Abstract: In an optical amplifier for use in, for example, a wavelength multiplexing optical communication system, in order to allow an excitation light source to be enlargeable or removable in accordance with an increase/decrease in the number of channels in signal light even if the optical communication system is in operation, there are included an optical amplifying section (2) for amplifying and outputting inputted signal light, a plurality of excitation light sources (3, 4) and an excitation light source control section (5) for controlling operations of the excitation light sources (3, 4), wherein the excitation light sources are composed of a main excitation light source (3) and an auxiliary excitation light source (4), and the excitation light source control section (5) is equipped with a control section (7) which, when the number of channels in the inputted signal light is equal to or less than a predetermined number of channels, executes control whereby the main excitation light source (3) supplies excitation

Abstract: A bidirectionally pumped optical amplifier (200) comprises an active fibre (201), a first WDM coupler (204) and a second WDM coupler (205), a first pump: branch (220) coupled to said first WDM coupler (204) comprising a first laser (202) and a first grating (210), for introducing pump radiation into said active fibre (201) in a first direction, a second pump branch (230) coupled to said second WDM coupler (205) comprising a second laser (203) and a second grating (212), for introducing pump radiation into said active fibre (201) in a second direction, opposite to said first direction. The second laser has an output power PF. A first pump residual, having a power Pinj, is coupled into said second pump branch (230) from the active fibre (201) and injected into said second laser (203). The first pump branch (220) further comprises an optical isolator (211) for the pump radiation. The output power of the injected laser and the injected pump power residual are such that PF/Pinj>2.

Abstract: An optical amplifier. The amplifier includes a plurality of pump radiation sources, each pump radiation source adapted to produce radiation having a set of pump wavelengths and pump powers corresponding to the respective pump wavelengths, wherein at least one set is different from at least one other set. The amplifier also includes a plurality of pump radiation combiners and a coupler. The coupler is optically coupled to the outputs of the pump radiation combiners, receives the coupled radiation from the pump radiation combiners and outputs pump radiation profiles to respective coupler outputs. The amplifier also includes pump-signal combiners, each optically coupled to a respective coupler output of the coupler outputs, which are adapted to couple an optical signal with the respective pump radiation profiles.

Abstract: The present invention relates to an optical fiber transmission system in which at least a first carrier signal, having a wavelength in a first spectral band, is transmitted, said system including an optical fiber, at least a first Raman amplifier module for launching into said optical fiber a first pumping signal at an appropriate wavelength for a stimulated Raman amplification of said first carrier signal, said first Raman amplifier module including first pumping means comprising two optical sources, a first of said optical sources emitting at said appropriate wavelength a linear beam along a first axis of polarization, a second of said optical sources emitting at said appropriate wavelength a linear beam along a second axis of polarization distinct from said first axis, first combination means arranged to combine said beams in order to provide said first pumping signal.

Abstract: An optical fiber amplifier module is disclosed which comprises a signal path locatee between a signal input and a signal output. A WDM coupler and an amplifying gain medium are disposed along the signal path. A pump laser is disposed out of the signal path in a manner that allows a pump signal from the pump laser to reflect off the WDM coupler and enter the signal path. An embodiment utilizing a second WDM coupler and a second pump laser is also disclosed.

Abstract: The amplification and noise level of an optical communication signal is controlled by providing a feedback loop to adjust the energy level of an optical pump energy source used to amplify the communication signal. The communication signal is combined with an optical control signal outputted by the pump energy source. The communication signal is amplified as the combined signals pass through an erbium doped fiber optic cable energized by the control signal. The amplified communication signal is then separated from the control signal. The control signal is in a depleted state (substantially residual pump energy) after traveling through the length of the erbium doped fiber optic cable. A feedback signal, used to adjust the energy level of the control signal, is generated based on the amplified communication signal and the depleted control signal.

Abstract: Inputted multiplexed optical signal is separated by an optical branching section into C-band multiplexed optical signal and L-band multiplexed optical signal, and the C-band multiplexed optical signal and L-band multiplexed optical signal are optically amplified by a C-band optical amplifier and an L-band optical amplifier, respectively. The amplified optical signals are combined by an optical combiner, and thus combined optical signal is outputted therefrom. The backward ASE light generated in the L-band optical amplifier upon optical amplification is blocked by an optical filter disposed between the optical amplifier and the optical branching section, so as to be prevented from traveling backward and being inputted to and amplified by the C-band optical amplifier, whereby the deterioration of noise characteristics is restrained.

Abstract: In an optical amplifier for use in, for example, a wavelength multiplexing optical communication system, in order to allow an excitation light source to be enlargeable or removable in accordance with an increase/decrease in the number of channels in signal light even if the optical communication system is in operation, there are included an optical amplifying section (2) for amplifying and outputting inputted signal light, a plurality of excitation light sources (3, 4) and an excitation light source control section (5) for controlling operations of the excitation light sources (3, 4), wherein the excitation light sources are composed of a main excitation light source (3) and an auxiliary excitation light source (4), and the excitation light source control section (5) is equipped with a control section (7) which, when the number of channels in the inputted signal light is equal to or less than a predetermined number of channels, executes control whereby the main excitation light source (3) supplies excitation

Abstract: An optical transmission system includes an optical transmitting unit (10) 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 (100) coupled along the link and adapted to amplify the optical signals; the optical amplifying unit (100) having an amplification wavelength band including the transmission wavelength band and comprising: an input (101) for the input of the optical signals, an output (102) for the output of the optical signals, at least an erbium-doped active fiber (103a, 103b) for the amplification of the optical signals, having a first end optically coupled to the input (101) and a second end optically coupled to the output (102), a pump source (104, 106) for generating a pump radiation having a wavelength greater than 1400 nm and lower than 1470 nm, and an optical coupler (105, 107) optically coup

Abstract: A system and method for amplifying an optical signal within an optical waveguide amplifier including providing at least one optical waveguide amplifier having an input for receiving an optical source signal therein and an output, wherein a forward pumping direction extends from the input to the output and rearward pumping direction extends from the output to the input. The system also includes providing at least one excitation light source in optical communication with the optical waveguide amplifier and capable of generating at least one excitation light. The system further includes amplifying the source signal by pumping a first excitation light from the excitation light source in the rearward pumping direction, and amplifying the source signal by simultaneously pumping a second excitation light from the excitation light source in the forward direction.

Abstract: An optical amplifier is described that can couple to and amplify optical signals along multiple fiber transmission paths. The optical amplifier includes a plurality of pump radiation sources, each pump radiation source adapted to produce radiation having a set of pump wavelengths and pump powers corresponding to the respective pump wavelengths, wherein at least one set is different from at least one other set. The optical amplifier also includes a plurality of pump radiation combiners, each pump radiation combiner coupling the radiation of a respective set of pump wavelengths of a respective source of the plurality of pump radiation sources and outputting the respective coupled radiation having coupled radiation profiles via a respective pump radiation combiner output. The optical amplifier also includes a coupler, such as a P×V coupler with P inputs and V outputs.

Abstract: An optical amplification system is described. The system includes a series of optical amplifier groups optically connected in series. Each optical amplifier group comprising multiple optical amplifiers. The optical amplifiers of a particular amplifier group each produces pump radiation having a different set of pump wavelengths and pump powers corresponding to the respective pump wavelengths. Each amplifier group provides a desired gain profile, such as a substantially flat gain profile, over a first range of optical signal wavelengths.

Abstract: A method for enabling a pump laser to be added on by means of an optical fiber Raman amplifier and reducing signal degradation to be caused by a gain change to occur after and in the pump laser source add-on process.

Abstract: Optical amplifiers are provided in which optical gain is produced by Raman pumping fiber. The Raman-pumped fiber may be a span of transmission fiber or a coil of fiber in a discrete amplifier. Raman pump light may be provided using laser diodes operating at different wavelengths. The Raman pump light that is produced by the laser diodes may be modulated to reduce pump interactions in the fiber. Raman pump light may be modulated by directly modulating the laser diodes or by using optical components that modulate constant power pump light from the laser diodes.

Abstract: An optical amplifier including a pumping source for supplying pump light to an optical fiber transmission line is provided so that at least a part of the optical fiber transmission line produces Raman amplification to an optical signal. An optical filter unit for selectively switching between a first condition where the optical signal and the pump light are passed and a second condition where the optical signal is passed and the pump light is not passed is connected between the optical fiber transmission line and the optical amplifier. The power of the optical signal in the first condition is compared with that in the second condition, and the characteristics of the optical fiber transmission line, such as a splice loss therein, is evaluated according to the result of this comparison.

Abstract: The optical fiber pumping system includes a connector that is adapted to selectively communicate with an external pump system. The connector communicates with an onboard pump multiplexer which also receives input from an on-board pump via a connector. The on-board pump may be hot swapped by connecting an external pump system to the connector and coordinating the power up of the external pump system with the power down of the on-board pump to replace a failed on-board pump with a new pump.

Abstract: An optical amplifier comprises an optical fiber segment doped with impurity ions such as erbium for providing optical gain for an optical signal propagating in the optical fiber segment. A first source of a first pumping wavelength pumps the ions from a first ground state to a second metastable state. The metastable state decays to the ground state by stimulated emission to provide the optical gain. A second source of a second pumping wavelength pumps the ions from the ground state to a third auxiliary state. The auxiliary state decays to the metastable state. Thus, by controlling the pumping power in one or both pumping wavelengths, it is possible to control the fraction of ions in the metastable state. This in turn permits control of an overall scale factor of the gain spectrum without substantially affecting the shape of the gain spectrum.

Abstract: Multiwavelength Raman pumps for Raman amplifiers are provided. The multiwavelength Raman pumps may be based on semiconductor devices that have multiple source regions, each of which handles pump light at a different wavelength. An optical coupler such as a lens and isolator arrangement or an integral fiber lens may be used to couple pump light from the multiwavelength Raman pump into a fiber. A depolarizer may be used to depolarize the Raman pump light provided by the Raman pump. Gratings may be used to define the lasing wavelengths for the Raman pump. A number of tunable sources may be used on the semiconductor device. A fiber Bragg grating may be used to form an external cavity or coupled cavity arrangement for the semiconductor device.

Abstract: A plurality of Raman amplifiers are positioned on a transmission line over which a multi-wavelength light is transmitted. Each of the Raman amplifiers uses a plurality of pump lights &lgr;1 through &lgr;4. When a fault occurs in a pump light source producing the pump light &lgr;3 in a particular Raman amplifier among the plurality of Raman amplifiers, the power of the pump light &lgr;3 is raised in another or other Raman amplifiers.

Abstract: A plurality of pump lights are appropriately located in a wavelength band &lgr;1 to &lgr;3. The width of the wavelength band &lgr;1 to &lgr;3 is wider than a Raman shift amount. Gain is obtained in a wavelength band &lgr;2 to &lgr;3 by the plurality of pump lights located in the wavelength band &lgr;1 to &lgr;2. Gain is obtained in a wavelength band &lgr;3 to &lgr;4 by the plurality of pump lights located in the wavelength band &lgr;2 to &lgr;3. As a result, gain can be obtained in a wavelength band &lgr;2 to &lgr;4. A plurality of signal lights are located in the wavelength band &lgr;2 to &lgr;4. The deviation of gain can be adjusted by controlling the power of each of the plurality of pump lights.

Abstract: A laser amplifier and/or oscillator comprise a gain medium including rare earth dopant in an host medium. Ions of the rate earth dopant has an energy level structure including a ground level and a pair of laser upper level and laser lower levels between which a stimulated transition is to be produced after production of a population inversion between the pair of laser upper and laser lower levels. A first exciting light source is coupled to the gain medium for introducing first exciting light to said gain medium to produce said population inversion. A second exciting light source is coupled to the gain medium for introducing second exciting light to the gain medium to raise the rare earth dopant ions from the ground level to the laser lower level.

Abstract: A pump source for rare earth and Raman amplifiers or for distributed amplification uses two or more light sources to generate two source beams that are combined by a beam combiner to form the output pump beam. In accordance with one embodiment, the light sources are a diode laser array having be two or more monolithic laser stripes providing dual output beams having substantially the same polarization, such as the TE mode. One of the polarized due outputs is rotated 90° and both beams are applied to a birefringent crystal that combines the beams for insertion into an optical fiber or into a rare earth doped fiber or into a fiber capable of Raman amplification via SRS. The power output of each polarization in the combined beam can be measured and used to drive a feedback circuit that controls the current provided to each diode in order to maintain the power in the two polarization components of the output beam equal.

Abstract: An optical amplifying module having an internal pumping source is provided. WDM signal light obtained by wavelength division multiplexing a plurality of optical signals allocated to different wavelength channels is supplied to the optical amplifying module. An output power from the internal pumping source is adjusted so that the optical amplifying module provides a gain for the WDM signal light. A booster module having an external pumping source for supporting the gain is connected to the optical amplifying module. An output power from the external pumping source is set according to the number of channels of the WDM signal light. This method allows easy response to a change in the number of channels of the WDM signal light.

Abstract: Optical systems of the present invention include amplifiers configured to achieve maximum signal channel in a span downstream of the transmitter and amplifier site and to decrease the interaction between the wavelengths at high signal channel powers. In addition, the system can include various types of optical fiber positioned in the network to provide for increased signal channel powers and higher gain efficiencies in the system.

Abstract: A Raman amplifier according to the present invention comprises a plurality of pumping means using semiconductor lasers of Fabry-Perot, DFB, or DBR type or MOPAs, and pumping lights outputted from the pumping means have different central wavelengths, and interval between the adjacent central wavelength is greater than 6 nm and smaller than 35 nm. An optical repeater according to the present invention comprises the above-mentioned Raman amplifier and adapted to compensate loss in an optical fiber transmission line by the Raman amplifier. In a Raman amplification method according to the present invention, the shorter the central wavelength of the pumping light the higher light power of said pumping light.

Abstract: An optical fiber amplifier capable of having a flattened gain irrespective of the intensity of an input signal light. The optical fiber amplifier includes a first amplifying unit for amplifying an input signal light using a first pumping light to obtain a predetermined gain, a second amplifying unit for re-amplifying the signal light amplified by the first amplifying unit, using a second pumping light, to obtain the same gain as the predetermined gain, and a pumping light separating unit for allowing the amplified signal light outputted from the first amplifying unit to enter the second amplifying unit while preventing the first pumping light from reaching the second amplifying unit and preventing the second pumping light from reaching the first amplifying unit, whereby the amplified signal light entering the second amplifying unit is allowed to be amplified only by the second pumping light.

Abstract: An improved long wavelength-band EDFA (L-band EDFA) is disclosed. The EDFA includes an input terminal for receiving signal light, a pumping unit for pumping a 1,530 nm wavelength band pumping light, a WDM coupler for multiplexing the signal light and the pumping light, and an EDF pumped by a 1,530 nm wavelength band pumping light for amplifying the signal light. Compared with conventional 1,480 nm pumping, the EDFA pumped by 1,530 nm band pumping have about two times higher power conversion efficiency.

Abstract: An object of the invention is to provide, for an optical amplifier which performs amplification of optical signals of two wavelength bands, an optical amplifier and an optical amplification method of a simple configuration which can deal with restrictions on installation space, power consumption and the like. Hence with the optical amplifier of the invention, optical circulators are respectively connected to opposite ends of an optical amplifying means, and optical signals of the respective wavelength bands of a first wavelength band and a second wavelength band are input and output to the optical amplifying means via each of the optical circulators so that the propagation directions of the respective optical signals of the respective wavelength bands are in mutually opposite directions inside a rare earth element doped fiber. As a result, the optical signals of the respective wavelength bands can be collectively amplified with a simple configuration using a single rare earth element doped fiber.

Abstract: A plurality of pumping light sources (1) which generate pumping light having wavelengths different from each other are connected to respective input ports of an optical multiplexer via optical reflectors (3). The respective pumping light is stabilized by optical reflectors with respect to the oscillating wavelengths, and is multiplexed by an optical multiplexer (4). The multiplexed pumping light is multiplexed to signal light passing through an optical fiber (6) for amplification.

Abstract: The output level of pumping light supplied from a pumping light source is varied using a variable attenuator, which is controlled by a variable attenuator driver circuit. By separating a portion containing the pumping light source from a portion containing an amplification medium, it becomes possible to prevent heat emitted by the pumping light source from adversely affecting the amplification medium. By arranging the portion containing the pumping light source such that a pumping light source or sources can be added when necessary, optical transmission system requirements of having more pumping light sources for system upgrade can be accommodated readily. By packaging portions containing amplification media, an optical amplifier can be made small.

Abstract: A gain-controllable optical fiber amplifier having an input for receiving an optical signal and an output for providing an amplified optical signal. A first gain stage is coupled between the input and output and includes a first optical fiber and a first pump. A second gain stage is coupled in series with the first stage and includes a second optical fiber and a second pump. The amplifier includes a pump controller for controlling the first and second pumps and adjusting the power output of the first and second pumps to maintain a substantially constant gain. The controller decreases the power output from each of the first and second pumps as a function of minimum output of each pump to minimize noise. Accordingly, the present invention advantageously controls the gain applied to an optical fiber in a manner that minimizes the amount of noise that may otherwise be introduced into the optical signal, especially when the input power is comparable to the backward amplified spontaneous emission of the amplifier.

Abstract: A twin coupler system couples a multimode pump power signal from a pump fiber to an optical information carrying double-clad signal fiber. The twin coupler system includes first and second optical couplers and a mode scrambler. The first optical coupler couples the pump fiber to the optical signal fiber to transfer outer modes of the pump power signal from the pump fiber into the optical signal fiber. The mode scrambler scrambles the modes of the pump power signal remaining in the pump fiber beyond the first optical coupler. The second optical coupler couples the pump fiber to the optical signal fiber to transfer outer modes of the scrambled pump power signal from the pump fiber into the optical signal fiber.

Abstract: The power of the pumping light to be transmitted is limited by the Raman effect. In order to alleviate the problems associated with this, pumping signals having different wavelengths are transmitted via a number of optical fibers, are combined in a coupling device at the fiber amplifier, and are fed into an amplifier fiber.

Abstract: The output level of pumping light supplied from a pumping light source is varied using a variable attenuator, which is controlled by a variable attenuator driver circuit. By separating a portion containing the pumping light source from a portion containing an amplification medium, it becomes possible to prevent heat emitted by the pumping light source from adversely affecting the amplification medium. By arranging the portion containing the pumping light source such that a pumping light source or sources can be added when necessary, optical transmission system requirements of having more pumping light sources for system upgrade can be accommodated readily. By packaging portions containing amplification media, an optical amplifier can be made small.