Abstract: Provided is a multi-value optical transmitter in which a DC bias may be controlled to be stabilized so as to obtain stable optical transmission signal quality in multi-value modulation using a dual-electrode MZ modulator. The multi-value optical transmitter includes: D/A converters for performing D/A conversion on first and second modulation data which are set based on an input data series, so as to generate a first and a second multi-value signal, respectively; a dual-electrode MZ modulator including phase modulators for modulating light from a light source based on the first multi-value signal and the second multi-value signal, so as to combine optical signals from the phase modulators to output the optical multi-value signal; an optical output power monitor for detecting average power of the optical multi-value signal; and a DC bias control unit for controlling a DC bias for the dual-electrode MZ modulator, so as to maximize the average power.

Abstract: A quantum key delivery system includes an optical circulator, an optical low-pass filter, optical splitters, and first and second optical couplers arranged for outputting various wavelength components including correlated-photon pair wavelength components outputted from an optical loop path. The first and second optical couplers output light beams, which are sent over first and second quantum channels to first and second recipients, respectively. Other optical splitters are adapted to output light rays, from which first and second control signals are produced. From auxiliary idler light components transmitted over the first and second quantum channels, clock signals are extracted. The system thus extracts a clock signal for detecting arrival of photons, and stably operates with an expected value of the number of generated correlated photon pairs maintained at a substantially constant value.

Abstract: A system and method are provided for controlling the pre-emphasis applied to an optical signal, in which the output level of individual transmitters is controlled in order to reach a pre-defined desired value of a quality metric. Transmitters are able to adjust their output power without external control in such a way as to optimise the power distribution across the system.

Abstract: Included are a first modulator, a second modulator, a first optical amplifier that amplifies an output of the first modulator at an amplification factor based on a first bias signal, a second optical amplifier that amplifies an output of the second modulator at an amplification factor based on a second bias signal, an optical phase adjuster that phase-rotates an output of the second optical amplifier, an optical multiplexer that multiplexes an output of the first optical amplifier with an output of the optical phase adjuster, and a second bias corrector that generates a first pulse signal and a second pulse signal, which are complementary to each other, and obtains a first bias value and a second bias value based on a change of strength of an output signal of the optical multiplexer. The first and second pulse signals are superimposed on the first and second bias signals, respectively.

Abstract: An optical signal transmitter of direct modulation, a method for transmitting optical signals, and an optical network are provided. The optical signal transmitter includes a laser diode operating at a bias current above a lasing threshold of the laser diode; a modulating device applies a modulation signal to the diode to produce a first output optical signal having first and second signal power levels; and a power level discriminator. The power level discriminator, from the received first output optical signal, generates a second output signal of significantly improved extinction ratio by reducing power of one of the first and second signal power levels of the first output optical signal.

Abstract: An optical transceiver includes an optical transmitter. The optical transmitter varies the wavelength of its output beam in accordance with the setting of a digital to analog converter. Two split beams emerging respectively from beam splitters are introduced into a photodetector and a wavelength filter, respectively. A quotient is calculated by dividing the digital value output from an analog to digital converter (ADC) by the digital value output from another ADC. A memory address m is then determined based on this quotient without making any calculation for compensating for the imperfect characteristics of the wavelength filter. A wavelength notification value is then selected from a wavelength notification table based on the determined memory address m, and sent to the system host.

Abstract: An optical transmission device in which: a first cyclic filter with a fixed transmission wavelength characteristic and a second cyclic filter with a variable transmission wavelength characteristic are combined, and the transmission wavelength characteristic of the second cyclic filter is changed according to a target wavelength, to thereby control the relative phase relationship of the transmission wavelength characteristics of the first and second cyclic filters. Moreover a light source is controlled according to a monitored value of the transmittance of the second cyclic filter with respect to the control target light, to thereby match the wavelength of the control target light with the target wavelength. Consequently, it is possible, with a simple configuration using a combination of two cyclic filters, to variably control wavelength at arbitrary wavelength intervals at a high level of precision.

Abstract: A method for stabilizing multi-channel optical signal wavelengths includes the following steps. A first detecting signal is stacked on a plurality of driving signals in sequence. A plurality of optical signals generated after being driven by the plurality of driving signals is combined into one optical total signal. A wavelength detection is performed on the optical total signal. A second detecting signal with a frequency band the same as that of the first detecting signal is extracted from the signals obtained after the wavelength detection. The wavelength of the optical signal in the corresponding channel among the multiple channels is controlled according to the second detecting signal. A device for stabilizing multi-channel optical signal wavelengths is also provided. Using the above method or device, the multi-channel optical signal wavelengths can be stabilized, which requires less elements, and has a simple circuit structure, a high integration level, and a low cost.

Abstract: A WDM transmission apparatus to receive or relay WDM light in a WDM transmission system, includes a measuring unit configured to measure an optical level of each channel transmitted by the WDM light; an adjusting unit configured to adjust a resolution of the measuring unit; and a processing unit configured to obtain, for each channel, optical level information which represents an optical level respectively measured with a resolution corresponding to a bit rate of a transmission signal of each channel.

Abstract: An apparatus and method are disclosed for maximizing interference contrast in an interferometric quantum cryptography system to detect eavesdropping by utilizing a tunable emitter station in communications with a receiver station via a quantum communications channel and a “public” communications channel. The tunable emitter station tracks and compensates for interferometer drifts by adjusting the interference contrast of the QC system to minimize or eliminate inherent perturbations induced into key bit transmissions. Tuning of the photo emitter's output wavelength is accomplishable using temperature and/or drive current adjustment of the emitter's tunable optical subsystem.

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: An infrared transmitter transmits a signal via an infrared ray. The infrared transmitter includes: a signal converter for converting the signal into an infrared signal; an oscillator for oscillating a carrier frequency of the infrared signal; a controller for adjusting a cutoff frequency of a filter according to the carrier frequency; and the filter provided between the oscillator and the signal converter to reduce a spurious signal of a carrier wave. The cutoff frequency of the filter is adjusted by the controller.

Abstract: Techniques for controlling a light source in a wavelength division multiplexed passive optical network (WDM-PON) are disclosed. In one particular exemplary embodiment, the techniques may be realized as an apparatus for controlling a light source in a wavelength division multiplexed passive optical network (WDM-PON). The apparatus may include a digital signal processing device configured to output a pilot tone signal. The apparatus may also include an amplifier configured to modulate a modulation current and the pilot tone signal, and output an amplitude modulated signal. The apparatus may further include a capacitor configured to AC couple the amplitude modulated signal to a bias current applied to a light source; and a monitoring photodiode configured to detect an output optical signal of the light source and transmit the detected output optical signal to the digital signal processing device to control the output optical signal of the light source.

Abstract: An optical communication apparatus includes an optical signal transmitter for outputting an optical signal, an optical switch device for switching a route of the optical signal, a drive controller for supplying a drive current for controlling a route switching to the optical switch device, a cooling device for cooling the optical switch device on the basis of a control signal, a temperature controller for transmitting the control signal to the cooling device in order to keep a measured temperature at a specific temperature, where the measured temperature is related to a temperature of the optical switch device.

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: An wave division multiplexed (WDM) optical transmitter is disclosed including a directly modulated laser array and a planar lightwave chip (PLC) having a plurality of OSRs that receive outputs of the laser array and increase the extinction ratio of the received light. An optical multiplexer receives the outputs of the OSRs and couples them to a single output port. The multiplexer has transmission peaks through its ports each having a 0.5 dB bandwidth including the frequency of a laser in the array. The optical multiplexer may be embodied as cascaded Mach-Zehnder interferometers or ring resonators.

Abstract: An apparatus for generating a dispersion compensation signal includes a splitting module for splitting a data signal to be transmitted into N channels of data signals; N pre-processing modules for adjusting in frequency domain the phases and amplitudes of the N channels of data signals and outputting N channels of pre-warped electrical signals; an optical carrier generating module for generating N channels of coherent optical carriers; N electro-optic modulators for modulating the N channels of coherent optical carriers based on the N channels of pre-warped electrical signals and generating N channels of pre-warped optical signals; an optical coupling module for coupling the N channels of pre-warped optical signals into a dispersion compensation optical signal. By pre-processing the data signals, the present disclosure may allow the use of existing devices to generate a dispersion compensation signal so that the bandwidth requirement set by prior art on the electrical device is reduced.

Abstract: A tunable photonic channelizer includes an optical signal generator and an optical modulator. The optical modulator receives a first optical signal as an input from the optical signal generator and modulates the first optical signal to create a second optical signal. The tunable photonic channelizer includes an optical filter that is selectively tunable. The optical filter receives the second optical signal, filters the second optical signal, provides a third optical signal as a filtered version of the second optical signal. The tunable photonic channelizer includes a feedback loop between the optical filter and the optical signal generator to provide temperature and/or environmental feedback from the optical filter to the optical signal generator to enable the first optical signal to float in relation to the temperature and/or environmental feedback.

Abstract: An optical transceiver calibration system and manufacturing method to fabricate a dual closed loop control transceiver are provided. The calibration system and method includes measuring an operating temperature and determining operational parameters based upon the operating temperature. The operational parameters may include, for example, a target power for transmitting a digital one, a target power for transmitting a digital zero, a modulation current, and a bias current. A bias may be added to the temperature to account for the difference between the temperature at the temperature sensor and the optical equipment. The operational parameters are preferably calculated independently of each other and are used as initial values during operating modes and allow the control loop to converge more quickly. The optics data is may be scanned electronically via bar code or some other electronic format prior to test. The software residing on the module then calibrates and configures the transceiver.

Abstract: An aspect of the embodiments utilizes an optical transmission apparatus which includes a rough adjustment execution portion that monitors a bit error rate of an optical signal for set values of a dispersion compensator where the set values have been set less closely to each other within a dispersion compensation control range than when a wavelength dispersion value set in the dispersion compensator is determined, and carries out a rough adjustment to determine a comparison threshold value used to set the wavelength dispersion value based on the monitored bit error rate, and a fine adjustment execution portion that monitors the bit error rate for the dispersion compensator the set values have been set more closely to each other, and carries out an adjustment to determine a wavelength dispersion value corresponding to the midpoint between the two acquired bit error rates as the wavelength dispersion value of the dispersion compensator.

Abstract: An apparatus for detecting wavelength drift and a system and method for locking wavelengths are disclosed herein so that multiple optical modules can share a wavelength locking apparatus without any wavelength selecting module. The output signals of only one optical module are scrambled at a time, and the identifier information carried in the optical signals output by different optical modules is the same, for example, the same frequency is applied to scrambling of every optical signal. Therefore, the scrambling apparatus is simplified, and the interference between scrambling signals is eliminated. Because no mechanical or electrical apparatus is used for controlling the wavelength switching, the cost is reduced, the locking speed is increased, the accuracy of signal processing is improved, and the precision of wavelength locking is enhanced.

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: An optical transmitter may include a tunable signal source configured to emit a signal to an optical fiber system; a back scatter detector for measuring an amount of back scatter observed following injection of the signal to the optical fiber system; and control logic. The control logic may be configured to cause the tunable signal source to scan through a range of wavelengths. Measured amounts of back scatter are received for each of the wavelengths. A wavelength corresponding to a peak back scatter amount may be identified and the tunable signal source may be set based on the identified wavelength.

Abstract: The present disclosure relates to a WDM-PON optical transmitter; and, more particularly, to a system for controlling a driving current of the WDM-PON optical transmitter. The present disclosure provides a driving current control system of an optical transmitter for use in WDM-PON including a plurality of optical transmitters, each transmitter generating and transmitting a transmittance optical signal based on a driving current and an optical multiplexer/demultiplexer for combining the optical signals received from the plurality of the optical transmitters to output a combined optical signal through a single common terminal, wherein the driving current is controlled based on the combined optical signal outputted from the common terminal.

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 photonic system and method are provided. The system includes an optical source configured to generate a carrier signal; and a modulator configured to modulate the carrier signal with a radio frequency, (“RF”) input signal to generate a modulated signal. The system also includes an optical filter configured to filter the modulated signal to generate a vestigial sideband modulated signal; and an optical detector configured to demodulate the vestigial sideband signal to generate an RF output signal. The system further includes a wavelength controller module configured to set an operating parameter of the optical source.

Abstract: There is provided an optical signal transmission apparatus having a stable dispersion compensation function without unnecessarily controlling a compensation value even when a main signal quality is deteriorated due to a factor other than dispersion or in the case of a transmission failure. When it is determined that a signal quality is deteriorated due to dispersion of a fiber by determining a control mode of a variable dispersion compensator by means of optical noise information and received power information in addition to bit error information of a received signal, a compensation value of the variable dispersion compensator is varied and a compensation value other than the dispersion of the optical fiber is held to an existing set value.

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: An optical transmitter using a chirp managed laser is disclosed. The optical transmitter compares, in advance to the ATC operation, the phases of the signal corresponding to the original output of the LD and the signal corresponding to that reflected by the filter. When the two signals are in phase, the transmitter lowers the target temperature of the ATC loop to shift the emission wavelength of the LD shorter until the two signals are out of phase.

Abstract: A tunable filter may be utilized to successively tune to different wavelengths. As each wavelength of the wavelength division multiplexed signal is extracted, it may be successively power monitored. Thus, power monitoring may done without requiring separate power monitors for each channel. This results in considerable advantages in some embodiments, including reduced size, reduced complexities in fabrication, and reduced yield issues in some embodiments.

Abstract: An optical communication system comprising a transmitter including a data register having a plurality of outputs, each output comprising a separate data channel, a plurality of signal processors, each signal processor corresponding to a data, a plurality of laser modules, each laser module coupled to an output of a corresponding signal processor, wherein each laser module modulates the modified signal from its corresponding data channel onto an optical carrier having a selected wavelength, and an optical multiplexer coupled to an output of all the laser modules.

Abstract: The present disclosure relates to a WDM-PON (wavelength division multiplexed-passive optical network) optical transmitter; and, more particularly, to a system for controlling driving current of the WDM-PON optical transmitter. The present disclosure provides a driving current control method of the optical transmitter for in use in the WDM-PON, including: setting an attenuation value of a variable optical attenuator to X; detecting an optical power Px received by a monitoring photo diode of the optical transmitter; setting an attenuation value of the variable optical attenuator to Y; detecting an optical power Py received by the monitoring photo diode of the optical transmitter; calculating an optical power Pout of an optical signal outputted from a common terminal of a 1×N optical multiplexer/demultiplexer based on the detected optical power Px and Py; and controlling a driving current based on the calculated optical power Pout.

Abstract: A circuit controlling the gain of an amplifier in an optical transmitter used for optical communication, including a detection circuit for measuring the power of the RF input to a laser; a gain controller or controlling a gain of an amplifier, and a switch connected to the gain controller, wherein the gain controller is adapted, in response to an activation of a switch, to: (i) automatically vary gain of the amplifier, and (ii) set the gain of the amplifier at a level corresponding to a reduction in the noise and/or distortion associated with the transmitter.

Abstract: The subject matter disclosed herein relates to determining a photosensor operating point.

Abstract: An algorithm is disclosed for performing channel balancing on channels between optical network elements within an optic-fiber communications system. The algorithm groups at least a portion of the channels into channel pairs, differentially adjusts the transmitter output power level of each of the channel pairs until the bit error ratio (BER) of at least one channel in each of the channel pairs exceeds a threshold, and records a respective power margin for each of the channels as the difference between the initial and final power levels. From the recorded power margins, a mean power margin is determined that is used to shift the transmitter output power level of each of the channels.

Abstract: An optical transmitter is disclosed in which the wavelength deviation occurred at the turning on from the disabled state to the enabled state by the negating of the Tx_Disable command is suppressed. The optical transmitter includes a semiconductor laser diode (LD) and an automatic temperature controller (ATC) circuit to drive the thermo-electric cooler (TEC). When the transmitter receives the Tx_Disable to start up the operation of the LD, a pulsed signal is generated in synchronizing with the transition of the Tx_Disable signal to momentarily enhance the cooling capacity of the TEC in order to compensate the increase of the temperature of the LD by the self heating, which prevents the output wavelength of the transmitter from deviating.

Abstract: A light detecting apparatus receives input light branched and output by a branching device, to calculate transmittance and reflectivity from the input light, acquires a wavelength corresponding to the calculated transmittance and reflectivity to calculate a gain value corresponding to input light intensity, acquires a driving current value corresponding to a calculated gain value and an acquired wavelength, and outputs an acquired driving current value.

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: The frequency chirp modulation response of a directly modulated laser is described using a small signal model that depends on slow chirp amplitude s and slow chirp time constant ?s. The small signal model can be used to derive an inverse response for designing slow chirp compensation means. Slow chirp compensation means include electrical compensation, optical compensation, or both. Slow chirp electrical compensation can be implemented with an LR filter or other RF circuit coupled to a direct modulation source (e.g., a laser driver) and the directly modulated laser. Slow chirp optical compensation can be implemented with an optical spectrum reshaper having a rounded top and relatively large slope (e.g., 1.5-3 dB/GHz). The inverse response can be designed to under-compensate, to produce a flat response, or to over-compensate.

Abstract: A system and method for suppressing beat noise in line monitoring equipment. A wavelength dither generator wavelength modulates a carrier wavelength of a test signal laser transmitter. A test code is modulated on the dithered carrier wavelength to provide a test signal output of the line monitoring equipment.

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 driver circuit is coupled to an optical waveguide transmitter. The driver circuit has a current generator that is in series with the transmitter, and a current robbing circuit is coupled to the transmitter. The current robbing circuit is to divert first and second amounts of current from the transmitter, in accordance with predetermined values of first and second bit streams, respectively, in which data is received to be transmitted. Other embodiments are also described and claimed.

Abstract: An optical transmitter is disclosed having a temperature stabilization system for an optical filter for maintaining constant the frequency response of the filter. The filter is mounted within a housing having a substantially higher thermal conductivity. The housing may include a copper-tungsten alloy and extend along the optical axis of the filter. The housing is in thermal contact with a thermo-electric cooler (TEC) and a temperature sensor. The TEC and temperature sensor are electrically coupled to a controller which adjusts the temperature of the TEC according to the output of the temperature sensor.

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: A method and apparatus for controlling a wavelength tuning of an optical source in an optical communication system. An operating temperature of an optical source is controlled and monitored to shorten a wavelength tuning time of the optical source generated in an optical source generator. When the current operating temperature reaches a final target temperature, an operating current is supplied to the optical source generator, and transmission of the operating current to the optical source generator is controlled and monitored. When the operating current reaches a final operating current, the wavelength tuning of the optical source is terminated. The operating temperature is adjusted by distinguishing between a smaller amount of temperature change and a larger amount of temperature change to prevent oscillation at the point of reaching the final target temperature, thereby minimizing the time taken for the output wavelength tuning.

Abstract: In the present invention, the extremely complicated setting and control and an extremely expensive optical component (wavelength locker) are not required, and optical output wavelength and optical output power can simply be set and controlled at a moderate price. At least one value for determining a dependence of the optical output wavelength on drive current and device temperature and at least one value for determining a dependence of the optical output power on drive current and device temperature in a light emitting device constituting first means 1 for emitting light are stored in fourth means 4.

Abstract: Systems and methods for generating spectrally efficient modulated optical signals are provided. Capacity of WDM optical communication links may be increased dramatically without changing the WDM channel plan thus minimizing modifications to optical amplifiers and passive optical components. A vestigial sideband (VSB) optical signal may be generated by filtering an amplitude modulated (AM) signal using a filter having a center frequency locked to the transmission frequency of a laser.

Abstract: An optical communications circuit has a communications light signal source and a heat pump coupled to cool the signal source. A controller monitors a current and a temperature of the signal source, and regulates the temperature. The controller updates a heat pump control limit parameter for the heat pump, based on the monitored current. Other embodiments are also described and claimed.

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.