A packaged integrated white light source configured for illumination and communication or sensing comprises one or more laser diode devices. An output facet configured on the laser diode device outputs a laser beam of first electromagnetic radiation with a first peak wavelength. The first wavelength from the laser diode provides at least a first carrier channel for a data or sensing signal.

An optical transmitter includes a bias supplying unit configured to supply a first bias voltage, a second bias voltage and a third bias voltage to an optical modulator. The bias supplying unit acquires a first voltage value at which an average value of an optical output signal becomes maximum by sweeping the first bias voltage, acquires a second voltage value at which an average value of the optical output signal becomes maximum by sweeping the second bias voltage, and acquires a third voltage value at which an average value of the optical output signal becomes maximum by sweeping the third bias voltage. The bias supplying unit determines a value of the first bias voltage based on the first voltage value, determines a value of the second bias voltage based on the second voltage value, and determines a value of the third bias voltage based on the third voltage value.

A system to control convergence of a loop to a reference value. A device, under control of the control loop, generates an output signal. A comparator compares the output signal to a reference value. Responsive to the output signal being less than the reference value, outputting an up signal and, responsive to the output signal being greater than the reference value, outputting a down signal. A counter is configured to maintain a counter value which is incremented in response to an up signal and decremented in response to a down signal. The counter outputs a gain control value. An up/down signal tracker is configured to track a pattern of up signals and down signals and compare the tracked pattern to one or more predetermined patterns such that, responsive to the up signals and down signals matching one of the one or more predetermined patterns, the counter size is decreased.

Apparatus and method for digital signal constellation transformation are provided herein. In certain configurations, an integrated circuit includes an analog front-end that converts an analog signal vector representing an optical signal into a digital signal vector, and a digital signal processing circuit that processes the digital signal vector to recover data from the optical signal. The digital signal processing circuit generates signal data representing a signal constellation of the digital signal vector. The digital signal processing circuit includes an adaptive gain equalizer that compensates the signal data for distortion of the signal constellation arising from biasing errors of optical modulators used to transmit the optical signal.

In order to suppress any reduction in the reception performance of an optical transceiver, the optical transceiver includes a light source, an optical splitter that splits the output of the light source into a first split light and a second split light, an optical modulation unit that modulates the first split light, a coherent receiver that causes the inputted received light to interfere with the second split light, and a first control unit that controls the split ratio of the optical splitter on the basis of the reception characteristic of the received light received by the coherent receiver.

Methods and apparatus for coherent transmitter calibration are provided that employ direct detection (DD) using one single photodetector (PD). The provided method and apparatus do not require hardware for coherent reception, or additional ADCs for quality control. An additional optical tone is added to a QAM optical signal that is outside the band of the QAM optical signal. The result of this is that after direct detection, there is a correlation between the real and imaginary parts, and the imaginary part can be recovered with a Hilbert transform. The estimated QAM optical signal obtained by direct detection is used to perform a transmitter factory calibration method to calibrate for one or more transmitter impairments and/or to perform in-line self-calibration.

An apparatus includes a laser, an optical power combiner, and an electronic controller. The laser has a plurality of modulatable optical reflectors and is operable to emit mutually coherent optical beams from the modulatable optical reflectors. The optical power combiner has a first optical inputs connected to receive light of one of the optical beams emitted from a first of the modulatable optical reflectors and has a second optical input connected to receive light of one of the optical beams emitted from a second of the modulatable optical reflectors. The electronic controller is connected to operate the first and second of the modulatable optical reflectors to modulate the optical beams emitted therefrom to carry respective first and second data streams. The optical power combiner is connected to interfere the light received from the first and second of the modulatable optical reflectors with a relative phase difference.

In some embodiments, an apparatus includes an optical transmitter module that can be electrically coupled to an electrical serializer/deserializer and a controller. The optical transmitter module can include an electrical detector that can receive an in-band signal. The electrical detector can send to the controller a first power error signal and a second power error signal based on the in-band signal. The controller can send a correction control signal to the electrical serializer/deserializer based on the first power error signal and the second power error signal such that the electrical serializer/deserializer sends a pre-emphasized signal to the optical transmitter module based on the correction control signal. In such embodiments, the first power error signal, the second power signal and the correction control signal are out-of-band signals.

The present invention is directed to communication systems and methods. In a specific embodiment, the present invention provides an optical receiver that receives a data stream from an optical transmitter. The optical receiver determines a histogram contour parameter using the data stream and inserts the histogram contour parameter into a back-channel data segment, which is then transmitted to the optical transmitter. The optical transmitter changes its data transmission setting based on the histogram contour parameter. There are other embodiments as well.

A method or apparatus for narrowing the linewidth of a single mode laser is provided. The linewidth of a single mode laser is narrowed by injecting an optical feedback simultaneously into the first laser cavity mirror and the second laser cavity mirror of the single mode laser.