Abstract: An optical apparatus connected to an up and a down transmission lines, comprising an optical amplifier including an optical amplification medium and an excitation light source. The excitation light source supplies an excitation light to the optical amplification medium. An optical supervisory channel (OSC) unit receives OSC optical signals from, and transmits the OSC optical signals to, the up and the down transmission lines. If an output power decrease of the excitation light source due to an random failure is detected, the excitation light is kept unchanged and the OSC unit transmits information of the random failure of the excitation light source via the OSC optical signals to the up and the down transmission lines, and if the OSC unit receives information of an random failure of an excitation light source in another optical apparatus, the output light power of the excitation light source is increased.

Abstract: In an optical transmission node network in which a first optical transmission node is connected with a second optical transmission nodes through an optical fiber cable and automatic optical output (APSD: Automatic Power Shut-Down) control is activated, after the APSD control is brought into an inhibited status, if an optical conduction to the second optical transmission node is detected, the APSD control inhibited status is canceled. In this way, if an optical transmission fiber is resorted (reconnected) after optical output power measurement or the like is carried out, the APSD control inhibition status (invalid status) is canceled for automatically restoring the APSD control activated status. Thus, optical output can be prevented from being inadvertently emitted at a high energy level from the optical fiber cable.

Abstract: A connection failure detection circuit that detects incomplete connection between printed circuit boards. A supervisory signal source is mounted on a first printed circuit board to produce a supervisory signal. A supervisory signal receiver is mounted on the first or second printed circuit board to receive the produced supervisory signal and determine whether the received supervisory signal carries expected logical values. Wiring lines are arranged so as to form a signal path that crosses connectors between the first and second printed circuit boards at at least one point.

Abstract: An optical signal propagating through a transmission line of a multimode fiber is branched by an MMF coupler of a reception device, and the intensity of the signal is detected by a MMF monitor PD. After connecting from the multimode fiber to a single-mode fiber, the optical signal is branched by a SMF coupler, and the intensity of the optical signal after the connection by a SMF monitor PD is detected. A coupling loss is calculated from the two detection results and the status of the occurrence of an error rate is estimated from the obtained coupling loss.

Abstract: A controller monitors output level variation rate of excitation light outputted by a light source in accordance with a drive current of the light source and provided to a rare-earth doped amplifying medium so that a signal light is amplified as the signal light travels through the amplifying medium. In an embodiment, the controller decreases the drive current when the monitored output level variation rate is larger than a threshold value, to thereby reduce power level of the outputted excitation light and thereby delay progress of degradation of the light source indicated by the monitored output level variation rate being larger than the threshold value.

Abstract: A chromatic dispersion compensation control method for compensating the chromatic dispersion of an optical transmission path with a variable dispersion compensator inserted in the optical transmission path is disclosed.

Abstract: Occurrence of a reception error and breakdown of a device are prevented by absorbing an optical surge that occurs at the time of an instantaneous interruption of light. Dummy light having a wavelength at which a Raman gain is obtained when the wavelength of a main signal is assumed to be the wavelength of the pump light of a Raman amplifier is combined in a combiner with the main signal, and the combined light is introduced into an optical fiber where, by exploiting the SRS effect, the energy of the optical surge occurring in the main signal is absorbed into the dummy light, thus absorbing the optical surge.

Abstract: The present invention provides provide a light power adjusting method, an optical transmitter, and an optical receiver suitable for ensuring high data transmission quality by preventing the rapid increase in SBS which occurs when the light power exceeds a predetermined value. The incident light power with which the SBS-induced backward propagating light included in the reflected light returned from the optical transmission line rapidly increases, i.e., the light power threshold is calculated. By setting the power of the light incident on the optical transmission line at a value equal to or smaller than the thus calculated light power threshold, the rapid increase in the SBS-induced backward propagating light, which is a nonlinear phenomenon of the optical fiber, is prevented.

Abstract: Equipped between a transmitter 20 and an optical multiplexer module 25 of a division/multiplexer unit 24 are band-pass filters 23-1 through 23-m letting only a light of right wavelength pass while reflecting other wavelengths light. The transmitter 20 is equipped with a reflection light monitor 26 for monitoring a reflection light from the band-pass filters 23-1 through 23-m for examining an intensity of a reflection light. A wavelength of a light oscillated by a tunable laser diode (LD) unit 21 is controlled so as to make the intensity of the light smaller than a threshold value.

Abstract: A reliable optical transmission system with an improved signal control mechanism that avoids abrupt power variations of light beams, thereby preventing optical supervisory channel (OSC) signals from experiencing errors. An optical amplifier amplifies main signals under the control of an optical amplifier controller, which spends a first predetermined time to raise the output power of the optical amplifier up to a desired level. A pump light source produces a pump beam for injection to a fiber-optic transmission line so as to make it serve as an amplifying medium. The pump light source is controlled by a pump light source controller that spends a second predetermined time to raise the pump beam to a desired power level. This stepwise start-up process of the amplifier power and pump beam power prevents OSC signals from experiencing abrupt power variations.

Abstract: The present invention provides provide a light power adjusting method, an optical transmitter, and an optical receiver suitable for ensuring high data transmission quality by preventing the rapid increase in SBS which occurs when the light power exceeds a predetermined value. The incident light power with which the SBS-induced backward propagating light included in the reflected light returned from the optical transmission line rapidly increases, i.e., the light power threshold is calculated. By setting the power of the light incident on the optical transmission line at a value equal to or smaller than the thus calculated light power threshold, the rapid increase in the SBS-induced backward propagating light, which is a nonlinear phenomenon of the optical fiber, is prevented.

Abstract: The invention is aimed at providing a simple noise light elimination technique capable of eliminating noise light components contained in a signal light, together with wavelength components same as for the signal wavelength, with the condition of the light remaining as is, and an optical transmission system. To this end, an optical transmission system applied with a noise light elimination method according to the present invention comprises a high output type optical repeater and a noise light elimination unit for each required repeating span. This noise light elimination unit includes a dummy transmission path that, when a light of a power exceeding a threshold value is input, generates a return light due to stimulated Brillouin scattering (SBS). The signal light amplified in the optical repeater up to the power exceeding the threshold value is input to the dummy transmission path via an optical input/output section of the noise light elimination unit.

Abstract: An optical signal propagating through a transmission line of a multimode fiber is branched by an MMF coupler of a reception device, and the intensity of the signal is detected by a MMF monitor PD. After connecting from the multimode fiber to a single-mode fiber, the optical signal is branched by a SMF coupler, and the intensity of the optical signal after the connection by a SMF monitor PD is detected. A coupling loss is calculated from the two detection results and the status of the occurrence of an error rate is estimated from the obtained coupling loss.

Abstract: In an optical transmission node network in which a first optical transmission node is connected with a second optical transmission nodes through an optical fiber cable and automatic optical output (APSD: Automatic Power Shut-Down) control is activated, after the APSD control is brought into an inhibited status, if an optical conduction to the second optical transmission node is detected, the APSD control inhibited status is canceled. In this way, if an optical transmission fiber is resorted (reconnected) after optical output power measurement or the like is carried out, the APSD control inhibition status (invalid status) is canceled for automatically restoring the APSD control activated status. Thus, optical output can be prevented from being inadvertently emitted at a high energy level from the optical fiber cable.

Abstract: A Raman excitation control method enabling to reduce the number of couplers and photodetectors (PD) for providing an optical transmission unit with reduced cost The method is provided for use in optical amplification to amplify an optical signal using Raman excitation light fed into an optical transmission line. A backward light of a laser diode producing the Raman excitation light is monitored by an optical back power monitor. The monitored power value is compared with an initial set value stored in a memory for the laser diode. Based on this comparison result, a feedback control is performed against the light emission power of the laser diode.

Abstract: A diagnosing method and apparatus non-destructively performing damage evaluation of a piled up structure of conductive materials by using acoustic waves. The diagnosing method according to the present invention includes the steps of placing an electro-magnetic acoustic transducer 20 out of contact with a piled up structure 34 of conductive materials 32 and 34 piled up with a non-conductive interface 33 (35) interposed therebetween, transmitting ultrasonic waves from one side 31 of the piled up structure by the electro-magnetic acoustic transducer 20, receiving ultrasonic waves reflected from the other side of the piled up structure, and diagnosing a damaged condition of the piled up structure on the basis of the ultrasonic velocity and attenuation of the received ultrasonic waves.

Abstract: Disclosed herein is a method including the steps of wavelength division multiplexing a plurality of optical signals having different wavelengths to obtain resultant WDM signal light; transmitting the WDM signal light by an optical fiber transmission line; supplying reference light having a predetermined wavelength to the optical fiber transmission line; generating four-wave mixing in the optical fiber transmission line by the interaction of the WDM signal light and the reference light; detecting the power of light generated as the result of the four-wave mixing; and controlling the power of the WDM signal light to be supplied to the optical fiber transmission line according to the power detected. According to this method, the effect of four-wave mixing can be suppressed.

Abstract: A reliable optical transmission system with an improved signal control mechanism that avoids abrupt power variations of light beams, thereby preventing optical supervisory channel (OSC) signals from experiencing errors. An optical amplifier amplifies main signals under the control of an optical amplifier controller, which spends a first predetermined time to raise the output power of the optical amplifier up to a desired level. A pump light source produces a pump beam for injection to a fiber-optic transmission line so as to make it serve as an amplifying medium. The pump light source is controlled by a pump light source controller that spends a second predetermined time to raise the pump beam to a desired power level. This stepwise start-up process of the amplifier power and pump beam power prevents OSC signals from experiencing abrupt power variations.

Abstract: A Raman excitation control method enabling to reduce the number of couplers and photodetectors (PD) for providing an optical transmission unit with reduced cost. The method is provided for use in optical amplification to amplify an optical signal using Raman excitation light fed into an optical transmission line. A backward light of a laser diode producing the Raman excitation light is monitored by an optical back power monitor. The monitored power value is compared with an initial set value stored in a memory for the laser diode. Based on this comparison result, a feedback control is performed against the light emission power of the laser diode.

Abstract: Disclosed herein is a method including the steps of providing an optical fiber transmission line for transmitting signal light; optically connecting a Raman amplifier having a pumping source for outputting pump light propagating in a direction opposite to the propagation direction of the signal light to the optical fiber transmission line; detecting the reflection of the pump light at a connection point between the Raman amplifier and the optical fiber transmission line; and controlling the Raman amplifier according to the reflection detected in the detecting step. According to this method, a lump loss can be easily detected in the case of performing Raman amplification, and any problem due to the lump loss can be prevented.