A control device that may be implemented in a single IC chip is provided that is capable of controlling EAM bias voltages and DFB bias currents and of monitoring the EAM photocurrents and received signal strength indicators (RSSIs) in a multi-channel optical transceiver module. The control device IC chip can be manufactured at relatively low cost with relatively high yield, and can be implemented in a relatively small area. To implement the control device in a single IC chip, multiple supply voltage domains are used in the IC chip, one of which is a negative supply voltage domain and one of which is a positive supply voltage domain. In order to provide these different supply voltage domains, a level shift circuit is employed in the IC chip that converts signals from the positive to the negative supply voltage domain, and vice versa, and changes the voltage levels, as needed.

In order to provide an optical modulator capable of controlling a bias voltage to correspond to transmission characteristics of a modulation means even when a multi-level modulation scheme is applied, an optical modulator 10 is provided with: an amplitude information control means 20 that generates amplitude information for controlling the amplitude of an information signal to correspond to transmission characteristics of a modulation means 50, adds a dither signal to the amplitude information, and outputs the amplitude information; a bias value control means 30 that generates and outputs a bias value for controlling the center of the amplitude of the information signal to correspond to the transmission characteristics of the modulation means 50; a data output means 40 that corrects the amplitude of information data on the basis of the amplitude information, and outputs the information data as the information signal; the modulation means 50 that corrects the center of the amplitude of the information signal on the basis of the bias value, modulates continuous wave light by using the information signal, and outputs a modulation signal; and an adjustment means 60 that extracts, from the modulation signal, the dither signal added to the amplitude information, and adjusts the amplitude information and the bias value such that the differential value of the intensity of the dither signal added to the amplitude information becomes zero.

Embodiments of the present disclosure are directed toward techniques and configurations for an apparatus comprising an electro-optical modulation device with a bias control and adjustment. In some embodiments, the apparatus may comprise an electro-optical modulator having first and second arms, to modulate light passing through the first and second arms in response to an input data signal, and output a corresponding optical data signal. The apparatus may further comprise a control module coupled with the electro-optical modulator, to differentially adjust respective phases of first or second light portions passing through the first and second arms, to achieve a bias point for the optical data signal. The bias point may define a desired power output of the apparatus that corresponds to the optical data signal. Other embodiments may be described and/or claimed.

A Dual Parallel (DP)-Inphase/Quadrature (I/Q) Mach-Zehnder Modulator (MZM) bias controller configured to generate a pair of orthogonal dither signals; multiply the pair of dither signals to create a second order orthogonal dither signal; and lock an Inphase (I) I MZM of a DP-I/Q MZM to a value of a corresponding I component of a transmission signal by applying the pair of orthogonal dither signal to a Quadrature (Q) MZM and a Phase (P) MZM of the DP-I/Q MZM; applying an I bias signal to the I MZM of the DP-I/Q MZM; detecting an output of the DP-I/Q MZM; and determining an I error signal in the output of the I MZM of the DP-I/Q MZM based on the product of second order dither signal and the output of the DP-I/Q MZM.

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.

A communication system includes a laser that generates a laser light and a modulator that includes a modulation element configured to modulate the laser light with an input signal based on a bias voltage to produce an output signal. Control circuitry provides the bias voltage to a bias input of the modulation element and is configured to maintain a bias lock on at least two bias points of the modulation element during operation. The control circuitry is programmed to perform a bias lock operation that includes performing an initial voltage sweep on the modulation element and establish initial bias values for the at least two bias points. The circuit also providing a bias waveform to the bias input of the modulation element that varies over time and contains identifiable dither tones, determines harmonic power at the at least two bias points; and varies the bias waveform to determine harmonic power until the harmonic power is minimized to establish a bias lock with locked bias values.

An apparatus includes an optical device to output a data-modulated optical signal, an electrical radio-frequency (RF) driver to drive the optical device with one or more RF drive signals, a photodetector to provide a measure of a light intensity output by the optical device, and an electronic controller. The electronic controller is configured to dither an amplitude of at least one of the one or more RF drive signals at a dithering frequency. The electronic controller is also configured to adjust one or more operation settings of at least one of the electrical RF driver and the optical device based on a component of the measure of a light intensity at the dithering frequency.

A Mach-Zehnder modulator (MZM) includes a first optical path with a first diode coupled to a first voltage signal node and configured to modify a phase of a first light signal transmitted through the first optical path. A further diode is positioned in the first optical path and configured to introduce a phase shift to the first light signal. A second optical path includes a second diode coupled to a second voltage signal node and configured to modify a phase of a second light signal transmitted through the second optical path. A first voltage signal carried on the first voltage signal node and a second voltage signal carried on the second voltage signal node each vary between a reverse biasing voltage level and a forward biasing voltage level. An optical coupler is coupled the first and second optical paths.

Disclosed are bias control methods for Mach-Zehnder modulators for the generation of optical QAM signals while ensuring correct I/Q polarity of the generated optical QAM signal. One exemplary method involves temporarily offsetting I and Q biases from ideal transmission null bias points while another illustrative method temporarily makes I and Q data streams identical.

An optical communications apparatus comprising a host (100) and an optical module (200) comprising a Mach-Zehnder modulator (202), MZM, wherein the optical module is removably connected to the host via a connection path, the optical communications apparatus comprising: a signal generator (101) at the host, configured to generate a plurality of calibration signals at a plurality of frequencies; a host interface (102) configured to transmit the calibration signals to the optical module via the connection path; a module interface (201) configured to receive the transmitted calibration signals; wherein the MZM is configured to use the calibration signals to modulate a laser light source (206) and biased to a point at which average output power is proportional to the output modulated signal; an optical detector configured to measure an average magnitude of an output of the MZM when each of the calibration signals is used to modulate the laser light source; one of a host calibration unit (103) and a module calibration unit (203), configured to determine a magnitude response of the connection path based on the measured average magnitudes and magnitudes of the respective calibration signals, and further configured to determine a pre-emphasis characteristic based on the magnitude response, the pre-emphasis characteristic for application to signals transmitted by the optical transmitter in use.