Abstract: Multi-wavelength light is inputted to an erbium-doped fiber as an optical amplification medium. Pump light is supplied to this erbium-doped fiber. When a transition from a state signal light on the short wavelength area in the multi-wavelength is input in the erbium-doped fiber to a state the signal light is not input, the output power of signal light on the long wavelength area in the multi-wavelength light can vary. The wavelength of pump light is selected in such a way that the output power of the signal light on the long wavelength area can not be negative when the power varies.

Abstract: There is provided an optical amplifier including a Raman amplification medium, a rare earth doped fiber located at a latter stage of the Raman amplification medium, a first pump light outputting unit for outputting pump light with a plurality of wavelengths, a variable distribution element for distributing the pump light with the plurality of wavelengths, outputted from the first pump light outputting unit, to the Raman amplification medium and the rare earth doped fiber in a variable distribution ratio for each wavelength, and a control unit for individually controlling the distribution ratio of the pump light with the plurality of wavelengths in the variable distribution element and the power of the pump light with the plurality of wavelengths from the first pump light outputting unit in accordance with a wavelength arrangement of each of signal lights wavelength-multiplexed into the wavelength-multiplexed signal light.

Abstract: A Raman amplifier providing a wideband gain for use in a wavelength division multiplexing (WDM) optical communication system. In one embodiment, a first optical amplifier Raman amplifies a wavelength division multiplexed signal light in both a first wavelength band and a second wavelength band in accordance with a plurality of excitation (pumping) lights provided to the first optical amplifier, the first and second wavelength bands being different from each other. A divider divides the amplified signal light into first and second lights in the first and second wavelength bands, respectively. A second optical amplifier amplifies the first light and has a gain band in the first wavelength band. The third optical amplifier amplifies the second light and has a gain in the second wavelength band. In various embodiments, a gain equalizer and/or an optical isolator is used in combination with the first optical amplifier providing the Raman amplification.

Abstract: A Raman amplifier for amplifying a wavelength division multiplexed (WDM) light including signal lights wavelength division multiplexed together. The amplifier includes an optical amplifying medium and a controller. The optical amplifying medium uses Raman amplification to amplify the WDM light in accordance with multiplexed pump lights of different wavelengths traveling through the optical amplifying medium. The WDM light is amplified in a wavelength band divided into a plurality of individual wavelength bands. The controller controls power of each pump light based on a wavelength characteristic of gain generated in the optical amplifying medium in the individual wavelength bands.

Abstract: In an optical amplification characteristics simulation apparatus according to the present invention, using spectrums of a signal light input to an optical amplifier and a characteristic parameter for amplification medium, gain wavelength characteristics of the amplification medium are calculated. A calculating formula for the above has a parameter corresponding to a gain fluctuation portion due to a gain spectral hole burning (GSHB) phenomenon, and this parameter is defined by a function obtained by modeling a physical phenomenon in which a population inversion rate is reduced due to the GSHB, based on that electron occupation numbers in each Stark level on the end level side are increased. Then, based on the calculated gain wavelength characteristics, the output power of the signal light is obtained, to thereby perform the optical amplification characteristics simulation on the optical amplifier.

Abstract: A control apparatus comprises a light monitoring unit for dividing a signal wavelength band into at least a band in which output light power of an optical amplifier tends to decrease at an decrease in the number of signal wavelengths and a band including a gain deviation band, and for monitoring inputted light power for the individual divided bands, a calculation unit for obtaining the number of signal wavelengths in the individual divided bands based on a monitor result, and a target gain correction unit for correcting a target gain based on a result of the calculation. This suppresses a transient variation of signal light level due to SHB or SRS at a high speed with a simple configuration without deteriorating noise characteristic, thus enabling optical amplifiers to be further disposed in a multi-stage fashion, which can lengthen the transmission distance of a transmission system including an optical add/drop unit.

Abstract: The present invention relates to an optical transmission apparatus capable of suppressing a transitional gain variation when a number of signal wavelengths changes, and maintaining communication quality in optical signals. The optical transmission apparatus is provided with an optical power control device that varies light power of light for each wavelength component corresponding to a wavelength channel, the light including signal light and spontaneous emission light; a wavelength arrangement information obtaining unit that obtains arrangement information of the wavelength channel of the signal light; and a control unit that controls the power control device based on the arrangement information obtained at the wavelength arrangement information obtaining unit so that light power of a wavelength component of the signal light and light power of a wavelength component other than the wavelength component of the signal light become substantially equal.

Abstract: An optical fiber includes: a first core portion doped with rare earth ions; a second core portion having a lower refractive index than that of the first core portion, provided along an outer circumference of the first core portion, and doped with the rare earth ions; and a clad portion having a lower refractive index than that of the second core portion and provided along an outer circumference of the second core portion, and is configured such that a concentration of the rare earth ions added to the second core portion is higher than that to the first core portion. With this configuration, it is possible to suppress an amount of FWM crosstalk in an optical amplification by decreasing the length of a fiber while alleviating efficiency deterioration due to concentration quenching.

Abstract: According to an optical surge suppressive type optical amplifier in the present invention, for a WDM optical amplifier having a multi-stages amplification configuration in which a plurality of optical amplifying means is connected in series, an optical amplifying medium capable of causing a homogeneous up-conversion (HUC) phenomenon is applied to the optical amplifying means on the signal light output side, so that an optical surge is suppressed utilizing the degradation of gain efficiency by the HUC caused at the time when the input power is decreased. Further, for a one wave optical amplifier, an optical amplifying medium capable of causing a pair induced quenching (PIQ) phenomenon is applied to the optical amplifying means on the signal light input side, so that the optical surge is suppressed utilizing the degradation of output power efficiency by the PIQ caused at the time when the input power is increased.

Abstract: In an optical transmission apparatus, optical power of each of wavelength contained in a wavelength multiplexing signal is measured, a measured value of the optical power of each wavelength is compared with a predetermined threshold value, a total value of the measured values of the optical power, which are equal to or larger than the threshold value, is calculated as a total value of signal beam power, and a total value of the measured values of the optical power, which are less then the threshold value, is calculated as a total value of ASE power. The number of the measured values of the optical power, which are equal to or larger than the threshold value, is calculated as a wavelength count of the signal beams contained in the wavelength multiplexing signal. A signal-to-ASE ratio is calculated from the total value of the signal beam power and the total value of the ASE power.

Abstract: There is provided an optical amplifier including a Raman amplification medium, a rare earth doped fiber located at a latter stage of the Raman amplification medium, a first pump light outputting unit for outputting pump light with a plurality of wavelengths, a variable distribution element for distributing the pump light with the plurality of wavelengths, outputted from the first pump light outputting unit, to the Raman amplification medium and the rare earth doped fiber in a variable distribution ratio for each wavelength, and a control unit for individually controlling the distribution ratio of the pump light with the plurality of wavelengths in the variable distribution element and the power of the pump light with the plurality of wavelengths from the first pump light outputting unit in accordance with a wavelength arrangement of each of signal lights wavelength-multiplexed into the wavelength-multiplexed signal light.

Abstract: An object of the present invention is to provide at low cost, a highly functional and small size optical amplifier, which realizes a polarization mode dispersion (PMD) compensation function and an optical amplifying function, with a simple construction.

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: Multi-wavelength light, including a plurality of segments of light signal with a different wavelength each, is inputted into a Raman amplification fiber. Pumping light generated by a pumping light source is supplied to the Raman amplification fiber in the opposite direction of the transmission direction of the multi-wavelength light. An auxiliary light source generates auxiliary light. An auxiliary light control circuit adjusts the optical power of the auxiliary light with a prescribed response time, based on the change in input power of the multi-wavelength light. The auxiliary light is supplied to the Raman amplification fiber in the same direction as the transmission direction of the multi-wavelength light.

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: In one of control methods of a bidirectional pumping type Raman amplifier according to the present invention, the power of a pumping light supplied to a rare-earth element doped optical fiber is increased or decreased, and a transmission wavelength characteristic of a dynamic gain equalizer is controlled according to a change in a gain wavelength characteristic occurring due to the increase or decrease of the power of the pumping light, to thereby extend a signal light band to either a short wavelength side or a long wavelength side. As a result, it becomes possible to realize a signal light band extension service at a low cost.

Abstract: An object of the invention is to provide an optical multiplexing method and an optical multiplexer, capable of fixing lights of different wavelengths at required wavelengths to stably multiplex them with a simple optical circuit configuration. To this end, in the present optical multiplexer, there is provided a tilted FBG, which is formed on an optical fiber through which a first light is propagated, with a grating direction thereof being tilted to an axial direction of the optical fiber, and has the sufficiently high reflectance to a second light (multiplexed light) of a wavelength different from that of the first light. The multiplexed light emitted from a light source is irradiated to the tilted FBG, via a free space from an angle direction determined according to a grating pitch of the tilted FBG and the wavelength of the multiplexed light, to be coupled within the optical fiber.

Abstract: In an optical amplifier of the invention, a WDM signal light is separated into N components by a demultiplexer after which each component is amplified by N optical amplifier sections, and the output light level of each optical amplifier section is controlled to a constant level by respective control circuits and multiplexed in a multiplexer. At this time, in the demultiplexer, the bandwidth of the signal light output from each of the output ports is designed to have a different value, so that inter-wavelength deviation in the optical output level that occurs in each of the optical amplifier sections, falls within a preset range. Moreover, the constant output control of each control circuit is performed by individually adjusting the gain of each of the optical amplifier sections in relation to fluctuations in the power level without channel number changes of the WDM signal light input to the demultiplexer.

Abstract: A control apparatus comprises a light monitoring unit for dividing a signal wavelength band into at least a band in which output light power of an optical amplifier tends to decrease at an decrease in the number of signal wavelengths and a band including a gain deviation band, and for monitoring inputted light power for the individual divided bands, a calculation unit for obtaining the number of signal wavelengths in the individual divided bands based on a monitor result, and a target gain correction unit for correcting a target gain based on a result of the calculation. This suppresses a transient variation of signal light level due to SHB or SRS at a high speed with a simple configuration without deteriorating noise characteristic, thus enabling optical amplifiers to be further disposed in a multi-stage fashion, which can lengthen the transmission distance of a transmission system including an optical add/drop unit.

Abstract: There is provided an optical amplifier comprising a Raman amplifying section, a rare earth element doped fiber amplifying section to be disposed in the case where the number of operating channels exceeds the number of allowable channels A, and a control section. And the control section controls the wavelength of pumping light of the Raman amplifying section such that the signal light of the entire band is able to be amplified, in the case where the number of operating channels is equal to that of allowable channels A or less, and whereas the control section controls the wavelength of pumping light of the Raman amplifying section such that the signal light of the band located out of the amplifying band of the rare earth element doped fiber amplifier is able to be amplified, in the case where the number of operating channels becomes greater than the number of allowable channels A.