A superposition circuitry superposes a dither signal on a reference DC bias voltage and outputs a resultant voltage as a bias voltage to an MZ modulator, during control of a driving voltage amplitude. During the control of the driving voltage amplitude to the MZ modulator, an amplitude setter determines, by varying the amplitude of an output voltage from an amplifier, a plurality of amplitudes of output curves from a synchronous detector, each of which is obtained by varying the reference DC bias voltage output from a bias controller, and the amplitude setter sets the amplification factor of the amplifier, based on an amplitude of the output voltage from the amplifier that corresponds to an amplitude satisfying a predetermined condition, out of the plurality of the amplitudes of the output curves from the synchronous detector.

An optical transmitter includes an optical modulator including a first modulator, a second modulator, and a phase shifter that provides a predetermined optical phase difference between the first modulator and the second modulator, a light source that makes light enter the optical modulator, and a voltage controller that detects a distortion of light power characteristics from output light of the optical modulator in a state where no data signal is input to the optical modulator to determine a bias voltage to be set in the optical modulator while reducing the distortion.

A system for controlling an optical intensity and modulation of an optical data transmitter which includes current driver circuitry configured to provide a drive current to a laser diode wherein said current comprises a fixed component and a modulated component, said modulated component having a magnitude related to an input data stream. The monitor circuitry contains a photodiode and a first transimpedance amplifier coupled to said photodiode, said monitor circuitry configured to provide an output signal related to an optical intensity of said laser diode. The system further includes replica monitor circuitry containing a replica capacitor with a replica capacitance and a second transimpedance amplifier configured to be substantially identical in construction to said first transimpedance amplifier, said second transimpedance amplifier coupled to said replica capacitor. The system further includes replica capacitance control circuitry configured to control said replica capacitance of said replica capacitor to match a capacitance associated with said photodiode.

Systems and methods described herein include methods and systems for controlling bias voltage provided to an optical modulating device. The optical modulating device is biased at a bias point that is different from a null point of the device such that an offset to the received optical power due to limited extinction ratio is reduced.

An integrated high speed electro-optical control loop for very high-speed linearization and temperature compensation of an electro-absorption modulator (EAM) for analog optical data center interconnect applications is disclosed. The control loop can function in a stable manner because the electronics and optical components are monolithically integrated on a single substrate in small form factor. Because of the small size enabled by monolithic integration, the temperatures of the optical blocks and electronics blocks are tightly coupled, and the control loop time delays and phase delays are small enough to be stable, even for very high frequency operation. This arrangement enables a low cost, low power analog transmitter implementation for data center optical interconnect applications using advanced modulation schemes, such as PAM-4 and DP-QPSK.

An optical signal transmission apparatus generates a multi-level optical signal from a multi-level electric signal. The optical signal transmission apparatus detects, based on a supervisory signal generated from an optical signal, an electric-to-optical (E/O) conversion characteristic of an E/O converter configured to convert an electric signal into an optical signal. For example, when the E/O converter generates a multi-level optical signal from a multi-level electric signal based on a bias signal, the optical signal transmission apparatus determines a correspondence relationship between the bias signal and the optical signal. The optical signal transmission apparatus adjusts a use range of intensities of the bias signal based on the determined correspondence relationship so that the E/O converter may linearly operate.

An optical transmitter includes an electro-optic modulator, a monitor circuit that monitors output light of the electro-optic modulator, and a processor that controls a bias voltage of the electro-optic modulator using a monitoring result of the monitor circuit, wherein the processor superimposes a first dither signal with a first frequency and a second dither signal with a second frequency different from the first frequency, onto one bias voltage in a time sharing manner, calculates a first control error based on a first component oscillating at the first frequency and a second control error based on a second component oscillating at the second frequency based on the monitoring result, and determines a control value for controlling the bias voltage using the first control error and the second control error.

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.

Described herein is a solution to address the intrinsic nonlinearity of analog signals and the restrictions this places on the signals dynamic range. The subject matter described herein produces linear electro-optic modulation over a dramatically wider range of the input signal amplitude. This is accomplished by a distributed multiwavelength design that folds the large dynamic range across multiple linear subranges, with each subrange being addressed using an optical wavelength. As a result, the subrange within the wide dynamic range of the input signal is captured by the linear portion of the transfer function of a single transfer function. Several physical implementations of this subject are presented herein. This innovation enables the efficient use of optical links for the transmission and processing of analog and multilevel signals, overcoming the limitations that were once hindering progress in this field.

A device for generating wide capture range frequency tunable optical millimeter-wave signal includes a millimeter-wave signal generating structure, a millimeter-wave signal modulation structure, an optical delay phase detection structure and a feedback control loop. The millimeter-wave signal generating structure obtains millimeter-wave signal by beat frequency of the optical signal generated by a master laser and a slave laser, the millimeter-wave signal is modulated onto an optical carrier of the master laser by the electro-optical modulation structure, and then passes through the optical delay phase detection structure to generate an error signal associated with a frequency of the millimeter-wave signal. The error signal is controlled by the feedback control loop to change temperature and driving current of the slave laser, and adjust a difference between output wavelengths of the master laser and the slave laser, and at last maintain the frequency and phase of the millimeter-wave be stable.