Methods and systems for encoding multi-level pulse amplitude modulated signals using integrated optoelectronics are disclosed and may include generating a multi-level, amplitude-modulated optical signal utilizing an optical modulator driven by first and second electrical input signals, where the optical modulator may configure levels in the multi-level amplitude modulated optical signal, drivers are coupled to the optical modulator; and the first and second electrical input signals may be synchronized before being communicated to the drivers. The optical modulator may include optical modulator elements coupled in series and configured into groups. The number of optical modular elements and groups may configure the number of levels in the multi-level amplitude modulated optical signal. Unit drivers may be coupled to each of the groups. The electrical input signals may be synchronized before communicating them to the unit drivers utilizing flip-flops. Phase addition may be synchronized utilizing one or more electrical delay lines.

An coherent transceiver includes a single silicon photonics substrate configured to integrate a laser diode chip flip-mounted and coupled with a wavelength tuning section to provide a laser output with tuned wavelengths which is split in X:Y ratio partly into a coherent receiver block as local-oscillator signals and partly into a coherent transmitter block as a light source. The coherent receiver includes a polarization-beam-splitter-rotator to split a coherent input signal to a TE-mode signal and a TM*-mode signal respectively detected by two 90-deg hybrid receivers and a flip-mounted TIA chip assisted by two local-oscillator signals from the tunable laser device. The coherent transmitter includes a driver chip flip-mounted on the silicon photonics substrate to drive a pair of Mach-Zehnder modulators with 90-degree shift in quadrature-phase branches to modulate the laser output to two polarized signals with I/Q modulation and uses a polarization-beam-rotator-combiner to combine them as a coherent output signal.

Provided is an optical transceiver including a reference tunable laser module configured to generate and output light of a reference wavelength; a first general tunable laser module configured to generate and output light of a first wavelength; and a controller configured to control a tuning operation of the first wavelength of the first general tunable laser module, based on information about a relationship between the reference wavelength and the first wavelength.

An optical modulator includes: an encoder that encodes an input data signal; a branch circuit that branches an optical signal into first and second optical signals; a first arm through which the first optical signal branched at the branch circuit passes; a first phase shifter group on the first upper arm that adjusts a phase shift amount of the first optical signal that passes through the first arm; a second arm through which the second optical signal branched at the branch circuit passes; a second phase shifter group on the second arm that adjusts a phase shift amount of the second optical signal that passes through the second arm such that a sign of the phase shift amount of the second optical signal becomes opposite to a sign of the phase shift amount of the first optical signal; and a multiplexing circuit that multiplexes the first optical signal.

A method of controlling an optical modulator having a first child modulator, a second child modulator, and a parent modulator includes applying a first bias, on which a first dither signal with frequency f1 is superimposed, to the first child modulator, applying a second bias, on which a second dither signal with frequency f2 different from f1 is superimposed, to the second child modulator, applying a third bias, on which a third dither signal with frequency f3 different from both f1 and f2 is superimposed, to the parent modulator. A first error component having the f1 frequency, and a second error component having a beat frequency of f2 and f3 frequencies are detected from the output light from the optical modulator, and a first error signal is generated from the first error component and the second error component to adjust the first bias.

Disclosed herein is a dual parallel Mach-Zehnder-modulator (DPMZM) device comprising a DPMZM 10 having first and second inner MZMs arranged parallel to each other. The first inner MZM generates an in-phase component E.sub.I of an optical signal in response to a first driving voltage V.sub.I, and the second inner MZM generates a quadrature component E.sub.Q of said optical signal in response to a second driving voltage V.sub.Q. Further disclosed is a calculation unit 52 configured for receiving an in-phase component y.sub.I and a quadrature component y.sub.Q of a desired base-band signal, and for calculating pre-distorted first and second driving voltages V.sub.I, V.sub.Q. The calculation of the pre-distorted first and second driving voltages V.sub.I, V.sub.Q is based on a model of said DPMZM 10 accounting for I-Q cross-talk, and using an algorithm that determines said first and second driving voltages V.sub.I, V.sub.Q each as a function of both of said in-phase and quadrature components y.sub.I, y.sub.Q of said base-band signal.

An optoelectronic device for quadrature-amplitude modulation (QAM) and a method of modulating light according to the same. The device comprising: an input waveguide; two intermediate waveguides, each coupled to the input waveguide via an input coupler; and an output waveguide, coupled to each of the intermediate waveguides via an output coupler; wherein each intermediate waveguide includes a modulating component connected in series with a phase shifting component, and each modulating component is connected to a respective electronic driver, the electronic drivers together being operable to produce a QAM-N modulated output from light entering the device from the input waveguide.

An optical transmitter includes quadrature modulators and light receiving elements to which inverted output light of output light from the quadrature modulators is input, the quadrature modulators including parent Mach-Zehnder modulators in respective paths of a first pair of paths into which carrier light from a light source is split, the parent Mach-Zehnder modulators including child Mach-Zehnder modulators including first phase modulation units, and second phase modulation units. When blocking a transmission optical signal, the voltage amplitude of a transmission electrical signal to be applied to the quadrature modulator is adjusted such that it is smaller than a half-wave voltage, at most two dither signals are applied to the first phase modulation units, a component output by the light receiving element, the component having n times a frequency of the dither signals, is detected, and bias voltages to be applied to the first phase modulation units are controlled such that the component having n times the frequency is minimized.

An optical transmission system includes an optical transmitter and an optical receiver. The optical transmitter includes a low speed signal generation unit configured to generate, based on an input signal of a transmission data sequence and a signal obtained by cyclically shifting a spectrum of the input signal, a plurality of low speed signals, a high speed signal generation unit configured to digital-to-analog convert and synthesize the plurality of low speed signals to generate a high speed signal, and an optical modulation unit configured to transmit an optical signal obtained by modulation of the high speed signal to a transmission path. The optical receiver includes a reception unit configured to receive the optical signal from the transmission path and output the high speed signal obtained from the optical signal that is received, an optical-receiver-side high speed signal compensation unit configured to compensate, based on the high speed signal output by the reception unit and a signal obtained by cyclically shifting a spectrum of the high speed signal, for the high speed signal, and a reception data decoding unit configured to decode the high speed signal compensated by the optical-receiver-side high speed signal compensation unit to restore binary information included in the optical signal transmitted by the optical transmitter.

A Mach Zehnder modulator operates by phase modulating split optical beams with a modulating signal to create dissimilarities in the optical characteristics between the split beams. When the beams are recombined, the dissimilarities gives rise to intensity modulations that are indicative of the modulating signal. One or both beams are modulated with an RF trimming signal. The trimming signal is applied asymmetrically across the two beams thereby reducing the intensity of the optical carrier frequency in one of the beams more than in the other. By selecting the size of the trimming signal the differences in the optical amplitude of the carrier frequency in the two beams can be nulled.