An apparatus at least includes a processor to, after a first signal passes through a narrowband photodetector, perform frequency mix of the first signal with a first reference signal and a second reference signal respectively and perform noise reduction, to obtain a first detection signal and a second detection signal. The first signal is obtained after a measurement signal passes through a filtering module of an optical transmitting end, the measurement signal being transmitted in a path of multiple branches, signals not transmitted in other paths of the multiple branches, a frame structure of the measurement signal including at least one two-tone signal, two tones in the two-tone signal having a fixed tone interval. The processor is to calculate group delays at multiple frequency bins according to the first detection signal and the second detection signal; and determine a phase response of the filtering module of the optical transmitting end in the path according to the group delays at multiple frequency bins.

Various embodiments of a laser driver are described herein. In an embodiment, a laser driver system includes: an external set of inductors including a first external inductor and a second external inductor; an internal set of inductors including a first internal inductor and a second internal inductor; and a DC-to-DC convertor configured to bias a first output path defined by the first external inductor and the first internal inductor and a second output path defined by the second external inductor and the second internal inductor.

The upper surface of the semiconductor substrate has a slope descending from the projection in the second direction at an angle of 0-12° to a horizontal plane. The mesa stripe structure has an inclined surface with a slope ascending from the upper surface of the semiconductor substrate at an angle of 45-55° to the horizontal plane, the mesa stripe structure having an upright surface rising from the inclined surface at an angle of 85-95° to the horizontal plane. The buried layer is made from semiconductor with ruthenium doped therein and is in contact with the inclined surface and the upright surface. The inclined surface is as high as 80% or less of height from the upper surface of the semiconductor substrate to a lower surface of the quantum well layer and is as high as 0.3 μm or more.

Various embodiments of a laser driver are described herein. In an embodiment, a laser driver system includes: an external set of inductors including a first external inductor and a second external inductor; an internal set of inductors including a first internal inductor and a second internal inductor; and a DC-to-DC convertor configured to bias a first output path defined by the first external inductor and the first internal inductor and a second output path defined by the second external inductor and the second internal inductor.

A photodiode current comparison circuit has a first current source coupled to a circuit node configurable to operate in a first mode, a second current source coupled to the circuit node configurable to operate in a second mode opposite the first mode, and a third current source switchable to route a current to the circuit node in response to a data signal using a transistor coupled between the circuit node and the third current source. A photodiode is coupled to the circuit node. In a first configuration, an anode of the photodiode is coupled to the circuit node and a cathode of the photodiode is coupled to a power supply terminal. In a second configuration, a cathode of the photodiode is coupled to the circuit node and an anode of the photodiode is coupled to a power supply terminal. An amplifier provides an error signal of the photodiode.

A method and apparatus for matching different impedance of optical components and a package for optical communication using a tapered transmission line (or a taper) are provided. The taper may be configured to include a first section, a second section, and a third section, each of which corresponds to different components. By way of example, the first section of the taper may be configured to be allocated to a driver to a flex joint on a printed circuit board (PCB), the second section of the taper may be configured to be allocated to a flex circuit, and the third section of the taper may be configured to be allocated to a transistor outline (TO) and submount including a directly modulated laser (DML). The taper is configured to minimize an amount of impedance mismatch between the optical components and the package.

The present invention relates to a technical field of optical communications. It relates to a dual-rate DML device and module, and a calibration method, and in particular, to a dual-rate DML device and module having a built-in signal calibration circuit, and a calibration method. According to the present invention, the signal calibration circuit is added into the device; a PD is prepositioned by means of a novel light splitting structure; a control structure for a sequence-divided multi-channel serial signal is utilized to feed back a monitoring signal to an electric driver to adjust drive current; crosstalk between backlight monitoring is reduced; and high-quality signal output under dual modulation frequencies of 25 Gbps and 28 Gbps is realized.

An optical device includes a generator, a light emitter, a modulator, an optical amplifier, a current source, a storage, and a controller. The generator generates an electric signal of a multilevel amplitude modulation method. The light emitter emits laser light. The modulator modulates the laser light using the electric signal and outputs an optical signal. The optical amplifier optically amplifies the modulated optical signal according to a drive current. The current source adjusts the drive current to be supplied to the optical amplifier. The storage previously stores an information with respect to input-output characteristics of the optical signal in the optical amplifier relative to drive current value of the drive current. The controller acquires, from the storage, the input-output characteristics corresponding to the drive current value of the drive current supplied to the optical amplifier and controls the electric signal based on the acquired input-output characteristics.

A system for transmitting a sequence of at least two data bursts in a fibre optical communications system includes: selection circuitry configured to select one of a data input value, a logical high value or a logical low value such that the selection circuitry selects the data input value during a data transmission period during a defined burst period and selects one of the logical high value and the logical low value during an extension time period during the defined burst period and immediately following the data transmission period, such that for the sequence of at least two bursts, at least one burst has a logical low value extension period and at least one burst has a logical high value extension period; drive circuitry configured to apply a current to a laser diode, the current corresponding to the value selected by the selection circuitry during the defined burst period or a zero value otherwise, the current being such that the laser diode is configured to provide an optical output; an optical sensor module configured to provide a sensor module output corresponding to the optical output of the laser diode; wherein the sensor module output is configured to provide an electrical output proportional to the laser diode's optical output corresponding to the logical high value and the logical low value in the sequence of at least two bursts, and further configured to provide an output corresponding to an average value of the sensor module output during only the data transmission period during the sequence of bursts; and a controller configured to receive values regarding desired minimum and maximum optical output power levels of the laser diode and to receive the electrical output from the optical sensor module proportional to the optical output power level corresponding to the logical high and the logical low values, and to receive the output corresponding to the average value of the sensor module output during only the data transmission period during the sequence of bursts; wherein the controller is configured to use the received information to provide control values for the drive circuitry.

A photodiode current comparison circuit has a first current source coupled to a circuit node configurable to operate in a first mode, a second current source coupled to the circuit node configurable to operate in a second mode opposite the first mode, and a third current source switchable to route a current to the circuit node in response to a data signal using a transistor coupled between the circuit node and the third current source. A photodiode is coupled to the circuit node. In a first configuration, an anode of the photodiode is coupled to the circuit node and a cathode of the photodiode is coupled to a power supply terminal. In a second configuration, a cathode of the photodiode is coupled to the circuit node and an anode of the photodiode is coupled to a power supply terminal. An amplifier provides an error signal of the photodiode.