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: An optical transmission system for performing frequency synchronization even with a client signal with low frequency accuracy, and for transmitting thereof by accommodating/multiplexing without causing a bit slip. A new overhead is added to the entire client signal, and the signal including the new overhead being stuffed is transmitted in conjunction with a plurality of stuffing bits as an optical signal wherein a data storing bit for a negative stuffing, a stuffing information notification bit, and a stuff bits inserting bit for a positive stuffing in the payload are defined in plurality as stuffing bits for adjusting clock frequencies of the client signal in this new overhead.

Abstract: In a transmission apparatus, a monitor unit monitors a signal level and generates a monitored value; a level control unit controls the level of the input signal in accordance with the monitored value; an output amplification unit amplifies and outputs the level-controlled signal; and a control unit controls unit operation statuses in accordance with setting information. The control unit recognizes the period of duration of a single level in the input signal, from the signal format given by the setting information, and performs variable control of at least one of a monitor time constant, a response time from the signal input to the monitor unit until the generation of the monitored value, and a level setting time constant, a response time from the input of the monitored value to the level control unit until the execution of level control, in accordance with the period of duration of the single level.

Abstract: An optical transmitter is disclosed wherein a modulating signal, such as an NRZ signal, encoding data is combined with a time derivative of the modulating signal and coupled to a directly modulated laser in order to generate artificial transient chirp in the output of the laser effective to substantially compensate for dispersion experienced by the output of the laser traveling through a dispersive medium such as an optical fiber. In some embodiments, the time derivative is added to the modulating signal only at the falling edges of the modulating signal.

Abstract: Described is a method of reducing transmitter error in an optical communications channel. An optical signal transmitted from an optical transmitter that has impairment due to transmitter error is processed to generate a digitally-equalized signal. A nonlinear characteristic of the digitally-equalized signal that relates to the transmitter error is determined. An optical control signal comprising data that are based on the nonlinear characteristic is transmitted to the optical transmitter. The optical transmitter modifies a transmitter parameter in response to the optical control signal to change the nonlinear characteristic and thereby reduce the impairment.

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: Provided is an optical transmission circuit capable of realizing a high-quality optical signal waveform with low power consumption. An optical transmission circuit (10) includes: a laser diode (800); a modulator (900) for supplying a differential modulation current to an anode terminal and a cathode terminal of the laser diode (800) through transmission lines (301 to 304); a current source (101) for supplying a forward bias current to the laser diode (800); and a magnetic sheet (wave absorber) (400) disposed so as to cover at least a part of the transmission lines (303 and 304). An impedance of the laser diode (800) is lower than characteristic impedances of the transmission lines (301 to 304) which are formed so that the characteristic impedances thereof are matched to an output impedance of the modulator (900).

Abstract: Provided herein are embodiments of a device, method of use and system for a low-cost analog multi-wavelength video distribution transamplifier for CATV and FTTH networks having a broadband overlay. The transamplifier embodiments described herein allow the use of multiple wavelengths to segment logical service groups in a CATV distribution system and a FTTH system having a broadband overlay.

Abstract: A method of transmitting information over a non-linear optical channel includes the step (152) of generating an information-bearing signal, preferably an OFDM signal, which includes a plurality of closely-spaced sub-carriers in the frequency domain. A time-varying phase modulation is determined (154), which is a first function, and preferably a linear function, of the transmitted optical power corresponding with the information-bearing signal. The information-bearing signal and the time-varying phase modulation are applied (156) to an optical source in order to generate a corresponding transmitted optical signal having substantially the stated transmitted optical power characteristic. The first function of transmitted optical power is selected so as to mitigate the effect of the non-linearity of the optical channel upon the transmitted optical signal.

Abstract: An equaliser (60) processes, in the electrical domain, a signal obtained from a path of an optical transmission system. The equaliser comprises N cascaded stages (where N?1). At least one of the stages comprises a cascade of a linear equalisation element (61) and a non-linear equalisation element (62). The equaliser (60) is able to compensate for both linear impairments, such as dispersion, and non-linear impairments. The cascaded linear and non-linear elements can simulate the effect of signal propagation through a fibre which has the opposite propagation parameters (e.g. attenuation, dispersion, non-linearity) to those of the propagation path experienced by a signal in the transmission system. The non-linear equalisation element (62) can be a non-linear phase rotator which rotates phase of an input signal proportional to the squared modulus of the input signal amplitude.

Abstract: A method of communicating digital information over a dispersive optical channel includes encoding the digital information into a plurality of data blocks, each of which includes a number of bits of the information. A time-varying electrical signal is generated which corresponds with each of said data blocks. The time-varying electrical signal is applied to an optical transmitter (122) to generate an optical signal which includes an asymmetrically amplitude limited transmitted signal modulated onto an optical carrier. The optical signal is then transmitted over the dispersive optical channel (106). At a receiving apparatus (104) the optical signal is detected to produce an electrical signal which corresponds with the asymmetrically amplitude limited transmitted signal.

Abstract: A method and apparatus is presented for reducing or eliminating pathological data patterns from signals for transmission over optical communications systems. One embodiment includes a decoder/deserializer configured to receive an encoded serial digital signal, a ditherer configured to dither a least significant bit of each digital data word, and a reserializer/encoder configured to serialize digital data and encode it, for example according to an applicable communication standard such as SMPTE 259M. The improvements may be provided in a single removable unit, such as a small form-factor pluggable (SFP) module compatible with existing optical communications equipment.

Abstract: A method and an apparatus are provided for use in a parallel optical transmitter or transceiver to compensate for variations in optical crosstalk in an optical output power monitoring system that are caused by lasers being enabled and/or disabled. In particular, the method and apparatus cause adjustments to be made to the reference value of each optical channel based on determinations of whether one or more lasers of the other optical channels have been disabled or enabled. By making these adjustments, the average optical output power level of each laser of each channel can be maintained at a desired or required level even if one or more of the lasers of one or more of the other channels is enabled or disabled.

Abstract: The invention relates to the field of optical transmission systems. In particular, the invention relates to a system and a method for adjusting an optical OFDM transmission system in a power optimized manner An optical OFDM transmitter (310) operating at an overall bit-rate is provided. It comprises an adjustable mapping unit (314) associated with one of N OFDM subcarriers, operable to map M bits of a digital input signal (360) into a constellation point, thereby yielding a subcarrier signal of the corresponding OFDM subcarrier. Furthermore, it comprises an adjustable transformation unit (315, 316), operable to transform the subcarrier signal to yield an electrical output signal. In addition, the OFDM transmitter comprises an electrical-to-optical converter (324, 325), operable to convert the electrical output signal into an optical output signal.

Abstract: The present invention relates to an optical modulation method and optical modulation system of a wavelength locked Fabry Perot-Laser Diode (FP-LD) by injecting a broadband light source (BLS) using mutual injection of FP-LDs. More specifically, the present invention relates to a novel modulation technology which embodies a wavelength locked FP-LD capable of being used as an economic light source in an optical network based on a wavelength-division multiplexing passive optical network (WDM-PON).

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 multimode optical fiber has an equivalent modal dispersion value (DMDinner&outer) of less than 0.11 ps/m for (??max×D)>0.07 ps/m as measured on a modified DMD graph. The modified DMD graph accounts for chromatic dispersion to ensure that the multimode optical fiber has a calculated effective bandwidth EBc greater than 6000 MHz-km when used with multimode transverse sources.

Abstract: An optoelectronic timing system includes an adaptive frequency generator system in which optical pulses are developed by a semiconductor laser. The pulses are directed into a number of time-quantifiable optical paths. Time quantification for a pulse is based upon the time required for a pulse to travel a particular length at the speed of light. Pulses are recombined at a nodal point and exhibit a numerical relationship with the periodicity of the issued pulse train equal to the numerical relationship between the lengths of the number of optical waveguides. A pulse detector and a regenerator are coupled to the semiconductor laser. A regeneration waveguide having a length equal to the longest of the optical paths is coupled to receive pulses from the laser.

Abstract: The present invention provides a system and method of optical communications that utilize coherent detection technique and optical orthogonal frequency division multiplexing for phase encoded data transmission. In particular the invention addresses a device and method for digital polarization compensation of optical signals with up to 100 Gb/s transmission rate received via an optical link. The polarization compensation operates in two modes: acquisition mode and tracking mode. The polarization recovery is performed at the receiver side using the received digital signal conversion into frequency domain and separate reconstruction of the polarization state in each spectral component.

Abstract: A transmitter (3) for generating a DQPSK-modulated optical signal, including: a splitter (7) for dividing an optical carrier signal into a first and second branch (8a, 8b), a first and second Mach-Zehnder interferometer (9, 10) in the first and second branch (8a, 8b), respectively, a phase shifter (11) in one of the branches (8b) generating a nominal phase shift of .pi./2, and a combiner (7?) for combining the optical output signals of the two branches (8a, 8b). The transmitter (3) has a feedback circuit (12) generating at least a first and second bias signal (15.1 to 15.3) for adjusting a bias of at least the first and second Mach-Zehnder interferometers (9, 10), the feedback circuit (12) includes a detector for generating at least a first and second feedback signal from a sample signal extracted from the optical signal after the combiner (7?), and for each bias signal: a local oscillator generating an auxiliary signal modulating the bias signal (15.1 to 15.

Abstract: An optical transceiver module configured for longwave optical transmission is disclosed. Significantly, the transceiver module utilizes components formerly used only for shortwave optical transmission, thereby reducing new component production and device complexity. In one embodiment, the transceiver module includes a transmitter optical subassembly including a laser capable of producing an optical signal. A consolidated laser driver/post amplifier including a first bias current source provides a bias current to the laser for producing the optical signal. A means for amplifying the bias current provided to the laser by the first bias current source is also included as a separate component from the laser driver/post amplifier. The means for amplifying in one embodiment is a field-effect transistor that is operably connected to the laser driver/post amplifier and configured to provide an additional bias current to the laser diode such that sufficient lasing operation of the laser is realized.

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: According to one embodiment, a microwave photonic band-stop (MPBS) filter uses an electrical input signal to drive an optical Mach-Zehnder modulator. A modulated optical carrier produced by the modulator is applied to an optical filter having at least two tunable spectral attenuation bands that are located substantially symmetrically on either side of the carrier frequency. The resulting filtered optical signal is applied to an optical-to-electrical (O/E) converter to produce an electrical output signal.

Abstract: An apparatus and method for controlling bias in an optical modulator is disclosed. The method is particularly applicable to controlling multi-wavelength modulators and wavelength-tunable transmitters. At a calibration stage, a desired optical performance of the modulator is achieved, and an amplitude of a peak-to-peak variation of the output optical signal at a pre-determined amount of dither is stored in a memory as a reference. At operating stage, a controller of the optical modulator adjusts a bias voltage of the modulator until the measured peak-to-peak optical signal variation matches the reference value stored at the calibration stage. For multi-wavelength modulators and tunable transmitters, the calibration is repeated at each wavelength, and corresponding peak-to-peak optical signal variations are stored in the memory.

Abstract: The present disclosure provides a multi-carrier optical transmitter, receiver, transceiver, and associated methods utilizing offset quadrature amplitude modulation thereby achieving significant increases in spectral efficiency, with negligible sensitivity penalties. In an exemplary embodiment, an optical transmitter includes circuitry configured to generate a plurality of optical subcarriers, a plurality of data signals for each of the plurality of subcarriers, and a plurality of modulator circuits for each of the plurality of subcarriers, wherein each of the plurality of modulator circuits includes circuitry configured to offset an in-phase component from a quadrature component of one of the plurality data signals by one-half baud period.

Abstract: A system is provided for electrical domain optical spectrum shaping. The system may include a laser, a modulator, a first electrical filter, and a second electrical filter. The laser may be configured to output an optical carrier signal. The modulator may be configured to modulate the optical carrier signal to output a modulated optical signal based on a first filtered input signal and a second filtered input signal received by the modulator. The first electrical filter may be configured to filter a first input signal to produce the first filtered input signal. The second electrical filter may be configured to filter a second input signal to produce the second filtered input signal.

Abstract: A method and system for improving the performance of a differential-phase modulated optical communication system is disclosed. The system comprises a demodulator having a tunable element to adjust the free-spectral range (FSR) thereof, and a tunable phase shifter to adjust a frequency of a signal passing therethrough.

Abstract: New method to control the optical transmitter is disclosed. The optical transmitter provides both of the ATC feedback loop and the APC feedback loop. When a failure occurs in the ATC feedback loop and the temperature sensor is unable to output an adequate signal any longer, the optical transmitter cuts the APC loop and operates the LD in constant conditions. The output of the monitor PD is transferred to the ATC loop to control the TEC based on the optical output of the LD.

Abstract: An electronic system comprises an automatic power control (APC) unit, an adjustment unit, and a calibration unit. The automatic power control (APC) unit receives a first input signal and a second input signal and generates an output signal. An adjustment unit coupled to the first input terminal of the APC unit generates a voltage offset according to an adjustment signal. The calibration unit provides the adjustment signal with a series of values. The calibration unit monitors the output signal until the output signal changes states.

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: There is provided an optical modulator capable of controlling the phase of a USB signal and the phase of an LSB signal of an optical FSK modulated signal. A modulation signal is applied to a main Mach-Zehnder electrode (or an electrode C) (11) of a main Mach-Zehnder waveguide (MZC) (8) to switch the USB signal and the LSB signal, and so FSK modulation can be made. In order to control the phase of the optical signal to be outputted from the main Mach-Zehnder waveguide (MZC) (8), bias voltage is applied to the main Mach-Zehnder electrode (11), and the phases of the USB signal and the LSB signal are controlled. By doing so, FSK modulation with adjusted phases can be performed.

Abstract: The invention relates to an optical transmission system comprising transmitter and receiver devices and comprising automatic optical signal level configuration means which provide the same fixed output signal level for a received signal level range, and the system comprising at least one automatic self-level unit in the transmitter device and at least one automatic self-level unit in the receiver device.

Abstract: An improved precompensation circuit includes a greatly improved differentiator in the dispersion precompensation path, a preprocessor in the dispersion precompensation path for reducing f2?f1 type Composite Second Order (CSO) distortion, and a broadband phase shifter for compensating undesired vector interaction between the laser predistortion and dispersion compensation.

Abstract: An optical modulator achieving high extinction ratio and an optical modulator system. By a control system performing an adjustment method comprising predetermined steps by applying a bias voltage daringly to a modulation electrode for switching the USB signal and LSB signal of an established optical SSB modulator or optical FSK modulator, a means for adjusting bias voltage applied to each bias electrode preferably automatically is provided and a bias point where the extinction ratio of an optical modulator is maximized can be obtained.

Abstract: A directly modulated optical transmitter for use with a fiber optical communications system operating in the 1550 nm wavelength band exhibits very low chirp. The chirp inherently present in a directly modulated laser is cancelled by a phase modulator which optically modulates the directly modulated laser light beam by applying a 180° phase delay to a split-off portion of the input radio frequency signal. This provides a low cost transmitter capable of operating in the 1550 nm band and with laser chirp effectively cancelled or substantially reduced, thereby avoiding distortions due to laser chirp interactions with the downstream optical fiber.

Abstract: Provided are an apparatus for and a method of generating millimeter waves, in which millimeter-wave generation and frequency up-conversion can be achieved at the same time using a single device. The apparatus includes a mode-locking laser diode (LD) which has a distributed feedback (DFB) sector and a gain sector and generates high-frequency optical pulses through a passive mode locking process, a modulator which modulates an external optical signal using an electric signal and injects the modulated optical signal to the mode-locking LD to lock the optical pulses, and a radio frequency (RF) locking signaling unit which injects the electric signal to the modulator.

Abstract: After implementing a scrambler upon an electric signal of digital signals to be transmitted to a user terminal, this electric signal is converted into a digital optical signal, and an analog optical signal and this digital optical signal are multiplexed by wavelength division multiplexing, thereby reducing influence of cross-talk interference that is exerted on the analog optical signal by the digital optical signal.

Abstract: An optical transmission apparatus according to the present invention comprises: a plurality of optical modulating sections serially connected to each other via optical fibers; driving sections corresponding to the optical modulating sections; delay amount varying sections that provide variable delay amounts for modulating signals to be input to the driving sections, to adjust timing between drive signals to be provided for the optical modulating sections; temperature monitoring sections that monitor the temperature of each of the optical fibers and the like; and a delay amount control section that controls the delay amount in each of the delay amount varying sections based on the monitored temperatures.

Abstract: The present invention utilizes field programmable gate arrays (FPGAs) to implement a parallel differential quadrature phase shift keying (DQPSK) precoder and a DQPSK optical transmitter with an automatic realignment process. The present invention can perform DQPSK preceding, modulation, and data stream realignment at any lower rate, and its upper rate is determined by capability in speed and logic resources and external connections of available integrated circuit technology.

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: The present invention provides a software-based electro-optic modulator bias control system resident in an optical transceiver including an electro-optic modulator that includes an optical-to-electrical converter including a transimpedance amplifier, an analog-to-digital converter, and a software algorithm, wherein the software algorithm is operable for determining an optimum bias voltage applied to the electro-optic modulator by discovering a maximum average optical power transmitted by the electro-optic modulator, or quadrature point, wherein the quadrature point is discovered by determining at what bias voltage the slope of an average optical power transmitted by the electro-optic modulator, defined as an optical power change given an incremental bias voltage change, is equal to zero.

Abstract: An optical transmission device includes: a variable dispersion compensator to give chromatic dispersion and output an input light, a branching unit to branch the light output from the variable dispersion compensator to a first part and a second part, a reproduction unit to reproduce an electric signal from the first part of the input light, a monitor unit to perform reproducing processing on the electric signal from the second part of the input light, control the variable dispersion compensator based on a result of the reproducing processing, and has a sensitivity to a variation of the chromatic dispersion which is higher than the sensitivity to the variation of the chromatic dispersion of the reproduction unit.

Abstract: A method and device for adequately controlling the DC bias of each of the optical modulating sections of an optical modulator even while the optical modulator is operating in normal mode and even with a simple structure.

Abstract: A light emitting element driving differential switch (2) includes first and second transistors (M1, M2). A third transistor (M3) is connected as an auxiliary switch in parallel to the first transistor (M1) whose drain is connected to a light emitting element (1). A third switch driving signal (IN3) is input to the third transistor (M3) to turn ON the third transistor (M3) at a slightly earlier point in time than when complementary switch driving signals (IN1, IN2) are input to the first and second transistors (M1, M2) to drive the first and second transistors (M1, M2). This improves the rising characteristics of the output from the light emitting element having a high power level.

Abstract: In an optical communications device that generates picture optical signals and optical signals for data communication by wavelength division multiplexing, it is carried out to alter a signal pattern inserted between packet signals of the optical signals for data communication so that a frequency component of a modulation waveform of the signal pattern disperses. The signal pattern is generated by inputting outputs of a counter for counting up a sign bit into a coder adopting a designated coding method.

Abstract: A time-multiplexed waveform generator includes a wavelength splitter that receives an input optical signal and spectrally separates the input optical signal into a plurality of frequency components. A plurality of intensity modulators receives each of the frequency components and passes each of the frequency components for a selective time period, and then extinguishes that frequency for the remainder of a chirp time, the plurality of intensity modulators producing a plurality of first output signals. A plurality of adjustable delay lines is positioned after the intensity modulators and receives the first output signals. Each of the adjustable delay lines enables phase control of each of the frequency components associated with the first output signals for compensating any relative drifts of the path lengths and phase coherently stitching a plurality of sub-chirps together. The adjustable delay lines produce a plurality of second output signals.

Abstract: Alerts, such as laser driver current alarms, are triggered in an optoelectronic device based on dynamic digital diagnostics, such as operating temperature. Optoelectronic devices may execute microcode structured to represent a formulaic relation between a first parameter (e.g., temperature) and an indicator value for a second parameter (e.g., laser driver current). The microcode may further be structured to cause the optoelectronic device to access the first parameter, calculate an indicator value for the second parameter based on the accessed first parameter using the formulaic relation, access the second parameter, and compare the indicator value with the second parameter to determine whether to trigger an alert. If the second parameter exceeds the indicator value, the alert may be triggered, and may be indicative of potentially imminent optoelectronic device failure.

Abstract: An optical transmitter for generating a modulated optical signal for transmission over a fiber optic link to a remote receiver including a laser; an input coupled to the laser for directly amplitude modulating the laser with an RF signal to produce an optical signal including an amplitude modulated information-containing component; and a phase modulator coupled to the output of the laser for reducing or canceling the noise signals generated in the laser.

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.