Abstract: An optical amplifier which amplifies a wavelength division multiplexed (WDM) optical signal having a variable number of channels associated with different wavelengths and outputs the amplified WDM optical signal. The optical amplifier includes (a) an optical attenuator which controls a level of the amplified WDM optical signal, and (b) a controller which controls the WDM optical signal to be amplified with an approximately constant gain.

Abstract: A multichannel optical amplifier having an adjustable gain set point is controlled to permit substantially constant gain tilt control during a gain set-point change so that the channel powers are maintained during system modification. To this end the amplifier comprises an erbium doped fibre (EDF) loop and associated pump amplifier for amplifying an optical signal comprising channels of different wavelengths, a variable optical attenuator (VOA) for controlling the gain of the amplifier by applying a loss profile that varies with wavelength so that the different channels are amplified in accordance with a required gain tilt, preferably a zero gain tilt, and a PI controller for applying a gain tilt adaptation profile to compensate for an inherent gain tilt to produce the required gain tilt.

Abstract: A multi-wavelength light amplifier includes a first-stage light amplifier which has a first light amplifying optical fiber amplifying a light input, a second-stage light amplifier which has a second light amplifying optical fiber amplifying a first light output from the first-stage light amplifier, and an optical system which maintains a second light output of the second-stage light amplifier at a constant power level. The first-stage and second-stage light amplifiers have different gain vs wavelength characteristics so that the multi-wavelength light amplifier has no wavelength-dependence of a gain thereof.

Abstract: An optical amplifier includes a first optical path, second optical path, semiconductor optical amplifier, and multi-mode interference 3-dB coupler. The first optical path guides oscillation light. The second optical path guides signal light. The semiconductor optical amplifier causes oscillation on the first optical path. The multi-mode interference 3-dB coupler crosses the first and optical paths in the gain medium of the semiconductor optical amplifier.

Abstract: An optical fiber amplifier array and related method, in which high beam quality is achieved by varying the frequency of an input signal applied to all of the fiber amplifiers, to locate a frequency at which the amplifiers produce nearly coherent optical outputs. In spite of statistical variations in length and other factors among the fibers, there are frequencies at which the amplifiers produce nearly coherent outputs. In the control system of the invention, the input signal frequency is scanned across a selected narrow range and the beam quality is monitored by measuring on-axis far-field output beam intensity. The frequency is scanned until the beam intensity exceeds a selected threshold, and then the frequency is held constant until the beam intensity falls below a second selected threshold.

Abstract: An optical communications system initiates automatic power reduction by selecting a portion of a Raman optical pumping signal from optical signals propagating on an optical fiber span. A signal related to a magnitude of the selected portion of the Raman optical pumping signal is generated. Power of at least one of the optical data signals and the optical pumping signals propagating in the optical fiber span is reduced in response to the generated signal.

Abstract: Integration of laser sources into optoelectronic integrated circuits requires that the laser do not operate using two cleaved end facets. Unfortunately, replacing of one of the end facets results by either a dry etched mirror or by a corner reflectors results in undesirable performance of the laser source since a gain coefficient for the laser source is lower than that for a dual cleaved end facet laser source. A modified waveguide is thus proposed which serves to reduce the undesirable effects found when a corner reflector is used by providing an improved waveguide region between the cleaved end facet and the corner reflector that facilitates excitation of a single optical mode within a laser cavity formed between the corner reflector and the cleaved end facet.

Abstract: Optical transmission systems of the present invention include a plurality of optical amplifiers configured to provide optical amplification of one or more information carrying optical signal wavelengths. At least two of the optical amplifier are operated to provide net losses or net gains along corresponding spans, while the cumulative gain provided by the plurality of optical amplifiers substantially compensates for the cumulative loss of the spans.

Abstract: A multi-section filter is provided for use in processing optical signals and other signals that can be readily projected from one filter section to another. Filters of the invention can be configured in numerous forms, including IIR and FIR filters and both linear and 2D active optical lattice filters. Filter sections are coupled together by means of four direction couplers and surface grating couplers, and may be implemented as GSE photonic integrated circuit devices.

Abstract: An amplification medium simulation apparatus comprises a basic data retaining unit 21, an input signal beam information retaining unit 22, and a simulation executing unit 31 approximating and calculating an output signal beam power at each signal beam wavelength outputted from the amplification medium involving a fluctuation in ion population at the metastable energy level in the amplification medium due to input of the input signal beam, by using contents retained in the basic data retaining unit 21 and the input signal beam information retaining unit 22, and outputting a result of calculation as a result of simulation of performance of the amplification medium.

Abstract: An optical apparatus which is reduced in the number of optical devices arranged on a main optical signal transmission path, thereby reducing the size and cost of the device, and which is improved in optical transmission quality. An optical amplifier includes an amplification medium, which is doped with an active material for optical amplification and to which pump light is introduced, for amplifying an optical signal to be output. A reflection-type variable optical attenuator includes a reflecting mirror for reflecting an input light to generate a reflected light, and a magneto-optical crystal arranged in a position where the input and reflected lights pass. The magneto-optical crystal is applied with a magnetic field to induce a Faraday rotation angle therein and thereby vary an attenuation amount of the amplified optical signal, and part of light transmitted through the reflecting mirror is converted, as input monitor light, into an electrical signal.

Abstract: A flattened gain amplifier has a waveguide with a core doped with at least one species of rare earth ion. The rare earth ion has a gain profile with a first gain in a first wavelength band and a second gain in a second wavelength band. The flattened gain amplifier also has a first grating and a reflective element optically coupled to the core. The positions of the first grating and reflective element along the length define a first amplifying length and a second amplifying length. The ratio of the first amplifying length to the second amplifying length is about equal to the ratio of the second gain to the first gain.

Abstract: Disclosed is a gain-providing optical power equalizer which can equalize optical channel output or gain while amplifying signal output. In prior art technologies, optical power equalization has been achieved by attenuating signal output differently depending upon optical channels. However, the optical power equalizer of the present invention is characterized in that it achieves equalization of optical power by giving optical gain differently depending upon optical channels. According to the present invention, the output of optical channels can be adjusted to be flat or as desired without deteriorating signal to noise ratio.

Abstract: Apparatus and method for spectral-beam combining light from a plurality of high-power fiber lasers that, in some embodiments, use two substantially identical diffraction gratings in a parallel, mutually compensating configuration to combine a plurality of separate parallel input beams each having a slightly different successively higher wavelength into a single output beam of high quality. In other embodiments, a single diffraction grating is used to combine a plurality of different wavelengths, wherein the input laser beams are obtained from very narrow linewidth sources to reduce chromatic dispersion. In some embodiments, diagnostics and adjustments of wavelengths and/or positions and angles are made dynamically in real time to maintain the combination of the plurality input beams into a single high-quality output beam.

Abstract: The invention describes a system of two-stage optical amplifiers adapted for inserting OADM in the mid-stage, and an integrated assembly designed for implementing the amplifiers in a way suitable for forming bi-directional configurations useful in optical networks. A so-called east-west configuration for a bi-directional transmission is described, where each direction of the optical transmission is served by the two-stage optical amplifier the 1st stage of which belongs to one integrated assembly, and the 2nd stage—to another assembly.

Abstract: An optical amplifier and a laser generator based on the fiber side-polished technology having a high pumping efficiency, a low noise figure and a small footprint are provided in this application. The optical amplifier and the laser, which have a very long effective interaction length in conjunction with highly doped Erbium glass attached to its surface and an addition of a slanted fiber grating inscribed in the guiding core at the polished region can spatially separate the signal and pump power to simultaneously improve the pumping efficiency and optimize the penetrated depth of the signal evanescent-field. The spontaneous emission is kept from being amplified and therefore a high quality amplified signal is produced.

Abstract: A broad-band light source has a reduced tendency to oscillate and has high efficiency. The broad-band light source comprises (a) an optical waveguide that comprises a optical active element to generate an ASE lightwave when a pumping lightwave is supplied, that outputs an ASE lightwave in a first wavelength band from its first end, and that outputs an ASE lightwave in a second wavelength band from its second end, (b) a pumping lightwave-supplying means for supplying a pumping lightwave to the optical active element, and (c) a lightwave-combining means that receives the ASE lightwave in the first wavelength band, that receives the ASE lightwave in the second wavelength band, that combines the received ASE lightwaves, and that outputs the resultant ASE lightwave.

Abstract: The optical amplifier has a waveguide including a core and a cladding. The cladding at least partially surrounds the core and is doped with at least one species of rare earth ion in the range of 5 to 75 wt %. In another embodiment, the core is doped with Er3+ in the range of 7 to 9 wt % and with Yb3+ in the range of 11 to 13 wt %.

Abstract: Two embodiments of a multilayered low energy optical power limiter device are disclosed which protect thermal sensors against laser threats in the far infrared spectral region. One limiter device has multiple layers in order from the incoming radiation side an antireflective coating layer, a window substrate layer, a layer of chalcogenide, a germanium substrate layer, a layer of vanadium dioxide (VO2), a window substrate, and an antireflective coating layer. As incoming radiation energy increases, the VO2 layer will heat up and change from an unswitched transmissive state to a switched reflective state. The excessive energy past the switched state is reflected back through the germanium and chalcogenide layer and is absorbed quickly therein so that these layers also heat up quickly and are switched almost simultaneously with the VO2 layer to provide high optical density at a low switching threshold temperature with high damage threshold.

Abstract: A transmission wavelength band in an optical transmission line is divided into a plurality of sub-bands and signal lights or an ASE dummy light is disposed per sub-band as a unit. The optical power of the ASE dummy light in each sub-band is controlled so as to realize the gain profile at a full implementation in the optical transmission line. While new signal lights are being added, the optical power of whole ASE dummy lights or the optical power of the ASE dummy lights in sub-bands adjacent to the sub-band in which the new signal lights are to be added is controlled while increasing the optical power of the new signal lights so that the transmission characteristics of the existing signal lights are not affected by the signal addition.