupled to the common input terminal and a bias source for providing a bias current to the group of series connected diodes. The distortion circuit may be implemented as a predistortion circuit in the headend of the optical communications system or as a postdistortion circuit at the receiving end.

Abstract: An optical modulator for a high power laser transmitter includes a laser source coupled through a phase modulator to a signal modulator. A noise source provides a band limited noise signal to either the laser source or the phase modulator or both. Alternatively, an optical modulator for a high power laser transmitter includes a laser source providing a laser output optical signal and a phase modulator. First and second continuous wave signals at respective first and second frequencies are combined to modulate either the laser source or the phase modulator. The first frequency is different than the second frequency. The laser and phase modulation produces a broadened optical output signal such that the broadened optical output signal is characterized by beat frequencies harmonically related to the first and second frequencies. The modulation bandwidth includes no significant beat frequencies.

Abstract: An optical modulator for a high power laser transmitter includes a laser source coupled through a phase modulator to a signal modulator. A noise source provides a band limited noise signal to either the laser source or the phase modulator or both. Alternatively, an optical modulator for a high power laser transmitter includes a laser source providing a laser output optical signal and a phase modulator. First and second continuous wave signals at respective first and second frequencies are combined to modulate either the laser source or the phase modulator. The first frequency is different than the second frequency. The laser and phase modulation produces a broadened optical output signal such that the broadened optical output signal is characterized by beat frequencies harmonically related to the first and second frequencies. The modulation bandwidth includes no significant beat frequencies.