Abstract: An optical communication system includes a first optical communication apparatus configured to insert a wavelength control signal in a main signal to produce a modified main signal; convert the modified main signal into a first optical signal; and transmit the first optical signal, and a second optical communication apparatus configured to receive the first optical signal; extract the wavelength control signal from the received first optical signal; determine a wavelength of a second optical signal based on the extracted wavelength control signal; and transmit the second optical signal to the first optical communication apparatus.

Abstract: A method for estimating optical power in an optical channel includes determining a tunable filter full-width, FWF, by measuring a response of the tunable filter to a known signal and mapping the response to frequency. A portion of an optical channel is coupled to an input of the tunable optical filter. A peak power response, PR, and a full width tunable filter response, FWR, to the optical channel are determined by measuring a response of the tunable filter to the optical channel and mapping the response to frequency. A signal power, PS, is then calculated from the peak power response, PR, and a ratio of the full width tunable filter response, FWR, to the tunable filter full-width, FWF.

Abstract: A laser unit, usable in a network interface unit (NIU), that includes a laser adapted to generate an optical signal having a wavelength, a temperature control system for establishing a temperature of the laser and a controller functionally connected to the temperature control system for setting the temperature, the controller configured to automatically vary the temperature between a high temperature and a low temperature different than the high temperature. Also an NIU and a system of NIU's including the laser and an associated method of controlling the laser.

Abstract: The invention relates to a method of operating a first optical network element (100), particularly an optical network unit, ONU, wherein said method comprises the following steps: performing a coarse tuning process (2100) of at least one transmission wavelength which is used by said first optical network element (100) for transmitting an optical signal to a second optical network element (200), particularly an optical line terminal, OLT, and performing a fine tuning process (2200) of said at least one transmission wavelength, wherein said fine tuning process (2200) is preferably performed after said coarse tuning process (2100).

Abstract: According to an aspect of an embodiment, an apparatus for controlling optical waveform, comprises: an input port for inputting a signal light having a modulating frequency and a signal light power; a pump light generator generating pulsed pump light having a frequency higher than the modulating frequency of the signal light and a pulsed pump light power; a nonlinear optical medium for transmitting the signal light from the input port and the pulsed pump light, the nonlinear optical medium having a gain of the signal light based on a nonlinear optical effect; and a power adjustor for adjusting a gain of the signal light saturates in the nonlinear optical medium by a nonlinear optical effect by adjusting at least one of the signal light power or the pulsed pump light power.

Abstract: A tunable element of a tuning module is receptive to optical data channels of a multiplexed optical data signal, each optical data channel having a different respective wavelength. The tunable element is responsive to different stimuli such that multiple passbands of the tunable element are defined, each passband corresponding to a respective stimulus and including no more than one wavelength of the optical data channels. An optical detector communicates with the tunable element and is receptive to no more than one optical data channel from the tunable element at any given time, an output of the optical detector is an electrical data signal that corresponds to the optical data channel received by the optical detector from the tunable element. A controller communicates with the tunable element and tunes the tunable element from one optical data channel to the other by causing application of a corresponding stimulus to the tunable element.

Abstract: An optical wavelength multiplexing system includes transmission-side and reception-side optical wavelength multiplexers, and terminal devices, which are connected to each other by optical fiber cables. Optical wavelength converters in the transmission-side optical wavelength multiplexers are connected to ports respectively. The optical wavelength converter converts an input optical signal into an arbitrary preset wavelength to generate a converted optical signal. The port has a predetermined wavelength preset therein. Each optical power level of input converted optical signals is compared with each optical power level of optical signals of respective wavelengths set in the ports. When a difference is detected in the comparison result, it is determined that an optical wavelength converter is incorrectly connected to the port.

Abstract: A signal treating apparatus for presenting an output signal representing an input signal over a signal range includes: (a) an input section receiving the input signal and presenting a first filtered signal limited to a first bandwidth at a first circuit locus; the input section presenting a second filtered signal limited to a second bandwidth at a second circuit locus; (b) an amplifying unit receiving the first filtered signal and presenting an increased gain signal at an amplifier output locus; (c) a detector coupled with the amplifier output locus and presenting third bandwidth-limited signal limited to a third bandwidth less than the first bandwidth at a third circuit locus; and (d) a combining section coupled with the second and third circuit loci and presenting a resulting signal related with the second filtered signal and the third filtered signal; said resultant signal being said output signal.

Abstract: Apparatus and methods for using a tunable optical source in safety curtain applications provide for enhanced operation of the safety curtain. In an embodiment, a safety curtain includes a transmit unit and a receive unit to operate as the safety curtain, where a single tunable light source generates different wavelengths of light and a single detector is used to detect the generated light.

Abstract: There is provided a wavelength division multiplexing transmission system and apparatuses used therein, in which a remote apparatus to be newly added to a station apparatus autonomously sets a wavelength to be used in the remote apparatus, thereby avoiding the need for presetting a wavelength to be used in the remote apparatus. The remote apparatus includes wavelength determining means that determines an available wavelength on the basis of an optical signal received from the station apparatus. The wavelength determining means may determine the wavelength of an unreceived optical signal as the available wavelength or may determine the wavelength of a received optical signal as the available wavelength, and may set that wavelength as a transmission and reception wavelength to be used in the remote apparatus.

Abstract: Described is a method for controlling the wavelength of a laser in a wavelength division multiplexed (WDM) system. The method includes generating broadband light having a dithered optical power and a wavelength spectrum that includes a plurality of WDM wavelengths. The broadband light is spectrally filtered to generate a spectrally-sliced optical signal having a wavelength spectrum that includes one of the WDM wavelengths. The spectrally-sliced optical signal is injected into a laser and a dithered optical power of the laser is determined. A parameter of the laser is controlled in response to the determination of the dithered optical power to thereby align a wavelength of the laser to the wavelength spectrum of the spectrally-sliced optical signal.

Abstract: The present invention provides systems and methods to convert a reconfigurable optical node multiple-input multiple-output (MIMO) system to a single-input single-output (SISO) system suitable for a proportional-integral-differential (PID) control process. Advantageously, the present invention allows PID control to apply to a MIMO optical node by modeling the node as two SISO systems. The present invention optimizes the division of gain and loss between components in the reconfigurable optical node. This provides means to control the net gain and loss of a series of components when the component chain being controlled includes those components that have a single action affecting multiple channels and components that affect only one channel. The present invention utilizes control of a single quantity of amplifier gain minus attenuation for each channel, and the coupling together of all channels in the amplifier which makes the channels inter-dependent.

Abstract: A system and method for spectral loading unutilized channels of a partially loaded WDM system may be used to suppress spectral hole burning (SHB). Dummy tones may be loaded at different loading wavelengths within the band of system wavelengths such that the loading wavelengths are associated with a subset of unutilized channels in the WDM system. The loading wavelengths may be selected and spaced based on a distortion in the gain spectrum of the partially loaded WDM system such that the dummy tones alter the distortion to provide a desired gain spectrum.

Abstract: In accordance with the teachings of the present invention, a system and method for managing wavelength drift in an optical network is provided. In a particular embodiment, the method includes receiving traffic in one or more optical channels transmitted by one or more transmitters, each channel having successive timeslots, each transmitter assigned to transmit in a channel in allocated timeslots in the channel. The method also includes determining whether the traffic received in a particular channel in a particular timeslot was transmitted by one of the transmitters that was not assigned to transmit in the particular channel.

Abstract: An optical transmitter that multiplexes a plurality of signal light each having less chirp characteristic by the CML technique is disclosed. The optical transmitter comprises a plurality of optical modules, a plurality of TEC controllers each driving the TEC in the optical module, a de-multiplexer that de-multiplexes the output of respective modules, an etalon filter, and a monitoring unit that monitors the component of the signal light output from respective modules. The TEC controller controls the temperature of the LD in the module such that two emission wavelengths of the LD each corresponding to the ON level and the OFF level is set in both side of one of the critical wavelengths of the etalon filter where the transmittance thereof becomes a maximum.

Abstract: Methods, systems and computer program products for countering the effects of four wave mixing are described. In one implementation, a controller can be used to shift an operating wavelength of an optical transmitter away from a zero-dispersion wavelength through which signals of the optical transmitter are transmitted. The controller can perform the shifting process while allowing sufficient margin for division multiplexing and minimal dispersion. The controller may determine an appropriate offset to be used for shifting the operating wavelength without subjecting the signals to a significant increase in undesirable effects such as dispersion, crosstalk and signal distortion which can impact the overall bit-error rate.

Abstract: Various embodiments of the present invention relate to systems and methods for monitoring and tuning detector and modulator resonators during operation. Aspects of the present invention use DC balanced coding of data in optical signals tune and monitor the performance of a resonator. Whether the resonator is being used as a modulator or a detector, the intensity of the light coupled into the resonator is DC balanced and varies as a function of the data being transmitted. Average intensity variations of the light scattered from the resonator are converted into an electronic feedback signal, which is used to determine appropriate levels of thermal and electronic tuning applied to the resonator.

Abstract: An apparatus and method is disclosed for producing and filtering optical and electrical waveforms. The apparatus includes an electro-optical modulator, an optical filter capable of modulating at least two spectral regions within the bandwidth of the electrical waveform, and an optical-to-electrical converter. The optical filter includes a spatial dispersion means, a spatial modulating means having the capability to substantially independently modulate a characteristic of each of a pair of optical spatial elements.

Abstract: A high-speed wavelength selectable optical source and a method thereof are disclosed. The wavelength selectable optical source includes at least one optical source having a multimode oscillation spectrum, a demultiplexer and an optical switch for extracting light having a certain selected wavelength. A certain wavelength can be selected among the multimode wavelengths using the demultiplexer and the optical switch, and thus the wavelength can discontinuously be tuned at high speed. Also, by making the light having the selected wavelength incident to the multimode optical source, the power of the output light can uniformly be maintained and maximized through injection locking.

Abstract: An inline repeater that uses a forward-pumped DRA that can use a pumping light source such as an FBG pumping light source and a fiber laser, which are the most commonly used, and an optical fiber communication system are realized.

Abstract: According to the invention, a very narrow-band transfer signal (LS) is generated by serially connecting a frequency modulator (2) and an amplitude modulator (4). The frequency modulator (2) is operated at a modulation index which at least largely suppresses the carrier signal (TS) while the amplitude modulator (4) suppresses the broadband portion of the spectrum by fading out the transfer signal (LS) during frequency-shift keying.

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: The invention relates to a method and a device for operating an optical transmitting device having a plurality of optical transmitters that can be driven independently. The method includes detecting the parameter values of the individual transmitters, comparing the parameter values determined with one another and/or with a prescribed comparison value, and selecting one of the transmitters for the communication operation of the transmitting device based on the comparison. The method further includes operating the transmitting device with the selected transmitter.

Abstract: A system and method using for wavelength monitoring and control in a WDM optical communication system. An aggregate channel monitor detects crosstalk between channels in the aggregate signal. Channel spacing may be modified by an element management system in response to the output of the aggregate channel monitor.

Abstract: Systems, apparatus and methods for implementing single-fiber optical ring networks based on double side band modulation.

Abstract: A system and method for detecting and correcting for thermal shifting of the passbands of an input filter of an optical receiver relative to the passbands of an output of an optical device, such as an optical router, where the router and the receiver are operating at remote locations and at different operating temperatures that cause thermal drifting of the passbands. In one implementation RF signals are impressed on optical signals transmitted by a transmitter to the optical router. Different frequency RF signals are impressed on each of the optical signals and the receiver uses the detected RF frequencies to cancel portions of optical signals that have drifted into adjacent passbands at the optical receiver. In another implementation a mechanically adjustable filter is employed at the receiver which is used to achieve a needed degree of shifting of the receiver passbands to compensate for passband misalignment between the router and the receiver.

Abstract: For transmitting information on an optical fiber, a plurality of information carrier channels at different carrier frequencies and a plurality of filling channels are used. The filling channels are transmitted together with the information carrier channels along the fiber. The total optical power of the information carrier channels and the filling channels transmitted on the fiber is maintained constant by compensating every change of the optical power of the information carrier channels by an inverse change of the optical power of the filling channels. The change of the optical power of the filling channels is distributed to the individual filling channels such that a minimum displacement of the center of gravity of the common spectrum of information carrier channels and filling channels results.

Abstract: An optical wavelength controlling method and a system thereof for an optical wavelength division multiplexing transmission system, wherein a plurality of wavelengths of channels are multiplexed and transmitted by an optical transmitting unit, and the multiplexed wavelengths are divided into the wavelengths of the channels by an optical receiving unit, are disclosed. The optical wavelength controlling method includes: a step of reducing optical power of the wavelength of a target channel, and transmitting the wavelengths; a step of evaluating channel crosstalk based on a code error rate of a channel adjacent to the target channel, and detecting a shift of the wavelength of the target channel; and a step of compensating for the shift of the wavelength of the target channel.

Abstract: A transponder in a wavelength division multiplexing apparatus detects a wavelength of a leak light (received light) having one of plural wavelengths multiplexed or divided by a WDM unit, the leak light having been received from the WDM unit when the transponder is connected to the WDM unit; determines a transmission wavelength which is a wavelength of a light to be transmitted to the WDM unit on the basis of the wavelength of the received light; and sets to convert the wavelength of the light to be transmitted to the WDM unit into the transmission wavelength, and transmit the converted light.

Abstract: There is provided a wavelength division multiplexing transmission system and apparatuses used therein, in which a remote apparatus to be newly added to a station apparatus autonomously sets a wavelength to be used in the remote apparatus, thereby avoiding the need for presetting a wavelength to be used in the remote apparatus. The remote apparatus includes wavelength determining means that determines an available wavelength on the basis of an optical signal received from the station apparatus. The wavelength determining means may determine the wavelength of an unreceived optical signal as the available wavelength or may determine the wavelength of a received optical signal as the available wavelength, and may set that wavelength as a transmission and reception wavelength to be used in the remote apparatus.

Abstract: A system and method for transmitting an optical signal. The system includes a first optical transmitter capable of transmitting a first optical signal under one or more first operating conditions, and the first optical signal corresponds to a first wavelength. Additionally, the system includes a second optical transmitter capable of transmitting a second optical signal under one or more second operating conditions, and the second optical signal corresponds to a second wavelength. Moreover, the system includes an optical multiplexer coupled to the first optical transmitter and the second optical transmitter and capable of generating a multiplexed optical signal, a detection component configured to determine at least whether the first optical transmitter satisfies one or more predetermined conditions, and a tunable optical transmitter capable of transmitting a third optical signal. The third optical signal corresponds to a third wavelength.

Abstract: Various methods, systems, and apparatuses in which a wavelength-division-multiplexing passive-optical-network includes a first broadband light source and a second broadband light source. The first broadband light source supplies an optical signal containing a first band of wavelengths to a first plurality of optical transmitters. The second broadband light source supplies an optical signal containing a second band of wavelengths to a second plurality of optical transmitters. A fiber is used for bi-directional transmission of optical signals in at least two different wavelength bands.

Abstract: A signal identification method for efficiently identifying Dense Wavelength Division Multiplexing (DWDM) channel modulation formats, signal powers, and center frequency detuning of signals that may be used in conjunction with telecom-grade monitoring equipment. The method utilizes least-square curve fitting estimates applied to a set of curves, each curve is characteristic of a modulation format and rate. For each least-square estimate an error value is calculated, and a curve fit with the least error is selected as the identified signal format for a signal.

Abstract: In a wavelength-division-multiplexing optical transmission system in which optical-node apparatuses that perform relay transmission of wavelength-division-multiplexed light are located at specified nodes in a main optical transmission path, an optical amplifier switches level control to constant-gain control when there is a notification of a change in the number of multiplexed wavelengths, and then after a specified amount of time restarts level control so that the level becomes a target level that corresponds to the actual number of wavelengths.

Abstract: An apparatus and method for extracting an optical clock signal are provided. The apparatus includes a first reflection filter selecting and reflecting only a first frequency component in an input optical signal; a first Fabry-Perot laser diode matching the first frequency component reflected by the first reflection filter with a predetermined output mode and outputting the first frequency component in the predetermined output mode; a second Fabry-Perot laser diode selecting a second frequency component in an input optical signal that has not been reflected but has been transmitted by the first reflection filter, matching the second frequency component with a predetermined output mode, and outputting the second frequency component in the predetermined output mode; and a photodetector receiving the first frequency component from the first Fabry-Perot laser diode and the second frequency component from the second Fabry-Perot laser diode and beating them to extract a clock signal.

Abstract: In a telecommunication system, channels of information are modulated onto respective carriers that are swept repeatedly across a frequency range in a time-staggered fashion so that, at any one time each carrier is at a different frequency. The carriers are multiplexed onto a single communications link and separated, on reception, by filters swept in synchronism so as to de-multiplex the signals.

Abstract: A wavelength tunable device for use in a wavelength division multiplexing (WDM) system comprising a display device for displaying at least one operating wavelength of the wavelength tunable device. The display device is electrically coupled to a control unit in the wavelength tunable device so as to display the tuned wavelength in real time. The wavelength tunable device may be, in exemplary embodiments, an optical transponder, wavelength division demultiplexer, or wavelength division multiplexer. In embodiments where the optical equipment has a plurality of tunable ports, the display device is adapted to display the operating wavelength of each tunable port.

Abstract: A transmitter (11) emits a single wavelength optical signal and transmits this as a wavelength channel (13) in a compound multiplex signal through the WDM network. The receiver (12) selects the single wavelength optical signal (21) from the compound multiplex signal using a band-pass filter. A wavelength fit detector (15) determines a feedback signal by correlating variations of the amplitude of the received signal with variations of the traffic density. This feedback signal is then returned to the transmitter (11) via a back channel (16) and serves to tune the wavelength of the single wavelength optical signal.

Abstract: An optical communication apparatus using a sub-carrier multiple access includes a laser diode for generating an optical signal with a central frequency, a temperature controller installed at a subscriber side for controlling a temperature of laser diode placed at a transmitting terminal, an optical coupler for coupling the optical signal outputted from the laser diode to an optical fiber and an optical receiver for receiving the optical signal outputted from the optical coupler. The central frequency of the optical signal outputted from the laser diode is changed in response to the change of the temperature controlled by the temperature controller.

Abstract: In an optical transmission system which can keep a flat pass characteristic within an optical signal modulation band, a spectrum of a dropped optical signal within a modulation band per channel is monitored, and non-flatness for the optical signal is compensated by detecting the non-flatness of a pass characteristic of a transmission line from the spectrum.

Abstract: Various methods, systems, and apparatuses is described in which a passive-opticalnetwork includes a first multiplexer/demultiplexer, a second multiplexer/demultiplexer, a wavelength tracking component, and a transmission wavelength controller. The first multiplexer/demultiplexer is located in a first location. The second multiplexer/demultiplexer is located in a second location remote from the first location. The wavelength tracking component determines the difference between the transmission band of wavelengths of the first multiplexer/demultiplexer and the second multiplexer/demultiplexer to provide a control signal to match the transmission band of wavelengths of the first multiplexer/demultiplexer and the second multiplexer/demultiplexer. The transmission wavelength controller alters an operating parameter of the first multiplexer/demultiplexer based on the control signal to control the transmission band of wavelengths of the first multiplexer/demultiplexer.

Abstract: An optical switch includes an optical source; a plurality of tunable optical resonators or tunable waveguides in optical communication with the optical source; and a tuning device configured to selectively route an optical beam from the optical source to at least one optical destination by tuning at least one of the optical resonators or tunable waveguides, in optical communication with at least one optical destination, to a wavelength characteristic of the optical beam.

Abstract: A system and method for detecting and compensating for thermal drift in an optical network in a manner that enables an increased number of optical channels to be used on a given optical medium, such as on a single optical fiber. A pair of narrow band, closely spaced optical signals from an optical transmitter function as a “temperature probe” signal. The two narrow band signals are centered within one passband of a filter of an optical device, such as an optical router. When the two narrow band signals are transmitted back to an optical receiver via the router, the magnitudes of the two signals are compared and a determination can be made as to the magnitude and direction of thermal drift of the passbands of the filter of the optical router.

Abstract: WDM optical tranmsmission equipment with redundant configuration includes a plurality of tranmitters. Each tranmitter includes active and standby panels including active and standby optical transmission circuits respectively having active and standby attenuators for controlling an attenuation amount of each output of the active and standby optical transmission circuits; and a coupler combining the outputs of the active and standby attenuators.

Abstract: A transmitter subsystem generates an optical signal which contains multiple subbands of information. The subbands have different polarizations. For example, in one approach, two or more optical transmitters generate optical signals which have different polarizations. An optical combiner optically combines the optical signals into a composite optical signal for transmission across an optical fiber. In another aspect, each optical transmitter generates an optical signal containing both a lower optical sideband and an upper optical sideband (i.e., a double sideband optical signal). An optical filter selects the upper optical sideband of one optical signal and the lower optical sideband of another optical signal to produce a composite optical signal.

Abstract: An optical control monitor and a method for adjusting for changes in optical signals transmitted through an optical network. The method comprises the steps of transmitting a set of optical signals through a network, each of the optical signals having a respective wavelength; and tracking changes to said set of signals by passing each of the signals through a filter having a bandpass function, and dithering the filter bandpass about the wavelengths of each of said set of signals to generate filter output signals. The filter output signals are used to adjust the network or the set of optical signals to compensate for said changes.

Abstract: The automatic dispersion compensation device of the present invention comprises a unit measuring the transmission quality of incoming optical signals for one or more channels input from a transmission line and a unit separating and detecting the transmission quality degradation due to chromatic dispersion, in the measurement result of the unit from degradation due to other factors and controlling a variable chromatic dispersion compensator (VDC) in such a way as to compensate for that degradation.

Abstract: A wavelength selecting apparatus includes a wavelength selecting filter and that a monitoring filter are similar acousto-optic tunable filters; a light source that outputs light having a specific wavelength to the monitoring filter; a light receiving unit that detects a wavelength of light that has passed the monitoring filter; and a control unit that outputs, to the wavelength selecting filter, a control signal having a control frequency to selectively pass light of a desirable wavelength. The light source includes a light emitting element that emits light of a wide wavelength band; and an optical filter having at least two transmission bands through which the light passes to the monitoring filter. The control unit, based on at least two wavelengths of the light output by the light source, outputs a control signal having a control frequency corresponding to the desirable wavelength.

Abstract: This invention provides a system that combines a wavelength multiplexer with an FM discriminator for chirp reduction and wavelength locker in a filter to produce a wavelength division multiplexed signal with reduced chirp. A partially frequency modulation laser signal is converted into a substantially amplitude modulation laser signal. This conversion increases the extinction ratio of the input signal and further reduces the chirp. A wavelength division multiplexing (WDM) method is used for transmitting high capacity information through fiber optics systems where digital information is carried on separate wavelengths through the same fiber. Separate transmitters normally generate their respective signals that are transmitted at different wavelengths. These signals are then combined using a wavelength multiplexer to transmit the high capacity information through the fiber optic system.

Abstract: A method and apparatus for controlling bias and alignment in an optical signal transmitter for providing intensity modulation and DPSK modulation to an optical signal, e.g. in an RZ-DPSK modulation format. Output power in dither signals applied to the bias signals may be detected by a low speed photodetector. One or more of the bias signals may be adjusted in a low speed control loop in response to an error signal obtained by mixing the detected signal with the low frequency dither signals.