Abstract: According to a first aspect, techniques are provided to optimize a Mach-Zehnder modulator drive waveform by distorting the outer modulation levels of the waveform, thereby equalizing eye openings of the received optical field, and in particular creating a wider and more defined central eye opening of the received optical field. According to a second aspect, techniques are provided to adjust in-phase (I) modulation levels based on the imperfect performance of a Mach-Zehnder modulator allocated to modulate quadrature-phase (Q) modulation levels, and conversely to adjust the Q modulation levels based on the imperfect performance of an MZ modulator allocated to modulate I modulation levels.

Abstract: A polarization-multiplexed signal receiver includes a polarization adjustment unit to adjust a polarization state of inputted polarization-multiplexed signal, which is carrying signal data on each of two polarized waves being inputted, based on a control signal and to output the adjusted polarization-multiplexed signal, an optical signal reception unit to convert the polarization-multiplexed signal having the adjusted polarization state into an analog electric signal and output the analog electric signal, an A/D conversion unit to convert the analog electric signal into a digital electric signal and output the digital electric signal, a digital signal processing unit to perform digital coherent processing to the digital electric signal and take out the signal data and a feedback control unit to generate the control signal based on quality of the signal data and output the signal data to the polarization adjustment unit.

Abstract: To stabilize power to an optical multimode receiver a multimode variable optical attenuator is connected to the receiver with the attenuator's voltage being controlled using a feedback signal provided by an output detector, the signal being processed using a control algorithm based on proportional-integrate-differential theory.

Abstract: An optical modulation device includes a generating circuit that generates a low-frequency signal, an average value of amplitude as an alternating-current component of the low-frequency signal being different from a center value of the amplitude of the low-frequency signal, a superimposing unit that superimposes the low-frequency signal on a data signal, an optical modulator that modulates, using the superimposition of the low-frequency signal by the superimposing unit, light from a light source and outputs a light signal, a calculating circuit that calculates an amplitude average value and an amplitude center value of a low-frequency component obtained from the light signal output by the optical modulator, and a controller that controls a bias voltage of the optical modulator such that the amplitude average value is brought closer to the amplitude center value of the frequency component calculated by the calculating circuit.

Abstract: A circuit, optical transceiver and/or methods for using the same may be useful for determining average power, extinction ratio, and/or modulation amplitude when monitoring an optical transceiver and/or optical network. The circuit generally comprises a photodiode configured to generate a first current responsive to an optical signal, a current mirror coupled to a first terminal of the photodiode, and a detector coupled to a second terminal of the photodiode. The current mirror is configured to produce a second current equal to or proportional to the first current, and the detector is configured to determine a power or amplitude of the optical signal. Further, the present scheme may communicate information using a low speed signal superimposed on or combined with the relatively high speed optical signal.

Abstract: Systems and methods for determining the envelope of a modulated signal using high bandwidth and low bandwidth samples of a hybrid signal. The hybrid signal is obtained by mixing the modulated signal with its carrier signal. The systems and methods of the present disclosure may be suitable for equivalent-time or real-time oscilloscopes.

Abstract: Analog transport of a wideband RF signal is effectively and efficiently provided using a coherent, narrowband optical carrier. The wideband RF signal is phase modulated onto the carrier at a first location. Non-coherent discrimination is applied to the modulated carrier at a second, different location to generate an amplitude modulated optical signal where the amplitude modulation represents the original wideband RF signal. A photo-detector is then used to regenerate a representation of the original wideband RF signal. The method and apparatus of the invention can be applied in systems dedicated to the analog RF transport or in wavelength division multiplexed systems which also provide transport for other analog or digital data.

Abstract: A module for routing packets of first and second optical signals comprising first and second inputs (A,B) for receiving the first and second optical signals and first and second outputs (C,D) for the optical signals. The module comprises optical switching means (8) for switching the first optical signal and the second optical signal to either one of the two outputs (C,D), and a correlator module (7). The correlator module comprises at least two optical correlators (9,10,11,12). The correlator module (7) is arranged to generate control signals for controlling the switching means (8) based on destination data in packets of the first and second signals such that if packets of the first and second optical signals overlap, the switching means directs the packet that was received first to the output (C,D) indicated by the destination data of that packet and the overlapping subsequent packet is directed to the other output (C,D) or blocked.

Abstract: An optical transmitter is disclosed. An optical modulator outputs an optical signal by modulating light being input, and has an optical absorption characteristic which changes a degree of optical absorption depending on a bias voltage being applied and includes a first characteristic region and a second characteristic region in which the degree of the optical absorption is greater than the first characteristic region. An power source applies an electric field generated by applying a predetermined shutdown bias voltage corresponding to the second characteristic region to electrodes provided in two interference optical guides formed in the optical modulator, when an output of the optical signal from the optical modulator is shut down to be less than or equal to a desired amount.

Abstract: An apparatus comprising a frequency-domain equalizer that has been iteratively generated to compensate for filtering effects of a wavelength selective switch, wherein the FDEQ is configured to process in a frequency domain digital samples of a polarization multiplexed phase-shift-keying signal that has been transported over an optical channel.

Abstract: Methods and systems are provided for extending the range that a laser can transmit data, particularly in environments with high attenuation or turbidity. Particularly, an energy storing laser that is capable of continuously converting electrical energy to optical energy and storing the optical energy or the electrical energy in the energy storing laser until the energy storing laser is instructed to transmit a laser transmission. In some embodiments, the energy storing laser uses a pulse train with a low duty cycle to increase the peak power of each laser pulse. Also, a pointing and tracking system is used to provide a communication link between stationary platforms or moving vehicles.

Abstract: A laser mux assembly generally includes a back reflector selectively coupled to one of the input ports of an optical multiplexer, such as an arrayed waveguide grating (AWG), and at least one laser emitter coupled to an output port. The laser emitter may include a gain region that emits light across a plurality of wavelengths including, for example, channel wavelengths in an optical communication system. The emitted light is coupled into the output port and the AWG or optical multiplexer filters the emitted light from the laser emitter at different channel wavelengths. The back reflector reflects the filtered light at the respective channel wavelength such that lasing occurs at the channel wavelength(s) of the reflected, filtered light. The laser mux assembly may be used, for example, in a tunable transmitter, to generate an optical signal at a selected channel wavelength.

Abstract: The present invention discloses a service protection method and device based on an automatic switched optical network (ASON), which are adapted to restoring a service when a fault occurs in the connection of the service. The method comprises: comparing a dynamic restoration lag time of the service with a protection switching lag time of the service; and starting a protection switching process to restore the service if the dynamic restoration lag time is greater than the protection switching lag time; and starting a dynamic re-routing process to restore the service if the protection switching lag time is greater than the dynamic restoration lag time. By the present invention, the reliability of the network is enhanced and the self-healing capacity of the ASON is improved.

Abstract: In one embodiment, a method for performing nonlinearity compensation on a dispersion-managed optical signal that was transmitted over an optical communication link, the method including virtually dividing the communication link into a plurality of steps, performing lumped dispersion compensation on a received optical signal to obtain a waveform upon which digital backward propagation (DBP) can be performed, performing DBP by performing dispersion compensation and nonlinearity compensation for each step, and generating an estimate of the transmitted signal based upon the performed DBP.

Abstract: Feed-forward and feedback strategies are used to control local oscillator power and transimpedance amplifier gain in a high-speed coherent optical receiver.

Abstract: An optical source uses feedback to maintain a substantially fixed spacing between adjacent wavelengths in a set of wavelengths in a wavelength comb output by the optical source. In particular, a set of light sources in the optical source provide optical signals having the set of wavelengths. Moreover, the optical signals are output at diffraction angles of an optical device in the optical source (such as an echelle grating), and optical detectors in the optical source determine optical metrics associated with the optical signals. Furthermore, control logic in the optical source provides control signals to the set of light sources based on the determined optical metrics.

Abstract: An optical packet switching system includes optical packet switching apparatus and an optical packet transmitting apparatus. The optical packet switching apparatus includes client optical delay units for delaying optical packet signals, network optical delay units for delaying one of the network optical packet signals, the network optical delay unit having a longer delay time than the client optical delay unit, an optical switch unit for switching the route of the inputted client optical packet signal so as to be sent out, an optical switch control unit for controlling the optical switch unit. The optical switch control unit is configured in such a manner as to detect a free time slot. The optical packet transmitting apparatus adjusts transmit timing, with which the client optical packet signal is sent out, in such a manner that the client optical packet signal is inserted into the free time slot.

Abstract: The present invention discloses a method and system for accurate time transfer in PON. An Optical Line Terminal (OLT) ranges Optical Network Units (ONUs) and obtains ranging information, then, triggered by the periodic Pulse per n Second (PPnS), generates a PPnS timestamp based on the local reference counter and the Time of Day (TOD) above second; OLT transmits the ranging information, the periodic PPnS timestamp and TOD to ONUs; ONUs predicts the time of the next second according to said periodic PPnS timestamp, TOD and ranging information, and outputs the corresponding PPnS. The invention is characterized by the combination of the features of PON point to multi-point and PON ranging into its time transfer method, the high accuracy of time transfer, and the low hardware costs for OLT and ONU, as well as the extremely small bandwidth occupancy.

Abstract: Methods and apparatus for optical analog to digital conversion are disclosed. An optical signal is converted by mapping the optical analog signal onto a wavelength modulated optical beam, passing the mapped beam through interferometers to generate analog bit representation signals, and converting the analog bit representation signals into an optical digital signal. A photodiode receives an optical analog signal, a wavelength modulated laser coupled to the photodiode maps the optical analog signal to a wavelength modulated optical beam, interferometers produce an analog bit representation signal from the mapped wavelength modulated optical beam, and sample and threshold circuits corresponding to the interferometers produce a digital bit signal from the analog bit representation signal.

Abstract: The present invention discloses a Wavelength Division Multiplexing Filter which can satisfy coexistence requirements of different PON systems and an optical line detecting system.