Abstract: An optical receiver includes: a converting unit that converts an optical signal into an electrical signal; an amplifying unit that amplifies the electrical signal; a regenerating unit that regenerates the amplified electrical signal; a correcting unit that performs correction of an error included in the regenerated electrical signal; a monitoring unit that performs monitoring of an optical current flowing through the converting unit; and a control unit that calculates a decision threshold based on a result of the correction and a result of the monitoring.

Abstract: A transimpedance amplifier (TIA) circuit usable for burst mode communications is provided. The TIA circuit includes a TIA stage, a limiter-amplifier, and a DC restoration loop. The invention overcomes problems of the prior art relating to burst communications, such as a DC level in the output signal which can change from burst to burst and a duty-cycle distortion in large signals. This is achieved by using a DC restoration loop that ensures achieving zero DC potential within variable acquisition periods.

Abstract: A method for receiving an optical signal is included where an ingress signal is split into a first portion and a second portion. A relative delay is induced between the first portion and the second portion, which are optically interfered to generate at least one interfered signal. Quality criteria of a monitored signal at least based on the at least one interfered signal is monitored so that a relative delay based in the quality criteria may be adjusted.

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: An optical transmission network includes an optical transmitter photonic integrated circuit (TxPIC) chip, utilized in an optical transmitter and has a plurality of monolithic modulated sources integrated for multiple signal channels on the same semiconductor chip is provided with channel equalization at the optical receiver side of the network that permits one or more such integrated modulated sources in the TxPIC chip to be out of specification thereby increasing the chip yield and reducing manufacturing costs in the deployment of such TxPIC chips. FEC error counts at the FEC decoder on the optical receiver side of the network includes counters that accumulate a plurality of bit pattern-dependent error counts based on different N-bit patterns in the received data bit stream. The accumulated counts of different N-bit patterns are utilized to provide for corrections to threshold and phase relative to the bit eye pattern as well as provided for weight coefficients for the optical receiver equalization system.

Abstract: An electronic dispersion compensation (EDC) arrangement for a multi-channel optical receive utilizes a time division technique to “share” a common adaptive algorithm block between a plurality of N separate channels. The algorithm block embodies a specific algorithm associated with correcting/updating tap weights for the delay lines forming the equalizing elements, and a time slot assignment element is used in conjunction with the algorithm block to control the access of the various channels to the algorithm block. In situations where certain channels experience a greater degree of dispersion than others, the time slot assignment element may be configured to allot a greater number of time slots to the affected channels.

Abstract: An optical line termination comprises a DC current load, power measurement circuitry, upstream data path circuitry and current mirror circuitry. The current mirror circuitry is connected between the DC current load, the power measurement circuitry and the upstream data path circuitry. The DC current load is connected in parallel with a photodiode of the upstream data path circuitry. The DC current load exhibits a substantially fixed load. The current mirror provides a copy of an aggregate current to the power measurement circuitry. The aggregate current is a summation of a current draw by the DC current load and a current draw by the photodiode. The power measurement circuitry is configured for outputting a power level dependent upon the aggregate current. Accordingly, the optical line termination provides for a non-intrusive solution for measuring optical input power and, thereby, enables the measured optical power to be monitored.

Abstract: A method is disclosed for monitoring and controlling the bit error rate (BER) in an optical communication network where an optical receiver in the optical transmission network. The method includes the steps of decombining a combined channel signal received from the network and then monitoring a real time bit error rate (BER) of a decombined channel signal. The determined BER is then communicated, such as through an optical service channel (OSC) to an optical transmitter source that is the source of origin of the channel signal. Based upon the determined BER, the chirp of a channel signal modulator at the optical transmitter source that generated the monitored channel signal is adjusted by, for example, adjusting its bias. The same channel signal received at the optical receiver can be monitored again to determine if an acceptable level for the BER has been achieved by the previous chirp adjustment.

Abstract: Provided is a burst mode optical receiver capable of accurately detecting an optical signal of minimum amplitude, by automatically controlling a gain of a pre-amplifier according to an amplitude of an input optical signal. The burst mode optical receiver can automatically control a gain of a pre-amplifier according to the amplitude of an input optical signal using an output signal of a first peak detector. In other words, when the input optical signal has a small amplitude that meets the receiving sensitivity of the burst mode optical receiver, the gain of the pre-amplifier automatically increases, thereby improving the receiving sensitivity of the burst mode optical receiver.

Abstract: The aim of the invention, which concerns a method and a system for converting an optical received pulse train into an electrical output pulse train, is to create a method and an associated circuit arrangement for converting an optical received pulse train into an electrical output pulse train whereby achieving an improvement in transmission quality and a reduction in latency time.

Abstract: A burst optical receiver includes an optical signal inlet, an optical-electrical signal converter, an AC coupling network, an integrator feedback network, and an electrical signal outlet. The AC coupling network is electrically communicated with the optical-electrical signal converter, and blocks the electric signal having the frequency ranges lower than a predetermined threshold frequency, and allows the electric signal having the frequency ranges above the threshold frequency to pass through. The integrator feedback network is electrically communicated with the AC coupling network, and recurrently modifies the electric signal from the AC coupling network in such a manner to minimize noise mixed with the electric signal such that the electric signal is sufficiently contrasted with the noise for maximizing a signal-to-noise ratio of the electric signal.

Abstract: According to embodiments of the present invention, an optical transponder and/or optical transceiver includes a decision circuit, which scales a decision threshold voltage based on power in a received optical signal. In one embodiment, the decision set point may be established based on an expected amplitude or power of an incoming optical signal and the transponder and/or transceiver uses the actual power of the incoming optical signal to adjust the decision threshold voltage.

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: A communication system having a transmitter transmits an information signal over a communication media and a receiver coupled to the communication media receives the transmitted information signal. The receiver includes a continuous time filter having an adjustable bandwidth for linearly equalizing the transmitted information signal as a function of the adjustable bandwidth. A decision feedback equalizer coupled to the continuous time filter then reduces inter-symbol interference in the filtered information signal.

Abstract: Methods and systems for split voltage domain receiver circuits are disclosed and may include amplifying complementary received signals in a plurality of partial voltage domains. The signals may be combined into a single differential signal in a single voltage domain. Each of the partial voltage domains may be offset by a DC voltage from the other partial voltage domains. The sum of the partial domains may be equal to a supply voltage of the integrated circuit. The complementary signals may be received from a photodiode. The amplified received signals may be amplified via stacked common source amplifiers, common emitter amplifiers, or stacked inverters. The amplified received signals may be DC coupled prior to combining. The complementary received signals may be amplified and combined via cascode amplifiers. The voltage domains may be stacked, and may be controlled via feedback loops. The photodetector may be integrated in the integrated circuit.

Abstract: The present invention provides a frequency offset monitoring device and an optical coherent receiver. A low speed frequency offset monitoring device comprises a signal speed lowering section, for lowering the speed of an inputted signal and outputting the speed lowered signal, and a frequency offset monitor, for monitoring frequency offset of the speed lowered signal outputted by the signal speed lowering section.

Abstract: The data transmission apparatus for performing data communication based on optical transmission includes a transmitting unit for converting and sending electric communication data, which is to be transmitted, into optical communication data, and a photoelectric conversion circuit for receiving the optical communication data and converting the received optical communication data into electric communication data, wherein the photoelectric conversion circuit includes a photodiode for generating a current based on the optical communication data, and a variable current supply for subtracting a predetermined current from the current generated by the photodiode. In addition, a bias current of a laser diode of each transmitting unit is set to a current larger than a laser oscillation threshold current so as to reduce the deviation of a light emission delay time of each laser diode.

Abstract: An optical receiver is capable of minimizing fluctuations in the pulse width of an electrical signal rendered by converting an optical signal of broad-range illumination. The optical receiver includes a light-receiving element that receives an optical signal and converts the optical signal into a current; a bypass element through which a portion of the current of the light-receiving element flows; an impedance element that detects the remaining portion of the current of the light-receiving element and converts the remaining portion into a voltage signal; a voltage separation element interposed between the impedance element and the light-receiving element that separates the voltages on both sides thereof; and an automatic gain control (AGC) circuit to which the voltage signal from the impedance element is inputted and that controls the current flowing to the bypass element in accordance with the voltage signal.

Abstract: An apparatus and method for use in an adaptive optical equalizer including, in one embodiment an optical equalizer having an input and output coupled to receive an incoming optical signal and configured to generate an output optical signal by phase modulation and/or amplitude modulation of the receive optical signal in response to electronic control signals. A photodiode is configured to receive the output optical signal and generate an representative current signal. A control signal generator is configured to generate the electronic control signals in accordance with predetermined criteria and in response to the representative current signal from the photodiode. An interferometer is connected to receive the incoming and output optical signal from the optical equalizer, the differential amplifier is configured to receive electronic versions of outputs from the interferometer for generating a difference signal and supplying the difference signal to the control signal generator.

Abstract: An optical receiver circuit is disclosed. This receiver included in receiver optical sub-assembly (ROSA) adjusts bandwidth based on a voltage level detection at a receiver signal strength indication (RSSI) pin, or rate-adaptively adjusts the bandwidth of optical receiver circuit based on operation data rate.

Abstract: A receiver (10) for an optical signal containing a time jitter and a time-varying distortion caused by a periodic polarization scrambled signal comprises at least one decision gate (11) and a clock recovery module (13) providing a clock signal (C) recovered from the optical signal to the at least one decision gate (11). The receiver (10) further comprises a scrambling frequency generator (16) synchronized to the scrambling frequency and phase of the polarization scrambled signal, a jitter function generator (17) generating a clock phase control signal (??b) reproducing the time jitter, and at least one clock phase modulator (14) modulating the phase of the clock signal (C) according to the clock phase control signal (??b).

Abstract: The present invention includes apparatus and method of a variable step size dithering control algorithm for polarization mode dispersion controllers (PMDCs). The dithering step size of the PCs is adjusted according to the feedback signal including degree of polarization (DOP).

Abstract: The present invention provides an optical transceiver that enables to reduce the crosstalk from the optical transmitter to the optical receiver. The regenerator of the optical transceiver includes two main amplifiers, a selector, a selector control, and a re-shaper for shaping the receiving signal selected by the selector. The first main amplifier provides a first amplifier and a delay circuit connected in upstream to the first amplifier. The second main amplifier provides a second amplifier and a delay circuit connected in downstream to the second amplifier. The selector selects, based on the phase difference between the receiving signal Rx and the transmitting signal Tx, the output from the first main amplifier or that from the second main amplifier.

Abstract: A receiver for an OTDM/PDM pulse train (10) in which the pulses (12) have alternating polarizations (P1, P2) has a polarization insensitive optical switch (16; 161, 162, 163, 164) for isolating optical pulses (10?) within the pulse train (10), and a polarization selective element (17) for separating from the isolated pulses (10?) at least one component that has a single polarization. This allows to considerable relax the constraints posed on the switch since components in the isolated pulses that result from interchannel interference can, at least to a large extent, be eliminated by the subsequent polarization selective element (17).

Abstract: An optical receiver is disclosed that exhibits an improved phase margin and substantially constant output in response to changes in operating conditions (e.g., temperature, process, etc.). In accordance with the illustrative embodiment, a common-mode feedback comparison is performed prior to conversion of the signal from single-ended to differential voltage. When the common-mode feedback comparison is performed in this way, there are fewer amplifiers in the signal path and the phase margin of the common-mode feedback loop is increased. In addition, as the common-mode feedback is performed at the first stage of the transimpedance amplifier, the gain response of the transimpedance amplifier remains substantially constant in response to changes in temperature, input current range, and for different integrated circuit fabrication processes.

Abstract: An optical receiving apparatus sets, efficiently and optimally, a delay interferometer and a variable wavelength dispersion compensator in the apparatus.

Abstract: In an over-sampled maximum-likelihood sequence estimation (MLSE) receiver system, the optimal sample spacing is determined for a variety of conditions. In an illustrative implementation, the system includes an optical filter for tightly filtering an incoming optical data signal with an on-off-keying (OOK) non-return-to-zero (NRZ) format, followed by an optical-to-electrical converter, an electrical filter, a sampler, and a MLSE receiver. The sampler samples the filtered electrical data signal twice each bit period with unequal sample spacings. For wide optical filtering bandwidths, the optimal sample spacing occurs at less than 50% of a bit period. For narrow bandwidths, the optimal sample instances occur closer to the maximum eye opening.

Abstract: A relation between a light input power monitor value of an optical transmission signal before passing through a fiber and an input signal amplitude monitor value is recorded in advance in a storage device. Next, actual optical-transmission-waveform is inputted into an optical receiver module, and then comparisons between a light input power monitor value and an input signal amplitude monitor value, and respective monitor values in the case without having the waveform distortion as described above are performed in an operation device to calculate a waveform distortion value. According to the waveform distortion level calculated herein, an optimum threshold value and an optimum phase adjusting value, at which receiver sensitivity is maximized, are calculated in the operation device to control a threshold-value adjusting circuit and a phase-value adjusting circuit, thereby a threshold value and a phase value that are optimum for an input distortion level can be established.

Abstract: The present invention provides an optical receiver applicable to various transmission rates. The optical receiver of the invention includes a main amplifier and a switching unit. The main amplifier amplifies a voltage signal output from the preamplifier, which converts the photocurrent to the voltage signal. The switching unit is inserted between the preamplifier and the main amplifier to vary the input impedance RIN of the main amplifier depending on the transmission rate.

Abstract: A system and method for superheterodyne detection in accordance with the invention. The system comprises a first conversion unit for performing a first heterodyne operation on an optical input signal to generate an electrical IF signal. A second conversion unit is electrically or optically coupled to the first conversion unit. The second conversion unit performs a second heterodyne operation to generate an electrical output signal suitable for signal processing.

Abstract: Methods and systems for PMD compensation in an optical communication system are implemented by transmitting multiple optical signals through a common optical conduit to an optical compensator that adjustably rotates the polarization states of the multiple optical signals and transmits the rotated optical signals to an optical receiver. The receiver, upon sensing an excessive error condition, commands the optical compensator to change the polarization state of rotation, which changes the PMD profile of the received optical signals.

Abstract: In an optical communication-use receiving circuit of the present invention, the pulse width of the received pulse which is a binary signal corresponding to the signal optical pulse is specified by using an integration circuit and a trigger generating circuit. If the pulse width of the received pulse is not shorter than a predetermined value, a signal having a fixed pulse width is outputted as an output signal from a one-shot pulse generating circuit, so that a pulse having a constant pulse width corresponding to the specified communication speed is outputted. Accordingly, if the pulse width deriving from the signal optical pulse is larger than a certain value, the communication is deemed as a low-speed communication, and a pulse having a constant pulse width corresponding to the communication speed is outputted. As a result, it is possible to realize a small-size receiving circuit and a small-size electronic device which require no external switching-over terminal.

Abstract: A transmitting and receiving device, in which the received signal which is produced by the receiving device has only a small amount of crosstalk. This object is achieved by providing a transmitting and receiving device having a transmitting device for producing a transmission signal, a receiving device for producing a received signal, and a compensation device which is connected to the transmitting device and to the receiving device and which at least reduces any crosstalk which is produced by the transmitting device in the receiving device.

Abstract: An optical access network system having a function of correcting upstream signal waveform distortions occurring in the PON section, wherein a central office side apparatus comprises a main controller to notify each subscriber connection apparatus of a transmission grant period, an equalizer of a tap gain adaptive control type to correct waveform distortions of signals received from the subscriber connection apparatuses, an equalizer controller, and a parameter table for storing, for each subscriber connection apparatus, the initial values of tap gains to be set for the equalizer. The main controller issues a switchover request for switching the equalization characteristic to the equalizer controller each time notifying a subscriber connection apparatus of a transmission grant period, and the equalizer controller retrieves the initial values of the tap gains for the subscriber connection apparatus from the parameter table in response to the switchover request, and sets these values to the equalizer.

Abstract: A dispersion compensating method for compensating wavelength dispersion occurring in an optical transmission line, includes the steps of: a) performing dispersion compensation by causing an optical signal, supplied from the transmission line, to pass through a variable dispersion compensator; and b) controlling a dispersion compensating amount in the variable dispersion compensator according to code error information corresponding to a type of code in a received data signal obtained from receiving the optical signal having undergone the dispersion compensation.

Abstract: A communication system includes an optical transmitter which is differentially driven and an optical receiver that outputs a differential signal. The optical transmitter creates the differential drive signal from an input signal and delivers the differential drive signal to a laser. The differential drive signal is generated with a transformer and RF chokes for floating the laser above ground. The signal detected by the receiver is input as a differential signal to a transformer which then passes the signal through amplifiers and a filter. The optical communication system provides an increased spurious-free dynamic range which is well suited for RF signals and other analog signals.

Abstract: A control device with a switchable bandwidth including: an integrating element with a first capacitance, which is charged and discharged by at least one current; at least one second capacitance, which can be connected in parallel with the first capacitance via a first switch; and at least one voltage follower, via which the voltage present at the first capacitance can be fed to the second capacitance. In this case, the first switch is open if the voltage present at the first capacitance is fed to the second capacitance by means of the voltage follower. The first switch is closed if the second capacitance is connected in parallel with the first capacitance. The invention enables a further capacitance to be supplementarily connected without a disturbance signal arising.

Abstract: Detecting a pulse of a signal includes receiving the signal and a light beam. The signal drives a spatial light modulator to modulate the light beam, where the complex amplitude of the modulated light beam is proportional to the signal current. The modulated light beam passes through an optical system and is detected by an optical detector array. A processor identifies a portion of the signal comprising the pulse.

Abstract: An optical receiver with a threshold voltage convergence and audio apparatus and communication apparatus using the optical receiver are provided. The optical receiver of the present invention includes an optical detector for converting a received optical signal to a current signal; a transimpedance amplifier for converting the current signal to a voltage signal; a level shifter for converging the voltage signal to a threshold voltage by removing an offset of the voltage signal, the level shifter comprising a plurality of linear subtractors connected in series; a reference voltage generator for generating a reference voltage in proportion to a variation of the offset of the voltage signal; and a comparator for comparing the threshold voltage and the reference voltage and generating a digital signal of a logic level according to a comparison result.

Abstract: A system and method for detecting digital symbols carried in a received optical signal. The system comprises a functional element operative to receive a stream of samples of an electrical signal derived from the received optical signal and to evaluate a non-linear function of each received sample, thereby to produce a stream of processed samples. The system also comprises a detector operative to render decisions about individual symbols present in the received optical signal on the basis of the stream of processed samples. In an embodiment, the non-linear function computes substantially the square root of each received sample.

Abstract: A system, method, and computer readable medium for measurement of burst mode optical power over multiple bursts, comprises mirroring a photodiode current of an optical signal burst, converting the mirrored photodiode current to a capacitor voltage, comparing the capacitor voltage to a pre-determined threshold voltage, and accumulating a burst time necessary for the capacitor voltage to reach the pre-determined threshold voltage.

Abstract: An optical receiver having compensation for signal level transients. The receiver includes an OE converter, a transient threshold compensator, a threshold combiner and a CDR system. The OE converter receives the incoming optical signal and provides a modulated electrical signal having a high speed response for tracking the modulation on the optical signal and an averaged electrical signal having a moderate speed response for tracking changes in the average level of the optical signal. The transient threshold compensator processes the averaged electrical signal for providing a transient feedforward adjustment. The threshold combiner combines the transient feedforward adjustment with a lower speed BER feedback threshold adjustment for providing a decision threshold signal. The CDR system uses the decision threshold signal for recovering a clock, providing the BER feedback threshold adjustment, and estimating the data carried by the modulation.

Abstract: An optical, multi-channel, Differential Phase Shift Keying (DPSK) receiver demodulates multiple Wavelength Division Multiplexed (WDM) channels using at least one interferometer. This distributes expense of the interferometer(s) over all channels of an optical signal, allowing for deployment of cost-effective, scalable, wideband, WDM DPSK systems. For example, for an 80 channel WDM link, the receiver uses a single interferometer instead of eighty interferometers and associated stabilization hardware, dramatically reducing size, weight, power, and cost. The receiver is architecturally compatible with existing interferometer technologies so previous development and qualification efforts can be leveraged. This allows for expedited technology insertion into existing optical communications networks, including terrestrial and space-based optical networks.

Abstract: In an adaptive optics module, wavefront sensing and data detection are implemented in a single device. For example, an optical-to-electrical converter converts a data-encoded optical beam to an intermediate electrical signal, which contains both the data encoded in the beam and also wavefront information about the beam. The data and wavefront information are later separated, for example by frequency filtering.

Abstract: An optical receiver circuit is constructed to be immune to interference from external interference signals. The optical receiver circuit includes a differential amplifier having an optical reception device connected to one input of the differential amplifier. The optical receiver circuit also includes an electrical element for simulating the electrical behavior of the reception device in the illumination-free state. The electrical element is connected to the other input of the differential amplifier.

Abstract: A transmission apparatus that receives an optical signal by selecting any one of a plurality of provided optical signal transmission paths through protection control is configured to include a plurality of optical signal outputting sections that output the optical signals transmitted through said optical signal transmission paths respectively as optical signals having wavelengths that are different from each other, a wavelength selective optical switch capable of selectively outputting light of a wavelength corresponding to any one of the optical signals coming from the optical signal outputting sections on the basis of the frequency of a controlling frequency signal, and an optical switch controlling section that supplies said controlling frequency signal to the wavelength selective optical switch so as to output the optical signal coming from the optical signal transmission path side that is selected by said protection control among the optical signals coming from the optical signal outputting sections.

Abstract: An optical receiver is disclosed comprising an erbium-doped fiber amplifier (EDFA) that is coupled to a photodiode and transimpedance amplifier without filtering output light signal in the EDFA. Optionally, a clock/data regenerator can be coupled to the electrical output of the transimpedance amplifier for compensating for noise distortion and timing jitter for affecting the control loop feeding back for adjusting the electrical current into a pump laser of an optical pre-amplifier. Furthermore, the optical receiver of the present invention can also be implemented in a transponder.

Abstract: A communications system includes an optical receiver for receiving optical signals and for converting the optical signals into electrical signals, a transimpedance amplifier (“TIA”) for filtering the electrical signals, a limiting amplifier coupled with the TIA, an automatic threshold control (“ATC”) coupled with the TIA for providing a reference voltage for the limiting amplifier. The ATC further includes a common emitter circuit and an emitter follower circuit, wherein logic high signals and logical low signals in the electrical signals are determined based on the reference voltage output from the ATC.

Abstract: A light receiver has a photoelectric conversion circuit which converts an input optical signal into an electrical signal, an electric amplifier which amplifies the electrical signal output from the photoelectric conversion circuit, a threshold adjustment circuit which outputs a threshold value according to signal information in the optical signal, and an optical signal loss detection circuit which compares amplitude of the electric signal output from the electric amplifier with the threshold value output from the threshold adjustment circuit and outputs results of the comparison.

Abstract: A direct attach optical receiver module and a system and method for testing the direct attach optical receiver module are provided. An optical receiver module may include an optical detector and an integrated circuit with an integrated amplifier circuit and at least one integrated capacitor. In one example, the optical detector may be physically attached to the integrated circuit and the output port of the optical detector may be electrically coupled to the input port of the integrated circuit. In another example, a redistribution layer that includes a tuning inductor may be being physically attached between the optical detector and the integrated circuit.